Search

India is one among the Asia's newly industrialized countries, in which urban centres generate large amount of municipal solid wastes due to the rapid urbanization. To demonstrate urban waste potentials for biogas production by anaerobic digestion, a comprehensive analysis on the availability of organic waste hotspots and its biogas potential for the exemplary case of Chennai, India, was undertaken. The identified hotspots and their biogas potential were plotted with Geographical Information System as thematic maps. The results of biogas potential tests revealed strong variations in the biogas potentials of individual waste streams from 240.2 to 514.2 mL N /g oDM (organic dry matter) with oDM reduction in the range of 36.4-61.5 wt.-%. Major waste generation hotspots were identified from the surveyed urban bio-reserves and the biogas potentials within an effective area of 5 km radius surrounding the hotspot were estimated. It was found that the biogas potential of individual hotspots ranged between 38.0-5938.7 m 3 /day. Further results revealed that the biogas potential during anaerobic co-digestion, by considering nearby bio-reserves in the effective areas of major hotspots, with and without residential organic waste, ranged between 4110.4-18-106.1 m 3 /day and 253.2-5969.5 m 3 /day, originating from 144.0-620.0 tons and 3.1-170.5 tons, respectively. Despite variations in the composition of the wastes, the Carbon/Nitrogen ratio, oDM reduction, biogas production and substrate availability were improved during co-digestion of nearby bio-reserves within the major hotspots, thereby improving the prevailing barriers in substrate management during anaerobic digestion of wastes.

The i-REXFO LIFE project designs an innovative business model with the objective of reducing significantly the amount of landfilled food waste. Given the availability of supermarket food waste in the Umbria region (Italy), the logistics is optimized using a Vehicle Routing Problem Solver, mass and energy balances of the biogas plant are partly calculated and partly measured from a real biogas plant. The data obtained from food waste transport and anaerobic co-digestion process are used as input for LCA analysis. The aim of the methodology is to assess the environmental and economic benefit of the substitution of energy crops (like corn silage) with food waste in anaerobic digestion. Two approaches are adopted: consequential LCA and attributional LCA. Only one impact category is taken into account: climate change. This decision has been taken to focus on two decision making criteria (economic feasibility and GHG emissions reduction). The results show that a reduction of 42% in the carbon footprint of the electricity produced from the biogas plant can be obtained by substituting about 9900 t of corn silage with 6600 t of food waste. Through the combined use of economic analysis and consequential LCA it has been possible to identify an optimized scenario in which: food waste produced from food industries is collected and used to produce energy in Expired Food Energy chains (EFE), while the food obtained from supermarkets is used to promote charity initiatives in actions aiming at the Reduction of Expired Food waste (REF)., Competing Interests: Declaration of competing interest The authors certify that they have NO affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers' bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Solid-state anaerobic digestion (SS-AD) is commonly used to treat feedstocks with high solid content such as municipal solid waste and lignocellulosic biomass. Compared to liquid state anaerobic digestion (LS-AD), SS-AD has multiple advantages including high organic loading, minimal digestate generated, and low energy requirement for heating. However, the main disadvantages limiting the efficiency of SS-AD are long solid retention time, incomplete mixing, and an accumulation of inhibitors. For a successful and efficient SS-AD, it is important to control operation parameters such as nutrient levels, C/N ratio, feedstock-to-inoculum ratio, pH, temperature, and mixing. Biogas production in SS-AD performance can be enhanced by feedstock pretreatment, co-digestion, and supplement of additives such as biochar. The aim of this chapter is to provide a comprehensive summary of the current development in SS-AD as an effective way for treating solid waste materials. Graphical Abstract.

Anaerobic co-digestion of sewage sludge and glycerol from the biodiesel industry was evaluated in three experimental stages. In the first step, the addition of higher proportions of crude glycerol (5-20% v/v) to the sludge was evaluated, and the results showed a marked decrease in pH and inhibition of methane production. In the second step, co-digestion of sludge with either a lower proportion (1% v/v) of crude glycerol or glycerol pretreated to remove salinity resulted in volatile acid accumulation and low methane production. The accumulation of volatile acids due to the rapid degradation of glycerol in the mixture was more detrimental to methanogenesis than the salinity of the crude glycerol. In the third step, much lower amounts of crude glycerol were added to the sludge (0.3, 0.5, 0.7% v/v), resulting in buffering of the reaction medium and higher methane production than in the control (pure sludge). The best condition for co-digestion was with the addition of 0.5% (v/v) crude glycerol to the sewage sludge, which equals 0.6 g glycerol/g volatile solids applied. Under this condition, the specific methane production (mL CH 4 /g volatile solids applied) was 1.7 times higher than in the control.

The feasibility of simultaneous treatment of multiple wastes via co-digestion was studied in semi-continuous mode at mesophilic conditions. The obtained results indicated that sewage sludge, organic fraction of municipal waste (OFMSW) and grease trap sludge (GTS) possess complementary properties that can be combined for successful anaerobic digestion. During the co-digestion period, methane yield and VS removal were significantly higher in comparison to digestion of sewage sludge alone. Addition of GTS to digesters treating sewage sludge resulted in increased VS removal and methane yield up to 13% (from 50 to 56.4) and 52% (from 300 to 456,547m 3 /Mg VS add ), respectively. While the use of OFMSW as the next co-substrate in the feedstock, can boost methane yield and VS removal up to 82% (300-547m 3 /Mg VS add ) and approximately 29% (from 50% to 64.7%), respectively. Moreover, the results of the present laboratory study revealed that the addition of co-substrates to the feedstock had a significant influence on biogas composition. During the experiment methane content in biogas ranged from 67% to 69%. While, the concentration of LCFAs was increasing with the gradual increase in the share of co-substrates in the mixtures, wherein only the oleic acid was higher than some inhibition concentrations which have been reported in the literature. However, it did not significantly affect the efficiency of the co-digestion process., (Copyright © 2017. Published by Elsevier Inc.)

The feasibility of co-digestion of blends of two different animal by-products (pig manure and pasteurized slaughterhouse waste) and recovered glycerine was studied in mesophilic conditions. Experiments were performed in a lab-scale CSTR along 490days, with a hydraulic retention time of 21-33days and with a step-wise increased organic loading rate, by adding and/or changing the wastes ratio, from 0.8 to 3.2kg COD m -3 d -1 . The best methane production rate (0.64Nm 3 CH4 m -3 d -1 ) represented an increment of 2.9-fold the initial one (0.22Nm 3 CH4 m -3 d -1 with pig manure solely). It was attained with a ternary mixture composed, in terms of inlet volatile solids, by 35% pig slurry, 47% pasteurized slaughterhouse waste and 18% glycerine. This blend was obtained through a stepwise C/N adjustment: this strategy led to a more balanced biodegradation due to unstressed bacterial populations through the performance, showed by the VFA-related indicators. Besides this, an improved methane yield (+153%) and an organic matter removal efficiency (+83%), regarding the digestion of solely pig slurry, were attained when the C/N ratio was adjusted to 10.3., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Anaerobic co-digestion of food waste (FW) and pig manure (PM) was undertaken in batch mode at 37°C in order to identify and quantify the synergistic effects of co-digestion on the specific methane yield (SMY) and reaction kinetics. The effects of the high initial volatile fatty acid (VFA) concentrations in PM on synergy observed during co-digestion, and on kinetic modelling were investigated. PM to FW mixing ratios of 1/0, 4/1, 3/2, 2/3, 1/4 and 0/1 (VS basis) were examined. No VFA or ammonia inhibition was observed. The highest SMY of 521±29ml CH4/gVS was achieved at a PM/FW mixing ratio of 1/4. Synergy in terms of both reaction kinetics and SMY occurred at PM/FW mixing ratios of 3/2, 2/3 and 1/4. Initial VFA concentrations did not explain the synergy observed. Throughout the study the conversion of butyric acid was inhibited. Due to the high initial VFA content of PM, conventional first order and Gompertz models were inappropriate for determining reaction kinetics. A dual pooled first order model was found to provide the best fit for the data generated in this study. The optimal mixing ratio in terms of both reaction kinetics and SMY was found at a PM/FW mixing ratio of 1/4., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Solid-state anaerobic co-digestion of tomato residues with dairy manure and corn stover was conducted at 20% total solids under 35°C for 45days. Results showed digestion of mixed tomato residues with dairy manure and corn stover improved methane yields. The highest VS reduction (46.2%) and methane yield (415.4L/kg VSfeed) were achieved with the ternary mixtures of 33% corn stover, 54% dairy manure, and 13% tomato residues, lead to a 0.5-10.2-fold higher than that of individual feedstocks. Inhibition of volatile fatty acids (VFAs) to biogas production occurred when more than 40% tomato residues were added. The results indicated that ternary mixtures diluted the inhibitors that would otherwise cause inhibition in the digestion of tomato residues as a mono-feedstock., (Copyright © 2016. Published by Elsevier Ltd.)

Horse keeping is of great economic, social and environmental benefit for society, but causes environmental impacts throughout the whole chain from feed production to manure treatment. According to national statistics, the number of horses in Sweden is continually increasing and is currently approximately 360,000. This in turn leads to increasing amounts of horse manure that have to be managed and treated. Current practices could cause local and global environmental impacts due to poor performance or lack of proper management. Horse manure with its content of nutrients and organic material can however contribute to fertilisation of arable land and recovery of renewable energy following anaerobic digestion. At present anaerobic digestion of horse manure is not a common treatment. In this paper the potential for producing biogas and biofertiliser from horse manure is analysed based on a thorough literature review in combination with mathematical modelling and simulations. Anaerobic digestion was chosen as it has a high degree of resource conservation, both in terms of energy (biogas) and nutrients (digestate). Important factors regarding manure characteristics and operating factors in the biogas plant are identified. Two crucial factors are the type and amount of bedding material used, which has strong implications for feedstock characteristics, and the type of digestion method applied (dry or wet process). Straw and waste paper are identified as the best materials in an energy point of view. While the specific methane yield decreases with a high amount of bedding, the bedding material still makes a positive contribution to the energy balance. Thermophilic digestion increases the methane generation rate and yield, compared with mesophilic digestion, but the total effect is negligible., (Copyright © 2016. Published by Elsevier Ltd.)

This work aims at selecting a suitable strategy to improve the performance of the anaerobic digestion of residues generated in the treatment of waste vegetable oils (WVO). Biochemical methane potential (BMP) assays were conducted at 35 °C to evaluate the effects of substrate mix ratio between a mixture of WVO residues (M) and pig manure (PM) co-digesting by using different inocula. Inoculum from an industrial digester fed with organic waste from hotels, restaurants and catering leftovers (HORECA) showed higher methanogenic activity (55.5 mLCH4 gVS(-1) d(-1)) than municipal wastewater treatment plant (mWWTP) inoculum (42.6 mL CH4 gVS(-1) d(-1)). Furthermore, the results showed that the resistance to WVO residues toxicity was higher for the HORECA sludge than for the mWWTP sludge. HORECA inoculum produced more biogas in all the assays. Moreover, the resulting biogas was of better quality, containing an average of 71.1% (SD = 1.6) methane compared to an average of 69.5% (SD = 1.2) methane for test with mWWTP sludge. The maximum degradation rate occurred at the higher PM mix ratio (M/PM:1/3), reaching 26.7 ± 4.3 mLCH4 gVS(-1) d(-1) for mWWTP inoculum, versus 42.0 ± 1,5 mLCH4 gVS(-1) d(-1) achieved for HORECA inoculum. A high reduction of volatile solids (between 70% and 81%) was obtained with both inocula at all M/PM ratios assayed (1/0, 1/3, 1/1 and 3/1 v/v) but, bearing in mind the operation of a full-scale anaerobic plant, the optimal scenario assayed corresponds to the ratio M/PM: 1/3 v/v where shorter lag periods will make it possible to operate at lower hydraulic retention times., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Anaerobic digestion of manure and other agricultural waste streams with subsequent energy production can result in more sustainable dairy operations; however, importation of digester feedstocks onto dairy farms alters previously established carbon, nutrient, and salinity mass balances. Salt and nutrient mass balance must be maintained to avoid groundwater contamination and salination. To better understand salt and nutrient contributions of imported methane-producing substrates, a mass balance for a full-scale dairy biomass energy project was developed for solids, carbon, nitrogen, sulfur, phosphorus, chloride, and potassium. Digester feedstocks, consisting of thickened manure flush-water slurry, screened manure solids, sudan grass silage, and feed-waste, were tracked separately in the mass balance. The error in mass balance closure for most elements was less than 5%. Manure contributed 69.2% of influent dry matter while contributing 77.7% of nitrogen, 90.9% of sulfur, and 73.4% of phosphorus. Sudan grass silage contributed high quantities of chloride and potassium, 33.3% and 43.4%, respectively, relative to the dry matter contribution of 22.3%. Five potential off-site co-digestates (egg waste, grape pomace, milk waste, pasta waste, whey wastewater) were evaluated for anaerobic digestion based on salt and nutrient content in addition to bio-methane potential. Egg waste and wine grape pomace appeared the most promising co-digestates due to their high methane potentials relative to bulk volume. Increasing power production from the current rate of 369 kW to the design value of 710 kW would require co-digestion with either 26800 L d(-1) egg waste or 60900 kg d(-1) grape pomace. However, importation of egg waste would more than double nitrogen loading, resulting in an increase of 172% above the baseline while co-digestion with grape pomace would increase potassium by 279%. Careful selection of imported co-digestates and management of digester effluent is required to manage salt and nutrient mass loadings and reduce groundwater impacts., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

The global shift towards sustainable waste management has led to an intensified exploration of co-digestion and co-treatment of sewage and organic waste using anaerobic reactors. This review advocates for an integrated approach where organic waste is treated along with the sewage stream, as a promising solution to collect, treat, and dispose of organic waste, thereby reducing the environmental and economic burden on municipalities. Various efforts, ranging from laboratory to full-scale studies, have been undertaken to assess the feasibility and impacts of co-digestion or co-management of sewage and organic waste, using technologies such as up-flow anaerobic sludge blankets or anaerobic membrane bioreactors. However, there has been no consensus on a standardized definition of co-digestion, nor a comprehensive understanding of its impacts. In this paper, we present a comprehensive review of the state-of-the-art in liquid anaerobic co-digestion systems, which typically operate at 1.1% total solids. The research aims to investigate how the integration of organic waste into mainstream anaerobic-based sewage treatment plants has the potential to enhance the sustainability of both sewage and organic waste management. In addition, utilizing the surplus capacity of existing anaerobic reactors leads to significant increases in methane production ranging from 190 to 388% (v/v). However, it should be noted that certain challenges may arise, such as the necessity for the development of tailored strategies and regulatory frameworks to enhance co-digestion practices and address the inherent challenges. [ABSTRACT FROM AUTHOR]

This review paper delves into the intricate challenge of transforming microalgal biomass into biofuel through anaerobic digestion, elucidating its significance for sustainable energy production and waste management. Despite the promise anaerobic digestion holds, obstacles like inhibitory substances, process stability issues, and residue management complexities persist. Microalgal biomass, characterized by high biogas yields and carbon sequestration potential, emerges as a viable solution to enhance anaerobic digestion efficiency. Employing a comprehensive literature selection process, the review synthesizes recent studies to shed light on breakthroughs and pinpoint areas for future investigation. Key findings underscore advancements in microalgal biomass utilization, with strategic strain selection and innovative pretreatment methods resulting up to 25% increase in biogas production. Additionally, the assimilation of co-digestion techniques yields enhanced overall process efficiency. Microalgal biomass demonstrates remarkable carbon sequestration capabilities, sequestering up to 60% of CO2 during the anaerobic digestion process. Furthermore, the analysis reveals that despite inhibitory substances posing challenges, innovative approaches have reduced inhibition by 15%, promoting more stable and efficient digestion. Implications of the review findings stress the need to scale laboratory successes to industrial applications while maintaining environmental sustainability. Identified gaps include challenges in inhibitory substance management and process stability, with future research directions advocating for multidisciplinary approaches to unlock the full potential of microalgal biomass in anaerobic digestion. In conclusion, the review contributes significantly to understanding the intricate relationship between microalgal biomass and anaerobic digestion, highlighting the importance of continued research and development to address existing challenges and advance towards a more regenerative bioeconomy. [ABSTRACT FROM AUTHOR]

This article discusses a study on the anaerobic co-digestion of vegetable waste with cattle dung and fruit waste in India to generate biogas. The study aims to treat waste, generate biogas, and reduce environmental pollution. The results show that the co-digestion of vegetable waste with equal proportions of cattle dung and fruit waste yields the highest biogas volume. The study concludes that this method can generate significant biogas yield and reduce environmental pollution. [Extracted from the article]

Anaerobic digestion is a process that can provide both clean energy and environmentally sustainable management of organic wastes. However, dry anaerobic digestion is susceptible to inhibitions and still has technological hurdles that limit its implementation. The study of operational parameters for the treatment of OFMSW in many places of the world is conducted, but the effect of the substrate composition is poorly understood. The present study evaluated strategies to enhance methane production from two different types of OFMSW, provided by two municipalities of Sabana Centro (Colombia), that are distinguished from each other by the presence (Cajicá, W1) and absence (Chia, W2) of meat residues. For both residues, higher methane production was achieved when the lowest substrate to inoculum ratio was used. ACoD with MGW enhanced biogas production with both sources of OFMSW, increasing 61% of production when non-meat residues were used, and always being necessary for production on residues with meat. Fungal pretreatment did not increase methane yields as expected from experiences in other studies due to pH drops and the accumulation of potential toxic inhibitors. In conclusion, as organic waste composition is critical to achieve an efficient dry anaerobic digestion performance, results presented in this work highlights the need to consider how much nature of the substrate influences the process. The findings of this study hold significance for the scientific community working on dry anaerobic digestion. The study presents novel insights into the co-digestion of OFMSW and the pretreatment with the WRF. Furthermore, the results have practical implications for local authorities in Sabana Centro. Based on these findings, policymakers can formulate new source-separation policies, and a dry anaerobic digestion facility can be designed to meet the specific characteristics of the substrates. • Fungal pretreatment and co-digestion strategies were evaluated for OFMSW. • The impact of substrate composition on mono and co-digestion was evaluated. • Information about fungal pretreatment of OFMSW with white rot fungi is presented. • The best operational parameters for co-digestion of OFMSW were proposed. • Waste composition is critical to an efficient dry anaerobic digestion performance. [ABSTRACT FROM AUTHOR]

Anaerobic digestion is a well-known and long-used biological method for stabilizing organic materials. Among the benefits of this process in waste management are the reduction of greenhouse gases, the production of alternative energy, and the acquisition of valuable digestate that can be used in the form of biogas, thereby closing the cycle of elements in nature. For some materials, such as manure, which is heterogeneous in terms of morphology and chemical composition, digestion of a single substrate may not be very efficient. Therefore, more and more studies on the co-digestion process are appearing in the literature. This solution allows higher biogas production and the possibility of processing several wastes simultaneously. The prospect of the future effective application of anaerobic co-digestion depends on regulations, work regime, and access to raw materials. Therefore, there is a need to systematize the available knowledge and results, as well as to identify the possibilities and limitations of the discussed process, which is undertaken in this paper. [ABSTRACT FROM AUTHOR]

The convergence of sustainability and climate change has catalyzed the pursuit of inventive strategies for waste management and sustainable energy production. Hereby, we explored the effect of coupling biochar addition and thermal pretreatment in anaerobic mono-digestion and co-digestion of thermally pretreated thickened waste activated sludge (PTWAS) with food waste (FW). Six semi-continuous lab-scale digesters were operated for 161 days at various organic loading rates (OLR of 2, 3, 4 and 8 kgCOD/m3/day) with and without biochar (BC) addition. Coupling biochar addition and co-digestion of 30%FW +70% PTWAS, increased methane yield (MY) by 87.5% to 0.15 LCH 4 /gCOD added, when the systems experienced high ammonia concentration of 2.4 g/L at OLR of 8 kgCOD/m3/d. The non-competitive ammonia inhibition constant (Ki) ranged from 0.250 g/L to 0.345 g/L. The maximum COD-to-BC ratio to overcome inhibition was 16.5 g COD substrate /g BC corresponding to TN-to-BC ratio of 0.84 g TN substrate /g BC. These results imply that biochar addition to the anaerobic co-digestion of thermally pretreated TWAS and FW can promote high-rate anaerobic digestion by relieving ammonia and VFA inhibition. [Display omitted] • Ammonia inhibition constant was determined using non-competitive inhibition model. • Coupling BC with codigestion of FW and TWAS improved methane yield by 87.5%. • BC addition enhanced COD removal efficiency, MY, and biodegradability. • COD-to-BC and TN-to-BC ratios were optimized. [ABSTRACT FROM AUTHOR]

Clean electricity is generated by the anaerobic digestion of biomass waste. The environmental impacts of various biomass waste feedstocks vary, while co-digestion has been reported to improve anaerobic digestion performance. A consequential life-cycle assessment (LCA) and techno-economic analysis (TEA) are carried out for cow manure waste management for a cow farm. Three scenarios are considered in this study: (S1) mono-digestion of cow manure, (S2) co-digestion of cow manure and maize silage, and (S3) co-digestion of cow manure with cow feed waste, sewage sludge, and returned dairy products. The LCA aims to quantify the environmental impact of each MWh of electricity generated, assuming the plant is located in Malaysia, using OpenLCA software. The TEA economic parameters are quantified and compared between the three scenarios. Net present value (NPV), Internal Return Rate (IRR), and Return of Investment (ROI) are examined. Among the three scenarios, S2 with maize cultivation has a higher environmental impact due to its higher energy requirements. With the integration of closed digestate storage and renewable energy-powered electricity, S3 has the best environmental performance in global warming, eutrophication and acidification. S3 is found to be most economically viable, with MYR 1.28 million NPV, 14% IRR, and 15% ROI, and a Payback Period of 6.56 years with an OPEX of MYR 3491.82/MWh. [ABSTRACT FROM AUTHOR]

Experiments in series horizontal anaerobic reactors with fixed bed (HARFB) were conducted to evaluate the co-digestion of crude glycerol (CG) from biodiesel production and domestic sewage (DS) concerning the start-up strategy and best organic loading rate (OLR) to improve biogas production as well as to analyze the dynamic changes in the anaerobic microbial consortium during their operation. This approach can be used to increase the buffering capacity of anaerobic reactors as well as dilute toxic compounds. The reactor configuration applied at the present research is a novelty about CG and DS co-digestion and biogas production. The highest hydrogen generation was 10.3 mol H2 (m3 day−1) in reactor R1, and the highest methane yield was 312.0 and 283.9 L CH4 (m3 day−1) in R2 and R3, respectively. These values, obtained with mixed culture, agree with previous co-digestion research. The three-stage system showed high efficiency in removing crude glycerol and chemical oxygen demand (COD), with consumptions of 99.9%, both. The strategy of co-digestion is positive to avoid substrate inhibition. In addition, there was a change in the relative abundance of microorganisms among R1, R2, and R3 and a considerable decrease in the diversity index in the fermentation reactor (R1). The results have shown the potential of applying HARFB reactors for energy recovery and alternative waste disposal. [ABSTRACT FROM AUTHOR]

In the context of increasing pressure regarding the sustainable utilization of food waste in a circular economy, one of the trends is their biological transformation, through anaerobic digestion, into biogas as a renewable source of energy. We presented the physical-chemical properties of the main categories of food waste from different sources: dairy, meat, and poultry, fish, fruit and vegetable, cereal and bakery, brewing and winery industries, and others. Due to the high organic load, the presence of a multitude of nutrients, and an insignificant amount of inhibitors, food waste can be successfully used in the biogas production process in co-digestion with other materials. Physical (mechanical and thermal), chemical (alkali, acid, and oxidative), and biological (enzymatic, bacterial, and fungal) techniques have been widely used for pretreatment of different substrate types, including food waste. These pretreatments facilitate the degradation of pretreated food waste during anaerobic digestion and thus lead to an enhancement in biogas production. The purpose of this study is to review the situation of food waste generated in the food industry and to formulate the main trends of progress in the use of this waste in the anaerobic digestion process. [ABSTRACT FROM AUTHOR]

Buffalo grass and alkaline-pretreated buffalo grass samples were co-digested with cow manure separately to generate biogas in anaerobic reactors. The study considered a solid content of 20% (10% buffalo grass and 10% cow manure). The methane (CH 4) content and CH 4 yield of the distinct experiments were compared. For the untreated buffalo grass, the weighed buffalo grass was mixed with cow manure and water. For the alkaline-pretreated buffalo grass, the weighed buffalo grass was soaked in 1% sodium hydroxide for 1 day prior to being mixed with cow manure and water. The untreated and pretreated buffalo grass-manure were fed semi-continuously at the rate of 125 mL/day for five days feeding in a 5 L reactor, with 40 days hydraulic retention time. The experiments were conducted for approximately 100 days. Results were reported when the systems were in steady-state conditions. The chemical oxygen demand (COD) conversion efficiency of co-digestion of the untreated and pretreated buffalo grass-manure were 46.21 and 62.76%, respectively, and for the total volatile solids (TVS) were 68.50 and 71.80%, respectively. The CH 4 contents generated from co-digestion of the untreated and pretreated buffalo grass-manure were 48.32% and 50.36%, respectively. The CH 4 yields generated from co-digestion of the untreated and pretreated buffalo grass-manure were 328 and 385 L/kgTVS conversion, respectively. It was observed from the experiments that pretreatment of the buffalo grass prior to co-digestion provided system stability during biogas production. • Buffalo grass has high potential as a biomass source for biogas production. • Co-digestion of NaOH-pretreated buffalo grass-manure increases CH 4 yield. • CH 4 content and CH 4 yield are 50.36% and 387 L/kg TVS conversion. • COD and TVS conversion efficiency reach 62.76 and 71.80%. • System stability increases noticeably. [ABSTRACT FROM AUTHOR]

Community agricultural waste-to-energy management, especially in developing countries, can respond to sustainable development goals by the United Nations. Co-digestion techniques for waste from phytomass in fields as Napier grass (NP) and debris from consumption in the community as food waste (FW) into biogas production by conventional anaerobic digestion technology contribute to sustainable energy communities. However, lignocellulose requires proper pretreatment of the material type. Therefore, low sodium hydroxide (NaOH) concentration for Napier grass pretreatment and varying the co-digestion ratio with food waste from the community under conventional batch conditions were optimized to be economically cost-effective with elementary technology. The results showed the highest methane yield at 0.285 m3/kg VSadded at the 4% concentration of sodium hydroxide pretreatment with significant content of FW added with biomass. The best conditions of co-substrates can increase methane yields by up to 3.54 times compared to a single substrate. The energy and cost estimation based on energy consumption and chemical input cost showed that co-digestion with NaOH pretreatment could achieve the net benefits by increasing the biogas production (242 US$/tonne TS). This study confirms the application of waste management in agricultural communities that can be used as fuel in households to increase biogas and economic value. The authors expect this work to be a successful case study for further results that lack government financial support and limitations of advanced technology for a sustainable community. [ABSTRACT FROM AUTHOR]

Slaughterhouse activities generate large volumes of biodegradable organic wastes such as animal faeces, blood, fat, animal trimmings, paunch contents and urine. These wastes are mainly responsible for air, soil, and water pollution if untreated or poorly managed. In many developing countries, the common method adopted by most slaughterhouses in the disposal of these streams of wastes is landfilling which poses environmental challenges such as greenhouse gas emissions, bad odour and leachate management. Treatment using anaerobic digestion has been considered an appropriate method for treating slaughterhouse waste with high organic loads. These wastes are considered energy-rich and characterised by high concentration of carbohydrates, mainly in the form of lactose, as well as protein and lipids. However, high concentrations of ammonia, hydrogen sulphide and long chain fatty acids remain major inhibitors of methanogenic activities and are often responsible for digester upsets. On a broader note, suitable co-substrates depending on type and composition of feedstock, with appropriate percentage total solids and volatile solids, as well as carbon to nitrogen ratio, are very critical for effective degradation. This paper reviews the utilisation of slaughterhouse wastes as a potential feedstock for the production of methane-rich biogas. The interactive effects of key operational and environmental parameters for efficient process performance and stability are also presented to overcome the drawbacks of mono-digestion of slaughterhouse waste. [ABSTRACT FROM AUTHOR]

Anaerobic co-digestion of domestic sewage sludge with food waste as a substrate for biogas production and as a mean for waste management was conducted. The food waste was incorporated into the bioreactor as a cosubstrate semi-continuously via replacement mode and addition mode of operations in ratios up to 50%. The methane gas yield under the replacement mode of operation ranged from 295 to 1358 ml/gVSadded and from 192 to 462 ml/gVSadded for the replacement mode of operation and the addition mode of operation, respectively. The results indicate that the methane gas yield increases along with the percentage share of food waste in the feed. Anaerobic co-digestion under semi-continuous operation enabled handling large organic loadings compared to batch co-digestion processes. [ABSTRACT FROM AUTHOR]

Energy and waste disposal issues are calling for advanced recycling methods such as conversion of organic waste into biohydrogen and biomethane. Here we review factors that influence yields, such as pH, temperature, substrate composition, biocatalyst, nutrient content, volatile fatty acids concentration, organic loading rate, hydraulic retention time and C/N ratio. The optimum pH is 5.5–6 for hydrogen production, and 6.8–7.2 for methane production. Hydrogen yield improved highly after reducing the retention time from 72 to 20 h. The highest methane productivity was achieved with C/N ratio of 16–27. We also discuss methods to improve efficiency such as co-digestion, pre-treatment, application of additives and optimal digester design. Co-digestion synergizes the effects on microbial communities, balances the nutrients, reduces the inhibitory effects and improves the economic viability. Co-digestion has enhanced the productivity by 25–400% compared to mono-digestion. Acid pre-treatment is the best method for lignocellulose hydrolysis, followed by enzyme pre-treatment. Microwave pre-treatment enhances the biomethane production 4–7 times. The batch mode improves the substrate degradation efficiency and hydrogen production by 25% compared to the continuous mode. The addition of trace metals alters the hydrogenase activity during anaerobic fermentation. Reaction kinetics and metabolomics, bioaugmentation, digestate recirculation, frequent feeding and development of bioreactor systems for two-stage anaerobic digestion are also presented. [ABSTRACT FROM AUTHOR]

This study evaluated anaerobic digestibility and biogas production potential of microalgal biomass and food waste. Biochemical Methane Potential (BMP) assays were conducted to determine the biogas generation potential of microalgal biomass and food waste both separately and together. Results indicated that several algal species in the collected samples are among the major harmful algal bloom (HAB) taxa found in freshwaters in North America. Bio‐methane yields for mono‐digestion of microalgal biomass and food waste were found to be 131–188 and 430–542 ml of bio‐methane per gram of volatile solids (ml CH4/g VS), respectively; while bio‐methane yield for co‐digestion of microalgal biomass and food waste was 426–505 ml CH4/g VS. Co‐digestion of microalgal biomass and food waste resulted in up to 12.3% increase in methane production relative to mono‐digestion of these substrates. Statement of Industrial Relevance: Harmful algal blooms (HABs) have many adverse environmental impacts such as lowering dissolved oxygen concentrations, altering aquatic food webs, producing toxins, and taste‐and‐odor compounds. There has been a dramatic rise in the severity and geographical range of HABs with the increasing environmental degradation over the past century. This work provides a new insight in terms of integrating HABs disposal and valorization for bio‐methane generation as a renewable energy. Bioenergy generation from mechanically harvested HABs along with its environmental and resource‐conserving benefits are relevant to waste management and biogas industries. Significance: The results indicate that integrating mechanical harvesting of HABs with valorization of the collected algal biomass will increase its economic feasibility. Moreover, anaerobic co‐digestion of HABs and food wastes generate extra bio‐methane relative to mono‐digestion of these substrates by balancing the C:N ratio. [ABSTRACT FROM AUTHOR]

Featured Application: The application of this work is directly related to food processing industries such as slaughterhouses which produce high strength wastewater. An additional featured application is the opportunity for co-digestion where co-located industries, such as nearby beef feedlots, can develop synergistic partnerships in which waste can contribute to anaerobic digestion systems at slaughterhouse facilities to help optimise the process and also result in waste disposal for one industry and energy production and offsets for the other. This work represents and reviews a compilation of investigations into improving anaerobic digestion performance of high-strength wastewater in the Australian Red Meat Processing industry. The industry produces significant quantities of organic-rich wastewater which requires treatment prior to release to the environment. Anaerobic lagoons are a cost-effective method of waste treatment where land availability is not an issue; however, the high fat load in the wastewater can negatively impact the anaerobic lagoon system and result in compromised anaerobic digestion performance. This paper will discuss the importance of upstream primary pre-treatment and review a series of investigations focused on optimising digester performance and improving fat biodegradability. These studies include: 1. the effect of temperature and mixing; 2. the influence of feedstock trace element composition and supplementation, and; 3. the potential benefit from pre-treatments such as chemical, thermobaric, thermochemical and bio-surfactant. This paper discusses the implications of these findings for covered anaerobic lagoon operation and provides recommendations to promote optimum digester performance and future opportunities in adopting alternate anaerobic digestion technology options. Finally, the paper provides recent trends toward the use of other waste streams for co-digestion and discusses this in terms of digester optimization and technology options. [ABSTRACT FROM AUTHOR]

• Co-digestion of sewage sludge and organic waste for VFA production was studied. • Acetic acid dominated in short-term operation in batch mode. • An increasing proportion of organic waste increased valeric and caproic acid. • Caproic acid dominated during long-term operation in semi-continuous mode. • VFA-rich liquid achieved higher denitrification rate than acetate and methanol. Volatile fatty acids (VFAs) are intermediates of anaerobic digestion with high value and wide range of usage. Co-digestion of sewage sludge and external organic waste (OW) for VFA production can help achieve both resource recovery and ensure sustainable and innovative waste management. In view of this, the effect of substrate proportions on VFA production from co-digestion of primary sewage sludge and OW is studied. Long-term operation in a semi-continuous reactor was performed to assess the resilience of such a system and the VFA-rich effluent was tested for its ability to be used as carbon source for denitrification. Co-digestion was initially carried out in batch reactors with OW proportion of 0%, 25%, 50%, 75%, 100% in terms of COD and scaled up in a semi-continuous reactor operation with 50% OW. In the short-term operation in the batch mode, acetic acid dominated, however, increasing OW fraction resulted in increased valeric and caproic acid production. Moreover, in the long-term semi-continuous operation, caproic acid dominated, accounting for ≈55% of VFAs. The VFA-rich effluent from the semi-continuous reactor achieved the highest denitrification rate as a carbon source when compared with acetic acid and methanol. The results demonstrate that co-fermentation can increase VFA yield and shift products from acetic acid to caproic acid in long-term operation and the VFAs can be used within wastewater treatment plants to close the loop. [ABSTRACT FROM AUTHOR]

A considerable quantity of waste is being generated from fish markets and harbors of coastal regions in India. Presently, there is no systematic and sustainable ways of disposal which leads to unscientific handling and dumping in landfills. Upon considering the bottlenecks associated with the anaerobic digestion of fish waste (FW) as sole substrate, co-digestion with vegetable wastes (VW) could be an effective alternative to mitigate the problem along with simultaneous treatment of two different waste streams. In this study, an attempt has been made to examine the co-digestion efficiency of FW with VW for which three trials viz., T1 (mono-digestion of VW), T2 (mono-digestion of FW) and T3 (co-digestion of VW and FW) were conducted to analyze the biomethane production potential, degree of biodegradability and pH stability. From the obtained results co-digestion was found to yield 463 ± 6.73 L/kg VSfed of biomethane which is 24.13% and 22.32% higher as compared to VW (373 ± 4.94 L/kg VSfed) and FW (378 ± 4.55 L/kg VSfed) respectively. Maximum biodegradability based on organic carbon destruction was found to be 70% in co-digestion followed by mono-digestion of VW (58.8%) and FW (64%). Prevalence of acidification and ammonification in mono-digestion of VW and FW were reflected by physiological pH of 5.4 ± 0.41 and 8.3 ± 0.32 respectively. In co-digestion process pH was observed to be 7.3 ± 0.70 that indicated high stability and thus enhanced the biomethane yield. Co-digestion of these organic wastes could enhance the efficiency of methane production and therefore presents a unified waste management option. [ABSTRACT FROM AUTHOR]

The production of biogas from organic waste has attracted considerable interest as a solution to current energy and waste management challenges. This study explored the methane (CH 4) production potential of swine manure (SM), food waste (FW), and tomato waste (TW) and the changes in the microbial community involved in the anaerobic digestion process. The results revealed that the CH 4 production potentials of the four kinds of SM samples were influenced by the characteristics of SM (e.g., age and storage period). Among the four kinds of SM samples, the CH 4 yield from the manure directly sampled from primiparous sows (SM3) was the highest. The CH 4 yield was significantly improved when SM3 was co-digested with FW, but not with TW. The addition of SM fostered a stable CH 4 production community by enhancing the interaction between methanogens and syntrophic bacteria. Furthermore, the addition of FW as a co-substrate may improve the functional redundancy structure of the methanogenesis-associated network. Overall, the characteristics of SM must be considered to achieve consistent CH 4 yield efficiency from anaerobic digestion since CH 4 production potentials of SM can be different. Also, the contribution of co-substrate to the synergistic relationship between methanogens and syntrophic bacteria can be considered when a co-substrate is selected in order to enhace CH 4 yield from SM. [Display omitted] • Fresher sow manure yielded more CH 4 than aged or growing pig manures. • Food waste not tomato waste yielded more CH 4 when digested with manure. • Swine manure (SM) was a beneficial substrate for methanogenic community. • SM led to a robust and stable co-occurrence network of methanogens. • Food waste diversified methanogens enhancing functional redundancy. [ABSTRACT FROM AUTHOR]

Wastewater and sewage sludge contain organic matter that can be valorized through conversion into energy and/or green chemicals. Moreover, resource recovery from these wastes has become the new focus of wastewater management, to develop more sustainable processes in a circular economy approach. The aim of this review was to analyze current sewage sludge management systems in Scandinavia with respect to resource recovery, in combination with other organic wastes. As anaerobic digestion (AD) was found to be the common sludge treatment approach in Scandinavia, different available organic municipal and industrial wastes were identified and compared, to evaluate the potential for expanding the resource recovery by anaerobic co-digestion. Additionally, a full-scale case study of co-digestion, as strategy for optimization of the anaerobic digestion treatment, was presented for each country, together with advanced biorefinery approaches to wastewater treatment and resource recovery.

To investigate the effect of seaweed (SW) addition on anaerobic co-digestion of food waste (FW) and sewage sludge (SS), batch experiments were conducted at various substrate concentrations (2.5, 5.0, 7.5, and 10.0 g volatile solids (VS)/L) and mixing ratios ((FW or SS):SW = 100:0, 75:25, 50:50, 25:75, and 0:100 on a VS basis). The effect of SW addition on FW digestion was negligible at low substrate concentration, while it was substantial at high substrate concentrations by balancing the rate of acidogenesis and methanogenesis. At 10 g VS/L, CH4 production yield was increased from 103 to 350 mL CH4/g VS by SW addition (FW:SW = 75:25). On the other hand, SW addition to SS enhanced the digestion performance at all substrate concentrations, by providing easily biodegradable organics, which promoted the hydrolysis of SS. khyd (hydrolysis constant) value was increased from 0.19 to 0.28 d-1 by SW addition. The calculation showed that the synergistic CH4 production increment by co-digesting with SW accounted for up to 24% and 20% of total amount of CH4 production in digesting FW and SS, respectively. [ABSTRACT FROM AUTHOR]

Organic solid wastes (OSWs) should be regarded as valuable resources rather than dead‐end landfill waste that causes public health and odor concerns. Anaerobic digestion (AD) is an ideal approach for managing organic solid waste issues and involves using a group of anaerobic microorganisms to transform OSWs into useful products. In this review, over 100 publications related to AD of OSWs have been compiled, discussed, and analyzed. A comprehensive analysis of the environmental and safety impacts of AD, its key environmental factors, co‐digestion, and pretreatment, as well as the AD of OSWs by various anaerobic microbes uncovered by high throughput sequencing‐based approaches, is presented. The purpose of this review is to provide an outline of the current knowledge of AD processes from a multi‐angle perspective. A comprehensive understanding of AD of OSWs and genome‐enabled biology development could be helpful for providing up‐to‐date knowledge of AD, developing it, overcoming its drawbacks and, ultimately, improving global waste control for more efficient environmental management. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The VFAs were main inhibition factors on methane production. • The threshold VFA inhibition concentration on methane production was 16.5–18.0 g/L. • The possible functions of some bacteria were first estimated. • Syntrophic oxidation with hydrogenotrophic methanogenesis was the dominant pathway. • An inoculum rate of 50% & FW/PM ratio of 50:50 was preferable operation conditions. Abstract Compared with wet digestion, dry digestion of organic wastes reduces reactor volume and requires less energy for heating, but it is easily inhibited by high volatile fatty acid (VFA) or ammonia concentration. The inhibition on methane production kinetics during dry co-digestion of food waste and pig manure is rarely reported. The aim of this study was to explore the inhibition mechanisms and the microbial interactions in food waste and pig manure dry co-digestion systems at different inoculum rates (25% and 50% based on volatile solids) and food waste/pig manure ratios (0:100, 25:75, 50:50, 75:25 and 100:0 based on volatile solids). The results showed that the preferable operation conditions were obtained at the inoculum rate of 50% and food waste/pig manure ratio of 50:50, with a specific methane yield of 263 mL/g VS added. High VFA concentration was the main inhibition factor on methane production, and the threshold VFA inhibition concentrations ranged 16.5–18.0 g/L. Syntrophic oxidation with hydrogenotrophic methanogenesis might be the main methane production pathway in dry co-digestion systems due to the dominance of hydrogenotrophic methanogens in the archaeal community. In conclusion, dry co-digestion of food waste and pig manure is feasible for methane production without pH adjustment and can be operated stably by choosing proper operation conditions. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the performance and the kinetic constants of anaerobic mesophilic CSTR reactors run at increasing organic loading rates (OLR). The reactors were co-digesting dairy cow slurry (DCS) and municipal food waste (MFW). The supply of DCS was held constant, while the supply of MFW was increased in the four reactors: 0, 14.0, 24.5 and 32.2% (ww). Degradation of organic matter, specific methane yield per mass unit converted organic matter, and the kinetics of the process were used to investigate the performance of the reactors. While the hydraulic retention time was decreased from 25.9 to 17.5 days, the specific methane yield increased from 0.21 to 0.44 l CH 4 · gVS −1 . The relationship between the kinetic constant and the OLR was found to be linear. The efficiency of the process increased when the OLR increased in this experiment. [ABSTRACT FROM AUTHOR]

An overall interaction is manifested between wastewater and solid waste management schemes. At the Laboratory of Environmental Engineering (LISA) of the University of Padova, Italy, the scientific and technical implications of putting into practice a decentralized waste and wastewater treatment based on the separation of grey water, brown water (BW – faecal matter) and yellow water (YW – urine) are currently undergoing investigation in the Aquanova Project . An additional aim of this concept is the source segregation of kitchen waste (KW) for subsequent anaerobic co-digestion with BW. To determine an optimal mixing ratio and temperature for use in the treatment of KW, BW, and eventually YW, by means of anaerobic digestion, a series of lab-scale batch tests were performed. Organic mixtures of KW and BW performed much better (max. 520 ml CH 4 /g VS) in terms of methane yields than the individual substrates alone (max. 220 ml CH 4 /g VS). A small concentration of urine proved to have a positive effect on anaerobic digestion performance, possibly due to the presence of micronutrients in YW. When considering high YW concentrations in the anaerobically digested mixtures, no ammonia inhibition was observed until a 30% and 10% YW content was added under mesophilic and thermophilic conditions, respectively. [ABSTRACT FROM AUTHOR]

The aim of the mechanical pretreatment in case of anaerobic digestion of biowaste is to produce a substrate without impurities. To facilitate a failure free operation of the anaerobic digestion process even small impurities like stones or sand should be separated. As a result of an insufficient pretreatment or impurities separation, plant malfunctions, increased equipment wear or pipe clogging are reported. Apart from grit chambers or pulper systems, a hydrocyclone is a cost-efficient and space-saving option to remove impurities. The aim of this work was to investigate the efficiency of hydrocyclones for the separation of impurities. Two hydrocyclones at two different plants were investigated regarding their capability to separate the small inert impurities from pretreated source separated biowaste. In plant A, the hydrocyclone is part of the digester system. In plant B, the hydrocyclone is part of the biowaste pretreatment line (after milling and sieving the biowaste) before digestion. Separation rates of inert impurities such as stones, glass and sand were determined as well as the composition of the concentrated solids separated by the hydrocyclone. Due to the heterogeneity of the biowaste the impurity separation rates showed variations, therefore the following mean results were obtained in average: the investigated hydrocyclones of plant B, part of the biowaste treatment, separated more than 80% of the inert impurities in the waste stream before anaerobic digestion. These impurities had a size range of 0.5–4 mm. The hydrocyclone integrated in the digester system of plant A showed separation rates up to 80% only in the size range of 2–4 mm. [ABSTRACT FROM AUTHOR]

Anaerobic digestion (AD) of the organic fraction of municipal solid waste (OFMSW) has gained great interest in the last few decades. Presently, among the various municipal solid waste management (MSWM) techniques, such as sanitary land-filling, aerobic or anaerobic composting, and thermal incineration, AD is being considered as the most techno-economically viable method owing to its many advantages. AD not only serves to efficiently manage and treat an enormous quantity of OFMSW but also acts as a convenient source of non-conventional energy. The methane generated via AD of OFMSW serves as a potent substitute for fossil-based fuels. Given the current global energy crisis, this technology may be a welcome boost to the global energy demand. In this review an attempt has been made to provide a comprehensive understanding of: (i) the origin and scope of AD of OFMSW; (ii) the potential of AD for OFMSW stabilization; (iii) various pilot and bench-scale studies conducted hitherto; (iv) the process design aspects of AD of OFMSW; (v) the potential of energy recovery from AD of OFMSW; and (vi) the past experiences of AD of OFMSW. This review also delves into the critical issues that govern the process of AD in stabilizing OFMSW. In addition, the compatibility of AD for MSWM in the Indian scenario compared to other classical methodologies, such as landfilling, composting, thermal incineration, and pyrolysis or gasification, is highlighted. An overview of the overall future prospect of AD of OFMSW is discussed. [ABSTRACT FROM AUTHOR]

The increasing production of food waste worldwide and new international regulations call for the development of new technologies to treat this biowaste. Anaerobic processes are able to treat efficiently organic wastes, producing at the same time different value-added compounds. In addition, due to the lower costs and environmental impacts associated with these processes when compared to other options, they are among the most promising technologies for food waste treatment. This article reviews the state-of-the-art dealing with treatment of food waste by anaerobic processes, with emphasis on the most recent research carried out. The different processes that are assessed are anaerobic digestion for methane production, anaerobic fermentation for hydrogen and/or volatile fatty acids production and 2-stage systems. The primary issues associated with each alternative are presented, paying special attention to accumulation of ammonia and volatile fatty acids in the reactor. In addition, the latest developments to overcome the complications of each system are also described, focusing on how they improve its stability and performance. Moreover, the relevant economic and environmental research has also been reviewed, including several life cycle analyses that compare anaerobic processes with other technologies used for food waste treatment. Different case studies are also presented. Finally, recommendations for future research for the anaerobic processes studied and options for process integration are discussed. Moving towards the idea of a circular economy, a potential biorefinery for food waste valorization is also proposed. [ABSTRACT FROM AUTHOR]

This paper describes a semi-continuous laboratory-scale investigation of a potential co-substrate for mesophilic anaerobic sludge digestion in a municipal wastewater treatment plant. A feed liquid produced from source-sorted municipal organic waste by pretreatment with a screw press was subjected to the investigation. Quantities produced in press trials as well as the composition of the feed liquid are presented. Mass balances for N, P and chemical oxygen demand are given in order to verify the methane production of the feed liquid in co-digestion with sewage sludge at mesophilic conditions. Hydraulic retention time of the reactors were 14.7 to 16 d and organic loading rates were 1.5 to 2.7 kg volatile solids (VS) per cubic metre per day. The pretreatment by screw press is compared to the production of feed liquids with pulper-based pretreatment processes. While the addition of the feed liquid increased methane production by about 345 ml CH4/g VSin, total solids of the feed liquid were reduced to about 63%. With respect to co-digestion at municipal wastewater treatment plants, several risks associated with the investigated feed liquid are outlined. [ABSTRACT FROM AUTHOR]

The increased use of fossil fuel for energy consumption poses threat to the environment both locally and globally. Fodder residues rich in lignocellulose often form a major portion of farmyard waste. The present study investigates the suitability of co-digestion of pre-treated fodder residues in anaerobic digestion for production of biogas. This study was conducted to fi nd out the biogas production potential of different pre-treated fodder residues codigested along with cow dung. The trials were carried out by loading the substrates, in portable fl oating drum biogas plants of 0.5 m3 capacity. Daily gas yield from the plant was recorded for a period of 42 days. The study recommends that biogas is not just a renewable energy source but also an appropriate way of managing waste, having potential to replace fossil fuel. [ABSTRACT FROM AUTHOR]

Co-digestion of organic waste and wastewater is receiving increased attention as a plausible waste management approach toward energy recovery. However, traditional anaerobic processes for co-digestion are particularly susceptible to severe organic loading rates (OLRs) under long-term treatment. To enhance technological feasibility, this work presented a two-stage Anaerobic Membrane Bioreactor (2 S-AnMBR) composed of a hydrolysis reactor (HR) followed by an anaerobic membrane bioreactor (AnMBR) for long-term co-digestion of food waste and kitchen wastewater. The OLRs were expanded from 4.5, 5.6, and 6.9 kg COD m−3 d−1 to optimize biogas yield, nitrogen recovery, and membrane fouling at ambient temperatures of 25–32 °C. Results showed that specific methane production of UASB was 249 ± 7 L CH 4 kg−1 COD removed at the OLR of 6.9 kg TCOD m−3 d−1. Total Chemical Oxygen Demand (TCOD) loss by hydrolysis was 21.6% of the input TCOD load at the hydraulic retention time (HRT) of 2 days. However, low total volatile fatty acid concentrations were found in the AnMBR, indicating that a sufficiently high hydrolysis efficiency could be accomplished with a short HRT. Furthermore, using AnMBR structure consisting of an Upflow Anaerobic Sludge Blanket Reactor (UASB) followed by a side-stream ultrafiltration membrane alleviated cake membrane fouling. The wasted digestate from the AnMBR comprised 42–47% Total Kjeldahl Nitrogen (TKN) and 57–68% total phosphorous loading, making it suitable for use in soil amendments or fertilizers. Finally, the predominance of fine particles (D10 = 0.8 μm) in the ultrafiltration membrane housing (UFMH) could lead to a faster increase in trans -membrane pressure during the filtration process. [Display omitted] • Co-digestion of wastewater and kitchen waste using 2 S-AnMBR were surveyed • Hydrolysis and acetogenesis stages enhanced the performance of methanogenesis stage • Short SRT of the 2nd stage reduced digestate solid accumulation in AnMBR • Predominance of colloids (<1 μm) was a challenge for membrane fouling control [ABSTRACT FROM AUTHOR]