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Abstract

The developing world faces dual crises of escalating energy demand and lack of urban sanitation infrastructure that pose significant burdens on the environment. This paper presents results of a study evaluating the feasibility of using human feces-derived char as a solid fuel for heating and cooking, and a potential way to address both crises. The study determined the energy content and the elemental composition of chars pyrolyzed at 300, 450, and 750°C. Fecal chars made at 300°C were found to be similar in energy content to wood chars and bituminous coal, having a heating value of 25.6 ± 0.08 MJ/kg, while fecal chars made at 750°C had an energy content of 13.8 ± 0.48 MJ/kg. The higher heating values of the studied chars were evaluated using their elemental composition and a published predictive model; results found good agreement between the measured and predicted values. Fecal chars made at low temperatures were briquetted with molasses/lime and starch binders. Briquettes made with 10% starch had an average impact resistance index of 79 and a higher heating value of 25 MJ/kg. These values are comparable to those of commercial charcoal briquettes, making fecal char briquettes a potential substitute that also contributes to the preservation of the environment.

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... Fig. 1 outlines a concept for integrating this technology into the management of FS. Experimental studies have examined the characteristics of FS-derived biochars as a soil amendment (Woldetsadik et al., 2018), solid fuel (Ward et al., 2014) and adsorbent (Koetlisi and Muchaonyerwa, 2017) or have assessed different uses simultaneously (Gold et al., 2018;Liu et al., 2014). FS pyrolysis has also been the subject of thermodynamic modelling (Yacob et al., 2018). ...
... FS pyrolysis offers complete destruction of pathogens due to high processing temperatures (Ward et al., 2014). This is a key advantage for the agricultural use of FS-derived biochars, adding to the value from any plant nutrients retained in the biochar. ...
... The results from thermal analysis for PF, W-FS and N-FS are shown in Fig. 3. Any weight losses below 180 + C seen for FS and PF are caused by drying and dehydration reactions (Magdziarz and Werle, 2014). PF shows the typical weight loss between 150 and 500 + C caused by the decomposition of hemicellulose, cellulose and lignin (Basu, 2010) while the weight loss for FS is also associated with the decomposition of carbohydrates, protein and fats (Ward et al., 2014;Liu et al., 2014). Both PF and FS reach maximum weight loss rates between 340 and 350 + C. The cessation of weight loss from approximately 500 + C onwards for FS and 400 + C for PF indicates that the main pyrolysis reactions are complete. ...
Article
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Unsafe disposal of faecal sludge from onsite sanitation in low-income countries has detrimental effects on public health and the environment. The production of biochar from faecal sludge offers complete destruction of pathogens and a value-added treatment product. To date, research has been limited to the laboratory. This study evaluates the biochars produced from the co-treatment of faecal sludge from septic tanks and agricultural waste at two full-scale treatment plants in India by determining their physical and chemical properties to establish their potential applications. The process yielded macroporous, powdery biochars that can be utilised for soil amendment or energy recovery. Average calorific values reaching 14.9 MJ/kg suggest use as solid fuel, but are limited by a high ash content. Phosphorus and potassium are enriched in the biochar but their concentrations are restricted by the nutrient-depleted nature of septic tank faecal sludge. High concentrations of calcium and magnesium led to a liming potential of up to 20.1% calcium carbonate equivalents, indicating suitability for use on acidic soils. Heavy metals present in faecal sludge were concentrated in the biochar and compliance for soil application will depend on local regulations. Nevertheless, heavy metal mobility was considerably reduced, especially for Cu and Zn, by 51.2-65.2% and 48.6-59.6% respectively. Co-treatment of faecal sludge with other carbon-rich waste streams can be used to influence desired biochar properties. In this case, the addition of agricultural waste increased nutrient and fixed carbon concentrations, as well as providing an additional source of energy. This study is a proof of concept for biochar production achieving full-scale faecal sludge treatment. The findings will help inform appropriate use of the treatment products as this technology becomes more commonly applied.
... The soluble sugars contained in molasses can recrystallize after the drying processes and form solid bridges to capture more particles, which results in high mechanical strength of the pellets (Mišljenović et al., 2016). Studies have shown that hardeners, such as phosphoric acid, nitrate, and lime, further increase the pellets strength (Benk and Coban, 2011;Blesa et al., 2003a;Ward et al., 2014). However, lime can improve the green strength of pellets, is relatively inexpensive, and can enhance molasses agglomeration (D. ...
... However, lime can improve the green strength of pellets, is relatively inexpensive, and can enhance molasses agglomeration (D. Taulbee, 2009;Ward et al., 2014). Lime addition is also attractive for application in slagging boilers with the aim of lowering the ash-fusion temperature (D. ...
... In this study, molasses and a combination of cane molasses and lime (CaO) were selected as additional binders for pelletization. It is known that increasing the quantity (generally 10-20%, w/w) of molasses can increase the mechanical properties of pellets (Blesa et al., 2003a;Mišljenović et al., 2016;Ward et al., 2014). Preliminary experiments (Fig. 1) showed a similar result for hydrochar with 20% (w/w) molasses addition reaching a maximum compressive force and low compressive distance. ...
Article
Hydrochar was produced from food waste under varying hydrothermal carbonization (HTC) conditions, and was pelletized using molasses and molasses/lime binders for fuel pellet production. The physico-chemical properties, density, mechanical properties, and water resistance, and combustion characteristics of the hydrochar pellets were investigated. The results indicated that molasses pellets and molasses/lime pellets exhibited increased compressive strength, density, and impact resistance due tothe "solid bridge" that formed from molasses recrystallization and agglomeration by lime. The hydrochar samples prepared at 230 °C and 260 °C, with long residence times of 8 h, showed excellent compressive strength and impact resistance index (IRI). Both molasses pellets and molasses/lime pellets exhibited slightly increased equilibrium moisture content (EMC), with the former showing a high water-resistance index (WRI) in the immersion test. Thermogravimetric analyses indicated that the molasses pellets had a lower ignition temperature and higher combustion interval than those of the molasses/lime pellets.
... However, there is a lack of research on the use of excreta from dry toilets as pyrolysis substrate. Previous studies have included human faeces [14], and faecal sludge from pit latrines [15] and septic tanks [16], which have different characteristics from dry toilets with excreta and wood chips [7]. This also concerns the environmental safety and the effect of soil biochar addition on the growth of plants and consumption of resulting produce by animals and humans. ...
... Higher temperatures and higher heating rates usually cause more compounds to volatilize, leading to a lower yield [39]. The yield in this study was comparable to biochar yields with human feces produced at 450 °C and 750 °C (29 and 30% DM [14]). Biochar production from fecal sludge at 500 °C, 600 °C and 700 °C also had comparable yields of 35, 31 and 31% DM [16]. ...
... In comparison, biochars from woody feedstocks have typically lower concentrations of macronutrients (i.e., N, P, and K), their positive effect on soil fertility is attributed rather to effects like increasing cation exchange capacity, nutrient retention, water holding capacity, and elevation of soil pH [55]. This N concentration in the DTS-biochar was lower than reported for biochar derived from human feces (48 g N/kg DM [14]), but was comparable to fecal sludge derived biochars (24-29 g N/kg DM [16]) and wastewater sludge biochars (9-19 g N/kg DM [56]). These reported biochars were all produced at similar pyrolysis temperatures (450-700 °C) to the one used in this study. ...
Article
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Biochar is increasingly being applied as a soil amendment in agriculture. Biochar is typically produced from plant biomass and contains relatively low amounts of plant nutrients (e.g., N, P, and K), thus providing limited fertilizer value. Human excreta contains plant nutrients that could be recycled to create sustainable agricultural nutrient cycles. This study investigated the potential of biochar derived from a dry toilet substrate as soil amendment. The substrate consisted of urine, faeces, and wood chips, and was pyrolyzed at 500–650 °C for 10 min. The biochar was analyzed for plant available P, water leachable P and K, carbon stability, pH, electrical conductivity, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), dioxins, and germination tests with barley and lettuce were conducted to estimate the biochar fertilizer value and potential bio-toxicity. The biochar contained 25.0 ± 1.0 g N/kg dry mass (DM), 33.1 ± 2.1 g P/kg DM and 20.7 ± 0.2 g K/kg DM. 65% DM P was extractable by formic acid solution, 31.7% DM P and 60.5% DM K were water leachable in a ten-day column water-leaching experiment. The biochar complied with European regulations for PAHs, PCBs, dioxins and heavy metal concentrations, except for Zn and Ni. Germination of salt-resistant barley was not affected by biochar doses < 50% DM, while salt-sensitive lettuce germination was inhibited at doses ≥ 2% DM, indicating that the dry toilet substrate biochar induced salt stress. Based on these results, it is recommended that urine separation should be considered for biochar of excreta, which could reduce salt stress while maintaining concentrations of “fixed” or bioavailable nitrogen. Graphic Abstract
... At lower temperatures (300-700°C), low heating rates (1-10°C min −1 ) and long residence times (∼hours), a regime known as 'slow pyrolysis', most of the carbon content of faecal sludge can be converted to a useful and pathogen-free char, together with a high-energy gas and oil. 8 Among the products of pyrolysis, char is a carbon-enriched substance that is of interest due to its biochemical stability and porous structure with high specific surface area. These characteristics, beyond making biochar suitable as a fuel, has been shown to have the capability to increase water and nutrient retention of soil and to adsorb aquatic pollutants during water purification. ...
... biochar). 4,[20][21][22] While there has also been limited recent interest in the pyrolysis of untreated faeces 8,23,24 and in the combustion of faecal sludge in developing countries, 25,26 the authors are unaware of any peer-reviewed literature which has specifically examined the pyrolysis of pit latrine sludge, other than an earlier version of this study, which was retracted due to scientific errors in the energy balance calculations. 27 This is despite the many benefits potentially associated with generating a biochemically-stable product which can be used as a soil enhancer to improve the structure of soil and increase agricultural output (Table 1). ...
... Moreover, thermal conversion of char removes pathogens from faecal sludge and reduces the waste volume and transport costs associated with pit latrine sludge disposal. 8 In a developing country context, where up to 90% of people lack reliable energy supplies, 8,28 generating a sustainable biofuel is another strong motivation for investigating this strategy (Table 1). ...
Article
Sustainable methods are required in developing regions to treat and recover value from pit latrine sludge. One strategy is to pyrolyse pit latrine contents and generate char and bio-oil, which can then be used as a soil enhancer and fuel, respectively. Despite the many benefits associated with the process, there is very limited relevant literature available. This study examines its feasibility. Initially, the energy balance for the pyrolysis of sewage sludge was calculated using data from 14 literature studies. The average net energy recovery from pyrolysis of dewatered and dried sewage sludge followed by use of bio-oil as fuel was calculated as 4.95 ± 0.61 MJ kg⁻¹. For dewatered sewage sludge, an average net energy input of 2.23 ± 0.31 MJ kg⁻¹ was required. Parallel calculations were undertaken where pit latrine sludge with 0–100% water content was the hypothetical feedstock. On average, net energy recovery from produced bio-oil was achievable when pit latrine sludge with a water content of ≤∼55% was the feedstock. When both bio-oil and char were utilised, net energy recovery was feasible at a water content value of ≤∼65%. Char production is more favourable from stabilised pit latrine sludge with lower moisture and volatile solids content. Barriers to the pyrolysis of pit latrine sludge include its heterogeneous composition and the difficulty of collecting high-viscosity sludge. Overall, this study demonstrates the potential of pyrolysis as a disposal and value addition method for pit latrine sludge. Innovative methods for sludge drying and pit emptying will expedite the process becoming a reality.
... A few studies that have investigated the thermochemical conversion of human faeces have focused on the development of energy conversion systems and operating conditions (Onabanjo et al., 2016a;Ward et al., 2014;Jurado et al., 2018;Gold et al., 2018) with limited understanding of fuel conversion processes and interaction. From studies completed, there is the understanding that temperature and residence time are factors affecting the yield and quality of products (Ward et al., 2014;Liu et al., 2014;Gold et al., 2018). ...
... A few studies that have investigated the thermochemical conversion of human faeces have focused on the development of energy conversion systems and operating conditions (Onabanjo et al., 2016a;Ward et al., 2014;Jurado et al., 2018;Gold et al., 2018) with limited understanding of fuel conversion processes and interaction. From studies completed, there is the understanding that temperature and residence time are factors affecting the yield and quality of products (Ward et al., 2014;Liu et al., 2014;Gold et al., 2018). Operating temperature of 300 • C is suggested to be suitable for fuel production but those above 600 • C were not recommended for faecal char. ...
... Studies by Liu et al. (2014), Ward et al. (2014) and Gold et al. (2018) have showed that pyrolysis temperature of 300 • C can affect the quality of faecal char as fuel, due to progressive loss of energy-rich hydrocarbons and an increasing amount of ash. Unlike coal fuels, where low pyrolysis temperature improves HHVs via decarboxylation, aromatization, condensation and polymerization, low heat can cause thermal degradation of biomass feedstocks. ...
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Human faeces (HF) are treated as wastes in many parts of the world, a resource that can be converted to energy and fuels. To enhance the understanding of fuel conversion processes and decomposition characteristics, this study investigated the pyrolysis behaviour and evolved gas profiles of HF using thermogravimetry with gas chromatography–mass spectrometry methods. Kinetic parameters were deduced using model-free kinetic models. Results are compared with simulant faeces (SF), wood biomass (WB) and HF–WB blends. The pyrolysis of HF involved two decomposition peaks — a fronting peak with weight loss of ∼51 wt% and a tailing shoulder peak with weight loss of ∼15 wt%. The apparent activation energy for HF varied from 122–382 kJ/mol at conversion rates of 10%–90% using Kissinger–Akahira–Sunose model. Some of the key pyrolysis products for HF at 370 °C were 4-methoxy-phenol, n-hexadecanoic acid, phenol, 4-methyl- and indole isomer (pyrrolo[1,2-a]pyridine). At 530 °C, evolved gases were largely fragmented with high proportions of alkanes and alkenes including 3-dodecane, 2-undecane, 6-tridecene, 2-propenylidene-cyclobutene. These products differed to WB that are largely hydroxyphenyls and methoxyphenols with guaiacyl or syringil structures. Blending with WB improved pyrolysis of HF, irrespective of the proportions of blend.
... Chemical properties including chemical and biological oxygen demand, nutrient concentration, pH and conductivity are of importance for simulating biological disintegration, treatment of faeces and biogas production (e.g., Kaba et al., 1989;Wignarajah et al., 2006;Miller et al., 2015). Heating properties and elemental composition (C,H,N,O) are of importance for analysing energy recovery and for using the faeces for soil amendment e.g., biochar or compost production (e.g., Ward et al., 2014;Col on et al., 2015;Onabanjo et al., 2016a). Studies on the fate of faeces in sewers and in onsite sanitation systems include their movement, settling and physical disintegration together with biochemical disintegration. ...
... Simulant #7 (see Table 3) is the basis of the synthetic faeces used by a number of research groups focusing on the energy recovery from faeces and its treatment in onsite sanitation systems. Ward et al. (2014) and Danso-Boateng et al. (2012) used it to simulate the energy content of carbonized faeces. Danso-Boateng et al. (2012) modified this simulant for investigating converting biomass within faeces into char using hydrothermal carbonisation (HTC). ...
... No information on the purpose of their modification or the simulant's resemblance to faeces was reported. Ward et al. (2014) evaluated solid fuel char briquettes produced from faeces. They found that although both the faeces and the simulant (simulant #7 as in Table 3) had similar calorific values, the char produced from synthetic faeces had a higher calorific value compared to char produced from real faeces. ...
Article
Investigations involving human faeces and faecal sludge are of great importance for urban sanitation, such as operation and maintenance of sewer systems, or implementation of faecal sludge management. However, working with real faecal matter is difficult as it not only involves working with a pathogenic, malodorous material but also individual faeces and faecal sludge samples are highly variable, making it difficult to execute repeatable experiments. Synthetic faeces and faecal sludge can provide consistently reproducible substrate and alleviate these challenges. A critical literature review of simulants developed for various wastewater and faecal sludge related research is provided. Most individual studies sought to develop a simulant representative of specific physical, chemical, or thermal properties depending on their research objectives. Based on the review, a suitable simulant can be chosen and used or further developed according to the research needs. As an example, the authors present such a modification for the development of a simulant that can be used for investigating the motion (movement, settling and sedimentation) of faeces and their physical and biological disintegration in sewers and in on-site sanitation systems.
... The efficient utilization of energy will be an urgent problem in the next several decades, and many people in developing countries lack an adequate supply of energy resources [1]. Therefore, it is imperative to find out alternative and clean fuels. ...
... In addition, molasses based carbonized seaweed pellets have improved durability [34]. Molasses was also used in human feces char, with calorific values of 12.92 ± 0.11 MJ/kg [1]. ...
Article
In this study, the effect of four organic binders (protein, starch, lignin, and molasses) on woody biomass pellets was investigated. Properties of binder based pellets were evaluated for energy consumption, tensile strength, equilibrium moisture content, and combustion performance. Results indicate that the energy consumption of all binder based pellets was less than that of hydrochar pellets (45.38 J/g). In addition, starch and protein pellets exhibited better mechanical strength when binder content is 20% (3.07 and 3.40 MPa, respectively). Scanning electron microscope results indicate that starch and protein combined closely with hydrochar. Pellets with starch as the binder (20%) exhibited the highest equilibrium moisture content. Regarding combustion performance, low ignition temperature (Ti) was observed for all binder based pellets.
... Therefore, in this study molasses was used as a binder which was recommended by Zhai et al. (2018). Previous literature suggests that generally 10-20% w/w of molasses is helpful in improving the mechanical strength of pellets (MišljenovicétMišljenovicét al., 2016;Ward et al., 2014). For instance, MišljenovicétMišljenovicét al. (2016) used wheat straw and straw bales and mixed them in sugar beet molasses at two different proportions (1.5% and 3%). ...
... Molasses also played a vital role in producing pellet with high bulk density with low moisture content. Ward et al. (2014) treated human waste under pyrolysis process at 300, 450 and 750 °C for 2 h. Starch, molasses and lime were used in different binding ratio to prepare briquettes. ...
Article
A blended feedstock containing food waste and coal was used to perform co-hydrothermal carbonization (Co-HTC) at different temperatures to observe the effect of temperature on the solid fuel properties of different hydrochars. Moreover, these hydrochars were mixed with molasses which act as a binder to prepare high mechanical strength pellets. A range of techniques was used to characterise the hydrochars and pellets. Food waste and coal hydrochars produced at 300 °C exhibited high heating value (HHV) of 31.1 and 31.4 MJ/kg respectively, however, high heating value of the Co-HTC 300 °C hydrochar decreased to 28.6 MJ/kg. The ash content of hydrochar obtained via the Co-HTC at 300 °C, was 53% less than the ash content of raw coal. Combustion results showed that the Co-HTC of food waste and coal is thermally more suitable than HTC of food waste and coal. During pelletization molasses played an important role in making solid bridge between the hydrochars. The tensile strength of all the hydrochars ranged between 2 and 4.5 MPa. The blend treated at 300 °C showed the highest tensile strength of 4.5 MPa. The mass density of food waste and blend increased as the temperature was increased, however, the mass density of the coal sample showed a decreasing trend. The energy densities of all the hydrochars ranged between 22.2 and 39 GJ/m ³ and the energy density of the blends were higher than the coal and food waste hydrochar.
... Sugarcane bagasse 28.32 [22] Orange bagasse 26.47 [19] Human waste 25.1 [27] Groundnut shells 22.50 [28] Waste plastic and coal 19.27 [15] Rice husk 17.04 [29] Rice straw and rice husk ash 17.01 [29] Paper and saw dust 16.68 [30] Waste oil 14.65 [31] Leather cassava tubers and sludge 7.68 [16] Used COVID-19 polypropylene isolation gown waste -Current work ...
... This is due to the absence of exothermic or endothermic peaks. These results are supported by previous works [15,21,27]. ...
Article
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Slow pyrolysis using a batch reactor at 450 °C was applied to the polypropylene (PP) powder derived from Coronavirus Disease 2019 (COVID-19) isolation gown waste to yield char briquettes, using sugar palm starch (SPS) and a manual hydraulic press. These studies are significant because of reductions in plastic waste from the preparation of barbecue coal due to environmental sustainability. The results presented here include the physical, morphological, thermal, combustion, and mechanical properties of char when reinforced with various percentages of SPS loadings (0, 10, 20, 30, and 40%), which act as a matrix/binder to produce char/sugar palm starch (C/SPS) composites. The physical and morphological characteristics of C/SPS composites were determined using Fourier transform infrared (FTIR) and field emission scanning electron microscopy (FESEM). On the other hand, the thermal and combustion properties of the C/SPS briquettes were studied via thermogravimetric and bomb calorimeter analysis. The results show that the compressive strength of the briquettes increased as the SPS loading increased, whereas the higher heating values (HHV) reduced. The findings indicate that C-80/SPS-20 briquettes presented excellent combustion characteristics (1,761,430 J/g) with satisfactory mechanical strength (1.463 MPa) in the compression test. Thus, C-80/SPS-20 briquettes are the most suitable composites for domestic and commercial uses.
... Pyrolysis is the thermal degradation of organic materials to a carbon-enriched product namely char. It is well known that biomass pyrolysis also yields non-condensable gases of which some give off energy when combusted, as well as energy-rich solid and liquid products (tars and oils) that can be used directly as fuels (Kaminsky and Kummer, 1989;Ward et al., 2014) or chemically converted to higher-grade fuels. Some of the liquid products are released as pyrolysis gases but condense at room temperature and pressure to be liquids, while non-condensable gases remain gases. ...
... Liu et al. have performed pyrolysis experiments on partially decomposed septic tank waste (Liu et al., 2014) and showed the energy benefits of pyrolyzing the waste. Researchers have also demonstrated the production of fuel briquettes from the pyrolysis of untreated fecal sludge (Ward et al., 2014). ...
Article
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Pyrolysis of human feces renders the waste free of pathogens and is a potential method of treating fecal sludge waste collected from non-sewered systems. Slow pyrolysis experiments were conducted on human feces and the char yield and gas evolution quantified at 1–10 °C/min heating rates. Char yield ranged from 35.1 to 35.8% (dry mass basis), while the gas yield ranged from 17.2 to 29.6% (dry mass basis). The pyrolysis gases detected were CO, CO2, CH4, C2H6, and H2. These non-condensable gases contained a higher heating value (HHV) ranging from 7.2 to 22.8 MJ/Nm3. Kinetic analysis was done by a pyrolysis reaction model free method (Isoconversional) as well as a DAEM (Distributed Activated Energy Model) method that assumes many irreversible first order reactions. Both yielded very close values for activation energy ranging from 141 kJ/mol to 409 kJ/mol, with half of the biomass conversion happening at 241.5 ± 2.9 kJ/mol. The findings of the research provide useful technical information that can guide the design of a pyrolysis system to treat fecal waste. Social acceptance and scale-up issues need to be addressed through further research.
... Coal can be blended with a small quantity of this agricultural waste (agro residues) to produce briquettes (bio-coal briquettes) which ignites fast, burn efficiently, producing little or no smoke and cheaper than coal briquettes (Ward et al., 2014) [17] . Thus, the studies is aimed at formulating eco-friendly biocoal briquette from agro-waste and study how the binders affects the calorific values of the briquette through water boiling test. ...
... Coal can be blended with a small quantity of this agricultural waste (agro residues) to produce briquettes (bio-coal briquettes) which ignites fast, burn efficiently, producing little or no smoke and cheaper than coal briquettes (Ward et al., 2014) [17] . Thus, the studies is aimed at formulating eco-friendly biocoal briquette from agro-waste and study how the binders affects the calorific values of the briquette through water boiling test. ...
Article
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The potential use of biomass as energy source in Nigeria is very high and this can be explained from the fact that about 80 % of Nigerians are rural or semi-urban dwellers that depend solely on biomass for their energy source. This research investigates the formulation of bio-coal briquette from groundnut shell, maize cob and rice husk and also studies how incorporation of binder affects the calorific values of the formulated briquettes. Some briquettes were formulated from the agro-waste with the incorporation of equal amounts of starch and coal (samples B, E and H) while in other briquettes, only starch was incorporated (samples A, D and G). Briquette samples C, F and I were formulated without any binder. The result also showed that the briquette samples (with or without binder) has higher burning rate and heating values than firewood. The results showed that all the briquette samples incorporated with starch or starch and coal binders boiled water at 16 min while firewood and briquette samples without binder boiled at 20 min except for maize cob briquette that could not boil water at 20 min. Incorporation of binders was found to increase the calorific values the briquette significantly. It was observed that incorporation of coal as binder had a significant effect only on the calorific value groundnut shell briquette samples. The result showed that briquettes will serve as a more effective substitute for firewood as it shows more combustion characteristics over firewood and the raw materials (agro-waste) are readily available. Introduction Biomass, particularly agriculture residues seem to be the most promising energy resources for developing countries (Patomsok, 2008) [13]. Rural households and minority of urban dwellers depend solely on fuel woods (charcoal, firewood and sawdust) as their primary source of energy for the past decades (Onuegbu et al., 2010) [8]. Of all the available energy resources in Nigeria, coal and coal derivatives such as smokeless coal briquettes, bio-coal briquettes and biomass briquettes have been shown to have the highest potential for the use as suitable alternative to coal/fuel wood in industrial boiler and brick kiln for thermal application and domestic purposes. Global warming has become an international concern. Global warming is caused by greenhouse gasses which carbon dioxide is among the major contributors. It was shown that increase emissions of CO 2 have been drastically reduced owing to the fact that the rate of deforestation is higher than a forestation effort in the country (Yahaya and Ibrahim, 2012) [18]. In counties like Japan, China, India etc., it was observed that agricultural wastes (agro residues) can be briquetted and used as substitute for wood fuel. Every year, millions of tons of agricultural waste are generated (Wang et al., 2017) [16]. These are either not used or burnt inefficiently in their loose form causing air to the environment. The major residues are rice husk, corn cob, coconut shell, jute stick, groundnut shell, cotton stalk, etc. these wastes provide energy by converting into high density fuel briquettes. These briquettes are very cheap, even cheaper than coal briquettes. Adoption of briquettes technology will not only create a safe and hygienic way of disposing the waste, but turn into a cash rich venture by converting waste into energy and also contributing towards a better environment (Zubairu and Gana, 2014) [19] .
... Though at this HHT, the yield and energy content of the char reduce to half [67]. Ward et al. (2014) observed the faecal chars made at 750 • C having 13.8 ± 0.48 MJ/kg, which was much lower than those made at 350 • C with 25.6 ± 0.08 MJ/kg [70]. ...
... Though at this HHT, the yield and energy content of the char reduce to half [67]. Ward et al. (2014) observed the faecal chars made at 750 • C having 13.8 ± 0.48 MJ/kg, which was much lower than those made at 350 • C with 25.6 ± 0.08 MJ/kg [70]. ...
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The utilisation of micro-scale thermal treatment technologies for non-sewered applications has been emerging as a prominent route for the safe treatment and disposal of high water content hazardous feedstock. This study provides a comprehensive review of the technological concepts practiced up to date in commercial/pilot and small scales for various types of solid fuels. The respective challenges are critically described and discussed to aid in the selection of promising technology for on-site sanitary applications. Furthermore, the challenges observed with the nominated (pyrolysis) technology are discussed in detail and addressed. This study suggests rapid energy recovery from by-products primarily made up of the highest yield of syngas with a desirable calorific value. The optimum operating ranges are discussed to ensure a reliable thermal conversion of sludge materials considering the application constraints and technology drawbacks. However, further studies are needed to investigate the uncertainties regarding emissions, energy consumption and overall associated costs.
... In addition, faecal sludge could be co-incinerated with coal in power plants or for industrial applications as cement kilns, similarly to sewage sludge [19,20]. As an alternative to combustion, faecal sludge can be turned into biochar by pyrolysis [21,22] or hydrothermal carbonization [23,24]. Biochar is a high value product that can be employed in several applications, such as fuel for heat or power generation, cooking fuel, soil-conditioner in agriculture and adsorbent in the pollution treatment industry. ...
Article
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This work explores the effect of drying on the chemical and physical properties of faecal sludge, and evaluates the reuse potential of the dried material. For the purpose of this study, the nutrient content, calorific value and thermal properties were determined for faecal sludge samples dried at different moisture contents and under different drying and operating conditions. The results show that drying does not affect the nutrient content and calorific value, but it induces modifications of the chemical form of nitrogen and the thermal properties. The dried product was demonstrated to be suitable for reuse as an agricultural product and biofuel. In agriculture, dried faecal sludge could be used as an organic fertilizer with a particularly high phosphorous content and a slow release of nitrogen and phosphorous. As a biofuel, dried faecal sludge would have similar characteristics as wood.
... Onabanjo et al. [5] and Muspratt et al. [12] showed that human faeces have a comparable and, in some instances, higher heat value than wood biomass (both on a dry basis). This chemical energy can be recovered via thermochemical conversion technologies including smouldering [13,14], combustion [5,15], hydrothermal carbonization [10,16], and pyrolysis [17]. Combustion presents a huge opportunity for energy recovery in the NMT because of the heat released during the process at temperatures ranging from as low as 250°C (smouldering) to > 1000°C (combustion), depending on air excess, ignition modes (standard vs. booster), fuel composition, etc. ...
Article
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This article describes the design and commissioning of a micro-combustor for energy recovery from human faeces, which can operate both in updraft and downdraft modes. Energy recovery from faecal matter via thermochemical conversion has recently been identified as a feasible solution for sanitation problems in low income countries and locations of high income countries where access to sewage infrastructures is difficult or not possible. This technology can be applied to waterless toilets with the additional outcome of generating heat and power that can be used to pre-treat the faeces before their combustion and to ensure that the entire system is self-sustaining. The work presented here is framed within the Nano Membrane Toilet (NMT) project that is being carried out at Cranfield University, as part of the Reinvent the Toilet Challenge of the Bill and Melinda Gates Foundation. For this study, preliminary trials using simulant faeces pellets were first carried out to find out the optimum values for the main operating variables at the scale required by the process, i.e. a fuel flowrate between 0.4 and 1.2 g/min of dry faeces. Parameters such as ignition temperature, residence time, and maximum temperature reached, were determined and used for the final design of the bench-scale combustor prototype. The prototype was successfully commissioned and the first experimental results, using real human faeces, are discussed in the paper.
... The potentiality of nutrient recycling from faeces through pyrolysis was calculated based on literature data [35][36][37][38]. The average biochar production from faeces and other waste bio-solid were considered for calculating biochar production rate while the average concentration of C, N, P and K in the biochar was used for calculating nutrient content in the faeces biochar. ...
Conference Paper
Municipal organic waste and human excreta contain a large amount of nutrients, which could be a resource for agriculture if recycled and reused. These nutrients are usually dumped to water channels deteriorating the environment. In the current study, we estimated the nutrient loading from municipal organic waste and human excreta using linear modelling, explored the potential consequences to ecosystem services and finally proposed several management strategies. Waste and human excreta generation were calculated from the per capita generation rate while nutrient concentrations were considered as the average of literature values. The daily carbon, nitrogen, phosphorus and potassium loading from municipal organic waste, urine and faeces to the water bodies around the major cities in Bangladesh were respectively 3290 t (≈5351 t organic matter), 307 t (≈591 t urea), 54 t (≈ 203 t TSP) and 94 t (≈ 117 t MOP). The large nutrients dumping into water often reduce dissolved oxygen content resulting loss of biodiversity. Combined pyrolysis and composting of municipal organic waste while nutrient harvesting through adsorption with activated carbon, biochar and zeolite could potentially be used for recycling of nutrients. Moreover, precipitation and recycling of nitrogen as isobutyraldehyde-diurea and phosphorus as struvite may also be practiced. Biological trapping with algae or other quick growing plants may contribute significantly in recycling of nutrients. Altogether, our study provides a comprehensive understanding of nutrient loading and its potentials recycling options that may help to attain environmental sustainability.
... Recycling waste water has also the benefit of extracting energy from the sludge which creates new opportunities for income generation and enlarges the resource base available to poor households especially in developing countries. Briquettes made from sewer sludge have energy content that are comparable to those of commercial charcoal briquettes making them a potential substitute that also contributes to the preservation of the environment (Ward et al., 2014). ...
Article
Full-text available
Urbanization causes changes in social and environmental conditions with most of these changes impacting on the efficient provision of essential services such as water and sanitation. Nakuru Municipality was observed to be the fastest growing urban area in East and Central Africa. Research on patterns and trends of urban and population increase and their implication on water service provision and sanitation in urban Nakuru is very scanty. This paper presents findings from an assessment of the effects of population growth between 1999 and 2017 on urban extent and supply of water and sewage reticulation in Nakuru municipality and surrounding peri-urban areas. Data was collected through remote sensing and administration of questionnaires to urban Nakuru residents and key informants from NAWASSCO respectively to elicit information on the water supply network and sewerage reticulation in Nakuru municipality for the period 1989-2014. Geographic Information System (GIS) was used to analyze the data on time series. The results indicate that the population of Nakuru municipality and surrounding peri-urban areas has increased by 56.8% whereas that of built-up area has increased by 182.5% in the same period through densification of the urban core and expansion to the peri-urban areas characterized by urban sprawl. The water supply network and sewerage reticulation increased by 236km and 89km respectively within Nakuru municipality. The analysis of the maps shows that water supply network and sewerage reticulation are concentrated in the area around the urban core with very little spread. This means that the residents on the outskirts of Nakuru Municipality are not well served by the water supply network and sewerage reticulation. The study recommends involvement of all stakeholders in urban planning and in the water sector in order to increase water supply network and sewerage reticulation coverage both in the urban and peri-urban areas.
... This gas can be combusted and used in generators or in special cooking stoves. Collected organic matter can also be used as a component in solid fuels, like briquettes that are combusted for industrial, agricultural, or cooking purposes [50,51]. Alternatively, excreta can also be fed to Black Soldier Fly larvae [52], which are rich in both fat and protein. ...
Article
Full-text available
People in Base of the Pyramid markets still face difficulties when it comes to sanitation. Container-based Sanitation (CBS) services represent a promising advanced sanitation service. Despite the observed outcomes of CBS services, organizations face obstacles when providing these services. To overcome these obstacles, digital transformations of these services are being carried out. We rely on multiple case studies to understand these digital transformations. Our findings highlight (1) the challenges these case organizations faced before engaging in the digital transformation, (2) their individual digital transformation pathways, and (3) a general framework for digital transformations in BoP markets.
... There is no doubt that if safe disposal of sludge is not ensured, gains achieved by increased sanitation coverage cannot be realized. A recent study [3] has shown that about 1.5 billion people worldwide use toilets connected to septic systems that dump raw sewage into surface waters or drains. However from environmental and public health protection considerations it is required that the fecal sludge from onsite systems has to be collected, transported, treated and disposed according to a proper management plan. ...
Conference Paper
This study aims at depicting the present scenario of fecal sludge generation of different zones of Dhaka city and predicting future scenarios to make people as well as the policy makers aware of the importance of fecal sludge management (FSM). It involves developing zoning maps of fecal sludge generated in different zones of Dhaka city. The dry solid volume of sludge was determined based on population using septic tanks in different zones. Volume of sludge in future was predicted up to 2035 depending on future population which was calculated using growth rate of population. Narayanganj, zone-4 and zone-7 were found to be the zones having higher fecal sludge volume compared to others. It was also found that sludge volume would be increased by about 38% and 78% on 2025 and 2035 respectively indicating importance of a sustainable fecal sludge management for the city. Finally zoning maps were developed based on fecal sludge volume reflecting present as well as future scenarios which might facilitate the policy makers to assign relative importance while planning for fecal sludge management.
... After P recovery, those hydro-chars showed combustion energy production rates comparable to those of high-end sub-bituminous coals, which provide additional value to biochar after P recovery. Additionally, Ward et al. (2014) found human fecal chars made at 300 C with similar energy content to wood-chars and bituminous coal. ...
Article
Phosphorus ore extraction for soil fertilization supports the demand of modern agriculture, but extractable resource limitations, due to scarcity, impose a P reuse and recycling research agenda. Here we propose to integrate biochar production (pyrogenic carbon) with municipal and agricultural waste management systems, to recover and reuse phosphorous that would otherwise be lost from the ecological food web. A meta-analysis and available data on total P in biochar indicated that P-enriched feedstocks include animal manure, human excreta, and plant-biomass collected from P-polluted sites. Phosphorus in biochar could participate in P equilibriums in soils and is expected to supply P. The release, sorption and desorption of P by biochar will codetermine the potential of P replenishment by biochar and P loss from biochar-amended soils. Abiotic and biotic factors are expected to affect sorption/desorption of P between biochar and soil aggregates, and P acquisition by plants. Chemical extraction, using acid or alkaline solutions, is considered as a means for P retrieval from high P biochar, especially for biochar with high heavy metal contents. To bridge the gap between academia and practice, this paper proposes future development for phosphorus acclamation by pyrolysis: 1) identification of high-P bio-waste for pyrolysis; 2) retrieval of P by using biochar as soil amendment or by chemical leaching; 3) biochar modification by inorganic nutrients, P solubilizing microorganisms and other organic matter; and 4) compatible pyrolysis equipment fit to the current waste management context, such as households, and waste water treatment plants.
... Cassava starch has a moisture content of 13.09% on dry basis, ash content of 0.24%, a pH of 5.34 and a calorific value of 0.159 MJ/kg [34]. Cardboard and Saw dust 16.94 [35] Rice Husk 17.04 [36] Rice Straw 17.98 [36] 90%Rice Straw + 10% Rice Husk Ash 17.01 [36] Groundnut shells and bagasse 22.5 [15] Waste compost 22.42 [37] Sugar cane leaves (cow dung binder) 19.11 [38] Waste Plastic and Coal 19.27 [18] Buffing Dust of Total Solid Wastes 20.17 [39] Human Waste 25.1 [40] Used Tire 23.02 [41] Industrial Plastic 18.21 [41] Waste Oil 14.65 [41] Paper and saw dust 16.68 [13] Leather and Sludge 7.68 [42] Elephant grass blended with 50% coal 18.53 [43] Gmelina Arborea 18.6 [43] Comparisons were made with other biomass-derived briquettes as presented in Table 6. The TSW briquettes where surpassed in calorific value by briquettes developed from human waste. ...
Article
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The tannery industry is renowned for the huge amount of toxic solid and liquid waste generated from the cleaning, fleshing, splitting, tanning, shaving and buffing of raw materials. Biomass briquettes are a proven way of generating energy from waste. This study investigates the development and characterization of biomass briquettes from tannery solid wastes (TSWs). TSWs, which comprise hair, flesh, chrome shavings and buffing dust, were collected from a tannery in Kano, Nigeria, to formulate and characterize six briquettes. Scanning electron microscopy and proximate analysis were carried out on the samples. The six briquettes, comprising varying ratios of hair, flesh, chrome shavings and buffing dust, were molded and characterized. Thermal efficiency, durability and compressive strength, among other properties, were determined for the six briquette formulations. The briquettes developed had calorific values between 18.632 and 24.101 MJ/kg. Durability of the briquettes ranged from 98.12% to 99.77%. The energy values were within the range of 17.462–24.101 MJ/kg, which was comparable to other fuel sources such as sub-bituminous coal (20.000–24.730 MJ/kg). This study shows that TSWs can be used for fuel briquette production, which is a source of sustainable energy generation. It is environmentally friendly, cost effective and affordable compared to fossil fuel.
... For char production, a pyrolysis temperature of 350°C with a hold time of 10 minutes had the highest calorific value and lowest ash content. Pyrolysing faecal sludge can improve the fuel quality (H:C and O:C molar ratios) (Ward et al., 2014), destroys pathogens, and eliminates volatile odor-causing compounds. However, even when produced at optimal conditions, faecal sludge char can have a high ash content (up to 56% of dry solids), which contributes to a low calorific value (Bleuler, 2016). ...
Conference Paper
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The goal of this project was to improve the resource-recovery value of faecal sludge treatment products. A market assessment identified coffee husks, spent grain, and sawdust as optimal organic wastes to co-process with faecal sludge to increase its fuel value. Drying times of faecal sludge to 90% solids were reduced by half with co-pelletizing with these organic wastes. Briquettes produced with char had comparable heating value, fuel performance, and emissions to charcoal briquettes currently being sold. Use of pellets as a fuel was tested in a gasifier and in several industrial clay kilns (after crushing). High ash content led to clinker formation in the gasifier, but performed well in kilns. The potential market for co-processed faecal sludge fuels is high in Kampala, Uganda, especially among industries, however, the market for pellets needs to be developed.
... ). Fecal chars made at low temperatures can be briquetted, e.g., with molasses/lime and starch binders, resulting in heating values of around 25 megajoule kg -1 , which are comparable to those of commercial charcoal briquettes, making fecal char briquettes a potential substitute(Ward et al. 2014). ...
Book
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In low- and middle-income countries, the management of fecal sludge from on-site sanitation systems has received little attention over many decades, resulting in insufficient or missing regulations to guide investments and management options. To address this gap, this report examines existing and emerging guidelines and regulations for fecal sludge management (FSM) along the sanitation service chain (user interface, containment, emptying, transport, treatment, valorization, reuse or disposal). It also draws empirical examples from guidelines across the globe to support policy-makers, planners, and sanitation and health officers, as well as consultants in low- and middle-income countries in the development and design of local and national FSM guidelines and regulations.
... Molasses, a by-product of sugarcane processing, has been widely used as binder for briquette of coal products to improve their physical properties and combustion properties (Kambo and Dutta, 2014;Blesa et al., 2003). In Ward's study (Ward et al., 2014), the pyrolytic biochar from human waste was pelletized with molasses and the pellet showed excellent mechanical strength and was similar in energy content to bituminous coal. However, until now, the molasses application for hydrochar pelletization was not well studied. ...
... Similarly, energy scarcity affects the poorest people. Around 2 billion people use solid biomass, especially wood which is collected and converted into wood-charcoal, to provide their energy needs, such as cooking and heating; these practices have environmental impacts, including air pollution, greenhouse gas emissions, deforestation, and soil erosion (Bailis et al., 2003;Ward et al., 2014). ...
Article
Poor sanitation due to improper treatment of human excreta, and energy scarcity are global problems with only partial solutions. Thus, feasible conversion of human excreta into safe, reusable “products” and renewable energy could be advantageous. The research objectives were to study the properties and major chemical processes occurring during hydrothermal carbonization of raw human excreta with typical solids content, as well as exploring potential use of the resulting hydrochar and aqueous phase. Human excreta (often considered as black water) were hydrothermally carbonized in a set of nine 50-mL laboratory batch reactors under a range of severities, a single parameter obtained from a coalification model that represents the combination of temperature and time. Three temperatures (180, 210 and 240 °C) and reaction times (30, 60 and 120 min) were used. The physicochemical characteristics such as yield, elemental composition, organic matter and calorific value of the hydrochar (solid phase) were studied. Aqueous phase was characterized for carbon, nitrogen, macro and micronutrients composition. In addition, the potential use of the hydrochar and aqueous phase were studied. There was high correlation between severity factor and carbon content (R² = 0.95) and calorific value (R² = 0.89). Hydrochar yield decreased with increasing severity from 69 to 56%. Calorific values increased from 24.7 to 27.6 MJ/kg, falling within the calorific range of sub-bituminous coal. The aqueous phase demonstrated high nitrogen concentration, reaching up to 8178 mg/L total nitrogen, while N:P:K ratios were similar to those of commercial fertilizers. Pilot scale experiments resembled the results found in laboratory scale experiments for both hydrochar and aqueous phase and fitted the regression curves obtained from the severity factor. It is postulated that hydrothermal carbonization of human excreta could potentially serve as a sustainable sanitation technology with a closed-loop cycle approach while recovering energy and nutrients.
... Drying is a crucial step in any thermal treatment process. It has been estimated that more than 95% of the energy required to produce char from feces is used in drying feces [10] and 50% of the heat required from fuel could be sufficient for all pre-drying, drying, and pyrolysis steps [11]. Drying is driven by the difference between the thermodynamic activity of water as vapor in the atmosphere and water as moisture in the wet solid. ...
Article
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The drying (or dewatering) of fresh feces and fecal sludge is a productive step in the management of sanitation, waste treatment, and resource recovery services. An improved understanding of fresh feces and fecal sludge drying would contribute to the development and deployment of fecal sludge management services. However, there is a lack of available literature on the fundamental drying characteristics of fresh feces. In response to this gap, this work shares experimental results for equilibrium moisture content of fresh feces at different water activity levels (aw) and proposes the use of the Guggenheim, Anderson, and de Boer (GAB) model for predicting aw, calculating the heat of sorption, and estimating the corresponding energy requirements for drying of fresh feces. This is the first time this work has been done with fresh feces. The total heat of evaporation was significant up to a moisture content of about 0.2 kg water per kg dry solids. In addition to informing drying process design, the sorption isotherm can be used to predict microbial activity, which could improve the management of feces and fecal sludge from a public health perspective. These data in turn will be used to promote access to dignified, safe, and sustainable sanitation.
... It is anticipated that the fecal waste can be converted to char with longer times on sun, and with improved insulation around the receiver. Human fecal chars have been shown to have a higher heating value (HHV) comparable to that of cooking and heating fuels commonly used throughout the world, such as wood charcoal or bituminous coal [46]. ...
Article
Full-text available
Almost half of the world’s population is living without access to sanitation services that are safe, reliable, and minimize public health risk of human waste exposure. Modern flush-based sanitation networks are unsustainable: substantial resources, namely water and fuel, are required to bring human waste to centralized treatment facilities. Moving toward sustainable sanitation requires the implementation of innovative renewable energy technologies for stabilization and disinfection of waste, at the local or household scale, where minimal inputs of water, electricity or chemicals are required. A novel solar thermal disinfection toilet prototype has been constructed and is assessed for overall solar to receiver efficiency in treating waste without electrical, chemical, or water inputs from municipal supply. The measured solar to receiver efficiency is 28%, incorporating the capturing and concentration of sunlight and transmission of the energy to the receiver. For a typical sunny day, the current system can achieve thermal treatment of 0.8 kg human waste in roughly 100 min. The novel toilet is available for any location in the world with sufficient sunlight and irradiance data, and is scalable by adding solar collectors for sizes from single dwellings to communities.
... Pellets, unlike coal, are renewable, carbon-based, and possess high-calorific energy that finds application in various industries (Mitchual et al. 2013). A recent study has reported the use of fecal-char pellets for heating purposes (Ward et al. 2014). The characterization of manufactured pellets is to be tested for calorific value, ash content, moisture content, fixed carbon content, and Thermogravimetric analysis (Oliveira et al. 2017). ...
Article
The conversion of agro-residues to value added products is a potential opportunity for all agrarian countries. This study involves the utilization of agro-waste sourced from farmlands, and plant foliage waste collected from university premises, both blended with the distillery sludge in a ratio of 1:1 to prepare pellets. The pellet samples were tested with proximate analysis and ultimate analysis. The gross calorific value of the coal sample was 8967.23 kcal/kg, whereas the plant waste and sludge blend sample indicated a value of 7121.70 kcal/kg. The pellets produced from farm waste and sludge showed a value of 8621.334 kcal/ kg which is close to the gross calorific value of coal. The burning rate of the pure coal was found to be the highest with a value of 0.156 mg/min, followed by a mixture of farm waste and sludge with 0.129 mg/min and a blend of plant waste and sludge with 0.00745 mg/min, respectively. This research highlights the possibility of converting distillery sludge, plant waste, and farm waste into alternate fuel source.
... The potentiality of nutrient recycling from faeces through pyrolysis was calculated based on literature data [35][36][37][38]. The average biochar production from faeces and other waste bio-solid were considered for calculating biochar production rate while the average concentration of C, N, P and K in the biochar was used for calculating nutrient content in the faeces biochar. ...
Chapter
Biological organisms including humans require mineral nutrients for their growth and development. A significant amount of these nutrients remain unused in the left over materials, known as waste, causing environmental degradation. These nutrients could potentially be a resource for agriculture if recycled and reused. Therefore, a critical examination of nutrient loading from waste such as from human excretion and biowaste is required. Here, we estimated the nutrient loading from municipal organic waste (MOW) and human excreta using linear modelling, explored the potential consequences to ecosystem services and proposed several management strategies. Waste and human excreta generation were calculated from the per capita generation rate while nutrient concentrations were considered as the average of literature values. The daily carbon (C), nitrogen (N), phosphorus (P) and potassium (K) loading from MOW, urine and faeces to water bodies around the major cities in Bangladesh were estimated at 2158, 112, 58 and 91 t, respectively. The nutrient loading to water bodies reduces several ecosystem service with estimated cost of BDT. 42.93 million for the reduction in fish production and half of property rent. Combined pyrolysis and composting of municipal organic waste can reduce the volume of organic waste Similarly, pyrolysis of faeces and then, sorption of nutrients using the produced biochar could recycle 440 t C, 71 t N, 113 t P and 73 t K day−1.Combing the nutrient recycling through pyrolysis-composting of MOW and faeces pyrolysis-sorption of nutrients from urine, the estimated nutrient recycling was 39% C, 11% N, 68% P and 11% K of the intrinsic nutrients in waste. Altogether, our study provides a comprehensive understanding of nutrient loading, its consequences and potential recycling options that may help to attain environmental sustainability.
... • Fecal matter • Starch, molasses, lime • [62] Textile industry solid waste • Biosludge, cotton residue. ...
Article
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Growing global demand and utilization of fossil fuels has elevated wealth creation, increased adverse impacts of climate change from greenhouse gases (GHGs) emissions, and endangered public health. In most developing countries, biomass wastes, which include but are not limited to agricultural residues, are produced in large quantities annually. They are either inefficiently used or disposed of indiscriminately, which threatens the environment. It is possible to convert these wastes, through densification, into high-density and energy-efficient briquettes. Densification of biomass into briquettes presents a renewable energy option as an alternative to fossil fuels. This paper reviews biomass briquetting with reference to biomass resources, feedstock pre-processing, briquetting process parameters, briquetting technology, and briquettes quality evaluation parameters. The review also includes the economic aspect of briquetting relating to costs and feasibility.
... Binding materials like molasses, lime, and starch binders were used for producing the briquettes. The final CV were comparable to commercial charcoal briquettes, concluding that fecal char briquettes contributes to the preservation of the environment, substituting charcoal and firewood (Ward et al., 2014). On balance, the production of dung-based briquettes is a matter of research, although only a few articles have been published in the last decades. ...
Article
Solid waste management and the increasing energy demand are a global concern. Waste can play the role of alternative fuel, partly reducing the environmental footprint in the waste management sector. Waste briquetting is used as a treatment option for improving waste combustion efficiency, as well as its management and handling. This critical review aims at evaluating the potentialities of this method as a possible solution to introduce alternative fuels in developing countries. Totally, 85 scientific articles available from 1999 to 2021 from international databases were reviewed, and a SWOT analysis has been conducted following the indications underlined in the scientific literature. The outcomes of the review highlight that agricultural waste-based and wood-based briquettes are the most investigated, followed by plastics-based briquettes and paper & cardboard-based briquettes. Waste-based briquettes can be divided into three categories, function of the calorific value: biomass-based (16.22 ± 1.65 MJ kg⁻¹), wood-based (19.03 ± 2.46 MJ kg⁻¹), and plastics and charcoal-based briquettes (24.64 ± 5.29 MJ kg⁻¹). Review findings underline that in-door emissions analysis is lacking, as well as research related to the water boiling test for the valorisation of waste briquetting for cooking and heating systems in developing countries. The current review contributes to highlighting the importance in implementing appropriate technologies for energy production and waste management in developing countries.
... Char quality and properties are determined by pyrolysis parameters including heating duration, maximum temperature, pressure, and oxygen content, which can vary with different feedstock [25]. Ward et al. [26] and Harussani et al. [27] mentioned that the characteristics and attributes of the char are mainly depend in high extent of the composition of the waste to be pyrolysed. Thus, it will affect its surface area and porosity. ...
Conference Paper
Full-text available
The importance of carbon-based nanomaterials for various uses in today's world has prompted efforts to develop simple, cost-effective synthesis methods from abundantly available wastes. By thermally processing organic waste, pyrolysis in a broad spectrum is commonly used for the creation of carbon nanostructures. The growth of carbon nanomaterials is a difficult process that is heavily controlled by temperature, catalyst, and precursor type. Significant progress has been achieved in refining nanomaterial growth techniques in recent years, opening up new avenues for commercial carbon-based nanomaterial production. In this study, different pyrolysis techniques for the synthesis of carbon-based nanomaterials, specifically carbon nanotubes (CNTs), carbon nanofibers (CNFs), and graphene, are examined (G). The features of carbon-based composites are described in this review article for their specific application in defence sectors such as aeronautics, maritime-naval ships and submarines, automobiles, electronics, EMI shielding, and constructions.
... Despite the potentials provided by the use of faecal waste for biogas production, the technology is still beset by acceptability and sociocultural issues (Buit and Jansen 2016). Thus, a deep understanding of the acceptability and sociocultural issues surrounding faecal waste becomes very important if the deployment of faecal waste-to-biogas plants are to be successful (Ward et al. 2014). ...
Article
Full-text available
The use of wastes for biogas production has been restricted to few feedstock like cattle manure and food waste. Increasing the feedstock base for biogas production is capable of increasing the sustainability of feedstock availability. This study seeks to assess sociocultural and acceptability issues associated with the use of faecal waste (human excreta, cattle manure, etc.) as a source of energy in selected stakeholder areas in Benin City, Nigeria. Qualitative research methods were used for data collection as data were generated through survey questionnaire. Field responses were mined and analysed using Factor analysis and cluster plots generated from Factor plots were analysis using Statistical Program for Social Sciences to rank the variables in order of hierarchical means. Analyses from this study have shown that faecal waste is a dependable feedstock for biogas production while adding value to food production through digestate utilization. Furthermore, high factor loading of 0.759 for acceptance to the fact that biogas from faecal waste has the potential to improve environmental sanitation in Benin City. However, there exist considerable knowledge gap as shown in the analyses which suggest a need for continuous awareness creation, policy formulation and orientation on the importance of biogas production from a range of feedstock in tackling energy security and sustainability in line with SDGs 2, 6 and 7.
... Char quality and properties are determined by pyrolysis parameters including heating duration, maximum temperature, pressure, and oxygen content, which can vary with different feedstock [25]. Ward et al. [26] and Harussani et al. [27] mentioned that the characteristics and attributes of the char are mainly depend in high extent of the composition of the waste to be pyrolysed. Thus, it will affect its surface area and porosity. ...
Conference Paper
Full-text available
The importance of carbon-based nanomaterials for various uses in today's world has prompted efforts to develop simple, cost-effective synthesis methods from abundantly available wastes. By thermally processing organic waste, pyrolysis in a broad spectrum is commonly used for the creation of carbon nanostructures. The growth of carbon nanomaterials is a difficult process that is heavily controlled by temperature, catalyst, and precursor type. Significant progress has been achieved in refining nanomaterial growth techniques in recent years, opening up new avenues for commercial carbon-based nanomaterial production. In this study, different pyrolysis techniques for the synthesis of carbon-based nanomaterials, specifically carbon nanotubes (CNTs), carbon nanofibers (CNFs), and graphene, are examined (G). The features of carbon-based composites are described in this review article for their specific application in defence sectors such as aeronautics, maritime-naval ships and submarines, automobiles, electronics, EMI shielding, and constructions.
... Solar drying of fecal sludge from pit latrines in bench-scale tests resulted in an average drying rate between 0.5 and 0.8 kg/h/m 2 (Septien et al. 2018). Ward et al. (2014) investigated a solar-powered pyrolysis reactor known as the Sol-char toilet to convert fecal sludge from pit latrines into pathogen-free biochar. Another solar thermal water heater system was tested at laboratory scale to dry and disinfect fecal sludge (Sweya & Mgana 2020). ...
Article
Full-text available
On-site sanitation systems such as pit latrines are extensively used around the world, while there is a growing number of evidence documenting the impact of pit latrines on groundwater quality that may affect human health. Hence, this paper summarizes the various safe-sanitation technologies by broadly categorizing them into fecal pathogen disinfection methods (anaerobic digestion, chemical disinfection, biological additives, solar pasteurization and vermicomposting) and capturing methods (pit lining and permeable reactive barriers, the latter of which simultaneously capture and sanitize fecal sludge in pit latrines). While some of the reviewed technologies have been widely practiced for mitigating microbial contamination of the groundwater, others are still in the early stage of commercialization and field validation. Though there are challenges to the selection and adoption of the most appropriate technology, this paper discusses the readiness of each technology as a stand-alone fecal sludge management solution. HIGHLIGHTS Pit latrines impact groundwater quality that may affect human health.; Low-cost treatment techniques are discussed to capture and treat pathogens in pit latrines.; Pit liners such as peat, clay, hydrophobic membranes and permeable reactive barriers help capture pathogens.; When compared with other methods, the chemical disinfection method with chlorine, lime, Ikati and Soda ranked best with the highest score.;
... The negative side is more pronounced because it generates some of the major environmental and health difficulties faced by people living in poor societies, comprising of water pollution and the transmission of diseases and infections which affects around 2.5 billion people in unindustrialized countries with 300 million people from Africa [3][4]. Fitting and operating sewage plus wastewater treatment plants is costly and conventional wastewater management is not an ecologically friendly process since so much energy is utilized and has disposal complications issues [5]. Consequently, due to cost, many areas in the developing nations have opted out [4]. ...
... N/mm 2 for briquettes with 30-40% moisture content produced using 10 wt% cassava starch as a binder and those results are less than the ones (0.09-0.42 N/mm 2 ) obtained in this study. According to Turkish Standard (TS)12055, Class I briquettes should have a compressive strength greater than 13 N/mm 2 , while Class II briquettes should withstand a compressive strength not lower than 10 N/mm 2 (Haykiri-Acma, Yaman, and (Ward, Yacob, and Montoya 2014). ...
Article
This study investigated the use of African Elemi (Canarium Schweinfurthii) resin as a binder for the production of carbonized briquettes from charcoal fines. The binder and charcoal fines were characterized through proximate analysis, ultimate analysis, higher heating value, and SEM. Four briquette samples (B25, B30, B35, and B40) with a ratio of charcoal fines: binder of 3:1, 7:3, 13:7, and 3:2, respectively, were produced at a compaction pressure of 5.92–7.96 MPa. The physical properties of the briquettes determined were bulk density, impact resistance index (IRI), compressive strength, splitting tensile strength, water resistance index (WRI), and morphology. The chemical properties of the briquettes determined were proximate analysis, ultimate analysis, higher heating value (HHV), and energy density. One-way ANOVA and Fisher’s LSD were used to analyze the chemical properties of briquettes. The briquettes had a bulk density of 0.770–1.036 g/cm³, IRI of 2.90–73.33, compressive strength of 2.25–10.94 N/mm², splitting tensile strength of 0.09–0.42 N/mm², WRI of 99.26–99.29, and an HHV of 29.7–31.3 MJ/kg. The briquette properties were found to be comparable to results from other studies.
Article
This study investigated the potential of using locally available municipal solid wastes (MSW) (such as food wastes from restaurants, charcoal dust, coconut husk and shell, and sawdust) as feedstock to produce non-carbonized fuel briquettes. A low-cost briquetting machine sourced from Alfaster Industries in Kenya served to demonstrate the concept. Using decomposed food waste resulted in briquettes with higher bulk density (+4%), greater net calorific value (+18%) and lower burning rate (-24%), compared to the use of regular food waste. There was no significant difference in ash content from the two briquette types. The results also indicate that decomposing food waste and mixing it with tree-based raw materials such as coconut waste, charcoal waste or sawdust improves the quality of briquettes, and enhances the temperatures achieved during combustion. This recycling solution has the potential to serve multiple benefits in MSW management for sustainable cities while reducing rural land degradation and deforestation.
Article
Background: The provision of safe sanitation services is essential for human well-being and environmental integrity, but it is often lacking in less developed communities with insufficient financial and technical resources. Hydrothermal carbonization (HTC) has been suggested as an alternative sanitation technology, producing value-added products from faecal waste. We evaluated the HTC technology for raw human waste treatment in terms of resource recovery. In addition, we constructed and tested a low-cost HTC reactor for its technical feasibility. Methods: Raw human faeces were hydrothermally treated in a mild severity range (≤ 200 °C and ≤ 1 hr). The total energy recovery was analysed from the energy input, higher heating value (HHV) of hydrochar and biomethane potential of process water. The nutrient contents were recovered through struvite precipitation employing process water and acid leachate from hydrochar ash. A bench-scale low-cost reactor (BLR) was developed using widely available materials and tested for human faeces treatment. Results: The hydrochar had HHVs (23.2 - 25.2 MJ/kg) comparable to bituminous coal. The calorific value of hydrochar accounted for more than 90% of the total energy recovery. Around 78% of phosphorus in feedstock was retained in hydrochar ash, while 15% was in process water. 72% of the initial phosphorus can be recovered as struvite when deficient Mg and NH 4 are supplemented. The experiments with BLR showed stable operation for faecal waste treatment with an energy efficiency comparable to a commercial reactor system. Conclusions: This research presents a proof of concept for the hydrothermal treatment of faecal waste as an alternative sanitation technology, by providing a quantitative evaluation of the resource recovery of energy and nutrients. The experiments with the BLR demonstrate the technical feasibility of the low-cost reactor and support its further development on a larger scale to reach practical implementation.
Article
This study explored the production and evaluation of briquettes made from dried fecal sludge mixed with fresh food waste as a dual strategy to solve energy poverty and poor sanitation problems in Ugandan slums. Cylindrical briquettes measuring 82 mm height by 76 mm diameter were produced from dried fecal sludge (FS) alone, and FS mixed separately with pineapple peels (FS + PP), charcoal fines (FS + CD), and bean husks (FS + BH) in a mix ratio of 50% FS: 50% biomass (wt/wt basis) using red soil as the binder. Physiochemical characteristics and fuel thermal efficiency of the briquettes were tested following ASTM standards and were compared to wood-derived charcoal and commonly traded briquettes on market in Uganda. The average moisture content was 5.1%. Bulk density was highest in FS briquettes (1.12 g/cm³) and lowest in FS + BH (0.847 g/cm³). Volatile matter (VM) was highest in FS + PP (39%) and lowest in FS alone (25.7%). The average ash content was 30.4%. FS + PP had the highest calorific value (17.92 MJ/kg) while FS alone had the lowest (6.19 MJ/kg). The highest burning rate was recorded in FS + CD briquettes (8 g/min) and was lowest in FS + PP (4 g/min). Based on the calculated burning rates and calorific values, the economic advantage calculations implied that blending one ton of dry FS with one ton of dry pineapple peels for fuel briquettes, and their use as a substitute could save consumers about USD 620 per ton of wood charcoal foregone.
Article
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Background: The provision of safe sanitation services is essential for human well-being and environmental integrity, but it is often lacking in less developed communities with insufficient financial and technical resources. Hydrothermal carbonization (HTC) has been suggested as an alternative sanitation technology, producing value-added products from faecal waste. We evaluated the HTC technology for raw human waste treatment in terms of resource recovery. In addition, we constructed and tested a low-cost HTC reactor for its technical feasibility. Methods: Raw human faeces were hydrothermally treated in a mild severity range (≤ 200 °C and ≤ 1 hr). The total energy recovery was analysed from the energy input, higher heating value (HHV) of hydrochar and biomethane potential of process water. The nutrient contents were recovered through struvite precipitation employing process water and acid leachate from hydrochar ash. A bench-scale low-cost reactor (BLR) was developed using widely available materials and tested for human faeces treatment. Results: The hydrochar had HHVs (23.2 - 25.2 MJ/kg) comparable to bituminous coal. The calorific value of hydrochar accounted for more than 90% of the total energy recovery. Around 78% of phosphorus in feedstock was retained in hydrochar ash, while 15% was in process water. 72% of the initial phosphorus can be recovered as struvite when deficient Mg and NH 4 are supplemented. The experiments with BLR showed stable operation for faecal waste treatment with an energy efficiency comparable to a commercial reactor system. Conclusions: This research presents a proof of concept for the hydrothermal treatment of faecal waste as an alternative sanitation technology, by providing a quantitative evaluation of the resource recovery of energy and nutrients. The experiments with the BLR demonstrate the technical feasibility of the low-cost reactor and support its further development on a larger scale to reach practical implementation.
Article
Sludge treatment is an integral part of faecal sludge management in non-sewered sanitation settings. Development of pyrolysis as a suitable sludge treatment method requires thorough knowledge about the properties and thermal decomposition mechanisms of the feedstock. This study aimed to improve the current lack of understanding concerning relevant sludge properties and their influence on the thermal decomposition characteristics. Major organic compounds (hemicellulose, cellulose, lignin, protein, oil and grease, other carbohydrates) were quantified in 30 faecal sludge samples taken from different sanitation technologies, providing the most comprehensive organic faecal sludge data set to date. This information was used to predict the sludge properties crucial to pyrolysis (calorific value, fixed carbon, volatile matter, carbon, hydrogen). Samples were then subjected to thermogravimetric analysis to delineate the influence of organic composition on thermal decomposition. Septic tanks showed lower median fractions of lignin (9.4%dwb) but higher oil and grease (10.7%dwb), compared with ventilated improved pit latrines (17.4%dwb and 4.6%dwb respectively) and urine diverting dry toilets (17.9%dwb and 4.7%dwb respectively). High fixed carbon fractions in lignin (45.1%dwb) and protein (18.8%dwb) suggested their importance for char formation, while oil and grease fully volatilised. For the first time, this study provided mechanistic insights into faecal sludge pyrolysis as a function of temperature and feedstock composition. Classification into the following three phases was proposed: decomposition of hemicellulose, cellulose, other carbohydrates, proteins and, partially, lignin (200–380 °C), continued decomposition of lignin and thermal cracking of oil and grease (380–500 °C) and continued carbonisation (>500 °C). The findings will facilitate the development and optimisation of faecal sludge pyrolysis, emphasising the importance of considering the organic composition of the feedstock.
Article
Slow-pyrolysis is a treatment technology that is being explored for treatment of faecal sludge (FS) from onsite sanitation technologies. Next to pathogen inactivation, the technology produces treatment products. Revenues from these products could offset treatment costs and contribute to financially viable sanitation. In comparison to lignocellulosic biomass and other biowastes, little information is available on operating parameters for FS pyrolysis to produce char for different resource recovery options. In Kampala, Uganda, this bench-scale study investigated the influence of two major operating parameters, hold time (10, 20 and 40 minutes) and pyrolysis temperature (350, 450 and 600 C) for pyrolysis of FS into char for solid fuel production, soil enhancement and carbon sequestration. Hold time: 10 min was the most suitable hold time for all resource recovery options as char characteristics had only minor variations between hold times. Temperature: Char characteristics identified 350 C as the most suitable for fuel production and 450 or 600 C for carbon sequestration. FS char had characteristics for soil enhancement comparable to biowaste and lignocellulosic biomass chars, with heavy metal concentration exceeding guideline concentrations. The most suitable temperature needs to be selected based on plant and soil type, and legal regulations.
Article
There is a strong need for transformative sanitation systems in the areas of the world where open defecation habits and/or inadequate sewage treatment methods and facilities exist. This paper describes an innovative thermally efficient solid waste treatment process as a basis for an off-the-grid, non-sewered toilet in order to address this need. Human feces are combusted in a continuous-cyclic manner using two stages of smoldering and catalytic oxidation. It has been shown that thermal coupling of the two stages creates a self-sustained reactor that can combust wet fecal material containing up to 3.2 parts water to 1 part dry matter – equivalent of water content in healthy human feces – without the need for external heating, known as the ultimate challenge in direct combustion of human feces. Furthermore, it has been shown that air flow rate can be reliably used as a controlling mechanism for fecal destruction rate which means the same reactor could be operated for various and varying input rates. The present work demonstrates the potential for manufacturing low-cost, low-energy consuming sanitation systems that are more easily accessible to communities in need of such systems.
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In many low-income cities, a high proportion of fecal sludge, the excreta and blackwater collected from onsite sanitation systems such as pit latrines, is not safely managed. This constitutes a major danger to environmental and human health. The water, sanitation, and hygiene sector has recognized that valorization of treated fecal sludge could offset the upfront cost of treatment by using it as a fuel source. The few quantitative studies on fecal sludge fuel published to date have focused on heating value, moisture, ash fraction, and heavy metals. However, other factors impacting fuel utility, specifically ash speciation, have not been adequately quantified for fecal sludge. This study contributes to closing that gap and shows the value of more detailed quantification. It first characterizes fecal sludge samples from Colorado and Uganda, confirms that the fuel is better if cofired with other biomass, and outlines a framework for determining safe cofire ratios. Second, the study evaluates two methods for improving fecal sludge as a fuel: carbonization and ash leaching. Carbonization of fecal sludge did not improve fuel quality, but leaching showed promise in ash reduction.
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Resource recovery from faecal sludge can take many forms, including as a fuel, soil amendment, building material, protein, animal fodder, and water for irrigation. Resource recovery as a solid fuel has been found to have high market potential in Sub-Saharan Africa. Laboratory- and pilot-scale research on faecal sludge solid fuel production exists, but it is unclear which technology option is most suitable in which conditions. This review offers an overview and critical analysis of the current state of technologies that can produce a dried or carbonized solid fuel, including drying, pelletizing, hydrothermal carbonization, and slow-pyrolysis. Carbonization alters fuel properties, and in faecal sludge, it concentrates the ash content and decreases the calorific value. Overall, a non-carbonized faecal sludge fuel is recommended, unless a carbonized product is specifically required by the combustion technology or end user. Carbonized and non-carbonized fuels have distinct characteristics, and deciding whether to char or not to char is a key judgement in determining the optimal solid fuel technology option. Based on the existing evidence, this review provides a decision-making structure for selecting the optimal technology to produce a faecal sludge solid fuel and identifies the top research needs prior to full-scale implementation.
Article
Hydrothermal carbonization (HTC), as one of the thermal conversion techniques, shows promising commercial potential for hydrochar production from wet biowaste. This technique was re-discovered and regraded as artificial coalification to mimic natural process. In recent years, researchers concern more about hydrochar obtained from HTC, since large amount of organic waste including sludge, algae, food waste, manure etc. are generated with high moisture, which can be directly used as reaction medium, and hydrochar has high carbon density and energy retention. With this regard, application of hydrochar as biofuel is a renewable and sustainable way for biowaste recycling. In this review, HTC process and pathways about hydrochar formation from (N-free/N-rich biowaste), carbon-skeleton structure, critical elements on clean properties, and hydrochar pelletization for biofuel production were presented. Potential applications and challenges for HTC as green and sustainable way were presented, which will provide prospect for hydrochar as clean and renewable biofuel.
Conference Paper
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Bangladesh faces waste management challenges in most of the cities. The untreated fecal sludge is disposed to the water bodies, agricultural fields and lands indiscriminately which in turn is greatly polluting the environment and posing serious health effects. However, it contains nutrients and organic matters which can be used to increase the agricultural productivity. This resource recovery option will eventually reduce pollution load to the environment. This study tried to determine the physicochemical characteristics of dried fecal sludge with a view to assessing the fertilizer potentiality. The fuel potential of the sludge was also tried to assess by determining calorific value using oxygen bomb calorimeter. In this study fecal sludge samples were collected from drying beds in Satkhira, Khulna. Samples of different ages were also collected to determine the impact of sludge age on fertilizer and fuel potentiality as well. A wide variety of parameters of sludge were determined to ascertain the physicochemical characteristics which included color, odor, moisture content, pH, Organic Carbon, Total Nitrogen, C:N ratio, Phosphorus, Potassium, Sulfur, Zinc, Copper, Chromium, Cadmium, Lead, Nickel etc. The results found in experiments met the Bangladesh standard for organic fertilizer. The average calorific values were found to be 7.1 and 4.32 MJ/Kg for 15 days and 21 days dried samples respectively indicating a decrease in fuel potentiality with age.
Article
composting toilets (CFS) provide a promising decentralized alternative to sewer based sanitation systems. However, the valorization of fecal sludge from CFS by conventional technologies is limited. In this study, we evaluated carbonization as an alternative valorization route for CFS, providing a time-efficient, decentral applicable and hygienically safe treatment option. CFS was carbonized using either pyrolysis (at 500 °C for 1 h) or hydrothermal carbonization (HTC at 200 °C for 4 h). CFS exhibits promising feedstock characteristics, such as high total solids (TS 21 ± 9%) and low ash content (9 ± 2%TS). HTC of CFS exhibits high char yields (75 ± 7%) while pyrolysis char from CFS exhibits elevated higher heating values (25 ± 2 MJ kg−1) and low ash (24 ± 5%TS) compared to chars produced from fecal sludge (FS) from other sources. Further calculations showed that FS with low TS amended with sawdust can be used as inexpensive feedstock to achieve energy self-sufficient pyrolysis operation.
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Char, a solid product obtained from carbonization of waste Poly(Ethylene) Terephthalate (PET), has high potential to solve the current plastic waste problem through the synthesis of new carbon-based adsorbents. However, thermal degradation reaction of polymer involves multiple series of complex reaction pathways and the formation of char is not clarified. In this study, the phase behavior of PET carbonization and the mechanism of char formation was studied in detail. Based on the van Krevelen diagram, it is evident that rapid thermal decomposition of PET occurs through decarbonylation to form char and decarboxylation to form wax. Based on the analysis of cross-linking behavior, a correlation between the degree of cross-linking as a function of CO and CO2 and dependent parameters based on the experimental operation was obtained. The findings validified the assumption that scission of CO bond in the carbonyl group through decarbonylation and decarboxylation to release CO and CO2 leads to the formation of char. The cross-linking behavior was further clarified by studying the distribution of cross-linking structure in char and wax. It was confirmed that decarbonylation reaction to release CO is highly associated with the formation of cross-linking to form char in the solid residue, whereas decarboxylation reaction to release CO2 is highly associated with the formation of cross-linking to form aromatic compounds in the wax residue.
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Sustainable methods are required in developing regions to treat and recover value from pit latrine sludge. One potential strategy is to pyrolyse pit latrine contents and generate char and bio-oil, which can then be used as a soil enhancer and fuel, respectively. Despite the many benefits associated with the process, there is very limited relevant literature available. This study examines its feasibility. Initially, the energy balance associated with pyrolysis of sewage sludge was calculated using data from 14 literature studies. For dewatered sewage sludge, the average energy input required during drying and pyrolysis was 2.9±0.2 MJ·kg-1 sludge, while the average net energy recovered from combustion of bio-oil was 6.9±0.2 MJ·kg-1. For sewage sludge which had been dewatered and dried prior to pyrolysis equivalent values were 1.2±0.2 MJ·kg-1 and 8.5±0.9 MJ·kg-1. Parallel calculations were then undertaken with pit latrine sludge as the hypothetical feedstock, assuming a water content of 30, 52, 82 or 97% wt. The energy input required was 2.1, 2.6, 3.3 and 3.6 MJ·kg-1, respectively. Corresponding net energy recoveries from pyrolysis combined with use of the resultant bio-oil as fuel were 9.7±0.8, 7.1±0.8, 6.5±0.8 and 6.1±0.8 MJ·kg-1. Char production is more favourable from stabilised pit latrine sludge with lower moisture and volatile solids content. Barriers to pyrolysis of pit latrine sludge are discussed, including the heterogeneity of pit latrine composition and the difficulty of collecting high-viscosity sludge. Overall, this study demonstrates the potential that pyrolysis has as a disposal and value addition method for pit latrine sludge. Innovative methods for sludge drying and pit emptying will expedite the process becoming a reality.
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Pyrolysis processing is one of several options for solid waste resource recovery in space. It has the advantage of being relatively simple and adaptable to a wide variety of feedstocks and it can produce several usable products from typical waste streams. The overall objective of this study was to produce a prototype mixed solid waste pyrolyzer for spacecraft applications. A two-stage reactor system was developed which can process a maximum of about 0.5 kg of waste per cycle. The reactor includes a pyrolysis chamber where the waste is heated to temperatures above 600 °C for primary pyrolysis. The volatile products (liquids, gases) are transported by a N 2 purge gas to a second chamber which contains a catalyst bed for cracking the tars at temperatures of about 1000-1100 °C. The tars are cracked into carbon and additional gases. Most of the deposited carbon is subsequently gasified by oxygenated volatiles (CO 2 , H 2 O) from the first stage. In a final step, the temperature of the first stage can be raised and the purge gas switched from N 2 to CO 2 and/or O 2 in order to gasify the remaining char in the first stage and the remaining carbon deposits in the second stage. Alternatively, the char can be removed from the first stage and saved as a future source of CO 2 or partially gasified to make activated carbon. This paper describes several improvements that were made in the original (First Generation) prototype pyrolyzer including: 1) replacement of stainless steel flanges with machineable ceramic in order to reduce weight; 2) construction of a new sample holder in order to make sample insertion and removal easier and sample heat-up more uniform; 3) replacement of a stainless steel outer shell with a double-wall quartz cylinder in order to significantly reduce weight and heat losses. In addition, experimental results are included for wheat straw and chicken manure feedstocks, primarily from the First Generation prototype.
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Pyrolysis processing is one of several options for solid waste resource recovery in space. It has the advantage of being relatively simple and adaptable to a wide variety of feedstocks and it can produce several usable products from typical waste streams. The objective of this study is to produce a prototype mixed solid waste pyrolyzer for spacecraft applications. A two-stage reactor system was developed which can process about 1 kg of waste per cycle. The reactor includes a pyrolysis chamber where the waste is heated to temperatures above 600°C for primary pyrolysis. The volatile products (liquids, gases) are transported by a N 2 purge gas to a second chamber which contains a catalyst bed for cracking the tars at temperatures of about 1000 °C – 1100 °C. The tars are cracked into carbon and additional gases. Most of the carbon is subsequently gasified by oxygenated volatiles (CO 2 , H 2 O) from the first stage. In a final step, the temperature of the first stage can be raised and the purge gas switched from N 2 to CO 2 in order to gasify the remaining char in the first stage and the remaining carbon deposits in the second stage. Alternatively, the char can be removed from the first stage and saved as a future source of CO 2 or used to make activated carbon. The product gases from the pyrolyzer will be rich in CO and cannot be vented directly into the cabin. However, they can be processed in a shift reactor or sent to a high temperature fuel cell. A control system based on artificial neural networks (ANNs) is being developed for the reactor system. ANN models are well suited to describing the complicated relationships between the composition of the starting materials, the process conditions and the desired product yields.
Book
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Understanding the sustainable use of energy in various processes is an integral part of engineering and scientific studies, which rely on a sound knowledge of energy systems. Whilst many institutions now offer degrees in energy-related programs, a comprehensive textbook, which introduces and explains sustainable energy systems and can be used across engineering and scientific fields, has been lacking. Energy: Production, Conversion, Storage, Conservation, and Coupling provides the reader with a practical understanding of these five main topic areas of energy including 130 examples and over 600 practice problems. Each chapter contains a range of supporting figures, tables, thermodynamic diagrams and charts, while the Appendix supplies the reader with all the necessary data including the steam tables. This new textbook presents a clear introduction of basic vocabulary, properties, forms, sources, and balances of energy before advancing to the main topic areas of: • Energy production and conversion in important physical, chemical, and biological processes, • Conservation of energy and its impact on sustainability, • Various forms of energy storage, and • Energy coupling and bioenergetics in living systems. A solution manual for the practice problems of the textbook is offered for the instructor. Energy: Production, Conversion, Storage, Conservation, and Coupling is a comprehensive source, study guide, and course supplement for both undergraduates and graduates across a range of engineering and scientific disciplines.
Conference Paper
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This paper continues previous work on pyrolysis processing of solid wastes for spacecraft and planetary surface applications. A domestic microwave oven was modified for use in this work for scoping studies in which the effects of sample composition, use of central microwave absorbers, and secondary pyrolysis of liquids were studied. Experiments were done with wheat straw and various formulations of a feces simulant. The microwave absorbers examined included activated carbon and char produced from previous experiments. The addition of a separate microwave-heated secondary pyrolysis zone was also examined as a means of reducing the liquid product yields. In general, the feces simulants had similar pyrolysis yields when compared to wheat straw for the char and total gas yields, but individual gas yields were different. For example, the feces simulants produced significantly more ethylene, larger amounts of methane, and smaller amounts of carbon oxides (CO + CO 2). This can be largely explained by the differences in elemental compositions. A comparison was also made of the microwave-assisted pyrolysis of feces simulants of variable moisture contents (0-60 wt. %). The higher moisture contents (40-60 wt. %) result in a delay for the onset of pyrolysis and a higher energy demand per gram of sample, as might be expected. However, at lower moisture contents, such as the 20 wt. % water for the baseline sample, it was found that the overall energy demand appeared to be lower than for the dried sample, perhaps due to the more efficient absorption of microwave energy.
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Various technical and economic aspects relating to the briquetting of fine coal with sawdust have been evaluated with the results for two segments of that study presented here: binder and briquetting-parameter evaluations. Approximately 50 potential binder formulations were subjected to a series of screening evaluations to identify three formulations that were the most cost effective for briquetting fine coal with sawdust. Two of the binders, guar gum and wheat starch, were selected as most suitable for the pulverized coal market while the third formulation, lignosulfonate/lime, was targeted for the stoker market. Following binder selection, a number of briquetting parameters including binder and sawdust concentration, sawdust type, briquetting pressure and dwell time, coal and sawdust particle size, clay content, moisture content, and cure temperature and cure time were evaluated. Briquetting pressure and dwell time have the least impact while binder and sawdust concentrations, sawdust type, and curing conditions exerted the greatest influence on briquette quality.
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In this study, we used a commercial pilot-scale pyrolysis reactor system to produce combustible gas and biochar at 620 °C from three sources (chicken litter, swine solids, mixture of swine solids with rye grass). Pyrolysis of swine solids produced gas with the greatest higher heating value (HHV) followed by the mixture of swine solids with rye grass and chicken litter. Relatively high S-containing gases were produced; dimethyl sulfide and methyl mercaptan concentrations were higher than the OSHA PEL limits. Biochar yield ranged from 43 to 49% based on dry weight with about 53% of carbon recovery. Whereas the HHV of the chicken litter biochar was slightly below that of low rank coals, swine-based biochars had HHVs between high and low rank coals. Approximately 50% of the feedstock energy was retained in biochar and 25% in produced gases. Manure biochars contained higher concentrations of P and K than that of original manure feedstocks. Consequently, these could be used as a low-grade fertilizer to improve soil fertility and crop yields. Extremely high energy (232.3 MJ/kg) was required to make 1 kg of biochar from wet swine manure with 97% MC. However, dewatering of the wet swine manure to 75% MC substantially reduced the external energy requirement by 19 folds. Mixing of dried biomass such as rye grass with the dewatered swine solids almost eliminated the need for external energy. If one can copyrolyze wet animal wastes with additional feedstock that are drier and more energy dense than rye grass such as waste plastic pellets, it may be possible to produce both valuable biochar and extra power.
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Abstract The energy problems of the developing world are both serious and widespread. Lack of access to sufficient and sustainable supplies of energy affects as much as 90% of the population of many developing countries. Some 2 billion people are without electricity; a similar number remain dependent on fuels such as animal dung, crop residues, wood, and charcoal to cook their daily meals. Without efficient, clean energy, people are undermined in their efforts to engage effectively in productive activities or to improve their quality of life. Developing countries are facing two crucial-and related-problems in the energy sector. The first is the widespread inefficient production and use of traditional energy sources, such as fuelwood and agricultural residues, which pose economic, environmental, and health threats. The second is the highly uneven distribution and use of modern energy sources, such as electricity, petroleum products, and liquefied or compressed natural gas, which pose important issues of economics, equity, and quality of life. To address these problems, this paper evaluates some successful programs and recommends that governments support market-oriented approaches that make the energy market equally accessible and attractive to local investors, communities, and consumers. Such approaches ideally improve access to energy for rural and poor people by revising energy pricing and by making the first costs of the transition to modern and more sustainable uses of energy more affordable.
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While pyrolysis of livestock manures generates nutrient-rich biochars with potential agronomic uses, studies are needed to clarify biochar properties across manure varieties under similar controlled conditions. This paper reports selected physicochemical results for five manure-based biochars pyrolyzed at 350 and 700°C: swine separated-solids; paved-feedlot manure; dairy manure; poultry litter; and turkey litter. Elemental and FTIR analyses of these alkaline biochars demonstrated variations and similarities in physicochemical characteristics. The FTIR spectra were similar for (1) turkey and poultry and (2) feedlot and dairy, but were distinct for swine biochars. Dairy biochars contained the greatest volatile matter, C, and energy content and lowest ash, N, and S contents. Swine biochars had the greatest P, N, and S contents alongside the lowest pH and EC values. Poultry litter biochars exhibited the greatest EC values. With the greatest ash contents, turkey litter biochars had the greatest biochar mass recoveries, whereas feedlot biochars demonstrated the lowest.
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Several torrefaction experiments using wood briquettes are reported in this paper. The torrefied briquettes weight yield lies between 43 and 94 %, and energy yields ranged from 50 to 97 % depending on the operating parameters. After torrefaction the briquettes showed an increase of approximately 15 % in heating value, and a decrease of approximately 73 % in equilibrium moisture. It was shown that torrefied briquettes achieved hydrophobic character and remained unaffected when immersed in water. This research also provides information on proximate and elemental analysis, showing that temperature has more influence than residence time. The aforementioned data indicate that torrefaction is a feasible alternative to improve energy properties of ordinary briquettes and prevent moisture absorption during storage.
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Direct research on gut microbiota for understanding its role as 'an important organ' in human individuals is difficult owing to its vast diversity and host specificity as well as ethical concerns. Transplantation of human gut microbiota into surrogate hosts can significantly facilitate the research of human gut ecology, metabolism and immunity but rodents-based model provides results with low relevance to humans. A new human flora-associated (HFA) piglet model was hereby established taking advantage of the high similarity between pigs and humans with respect to the anatomy, physiology and metabolism of the digestive system. Piglets were delivered via cesarean section into a SPF-level barrier system and were inoculated orally with a whole fecal suspension from one healthy 10-year-old boy. The establishment and composition of the intestinal microbiota of the HFA piglets were analyzed and compared with that of the human donor using enterobacterial repetitive intergenic consensus sequence-PCR fingerprinting-based community DNA hybridization, group-specific PCR-temperature gradient gel electrophoresis and real-time PCR. Molecular profiling demonstrated that transplantation of gut microbiota from a human to germfree piglets produced a donor-like microbial community with minimal individual variation. And the microbial succession with aging of those ex-germfree piglets was also similar to that observed in humans. This HFA model provides a significantly improved system for research on gut ecology in human metabolism, nutrition and drug discovery.
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Handling and processing human feces in space habitats is a major concern and needs to be addressed for the Crew Exploration Vehicle (CEV) as well as for future exploration activities. In order to ensure crew health and safety, feces should either be isolated in a dried form to prevent microbial activity, or be processed to yield a non-biohazardous product using a reliable technology. During laboratory testing of new feces processing technologies, use of "real" feces can impede progress due to practical issues such as safety and handling thereby limiting experimental investigations. The availability of a non-hazardous simulant or analogue of feces can overcome this limitation. Use of a simulant can speed up research and ensure a safe laboratory environment. At Ames Research Center, we have undertaken the task of developing human fecal simulants. In field investigations, human feces show wide variations in their chemical/physical composition. However, under controlled experimental conditions using healthy adults (e.g. astronauts) fed a standard diet, the variations are likely to be minimal and within statistically acceptable levels. We have prepared a number of simulants using organic chemicals, soy paste ("Miso") and other materials - particularly those capable of representing the water-holding capacity (WHC) of feces. The chemical composition of this simulant was a better approximation to human feces than previously used analogues. Rheological studies of the simulant are planned to ensure that it simulates fecal material. The emphasis on rheology and WHC is based on the assumption that in space habitats feces will be compacted to reduce volume and/or the water will be removed to safen the fecal waste.
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Char samples were obtained from slow pyrolysis of hazelnut and peanut shells at different temperatures (623 K, 873 K, and 1123 K). Composition, heating values, and surface properties of the charcoals were analyzed to explore their potentiality as bio-fuels and/or for further conversion into activated carbons. The chars generated from both wastes at 873 K exhibited good properties for these purposes, although the hazelnut shell-derived char showed a relatively greater potential. Furthermore, kinetics of the shell's pyrolysis over the temperature range 300 to 1200 K was characterized from nonisothermal thermogravimetric measurements by applying a model that assumes a steadily increasing variation in the activation energy with the process course. It allowed for a satisfactory description of kinetic data for the pyrolysis of hazelnut and peanut shells over the whole range of temperatures examined. Differences in the estimated kinetic parameters characterizing the wastes were found.
Article
Batch isotherm experiments were conducted with chars to study adsorption of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Chars generated from corncobs, bamboo and wood chips in a laboratory pyrolyzer at 400-700 °C were compared with traditional kiln charcoals collected from villages in S/SE Asia and with activated carbons (ACs). 2,4-D uptake by laboratory chars obtained from bamboo and wood chips after 14 h of pyrolysis at 700 °C, from wood chips after 96 h of pyrolysis at 600 °C, and one of the field-collected chars (basudha) was comparable to ACs. H:C and O:C ratios declined with pyrolysis temperature and duration while surface area increased to >500 m(2)/g. Increasing pyrolysis intensity by increasing temperature and/or duration of heating was found to positively influence adsorption capacity yield (mg2,4-D/gfeedstock) over the range of conditions studied. Economic analysis showed that high temperature chars can be a cost-effective alternative to ACs for water treatment applications.
Article
Recent au fost cercetate mai multe tipuri de biomasă, care pot produce energie în vederea înlocuirii combustibililor fosili. Această lucrare prezintă o abordare în vederea optimizării producţiei de bio-cocs din piroliza prin modificarea parametrilor de proces. Materialul analizat a fost rumeguşul de cireş. Experimentele s-au efectuat prin piroliza la temperaturi între 450 ºC şi 800 ºC. Studiul experimental s-a bazat pe influenţa temeraturii, timpului de staţionare şi a ratei de încălzire asupra producţiei de bio-cocs şi asupra determinării puterii calorifice superioare a cocsului. Recently much research has been investigated on identifying suitable biomass species, which can provide high-energy outputs, to replace conventional fossil fuels. This paper reports an approach for increasing the yield of bio-char production from pyrolysis with respect to process conditions. The analyzed material was cherry sawdust. The experiments were conducted for pyrolysis temperature between 450ºC and 800ºC. The experimental study focused on the influence of pyrolysis temperature, residence time or heating rate on the bio-char yield and on determination of the HHV of the pyrolysis char.
Article
Four physical properties have been identified as being of greatest value when developing or evaluating fuel briquette formulations or processes. They are resistances to crushing, impact, abrasion and water penetration. Arbitrary tests for these properties have evolved in this laboratory during a decade of investigations of binders and formulations for briquetting coal fines and the like. The simple test methods are described and some typical results are given.Tests of several types of commercial and pilot process fuel briquettes have been used to set realistic target values for these four physical properties. In the process development stages, it is suggested that the tests should relate to the briquette material, rather than the briquette as an entity, and that this can be achieved by transforming the raw data into various indices. These would allow intra-laboratory or inter-laboratory comparisons of briquette formulations. This approach is illustrated by presenting results for compressive strength, impact resistance and abrasion resistance. The same could apply to water resistance and some suggestions are discussed.The needs of research and development and of production in respect of briquette testing are seen as different, but complementary. It is hoped that the paper will stimulate researchers and producers alike to work towards the adoption of codes of standard practice in briquette testing.
Article
We present a high temperature heat treatment study of CVD-grown graphene nanoribbons annealed up to 2800°C, demonstrating a progressive annihilation of lattice defects as the heat treatment temperature is raised. Starting at 1500°C, single and multiple loop formation were observed on the ribbons edges as the temperature was increased. The structural changes of the samples are documented by X-ray diffraction, Raman spectroscopy, TGA, SEM, and HRTEM. This work indicates that nanoribbon annealing eventually leads to defect-free samples, through graphitization and edge loop formation. The annealed material exhibits structural differences that could be tailored for a variety of specific applications.
Article
Selected values of the heats of combustion and heats of formation of 719 organic compounds are reported here. The data tabulated pertain to compounds containing the elements carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur (CHNOPS). The information is arranged according to classes of compounds and within each class, compounds are arranged by empirical formula. The general classes covered are: hydrocarbons, alcohols, phenols, polyols, ethers, aldehydes, ketones, acids, acid anhydrides, esters, steroids, lactones, carbohydrates, heterocyclic oxygen compounds, amines, amides, urea derivatives, guanidine derivatives, amino acids, peptides, alkaloids, heterocyclic nitrogen compounds, porphyrins, organic sulfur compounds, and organic phosphorus compounds. When a selection was made from among several investigators, commentary is provided to indicate the choice, and usually some relevant data. The number of references cited is 596. An alphabetical compound index is provided which gives the name, page number, empirical formula, and the Wiswesser Line Notation (WLN), for each compound.
Article
Char samples were obtained from slow pyrolysis of hazelnut and peanut shells at different temperatures (623 K, 873 K, and 1123 K). Composition, heating values, and surface properties of the charcoals were analyzed to explore their potentiality as bio-fuels and/or for further conversion into activated carbons. The chars generated from both wastes at 873 K exhibited good properties for these purposes, although the hazelnut shell-derived char showed a relatively greater potential. Furthermore, kinetics of the shell’s pyrolysis over the temperature range 300 to 1200 K was characterized from nonisothermal thermogravimetric measurements by applying a model that assumes a steadily increasing variation in the activation energy with the process course. It allowed for a satisfactory description of kinetic data for the pyrolysis of hazelnut and peanut shells over the whole range of temperatures examined. Differences in the estimated kinetic parameters characterizing the wastes were found.
Article
Progress towards the sanitation component of Millennium Development Goal (MDG) Target 7c was re-assessed to account for the need to protect communities and the wider population from exposure to human excreta. We classified connections to sewerage as 'improved sanitation' only if the sewage was treated before discharge to the environment. Sewerage connection data was available for 167 countries in 2010; of these, 77 had published data on sewage treatment prevalence. We developed an empirical model to estimate sewage treatment prevalence for 47 additional countries. We estimate that in 2010, 40% of the global population (2.8 billion people) used improved sanitation, as opposed to the estimate of 62% (4.3 billion people) from the WHO/UNICEF Joint Monitoring Programme (JMP), and that 4.1 billion people lacked access to an improved sanitation facility. Re-defining sewerage-without-treatment as 'unimproved sanitation' in MDG monitoring would raise the 1990 baseline population using unimproved sanitation from 53% to 64% and the corresponding 2015 target from 27% to 32%. At the current rate of progress, we estimate a shortfall of 28 percentage points (1.9 billion people) in 2010 and a projected 27 percentage point shortfall in 2015.
Book
Modernized biomass gasification for power generation has attracted increasing interests as an attempt to reduce our reliance on fossil fuel. In fact, over the past couple of years, a lot of RD&D has gone into overcoming the technical hurdles of biomass gasification mainly producing clean gas which is free of particulates and tars bed agglomeration and biomass feeding/handling. Biomass Gasification Design Handbook offers engineers and scientist a "hands on" reference for understanding and successfully overcoming these hurdles. In this book, readers find a versatile resource that not only explains the basic principles of energy conversion and biomass conversion systems but also provides valuable insight into the design of biomass gasifiers. Thorough in his coverage, the author provides many worked out design problems, step-by-step design procedures, and real data on commercially operating systems. In addition, the book contains four valuable appendices that eliminate the need to search for essential information. Includes step-by-step design procedures and case studies for Biomass Gasification Provides worked process flow diagrams for gasifier design. Covers integration with other technologies (e.g. gas turbine, engine, fuel cells).
Article
In this work, biomass samples were converted to char, liquid, and gaseous products using pyrolysis process at different temperatures. The amount of char from pyrolysis of the biomass samples decreases with increasing the pyrolysis temperature. The highest liquid yields were obtained from the biomass samples between 650 and 800 K. The yield of char and the chemical composition of char can be calculated as functions of the pyrolysis temperature. There have been numerous other mathematical equations, which were created based on data from the physical or chemical compositions, proximate or ultimate analysis of the biomass fuels. The char components and higher heating values (HHVs) of biomass fuels were correlated with pyrolysis temperatures. There were highly significant linear correlation between the pyrolysis temperature of the biomass fuel and the fixed carbon content and HHV of char. The fixed carbon (FC) and HHV (MJ/kg) of the char from biomass as a linear function of pyrolysis temperature (T, K) was calculated using the following equations: For Eqs. (a) and (b) the correlation coefficients (r) were 0.9809 and 0.9983, respectively.
Article
A sustainable energy system includes energy efficiency, energy reliability, energy flexibility, fuel poverty, and environmental impacts. A sustainable biofuel has two favorable properties which are availability from renewable raw material, and its lower negative environmental impact than that of fossil fuels. Charcoal is produced by slow heating wood (carbonization) in airtight ovens or retorts, in chambers with various gases, or in kilns supplied with limited and controlled amounts of air. The charcoal yield decreased gradually from 42.6 to 30.7% for the hazelnut shell and from 35.6 to 22.7% for the beech wood with an increase of temperature from 550 to 1,150 K while the charcoal yield from the lignin content decreased sharply from 42.5 to 21.7% until it was at 850 K during the carbonization procedures. The charcoal yield decreases as the temperature increases. The ignition temperature of charcoal increases as the carbonization temperature increases. The charcoal briquettes that are sold on the commercial market are typically made from a binder and filler.
Article
Char is ubiquitous in the environment and contributes significantly to the inert soil organic carbon pool. Its roles as a carbon sink and a strong sorbent of organic contaminants have come under increasing attention. However, quantifying these roles is difficult because properties such as degradability and sorption affinity vary greatly amongst chars, especially those produced at different temperatures. Here we describe a simple method for gauging the degree of aromatic condensation of chars, a molecular-scale property that affects both their degradability and sorption affinity. The method involves adding 13C6 benzene directly to char. The 13C nuclear magnetic resonance (NMR) chemical shift of the sorbed benzene is affected by diamagnetic ring currents in the fused aromatic structures in the char. These ring currents increase in magnitude with increasing extent of aromatic condensation. Seventeen heat-treated materials were analysed in this way. Our results confirm that aromatic condensation increases with increasing heat treatment temperature (HTT) and that activated chars contain the most highly condensed aromatic structures, but also show the importance of starting material and heat treatment time on aromatic condensation. We also show for four of the materials that the ring current effect on chemical shift was similar for other 13C-labelled molecules, including MeOH, CH3CN and toluene.
Article
Biomass as a fuel suffers from its bulky, fibrous, high moisture content and low-energy-density nature, leading to key issues including high transport cost and poor biomass grindability. This study investigates the possibility to pretreat biomass to produce biochar as a solid biofuel to address these issues. Biochars were produced from the pyrolysis of centimeter-sized particles of Western Australia (WA) mallee wood in a fixed-bed reactor at 300 to 500 °C and a heating rate of 10 °C/min. The data show that, at pyrolysis temperatures ≥320 °C, biochar as a fuel has similar fuel H/C and O/C ratios compared to Collie coal that is the only coal being mined in WA. Converting biomass to biochar leads to a substantial increase in fuel mass energy density from 10 GJ/ton of green biomass to 28 GJ/ton of biochars prepared from pyrolysis at 320 °C, in comparison to 26 GJ/ton for Collie coal. However, there is little improvement in fuel volumetric energy density, which is around 7−9 GJ/m3 in comparison to 17 GJ/m3 of Collie coal. Biochars are still bulky and grinding is required for volumetric energy densification. Biochar grindability experiments show that the fuel grindability increases drastically even at pyrolysis temperature as low as 300 °C. Further increase in pyrolysis temperature to 500 °C leads to only a small increase in biochar grindability. Under the grinding conditions, a significant size reduction (34−66% cumulative volumetric size below 75 μm) for biochars can be achieved after 4 minutes grinding (in comparison to only 19% for biomass after 15 minutes grinding), leading to a significant increase in volumetric energy density (e.g., from 8 to 19 GJ/m3 for biochar prepared from pyrolysis at 400 °C). Whereas grinding raw biomass typically results in large and fibrous particles, grinding biochars produces short and round particles. The results in this article indicate that biochar has desired fuel properties and potentially a good solution to address the key issues including high transport cost and poor grindability associated with the direct use of biomass as a fuel.
Article
Two types of swine-manure chars, hydrothermally produced hydrochar and slow-pyrolysis pyrochar, and their raw swine-manure solid were characterized using advanced solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. In comparison to raw swine-manure solid, both hydrochars and pyrochar displayed significantly different structural features, with lower alkyl carbons, NCH, OCH3, O-alkyl, and COO/N−C═O groups but higher aromatic/olefinic and aromatic C−O groups. The chemical structures of four hydrochars varied with different processing conditions. In comparison to the hydrochar with only water wash (HTC-swine W), washing hydrochar with acetone (HTC-swine A) removed the soluble intermediates deposited on the hydrochar, as shown by the decrease of O-alkyl (primarily carbohydrates), corresponding increase of aromatic/olefinic carbons and complete removal of OCH3 groups. With citric acid prewash and acetone wash (HTC-AW-swine A), aromatic C−O and aromatics/olefinics were increased and alkyls were decreased, with O-alkyls totally removed in comparison to just acetone wash (HTC-swine A). Citric acid catalysis and acetone wash (HTC-AC-swine A) increased aromatic C−O and non-protonated aromatics/olefinics, decreased alkyls further, and reduced protonated aromatics/olefinics compared to citric acid prewash and acetone wash (HTC-AW-swine A). The ratios of non-protonated to protonated aromatic/olefinic carbons for HTC-swine W, HTC-swine A, and HTC-AW-swine A hydrochars were quite similar but enhanced for HTC-AC-swine A hydrochar. Obviously, citric acid catalysis and acetone wash (HTC-AC-swine A) provided deeper carbonization than other hydrothermal processes. Hydrothermal carbonization (HTC) processes were associated with the hydrolysis and subsequent decomposition of major biopolymer components in swine manure. The increase of aromaticity during HTC was likely due to condensation polymerization of the intermediates from the degradation of carbohydrates. Pyrochar produced from slow pyrolysis was structurally different from HTC hydrochars. The dominant component of pyrochar was aromatics, whereas that of hydrochars was alkyl moieties. The aromatic cluster size of pyrochar was larger than those of hydrochars. Slow pyrolysis at 620 °C provided deeper carbonization than HTC processes.
Article
Coal briquettes and the binders were tested from the view of resistivity to transportation, loading and storage by measuring the abrasion index and strength to crushing. The binders used in coal briquetting also affect the combustion properties of the coal. Combustion properties of the Tuncbilek lignite and different binders were analysed by thermogravimetric (TG/DTG) methods. Molasses, carboxyl methylcellulose (CMC), sulphide liquor, heavy crude oil, sodium silicate, cornstarch, lime, peridur, and bentonite, cement poly(vinyl acetate) were used as binders. It was observed that molasses and CMC decreased the residue content at the end of the combustion period, whereas, heavy crude oil, sulphide liquor and corn starch increased the calorific values of the samples.
Article
Diplicate groups of rainbow trout were fed low-protein (38%) diets containing high levels (38%) of five different carbohydrate sources (raw starch, extruded corn, extruded wheat, extruded corn starch or extruded wheat starch). A modified pair-feeding method was used to allow equal intakes of protein and of digestible energy by each group of fish. Growth parameters were followed over a period of 18 weeks; the digestibility of the diets, nitrogen and energy balances, and the respiratory and ammonia quotients of fish fed the different diets were determined. To study the long-term effects of dietary carbohydrates, plasma glucose profile and its control by bovine insulin was followed in fish fed over 30 weeks with selected test diets. The results show that inclusion of extruded cereals or extruded starch improves availability of dietary energy. High levels of carbohydrates to not adversely affect overall growth or nutrient retention efficiencies. Long-term feeding with carbohydrate-rich d diets does not confer on trout any adaptive capacity to regulate postprandial glycemia levels. Respirometric measurements appear to provide interesting data on the metabolic utilization of body substrates.
Article
Fuelwood shortages are widespread throughout the developing world. One option to alleviate the situation is to substitute indigenously produced coal briquettes. This paper reviews carbonizing and briquetting technologies that convert coal to a smokeless, strong, and low-emissions bbriquette for domestic or commercial application. Cost studies are presented indicating the briquettes are competitive in some countries. We examine experiences with briquettes in the Third World and identify 36 countries where both coal and fuelwood shortages exist, which are prerequisites for the technology Finally, we describe the necessary resource, technological, market, and government policy assessments for analysing a country's coal briquetting prospects.
Article
In Arizona, cotton (Gossypium) plant residue left in the field following harvest must be buried to prevent it from serving as an overwintering site for insects such as the pink bollworm. Most tillage operations employed to incorporate the residue into the soil are energy intensive and often degrade soil structure. Trials showed that cotton plant residue could be incorporated with pecan shells to produce commercially acceptable briquettes. Pecan shell briquettes containing cotton residue rather than waste paper were slightly less durable, when made using equivalent weight mixtures and moisture contents. Proximate and ultimate analyses showed the only difference among briquette samples to be a higher ash content in those made using cotton plant residue. Briquettes made with paper demonstrated longer flame out time, and lower ash percentage, compared to those made with cotton plant residue.
Article
This article deals with slow pyrolysis of four shells such as hazelnut, walnut, almond and sunflower at the range of temperature 500–1200 K in a cylindrical reactor batch reactor. The aim of this work was to experimentally investigate how the temperature affects char, liquid and gaseous product yields from different shells via pyrolysis. The amount of char from pyrolysis of the shell samples decreases with increasing the pyrolysis temperature. The highest liquid yields were obtained from the samples between 650 and 800 K. The yield and the chemical composition of char can be calculated as functions of the pyrolysis temperature. The char components and higher heating values (HHVs) of shell fuels were correlated with pyrolysis temperatures. There were highly significant linear correlation between the pyrolysis temperature of the fuel and the fixed carbon content and HHV of char.