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A combination anaerobic digestion scheme for biogas production from dairy effluent—CSTR and ABR, and biogas upgrading
Abstract
Anaerobic digestion of low-strength dairy waste water was used for the production of biogas which is aimed at serving as a concentrated carbon dioxide (CO2) source for further methanation. Using hydrogen (which can be produced via electrolysis using renewably sourced electricity), the CO2 fraction of the produced biogas can be used as a mechanism to store surplus electricity by the Sabatier process, which converts the CO2 fractions to methane (CH4), i. e. synthetic natural gas. This study investigates the use a combined reactor scheme for the anaerobic digestion of dairy waste water, and the further upgrading of the biogas products from the process. A combination pilot scale process was established with a 90 d start-up time using a 1 m³ continuous stirred tank reactor (CSTR) and a 0.2 m³ baffled reactor (ABR) in series. The system was fed at constant retention time in the ABR of 1.6 d and with varying substrate organic loading rates between 1.25 and 4.50 kg m⁻³ d⁻¹. The average chemical oxygen demand (COD) removal was 82% with a biogas yield of 0.26 m³ kg⁻¹. The use of the derived biogas for the Sabatier process to convert hydrogen into CH4 showed no disadvantages compared to synthetic gas mixtures. The combination of CSTR and ABR overcame the individual disadvantages of both reactor types. The investigated anaerobic digestion system can be further optimized and adopted to replace conventional waste water treatment systems.
... In the dairy industry, a huge amount of water is utilized for manufacturing dairy products and so it generates a huge amount of effluents. Wastewater keeps developing at every stage of the process, including cleaning, washing, disinfecting, heating, and cooling (Lars et al., 2018). Generated WW can be treated with various methods such as biomethanation, reverse osmosis, anaerobic filter reactor, filtration performance, electrochemical technologies such as electrocoagulation, electrodeposition, electrofloatation, electro-oxidation, and biological and physiochemical methods such as ASP, aerated lagoons, trickling filters, UASB reactor, anaerobic filters, and SBRs. ...
... The average yield of biogas while using a CSTR and anaerobic baffled reactor system by taking dairy WW as a primary source was 0.264 m 3 /kg. The observed yield depends on how much COD is removed in the pretreatment of dairy WW (Lars et al., 2018). The effluents of dairy WW are low strength and they need to be treated in high rate anaerobic digester such as up-flow anaerobic sludge blanket reactor. ...
The effect on climate change of greenhouse gases from fossil fuel combustion has increased the need for clean and renewable biological energies necessary for the future. A substitution for fossil-based fuels may be renewable biofuel biogas from wastewater (WW), which has the tremendous potential to meet energy demand and minimize greenhouse gas emissions. In green energy production technology, WW is wildly attracted to biogas recovery because it has environmental and economic benefits from domestic to industrial sectors. Owing to the growth of human lifestyles, urbanization, construction of WW treatment plants, and environmental legislation, the discharge of WW with high organic strength has increased enormously in recent decades. The organics present in the WW could be transformed into biogas through biological or biochemical processes and also, the contaminants could be alleviated. The knowledge of WW to biogas conversion is crucial to improve bioenergy production with a reduced operating economy.
... Bioenergy with carbon capture and storage (BECCS) is seen as a more viable and cost-effective approach to achieve negative emissions over DAC, because it simultaneously generates energy as CO 2 is captured from the atmosphere from biomass growth (see Fig. 1 for energy balance of BECCS compared to other energy sources) [74,[78][79][80]. Biomass can be converted into energy in the form of heat, electricity or biofuels in different ways [81], including (i) chemical reactions such as etherification, esterification, hydrogenation and oligomerization [82][83][84], (ii) ethanol production by fermentation [85][86][87][88][89], (iii) anaerobic digestion (or biomethanation) [90][91][92][93][94][95][96], and (iv) thermal processes as combustion, gasification, pyrolysis, and torrefaction [97][98][99][100][101][102]. BECCS is mainly applied to provide carbon-negative energy by capturing CO 2 emission from the direct combustion of biomass to generate heat or electricity [103,104], as well as from fermentation [105] or gasification [106] of biomass to produce biofuels. ...
... BECCS is mainly applied to provide carbon-negative energy by capturing CO 2 emission from the direct combustion of biomass to generate heat or electricity [103,104], as well as from fermentation [105] or gasification [106] of biomass to produce biofuels. Otherwise, with biogas production by anaerobic digestion gaining popularity, biogas upgrading will also play an important role in the bioenergy sector, which consists of removing or converting the CO 2 from the produced biogas to render methane content comparable to natural gas [94,[107][108][109][110][111]. ...
Bioenergy with carbon capture and storage (BECCS) is gaining increasing attention not only as a carbon-neutral alternative to fossil fuels as an energy source, but also as one of the most cost-effective paths to achieve “negative emissions”, which aims at inducing a net emission reduction of atmospheric CO2 with the combined effect of photosynthesis and capture of CO2 emissions. However, like any solution to tackle environmental issues, BECCS has challenges and obstacles to overcome. Concerns over food security, land use, water use, and the feasibility of application at scale have notably been raised and addressing them will be crucial for successful implementation. As an emerging field, active research and development over the next decades, along with strong policy support, is crucial to ensure that BECCS can be implemented in time because delaying action on climate change reduces the likelihood of successfully meeting the goals of the Paris Agreement. Consequently, this critical review aims at establishing the upcoming challenges facing the implementation of BECCS and the pathways to address them, along with highlighting the advancements in the field over the last decade. An overview of the different paths to policy support along with techno-economic analyses of various forms of BECCS is also provided.
... CSTRs are used for hydrolyzing solids and fats in effluents with high solid and fat concentrations and for promoting acidification [73]. They are not prefer treating effluents with too high (e.g. up to 80 g COD/L) or too low (e.g. 2 to 10 g COD/L) of COD concentrations [73,74]. Studies have explored incorporating media into CSTRs to promote methane production and reduce biomass washout [74]. ...
... They are not prefer treating effluents with too high (e.g. up to 80 g COD/L) or too low (e.g. 2 to 10 g COD/L) of COD concentrations [73,74]. Studies have explored incorporating media into CSTRs to promote methane production and reduce biomass washout [74]. CSTRs are frequently used for anaerobic wastewater treatment prior to the 1970's [67]. ...
Three-quarters of the global energy consumption is expected to come from fossil fuels by 2040 despite many drawbacks to the world’s reliance on fossil fuels. The primary drawback of fossil fuels is in procuring, transporting, refining, and combusting them which generates pollution biproducts, global warming, which in turn generate a plethora of associated problems. Biomass as a renewable resource and its conversion into renewable fuel products can offset use and drawback of fossil fuels. Anaerobic digestion is known since the 10thcentury BC has become today a versatile tool to produce renewable energy in form of biogas from many biomass-based feedstock sources. These sources can be agriculturally based such as livestock waste, energy crops, plant (lignocellulosic) based, forest residues, or industrial and municipal waste such food waste, wastewater treatment sludge, distiller grains and food product residues. Feed stocks can be used in anaerobic fermentation processes as single or co-digest feedstock. Each feedstock represents a challenge on its own for anaerobic digestion processes in order achieve good operational stability and good biogas production. Selecting a suitable anaerobic fermentation process from today’s available technical sound processes described in this review is essential for future fossil fuel independence.
... Biogas composition is primarily dependent on conditions during anaerobic digestion (hydrolysis, acidogenesis, acetogenesis, and methane fermentation) as well as the type of organics being biodegraded. Biogas generally consists of methane (CH 4 ; 55-70 %), carbon dioxide (CO 2 ; 30-45 %), H 2 S (0.1-5 %), and trace constituents (e.g., water vapor, halogenated hydrocarbons, siloxanes, ammonia, and nitrogen) (Jürgensen et al., 2017;Barzegaravval et al., 2018). The presence of H 2 S in biogas is a consequence of biodegradation of proteins and other sulfurous compounds in digester feedstocks (Jürgensen et al., 2017). ...
... Biogas generally consists of methane (CH 4 ; 55-70 %), carbon dioxide (CO 2 ; 30-45 %), H 2 S (0.1-5 %), and trace constituents (e.g., water vapor, halogenated hydrocarbons, siloxanes, ammonia, and nitrogen) (Jürgensen et al., 2017;Barzegaravval et al., 2018). The presence of H 2 S in biogas is a consequence of biodegradation of proteins and other sulfurous compounds in digester feedstocks (Jürgensen et al., 2017). The concentration of H 2 S in biogas is directly related to process conditions and the amount of sulfur present in the feedstock (Miltner et al., 2017). ...
Expansion of modern industry coupled with a lack of effective treatment systems has resulted in excessive release of toxic and odorous pollutants such as hydrogen sulfide (H2S). Development of treatment measures is therefore necessary to protect ecosystems and human health. This paper explores recent advances in H2S treatment technologies. Particular focus is placed on innovative and recent advances in biofiltration, especially for wastewater treatment facilities and biogas generation (e.g., use of innovative packing media for better performance and reduced pressure drop, eliminating sulfate accumulation, and development of modeling techniques). The review also identifies current challenges and future prospects (e.g., fluctuations in methane and carbon dioxide concentrations during biogas upgradation, optimizing anoxic H2S biofiltration, and understanding the effects of operating conditions on biofilter performance) for improving biofiltration by highlighting research gaps in related fields.
... Biogas composition is primarily dependent on conditions during anaerobic digestion (hydrolysis, acidogenesis, acetogenesis, and methane fermentation) as well as the type of organics being biodegraded. Biogas generally consists of methane (CH 4 ; 55-70 %), carbon dioxide (CO 2 ; 30-45 %), H 2 S (0.1-5 %), and trace constituents (e.g., water vapor, halogenated hydrocarbons, siloxanes, ammonia, and nitrogen) (Jürgensen et al., 2017;Barzegaravval et al., 2018). The presence of H 2 S in biogas is a consequence of biodegradation of proteins and other sulfurous compounds in digester feedstocks (Jürgensen et al., 2017). ...
... Biogas generally consists of methane (CH 4 ; 55-70 %), carbon dioxide (CO 2 ; 30-45 %), H 2 S (0.1-5 %), and trace constituents (e.g., water vapor, halogenated hydrocarbons, siloxanes, ammonia, and nitrogen) (Jürgensen et al., 2017;Barzegaravval et al., 2018). The presence of H 2 S in biogas is a consequence of biodegradation of proteins and other sulfurous compounds in digester feedstocks (Jürgensen et al., 2017). The concentration of H 2 S in biogas is directly related to process conditions and the amount of sulfur present in the feedstock (Miltner et al., 2017). ...
Expansion of modern industry coupled with a lack of effective treatment systems has resulted in excessive release of toxic and odorous pollutants such as hydrogen sulfide (H2S). Development of treatment measures is therefore necessary to protect ecosystems and human health. This paper explores recent advances in H2S treatment technologies. Particular focus is placed on innovative and recent advances in biofiltration, especially for wastewater treatment facilities and biogas generation (e.g., use of innovative packing media for better performance and reduced pressure drop, eliminating sulfate accumulation, and development of modeling techniques). The review also identifies current challenges and future prospects (e.g., fluctuations in methane and carbon dioxide concentrations during biogas upgradation, optimizing anoxic H2S biofiltration, and understanding the effects of operating conditions on biofilter performance) for improving biofiltration by highlighting research gaps in related fields.
... In the presented study, a specific reactor construction made it possible to achieve the same methane yield at OLRs ranging from 4 kg COD/m 3 ·d to 6 kg COD/m 3 ·d. In turn, Jürgensen and co-workers [47] obtained a slightly higher methane yield of 0.264 L/g COD and 91% of COD removal, but in lower OLRs from 1.3 kg COD/m 3 ·d to 4.3 kg COD/m 3 ·d in a hybrid reactor combining a continuous stirred tank reactor (CSTR) with an anaerobic baffled reactor (ABR) treating dairy effluent. Dareioti and Kornaros [48] obtained a higher methane yield and COD removal efficiency up to 0.9 L/kg COD removed and 84.4% in a two-stage system of CSTRs with a separate methanogenic stage at an OLR of 3.58-7.15 ...
Increasing worldwide milk manufacturing and dairy processing resulted in producing more effluents, and thus effective management of wastewater is now the most important issue. This study used a new design of a pilot plant-scale hybrid anaerobic labyrinth-flow bioreactor (AL-FB) to increase the efficiency of anaerobic biodegradation and biogas productivity and improve anaerobic microflora performance. In addition, effluent recirculation was used to boost the treatment of dairy wastewater. Metagenomic analyses of the anaerobic microbial community were performed. It was found that an organic loading rate (OLR) of 4.0–8.0 g COD/L·d contributed to the highest CH4 yield of 0.18 ± 0.01–0.23 ± 0.02 L CH4/g COD removed, which corresponded to a high COD removal of 87.5 ± 2.8–94.1 ± 1.3%. The evenest distribution of the microorganisms’ phyla determined the highest biogas production. In all tested samples, Bacteroidetes and Firmicutes abundance was the highest, and Archaea accounted for about 4%. Metagenomic studies showed that methane was mainly produced in acetoclastic methanogenesis; however, higher OLRs were more favorable for enhanced hydrogenotrophic methanogenesis. Effluent recirculation enhanced the overall treatment. Thus, at OLR of 10.0 g COD/L·d, the highest COD removal was 89.2 ± 0.4%, and methane production yield achieved 0.20 ± 0.01 L CH4/g COD removed, which was higher by 25% compared to the achievements without recirculation.
... Santos et al. (2021a, b) obtained a 90% COD removal efficiency at an OLR of 1.0 kg COD/m 3 in a hybrid anaerobic biofilm baffled reactor. Jurgensen et al. (2018) studied dairy wastewater using a continuous tank reactor and anaerobic baffled reactor in series, and the researchers obtained 82% COD removal at OLRs between 1.25 and 4.5 kg COD/m 3 . ...
The dairy industry is a very productive sector worldwide and known for producing great volumes of wastewater that is rich in organic matter and nutrients. Apart from fat, the organic matter in such effluents is easily degradable, demanding an external carbon source for conventional denitrification. In this manner, new configurations of reactors promoting a suitable environment for more sustainable nitrogen removal are beyond required—they are paramount. Therefore, the performance of a structured-bed hybrid baffled reactor (SBHBR) with anaerobic and oxic/anoxic chambers was designed and assessed for treating different dairy wastewaters. A combination of baffled and biofilm-structured systems under intermittent aeration was the solution proposed to obtain a new method for nitrogen removal under low COD/TN ratios. The COD/TN ratios tested were 2.1 ± 0.6, 0.84 ± 0.5, and 0.35 ± 0.1 in the inlet of the O/A chambers for operational stages I, II, and III, respectively. The SBHBR provided COD removal efficiencies above 90% in all experimental stages. During stage III, the process had nitrification and denitrification efficiencies of 85.9 ± 17% and 85.2 ± 9%, respectively, resulting in a TN removal efficiency of 74.6 ± 14.7%. Stoichiometric calculations were used to corroborate the activity of bacteria that could perform the anammox pathways as their main mechanisms.
... However, high lipids and suspended solids must be removed before these systems can be implemented. Also this pretreatment can result in methane production reduction and increasing the complexity of the processes (Ji et al., 2020;Jürgensen et al., 2018;Martín-Rilo et al., 2015;McAteer et al., 2020). A novel anaerobic membrane bioreactor (AnMBR) has recently attracted widespread attention as it effectively processes various influents, generates high-quality effluent, has a small footprint, and high treatment efficiency (Hu et al., 2022a;Tang et al., 2022;Wu et al., 2022c). ...
Methanogenic treatment can effectively manage wastewater in the dairy industry. However, its treatment efficiency and stability are problematic due to the feature of wastewater. This review comprehensively summarizes the dairy wastewater characteristics and reveals the mechanisms and impacts of three critical issues in anaerobic treatment, including ammonia and long-chain fatty acid (LCFA) inhibition and trace metal (TM) deficiency. It evaluates current remedial strategies and the implementation of anaerobic membrane bioreactor (AnMBR) technology. It assesses the use of nitrogen-removed effluent return to dilute the influent for solving protein-rich dairy wastewater treatment. It explores the methodology of TM addition to dairy wastewater in accordance with microbial TM content and proliferation. It analyzes the multiple benefits of applying high-solid AnMBR to lipid-rich influent to mitigate LCFA inhibition. Finally, it proposes a promising low-carbon treatment system with enhanced bioenergy recovery, nitrogen removal, and simultaneous phosphorus recovery that could promote carbon neutrality for dairy industry wastewater treatment.
... It allows the identification of the most important environmental aspects and assessment of their impact on the environment throughout the life cycle of a given product (i.e., "from cradle to grave"), starting from obtaining raw materials through the production process, use and final waste management [33]. It can be concluded that an agricultural biogas plant is an installation that perfectly complies with the principles of sustainable development also in terms of the logistics process [34]. ...
The article addresses the progressive changes in the climate caused by increasing concentration of greenhouse gases in the atmosphere. In light of the applicable regulations, Poland should reduce the emissions with significant potential of creating the greenhouse effect. One way to achieve this is to increase the use of renewable energy sources, where biogas energy production is one of the most effective methods. Using the Life Cycle Assessment (LCA) method, the greenhouse gas emissions, expressed as CO2 equivalent generated during the entire logistic process of its production, were calculated.
... In comparison with biogas production potential, actual biogas yield is significantly low, which means a huge potential for biogas production in the future. Therefore, accelerating biogas digesters construction, promoting the capacities of wastes collection and sorting (i.e., dry-wet material separation) and improving biogas fermentation technology can overall enhance actual biogas yield in the future (Li et al., 2016;Gonzalez-Gonzalez et al., 2018;Jurgensen et al., 2017). Fig. 6b shows that there is a great difference in contributing biogas production among different animals. ...
With the ever-growing of livestock and poultry breeding (LPB) in China, its environmental problems have become a common concern. Pollution risk, resource potential and related policies evolution are essential to clarify, which is beneficial to better promote sustainable development of the LPB. In this study, a data-set covering the main animals of China's LPB (covering most of staple animals) and through a long period of 1996–2019 is collected. And then, the pollutants load from China's LPB is evaluated based on the new discharge coefficients adopted from recent research. The results show that China's LPB overall exhibits approximately 10-year periodic change in scale. And, the average annual wastes from China's LPB is up to 2.39 billion tons (Bt) and shows a continuing increase trend coupled with two significant declines (2006 and 2017). The mean wastes load of the LPB is 13,037 kg/ha. And, higher wastes load was found in southwestern and coastally eastern China and more attention should be paid to coastally eastern China due to dramatic increase of the LPB. Approximately 160,287 million m³ (M m³) of biogas production potential is estimated and greatest contributor of which is cattle. China's LPB has been experiencing a sharp and profound transition, converting from a traditional breeding pattern to an intensive one causing some serious environmental risks, especially in rural areas. Currently, China's government has built up scientific and sound framework, methods, regulations and laws for the LPB environmental impact assessment and management, covering pollutants disposal, productive process and environmentally monitoring system of the LPB. Considering the coexisted goals of food security, economic development and human's welfare, large-scale, organic and planting-breeding balanced LPB should be largely encouraged. This study has provided a fully-covered and exact evaluation on characteristic, role, function and environmental effects of China's LPB, furthermore raised novel and target-oriented optimizing strategies and key fields, which help to promote sustainable development of China's LPB and lowering environmental risks caused by it in the future.
... Various researchers have studied biogas production using dairy waste (manure), highlighting not only the environmental benefits of this process but also the importance of the outputs, namely digesters as a means to supply energy services and organic fertilizers [23,24,27]. Other studies focus more on the process of biogas production itself [28,29], in some cases looking for improvements of the bio-digestion process considering mixtures of dairy manure with other bio-wastes such as crop residues and food waste [30][31][32][33][34]. Determining the potential of biogas production, and its economic and environmental implications when utilizing biogas for the supply of electricity and/or heat, are also topics of study [8,17,32,[34][35][36][37][38]. Several investigations have shown that biogas production with dairy/organic waste contributes positively to the reduction of GHG emissions [27,31,33,37,39], which in turn contributes to the sustainability of the livestock sector, since it promotes resource efficiency generating environmental and economic benefits. ...
The transition towards sustainable economies with improved resource efficiency is today's challenge for all productive sectors. The dairy sector in Latin America is growing without considering a clear path for sustainable energy and waste management solutions. This study proposes integrated solutions through a waste-to-energy approach. The solutions consider biogas production (via cow manure) as the main energy conversion pathway; technology solutions include biodigesters, power generators, and combined heat and power systems that supply not only the energy services demanded by dairy farms (for cooking gas, electricity, refrigeration and hot water) but also provide organic fertilizers. Biogas' potential was estimated to verify whether it can cover the energy demands of the farms, while the levelized costs of producing biogas and electricity were the indicators for the techno-economic evaluation of the solutions. Greenhouse gas emission reductions were estimated by following IPCC guidelines. Specifically, the proposed solutions lead to energy self-sufficiency in most dairy farms with relevant biogas and electricity costs in the range of 1.7-3.7 and 6-12 USD cents/kWh, respectively. In addition, implementing the proposed solutions in Latin American dairy farms would allow annual greenhouse gas emission reductions of 32.8 Mton CO 2 eq. with an additional 17 Mton if widespread use of the supplied organic fertilizers is achieved.
... CSTRs require higher HRTs and operate with a solids content of less than 10% [68]. Typical organic loading rates (OLRs) of CSTR plants range from 2 to 8 kg VS m − 3 d − 1 , with higher ranges sometimes resulting in inhibited biogas production [36,[69][70][71]. Relatively high OLRs (4 kg VS m − 3 d − 1 ) and HRTs in excess of 20 days have been reported for the co-digestion of grass silage and dairy slurry with high biomethane production efficiencies [36]. ...
A methodology was developed to determine the location and biomethane potential of on-farm biomass feedstocks and furthermore, the quantity of this biomass situated away from an existing gas grid network. The development of decentralised systems which can be integrated with large industry in such locations offers a potential alternative deployment opportunity to centralised gas grid injection. The total biomethane resource from all on-farm feedstocks in a chosen case country (Ireland) was estimated at 67 PJ. Thematic maps were developed to show the quantity of each on-farm feedstock in different regions of Ireland and their distance from the existing gas network. Approximately 17% of the on-farm biomethane resource in Ireland, though in excess of 15 km from the grid, was within a 15 km radius of a large energy user. Two large energy users were presented as case studies, of which their entire heating demand could be met by the on-farm biomethane resource within a 2.5 km radius of each site. Coupling decentralised biomass with large industry users can potentially offer an alternative energy management strategy.
... It contributes to the improvement of air (reduction of greenhouse gas emissions) and soil (production of organic compost) qualities. It can also be more easily integrated into different energy and sectoral combinations [10][11][12][13]. Thus, anaerobic digestion process for organic fraction of municipal waste can be economically competitive with composting and landfilling operation as it produces simultaneously bioenergy and biofertilizer. ...
Performances of organic household waste anaerobic digestion was investigated in a new horizontal thermophilic pilot digester of 50 L total capacity. The operation was performed under favorable conditions without any chemical additives. The presence of predigested cattle manure in the digester provided an interesting buffer capacity that was able to balance the produced fatty acids during the digestion process.
The biomethane production reached 0.44 m³ CH4/Kg VS while achieving a COD removal of 70%.The operating time and the anaerobic digestion steps were shortened under thermophilic wet digestion. Only 4 days were sufficient to reach the daily maximum methane production (0.084 m³ CH4/(kgVS.day)) and 10 days to reach 80% of the overall biomethane potential. The process efficiency in removing volatile solid was found to be more than 35% within 5 days.
Therefore, wet anaerobic digestion under thermophilic temperature is suitable for industrial scale anaerobic digestion of biowaste regarding the high biomethane yield, the large COD and solid removing and the shortness of process operating time.
... Indeed, this technology is a good option for scientific research as a part of mixed systems, but it is difficult to realize the application of such a bioreactor in the industry as a result of the HRT restriction (Usack et al., 2017). For instance, CSTR and anaerobic baffled reactor (ABR) in series were able to treat low strength dairy wastewater and removed average of 82% COD with a biogas yield of 0.26 m 3 /kg, when fed at constant HRT of 1.6 days in the ABR with OLR between 1.25 and 4.50 kg COD/(m 3 · d) (Jürgensen et al., 2018). Two-stage CSTR-UFAF bi-reactors is a suitable system for anaerobic fermentation to efficiently degrade the liquid fraction of organic municipal waste, with an overall 80% of COD degradation efficiency at high OLR (13.1 kg COD/(m 3 · d)) (Held et al., 2002). ...
The dairy industry is one of the primary water consumers. It produces a large quantity of wastewater with a high concentration of solids, nutrients, fat, and organic compounds characterized by biochemical oxygen demand (BOD) and chemical oxygen demand (COD). Therefore, the treatment of dairy wastewater attracts increasingly more attention. The purpose of the paper is to provide an overview of biological treatment processes for dairy wastewater treatment, including one-stage and two-stage biological processes. The advantages, disadvantages, and limitations of aerobic and anaerobic technologies have been summarized and discussed in detail. Two-stage biological systems are also analyzed. In conclusion, the combined anaerobic and aerobic systems are determined as the most promising technologies for dairy effluent treatment in terms of the quality of the treated water.
... Therefore, the recovery of agro-industrial byproducts and zootechnical wastewater is undoubtedly a more sustainable and rational solution [27,28]. Many AD power plants are fed by different kinds of biowastes, such as wastewater [29][30][31], agricultural residues and food wastes [24,[32][33][34][35][36][37][38][39][40]. On the other hand, development of AD power plants entails a large amount of digestate production as a byproduct. ...
Italian power generation through anaerobic digestion (AD) has grown significantly between 2009 and 2016, becoming an important renewable energy resource for the country, also thanks to the generous incentives for produced electricity available in the last years. This work focuses on the economic and environmental issues of AD technology and proposes a techno-economic analysis of investment profitability without government support. In particular, the analysis focuses on an AD power plant fed by zootechnical wastewater and agro-industrial residues coupled to a cogeneration (CHP) system and a digestate-composting plant that produces soil fertilizers. We aim to determine the economic profitability of such AD power plants fed by inner-farm biomass wastes, exploiting digestate as fertilizer, using the cogenerated heat and taking into account the externalities (environmental benefits). Environmental analysis was carried out via a life cycle analysis (LCA), and encompassing the production of biogas, heat/electricity and compost in the downstream process. The un-released environmental emissions were converted into economic benefits by means of a stepwise approach. The results indicate that integrating a compost plant with a biogas plant can significantly increase the carbon credits of the process. The results were evaluated by means of a sensitivity analysis, and they report an IRR in the range of 6%–9% according to the Italian legislative support mechanisms, and possibilities to increase revenues with the use of digestate as fertilizer. The results significantly improve when externalities are included.
... Therefore, if the study could extend into economic and social dimensions in the future, a thorough understanding on the sustainability of the system could be achieved. According to Coyle and Rebow [42] and Jürgensen et al. [43], sustainability in energy systems is usually associated with energy efficiency and energy with lower emissions. An evaluation tool like the LCA can be used to assess the environmental performance and determine the hotspots along the supply chains, thus providing a comprehensive assessment of the sustainability of the renewable energy system. ...
A life cycle assessment (LCA)-based environmental sustainability evaluation conceptual framework of biogas production has been proposed to improve the sustainability of biogas supply chains. The conceptual framework developed in this study can be used as a guideline for the related stakeholders and decision makers to improve the quality and enhance the sustainability of biogas production in Malaysia as well as promoting biogas as a clean, reliable and secure energy. A case study on an LCA analysis of a zero waste discharge treatment process has been conducted. In the zero discharge treatment system, biogas can be produced with a maximum water recycle and reuse. It was indicated that the biogas production and zero discharge treatment of a palm oil mill e✏uent were environmentally sustainable as the system utilized organic waste to produce bioenergy and achieved zero discharge. However, there were other aspects that should be taken into consideration, particularly regarding the sources of electricity and upstream activity, to ensure the sustainability of the system holistically.
... Different cost-effective and efficient techniques have been developed and used for lactose and protein recovery from dairy effluents in recent past (Das et al., 2016). Dairy wastewater can be used for the production of biogas rich in carbon dioxide content, which can eventually be used for methane production (Jurgensen et al., 2018). Organic acids such as those that acetic and butyric acids are produced from fermentation of cellulose waste, for example, straw and bagasse (Naik et al., 2010). ...
Sustainable rural development requires benign, viable resources of energy. It is vital to the economic, social, and environmental sustainability of nations as well as for poverty eradication. The biorefinery mode operates for converting agroindustrial residues into various products, including biofuels and chemicals through a cascade of modern technologies such as pyrolysis, gasification, Fischer–Tropsch, and other catalytic processes. The development of the agroindustrial waste-based biorefineries can help to stabilize the economy of the rural areas by offering a clean energy service through the replacement of fossil fuel and creating energy security. A great extent of rigorous effort is currently being made for upgrading the existing biorefinery frameworks to fully attain the sustainability standards required to warrant their full-scale implementation. As a consequence of the mandatory inclusion of the sustainability goals into the biorefinery concept and the escalating concern on the “food-fuel conflict,” the biorefineries based on abundant agroindustry wastes are gathering quick popularity. Indian agroindustry wastes display an extraordinary variety of lignocellulosic biomass and round-the-year availability in ample amounts. Unfortunately, due to lack of awareness and poor valorization, these valuable wastes are often destroyed in mass scale for waste management instead of being utilized in a productive way. These residues can be used as an alternate source for the production of different products, such as biogas, biofuel, and as the raw material in various researches and industries. The use of agroindustrial wastes as raw materials can help to reduce the production cost and also reduce the pollution load from the environment. Agroindustrial wastes are used for manufacturing of biofuels, enzymes, vitamins, antioxidants, animal feed, antibiotics, and other chemicals through various processes. The major focus of the present chapter is to present the agroindustry scenario in the world with special reference to India, the adaptability of these wastes to products through cascading of various approaches in a biorefinery mode. The major issues of rural India such as energy security, water purification, and restoration of natural resources such as soil can be partially resolved by using a biorefinery approach. Hence, the implementation of biorefinery unit will help in complete utilization of bio-based resources to produce some value-added end products in an efficient way for sustainable development of rural India.
... This reactor type has several advantages including simplicity (without requirement of mechanical mixing), low energy consumption and ability in separating acidogens and methanogens longitudinally inside the reactor (Zhu et al., 2015). The most important characteristics of ABR are long solid retention time and performance stability under fluctuation of OLRs due to configuration of chamber (Jürgensen et al., 2018). High efficiencies have been reported using ABR in treating several lignocellulosic waste, e.g. ...
The use of agricultural waste to produce biofuel is challenging for waste management. This study investigated the biogas including methane production, and chemical oxygen demand (COD) removal efficiency by anaerobic digestion (AD) from mixed pineapple pulp and peel (MPP). Two-stage of anaerobic digestion system was configured as a continuously stirred tank reactor (CSTR) installed with an anaerobic hybrid reactor (AHR). Total solids (TS) of MPP loading at 4% (w/v) was used with four different hydraulic retention times (HRT) to investigate the subsequent effects, such as pH, alkalinity, biogas and methane production, and COD removal efficiency. The overall pH in CSTR was more acidic than the AHR system and exhibited less stability of the AD process by highly volatile acids. The highest biogas production (0.39 v/v-d) was obtained at HRT 7 with the biogas yield of 0.43 m3/kg COD removed and COD removal efficiency of 67.05% in the AHR system. The separated acidogenic and methanogenic stages in the two-stage system improved the digestion performance. The methane yields in the AHR system remained stable except for the lowest HRT condition (HRT5). Biogas production from pineapple wastes by two-stage anaerobic digestion systems was elucidated and could be applied for a larger digestion scale.Graphical abstract
The management of dairy processing wastewater (DPW) must address water pollution while delivering renewable energy and recovering resources. A high-rate anaerobic membrane bioreactor (AnMBR) was investigated for treating DPW, and the system was evaluated in terms of elemental flow, nutrient recovery, energy balance, and reduction of CO2 emission. The AnMBR system was superior in terms of both methanogenic performance and efficiency of bioenergy recovery in the DPW treatment, with a high net energy potential of 60.5-66.1 kWh/m3. The theoretical economic values of the digestate (13.8 $/m3) and permeate (4.1 $/m3) were assessed according to nutrient transformation and price of mineral fertilizer. The total CO2 emission equivalent in the AnMBR was 39.2 kg CO2-eq/m3, with a significant reduction of 59.6 kg CO2-eq/m3 compared to the conventional process. The application of the AnMBR in the DPW treatment is a promising approach for the development of carbon neutrality and a circular economy.
This paper presents a multi-criteria model to identify the best technology for separating fat from dairy waste and evaluates the economic feasibility of its implementation. Also, the model incorporates the analysis of the project specificities. The methodology was structured in four steps: (i) identification of criteria and technologies by systematic literature review; (ii) acquisition of qualitative information (linguistic variables) from Brazilian and international experts; (iii) application of the TOPSIS 2-tuple multi-criteria linguistic method to rank the technologies; and (iv) evaluation of the economic viability of the best technology identified using the EMIM (expanded multi-index methodology). Separation by centrifugal force, solvent, heating/decanting, acid hydrolysis, and combined methods were the separation technologies most used in the literature and, therefore the considered alternatives. The model was validated in a dairy industry that produces 3,000 m ³ /day of waste, with 3% fat. The performance of the technologies concerning five criteria was between medium poor and good for both groups of experts. Also, the experts indicate centrifugal force as the preferred technology. This technology is economically viable, as it presented a high degree of return and low levels of risks and sensitivities. It is estimated a potential profit of R$ 55 million (NPV) over the project’s entire life cycle, equivalent to an annual return of approximately R$ 14 million (ANPV). This represents an Additional Return on Investment—ROIA of 51.17% annually. The Payback discounted occurs in the first year of its implementation. Similar analyses may apply the model we propose for other contexts involving technologies selection.
The global problem of climate change and difficulties related to energy access, air pollution, and water pollution in India (and other developing countries) necessitate the need to look for alternative clean, local, and low-carbon energy sources for displacing fossil fuels. This paper analyses the existing waste-to-biomethane potential of the sericulture, fisheries, and agro-industrial sectors in India, which have mostly been neglected previously in India’s waste-to-energy assessments. In the process, the volume of wastewaters generated from India’s agro-industries are also estimated, data on which are scarce in the academic and grey literature. India’s annual biomethane potentials (for 2018–19) were found to be 88 million m 3 , 207 million m 3 , and 3514 million m 3 from the three sectors, respectively. To assess the energy generation potential of these wastes, a comprehensive literature review was conducted and data on residue-to-product ratios, results of proximate analyses, and specific biomethane yields were either compiled or calculated. The gross thermal energy and electricity generation potentials are 132 PJ and 22 TWh respectively; between 19 and 95 million people can benefit from such waste-to-energy production, depending on the end use of the biomethane for electricity generation or as a domestic cooking fuel. The corresponding mean removal of organic pollution from India’s surface waters can be between 5.5 and 9.3 million tonnes of chemical oxygen demand. For the end uses of biomethane in electricity generation and cooking, the cumulative GHG abatements attributable to these industries are 11.4 million tonnes and 6.8 million tonnes of carbon dioxide-equivalent respectively. Besides the numeric results reported, this paper also contains a comprehensive compilation of data on waste characteristics and biomethane productions. The present status of biogas generation and related policy implementation in India are reviewed and discussed. Overall, our findings indicate that biomethane from these wastes and wastewaters can generate substantial energy for India, is in line with recent government policies, and can aid India in achieving six Sustainable Development Goals of the United Nations.
Brazil is a significant producer of agricultural and agro-industrial waste, which can be used to recover valuable resources, such as struvite, hydroxyapatite, methane gas, hydrogen gas, and carboxylic acids, to mitigate the environmental impacts of the agro-industrial sector, add economic value to organic waste, and promote the sustainability of natural resources. Thus, this work's objective was to compile and analyze data on the composition, physical-chemical characterization, and volumetric production of six agricultural and agro-industrial wastewaters (AWWs) from activities of paramount importance in Brazilian agribusiness and to report studies on resource recovery from those liquid wastes. The literature review was carried out by analyzing scientific works obtained by searching for keywords in different databases. It was concluded that swine wastewaters (SWs), slaughterhouse wastewaters (SHWs), and dairy wastewaters (DWs) are the most promising for struvite recovery. DWs also stand out for the recovery of hydroxyapatite. SWs and brewery wastewaters (BWs) are commonly used for prospecting for algae or bacterial biomass and their derivative products. All AWWs analyzed are considered promising for biogas, methane and hydrogen, while the most soluble AWWs are more valuable for carboxylic acid production.
Anaerobic wastewater treatment is still a dynamically developing technology ensuring the effective degradation of organic compounds and biogas production. As evidenced in the large scale-up, this technological solution surpasses aerobic methods in many aspects. Its advantages stem from the feasibility of operation at a high organic load rate, the smaller production of difficult-to-manage sewage sludge, the smaller space and cubature required, and the high-methane biogas ultimately produced. The exploitation of anaerobic reactors is in line with the assumption of a circular economy, material recycling by reduced CO2 emissions and energy consumption, and the production of renewable energy. Despite their unquestionable advantages, there is still a need to seek novel approaches and improve the currently exploited installations. The key avenues of research entail improvements in the stability of bioreactor operations and the enhancement of bioreactor adaptability to changing and unfavorable process parameters. The versatility of such systems would also be greatly improved by increasing nitrogen and phosphorus removal rates. Attempts have been made to achieve these goals by setting up separate zones within bioreactors for the individual steps of methane fermentation, incorporating active fillings to promote nutrient removal, and introducing chemical and physical treatments. An interesting solution is also the use of microwave radiation to stimulate temperature conditions and induce non-thermal phenomena, such as enhancing the enzymatic activity of methanogenic microflora. Another prospective approach is to integrate digesters into microalgal biomass production systems. The aim of this review paper is to present the thus-far technological knowledge about anaerobic wastewater treatment, including standard solutions and innovative ones, the effectiveness of which has been corroborated in pilot-scale installations.
This work designed and assessed the performance of a structured-bed hybrid baffled reactor (SBHBR) with anaerobic/anoxic chambers, treating different dairy wastewater. The anoxic chambers in SBHBR were exposed to intermittent aeration for the simultaneous removal of organic matter and total nitrogen (TN) under a low COD/TN ratio. The hydraulic retention time (HRT) in SBHBR was 48h, with 16.3h in the anoxic zone, where intermittent aeration was implemented, consisting of 60 minutes of aeration and 30 minutes without aeration. The COD/TN ratios tasted were 2.1 ± 0.6, 0.84 ± 0.5, and 0.35 ± 0.1 in the inlet of the anoxic chambers. The SBHBR provided COD removal efficiencies above 90% in all experimental stages. The relevant results achieved in this research regarding carbon and nitrogen removal efficiencies were obtained in stage III. The SBHBR achieved a TN removal efficiency of 82.3 ± 11.4% during this stage. The nitrification and denitrification efficiencies were 85.9 ± 17% and 85.2 ± 9%, respectively, resulting in the anoxic zone TN removal efficiency of 74.6 ± 14.7% with a C/N ratio of 0.35 ± 0.1. Stoichiometric calculations based on nitrogen removal and the C/N ratio required by the denitrification process were used to corroborate the activity of bacteria that perform the anammox pathways as their main mechanism.
This study conducted a techno-economic analysis to compare two types of thermophilic anaerobic reactors and three biogas utilization schemes in biogas production from vinasse. The reactors studied were the Fixed Bed Reactor (FBR) and Continuous Stirred Tank Reactor (CSTR). The biogas utilization schemes investigated were biogas conversion to electricity compared to direct biogas use for co-firing in the existing boiler and combined uses for co-firing and domestic fuel sale to the nearby households around the plant. The techno-economic calculations were based on experimental data using the prototypes of FBR and CSTR. The fixed and working capital estimations were based on Indonesia's construction industry database. At the same Organic Loading Rate (OLR) of 9.66 g sCOD per litre, 7-day Hydraulic Retention Time (HRT), and 200 m³/day vinasse capacity, FBR produced twice more biogas than CSTR. The economic analysis result indicated that the scheme of co-firing in existing boilers by fuel-oil replacement and partial substitution of coal was economically more attractive than the electricity production at the current electricity pricing in Indonesia. In this recommended scheme, we obtained 17.26% internal rate of return, 4.34 years payback period, and Rp20.94 billion net present value.
Food waste have become a growing concern worldwide with raising population and economic growth. Wastewater discharged from food industries contains many valuable and toxic components that have a negative impact on the ecological system. Large amounts of wastewater are discharged from the food industry, which necessitates the creation of effective technologies. Wastewater from the food industry can be seen as a rich source of energy and a primary source for generating valuable products. Waste disposal and resource recovery are sustainably valued by anaerobic digestion of wastewater from the food sector. The characteristics, composition, and nature of wastewater produced from various food sectors are elaborated upon in this review. An overview of the anaerobic digestion process for wastewater treatment in the food industry is included. Enhancement strategies for the anaerobic digestion process have been discussed in detail. In addition, various types of reactors utilized for performing anaerobic digestion is illustrated. Though anaerobic digestion process possesses advantages, the challenges and future scope are examined for improving the outcome.
Endophytes are the microorganisms that inhabit plants without any detriment to the latter. These microbial communities are believed to be a long associated with plants and have evolved with them. Living inside the plants, these endophytes help the plants in dealing with various kinds of environmental or biological stresses, increasing the productivity and sustainability of the plant. Endophytes achieve this by producing certain bioactive compounds (secondary metabolites or enzymes), altering the physiology of the plant, acting as biocontrol agents for both pathogenic microbes and pests, etc. This chapter reviews a variety of fungal endophytes residing in crop plants and aiding crop improvement through various mechanisms.
Energy obtained from renewable resources has become crucial to reduce the impact of Greenhouse Gases. New and renewable energy resources offer a gripping possibility as they are inexhaustible and affordable. In particular, the biogas from these sources is a useful reserve for biofuels in terms of both potentiality and heat generation. Several microorganisms such as Methanobacterium sp., Methanosarcina sp., Methanococcus sp., Methanosaeta sp., and Methanospirillum were isolated from different ecological systems and are identified for their use in the production of biogas. With rapid development in biological sciences and understanding of metagenomics, designing and construction of microbial consortia has gained notable attention and has become one of the major areas in modern renewable energy science. This chapter is focused on the use of natural and synthetic microbial consortia for digestion and degradation of waste effluents (residues from agriculture/horticulture/sericulture/forestry/fisheries, industrial, and municipal waste) to obtain biomethane and find a solution to trouble that comes up during its production in order to enhance and improve the effectiveness of the process.
A fermenter (bioreactor) is a closed vessel with sufficient aeration, agitation, temperature, and pH regulation arrangements and a drain or overflow vent to extract the waste biomass along with its products from cultured microorganisms. The fermenter is intended for the production of biological products. The fermenter’s design and mode of operation depend primarily on the production organism, the optimal working condition needed to create the target product, the product value, and the production scale. Fermenter is a consent to design criteria including sterilization ability; simple construction; easy calculation, monitoring, control techniques; scale-up; flexibility; long-term stability; upstream process compatibility, antifoaming steps. Fermentation is accomplished in several forms, including batch, fed-batch, and continuous fermentation process. The current chapter addresses the fermenter configuration, fermentation mechanism, fermenter types used in industries, heat and mass transfer in the fermenter, and the scaling up and regulation of the industrial fermentation process.
Dairy industry wastewater is rich in organic content, presenting a high biodegradability, and therefore biological treatments are widely employed. This study aimed to evaluate biosolids production in three systems: activated sludge (AS), movingbed biofilm reactor (MBBR), and sequencingbatch movingbed biofilm reactor (SBMBBR). Simulated dairy wastewater was used at different organic load rates (OLRs): 1.22, 2.87, and 5.44 gCOD L−1d−1. Besides biosolids production, COD, total carbon (TC), and total nitrogen (TN) removal efficiency was evaluated. Biosolids production was measured in the mixed liquor, carrier-adhered biomass, treated wastewater, and surplus sludge. The operational conditions were kept similar for the three systems, with a carrier filling ratio of 50% for MBBR and SBMBBR. The SBMBBR proved to have better performance in the removal efficiencies of COD, TC, and TN for all OLRs studied. The MBBR presented a similar COD and TC removal efficiency as the SBBR for the two highest OLRs (2.87 and 5.44 gCOD L−1d−1). Concerning biosolids production, the MBBR system produced less biomass and delivered the lowest amount of adhered biomass inside the carriers. The AS treatment generated the highest amount of sludge and offered the worst treatment capability for all OLRs evaluated.
Dairy industries are one of the major food industries which generate a huge amount of wastewater both in terms of volume and strength. The chemical composition of dairy wastewater ranges from 1000 to 4500 mg/l for COD, 500 to 3000 mg/l for BOD, and 160 to 800 mg/l for TSS. Such wastewaters, if discharged into the environment without proper treatment will pose serious detrimental effects on water, land and air. The major portion of the wastewater generated from dairies is highly organic which depicts its higher degree of biodegradability. Compared to the aerobic and physicochemical methods employed for treating dairy wastewaters, anaerobic treatment methods are highly promising, cost-effective, and provide a sustainable energy generation option. The present manuscript critically evaluates the effect of various factors like pH, temperature, organic loading rate, hydraulic retention time, availability of nutrients, and C/N ratio on the process of anaerobic digestion. Recent studies and older research are considered for this study which concludes that these factors have a pertinent influence on the performance of an anaerobic digester. To check the feasibility of adopting an anaerobic digestion technology in both small and large-scale dairy units, technical and economic analysis is a must. This chapter also provides a detailed techno-economic analysis (TEA) framework for biogas production from dairy wastes.
Increasing demand for dairy products resulted in the development of a large number of dairy industries, generating wastewater of high pollution potential. Main wastes generated include whey residues, milk fat and proteins, dairy sludge, and liquid effluents produced through different lines (cleaning, processing, and sanitary). Anaerobic digestion technology has got wide acceptance in recent times for treating highly organic effluents like dairy wastes due to its added benefits like energy recovery and high waste stabilisation with less energy requirement. This review paper is aimed at studying the effects of different key parameters (pH, carbon-to-nitrogen ratio, temperature, organic loading rate, solid retention time, hydraulic retention time, alkalinity, and mixing) on the successful operation of an anaerobic digester and thereby enhancing biogas production efficiency. Different waste streams generated in the dairy industry are identified along with their important characteristics. The process chemistry of anaerobic degradation of various effluents generated from the dairy industry is discussed. The need for pre-treatment technologies and the scope of co-digestion of dairy wastewater with other organic wastes are also covered. This critical review is intended to summarise the present knowledge on the application of anaerobic methods for treating dairy wastes most efficiently with proper control over operational parameters while maximising the biogas yield.
Graphical abstract
The anaerobic digestion is a process widely recognized as an interesting alternative for the treatment and stabilization of residual organic substrates. However, several technical limitations were observed based on the characteristics of the organic matter submitted to the process, such as the presence of high concentrations of soluble sugars or fats. The technology of anaerobic digestion in multiple stages is described as a viable option in the control of variables, optimizing the environmental conditions of the main microorganisms involved in the process, assuring high solid removal and methane production, besides allowing a higher energy yield through the generation of molecular fuel hydrogen. Several studies reviewed the process of anaerobic digestion in multiple stages in the treatment of food waste, although few report its use applied directly to agroindustrial residues. Thus, the present work aims to review the literature evaluating the scenario and viability of the multi-stage anaerobic digestion process applied to agroindustrial effluents. Effluents such as manipueira, vinasse, and dairy wastewater are substrates that present high yields when treated by AD processes with stage separation. The high concentration of easily fermentable sugars results in a high production of molecular hydrogen (co-product of the production of volatile acids in the acid phase) and methane (methanogenic phase). The great challenges related to the development of the sector are focused on the stability of the composition and yield of hydrogen in the acid phase, besides the problems resulting from the treatment of complex residues. Thus, the present study suggests that future works should focus on the technologies of new microorganisms and optimization of process parameters, providing maturation and scale-up of the two-stage anaerobic digestion technique.
The main objectives of this research were twofold: a) to evaluate the performance of a low-temperature pilot-scale upflow anaerobic sludge blanket (UASB) reactor during the treatment of a chocolate-processing industry wastewater (CIW) with high soluble chemical oxygen demand; and b) to evaluate the performance of two thermal conditioning devices (TCDs) for bioenergy recovery through the in-situ biogas use. For 275 days, the UASB reactor was operated at low temperature (17–19 °C), short hydraulic retention time (6.2 h) and variable total organic loading rate (OLRT) and soluble organic loading rate (OLRS) (10.3 ± 2.9 kg-CODΤ/m³/d and 7.9 ± 2.2 kg-CODS/m³/d, respectively). The produced biogas was burned in-situ with two TCDs, which mainly consisted of an insulated combustion chamber, a heat exchanger and a Bunsen burner. The OLRT and OLRS removal efficiencies were 59.5 ± 13.6% and 71.4 ± 13.2%, respectively, whereas the biogas production was in the range of 119–834 L/d. In-situ burning of the produced biogas with the TCDs increased the influent temperature between 0.8 and 5.8 °C, which improved the biogas production of the UASB reactor. The CIW energetic potential was calculated based on the UASB reactor operational parameters, the calorific value of methane in biogas and the daily CIW production (90 m³) of the studied factory. The estimated CIW energetic potential (13.59 MJ/m³CIW) represents a sustainable source of energy, which could be enough to satisfy the power consumption of 25–42 households in Toluca Valley Metropolitan Area, Mexico.
There is a synergy between the large quantities of organics-rich effluents generated by the dairy industry and the continually increasing water needs for crop irrigation. In this sense, this study aimed at evaluating the effect of decreasing the hydraulic retention time (HRT) on the stability and efficiency of a hybrid anaerobic biofilm baffled reactor (HABBR) treating simulated fat- and salt-rich dairy wastewater, followed by its agricultural reuse. The reactor was monitored over 328 days, during which 72, 24, and 12 h were the hydraulic detention times. After achieving steady-state, the reactor presented organic matter removal greater than 90% and produced biogas with 41 ± 23%, 53 ± 3%, and 64 ± 12% of methane for HRTs of 72, 24, and 12 h, respectively. The best process performance was observed for an HRT of 24 h, and thus, a lettuce culture was irrigated with the treated effluent. The irrigation was performed in five different treatments, for which the amount of treated effluent added to tap water varied from 0 to 100%. Both the effluent and the harvested vegetables were evaluated for microbial contamination. Apart from the 75% effluent supply condition, there were no losses in leaf mass or area observed; instead, there was an increase of these parameters for the 25% and 50% effluent supply treatment. The use of dairy effluent treated by the HABBR allowed for microbiologically safe food production. Therefore, the process offered both potential cost reduction for fertilizers, preservation of water resources, and a renewable energy source. HIGHLIGHTS
The anaerobic baffled reactor was stable during treatment of fat-rich salt dairy wastewater.;
The methane content was enhanced with hydraulic retention time reduction.;
The use of dairy effluent reduced the needs related to N fertilizer by up to 50%.;
The use of drinking water for lettuce irrigation has been reduced by 50%.;
The effluent did not present a risk of contamination in lettuce production.;
Whey, a by-product of the dairy industry obtained during cheese production, is a rich source of different nutrients. As it is produced in enormous quantities, if untreated, it poses a big threat to the environment. Despite different attempts, the disposal of whey has become a big problem for industries. Therefore in order to overcome this problem and to meet the different governmental and environmental agencies, there is need for the search of technologies for the sustainable management of whey. Being rich in nutrients, whey can act as a substrate for the growth of microorganisms and subsequent production of different value-added products. Thus with the advent of biotechnological innovations, the valorization of whey for the production of value-added products has become feasible. These techniques can not only help to reduce the production cost, but also provide an alternative for the disposal of whey. This chapter provides comprehensive information about whey, its characteristics, different microbial sources, and various strategies applied for the biotransformation of whey into value-added products.
This paper aimed to explore the anaerobic resource conversion from some agro-industrial wastewaters (AWWs) employing three biorefinery platforms (methane, hydrogen, and carboxylic acids). Additionally, it presents the reported quantitative and qualitative characterization of AWWs, bioproduct conversion yields, by which it was possible to estimate the gross value added of the by-products. The studied AWWs showed to have excellent economic potentials for resource recovery, in which the CA platform seems to be more economically advantageous, especially when a chain elongation process is considered. However, the traditional anaerobic digestion is simpler in terms of process control, and methane purification is usually easier and cheaper. Because of the low yields achieved, it seems that hydrogen production is the least attractive technological route. Therefore, it is necessary to analyze other factors such as the gross value-added, consolidation of the production and recovery techniques, among others, to adopt the best choice of resource recovery platform.
Biological bubble-column (BBC) is beneficial for elemental sulfur recycle from H2S, but it's difficult to remove high concentration of H2S in biogas efficiently due to the mass transfer limitation of H2S from gas to liquid. In this study, a novel method with refluxing outlet gas in BBC was investigated. The results showed that gas reflux greatly enhanced the removal of high concentration of H2S (about 5000 ppmv) from biogas. The removal efficiency of H2S was 88.0 ± 4.1% with the reflux ratio at 1.0, which was higher than those without gas reflux (58.4 ± 1.0%), when the inlet H2S loading was 143.1 ± 4.5 g/(m3·h). Moreover, the removal capacity of H2S improved significantly with the increase of the reflux ratios from 1.0 to 4.0 and achieved the maximum at 271.8 ± 2.4 g/(m3·h). This might mainly be attributed to longer residence time and enhanced the mass transfer of O2 and H2S from gas to liquid through gas reflux.
Environmental comparison between conventional and hybrid anaerobic baffled reactors (CABR and HABR) was investigated. In the first study, the two reactors were operated, in parallel, from the same source of dairy wastewater at an organic loading rate of 3.33±0.03g-COD/L.d. The HABR was packed with sponge media characterized by specific surface area: 157 m 2 /m 3 , density: 65 kg/m 3 and voids ratio: 0.65. Results showed that, CABR and HABR achieved COD removal efficiencies of 72.50±2.40 and 87.86±2.12 % with biogas yield of 111.10±8.87 and 155.80±7.02 mL-CH 4 /g-COD r , respectively. The better methanogenic activity of HABR was attributed to the lower sludge yield (Y obs) of 0.067 g-VSS/g-COD (compared to Y obs of CABR: 0.084 g-VSS/g-COD). In the second investigation, experimental results were used to predict the greenhouse gas emissions (GHG) and economic performance of a large-scale ABR with a capacity of 200 m 3 /d. The CABR revealed lower GHG of 8.06±0.52 kg-CO 2 /m 3 than that of HABR: 13.72±0.61 kg-CO 2 /m 3 . Additionally, the CABR and HABR found net profits of 0.44±0.02 and 0.78±0.04 €/m 3 , and would return their investment in payback periods of 4.88±0.21 and 3.00±0.12 y, respectively.
The aim of this work was to study the possible deactivation effects of biogas trace ammonia concentrations on methanation catalysts. It was found that small amounts of ammonia led to a slight decrease in the catalyst activity. A decrease in the catalyst deactivation by carbon formation was also observed, with ammonia absorbed on the active catalyst sites. This was via a suppression of the carbon formation and deposition on the catalyst, since it requires a higher number of active sites than for the methanation of carbon oxides. From the paper findings, no special pretreatment for ammonia removal from the biogas fed to a methanation process is required.
The production of biogas through anaerobic digestion is one of the technological solutions to convert biomass into a readily usable fuel. Biogas can replace natural gas, if the biogas is upgraded to green gas. To contribute to the EU-target to reduce Green House Gases emissions, the installed biogas production capacity and the amount of farm-based biomass, as a feedstock, has to be increased. A model was developed to describe a green gas production chain that consists of several digesters connected by a biogas grid to an upgrading and injection facility. The model calculates costs and energy use for 1 m3 of green gas. The number of digesters in the chain can be varied to find results for different configurations. Results are presented for a chain with decentralized production of biogas, i.e. a configuration with several digesters, and a centralized green gas production chain using a single digester. The model showed that no energy advantage per produced m3 green gas can be created using a biogas grid and decentralized digesters instead of one large-scale digester. Production costs using a centralized digester are lower, in the range of 5 €ct to 13 €ct per m3, than in a configuration of decentralized digesters. The model calculations also showed the financial benefit for an operator of a small-scale digester wishing to produce green gas in the cooperation with nearby other producers. E.g. subsidies and legislation based on environmental arguments could encourage the use of decentralized digesters in a biogas grid.
The methanation of CO2 has been increasingly discussed for the potential long term storage of electricity and for facilitating grid load management. Using the regions of northern Germany as a case study, the feasibility of CO2 conversion from biogas plants and its integration in existing natural gas grid was examined in this study. Furthermore the material and energy flows of in the methanation process, were evaluated to provide expression for the quantities of excess electrical energy which could be potentially stored using the biogas integrated systems. The study results showed that with 480 biogas plants in the region would be able to utilize up to 0.7 TWh surplus electricity could be used to produce 100 106 m3 at standard temperature and pressure of upgraded methane per year.
Anaerobic treatment is often reported to be an effective method for treating dairy effluents. The objective of this paper is to summarize recent research efforts and case studies in anaerobic treatment of dairy wastewaters. The main characteristics of industrial dairy waste streams are identified and the anaerobic degradation mechanisms of the primary constituents in dairy wastewaters, namely carbohydrates (mainly lactose), proteins and lipids are described. Primary attention is then focused on bench–pilot–full-scale anaerobic treatment efforts for dairy waste effluents. Combined (anaerobic–aerobic) treatment methods are also discussed. Finally, areas where further research and attention are required are identified.
This project has studied the appropriateness of the ABR for on-site primary sanitation in low-income communities. The baffled design of the ABR ensures high solids retention resulting in high treatment rates, while the overall sludge production is
characteristically low. Effluent COD values measured from a 3 000 l pilot ABR using domestic wastewater at a wastewater treatment works were consistently below 200 mgCOD/l at an HRT of 22 h, and a 1 log reduction of pathogen indicator organisms (E. coli and total coliforms) was observed. Analysis of results indicates that the operating flow rate was too high to allow complete fermentation of particulate COD; it is expected that better COD and pathogen removal will be obtained at smaller hydraulic/organic loads. This paper presents results obtained for a 5 month analytical period at a single operating point. Operational and institutional issues relating to the appropriateness of the technology for on-site sanitation are explored, as well as the acceptability of the technology to target communities. Health related aspects associated with reuse of the effluent for agricultural purposes are discussed. Water SA Vol. 30 (5) 2005: pp.44-50
Dairy wastewater was evaluated for biological hydrogen (H2) production in conjugation with wastewater treatment in a suspended growth sequencing batch reactor (AnSBR) employing sequentially pretreated [heat-shock (100 °C, 2 h) and acid (pH 3.0, 24 h)] mixed consortia. The bioreactor was operated at mesophilic (room) temperature (28 ± 2 °C) under acidophilic conditions (pH 6.0) with a total cycle period of 24 h consisting of FILL (15 min), REACT (23 h), SETTLE (30 min), and DECANT (15 min) phases at three different organic loading rates (OLR) of 2.4, 3.5, and 4.7 Kg COD/m3-day, respectively. H2 evolution rate differed significantly with the substrate/OLR of wastewater used as substrate [OLR 2.4 Kg COD/m3-day - volumetric H2 production rate: 0.3683 mmol H2/m3-min; specific H2 production rate: 0.0184 mmol H2/min-g CODL; OLR 3.5 Kg COD/m3-day - volumetric H2 production rate: 1.105 mmol H2/m3-min; specific H2 production rate: 0.0245 mmol H2/min-g CODL and OLR 4.7 Kg COD/m3-day - volumetric H2 production rate: 0.7367 mmol H2/m3-min; specific H2 production rate: 0.0107 mmol H2/min-g CODL]. Substrate (COD) removal efficiency of 64.7 (substrate degradation rate (SDR): 1.577 Kg COD/m3-day), 60 (SDR: 3.168 Kg COD/m3-day), and 50% (SDR-3.2 Kg COD/m3-day), respectively, was observed at operating OLR of 2.4, 3.5, and 4.7 Kg COD/m3-day, respectively. The system showed rapid stabilization tendency (2.4 Kg COD/m3-day: 39 days; 3.5 Kg COD/m3-day: 14 days; 4.7 Kg COD/m3-day: 24 days) with respect to H2 generation and COD reduction. A surge in pH values from 5.8 to 4.5 (2.4 Kg COD/m3-day), 5.82 to 4.62 (3.5 Kg COD/m3-day), and 6.28 to 4.56 (4.7 Kg COD/m3-day) was observed during stabilized phase of operation.
The anaerobic treatment process is increasingly recognized as the core method of an advanced technology for environmental protection and resource preservation and it represents, combined with other proper methods, a sustainable and appropriate wastewater treatment system for developing countries. Anaerobic treatment of sewage is increasingly attracting the attention of sanitary engineers and decision makers. It is being used successfully in tropical countries, and there are some encouraging results from subtropical and temperate regions. In this review paper, the main characteristics of anaerobic sewage treatment are summarized, with special emphasis on the upflow anaerobic sludge blanket (UASB) reactor. The application of the UASB process to the direct treatment of sewage is reviewed, with examples from Europe, Asia and the Americas. The UASB reactor appears today as a robust technology and is by far the most widely used high-rate anaerobic process for sewage treatment.
Treatment of low-strength soluble wastewater (COD approximately 500 mg/L) was studied using an eight chambered anaerobic baffled reactor (ABR). At pseudo steady-state (PSS), the average total and soluble COD values (COD(T) and COD(S)) at 8h hydraulic retention time (HRT) were found to be around 50 and 40 mg/L, respectively, while at 10h HRT average COD(T) and COD(S) values were of the order of 47 and 37 mg/L, respectively. COD and BOD (3 day, 27 degrees C) removal averaged more than 90%. Effluent conformed to Indian standards laid down for BOD (less than 30 mg/L). Reactor effluent characteristics exhibited very low values of standard deviation indicating excellent reactor stability at PSS in terms of effluent characteristics. Based on mass balance calculations, more than 60% of raw wastewater COD was estimated to be recovered as CH(4) in the gas phase. Compartment-wise profiles indicated that most of the BOD and COD got reduced in the initial compartments only. Sudden drop in pH (7.8-6.7) and formation of volatile fatty acids (VFA) (53-85 mg/L) were observed in the first compartment due to acidogenesis and acetogenesis. The pH increased and VFA concentration decreased longitudinally down the reactor. Residence time distribution (RTD) studies revealed that the flow pattern in the ABR was neither completely plug-flow nor perfectly mixed. Observations from scanning electron micrographs (SEM) suggest that distinct phase separation takes place in an ABR.
The volume of biogas produced in agricultural areas is expected to increase in coming years. An increasing number of local and regional initiatives show a growing interest in decentralized energy production, wherein biogas can play a role. Biogas transport from production sites to user, i.e. a CHP, boiler or an upgrading installation, induces a scale advantage and an efficiency increase. Therefore the exploration of the costs and energy use of biogas transport using a dedicated infrastructure is needed. A model was developed to describe a regional biogas grid that is used to collect biogas from several digesters and deliver it to a central point. The model minimizes transport costs per volumetric unit of biogas in a region. Results are presented for different digester scales, different sizes of the biomass source area and two types of grid lay-out: a star lay-out and a fishbone lay-out. The model shows that transport costs in a fishbone lay-out are less than 10 €ct m−3 for a digester scale of 100 m3 h−1; for the star lay-out costs can go up to 45 €ct m−3. For 1800 m3 h−1 digesters, these values are 4.0 €ct m−3 and 6.1 €ct m−3, respectively. The results indicate that cooperation between biogas producers in collecting biogas by means of a fishbone lay-out reduces the biogas transport costs relative to using a star lay-out. Merging smaller digesters into a smaller number of larger ones reduces the costs of biogas transport for the same biomass source area.
In the future energy infrastructure there is a considerable potential for biogas and, in particular, for biomethane as a natural gas substitute. Among the alternatives of upgrading biogas to biomethane, this work focuses on membrane permeation. Taking cellulose acetate as membrane material and spiral-wound as membrane configuration, five layouts are assessed. All layouts have the same biogas plant rated at 500 m3/h (STP), yet they may adopt: (i) one- or two-stage permeation, (ii) permeate or residue recycle, and (iii) a water heater or a prime mover (internal combustion engine or a micro gas turbine) to exploit residues as fuel gas. Since residues are consumed, all layouts have zero emission of methane into the atmosphere. The membrane material is modeled considering the phenomenon of plasticization; the membrane modules are described by a crossflow permeation patterns without pressure drops. The results indicates that specific membrane areas range from 1.1 to 2.4 m2h/m3 (STP), specific energy from 0.33 to 0.47 kWh/m3 (STP), and exergy efficiencies from 57.6% to 88.9%. The splitting of permeation over two stages and the adoption of water heater instead of prime movers is a convenient option. The preferred layout employs a single compressor, a two-stage membrane permeation at 26 bar, a water heater fueled by the first-stage permeate, and a second-stage permeate recycle. Assuming a biomethane incentive of 80 €/MWhLHV and a project life of 15 years, the total investment of this plant is 2.9 M€, the payback time 5 years and the net present value 3.5 M€.
This study evaluated hydrogen production and chemical oxygen demand removal (COD removal) from tapioca wastewater using anaerobic mixed cultures in anaerobic baffled reactor (ABR). The ABR was conducted based on the optimum condition obtained from the batch experiment, i.e. 2.25 g/L of FeSO4 and initial pH of 9.0. The effects of the varying hydraulic retention times (HRT: 24, 18, 12, 6 and 3 h) on hydrogen production and COD removal in a continuous ABR were operated at room temperature (32.3 ± 1.5 °C). Hydrogen production rate (HPR) increased with a reduction in HRT i.e. from 164.45 ± 4.14 mL H2/L.d (24 h HRT) to 883.19 ± 7.89 mL H2/L.d (6 h HRT) then decreased to 748.54 ± 13.84 mL H2/L.d (3 h HRT). COD removal increased with reduction in HRT i.e. from 14.02 ± 0.58% (24 h HRT) to 29.30 ± 0.84% (6 h HRT) then decreased to 21.97 ± 0.94% (3 h HRT). HRT of 6 h was the optimum condition for ABR operation as indicated.
The effect of Ni content on the Ni/Ce-ZrO2 catalyst has been investigated in the methane conversion reactions to syngas, such as oxy-reforming, steam reforming and oxy-steam reforming. Among the catalysts examined, Ni/Ce-ZrO2 catalyst with 15% Ni loading exhibits not only the highest catalytic activity and selectivity but also remarkable stability. The TPR results reveal that strong interaction between support and metal exists and that some part of NiO incorporates into the surface of the Ce-ZrO2 support. Combined with H2 chemisorption results, one may deduce that Ni surface area and the chemical environment of nickel, as well as the properties of the Ce-ZrO2 support, play very important roles in the catalytic activity and stability of Ni/Ce-ZrO2 catalysts. It seems that two kinds of active sites, i.e. one for methane and the other for steam or oxygen, are well-balanced on 15% Ni/Ce-ZrO2 catalyst.
Optimal locations of renewable energy sources are often remote relative to consumers and electricity grids. In contrast, some existing CNG pipelines pass through optimal renewable energy harvesting regions. The growing interest in the possibility of using geothermal energy in central Australia has created a need to assess the economic, technical, and environmental viability of converting remote renewable energy to fuel for transport using existing CNG pipelines, and to compare this alternative with that required to construct new high-capacity electricity transmission lines. This assessment is reported, using first the conversion of electricity to hydrogen, and then conversion of the hydrogen to methane. The paper also compares the alternative of direct injection of hydrogen into existing CNG pipelines to create “hythane” (HCNG). An economic assessment showed that the relative capital and operating costs are sufficient make the alternative carrier prospect worthy of further consideration.
Siloxanes are widely used in industrial processes and consumer products. Some of them reach the wastewater. Siloxanes are not decomposed in the activated sludge process and partly concentrate in the sludge. During anaerobic digestion of the sludge, they volatilise into the formed biogas. Combustion of silicon containing gases, e.g., when producing electricity, produces, however, the abrasive microcrystalline silica that has chemical and physical properties similar to those of glass and causes serious damage to gas engines, heat exchangers and catalytic exhaust gas treatment systems.The growing consumption of silicones and siloxanes and the subsequent increased concentration in wastewater, together with the increasing interest in the production of biogas and “green energy” in sewage treatment plants, has created significant concern about the presence of siloxanes and the related damage (fouling etc.) in the biogas beneficiation equipment.The present paper, therefore, reviews the fundamentals of siloxanes and the current problems of the associated fouling. Moreover, it summarizes the useable methods for siloxane abatement from biogas and makes some recommendations towards preventive actions.
The reuse of wastewater from the dairy industry was investigated using coagulation, adsorption and membrane separation. Dairy industry was chosen as it requires huge volume of water. In recent times, development of newer membranes with high flux/rejection characteristics have increased the probability of water reuse and recycling up to a greater extent. In this investigation thorough pretreatment studies were done using different types of coagulants categorized as inorganic, polymeric, and organic having biological origins. The coagulant treatment was performed at various pH using different dosages and it was followed by activated charcoal treatment. The combined effects of these two pretreatment methodologies were evaluated. The color and the odor were removed completely and permanently after charcoal treatment. The pretreated water was passed through a cross flow reverse osmosis membrane system and the permeate water was found to have very good quality. This was compared to the process water used by the dairy farm and was found that the water can be recycled or reused.
A review concerning the development, applicability and possible future application of the anaerobic baffled reactor for wastewater treatment is presented. The reactor design has been developed since the early 1980s and has several advantages over well established systems such as the upflow anaerobic sludge blanket and the anaerobic filter. These include: better resilience to hydraulic and organic shock loadings, longer biomass retention times, lower sludge yields, and the ability to partially separate between the various phases of anaerobic catabolism. The latter causes a shift in bacterial populations allowing increased protection against toxic materials and higher resistance to changes in environmental parameters such as pH and temperature. The physical structure of the anaerobic baffled reactor enables important modifications to be made such as the insertion of an aerobic polishing stage, resulting in a reactor which is capable of treating difficult wastewaters which currently require several units, ultimately significantly reducing capital costs.
An anaerobic baffled reactor with four compartments (C1-C4) was successfully used for treatment of acetone-butanol-ethanol fermentation wastewater and methane production. The chemical oxygen demand (COD) removal efficiency was 88.2% with a CH(4) yield of 0.25L/(g COD(removed)) when organic loading rate (OLR) was 5.4kg CODm(-3)d(-1). C1 played the most important role in solvents (acetone, butanol and ethanol) and COD removal. Community structure of C2 was similar to that in C1 at stage 3 with higher OLR, but was similar to those in C3 and C4 at stages 1-2 with lower OLR. This community variation in C2 was consistent with its increased role in COD and solvent removal at stage 3. During community succession from C1 to C4 at stage 3, abundance of Firmicutes (especially OTUs ABRB07 and ABRB10) and Methanoculleus decreased, while Bacteroidetes and Methanocorpusculum became dominant. Thus, ABRB07 coupled with Methanoculleus and/or acetogen (ABRB10) may be key species for solvents degradation.
The applicability of anaerobic baffled reactor (ABR) was investigated for the treatment of acidic (pH 4.5-7.0) wastewater containing sulfate (1000-2000 mg/L) and Zn (65-200mg/L) at 35 degrees C. The ABR consisted of four equal stages and lactate was supplemented (COD/SO(4)(2-)=0.67) as carbon and energy source for sulfate reducing bacteria (SRB). The robustness of the system was studied by decreasing pH and increasing Zn, COD, and sulfate loadings. Sulfate-reduction efficiency quickly increased during the start-up period and reached 80% within 45 days. Decreasing feed pH, increasing feed sulfate and Zn concentrations did not adversely affect system performance as sulfate reduction and COD removal efficiencies were within 62-90% and 80-95%, respectively. Although feed pH was steadily decreased from 7.0 to 4.5, effluent pH was always within 6.8-7.5. Over 99% Zn removal was attained throughout the study due to formation of Zn-sulfide precipitate.
A nine-chambered modified anaerobic baffled reactor (MABR) was developed to evaluate its suitability for the treatment of municipal wastewater and to establish the understanding of the relationship between reactor design and operational parameters. The paper presents the configuration of the MABR, its start-up, effect of variation of hydraulic retention time (HRT) on treatment efficiency, and performance evaluation of the MABR while treating the municipal wastewater. To assess the self-inoculation potential of the MABR, the start-up was carried out without seed sludge at a HRT of 6 d. An acclimatization curve was plotted and indicated that a start-up period of 90 d was required for the MABR. Reactor performance evaluation was carried out for 375 d at 11 different HRTs ranging from 6 d to 3h. The HRT of 6h was adjudged to be appropriate for this reactor configuration. At a HRT of 6h, the efficiencies of reduction in suspended solids (SS), biochemical oxygen demand (BOD), and chemical oxygen demand (COD) were found to be 86%, 87% and 84% respectively. Specific biogas yield and methane content were found to be 0.34m(3)CH(4)/KgCODr and 67% respectively. The study has evaluated the performance pattern of the MABR and identified it as a suitable reactor technology for municipal wastewater management in India.
Nature's photosynthesis uses the sun's energy with chlorophyll in plants as a catalyst to recycle carbon dioxide and water into new plant life. Only given sufficient geological time can new fossil fuels be formed naturally. In contrast, chemical recycling of carbon dioxide from natural and industrial sources as well as varied human activities or even from the air itself to methanol or dimethyl ether (DME) and their varied products can be achieved via its capture and subsequent reductive hydrogenative conversion. The present Perspective reviews this new approach and our research in the field over the last 15 years. Carbon recycling represents a significant aspect of our proposed Methanol Economy. Any available energy source (alternative energies such as solar, wind, geothermal, and atomic energy) can be used for the production of needed hydrogen and chemical conversion of CO(2). Improved new methods for the efficient reductive conversion of CO(2) to methanol and/or DME that we have developed include bireforming with methane and ways of catalytic or electrochemical conversions. Liquid methanol is preferable to highly volatile and potentially explosive hydrogen for energy storage and transportation. Together with the derived DME, they are excellent transportation fuels for internal combustion engines (ICE) and fuel cells as well as convenient starting materials for synthetic hydrocarbons and their varied products. Carbon dioxide thus can be chemically transformed from a detrimental greenhouse gas causing global warming into a valuable, renewable and inexhaustible carbon source of the future allowing environmentally neutral use of carbon fuels and derived hydrocarbon products.
The start-up and operational performance (total 212 days, including the start-up of 164 days) of an anaerobic baffled reactor (ABR), which is used to treat heavy oil produced water, was studied without the temperature control. Inoculums were mixtures of acclimated sediment taken from a heavy oil produced water treatment plant and digested sludge from a sewage wastewater treatment plant. The rod-shaped and spherical granules with colors of henna and black, in which Clostridia, Methanosarcina and Methanothrx sp. were main populations, were observed in each compartment of ABR after the reactor's successful start-up (day 164). Rhodopseudomonas with the activity of lipase and halotolerant, as a kind of photosynthetic bacteria, was also observed in the first five compartments. X-ray diffraction (XRD) showed that the spherical granule sludge was compact and contained a large amount of organics, amorphous materials, and crystals of Fe(2)O(3), FeS, and CaCO(3), whereas the rod-shaped granule sludge was incompact without crystals of Fe(2)O(3), FeS, and CaCO(3). Scanning electron microscope (SEM) showed that the skeleton construction of this rod-shaped granule was filamentous bacteria and amount of extracellular polymeric substances (EPS). The ABR, after successful start up, can achieve high average chemical oxygen demand (COD) and oil removals of 65% and 88% for heavy oil produced water with poor nutrient (COD:TN:TP, 1200:15:1) and high salt concentration (1.15-1.46%), respectively. Furthermore, ABR kept stable during 2.5 times the COD level shock load (0.50 kg COD m-3 d-1) for four days.
Treatment of a low strength complex wastewater of chemical oxygen demand (COD) around 500mg/L was studied in a 10L capacity laboratory scale anaerobic baffled reactor (ABR). It was operated at hydraulic retention times (HRTs) of 20, 15, 10, 8 and 6h. Corresponding organic loading rates (OLRs) were 0.6, 0.8, 1.2, 1.5 and 2kg COD/m3d. At every HRT (or OLR), pseudo steady state (PSS) was achieved. Even at maximum OLR of 2kg COD/m3d, COD and biochemical oxygen demand (BOD) removals exceeded 88%. Removal of particulate fraction of organics was found to be greater than soluble fraction. Compartment-wise studies of various parameters revealed that if the OLR was larger, the number of initial compartments played significant role in the removal of organics. The values of volatile fatty acids (VFA) demonstrated that hydrolysis and acidogenesis were the main biochemical activities in the initial few compartments. Based on the tracer studies, dead space in the ABR was found to range from 23% to 34%. The flow pattern in the ABR was classified as intermediate between plug flow and perfectly mixed flows. Observations from scanning electron micrographs (SEM) also suggested that distinct phase separation takes place in an ABR. Study of organic and hydraulic shock loads revealed that ABR was capable of sustaining the type of shock loads generally experienced at a sewage treatment plant (STP).
The establishment of a sustainable energy future is one of the most pressing tasks of mankind. With the exhaustion of fossil resources the energy economy will change from a chemical to an electrical base. This transition is one of physics, not one of politics. It must be based on proven technology and existing engineering experience. The transition process will take many years and should start soon. Unfortunately, politics seems to listen to the advice of visionaries and lobby groups. Many of their qualitative arguments are not based on facts and physics. A secure sustainable energy future cannot be based on hype and activism, but has to be built on solid grounds of established science and engineering. In this paper the energy needs of a hydrogen economy are quantified. Only 20%-25% of the source energy needed to synthesized hydrogen from natural compounds can be recovered for end use by efficient fuel cells. Because of the high energy losses within a hydrogen economy the synthetic energy carrier cannot compete with electricity. As the fundamental laws of physics cannot be chanced by research, politics or investments, a hydrogen economy will never make sense
Entwicklng einer speziellen aktivkohle für den einsatz zur biogasentschwefelung und untersuchung der leistungsf€ ahigkeit im labor und im praktischen einsatz
- S Rossow
S. Rossow, Entwicklng einer speziellen aktivkohle für den einsatz zur biogasentschwefelung und untersuchung der leistungsf€ ahigkeit im labor und im
praktischen einsatz, (Dissertation).
Die karte der erneuerbaren energien, Database provided by the German Association of Solar Energy
- T Engel
T. Engel, Die karte der erneuerbaren energien, Database provided by the
German Association of Solar Energy, energymap.info, 2015.