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Phases’ characteristics of poultry litter hydrothermal carbonization under a range of process parameters
... Energy balance of HTC at different temperatures for duration of 60 min and for pyrolysis at 400 • C for duration of 60 min was performed as explained in the literature [41,42]. Considering the water content (65%) of the received TPOMW and the requirement that different water contents of feedstock are used in both processes, the energy input and output values of both processes were calculated according to the dry matter content. ...
... where H w,100 is the enthalpy of water at 100 • C, ΔH vap is the enthalpy of vaporization of water at 100 • C and T p is the final temperature of the pyrolysis process [30]. For both two process, the energy required to heat the reactor and to keep it at a constant temperature was not considered, since these values vary according to the reactor type and procedures applied during process, such as recovery of waste heats, etc. [41]. ...
... However, we would like to point out that the energy required to heat the reactor itself and heat losses during the process were ignored. Mau et al. also claimed that the heat losses and the energy required to heat the reactor can be minimized with a proper choice of reactor design and HTC procedure [41]. On the other hand, the Q input /Q output ratio in pyrolysis process was found to be higher due to huge amount of energy required for drying. ...
... The energy required to heat the reactor and keep it at constant temperature was not factored into the energy input (Q in ) calculation. This is because the energy input in this case is a process development perspective that varies with reactor design and operating procedures (Mau et al., 2016). Q in was estimated by adding the energy necessary to heat the dry solids and the water content during HTC, assuming the wet substrate is a non-reactive mixture of water and dry solids, according to equation (6). ...
... Terms such as the solid load (X 3 ), the interaction between reaction temperature and solid load (X 1 X 3 ), and quadratic effect of solid load (X 3 2 ) had p-values higher than 0.05, which indicates that these terms had no significant effect on the calorific value, i.e. they are not significant for optimisation of the calorific value of the hydrochar. The observed trend on the non-significant influence of the solid load on the hydrochar yield and calorific value is in agreement with Mau et al. (2016). To further improve the reliability of the model, a backward model reduction was performed for p-values coded at α = 0.1 to consider only the significant terms. ...
... Under this condition, in addition to accounting for factors such as the energy required to heat the system and heat losses, the process becomes energy-inefficient and unsustainable. A similar trend was observed by Mau et al. (2016) for carbonisation at a solid-to-water ratio of 1:10 and 250 • C, which required between 84 and 103% of the energy input from poultry litter-derived hydrochar combustion. Except for this case, the energy demand for HTC ranged from 41.66% to 88.56%, which is considerably high compared to the 17-27% energy requirement reported by Spitzer et al. (2018) for HTC of human excreta, and the 30.3-37.5% energy demand to treat spent coffee ground wastes at a solid load of 0.1 (Afolabi et al., 2020). ...
Current management of solid waste from pulp and paper activities represents an environmental and economic burden worldwide due to pollution emissions. This study investigates the potential of hydrothermal carbonisation (HTC) treatment as a sustainable alternative for producing cleaner and energy-dense solid fuel from paper mill sludge. The effect of process parameters (temperature, reaction time and solid load) on hydrochar fuel formation from paper sludge was evaluated and, for the first time, the paper sludge-derived hydrochar was optimised to maximise the mass yield and calorific value using response surface methodology (RSM). The physicochemical characteristics, thermal fuel behaviour, energy recycling efficiency and electricity generation potential were assessed by proximate and ultimate analysis, thermogravimetry, bomb calorimeter, scanning electron microscopy and process energy assessment. Results showed that hydrochar fuel formation and properties were mainly influenced by the process temperature and residence time, and governed by dehydration and decarboxylation reactions which reduced the atomic H/C and O/C ratios by 35.5% and 64%, respectively. The produced hydrochars presented low sulphur, nitrogen and ash content with a maximum calorific value (HHV) of 22.9 MJ/kg, equivalent to the HHV of coal for commercial utility in South Africa. The HHV of the hydrochar corresponded to a 49.80% increase over the HHV of the initial feedstock. The optimum operating conditions were 231 ± 1 ◦C and 1.99 h for a hydrochar yield of 74.4% and calorific value of 18.5 MJ/kg. The energy assessment showed that up to 58.34% of the energy produced by hydrochar fuel combustion may be recycled as heat or power, while the remaining 41.66% of the combustion energy could be utilised to sustain the HTC treatment of paper sludge. The substantial water demand was concluded to be a drawback. Thus, water recirculation and the potential to catalyse the HTC reactions to increase overall process efficiency will constitute a future study to make the process more environmentally friendly for industrial-scale application.
... HTC is a thermochemical process in which saturated water and vapor pressure are utilized to convert waste biomass into carbon-rich products . HTC is typically performed in temperature ranges between 150-350 °C and autogenous pressure (Mau et al., 2016). Hence, the water content stays in the aqueous phase during the HTC reaction, but its density and dielectric constant decrease. ...
... In addition to the solid residues, liquid and gas products are also formed during HTC. The liquid products obtained from the HTC of agricultural wastes (Benavente et al., 2015), sewage and dairy sludge (Danso-Boateng et al., 2015; Atallah et al., 2020), human excreta (Spitzer et al., 2018), and poultry litter (Mau et al., 2016) have been considered for different purposes, such as the production of nanostructured and adsorbent materials for soil amendment and bioenergy production. The characteristics of HTC products under different ranges of conditions have been extensively studied (Mau et al., 2016;Atallah et al., 2020). ...
... The liquid products obtained from the HTC of agricultural wastes (Benavente et al., 2015), sewage and dairy sludge (Danso-Boateng et al., 2015; Atallah et al., 2020), human excreta (Spitzer et al., 2018), and poultry litter (Mau et al., 2016) have been considered for different purposes, such as the production of nanostructured and adsorbent materials for soil amendment and bioenergy production. The characteristics of HTC products under different ranges of conditions have been extensively studied (Mau et al., 2016;Atallah et al., 2020). ...
This work evaluates the effect of hydrothermal carbonization (HTC) as a pretreatment and post-treatment technique to anaerobic digestion (AD) of dairy sludge. HTC's effect on AD was evaluated based on energy recovery, nutrient transformation, and hydrochar utilization. The first approach was executed by performing HTC under a range of temperatures before mesophilic AD. HTC optimal pretreatment temperature was 210 °C for 30 min residence time. HTC pretreatment significantly increased the methane yield potential by 192%, the chemical oxygen demand removal by 18%, and the sludge biodegradability during AD by 30%. On the other hand, the application of HTC after AD (post-treatment) increased the total energy production, i.e., in addition to methane, a hydrochar with a caloric value of 10.2 MJ/kg was also obtained. Moreover, HTC post-treatment improved the steam gasification performance of the AD digestate. From the fertilizer quality point of view, HTC implementation generally boosted the concentrations of macro, micro, and secondary nutrients, suggesting its suitability for use as a liquid fertilizer. Overall, the findings of the present study indicate that if bioenergy production were the main target, HTC post-treatment following AD would lead to the most promising outcomes.
... One reactor was equipped with a temperature probe to monitor the temperature inside the reactor. In all experiments, 12 g of dry waste feedstock and 36 mL of liquid (either distilled water or whey) were loaded into each reactor, maintaining a constant solids-mass-to-liquid ratio of 1:3 following a previous research by Mau et al. (2016). Whey solid content of 23 g/L was considered in the ratio. ...
... An energy balance was conducted to evaluate the feasibility of using HTC of dairy waste as a single treatment and as a co-treatment to AD, and to identify the conditions for enhancing the potential recovery of energy and nutrients. The energy balance was determined by calculating the energy required for AD and/or HTC (E input ) and the energy produced by the methane yield and/or hydrochar combustion (E output ) (Marin-Batista et al., 2020;Mau et al., 2016). The energy input for the AD and HTC treatments was determined based on the energy required to heat water, and feedstock in a closed batch system (Aragón-Briceño et al., 2021;Berge et al., 2011;Mau et al., 2016), and energy used for drying the produced wet-hydrochar (Benavente et al., 2015;Lucian and Fiori, 2017). ...
... The energy balance was determined by calculating the energy required for AD and/or HTC (E input ) and the energy produced by the methane yield and/or hydrochar combustion (E output ) (Marin-Batista et al., 2020;Mau et al., 2016). The energy input for the AD and HTC treatments was determined based on the energy required to heat water, and feedstock in a closed batch system (Aragón-Briceño et al., 2021;Berge et al., 2011;Mau et al., 2016), and energy used for drying the produced wet-hydrochar (Benavente et al., 2015;Lucian and Fiori, 2017). The focus of this study was to compare the energy balance using HTC alone and AD followed by HTC, and therefore, the following process assumptions were considered for the energy input calculations: (1) wet-manure was dehydrated at open-air and the initial temperature inside the reactor system was assumed to be 25 • C (i.e., ambient temperature); (2) sample weight loss during the digestion reaction was neglected due to its minimal impact on the balance results; (3) heat loss from the reactor (Aragón-Briceño et al., 2021) and heat transfer in porous media were neglected, as it differs according to the setup and can be minimized by optimizing the design and operational parameters; (4) heat released and absorbed by chemical reactions (Heidari et al., 2021), was neglected since both AD and HTC are net exothermic processes, which rely on external energy input to operate at ideal temperatures. ...
Hydrothermal carbonization (HTC) of raw and anaerobically digested (AD) manure with either water or whey was studied, with the goal of recovering energy and nutrients. Specifically, the impacts of HTC reaction temperature (180–240 °C), solid feedstock, and type of liquid on hydrochar quality and aqueous phase properties were tested. Of the hydrochars produced, the calorific value of whey-based hydrochar was the highest, (19.4 and 16.0 MJ/kg for manure and digestate, respectively). Overall, the net energy gain was higher for HTC of manure with whey (7.4–8.3 MJ/kg dry feedstock) and water (4.4–5.1 MJ/kg) compared to the combined AD-HTC process with whey (4.4–5.3 MJ/kg) and water (2.3–2.9 MJ/kg). Digestate-derived hydrochar contained up to 1.8% P, higher than manure-derived hydrochar (≤1.5%). Using whey as a liquid for HTC increased the aqueous-phase N-P-K concentrations up to 3,200, 410, and 7,900 mg/L, respectively, suggesting its potential use as a liquid fertilizer.
... Hydrothermal carbonization (HTC) can produce value-added products such as hydrochars by using either wet or dry feedstock in a water medium subjected to sub-critical temperatures and pressures (Mau et al., 2016;Wilk et al., 2019). Relative to pyrolysis and gasification for producing biochars, notable benefits of HTC are: (1) utilization of both wet and dry feedstocks, (2) air pollution is minimized because the generated syngas is dissolved in the water medium, (3) a higher rate of carbon (C) recovery for a given feedstock, and (4) the process is operated at lower carbonization temperatures with a lower energy cost (Fang et al., 2018;Kang et al., 2012;Mau et al., 2016). ...
... Hydrothermal carbonization (HTC) can produce value-added products such as hydrochars by using either wet or dry feedstock in a water medium subjected to sub-critical temperatures and pressures (Mau et al., 2016;Wilk et al., 2019). Relative to pyrolysis and gasification for producing biochars, notable benefits of HTC are: (1) utilization of both wet and dry feedstocks, (2) air pollution is minimized because the generated syngas is dissolved in the water medium, (3) a higher rate of carbon (C) recovery for a given feedstock, and (4) the process is operated at lower carbonization temperatures with a lower energy cost (Fang et al., 2018;Kang et al., 2012;Mau et al., 2016). During HTC, complex chemical reactions occur (Li and Jiang, 2017;Wilk et al., 2019); the cellulose and hemicellulose contained in biomass feedstocks are solubilized in the water medium leaving a lignin-rich solid-phase known as hydrochar, while other simultaneous reactions such as hydrolysis, dehydration, decarboxylation, aromatization and recondensation produce a nutrientrich liquid-phase (Fang et al., 2018;Wilk et al., 2019;Xiao et al., 2012). ...
... Non-lignocellulosic biomass is dominated by proteins, lipids, saccharides, inorganics with a fraction of lignin, cellulose, and hemicellulose, while lignocellulosic biomass is mainly composed of aromatic (lignin) and carbohydrate (cellulose and hemicellulose) polymers (Li and Jiang, 2017). Non-lignocellulosic feedstocks, such as animal manures and human feces, have been utilized for hydrochar production, although no comparative study with lignocellulosic biomass has been conducted (Mau et al., 2016;Wüst et al., 2019). Since the methodology for HTC is evolving, and given that non-lignocellulosic biomass is globally abundant (Li and Jiang, 2017), more comparative studies conducted under different process conditions are needed to validate whether the HTC process produces less favorable hydrochar from non-lignocellulosic biomass (Wilk et al., 2019). ...
The hydrothermal carbonization (HTC) process that converts wet/dry biomass to hydrochars (for use as solid fuels or adsorbents) needs to be optimized. We investigated the interactive effects of feedstock type and HTC temperature on chemical, fuel, and surface properties of hydrochars produced from lignocellulosic (canola straw, sawdust and wheat straw) and non-lignocellulosic feedstocks (manure pellet) at 180, 240 and 300 °C. Increased HTC temperature decreased hydrochar yield and surface functional group abundance, but increased hydrochar thermal stability due to increased devolatilization and carbonization. Hydrochar surface area ranged from 1.76 to 30.59 m² g⁻¹, much lower than those of commercially available activated carbon. Lignocellulosic and non-lignocellulosic feedstocks were distinctly affected by HTC temperature due to variable carbonization from ashing. Hydrochars produced from lignocellulosic biomass at 240 and 300 °C resembled high–volatile bituminous coal. Hydrochars should be designed for specific applications such as fuels by selecting specific feedstock types and carbonization conditions.
... This process is typically carried out at elevated temperatures (150 to 250 • C) and pressures (10 -50 bar) and suitable for the treatment of wet biowaste with up to 90% moisture content [2]. Under these operation conditions, HTC causes a decrease in the feedstock's O and H content through dehydration and decarboxylation reactions, which increase the C content and consequently the calorific value per unit mass of the hydrochar [5,6]. As can be seen, HTC does not require a drying process as the pre-treatment to wet biomass, e.g. ...
... > 0.3) [9]. The formation of organic acids and carbon dioxide from the carbonisation of cellulosic feedstock led to the reduction of pH from almost neutral to acidic in the aqueous phase [5]. The aqueous phase, as a nutrient rich product, has shown great potential for use as a fertiliser [10]. ...
... Several types of wet biomasses have been experimented for HTC, including poultry litter [11], lawn grass [12], microalgae [13], rice husk [14] and wheat straw digestate [15]. The yield and characteristics of the products depend on the process conditions [5,6,11,14,15], especially carbonisation temperature, reaction time and feedstock moisture content. Temperature has been found to be the most influencing parameter [5,6,11,14,15]. ...
In abattoir operation, paunch waste can present a major problem when flushed with water and discharged. Collected and processed separately, it provides a means of reusing organic carbon and nutrients. Hydrothermal carbonisation (HTC) is a means to process the waste that overcomes some problems of composting and anaerobic digestion. Experiments were conducted to investigate HTC of cattle paunch waste to hydrochar under different conditions. The fuel characteristics of hydrochar were tested for the potential in electricity generation and the nutrient concentrations of liquid were analysed for soil fertilization. The carbon content of paunch increased (∼15%) after HTC. It was also reflected in its increasing calorific value. The changes in the H/C and O/C ratios, analysed using the van Krevelen diagram, showed that the fuel properties of hydrochar improved noticeably after carbonisation. The TOC and TN concentrations in the liquid changed significantly with increasing temperature and time. With increasing moisture, the nutrient concentrations decreased, because of dilution effect. The liquid product contained significant levels of N, C and K; but may need suitable dilution before applying as a fertiliser. An energy balance showed that a fraction (<45%) of the hydrochar combustion energy was required to provide the input energy for HTC.
... Hydrochar was prepared following the methods described by Mau et al. (2016). The effect of production temperature was investigated since it has the greatest influence on hydrochar composition (Ghanim et al., 2016). ...
... The characteristics of the raw poultry litter and hydrochar produced at 180, 220 and 250 � C are presented in Table 1. In general, the characteristics of the hydrochar generated in this study were similar to those in previous studies on poultry litter HTC (Ghanim et al., 2016;Mau et al., 2016). This indicates that the hydrochar used in this study is representative of poultry litter hydrochar. ...
... This indicates that the hydrochar used in this study is representative of poultry litter hydrochar. As previously reported, hydrochar yield decreased significantly with temperature, while C content increased (Ghanim et al., 2016;Mau et al., 2016). The moisture content of the hydrochar following vacuum filtration from the aqueous phase decreased with increasing HTC treatment temperature, which is in agreement with the hydrochar's increased hydrophobicity . ...
The conversion of poultry litter to hydrochar has been proposed for stabilization of the soils and to eliminate pathogens. Still, research on the hydrochar's effect on soil properties as a function of production temperature, and its direct use with plants is limited in general and even less so on poultry litter. We characterized poultry litter hydrochar as an amendment for sandy soils in terms of changes to the soil's bulk density, porosity, water-retention capacity, and fertility. Soil bulk density, porosity and water-retention capacity were determined in a pneumatic tension plate system for sand with hydrochar-amendment rates of 0.5, 1 and 2%, and hydrochar-production temperature of 180, 220, and 250 � C. Soil fertility was assessed by growing lettuce seedlings in a randomized block design planter experiment, consisting of 16 blocks that were sampled every 10 days. The addition of poultry litter hydrochar resulted in decreased soil bulk density. Soil porosity increased with hydrochar generated at a temperature of up to 220 � C, and decreased with hydrochar generated at 250 � C. Soil water content increased as compared to unamended sand, but decreased with increasing hydrochar-production temperature, probably due to increasing hydrophobicity of the poultry litter hydrochar. The addition of hydrochar at concentrations of 0.5 and 1% resulted in improved plant growth despite an initial delay. While increased soil moisture due to increased soil water-retention capacity was confirmed, it did not seem to be responsible for the improved plant growth. It was also demonstrated for the first time that hydrochar decreases nitrate leaching from soils. Therefore, poultry litter-derived hydrochar seems to be an adequate amendment for sandy soils.
... Hydrochar was prepared following the methods described by Mau et al. (2016). The effect of production temperature was investigated since it has the greatest influence on hydrochar composition (Ghanim et al., 2016). ...
... The characteristics of the raw poultry litter and hydrochar produced at 180, 220 and 250 � C are presented in Table 1. In general, the characteristics of the hydrochar generated in this study were similar to those in previous studies on poultry litter HTC (Ghanim et al., 2016;Mau et al., 2016). This indicates that the hydrochar used in this study is representative of poultry litter hydrochar. ...
... This indicates that the hydrochar used in this study is representative of poultry litter hydrochar. As previously reported, hydrochar yield decreased significantly with temperature, while C content increased (Ghanim et al., 2016;Mau et al., 2016). The moisture content of the hydrochar following vacuum filtration from the aqueous phase decreased with increasing HTC treatment temperature, which is in agreement with the hydrochar's increased hydrophobicity . ...
The conversion of poultry litter to hydrochar has been proposed for stabilization of the soils and to eliminate pathogens. Still, research on the hydrochar's effect on soil properties as a function of production temperature, and its direct use with plants is limited in general and even less so on poultry litter. We characterized poultry litter hydrochar as an amendment for sandy soils in terms of changes to the soil's bulk density, porosity, water-retention capacity, and fertility. Soil bulk density, porosity and water-retention capacity were determined in a pneumatic tension plate system for sand with hydrochar-amendment rates of 0.5, 1 and 2%, and hydrochar-production temperature of 180, 220, and 250 � C. Soil fertility was assessed by growing lettuce seedlings in a randomized block design planter experiment, consisting of 16 blocks that were sampled every 10 days. The addition of poultry litter hydrochar resulted in decreased soil bulk density. Soil porosity increased with hydrochar generated at a temperature of up to 220 � C, and decreased with hydrochar generated at 250 � C. Soil water content increased as compared to unamended sand, but decreased with increasing hydrochar-production temperature, probably due to increasing hydrophobicity of the poultry litter hydrochar. The addition of hydrochar at concentrations of 0.5 and 1% resulted in improved plant growth despite an initial delay. While increased soil moisture due to increased soil water-retention capacity was confirmed, it did not seem to be responsible for the improved plant growth. It was also demonstrated for the first time that hydrochar decreases nitrate leaching from soils. Therefore, poultry litter-derived hydrochar seems to be an adequate amendment for sandy soils.
... It has been shown that hydrochar yield and carbon concentration are positively impacted by solid load (Heilmann et al. 2014). However, at high solid loads, such as solid-to-water ratios of 1:5 and 1:3, the effect on hydrochar as well as aqueous and gaseous phases composition is no longer significant (Mau et al. 2016). ...
... 18 3/3/2020 5:55:45 PM for hydrochar derived from maize silage at 230°C for 10 hours (Mumme et al. 2011). Typically, hydrochar has a calorific value of around 25 MJ/kg (Kambo and Dutta 2015), comparable to subbituminous coal, which is used for electricity production (Mau et al. 2016). ...
... These compounds are not detected in the untreated feedstock, confirming they arise as a result of feedstock carbonization (Danso-Boateng et al. 2015). The aqueous phase is also rich in several nutrients such as N, P, K, Na, Ca, Mg, and S, with concentrations varying depending on the original feedstock (Spitzer et al. 2018;Mau et al. 2016). ...
... The peak at 1650 cm −1 concerns the C=O stretching of CO 2 H and C=O of primary amides, which indicates the presence of protein. A CH 2 deformation peak registered at 1416 cm −1 is characteristic of saturated fatty acids and cellulose [44]. The peak at 1233 cm −1 of C-O is associated with the stretching of carbohydrates. ...
... The observed peak at 1416 cm −1 , which is associated with CH 2 deformation for both biochars, presents an intensity increase with temperature [39]. Also, the bonding of C-O increased at 1233 cm −1 , which is associated with the stretching of -COH in alcohols and -COR in aliphatic ethers [44]. The peak between 871 and 1024 cm −1 in the raw poultry manure is associated to aromatic -CH out-of-plane bending vibrations. ...
... The peak between 871 and 1024 cm −1 in the raw poultry manure is associated to aromatic -CH out-of-plane bending vibrations. This peak increased with the pyrolysis temperature, indicating a gradual conversion of aromatic structures during this process [44]. The presence of the various above-cited functional groups may play an important role in nutrient leaching from these biochars and especially pollutant adsorption from wastewaters [45,46]. ...
Raw poultry manure (RPM) and its derived biochars at temperatures of 400 (B400) and 600 °C (B600) were physico-chemically characterized, and their ability to release nutrients was assessed under static conditions. The experimental results showed that RPM pyrolysis operation significantly affects its morphology, surface charges, and area, as well as its functional groups contents, which in turn influences its nutrient release ability. The batch experiments indicated that nutrient release from the RPM as well as biochars attains a pseudo-equilibrium state after a contact time of about 48 h. RPM pyrolysis increased phosphorus stability in residual biochars and, in contrast, transformed potassium to a more leachable form. For instance, at this contact time, P- and K-released amounts passed from 5.1 and 25.6 mg g−1 for RPM to only 3.8 and more than 43.3 mg g−1 for B400, respectively. On the other hand, six successive leaching batch experiments with a duration of 48 h each showed that P and K release from the produced biochars was a very slow process since negligible amounts continued to be released even after a total duration of 12 days. All these results suggest that RPM-derived biochars have specific physico-chemical characteristics allowing them to be used in agriculture as low-cost and slow-release fertilizers.
... Another possible use of the aqueous phase is as a liquid fertilizer, taking advantage of its high nutrient content. 21 While a few studies have considered the impact of the aqueous phase on germination, 22−24 to our knowledge, only one study has considered its effect on plant growth. 25 Moreover, the combination of aqueous-phase recirculation and use as a liquid fertilizer has never been investigated. ...
... The stainless-steel tubular cylinder reactors (27 mm diameter, 50 mL volume) have been proven to withstand the expected temperatures and pressures in previous experiments. 21,26 One of the reactors was equipped with a temperature probe to monitor internal temperature during the entire process. To ensure even and rapid heating, the reactors were submersed in a preheated oil bath containing Paratherm HR (Conshohocken, PA) heat-transfer fluid. ...
... However, the absence of NO 3 − and substantial TAN concentrations have been previously observed in the aqueous phase of poultry litter (without recirculation). 21,25 Therefore, the N in the aqueous phase seemed to consist mainly of organic N which, together with DOC, accumulated with recirculation to a certain degree, while TAN was unaffected by recirculation. Similar trends and ranges have been reported for HTC recirculation studies of poultry litter. ...
Hydrothermal carbonization (HTC) has received much attention in recent years as a process to convert wet organic waste into carbon-rich hydrochar. The process also generates an aqueous phase that is still largely considered a burden. The success of HTC is dependent on finding solutions for the aqueous phase. In the present study, we provide the first investigation of recirculation of the aqueous phase from HTC of poultry litter as a means to concentrate nutrients, and its subsequent application to agriculture as a fertilizer. Aqueous-phase recirculation generally resulted in an increase in nitrogen, phosphorus and potassium concentrations up to cycle 3 with maximum concentrations reaching up to 5400, 397, and 23300 mg L-1 for N, P and K, respectively. Recirculation did not adversely affect hydrochar composition or calorific value. The recirculated and non-recirculated aqueous phases were able to support lettuce growth similar to a commercial fertilizer. Results from this study indicate that the combination of aqueous-phase recirculation and use as a fertilizer can be a suitable method to reutilize the aqueous phase and recycle nutrients back into agriculture, thus increasing HTC efficiency and economic feasibility.
... Common poultry-litter treatments include composting, anaerobic digestion and direct combustion. However, these all have their drawbacks [3,4], and alternatives solutions are needed [5]. ...
... The installation consisted of a fluidized-bed reactor for torrefaction (1), a feedstock hopper for initial biomass (2), a hopper for biochar (3), a cyclone (4) for separating the steam-gas flow from the bio-coal particles removed from the reactor, and a condenser of the steam-gas mixture (5). The steam generation was performed in a boiler. ...
A numerical model for the wet torrefaction of poultry litter in a pilot unit was developed
in this study. The model accounted for the following process steps: preheating biomass in a feed hopper, feeding biomass into the reactor, fluidized-bed generation using superheated steam, and the supply of additional heat by the electric heating of the reactor walls. Following a “black box” approach, a major assumption of the model is that the behavior of the fluidized-bed reactor is similar to a completely stirred tank reactor (CSTR). Under this assumption, the properties of the particles and gases do not depend on their location inside the reactor. During wet torrefaction, poultry-litter biomass was heated to a predetermined temperature and decomposed, generating biochar along with a gas phase (torgas), whose amounts depended on the content of inert ash in the biomass particles. Variable optimization in the model was performed using MATLAB software. The model successfully estimated the optimal duration required for the completion of wet torrefaction under various conditions: temperature, batch weight, reactor dimensions, etc. The model was validated using experimental data obtained from a series of wet torrefaction experiments performed in a fluidized bed, and provided reliable estimations of the duration of the process depending on material properties, reactor size and feedstock characteristics.
... Temperature is considered as the main factor that affects HTC reactions and enhances biomass conversion efficiency by providing more energy for breaking the intermolecular bonds in the feedstock [83][84][85]. Higher conversion rates can be achieved as well at longer retention times [86][87][88]. Temperature, residence time, and, to a lesser extent, solid load can be used to measure the severity of the process [23,88,89]. ...
... One of the main challenges of PW recirculation during HTC is the optimization of process parameters and the investigation of their effective influence for different biomasses. It was observed that, as the reaction severity increases (high temperatures and long residence times), there are more mass transfers from the feedstock towards the liquid phase [83,87,88]. However, at high temperatures and long retention times, a lower concentration of reactive soluble compounds could be available in the recycled PW; indeed, these substances could be more involved in decarboxylation reactions to form gaseous products and in re-polymerization reactions to aggregate into the hydrochar matrix during the first HTC step [76]. ...
Hydrothermal carbonization (HTC) is considered as an efficient and constantly expanding eco-friendly methodology for thermochemical processing of high moisture waste biomass into solid biofuels and valuable carbonaceous materials. However, during HTC, a considerable amount of organics, initially present in the feedstock, are found in the process water (PW). PW recirculation is attracting an increasing interest in the hydrothermal process field as it offers the potential to increase the carbon recovery yield while increasing hydrochar energy density. PW recirculation can be considered as a viable method for the valorization and reuse of the HTC aqueous phase, both by reducing the amount of additional water used for the process and maximizing energy recovery from the HTC liquid residual fraction. In this work, the effects of PW recirculation, for different starting waste biomasses, on the properties of hydrochars and liquid phase products are reviewed. The mechanism of production and evolution of hydrochar during recirculation steps are discussed, highlighting the possible pathways which could enhance energy and carbon recovery. Challenges of PW recirculation are presented and research opportunities proposed, showing how PW recirculation could increase the economic viability of the process while contributing in mitigating environmental impacts.
... Biochars, including those produced with microwave-assisted pyrolysis (MAP) and hydrochars produced by hydrothermal carbonization (HTC), are becoming attractive as low-cost adsorbents because they are produced from readily available agricultural and forestry wastes, such as crop residue, animal manure and sawdust, at temperatures below 600 • C (Elaigwu et al., 2014;Liu and Zhang, 2009;Wu et al., 2019). Moreover, MAP is time-saving (Foong et al., 2020), and HTC is energy-efficient (Mau et al., 2016), and the derived adsorbents or chars from both methods have excellent properties such as large specific surface area, an abundance of functional groups and well-developed pores. Nevertheless, these properties can vary with feedstock type and production temperature (Liu and Zhang, 2009;Yap et al., 2017); changes in those properties will affect lead(II) removal, adsorption capacities and kinetics of these adsorbents. ...
... Biochars produced by pyrolysis had mainly alkaline pH and non-saline to saline EC, due to the intense loss in carboxylic acid groups and the fixation of inorganic minerals such as carbonates (Fig. 4) and phosphates during pyrolysis (Mireles et al., 2019). Hydrochars produced by HTC had acidic to near-neutral pH and non-saline EC due to the formation of low molecular weight organic acids (e.g., oxalic and citric acids) and other products such as inorganic minerals in subcritical water (Mau et al., 2016). Electrical conductivity and ash content were significantly lower in the hydrochars than the biochars (Fig. 1g), likely because of the dissolution of minerals from the hydrochar into the HTC liquid phase (Elaigwu et al., 2014;Fang et al., 2018). ...
Adsorption of lead(II) using carbon-rich chars is an environmentally sustainable approach to remediate lead(II) pollution in industrial wastewater. We studied mechanisms for lead(II) adsorption from synthetic wastewater by biochars produced by microwave-assisted pyrolysis and hydrochars by hydrothermal carbonization at three temperatures using four feedstocks. Lead(II) adsorption was highest (165 mg g⁻¹) for canola straw biochar produced at 500 °C. Except for chars derived from sawdust, biochars outperformed hydrochars for lead(II) adsorption due to changes in solution pH driven by char pH. As char production temperature increased, lead(II) adsorption decreased in hydrochar mainly due to interaction with aromatic carbon but increased in biochar due to precipitation as hydrocerussite and lead oxide phosphate. Lead(II) adsorption also occurred via surface complexation and cation-ᴨ interaction, as the data fitted well to Freundlich, Langmuir and Temkin models, and the pseudo-first and pseudo-second order kinetic models, depending on feedstock type and production temperature. More than 80% of lead(II) adsorption occurred in the first 3 h for both types of chars; with a few exceptions, adsorption continued for almost 24 h. We conclude that production method, production temperature and feedstock type are crucial factors to consider in designing chars as adsorbents for removing lead(II) from wastewater.
... The mediation of the removal and retention of N in hydrochar is the frontier of future investigations on HTC of N-rich biomass. (Du et al., 2012;Ekpo et al., 2016;Falco et al., 2012;Heilmann et al., 2010;Levine et al., 2013;Park et al., 2018; (Greiserman et al., 2019;Lane et al., 2018;Neveux et al., 2014;Parsa et al., 2019;Xu et al., 2013 (Feng et al., 2018;He et al., 2013He et al., , 2015Ma et al., 2019;Park et al., 2018;Zheng et al., 2019;Zhuang et al., 2017) (Ekpo et al., 2016;Lang et al., 2018;Mau et al., 2016;Ro et al., 2017;Toufiq Reza et al., 2016) Food Benavente et al., 2015;Berge et al., 2011;Cao et al., 2013;X. Chen et al., 2017;Lane et al., 2018;Li et al., 2019;Petrović et al., 2016;Wang et al., 2018b; (Berge et al., 2011;Cai et al., 2016;Cao et al., 2013;Lane et al., 2018;Lang et al., 2018;Ma et al., 2019;Román et al., 2020;Xiao et al., 2012;Yao et al., 2016) Screening HTC parameters, such as reaction severity, and the engineering of the biochemical compositions of biomass, e.g., by using biomass mixtures and pretreatment of biomass, are the priorities to mediate the transformation of N during HTC (Leng et al., 2018c(Leng et al., , 2016. ...
... Du et al., 2012;Ekpo et al., 2016;Falco et al., 2012;Heilmann et al., 2010;Levine et al., 2013;Park et al., 2018; Macroalgae N char = 3.29 − 0.005 × HR 43 0.90-5.90 0.16 ⁎ HR ⁎ , Log R0, H (Greiserman et al., 2019;Lane et al., 2018;Neveux et al., 2014;Parsa et al., 2019;Xu et al., 2013 (Ekpo et al., 2016;Lang et al., 2018;Mau et al., 2016;Ro et al., 2017;Toufiq Reza et al., 2016) Food waste N char = 1.11 + 0.677 × N 44 1.10-5.30 0.57 ⁎⁎⁎ N ⁎⁎⁎ , C, A, V, FC (Benavente et al., 2015;Berge et al., 2011;Cao et al., 2013;X. ...
Biomass is a type of renewable and sustainable resource that can be used to produce various fuels, chemicals, and materials. Nitrogen (N) in biomass such as microalgae should be reduced if it is used to produce fuels, while the retention of N is favorable if the biomass is processed to yield chemicals or materials with N-containing functional groups. The engineering of the removal and retention of N in hydrochar during hydrothermal carbonization (HTC) of biomass rich in protein is a research hot spot in the past decade. However, the N transformation during HTC has not yet been fully understood. In order to mediate the migration and transformation of N in hydrochar, the present review overviewed i) the characteristics of hydrochar and the original feedstock, ii) the possible N transformation behavior and mechanisms, and iii) the effect of factors such as feedstock and pyrolysis parameters such as temperature on hydrochar N. The high temperature and high protein content promote the dehydration, decarboxylation, and deamination of biomass to produce hydrochar solid fuel with reduced N content, while the Millard and Mannich reactions for lignocellulosic biomass rich in carbohydrate (cellulose, hemicellulose, and lignin) at medium temperatures (e.g., 180–240 °C) significantly promote the enrichment of N in hydrochar. The prediction models can be built based on properties of biomass and the processing parameters for the estimation of the yield and the content of N in hydrochar.
... The raw sludge, hydrochar, and Fenton-activated hydrochar (AH50-30) were characterized using ATR-FTIR ( Fig. 1; note that all AHs had similar FTIR spectra; see Fig. S1 in the supplementary information). Several changes are observable in the hydrochar FTIR spectrum compared to that of the raw sludge: the broad peak in the range 2800e3600 cm À1 , which is indicative of carboxylic acid and hydroxyl groups (Ledesma et al., 2018;Mau et al., 2016), and the bands in the range 1550e1650 cm À1 , which are ascribed to the presence of amide motifs, decreased following HTC. In addition, the peak in the range 2800e3500 cm À1 shifted towards higher wavenumbers, indicating an increased presence of hydroxyl groups (Sun et al., 2015;Wahab et al., 2010). ...
... This increase is attributed to an increase in hydrochar carbon content (Elaigwu and Greenway, 2016;Nguyen et al., 2019). All of these changes are likely due to dehydration and decarboxylation during the HTC process and the development of new functional groups in the hydrochar (Mau et al., 2016;Tasca et al., 2019). ...
Lately, there has been a growing interest in converting low-cost biomass residuals, including wastewater sludge, into char-like materials for various applications. In this research, ammonium (NH4+) adsorption and desorption potential of hydrochar activated via Fenton oxidation were systematically investigated. Hydrochar was prepared from domestic wastewater treatment plant sludge and activated by Fenton oxidation using different H2O2 concentrations, H2O2/Fe2+ ratios, and activation times. The activated hydrochars (AHs) were characterized by ATR-FTIR, high-resolution XPS, BET specific surface area, and SEM, and their NH4+ adsorption capacity was analyzed. The NH4+ adsorption isotherms and kinetics, adsorption in the presence of competing ions (with and without humic acid), and NH4+ desorption were investigated. The results show that following hydrochar activation, the acidic groups’ concentration and the BET surface area increased, but the morphology remained essentially unchanged. It was also found that the activation occurs within a few minutes when using a relatively low concentration of reagents, and without extensive post-treatment steps. The NH4+ adsorption onto AH at equilibrium fitted the Langmuir isotherm model, with a maximum adsorption capacity of 30.77 mg∙g-1, and the NH4+ adsorption kinetics fitted the pseudo-second-order model. NH4+ adsorption in the presence of competing ions decreased by up to 33±3%. NH4+ desorption experiments demonstrated that NH4+ recovery can reach 33±5% with ultrapure water and 67±2% with 2 M KCl. The results of this study indicate that Fenton oxidation is a promising alternative for hydrochar activation, and can be used as an adsorbent for NH4+ remediation in wastewater treatment processes.
... The peaks at 2922, 1410, and 2850 cm −1 were attributed to C-H stretching and/or deforming in CH 3 , representing the presence of hydroaromatic and aliphatic structures Posmanik et al. 2020). The bands at 1642 cm −1 represented (Mau et al. 2016;Posmanik et al. 2020;Belete et al. 2021). The peak near 1033 cm −1 was probably from -Si-O (SiO 2 ) stretching or from the presence of C-O (acids, alcohols, ethers, lignin) functional groups that were retained in the hydrochar Posmanik et al. 2020;Belete et al. 2021). ...
The hydrothermal pretreatment (HTP) characteristics and the fate of phosphorus (P) and anaerobic digestion (AD) performance of dewatered sewage sludge (DSS) were investigated at different hydrothermal conditions. The maximum methane yield reached 241 mL CH4/g COD when the hydrothermal conditions were 200 °C-2 h-10% (A4), and the yield was 78.28% higher than that without pretreatment (A0) and 29.62% higher than that of the initial hydrothermal conditions (A1, 140 °C-1 h-5%). Proteins, polysaccharides, and volatile fatty acids (VFAs) were the main hydrothermal products of DSS. 3D-EEM analysis revealed that tyrosine, tryptophan proteins, and fulvic acids decreased after HTP, but the content of humic acid-like substances increased, and this phenomenon was more noticeable after AD. Solid-organic P was converted into liquid-P during the hydrothermal process, and nonapatite inorganic P was converted into organic P during AD. All samples achieved positive energy balance, and the energy balance of A4 was 10.50 kJ/g VS. Microbial analysis showed that the composition of the anaerobic microbial degradation community changed as the sludge organic composition was altered. Results showed that the HTP improved the anaerobic digestion of DSS.
... The fuel value index (FVI) reflected the relationship between the energy-intensive efficiency of the fuel and the ash content which indicates the potential of the material used for energy production [21]. The energy balance (E balance ) was used to measure the equilibrium relationship between the input energy and output energy during the preparation process of fuel, where the input energy was based on the total amount of energy required to heat the dry feedstock and aqueous phase during hydrothermal processing [26]. Meanwhile, the energy output was calculated based on the hydrochar yield and the heat of combustion, which corresponds to HHV. ...
Hydrothermal carbonization (HTC) of biomass remained promising as a low-cost and eco-friendly technique for solid fuel production. However, the common HTC approaches usually suffered low mass yields due to the dissolution of intermediates into the liquid phase. In this study, different catalyst solutions were prepared using three surfactants (sodium dodecyl benzene sulfonate (SDBS), Span 80 and Tween 80) and citric acid solution with a pH of 3.61 as the reaction medium. Surfactant/citric acid catalyzed HTC was performed under a 3:1 pomelo peel/surfactant mixing ratio and reaction temperature of 220 • C for 6 h. Compared with the citric acid-catalyzed HTC, SP80/citric acid catalyzed hydrochar demonstrated an increased solid yield from 39.04 % to 63.45 %, and enhanced HHV from 24.122 MJ/kg to 31.302 MJ/kg. Meanwhile, Tween 80 increased the hydrochar solid yield and HHV to 50.17 %, and 28.281 MJ/kg, respectively. The co-firing of hydrochars cata-lyzed by Span 80 and Tween 80 with coal significantly improved its combustibility, and further reduced the activation energy to 15.20-25.49 kJ/mol. Synergistic effects were observed during the co-combustion of sur-factant/citric acid catalyzed hydrochar and coal. This work showed that the unique amphiphilic properties of surfactants can help to regulate the composition of products during acid-catalyzed HTC, resulting in better fuel properties and combustion performance.
... To better understand the nature of the organic carbon transformations through the presence and dynamics of functional groups in the laboratory-scale experiments with different temperatures and particle sizes and onsite anaerobic treatment, ATR-FTIR spectroscopic analyses of the raw and digested solids of all treatments were performed. The most important bands found in the spectra of plant wastes and their usual behavior during degradation were characterized in Appendix Table A4 based on literatures (de Diego-Díaz et al., 2021;Kataki et al., 2017;Mau et al., 2016;Provenzano et al., 2014;Zhu et al., 2021). ...
Crop residues, such as toxic tomato plant wastes, often cause environmental and economic burdens. Anaerobic digestion of these residues, which contain hardly biodegradable lignocellulosic content and low C/N (~10), was not thoroughly studied or practiced. This study investigated the impacts of temperature and particle size on anaerobic degradation performance of tomato plant waste in both laboratory and field scales (the latter was studied for one year under desert conditions). The highest batch degradation rate was observed for the smallest particles <0.15 mm and highest temperature (35 °C). In the field reactor, 89 % of the organic carbon was recovered as biogas containing 62 % CH4. The average biogas yield was 0.55 m³/kg-VS. The digestor supernatant contained N and P of 657 mg/L and 76 mg/L, respectively, mostly as ammonia and soluble reactive-P. Onsite anaerobic digestion of tomato plant waste can efficiently reduce pollution burden, produce biogas, and recover nutrients under desert conditions.
... The conversion of sludge to solid hydrochar increases the potential for energetic applications and provides significant ease in handling, storage, and transportation [19] . HTC offers advantages over dry thermochemical processes such as pyrolysis, torrefaction and gasification, as the process is not influenced by the moisture content of the feedstock [20] , it requires subcritical to supercritical water temperatures under autogenous pressure [21][22][23][24] which is relatively low, and the overall process is considered an exothermic [25] thereby decreasing the energy consumption. Moreover, the resulting solid product known as "hydrochar" has higher energy density [26] with cleaner properties [27] compared to the raw feedstock, is easily dewatered and can be applied in monocombustion or co-combustion at coal-fired power plants for electricity generation. ...
The incineration of high‐moisture solid residues generated at the recycling paper mills represents an energetically unfavourable method of resource utilization. Alternatively, hydrothermal pre‐treatment is considered. In this study, low‐value paper sludges from three different recycling streams were hydrothermally carbonized at 205 °C, 225 °C and 245 °C for 3 hours. The raw feedstocks and derived hydrochars were analyzed for energy properties, chemical characteristics, surface morphology, functional groups and combustion performance employing energy densification and mass yield quantification, scanning electron microscopy, elemental analyzer, Fourier‐transform Infrared Spectroscopy and thermogravimetry. The increase in reaction temperature reported a decrease in mass yield and an increase in energy densification and calorific values corresponding to 5.98‐49.35 % and 10.10‐58.51% for raw fibre rejects and final sludge‐derived hydrochar. HTC had a non‐significant influence on the energy densification of primary clarifier sludge‐derived hydrochar. Higher reaction temperatures favoured the rate of dehydration and decarboxylation leading to hydrochars with lower H/C and O/C ratios, thereby enhancing the overall fuel properties. The low‐nitrogen and low‐sulphur fuels obtained validated the effectiveness of HTC treatment to produce high‐quality cleaner solid fuel. The burnout temperature was mostly reduced with an increase in HTC temperature. At HTC‐205°C and 225°C, the ignition temperature and the combustion performance increased as a result of the HTC reaction mechanisms. HTC effectively recovered hydrochar with increased carbon content, improved energy densification and good combustion adequacy. Hydrochar derived from recycling mills may play a role in the energy sector as a substitute for coal or in co‐combustion at coal‐fired power plants. This article is protected by copyright. All rights reserved.
... The increased hydrogen content for the modified (vs. pristine) hydrochars produced at 180 • C suggests that cellulose-derived compounds such as 5-(hydroxylmethyl) furfural were not released from hydrochars during the modification (Mau et al., 2016). ...
Elevated metal (e.g., alkali metals) and ash contents can negatively impact the use of biomass-derived solid fuels, including hydrochars, in clean energy generation. The effects of nitric acid modification on those and other properties (combustion, fuel and thermal) were studied for hydrochars produced at three temperatures from four feedstocks. Through side-chain oxidation and surface protonation, nitric acid significantly leached metals from pristine hydrochars to a maximum of five order and increased their burnout temperature by 9-41%, but its effect on ash content, gross calorific values and ignition temperature depended on feedstock type and carbonization temperature. Ignition temperature increased by >2 times for modified manure pellet hydrochar produced at 300 ℃. The combustion characteristics index for the hydrochars was above the minimum benchmark (2 x 10⁻⁷ %² min⁻² °C⁻³) for a typical solid fuel. Therefore, nitric acid can effectively improve hydrochar’s combustion and fuel properties and reduce slagging in industrial boilers.
... the HTT increases to 250 • C, the enhanced carbonization of biomass would result in development of abundant pores in hydrochars [128], while higher temperature (> 250 • C) decreases the surface area due to the blockage of pores by condensed volatile matters and sedimented minerals [129]. Moreover, low pH of the process water will facilitate the hydrolysis of carbohydrate and enhance microsphere formation, thus increasing hydrochar surface area at the early stage of HTC [126]. ...
... In addition to feedstock, HTT also significantly regulates hydrochar surface area [101]. As the HTT increases to 250 °C, the enhanced carbonization of biomass would result in development of abundant pores in hydrochars [131], while higher temperature (> 250 °C) decreases the surface area due to the blockage of pores by condensed volatile matters and sedimented minerals [132]. Moreover, low pH of the process water will facilitate the hydrolysis of carbohydrate and enhance microsphere formation, thus increasing hydrochar surface area at the early stage of HTC [129]. ...
With the rapid global population growth and industrial development, the promotion of sustainable agricultural production and environmental conservation has attracted great public and research interests. Application of carbonaceous materials (e.g., activated carbon, biochar, and hydrochar) for soil improvement and environmental remediation is highly recommended because of their economic viability and applicability. Hydrochars, carbonaceous solid materials with unique physicochemical properties and produced by hydrothermal carbonization (HTC) of biomass, have received wide attention due to their increasing applications as soil amendments, slow-release fertilizers, adsorbents, and energy sources. This review highlights the production of hydrochars from dry and wet feedstocks and summarizes the physicochemical properties including surface structure, porosity, nutrient content, and stability. Applications of hydrochars for soil improvement and environmental remediation are systematically analyzed and reviewed on the aspects of improving soil physicochemical and biological properties, affecting greenhouse gas emission, and remediating heavy metals and organic pollutants in water and soil environments. Finally, the knowledge gaps in the production, characterization, and application of hydrochars are addressed and the future research directions toward the development of hydrochar technology are proposed.
... HTC is conducted at high pressures with a closed reactor and all gases generated during the process are only emitted once the treatment has concluded. In addition, NH 3 is not emitted as a gas due to the low pH of the aqueous phase (Mau et al., 2016). Therefore, N in the HC might be plant available, and volatilised C and N can be dissolved in HTC liquor. ...
The dairy industry produces vast quantities of dairy processing sludge (DPS), which can be processed further to develop second generation products such as struvite, biochars and ashes (collectively known as STRUBIAS). These bio-based fertilizers have heterogeneous nutrient and metal contents, resulting in a range of possible application rates. To avoid nutrient losses to water or bioaccumulation of metals in soil or crops, it is important that rates applied to land are safe and adhere to the maximum legal application rates similar to inorganic fertilizers. This study collected and analysed nutrient and metal content of all major DPS (n = 84) and DPS-derived STRUBIAS products (n = 10), and created an application calculator in MS Excel™ to provide guidance on maximum legal application rates for ryegrass and spring wheat across plant available phosphorus (P) deficient soil to P-excess soil. The sample analysis showed that raw DPS and DPS-derived STRUBIAS have high P contents ranging from 10.1 to 122 g kg − 1. Nitrogen (N) in DPS was high, whereas N concentrations decreased in thermo-chemical STRUBIAS products (chars and ash) due to the high temperatures used in their formation. The heavy metal content of DPS and DPS-derived STRUBIAS was significantly lower than the EU imposed limits. Using the calculator, application rates of DPS and DPS-derived STRUBIAS materials (dry weight) ranged from 0 to 4.0 tonnes ha − 1 y − 1 for ryegrass and 0-4.5 tonnes ha − 1 y − 1 for spring wheat. The estimated heavy metal ingestion to soil annually by the application of the DPS and DPS-derived STRUBIAS products was lower than the EU guideline on soil metal accumulation. The calculator is adaptable for any bio-based fertilizer, soil and crop type, and future work should continue to characterise and incorporate new DPS and DPS-derived STRUBIAS products into the database presented in this paper. In addition, safe application rates pertaining to other regulated pollutants or emerging contaminants that may be identified in these products should be included. The fertilizer replacement value of these products, taken from long-term field studies, should be factored into application rates.
... The structure of the resulting hydrochar is similar to that of coal, thus making it applicable as a solid fuel, soil amendment, and adsorbent (Nogueira et al., 2019;Tan et al., 2016). Previous studies on the HTC of swine manure or chicken manure have demonstrated their potential in the production of solid fuels (Lang et al., 2019b;Mau et al., 2016). ...
Co-hydrothermal carbonization (HTC) of livestock manure and biomass might improve the fuel properties of the hydrochar due to the high reactivity of the biomass-derived intermediates with the abundant oxygen-containing functionalities. However, the complicated compositions make it difficult to explicit the specific roles of the individual components of biomass played in the co-HTC process. In this study, cellulose was used for co-HTC with swine manure to investigate the influence on the properties of the hydrochar. The yield of hydrochar obtained from co-HTC reduced gradually with the cellulose proportion increased, and the solid yield was lower than the theoretical value. This was because the cellulose-derived intermediates favored the stability of the fragments from hydrolysis of swine manure. The increased temperature resulted in the reduction of the hydrochar yield whereas the prolonged time enhanced the formation of solid product. The interaction of the co-HTC intermediates facilitated the formation of O-containing species, thus making the solid more oxygen- and hydrogen-rich with a higher volatility. In addition, the co-HTC affected the evolution of functionalities like -OH and C=O during the thermal treatment of the hydrochar and altered its morphology by stuffing the pores from swine manure-derived solid with the microspheres from HTC of cellulose. The interaction of the varied intermediates also impacted the formation of amines, ketones, carboxylic acids, esters, aromatics and the polymeric products in distinct ways.
... The pH of the process water was found to be 3.95 and was comparable with results obtained by Escala et al. (2013). Previous report by Mau et al. (2016) attributed this phenomenon to the decomposition of cellulose biomass which produced organic acids. The process water was found to contain significant quantities of N (1120.8 ...
This research determines the effects of temperature, residence time and mixing ratio on hydrochar yield and energy content from the co- hydrothermal carbonization (co-HTC) of pineapple and watermelon peels. The research assessed optimum conditions for higher hydrochar yields and energy content as well as the synergistic effects of pineapple and watermelon peels on the co-HTC process. Results show that hydrochar yield decreased with increasing temperature and residence time. In contrast, energy and carbon content increased with increasing temperature and residence time. Pineapple peels showed greater hydrochar yields and energy contents than watermelon peels. The optimum conditions for co-processing are 180 °C, 120 min and a mixing ratio of 70:30 for pineapple and watermelon peels respectively. Synergistic effects occurred during the co-HTC of pineapple and watermelon peels with a decrease in hydrochar yield and an increase in energy and carbon content.
... The structure of the resulting hydrochar is similar to that of coal, thus making it applicable as a solid fuel, soil amendment, and adsorbent (Nogueira et al., 2019;Tan et al., 2016). Previous studies on the HTC of swine manure or chicken manure have demonstrated their potential in the production of solid fuels (Lang et al., 2019b;Mau et al., 2016). ...
Swine and chicken manures are abundant solid wastes that can be converted into carbonaceous materials through hydrothermal carbonization (HTC). Owing to their unique biochemical compositions, co-HTC of these two types of manures may have significant implications for the generated products. We investigated the co-HTC of swine manure and chicken manure to understand the influence of the interaction between contrasting manures on the properties of the derived products. The results indicated that co-HTC treatment enhanced the formation of solid product and improved the C and N contents, heating value, and energy yield of the resulting hydrochar. Regarding the ignition temperature and comprehensive combustion index, the combustion properties of the hydrochar were enhanced owing to the mutual effect of the HTC intermediates. Additionally, the interaction of the intermediates significantly impacted the transfer of nitrogenous species and generation of organic acids and organic polymers with fused-ring structures. Therefore, co-HTC processing of animal manures could potentially provide a sustainable pathway for the conversion of animal waste into solid products with improved characteristics compared to those produced by treating the two feedstocks separately.
... Because of environmental concerns (odor, greenhouse gas emissions, pathogens spreading and pollution of water), chicken manure cannot be disposed of in landfill sites [8,9]. Therefore, various approaches have been employed to solve this problem, including composting [10][11][12][13], pyrolysis [14][15][16], combustion [17,18], gasification [19][20][21], hydrothermal carbonization [22,23] and anerobic fermentation [24][25][26]. ...
Animal waste is generated at an increased rate, and its disposal is attracting wide public attention. Anaerobic digestion is considered the most promising option for reducing this waste, and simultaneously, it produces renewable energy. Lignin contained in lignocellulosic biomass is hardly biodegradable, thus pre-treatment has to be considered prior to digestion. The possibility of biological pre-treatment of chicken manure with sawdust using Pleurotus ostreatus fungi was investigated in our study. This animal waste was used as a substrate for further biogas production. To provide a better nutrient balance, we added two different co-substrates, wheat straw and Miscanthus. Mixtures with different mass ratios of chicken manure with sawdust/ordinary wheat straw, as well as chicken manure with sawdust/pre-treated wheat straw were incubated for 30 d. The same experiments were performed with Miscanthus. During incubation, samples were taken at predetermined time intervals, and the concentration of acid-insoluble lignin was determined. Additionally, concentrations of glucose and xylose in the filtrate taken at the end of the Klasson procedure were determined in the initial samples and in the samples after 30 d of incubation. Despite our expectations, almost no lignin degradation was observed. Insignificant decreases in glucose and xylose concentrations after 30 d is attributed to fungi ingestion. Obtained results show that Pleurotus ostreatus, as a white-rot fungi with a unique enzymatic system and as generally preferred organisms for lignin degradation, is, therefore, not suitable for delignification of this particular animal waste.
... High Sodicity of wastewater, caused by high sodium concentrations is expected to cause soil swelling and dispersion, surface crusting and pore plugging leading to reduced infiltration and increased runoff within the soil clays (Oster, 1994). Still, the presence of the divalent ions, namely Ca þ2 and Mg þ2 , can mitigate the impact of sodicity (Mau et al., 2016). Table 2 shows the concentrations of Na þ , Ca þ2 , and Mg þ2 for all collected samples, indicating high values of SAR. ...
Industrial wastewater is a growing environmental challenge due to its high concentrations of organics and its limited biological degradability. Up to date, however, no published work discussed industrial wastewater characterization, which is the focus of this study. Moreover, the effect of hydrothermal treatment on the chemical oxygen demand (COD) removal and the soluble chemical oxygen demand (SCOD) release was investigated in this work. Wastewater samples were collected from different industrial sites and characterized in order to determine their initial properties. It was summarized that the salinity of wastewater estimated by EC was relatively low, and its pH values were in the acceptable range. On the other hand, however, high values of sodium absorption ratio (SAR) were obtained in all samples post to hydrothermal treatment. Nonetheless, our results revealed higher SCOD release post to hy-drothermal treatment suggesting better efficiency of COD removal obtained by this treatment technique.
... Mau and Gross (2017) combusted biochar produced from poultry litter and suggest that there is considerable potential for electricity generation. Besides the use of pyrolysis to produce biochar their study also considered hydrothermal carbonization, where wet material is converted into hydrochar (Ghanim et al., 2016;Mau et al., 2016). Cotana et al. (2014) showed the potential of the gasification of poultry litter and combustion with a Stirling engine, while de Graaff et al. (2017) have assessed impacts of co-firing in a wood biomass plant. ...
The production of broiler meat has increased significantly in the last decades in Germany and worldwide, and is projected to increase further in the future. As the number of animals raised increases, so too does the amount of manure produced. The identification of manure treatment options that cause low greenhouse gas emissions becomes ever more important. This study compares four treatment options for broiler manure followed by field spreading: storage before distribution, composting, anaerobic digestion in a biogas plant and production of biochar. For these options potential direct and indirect greenhouse gas emissions were assessed for the situation in Germany. Previous analyses have shown that greenhouse gas balances of manure management are often strongly influenced by a small number of processes. Therefore, in this study major processes were represented with several variants and the sensitivity of model results to different management decisions and uncertain parameters was assessed. In doing so, correlations between processes were considered, in which higher emissions earlier on in the process chain reduce emissions later. The results show that biogas production from broiler manure leads to the lowest greenhouse gas emissions in most of the analysed cases, mainly due to the emission savings related to the substitution of mineral fertilizers and the production of electricity. Pyrolysis of the manure and subsequent field spreading as a soil amendment can lead to similarly low emissions due to the long residence time of the biochar, and may even be the better option than poorly managed biogas production. Composting is the treatment option resulting in highest emissions of greenhouse gases, due to high ammonia volatilization, and is likely worse than untreated storage in this respect. These results are relatively insensitive to the length of transport required for field spreading, but high uncertainties are associated with the use of emission factors.
... Li et al., 2017b;Z. Li et al., 2017c;Liu et al., 2015;López Barreiro et al., 2015b;Lu et al., 2017;Maddi et al., 2016Maddi et al., , 2017Madsen et al., 2016a;Martinez-fernandez and Chen, 2017;Mau et al., 2016;Mursito et al., 2010;Nelson et al., 2013;Nurdiawati et al., 2017;Panisko et al., 2015;Pedersen et al., 2016;Posmanik et al., 2017;Reddy et al., 2016;Shen et al., 2017Shen et al., , 2018Si et al., 2018;Stemann et al., 2013;Teymouri et al., 2017;Wang et al., 2016;Watson et al., 2017;Weiner et al., 2014;Wirth and Reza, 2016;Yu et al., 2011;Zhang et al., 2016;Zheng et al., 2017;Zhou et al., 2011Zhou et al., , 2013Zhou et al., , 2015. ...
Hydrothermal carbonization (HTC)/liquefaction (HTL)/gasification (HTG) are promising processes for biofuel production from biomass containing high moisture. However, wastewater, the aqueous phase (AP) byproduct from these hydrothermal processes, is inevitably produced in large amounts. The AP contains >20% of the biomass carbon, and the total organic carbon in AP is as high as 10-20 g/L. The treatment and utilization of AP are becoming a bottleneck for the industrialization of hydrothermal technologies. The major challenges are the presence of various inhibitory substances and the high complexity of AP. Bioenergy recovery from AP has attracted increasing interest. In the present review, the compositions and characteristics of AP are first presented. Then, the progress in recovering bioenergy from AP by recirculation as the reaction solvent, anaerobic digestion (AD), supercritical water gasification (SCWG), microbial fuel cell (MFC), microbial electrolysis cell (MEC), and microalgae cultivation is discussed. Recirculation of AP as reaction solvent is preferable for AP from biomass with relatively low moisture; AD, MFC/MEC, and microalgae cultivation are desirable for the treatment of AP produced from processing biomass with low lignin content at relatively low temperatures; SCWG is widely applicable but is energy-intensive. Finally, challenges and corresponding strategies are proposed to promote the development of AP valorization technologies. Comprehensive analysis of AP compositions, clarification of the mechanisms of valorization processes, valorization process integration detoxification of AP, polycultures and co-processing of AP with other waste, enhancement in pollutant removal, scaling-up performance, and the techno-economic analysis and life-cycle assessment of valorization systems are promising directions in future investigations.
... To better understand the nature of the organic matter transformations through the presence and dynamics of functional groups, FTIR analysis of the raw and digested lettuce waste solids was performed (Fig. 3). Peaks were identified based on the literature (Christou et al. 2018;Dogan et al. 2007;Marcato et al. 2009;Mau et al. 2016). The difference between the FTIR results for raw and digested lettuce waste was in the formation of a wide peak in the range of 1520-1440 cm −1 for the latter, which could be assigned to the carboxylic acid derivatives. ...
Aquaponics plant waste, such as the non-edible parts of many vegetable crops, can be a source of environmental pollution, while its treatment might cause an economic burden. Therefore, efficient use of this waste would be advantageous.This study aimed at investigating anaerobic digestion of aquqponic lettuce waste to recover nutrients and energy through biogas production. A 700 L commercial anaerobic system was used to treat lettuce wastes from an aquaponic farming system that operated under desert climate and steady-state conditions. Digestion efficiency of the lettuce waste was 90.1% by weight, producing a maximum biogas volume of 0.65 m3/kg dry weight per day. Biogas composition contained on average 59.2% methane and 38.9% CO2 with only negligible hydrogen sulfide content. Moreover, the supernatant from the anaerobic digester contained elevated nutrient concentrations (N, P, K, Ca, and Fe), which can potentially be used onsite as a fertilizer. Onsite anaerobic digestion of lettuce plant waste from the aquaponic system under summer desert conditions is demonstrated for the first time to efficiently reduce pollution burden, produce high-quality biogas, and recover nutrients.
Hydrothermal carbonization (HTC) represents elegant thermochemical conversion technology suitable for energy and resource recovery from wet biowaste, while the elemental nitrogen is bound to affect the HTC process and the properties of the products. In this review, the nitrogen fate during HTC of typical N-containing-biowaste were presented. The relationship between critical factors involved in HTC like N/O, N/C, N/H, solid ratio, initial N in feedstock, hydrothermal temperature and residence time and N content in hydrochar were systematic analyzed. The distribution and conversion of N species along with hydrothermal severity in hydrochar and liquid phase was discussed. Additionally, the chemical forms of nitrogen in hydrochar were elaborated coupled with the role of N element during hydrochar formation mechanism and the morphology features. Finally, the future challenges of nitrogen in biowaste involved in HTC about the formation and regulation mechanism of hydrochar were given, and perspectives of more accurate regulation of the physicochemical characteristics of hydrochar from biowaste based on the N evolution is expected.
The effect of hydrothermal pretreatment (HTP) of dewatered sewage sludge (DSS) under optimized hydrothermal conditions and the fate of carbon and phosphorus (P) during anaerobic digestion (AD) of hydrochar and process water were studied. The results showed that the methane yield reached 241 mL CH 4 /g COD when the hydrothermal conditions were 200°C-2 h-10% (A4), which was 78.28% higher than that without hydrothermal pretreatment (A0) and 29.62% higher than that of unoptimized A1 (140°C-1 h-5%). Protein, polysaccharides, and volatile fatty acids (VFAs) were the main hydrothermal products of DSS, and polysaccharides were first absorbed and utilized by microorganisms. By 3D-EEM analysis, tyrosine, tryptophan proteins, and fulvic acids decreased after HTP, but the content of humic acid-like substances increased, and this phenomenon was more obvious after AD. A lag phase in protein degradation occurred during AD while polysaccharides are degraded first. The solid-organic P is converted into liquid-P in the hydrothermal process, and non-apatite inorganic P is converted to organic P during AD. A lower methane production rate occurred in the early AD, suggesting that the inoculum needed some time to adapt to the substrate. Microbial analysis showed that the composition of the microbial community of anaerobic degradation was different due to the various organic components.
Hydrothermal liquefaction (HTL) is identified as a promising thermochemical technique to recover biofuels and bioenergy from waste biomass containing low energy and high moisture content. The wastewater generated during the HTL process (HTWW) are rich in nutrients and organics. The release of the nutrients and organics enriched HTWW would not only contaminate the water bodies but also lead to the loss of valued bioenergy sources, especially in the present time of the energy crisis. Thus, biotechnological as well as physicochemical treatment of HTWW for simultaneous extraction of valuable resources along with reduction in polluting substances has gained significant attention in recent times. Therefore, the treatment of wastewater generated during the HTL of biomass for reduced environmental emission and possible bioenergy recovery is highlighted in this paper. Various technologies for treatment and valorisation of HTWW are reviewed, including anaerobic digestion, microbial fuel cells (MFC), microbial electrolysis cell (MEC), and supercritical water gasification (SCWG). This review paper illustrates that the characteristics of biomass play a pivotal role in the selection process of appropriate technology for the treatment of HTWW. Several HTWW treatment technologies are weighed in terms of their benefits and drawbacks and are thoroughly examined. The integration of these technologies is also discussed. Overall, this study suggests that integrating different methods, techno-economic analysis, and nutrient recovery approaches would be advantageous to researchers in finding way for maximising HTWW valorisation along with reduced environmental pollution.
Intensive growth of poultry production leads to generation of a large-scale accumulation of wastes, which is a critical concern for poultry farming. An environmentally friendly and effective solution is still being sought for sustainable management of poultry manure. In this study, evaluation of poultry manure both as a carbon source for production of solid fuels and activated carbon and as a phosphorus source has been investigated. The study focuses on the following: (1) biochar and hydrochar production under different process conditions for production of carbon-rich fuel from poultry manure; (2) phosphorus recovery by acid leaching-alkali precipitation from manure ash, biochar, and hydrochar; and (3) activated carbon production from acid-leached hydrochar and biochar. The results reveal that production of biochar and hydrochar is not a promising method for upgrading laying hen manure into an energy-dense solid fuel. Phosphorus in ash and chars was recovered as amorphous calcium phosphate with yields of 57.3-48.5% by acid leaching-alkali precipitation. Untreated and acid-leached chars were subjected to a chemical activation process with KOH and ZnCl2 to produce activated carbon. Due to the catalytic effect of inorganics in chars, the KOH activation resulted in a very low yield of activated carbon. The surface areas of activated carbons prepared using ZnCl2 were comparable to activated carbons derived from typical biomass using ZnCl2.
The best available technique (BAT) for managing the organic fraction of municipal solid waste (OFMSW) is represented by anaerobic digestion (AD) and subsequent composting. This research explored a new industrial model in the framework of the C2Land international project, with the insertion of hydrothermal carbonization (HTC) as a post-treatment for OFMSW digestate. The reaction was set for 3 h at three different temperatures (180 ÷ 220 °C); the wet solid hydrochar obtained after filtration was then co-composted with greenery waste as a bulking agent and untreated OFMSW digestate in four different proportions in bench-scale bioreactors. The hydrochars and the hydrochar co-composts were suitable for agro-industrial applications, while the HTC liquors were tested in biochemical methane potential (BMP) for internal recirculation to AD. The scenarios proposed can be beneficial for plant enhancement and increased biogas production. This study reports results connected to the production phase. Mass balances confirmed that, during HTC, phosphorus precipitated into the solid products, organic nitrogen partially mineralized into ammonium, and oxidizable organic matter solubilized. The selected hydrochar obtained at 200 °C had mean (dry) solid, liquid, and gaseous yields equal to 77, 20, and 3 %db, respectively. The dynamic respirometric index (DRI) confirmed that the reproduced BAT for the composting process was effective in producing high-quality hydrochar co-composts in terms of biological stability. The BMP tests on HTC liquors showed some inhibitory effects, suggesting the need for future studies with inoculum adaptation and co-digestion, to dilute toxic compounds and enhance biogas production. Part 2 of this study describes the agro-environmental properties of hydrochars and hydrochar co-composts, including the beneficial effect of composting on hydrochars phytotoxicity.
The demands on novel and sustainable techniques for vegetable waste (VW) valorization continues to increase during the past few decades due to the growing waste production under the flourishing vegetable industries. In this study, Chinese cabbage residues were hydrothermal carbonization (HTC) at 180, 200, 220 and 240 °C for 2 to 6 h to explore the impacts of process parameters on the characteristics of hydrochars and hydrolysates and their feasibility in sustainable agriculture. Results indicated that hydrothermal temperature had a greater impact on cabbage residue hydrolysis than the residence time. With the rising reaction severity, hydrochars became more alkaline with higher amount of ash and carbon (C), while the pH and dissolved organic nitrogen (DON) and NH4⁺-N in the hydrolysate were gradually reduced. The thermogravimetric analysis (TG-DTG) indicated that organic constitutions in the feedstock went through incomplete decomposition. Although the recalcitrance index (R50) steadily increased through HTC (0.37–0.46), hydrochars were unstable and would not applicable for carbon sequestration. Furthermore, hydrochars and hydrolysate would be optimal media for plants seedling and growth for the abundant nutrients and dissolved organic compounds but reduced phytotoxicity. In conclusion, these results showed that HTC is highly applicable for vegetable waste management for sustainable agriculture.
Thermochemical processing technologies such as hydrothermal liquefaction/carbonization/gasification, pyrolysis, torrefaction, and gasification have been widely used for the production of oil, char, and gas fuels from biomass. However, aqueous phase (AP), a co-product or process wastewater with high concentrations of carbon, nitrogen, phosphorus, and other elements, is inevitably produced in massive amounts after thermochemical treatment. The treatment and utilization of AP is one of the bottlenecks for the industrialization of biomass processing technologies. In this review, the production and characteristics of AP from dry and wet thermochemical processes were compared. Various AP valorization pathways were comprehensively discussed, including (i) the direct utilization of AP as a solvent, reaction medium, or a culture nutrient source for the cultivation of organisms such as microalgae; (ii) the separation and purification of nutrients such as struvite or chemicals such as carboxylic acids from AP, and (iii) the conversion of AP components to energy and fuels such as bioelectricity, biohydrogen, biogas, syngas, bioethanol, or chemicals such as polyhydroxyalkanoates (PHAs) through fermentation, anaerobic digestion, microbial electrolysis cells, microbial fuel cells, supercritical water gasification, and catalytic reforming. Finally, various strategies have been proposed to promote future research, including matching AP with preferable valorization technology, tuning AP compositions and properties (e.g., detoxification of AP), and process optimization and integration. This review could also be conducive to promoting the utilization of organic wastewater from other sources.
Hydrothermal carbonization (HTC) was employed for the conversion of the spent mushroom substrate (SMS) into a carbonaceous hydrochar. The effect of operating temperature (180, 200, 220, 240, and 260 °C) on the physicochemical, structural, and combustion properties of the obtained hydrochars was analyzed. The HTC treatment caused the increase of the higher heating value (HHV) and the lower heating value (LHV) of hydrochars for 58% and 65% in comparison with SMS, respectively. Analysis of morphology and functional groups showed the formation of microspheres and cracks on the hydrochar surface, which are predominantly dominated by aromatic and oxygen-rich functional groups. Thermal and kinetics analysis showed that HTC treatment improves the combustion behavior of the obtained solids. Combustion kinetic parameters of SMS and hydrochars were determined by the methods of Kissenger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO). The thermodynamic parameters and pre-exponential factors reveal a complex mechanism of SMS and hydrochars decomposition process.
The amount of household solid waste (HSW) has been significantly increasing due to a rapid population growth and economic development. HSW management is immensely sensitive and complicated problem not only in rapidly developing countries like Uzbekistan but also in developed countries with advanced economies.The accumulated waste has been causing a number of serious environmental problems such as release of the most dangerous greenhouse gases (CO 2 , N 2 O, CH 4) in the atmosphere which misbalance radiation in a planet's atmosphere causing a global warming. However, this waste can be friendly in terms of its potential to be used as energy source. HSW into energy conversion technologies has been playing a vital rolein order to successfully address global challenges suchas fossil fuel dependency, emission control and waste management issues.The most promising technology for conversions can be performed using thermochemical processes (e.g., pyrolysis or gasification).These thermochemical technologies can be used to convert solid waste into liquid and gaseous fuels, and this has already been studied sufficiently by other researchers. This article recommends a novel concept for intensification of value-added solid and liquid products recovery from HSW using hydrothermal carbonization and plasma treatment.
In order to meet the needs of modern people for protein food, livestock farming has developed rapidly. In the process of livestock breeding, a great deal of livestock manure will be produced, and the number of livestock manure is growing rapidly every year. Safe, economical, and effective treatment of livestock manure is a crucial link affecting the sustainable development of livestock breeding industry. Hydrothermal carbonization is an available technology for livestock manure treatment, which could transform livestock manure into hydrochar and solve the environmental pollution problem of livestock manure at the same time, such as odor, pathogens, greenhouse gas emission, and water/soil pollution. Hence, the study of hydrothermal carbonization of livestock manure has attracted extensive attention from researchers all over the world in recent years.
In this study, microwave-assisted hydrothermal carbonization of pig feces is investigated. The yield of hydrochar decreases with increasing reaction temperature/time, while it increases with rising solid-liquid ratio. The addition of CaO raises the yield of hydrochar, while the use of H2SO4 reduces the yield of hydrochar. Under non-catalytic conditions or with CaO as catalyst, most of P and heavy metals (Zn, Cr, Cu, Cd, Pb, and Ni) are retained in hydrochar, while large amounts of K/N are migrated into process water. In the presence of H2SO4, the migration of P and heavy metals (except Cu) into process water is significantly enhanced. Compared to raw pig feces, hydrochars exhibit higher thermal stability and porosity, and contain lower contents of soluble N/P/K nutrients. Direct use/discharge of process water is restricted by it’s high contents of COD, nutrients and some heavy metals (i.e., Zn and Cr), which needs further treatment.
Manure conversion into energy products via hydrothermal liquefaction was studied. Hydrothermal reactions, conducted at different temperatures (200–300°C), were compared on the basis of conversion yields, carbon and energy recoveries and products' quality. The results demonstrate how reaction temperatures affect the relative production of biocrude oil and hydrochar. A comprehensive analyses of both biocrude oil and hydrochar suggest that decarboxylation was the dominant mechanism involved in the reaction and was enhanced with temperature. With relatively high carbon (67–74%) and low oxygen (13¬¬–18%), biocrude oil seems to provide a better platform to deliver recovered energy, with higher heating values of 30–35 MJ/kg. An overall energy balance, supported by a sensitivity analysis demonstrated how the higher temperature enhanced the overall energy return. Twelve scenarios were used to estimate the daily net energy gained in feedlots of different sizes. All scenarios provided a positive energy balance with returned energy, found to be 2 to 3 times higher than invested energy. The estimation presented herein, highlights the feasibility of the hydrothermal technology to return energy by multiple products and hence, to provide a sustainable waste management practice in confined feedlots.
Current ways of managing spent coffee grounds (SCGs) are uneconomical and have significant environmental impacts. Alternative approaches, such as hydrothermal carbonisation (HTC), which can utilise their rich organic matter for energy recovery purposes are essential. Here we present, a response surface methodology (RSM) for understanding the combined interactive effects due to the main HTC operating conditions, i.e. reaction temperature and residence time, as well as optimising them to produce hydrochar from SCGs of maximal yield and calorific value. The fuel properties and combustion behaviours of hydrochar were further evaluated to assess its suitability to replace coals for energy applications. Depending on the operating conditions, the atomic carbon content and calorific values of the hydrochar were significantly improved: by 11.2–30.7% and 15.8–44.7% respectively. The highest hydrochar calorific value recorded, 33.5 MJ kg⁻¹, resembled that of anthracite and dry steam coal, generally used in the UK. At optimal conditions of ∼216 °C and 1hr - guided by the RSM - a maximal hydrochar yield of ∼64% and a calorific value of 31.6 MJ kg⁻¹ are feasible. Using this as a benchmark, the 500,000 tonnes of SCGs generated annually in the UK has the potential of replacing 4.4% of the coal used for electricity generation in the country.
Hydrothermal carbonization (HTC) is a promising technology for the treatment of swine manure (SM). In this study, the effects of main process parameters on the yield/properties of hydrochar and process water are investigated. In view of the mass/energy yield of hydrochar, the suitable reaction temperature, solid-liquid ratio and reaction time are 260 ℃, 0.1 g/mL and 30 min, respectively. At the above conditions, the yield and caloric value of hydrochar reach 53.2 wt.% and 15.9 MJ/kg, respectively. After HTC, the phosphorus and heavy metals contained in raw SM are accumulated in hydrochars. The contents of total P in hydrochars obtained at 220–280 ℃ increase by 11.3–33.6%, compared to that in raw SM. However, the contents of soluble P and leachable heavy metals in hydrochars both significantly decrease, especially for soluble P (reducing by 79.1–98.5%). Interestingly, only about 26.9–39.8% of N and 25.3–30.0% of K contained in raw SM are retained in hydrochars after HTC, with the rest entering into the liquid phase (process water). The COD and chroma values of process water reduce from 13.6 g/L to 6.5 g/L and from 13,000° to 3571° with increasing reaction temperature (200–280 ℃), respectively. The process water contains a mass of N, K, and organic C, and also a small amount of P. Both hydrochar and process water have agronomic fertilizer value, but attention should be paid to the pollution risk of heavy metals.
Co-hydrothermal carbonization (Co-HTC) has been reported as a potential technology for enhancing fuel qualities and subsequent combustion behaviors of high-moisture raw biowastes or coals. For the purpose of real energy utilization, two low-fuel-quality materials, sewage sludge (SS, a biowaste) and lignite (LC, a coal), were employed to explore the characteristics and capabilities of target hydrochars produced from Co-HTC of their mixture (1:1 mass ratio) in a temperature range from 120-300 °C. The results demonstrated that the hydrochars exhibited excellent synergistic characteristics, such as more fixed carbon, less volatile matter, an enhanced higher heating value, and an improved coalification degree (lower O/C and H/C ratios), which was probably explained by that the involved dehydration, decarboxylation, and aromatization reactions can be enhanced by the mutual interactions between SS and LC during Co-HTC process. Furthermore, the combustion of hydrochars was observed to have maximal synergistic capabilities at approximately 240 °C with a corresponding deviation value of -21.96% and a comprehensive combustion index of 10.28×10-8 min-2·°C-3. These findings, which are related to the synergistic effects of Co-HTC technique, could indicate a feasible approach for the effective energy utilization of low-fuel-quality raw biowastes or coals.
The biorefinery is an important approach for the current needs of energy and chemical building blocks for a diverse range of applications, that gradually may replace current dependence on fossil-fuel resources. Among other primary renewable building blocks, 5-hydroxymethylfurfural (HMF) is considered an important intermediate due to its rich chemistry and potential availability from carbohydrates such as fructose, glucose, sucrose, cellulose and inulin. In recent years, considerable efforts have been made on the transformation of carbohydrates into HMF. In this critical review we provide an overview of the effects of HMF on microorganisms and humans, HMF production and functional group transformations of HMF to relevant target molecules by taking advantage of the primary hydroxyl, aldehyde and furan functionalities.
The poultry industry is one of the largest and fastest growing agro-based industries in the world. This can be attributed to an increasing demand for poultry meat and egg products. However, a major problem facing the poultry industry is the large-scale accumulation of wastes including manure and litter which may pose disposal and pollution problems unless environmentally and economically sustainable management technologies are evolved. Most of the litter produced by the poultry industry is currently applied to agricultural land as a source of nutrients and soil amendment. However environmental pollution, resulting from nutrient and contaminant leaching can occur when poultry litter is applied under soil and climatic conditions that do not favour agronomic utilisation of the manure-borne nutrients. This review examines the composition of poultry litter in relation to nutrient content and environmental contaminants, its value as a nutrient source, soil amendment, animal feed and fuel source, and cost-effective innovative technologies for improving its value. Poultry litter provides a major source of nitrogen, phosphorus and trace elements for crop production and is effective in improving physical and biological fertility, indicating that land application remains as the main option for the utilisation of this valuable resource. The alternative use of poultry litter; as an animal feed and fuel source, is limited by contaminants, and high moisture content, respectively. The review proposes best management practices to mitigate environmental consequences associated with air and water quality parameters that are impacted by land application in order to maintain the continued productivity, profitability, and sustainability of the poultry industry.
A chemical process, hydrothermal carbonization (HTC) of low value biomass, is discussed as a tool for the sequestration of atmospheric CO 2 . Via the available biomass, CO 2 can be transformed into an efficient deposited form of carbon, i.e. hardly degradable peat or carbonaceous soil. Currently, world crude oil production amounts to about 4 billion tons or 4 km 3 per year (official energy statistics of the US Government, http://www.eia.doe.gov/ipm/supply.html). Assuming a price of US-$70 a barrel, this corresponds to a value of US-$1.76 trillion. As, essentially, all oil ends up— sooner or later—as CO 2 in the earth's system, the opposite side of this economy is the generation of an excess 12.5 billion tons of CO 2 per year, with the known implications on the world climate. The conventional discussion for handling this problem is to replace a minor part of the fuel and/or energy production by biomass schemes. This considers—beside direct combustion— the fermentation of carbohydrates to ethanol fuels, the cultiva-tion of oil seeds (''biodiesel''), or the generation of biogas via anaerobic digestion. 1 A very detailed analysis of the energy efficiencies, costs and biological impacts of such procedures was published by Gustavsson et al. as early as 1995. 2 For many years, sugarcane has been converted into ethanol in Brazil, replacing oil as a car fuel, which, however, turned out to be a highly inefficient process. Other countries, e.g. Sweden, try to become completely independent of oil imports through ''second generation'' biomass use, thus not only meeting their energy demand, but also significantly improving their CO 2 liberation footprint. However, in this context, it should be stated that biological fuel production schemes can only lower future increases in CO 2 emission, and cannot compensate for past and currently emitted CO 2 from fossil resources. Concerning climate change and the role of CO 2 therein, it would therefore be highly desirable to not only slow down further CO 2 emissions but also invert current development by sequestering the atmospheric CO 2 of past years of industrializa-tion. Not only is biomass a ''zero emission'' energy source, it also has the potential to generate a new chemical ''CO 2 disposal'' industry. This thought, as simple as it is, is only rarely accepted as a prerequisite for discussion. It also means that the search for new and efficient carbon deposits has to be perpetuated from a chemistry point of view. The biggest carbon converter, with the highest efficiency to bind CO 2 from the atmosphere, is certainly biomass. A rough estimate of terrestrial biomass growth amounts to 118 Â 10 9 tons per year, when calculated as dry matter. 3,4 Biomass, however, is just a short term, temporary carbon sink, as microbial decomposition liberates exactly the amount of CO 2 formerly bound in the plant material. Nevertheless, as biomass contains about 0.4 mass equivalents of carbon, removal of 8.5% of the freshly produced biomass from the active geosys-tem would indeed compensate for the complete CO 2 liberation from oil, all numbers calculated per year. To make biomass ''effective'' as a carbon sink, the carbon in it has to be fixed by ''low-tech'' operations. Coal formation is certainly one of the natural sinks that has been active in the past on the largest scale. Natural coalification of biomass takes place on a timescale of some hundred (peat) to hundred million (black coal) years. Due to its slowness, it is usually not considered in renewable energy exploitation schemes or as an active sink in CO 2 cycles. Never-theless, it is obvious that carbon fixation into coal is a lasting effort, as brown or black coal (on the contrary to peat) are obviously practically not biodegradable. The question of coa-lified carbon destabilization is, however, currently accessed in more detail. 5 Sufficient condensation of the carbon scaffold is, in any case, mandatory for the purposes of carbon fixation. It is therefore the purpose of this contribution to discuss the feasibility of turning coal formation into an active element of carbon sequestration schemes, simply by accelerating the under-lying coalification processes by chemical means. The natural process of peat or coal formation is presumably not biological but chemical in its nature. 6 As ''coaling'' is a rather elemental experiment, coals and tars have been made and used by mankind since the Stone Age, and one can find trials to imitate carbon formation from carbohydrates with faster chemical processes in the modern scientific literature. In this context, it is an exciting observation of soil research that the Indians of the Amazon basin used locally generated charcoal for the improve-ment of soil quality for hundreds of years (i.e. improving the water and ion binding of ''rich black'' soil) and that this carbon fraction was not easily decomposed. 7,8 Besides ''charcoal formation,'' which is performed with high quality, dry biomass only, hydrothermal carbonization (HTC)
Hydrothermal carbonization (HTC) is a novel thermochemical conversion process to convert lignocellulosic biomass into value-added products. HTC processes were studied using two different biomass feedstocks: corn stalk and Tamarix ramosissima. The treatment brought an increase of the higher heating values up to 29.2 and 28.4 MJ/kg for corn stalk and T. ramosissima, respectively, corresponding to an increase of 66.8% and 58.3% as compared to those for the raw materials. The resulting lignite-like solid products contained mainly lignin with a high degree of aromatization and a large amount of oxygen-containing groups. Liquid products extracted with ethyl acetate were analyzed by gas chromatography-mass spectrometry. The identified degradation products were phenolic compounds and furan derivatives, which may be desirable feedstocks for biodiesel and chemical production. Based on these results, HTC is considered to be a potential treatment in a lignocellulosic biomass refinery.
Supplies of good quality irrigation water are expected to decrease in the future because the development of new water supplies will not keep pace with the increasing water needs of industries and municipalities. Thus, irrigated agriculture faces the challenge of using less water, in many cases of poorer quality, to provide food and fiber for an expanding population. Some of these future water needs can be met by using available water supplies more efficiently, but in many cases it will prove necessary to make increased use of municipal wastewaters and irrigation drainage waters. Aside from increased levels of nitrogen, phosphorus, and potassium, the salinity (total salt content) and sodicity (sodium content) of these waters will be higher than that of the original source water because of the direct addition of salts to the water and the evapoconcentration that occurs as water is used. While the use of these waters may require only minor modifications of existing irrigation and agronomic strategies in most cases, there will be some situations that will require major changes in the crops grown, the method of water application, and the use of soil amendments.Use of poor quality waters requires three changes from standard irrigation practices: (1) selection of appropriately salt-tolerant crops; (2) improvements in water management, and in some cases, the adoption of advanced irrigation technology; and (3) maintenance of soil-physical properties to assure soil tilth and adequate soil permeability to meet crop water and leaching requirements (LR). This paper looks at farmers' experiences, research, and computer modelling in these areas, and concludes with a discussion of examples of farm experiences with waters that caused problems with infiltration rates and soil tilth and the practices used to mitigate these problems.
The carbonization of biomass residuals to char has strong potential to become an environmentally sound conversion process for the production of a wide variety of products. In addition to its traditional use for the production of charcoal and other energy vectors, pyrolysis can produce products for environmental, catalytic, electronic and agricultural applications. As an alternative to dry pyrolysis, the wet pyrolysis process, also known as hydrothermal carbonization, opens up the field of potential feedstocks for char production to a range of nontraditional renewable and plentiful wet agricultural residues and municipal wastes. Its chemistry offers huge potential to influence product characteristics on demand, and produce designer carbon materials. Future uses of these hydrochars may range from innovative materials to soil amelioration, nutrient conservation via intelligent waste stream management and the increase of carbon stock in degraded soils.
The land disposal of waste from the poultry industry and subsequent environmental implications has stimulated interest into cleaner and more useful disposal options. The review presented here details advances in the three main alternative disposal routes for poultry litter, specifically in the last decade. Results of experimental investigations into the optimisation of composting, anaerobic digestion and direct combustion are summarised. These technologies open up increased opportunities to market the energy and nutrients in poultry litter to agricultural and non-agricultural uses. Common problems experienced by the current technologies are the existence and fate of nitrogen as ammonia, pH and temperature levels, moisture content and the economics of alternative disposal methods. Further advancement of these technologies is currently receiving increased interest, both academically and commercially. However, significant financial incentives are required to attract the agricultural industry.
Supplies of good quality irrigation water are expected to decrease in the future because the development of new water supplies will not keep pace with the increasing water needs of industries and municipalities. Thus, irrigated agriculture faces the challenge of using less water, in many cases of poorer quality, to provide food and fiber for an expanding population. Some of these future water needs can be met by using available water supplies more efficiently, but in many cases it will prove necessary to make increased use of municipal wastewaters and irrigation drainage waters. Aside from increased levels of nitrogen, phosphorus, and potassium, the salinity (total salt content) and sodicity (sodium content) of these waters will be higher than that of the original source water because of the direct addition of salts to the water and the evapoconcentration that occurs as water is used. While the use of these waters may require only minor modifications of existing irrigation and agronomic strategies in most cases, there will be some situations that will require major changes in the crops grown, the method of water application, and the use of soil amendments. Use of poor quality waters requires three changes from standard irrigation practices: (1) selection of appropriately salt-tolerant crops; (2) improvements in water management, and in some cases, the adoption of advanced irrigation technology; and (3) maintenance of soil-physical properties to assure soil tilth and adequate soil permeability to meet crop water and leaching requirements (LR). This paper looks at farmers' experiences, research, and computer modelling in these areas, and concludes with a discussion of examples of farm experiences with waters that caused problems with infiltration rates and soil tilth and the practices used to mitigate these problems.
In this study, hydrochars were prepared by hydrothermal carbonisation (HTC) of poultry litter (PL) at temperatures between 150-300 °C with residence times of 30, 120 and 480 minutes. The effects of treatment temperature and residence time on the yield and composition of hydrochar were investigated. Both treatment temperature and residence time effects were observed however, the effect of residence time was lower. The results indicated that the HHV was improved by up to 25.17% and the overall ash in hydrochar was significantly lower compared to PL, however this coincided with a lower hydrochar yield.
Thermal hydrolysis and hydrothermal processing show promise for converting biomass into higher energy density fuels. Both approaches facilitate the extraction of inorganics into the aqueous product. This study compares the behaviour of microalgae, digestate, swine and chicken manure by thermal hydrolysis and hydrothermal processing at increasing process severity. Thermal hydrolysis was performed at 170°C, hydrothermal carbonisation (HTC) was performed at 250°C, hydrothermal liquefaction (HTL) was performed at 350°C and supercritical water gasification (SCWG) was performed at 500°C. The level of nitrogen, phosphorus and potassium in the product streams was measured for each feedstock. Nitrogen is present in the aqueous phase as organic-N and NH3-N. The proportion of organic-N is higher at lower temperatures. Extraction of phosphorus is linked to the presence of inorganics such as Ca, Mg and Fe in the feedstock. Microalgae and chicken manure release phosphorus more easily than other feedstocks.
The hydrothermal (HT) conversion has been proposed to produce nitrogen, chlorine free solid biofuel or liquid fertilizer from high moisture and nitrogen content bio-wastes, such as municipal solid waste (MSW), mycelial waste, sewage sludge and paper sludge. However, the energy and economic efficiency of this process has not been fully investigated yet. This work focuses on energy recycling from sewage sludge by producing solid biofuel with HT carbonization, in order to optimize the operating parameters and evaluate the energy efficiency of this fuel production process. The effect of the HT temperature and holding time on the biofuel recovering ratio, calorific value and energy recovery rate was investigated. This evaluation fully considered the effect of the HT conditions, mechanical dewatering, thermal drying, and biofuel recovery ratio. Moreover, the energy consumption of sludge thermal drying was introduced to illustrate the economic efficiency of the HT biofuel production process more intuitively. The results show that the HT biofuel production process was more cost-effective than the conventional thermal drying. The HT temperature was the most important parameter to affect the biofuel properties. The carbon content of solid biofuel kept increasing both with HT temperature and holding time, resulting in an increase in the calorific value of biofuel; whereas, the biofuel recovering ratio a, defined as the mass ratio of solid biofuel to raw sludge, also dropped causing a reduction in the energy recovery rate. After the HT temperature was above 200 degrees C, the energy recovery rate was around 40%. A moderate condition-HT temperature of 200 degrees C and holding time of 30 min was suggested to produce solid biofuel from sewage sludge with an energy recovery rate of 50%. Practically, it is better to improve the intensity of mechanical dewatering to remove more water from the HT products in order to improve thermal efficiency.
Food waste collected from restaurants, convenience stores, and food-processing factories was mixed with sawdust and subjected to hydrothermal pretreatment at 180 °C for 30 min to prepare compost raw material. Furan compounds such as 5-HMF (5-hydroxymethyl furfural) and furfural were produced at concentration levels of approximately 8 and 0.5 mg/g-ds, respectively, through hydrothermal pretreatment. The furan compounds inhibited the activity of composting microorganisms, thus delaying the start of organic matter degradation during composting. A newly identified fungus, Paecilomyces sp. FA13, which possesses the ability to degrade furan compounds, was isolated and used as an inoculum for the composting of the raw material prepared by hydrothermal pretreatment. By inoculating the FA13 into the compost raw material at 105 CFU/g-ds, the degradation of furan compounds was accelerated. As a result, bacterial activity, which contributed to composting, was enhanced, significantly promoting the start of vigorous degradation of organic materials.
Hydrothermal carbonisation of primary sewage sludge was carried out using a batch reactor. The effect of temperature and reaction time on the characteristics of solid (hydrochar), liquid and gas products, and the conditions leading to optimal hydrochar characteristics were investigated. The amount of carbon retained in hydrochars decreased as temperature and time increased with carbon retentions of 64-77% at 140 and 160°C, and 50-62% at 180 and 200°C. Increasing temperature and treatment time increased the energy content of the hydrochar from 17 to 19MJ/kg but reduced its energy yield from 88% to 68%. Maillard reaction products were identified in the liquid fractions following carbonisations at 180 and 200°C. Theoretical estimates of the methane yields resulting from the anaerobic digestion of the liquid by-products are also presented and optimal reaction conditions to maximise these identified.
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Projected shortages of global phosphate have prompted investigation of methods that could be employed to capture and recycle phosphate, rather than continue to allow the resource to be essentially irreversibly lost through dilution in surface waters. Hydrothermal carbonization of animal manures from large farms was investigated as a scenario for reclamation of phosphate for agricultural use and to mitigate the negative environmental impact of phosphate pollution. Hydrothermal reaction conditions were identified for poultry, swine, and cattle manures that resulted in hydrochar yields of 50 - 60% for all three manures, and > 90% of the total phosphorus present in these systems was contained in the hydrochars as precipitated phosphate salts. Phosphate recovery was achieved in yields of 80 - 90% by subsequent acid treatment of the hydrochars, addition of base to acid extracts to achieve pH 9, and filtration of principally calcium phosphate. Overall reclamation yields of phosphate achieved were in the range of 81-87% based on starting manures. Swine and cattle manures produced hydrochars with combustion energy contents comparable to high end sub-bituminous coals.
Process waters obtained from hydrothermal carbonization (HTC) of wheat straw, a biogas digestate derived thereof, and four woody biomass feedstocks were quantified regarding the total organic carbon (TOC) and selected organic compounds. HTC runs revealed that TOC loads were largely unaffected by process severity or type of feedstock whereas the C2–C6 fatty acids, determined by GC, displayed clear effects of temperature and feedstock. HPLC demonstrated simultaneously the initial increase and subsequent consumption of cellulose-derived furfural and 5-hydroxymethylfurfural as well as the increase of the lignin-derived 2-methoxyphenol. 2-Methylbenzofuran, an example for a substance potentially harmful to aquatic biota, was observed in high concentration in the HTC liquor from wheat straw-based feedstocks.
The high fertilizer demand for biodiesel production from microalgae is a significant challenge facing the commercialization of this promising technology. We investigated a processing strategy called hydrothermal carbonization (HTC) to convert wet algal biomass into a lipid-rich hydrochar and aqueous phase (AP) co-product. By reacting biomass at 200°C for 15 min, about 50% of the algae biomass became a solid hydrochar and roughly 40–70% of the C, N, and P in the reactant material dissolved into the AP. For the first time, an AP co-product of this nature was analyzed by HPLC, GC-MS and FT-ICR-MS to identify and characterize the dissolved organic matter. Using a unique marine bi-culture suspected to contain a green algae (Nannochloris) and a cyanobacteria (Synechocystis), we demonstrated that this AP co-product can support biomass growth better than a medium containing only inorganic nutrients. To manage unwanted contamination and optimize AP utilization, we employed a two-stage growth process and fed-batch additions of the AP co-product. The effect of media recycling and nutrient supplementation, as well as a production model for a large-scale facility, are discussed. Our work suggests that HTC can play a critical role in making algal biorefineries more sustainable by obviating biomass drying for fuel processing and recycling nutrients. © 2013 American Institute of Chemical Engineers Environ Prog, 32: 962–975, 2013
Biomass charcoal is dominantly made from lignin. It is necessary to study lignin carbonization process to improve the quality of biomass charcoal. A Thermo-Gravimetric Analyzer coupled with a Fourier Transform Infrared Spectrometry (TG-FTIR) was applied to investigate the kinetics of lignin carbonization. Three mass loss stages (drying, pyrolysis and carbonization) were observed below 900 °C and another stage (structural rearrangement stage) with a slight mass loss was noticed between 900 and 1200 °C. Charcoal obtained at different temperatures was analyzed by FTIR to track the variation of functional groups. The pyrolysis of lignin started at 200 °C and charcoal was initially formed till 500 °C together with the intensive evolution of volatiles including various phenyl compounds. Amorphous carbon was formed between 500 and 900 °C, while most benzene rings structures were transformed into aromatic structures with emission of CO. When the temperature increased from 900 °C to 1400 °C, most CC bonds were cleaved and a new charcoal structure, between amorphous carbon and graphite structures, was probably formed. The activation energies of the above three stages were estimated to be 54 kJ/mol, 70 kJ/mol and 178 kJ/mol.
Hydrothermal technologies are broadly defined as chemical and physical transformations in high-temperature (200–600 °C), high-pressure (5–40 MPa) liquid or supercritical water. This thermochemical means of reforming biomass may have energetic advantages, since, when water is heated at high pressures a phase change to steam is avoided which avoids large enthalpic energy penalties. Biological chemicals undergo a range of reactions, including dehydration and decarboxylation reactions, which are influenced by the temperature, pressure, concentration, and presence of homogeneous or heterogeneous catalysts. Several biomass hydrothermal conversion processes are in development or demonstration. Liquefaction processes are generally lower temperature (200–400 °C) reactions which produce liquid products, often called “bio-oil” or “bio-crude”. Gasification processes generally take place at higher temperatures (400–700 °C) and can produce methane or hydrogen gases in high yields.
Separated manure solids were collected from three dairy farms with different solid-liquid separators to study the engineering properties of the material. The specific heat, thermal conductivity and mean dry particle density of the solids were determined. Equations to estimate thermal diffusivity and air-filled porosity were also developed.
Hydrothermal carbonization (HTC) is a thermal conversion technique that converts food wastes and associated packaging materials to a valuable, energy-rich resource. Food waste collected from local restaurants was carbonized over time at different temperatures (225, 250 and 275°C) and solids concentrations to determine how process conditions influence carbonization product properties and composition. Experiments were also conducted to determine the influence of packaging material on food waste carbonization. Results indicate the majority of initial carbon remains integrated within the solid-phase at the solids concentrations and reaction temperatures evaluated. Initial solids concentration influences carbon distribution because of increased compound solubilization, while changes in reaction temperature imparted little change on carbon distribution. The presence of packaging materials significantly influences the energy content of the recovered solids. As the proportion of packaging materials increase, the energy content of recovered solids decreases because of the low energetic retention associated with the packaging materials. HTC results in net positive energy balances at all conditions, except at a 5% (dry wt.) solids concentration. Carbonization of food waste and associated packaging materials also results in net positive balances, but energy needs for solids post-processing are significant. Advantages associated with carbonization are not fully realized when only evaluating process energetics. A more detailed life cycle assessment is needed for a more complete comparison of processes.
This paper reviews information regarding the disposal of on-farm poultry wastes (manure, litter and dead birds) and the effects of poultry waste disposal on environmental quality. Waste composition and production rates are presented. Land disposal of the wastes and subsequent agronomic implications are extensively discussed, but alternative methods of disposal such as composting, biogas generation and others are presented as well. Results of experimental investigations into transformations of poultry waste constituents, particularly nitrogen, are summarized. Both surface and ground water quality are reviewed in relationship to customary methods of poultry waste disposal. The body of available literature is used as a basis for recommended future research, which includes more precise characterization of wastes, improved understanding of the dynamics of poultry waste constituents, and increased efforts to quantify and model water quality impacts of waste disposal.
Hydrothermal carbonization (HTC) is a pretreatment process for making a homogenized, carbon rich, and energy-dense solid fuel, called biochar, from lignocellulosic biomass. Corn stover, miscanthus, switch grass, and rice hulls were treated with hot compressed water at 200, 230, and 260 °C for 5 min. Mass yield is as low as 41% of the raw biomass, and decreases with increasing HTC temperature. Higher heating values (HHV) increase up to 55% with HTC pretreatment temperature. Up to 90% of calcium, magnesium, sulfur, phosphorus, and potassium were removed with HTC treatment possibly due to hemicellulose removal. At a HTC temperature of 260 °C, some structural Si was removed. All heavy metals were reduced by HTC treatment. The slagging and fouling indices are reduced with HTC treatment relative to that of untreated biomass. Chlorine content, a concern only for raw and HTC 200 switch grass, was reduced to a low slagging range at 230 °C, and 260 °C. Alkali index was medium for raw biomass but decreased by HTC.
The objective of this work was to evaluate the transformation characteristics of four organic substances in supercritical water. The purpose was to demonstrate the yield and stability of the acetic acid produced under hydrolytic and oxidative conditions. Other organic acids, such as formic, glycolic, and lactic acids, were monitored. Cellulose and coconut oil solutions, as well as brewery and dairy effluents, were used as feedstocks. Batch tests were performed at fixed conditions of 400 °C, 27.6 MPa, and 5 min of reaction time. Hydrogen peroxide was the oxidant. Under hydrolytic conditions, 70% of the initial carbon remained as the liquid product. On the contrary, in the presence of excess oxygen, there was a 95% conversion to the gaseous product. Typically, less than 15% of the initial total organic carbon was converted to the acids. The use of catalysts (i.e., TiO2) and additives (i.e., H2SO4) did not enhanced the organic acid yield. However, catalysts addition facilitated feedstock breakdown at lower oxygen levels. To evaluate the effect of alkali addition and the use of lower temperatures, continuous flow tests were conducted using glucose as the substrate. Under alkaline conditions, organic acid production increased. For example, at 250 °C and 27.6 MPa with the addition of NaOH (55.6 wt % glucose) and providing 25% stoichiometric oxygen, about 77% glucose was converted to acetic acid (17%), glycolic acid (22%), and formic acid (38%). These preliminary results indicate that valuable compounds could be obtained during the degradation of organic wastes in sub- and supercritical water instead of complete oxidation to CO2 and water.
Hydrothermal carbonization (HTC) of biomass involves contacting raw feedstock with hot, pressurized water. Through a variety of hydrolysis, dehydration, and decarboxylation processes, gaseous and water-soluble products are produced, in addition to water itself and a solid char. In this experimental effort, a 2 L Parr stirred pressure vessel was used to apply the HTC process to a mixed wood feedstock. The effects of the reaction conditions on product compositions and yields were examined by varying temperature over the range of 215−295 °C and varying reaction hold time over the range of 5−60 min. With increasing temperature and time, the amounts of gaseous products and produced water increased, while the amount of HTC char decreased. The energy density of the char increased with reaction severity. At reaction conditions of 255 °C for 30 min, the HTC char had 39% higher energy density than the raw biomass feedstock. Aqueous solutions from HTC experiments at lower temperatures (215−235 °C) contained significant levels of sugars. At higher temperatures (255−295 °C), greatly reduced concentrations of sugars were observed, while concentrations of acetic acid increased. A two-step HTC process involving low- and high-temperature regimes may be advantageous to maximize both the recovery of sugars and production of energy-dense char.
To determine optimum conditions for producing activated carbon and carbon black from biomass waste (i.e., chicken litter), studies have been performed on the thermal decomposition changes of chicken litter under a nitrogen atmosphere by evolved gas analysis (EGA) including thermogravimetric mass spectrometry (TG-MS), TG-fourier transform infrared (TG-FTIR), and pyrolysis-GC/MS. Samples were prepared by milling and sieving the as-collected chicken litter to obtain three kinds of samples differing in particle size distribution (sample A, above 140 mesh; sample B, 140−325 mesh; sample C, below 325 mesh). Samples A and C were found to show the two extremes in volatile matter to ash content ratios of 54/25% and 35/54%. Thus, to obtain carbon byproducts at a higher yield, decomposition of sample A in nitrogen was studied in particular, and it was found that the process can be roughly divided in four stages. The activation energy, E, was also obtained by kinetic analysis for each of the stages: (I) release of absorbed water and ammonia stemming from ammonium salts (25−160 °C), E = 100.6 kJ mol-1; (II) devolatilization of mainly lignin and hemicellulose, with evolution of sulfur compounds such as H2S (160−290 °C), E = 52.11 kJ mol-1; (III) devolatilization of mainly cellulose with evolution of N2O (290−390 °C), E = 193.9 kJ mol-1; and (IV) decomposition of cellulose (390−500 °C), E = 242.3 kJ mol-1. Activated carbon can be obtained after stage IV. Ammonia evolution in the lower-temperature regions was attributed to the release from ammonium salts, whereas that in upper-temperature regions was attributed to the decomposition of organic nitrogen compounds.