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The potential improvement in methane recovery and reaction kinetics from different mixes of potato peel (PP) and pig manure (PM) in a single stage anaerobic co-digestion/mono-digestion process was investigated in a laboratory study. The highest methane yield of 231 mL/g TCODadded was observed in the 50:50 mix of potato peel and pig manure. Compared to the mono-digested substrates, co-digestion of PP and PM at 75:25, 50:50, and 25:75 synergistically improved methane yield by 17%, 25%, and 11%, respectively. The co-digested mixes also produced methane at a faster rate, with the fastest methane production rate occurring at the 50:50 mix. Thus, co-digestion of potato peel and pig manure enhanced the methane yield and reaction kinetics. Hence, co-digestion rather than mono-digestion should be actively considered when a carbon rich waste (such as potato peel) and nutrient rich waste (such as pig manure) are available within reasonable proximity.

In this study, spoiled maize silage (SMS) and cattle manure were co-digested at five different mixtures by the Hohenheim Batch Yield Test unit under mesophilic conditions to explore biogas production possibilities of these wastes together. The mixtures were 100% cattle manure, 100% SMS, 85% cattle manure + 15% SMS, 70% cattle manure + 30% SMS, and 55% cattle manure + 45% SMS. Chemical properties of raw materials and mixtures, including crude fat, dry matter, organic matter, and acid detergent fiber (ADF) contents were determined. As the amount of SMS in the mixtures increased, biogas and methane production increased. The highest cumulative specific biogas and methane production were determined for 100% SMS as 0.62 Nm3 kg-1 organic matter (OM) and 0.31 Nm3 kg-1 OM, respectively, where Nm3 is the volume of biogas under normal conditions. Methane content of the mixture containing SMS (49.99% to 51.87%) was higher than that of cattle manure only (44.01%). Furthermore, the mixtures which had lower ADF content yielded more methane and biogas. In conclusion, the efficiency of biogas and methane production can be increased by applying the co-digestion technique.

Sustainable treatment of fecal matter is a long-standing challenge in sanitation, particularly in developing countries. Although recent developments have seen the evolution of innovative onsite sanitation technologies, the treatment of fecal waste collected still remains a daunting task. This study evaluated the effect of formulated feedstock: fecal matter from urine-diverting dry toilets and kitchen waste (1:0, 1:1, 2:1, 4:1, and 0:1) on waste weight reduction, Hermetia illucens’ larval weight gain, and crude protein content during co-digestion. Samples were collected after every 2 days for larval weight determination and protein content analysis using the Kjeldahl method of nitrogen determination. The waste reduction index (WRI) was determined after 50% pupation. The larvae grew on all substrates yielding 32.97–38.6% dry matter (DM) protein content and larval weight ranging from 1.12 to 1.70 g per five larvae. Results indicate that a 1:1 co-digestion ratio resulted in a high WRI (3.61), DM crude protein content (38.6%), and larval weight (1.70 g per five larvae). This study used the circular economy-based approach which provides a win–win situation to sanitation provision and environmental management while realizing products with potential for livelihood improvement. HIGHLIGHTS A system for simultaneous co-digestion of the urine-diverting dry toilet fecal matter and kitchen waste for animal feed protein ingredients was investigated.; Hermetia illucens’ larvae developed in all rearing substrates provided despite the substrates' elemental composition.; Co-digestion of fecal matter increased process performance of H. illucens’ larvae.; Co-digestion significantly increased larval protein content and weight.

The generation of anthropogenic wastes, such as household human feces and kitchen waste, has resulted in a severe environmental impact. Sustainable management approaches to address disposal challen...

The dry anaerobic co-digestion is progressively implemented for treating manure with different agricultural wastes. Nanoparticles (NPs) were hypothesized to accelerate the dry anaerobic co-digestion process, which increases the biogas and methane production. The objective of this study is to produce biogas using dry anaerobic co-digestion of manure and whey with addition of photoactivated cobalt oxide nanoparticles (Co3O4 NPs). The effects of NPs on biogas and methane production were investigated using a specially designed batch anaerobic system, where a series of 2-L biodigesters were manufactured and implemented. The treatments were: mono-digestion of manure (control), co-digestion of manure with whey, co-digestion of manure and whey and 1, 2 and 5 mg/l of photoactivated Co3O4 NPs, respectively. The results revealed that the greatest specific production of biogas and CH4 (P

The capacity of a heat-treated sludge (HTS) to produce hydrogen from the mono- and co-digestion of corn (NW, pH 13.1) and brewery (BW, pH 3.8) wastewater was evaluated. The co-digestion of NW and BW was conducted with ratios (NW/BW) from 40/60 to 80/20 (vol/vol) at pH 6 and under different initial pH values (from 5.8 to 12.3) according to the substrates mixtures. With the initial pH adjusted to 6, the highest production (302 mL) occurred for the mono-digestion of NW, but hydrogen was produced in all incubations. For incubations under variable pH values, the highest hydrogen production was obtained with the ratio 60/40 (270 mL), followed by the ratio 65/35 (260 mL) with pH values of 10.8 and 10.4, respectively. The initial pH influenced the kinetic parameters, especially on maximum production and lag phase. For the ratio 60/40, with an alkaline pH value (10.4), the lag phase was delayed up to 122 h, but the highest volume of hydrogen was obtained with this condition. The Clostridium genus, present in all samples, could be associated as the main responsible for hydrogen production. Besides, the presence of Burkholderia genus, previously related to hydrogen production, was identified as the main involved in the culture at pH 10.8.

The objective of this study is to evaluate the influence of the addition of garden waste (GW) on the performance of food waste (FW) anaerobic digestion. In this regard, a bench scale experiment was performed via biochemical methane potential test. The reactors were composed of flasks with a total volume of 310 mL and a useable volume of 120 mL, containing the waste mixtures in the different studied conditions. All reactors were incubated under 36 °C. A factorial design was used to evaluate the influence of three factors on methane production: inoculum and substrate ratio (I:S), volatile solid (VS) content of the mixture and type of substrate. The results indicated that the condition referred to an I:S ratio of 1:1, higher VS content (VSmix) and only FW as a substrate achieved the higher methane production and differed significantly from the others. This combination resulted in 67.5% of VS removal, 509 NmL of cumulative CH4 and a specific methane yield of 159 NmLCH4 gVS−1. The results obtained in this research indicated that the addition of GW on the anaerobic digestion of FW did not positively influence the methane production.

The Circular and Green Economy principles is inspiring new approaches to municipal wastewater treatment plants (MWWTPs) design and operation. Recently, an ever-growing interest is devoted to exploring the alternatives for switching the WWTPs from being able to ‘simply’ removing contaminants from water to biorefinery-like plants where energy and material can be recovered. In this perspective, both wastewater and residues from process can be valorised for recovering nutrients (N and P), producing value added products (i.e. biopolymers), energy vectors and biofuels (i.e. bio-H2, bio-CH4 and bioethanol). As an additional benefit, changing the approach for WWTPs design and operation will decrease the overall amount of landfilled residues. In this context, the present research is aimed at evaluating the CH4 production potential of MWW screening units’ residues. While such a stream is typically landfilled, the expected progressive increase of biodegradable matter content due to the ban on single-use plastic along with the boost of bioplastics makes the investigation of different biochemical valorisation routes more and more interesting from an environmental and economical perspective. Thus, a full-scale data collection campaign was performed to gain information on screening residues amount and properties and to analyse the relationship with influent flowrate. The most relevant residue properties were measured, and lab-scale tests were carried out to evaluate the bio-CH4 potential.

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 co-substrate 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.

Anaerobic digestion (AD) under psychrophilic temperature has only recently garnered deserved attention. In major parts of Europe, USA, Canada and Australia, climatic conditions are more suited for psychrophilic (20 ℃) rather than mesophilic (35 - 37 ℃) and thermophilic (55 - 60 ℃) AD. Low temperature has adverse effects on important cellular processes which may render the cell biology inactive. Moreover, cold climate can also alter the physical and chemical properties of wastewater, thereby reducing the availability of substrate to microbes. Hence, the use of low temperature acclimated microbial biomass could overcome thermodynamic constraints and carry out flexible structural and conformational changes to proteins, membrane lipid composition, expression of cold-adapted enzymes through genotypic and phenotypic variations. Reduction in organic loading rate is beneficial to methane production under low temperatures. Moreover, modification in the design of existing reactors and the use of hybrid reactors have already demonstrated improved methane generation in the lab-scale. This review also discusses some novel strategies such as direct interspecies electron transfer (DIET), co-digestion of substrate, bioaugmentation, and bioelectrochemical system assisted AD which present promising prospects. While DIET can facilitate syntrophic electron exchange in diverse microbes, the addition of organic-rich co-substrate can help in maintaining suitable C/N ratio in the anaerobic digester which subsequently can enhance methane generation. Bioaugmentation with psychrophilic strains could reduce start-up time and ensure daily stable performance for wastewater treatment facilities at low temperatures. In addition to the technical discussion, the economic assessment and future outlook on psychrophilic AD are also highlighted.

Anaerobic digestion is a well-established technology for energy production and to diminish the environmental impact of different types of organic residues, which are mainly produced from human activities (processing food) but also from other recent activities related to energy generation processes (biofuel production). In the present study, mango organic residues: mango peel (MP) and mango seed (MS), and microalgal residue biomass (MRB) were co-digested in different proportions using a mixture design. The optimized mixture proportions of 60:20:20% of MP, MS and MRB, respectively, were determined by applying the simplex-centroid method to reach the highest biochemical methane potential (BMP); additionally, the mixture with the lowest BMP was selected (40:20:40%). The effects of thermal, physical and biological pretreatments of the selected mixtures were evaluated in order to improve its BMP. However, any pretreatment showed an improvement for the mixture 60:20:20, whereas the mixture 40:20:40 achieved an increment of 160.1, 72.5 and 96.4%, when the substrates were pretreated by thermal, physical and biological, respectively. The mixture optimization of these substrates shows an alternative way to reduce the environmental impact, due to their potential use in co-digestion process for biogas production.

This paper mainly introduces the potential of methane yield from co-digestion of primary sludge (PS) and the proposed new waste materials of sugarcane leaves (SL) and Corchorus stalks (CS) in Egypt. This paper includes three parts. In the first part, anaerobic co-digestion of PS, SL, and CS at different carbon-to-nitrogen (C/N) ratios was studied to determine the best C/N ratio. The results indicated that the maximum cumulative methane yields (CMYs) were observed at a C/N ratio of 18, which was associated with the highest volatile solid (VS) removal rate (74.41%). In the second part, the effect of using two types of inoculum (fresh cow manure (CM) and rumen content from slaughterhouses (RS)) on increasing the production of methane was investigated. Clearly, using CM as inoculum showed a superiority of the production of methane from co-digestion of PS, SL, and CS. The maximum CMYs were observed using the CM as inoculum from co-digestion of PS, SL, and CS. It was higher about 1.26 times more CMY using RS as inoculum. In the third part, the possibility of enhancing biogas yields from semi-continuous co-digestion of PS, SL, and CS using different organic loading rates (OLR) of 0.5, 1.0, and 2.0 was conducted. The highest biogas production rate was observed at an OLR of 1.0 gVS/(Lreactor.d) that coincided with the optimum VS removal rate. Statistical analysis of the results was conducted using analysis of variance (ANOVA) test, and the C/N ratio of 18 is statistically the best enhanced ratio. Overall, the feasibility of maximizing the methane productivity considering the anaerobic co-digestion of PS, SL, and CS under the optimal operating conditions and configuration was proved.

The huge agro-industrial biomass wastes had engendered the need for appropriate treatment technology, which could be deployed to sustainably manage and convert them to useful by-products. Consequently, the comparative anaerobic co-digestion effects of some agricultural biomass on their digestates biochemical properties were conducted. Twelve (12) replicates slurries from four mixing ratios of maize cob, poultry droppings and cow dung (1:0, 1:0, 1:0 and 1:1:1) as treatments TA, TB, TC and TD respectively, were separately digested in 13.6L locally fabricated batch-digester reactors, for eight weeks. Proximate and amino acids constituents were evaluated by standard procedure prior to and at post anaerobic digestion (AD). The biogas yields followed the sequence of TD (2200.7ml/kg) > TB (2197.9ml/kg) >TC (2079.0ml/kg) > TA (1713.2ml/kg), showing co-substrate effects. Proximate assay depicted a decrease in crude lipid across the treatments, with TC (86.82%) and TD (64.66%) as highest and lowest values. Crude fiber and nitrogen free extract had similar observation, apart from TB and TC with increased values. Percentage moisture and percentage ash contents increased across treatments. Carbon - Nitrogen ratio reduction (C/N Reduction) was in the range of 12.94 -85.79%. The Percentage chemical oxygen demand reduction (CODR), followed the order of TA (46.81%) > TB (34.15) >TC (25.81%) >TD (8.00%). There was increased histidine, glycine, cystine, methionine, total nonessential amino acids (TNEAA) and total aromatic amino acids (TArAA), with decrease in aspartic acids and serine. Percentage arginine, threonine, glutamic acid, proline, alanine, isoleucine, tyrosine, total amino acids (TAA) and total essential amino acid (TEAA) decreased only in TB. While, only TA had Percentage increased lysine (25.00%), valine (40.98%) and TArAA (6.13%), with phenylalanine unaffected (0.00%), Percentage leucine of TB (60.14%) and TD (23.08%) were reduced after AD. The process had revealed the alternative waste management, energy options, and useful industrial by-products for agro-allied industries.

Co-digestion is a well-established strategy to maximise the capacity of anaerobic digestion in wastewater treatment plants (WWTPs). Many tools have been developed to optimise the blend composition. However, the logistics associated with each component of the blend remain a relatively unexplored field, which can yield significant planning challenges. In this paper, an ant colony optimisation based approach is proposed to address these challenges. The proposed algorithm maximises an objective function composed of a first term related to the quality of the sludge and a second term related to the distance between the sludge generator and the anaerobic co-digester. The algorithm successfully optimises the blend composition by considering the related logistics, achieving an optimum blend with an approximately 18% volume of co-substrate. The approach presented here has been used to plan co-digestion using real data from an actual sanitation network composed of 13 WWTPs in the area of the Besos river basin in Catalonia, and an optimised co-digestion planning strategy with a waste management cost reduction of 77% was obtained

Anaerobic co-digestion (AcoD) of grease trap waste (GTW) and sewage sludge (SS) is an attractive management option for GTW valorisation and the transition to energy-neutral wastewater treatment plants (WWTPs). The main constraints that limit the direct use of GTW as a co-substrate in WWTP anaerobic digesters are the high content of non-disabled materials (floating plastics and fibres) and the low anaerobic biodegradability rates. This study assessed a single-step alkali and sieving pre-treatment of GTW at a low temperature (

This study investigated the performance of anaerobic co-digestion (AcoD) of pig manure and food waste on the reduction of antibiotic resistomes under wet and dry AcoD conditions. High-throughput quantitative PCR technology was utilized for a comprehensive assessment of the performances of the two processes. The results show that dry AcoD with a total solids (TS) content of 20% effectively reduced total antibiotic resistance genes (ARGs) by 1.24 log copies/g wet sample, while only 0.54 log copies/g wet sample was reduced in wet AcoD with a TS content of 5%. Dry AcoD was more efficient in reduction of aminoglycosides, multidrug and sulfonamide resistance genes compared with the reduction of other classes of ARGs. Dry AcoD caused a significant reduction of ARGs with resistance mechanisms of efflux pump and antibiotic deactivation. In contrast, there was no obvious difference in reductions of ARGs with different resistance mechanisms in wet AcoD. Network analysis showed that ARGs were significantly correlated with mobile genetic elements (MGEs) (Spearman's r 0.8, P 0.05), as well as microbial communities. Enrichment of ARGs and MGEs was found at the early period of AcoD processes, indicating some ARGs and MGEs increased during the hydrolysis and acidogenesis stages. But after a long retention time, their abundances were effectively reduced by dry AcoD in the subsequent stages.

The use of poultry manure (PM) in anaerobic digestion applications at high PM proportions is very limited due to its high nitrogen content since high levels of ammonia in the feedstock can lead to unstable and sub-optimal anaerobic digestion operation. This study investigated three methods to improve methane potential from PM at high PM proportions: (1) co-digestion of PM with a mixed substrate (MS) of a cheese factory and coffee-ground wastes at PM:MS ratios of 100:0, 75:25, 50:50, 25:75, and 0:100; (2) two-stage anaerobic digestion of PM and MS at PM:MS ratios of 100:0, 75:25, and 50:50, and (3) a novel post-hydrolysis ammonia stripping at pH 10 and 55 °C. The results indicated that co-digestion increased the methane potential in the samples due to reduced ammonia levels. A two-stage anaerobic digestion system further improved the methane potential by 21 and 41% in the cases of PM:MS at 100:0 and 75:25, while no improvement was observed in the case of PM:MS at 50:50. Post-hydrolysis ammonia stripping under the tested conditions achieved 79.2, 69, and 78.6% ammonia removal in PM:MS of 100:0, 75:25, and 50:50 and improved methane potential by 200, 150, and 64% when compared with the untreated samples.

Microalgae are a non-food grade, fast-growing, and non-land competitive biomass with relatively high energy content. The high lipid and mineral contents of microalgae render it beneficial for the production of biofuels and value-added products. The complete energy-effective harnessing of microalgae potentials concerning biodiesel production is faced with drawbacks because of the energy-intensive steps required to harvest and dry microalgae. The limitations have impelled the search for alternative and low-cost utilization of microalgae in wet form for biofuel production. Anaerobic digestion (AD) is among the wet techniques for the valorization of microalgae that is gaining immense research attention because of its simplicity. Also, the products can be recycled to reduce material costs. This review is focused on the recent trends and comparison of the AD process to maximize energy recovery from microalgae biomass and co-digestion of microalgae waste coupled to biodiesel production (after lipid extraction), respectively. The yield of methane gas in these two processes is compared and the pros and cons of biogas production using microalgae biomass and microalgae waste considering that the former produces biofuels and the later value-added products are discussed.

This work investigated the potential of generating biogas from mono-digestion of various substrates such as food and fruit waste (e.g., durian shell, dragon fruit peel and pineapple peel) and co-digestion in different combinations of a co-substrate as food waste as well as different types of fruit waste (durian shell, dragon fruit peel and pineapple peel). The mixture of food waste and fruit waste ratio varied as follows: 75:25, 50:50 and 25:75, which was based on weight. The batch experiments were carried out using 125 ml anaerobic digesters and were incubated for 50 days. For a mono-substrate, food waste produced the highest amount of methane gas (60.63 ± 1.02 ml/gvs) followed by durian shell (34.93 ± 1.30 ml/gvs), pineapple peel (31.70 ± 1.60 ml/gvs), and dragon fruit peel (30.12 ± 1.20 ml/gvs), respectively. The highest amount of methane gas came from food waste mixed with durian shell (FW75:D25), and it was on a higher level than food waste mixed with dragon fruit peel (FW75:DF25) and pineapple peel (FW75:P25). The highest methane gas production of co-digestion which was observed at the proportion of food waste and durian shell was 75:25 and produced higher content of methane gas than the highest methane gas production of mono-digestion (food waste) according to the high organic compound and optimum pH value in the system. The results showed that the co-digestion of durian shell and food waste improved methane production and reduced the startup time compared with their mono-digestion. On the other hand, pineapple peel was not suitable for co-digestion with food waste due to a decreasing pH value in the system.

There has been an increasing interest in continuous base-load low-carbon renewable energy generation in the United States. Several technologies have been developed to convert biomass into energy, a...

Anaerobic digestion found limited use in sludges from industrial wastewater treatment plants (WWTPs). So, it is of interest to assess the biodegradability and co-digestion performance of industrial sludges of biological origin alone and when mixed with municipal sludge. In this study, sludge from two different organized industrial districts (OIDs) and textile industry WWTPs are individually mixed with municipal sludge with and without ultrasound pretreatment to investigate their energy production potential and digestibility using biochemical methane potential tests. Sludges were used at different mass ratios in reactors with F/M ratio of 1. During operation, biogas amount and methane percentage were measured. Before and after reactor operation, total solids (TS), volatile solids (VS), chemical oxygen demand (COD) and pH were measured as performance indicators of digestion. Methane production potential was highest in reactors containing only municipal sludge and lowest containing only industrial sludge. The specific methane production normalized with COD removed for OID I, OID II and textile sludges were 0.13 L/g, 0.11 L/g and 0.11 L/g, respectively; whereas average specific methane production for municipal sludge was 0.31 L/g. COD, TS and VS reductions were lower in industrial sludges compared to domestic sludge. The co-digestion reactors with mixed industrial and municipal sludge performed in accordance with the proportion of two sludges. Ultrasonication improved the digestion performance. Although adding industrial sludge reduced the observed biogas amount to lower than that expected, results show that it is possible to co-digest some industrial sludges with municipal sludge in closely coordinated additions (about

Anaerobic co-digestion (AcoD) is a solution to recover renewable energy, such as methane, from food waste (FW) and garden waste (GW). Methane yield efficiency can be improved through the optimization of the operating conditions, such as mixing ratio of substrates (MRS) and Mixing Ratio of Inocula (MRI). The objective was to optimize the AcoD of FW with GW by combining Artificial Neural Networks (ANN) and Particle Swarm Algorithm (PSO). The AcoD of FW and GW were initially evaluated experimentally at a laboratory scale through a central design composed of two factors, at three levels each: FW:GW MRS at 80:20, 70:30 and 60:40 (w/w) and MRI with sludge mixture Granular (GSL) and Flocculant sludge (FSL) equal to 10:90, 30:70 and 50:50 (GSL:FSL, v/v). The response variables were the biochemical methane potential (BMP), bicarbonate alkalinity (BA), volatile fatty acids (VFA), hydrolysis (kh) and process stability index (If). The optimization identified the best operational conditions, which were later validated with a second experiment. Results of ANN and PSO showed that the maximized methane yield (270 mL CH4/g VS) can occur at the ratios of MRS 64:36 (w/w) and at MRI 44:56 (v/v) that increase the methane yield by 26% compared to mono-digestion of FW (70 mL CH4/g VS), while BA of 1645 mg L−1, 1955 mg L−1 of VFA, kh of 0.32d−1 and a stability (If) of −59 are achieved. The second experiment showed the robustness and applicability of the optimization tools, which resulted in a production of 265 mL CH4/g VS as a maximum yield.

The present work demonstrates the co-digestion of Used Disposable Nappies (DN) hydrolysate and Expired Food Products (EFP) at 60/40 (v/v) ratio in a two-stage pilot-scale mesophilic (37 °C) anaerobic system, in comparison with previously published data obtained from lab-scale experiments. The aim of the study was to validate the scale-up simulation of the lab experimentation and to evaluate the efficiency of the pilot-scale system. The operational conditions (acidogenic reactor: constant pH 5.5, HRT 2 d, and methanogenic reactor: HRT 20 d) were selected with respect to lab-scale results. The pilot-system succeeded a 75% COD removal, 0.63 ± 0.06 LCH4/LReactor.d and 0.37 ± 0.09 LH2/LReactor.d. The daily obtained gaseous biofuels’ yields correspond to 45.7 MJ of energy, which is 2.85 times higher than the energy needed for the operation of the equipment. It is estimated that the pilot-stage system converted 73% of the chemical energy of the feed materials to gaseous biofuels. Negligible differences between the two scales of the system were recorded, and the results are promising for the development of a full-scale process that would valorize these specific waste streams.

Anaerobic digestion process is gaining attention in the agriculture industry because of its potential for renewable energy production and manure stabilization. These potential benefits are significant against the current backdrop of rising energy costs and growing environmental concerns. Anaerobic digestion is a naturally occurring process through which organic matter such as manure, feed spills, meat processing wastes and crop residues are stabilized by microorganisms strictly in the absence of air. In developing countries, the inadequate management of waste particularly in urban areas where the consumption pattern have changed and the generation rate increased substantially from one location to another and from time to time. This study explored the production of biogas from kitchen wastes mixed with intestinal cow dung in a semi continuous anaerobic digester. Materials used as feed were Paw Paw, tomato, banana peels and intestinal cow dung. Various parameters were determined using standard methods; water displacement method was used to determine the volume of gas produced. The combustibility of the gas generated was tested using Bunsen burner. Microbiological methods were employed for the microbiological analysis. The temperature and pH recorded in the digester range from 27-33oC and 0-6.81c respectively. It was observed that the waste slurry produced biogas without nutrient or chemical addition to the digester. The highest volume of gas (2.8ml) was produced on the 14th day where the temperature (29oC) and pH (6.79) were relatively high. The result of the statistical analysis showed there is significant difference (P

The disposal of large quantities of tobacco stalks and animal manures generated annually is among the serious challenges faced in China, especially the former, as its toxic composition (nicotine) can induce the risk of healthy impairment during tradition treatment process. Anaerobic digestion (AD) may be an efficient technique for tobacco stalks. Nevertheless, the impact of nicotine in tobacco stalks upon AD is still unclear so far. Thus, a simulated AD experiment using glucose with different nicotine concentrations was implemented, suggesting a nicotine concentration of more than 4% (w/w) could inhibit AD. The nicotine component in tobacco stalks would not be an inhibitor on AD because its content was far below 4%. Meanwhile, in order to efficiently treat abundant tobacco stalks and manure wastes at the same time, untreated and alkaline hydrogen peroxide (AHP)-pretreated tobacco stalks were co-digested with three typical manures, including pig manure (PM), chicken manure (CM), and dairy manure (DM), to investigate their digestion performance. Co-digestion of pretreated tobacco stalks and PM at 1:4 ratio exhibited the highest methane production of 397.2 mL/g VS and had a synergistic effect. This study provides valuable guidance for simultaneously converting these two wastes in future AD applications.

Anaerobic co-digestion of oil palm empty fruit bunches with cow manure was studied. The research focus was on the evaluation of feeding different solid concentrations of the substrate in the on-going process of anaerobic digestion. The solid concentrations ranged from 0.5 to 12% TS. Results of the study showed that the maximum methane production could be reached with the reactor digesting substrates with 4 to 8% TS, in which the methane produced was from 1300 to 1400 mL per day. A significant drop of pH from 7.02 to 5.97 occurred when the reactor was digesting substrates with 10 and 12% TS. Acidic condition caused by organic matter overloads lowered the efficiency of organic conversion represented in the low removal of COD, which was only 22.4%. This finding is highly significant for the waste management industries in terms of dealing with the digester upset due to the digestion of large amount of organic wastes.

This study aims to evaluate the effects of the co‐digestion of agricultural residues with manure from camelids from the Andean zone. Different combinations of llama manure (LM) and vicuñas (VM) were made with amaranth (AS), quinoa (QS), and wheat (WS) residues. They were fermented using sewage sludge as inoculum. The co‐digestion was evaluated under mesophilic conditions for 40 days. The ratios of volatile substances of substrate / co‐substrate evaluated were 0:100; 25:75; 50:50, 75:25, and 100:0. Two substrate / inoculum ratios (SIR 1:1 and SIR1:2) were also evaluated. The results indicate that the maximum methane accumulation rate is obtained in SIR 1:1 for a VM‐AS ratio (25:75) with 540 mL/g volatile solid (VS). In general, the results did not increase with the increase in inoculum; rather, the tendency to improve methane yield is associated with an increase in the amount of agricultural residues, mainly AS. Regarding the kinetic modeling, the transfer model is the one that best adjusted the predicted values to those observed with an r2 between 0.991 and 0.999, and an RMSE value between 2.06 and 13.62 mL/g (volatile solid) VS. Finally, all the trials presented synergistic effects in their co‐digestion except the digesters formed by LM‐AS, LM‐QS and LM‐WS of SIR 1:2. These presented antagonistic effects in which the addition of the co‐substrate generated competition with the substrates, reducing methane production. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

A search for alternatives economically viable and environmentally sound to the world energy demand, stimulated the research in the field of anaerobic digestion, as a form of renewable energy and the anaerobic co-digestion is an alternative to use different types of residues, including food wastes. Therefore, this article presents an analysis of the scientific advances realized of the period of 2015 to 2018 in terms of anaerobic co-digestion, with emphasis on the use of different food residues, especially fruit and vegetable wastes, a different configuration of reactors, and kind of operational conditions used. A description of environmental factors affecting the process efficiency and the biogas generation based on substrate characteristics is presented in this review since these factors play an important role in the biogas yield and determine the metabolic conditions of the microorganism growth. Therefore, research should focus on the anaerobic digestion process balance, to identify optimal operating conditions through the use and valorization of wastes. info:eu-repo/semantics/publishedVersion

O interesse pela producao de biogas tem se intensificado principalmente pelo aumento da energia, alem da preocupacao importante com as questoes ambientais. Propos-se neste trabalho avaliar a potencialidade da co-digestao anaerobia de manipueira, casca de cafe e esterco bovino para a producao de biogas, um fim de otimizar as condicoes de operacao do biodigestor, em um tempo de retencao hidraulica de 15 dias. Foram conduzidas tres etapas experimentais aplicando o delineamento composto central rotacional (DCCR) para avaliar o efeito das variaveis e da interacao entre elas (niveis de carga orgânica volumetrica, temperatura, pH, adicao / concentracao celular de bacterias celuloliticas e adicao de micronutrientes) sobre o processo de metanizacao. Os resultados demonstraram que as condicoes ideais para metanizacao foram definidas como: 40mL de manipueira; 95mL de casca de cafe; 40mL de esterco bovino; pH 6; adicao de 1,5.106UFC.mL-1 de inoculo bacteriano, temperatura de 30 ° C; adicao de 46,97 e 4,41mg.L-1 de FeSO4.7H2O e MnSO4.H2O, respectivamente.

Anaerobic digestion of food waste alone is not very stable due to its acidic nature and high biodegradability. Co-digestion of food waste with alkaline substrate such as chicken manure and goat manure could enhance process stability and biogas yield. In this study comparison of mono digestion of food waste with 8% total solid content at an ambient temperature and co-digestion of food waste, goat and chicken manure at ratio 5:2:3 and 2:1:1 with 8% total solid content at an ambient temperature in hilly region of Nepal were carried out. Biogas yield was highest with mixing ratio of 5:2:3 with the values of 109 ml/gVS followed by mixing ratio of 2:1:1 with the values of 80 ml/gVS. Mono digestion of food waste was not stable and broke down after two weeks of operation. Findings from this study suggests that co-digestion could be a suitable method for addressing the problem related to stability in a single substrate digestion in an ambient temperature condition. Moreover, mixing ratio of co-digestion substrates is important for improved biogas production. Co-digestion of food waste with goat and chicken manure could be a practical approach for sustainable clean energy production and waste management in context of Nepal.

Biogas production can be greatly affected by inoculum addition and total solids. The effect of the substrate to inoculum ratios and total solids of chicken, goat and cow manure on biogas production was studied using a 0.15m3 laboratory-scale batch digester at a constant temperature of 35°C. Feedstocks were mechanically minced to 3 mm effective particle sizes prior to co-digesting with untreated cow manure from a free-range dairy rearing system. Different amounts of cow substrate inoculum were used at ratios of 2:1, 3:1, 4:1, 5:1 and 6:1, while total solid levels between (7.5% and 10.5%) at intervals of 0.5% were used to study their effects on biogas production. Increasing inoculums and total solids resulted in increased biogas production with peaks at a substrate to inoculum ratio of 4:1 (20% inoculum addition) and 9% total solids. Biogas production rates of 0.61 and 0.63m3/m3d were realized respectively. Keywords: Biogas Production, Chicken-Goat-Cow Manure, Substrate to Inoculum Ratios, Total Solids

This study uses a new approach for the recycling of plant nutrients by co-digesting sewage sludgewith fly ash from a wood combustion. Sewage sludge and fly ash both are enriched with nutrientsof the wastewater resp. wood, which makes these products an enhanced source for recycledfertilizers. The effects of the ash addition to the anaerobic digestion are studied in several labscale experiments including effects on the gas production and microbial activity. Following that,the fertilizing qualities of the digestate are evaluated by plant growth experiments. The resultsshow that the fertilizing qualities of the digested sludge were improved by the ash addition.Next to this, gas production results show that the methane production was not affected by theash addition, while the total gas release was reduced. The sulphur addition by the ashstimulated sulphate reducing bacteria. The sulphate reducing bacteria did not markedly inhibitthe methanogens. Validerad;2022;Nivå 2;2022-05-06 (hanlid)

In India, many biogas plants process cattle dung (CD). At the same time, an excessive amount of litter of leaves is swept and burnt. The paper investigates small-scale integration of leaf litter of neem (LLN) to the operational CD-based biogas plant under mesophilic conditions. The introduction of LLN at the volatile solid ratio of 1:4 (LLN:CD) respectively increased daily biogas production, specific methane yield, and the resultant electrical energy by 13.11, 15.26, and 15.02% and reduced the proportion of CO2 by 5.85%. However, because of the energy required to pulverize the LLN in CD-LLN–based, the net percentage increase of the electrical energy dropped to 13.59%. CD-LLN–based reactor also produced 56.34% higher electrical energy per organic substrate added and performed well by 15.0% in terms of CO2 emission compared to CD-based. Digester performance was seriously unaffected during the transition stage. The study highlights another way of managing LLN and shifting anaerobic reactors from one feedstock to another.

The present study evaluates the influence of kitchen wastes on animal manures via anaerobic digestion for biogas production. The digestion was done using a digester with a capacity of 5L. The digester was loaded with the slurry of wastes prepared by mixing the wastes with water in ratio 1:1, and operated at mesophilic temperature of 37 ± 2°C for 30 days. The co-digestion of kitchen wastes with poultry droppings produced highest biogas yield (814.0 ml/kg VS fed) and the least (365.84 ml/kg VS fed) was from the co-digestion of kitchen wastes with the mixture of poultry droppings and cow dung. Composition analysis of the biogas showed the highest methane content (63.1%) from kitchen wastes and the lowest (56.2%) from co-digestion of kitchen wastes with poultry droppings. The pH range for optimum biogas production varied between 5.25 and 7.5. The study concluded that biogas yield from co-digestion of substrates, among other factors depends on the composition of participating substrates.

Due to the rising concerns regarding food waste disposal as well as the increasing demand for renewable energy nowadays, a number of European countries have adopted anaerobic co-digestion, a technology that deals with food waste and sewage sludge. As stated in the HKSAR Government’s Policy Address 2016, the feasibility of using existing sewage treatment facilities for co-digestion of food waste and sewage sludge has been under exploration. A trial scheme has been commenced in 2019. This paper aims to compare the efficiency of biogas production and volatile solid reduction in co-digestion of food waste and sewage with mono-digestion in laboratory scale.

Modelling and optimisation of biogas production from different substrate mixtures is lagging behind in research and development. Current biogas production processes are not fully exploiting co-dige...

The pretreatment effects and synergistic effects of anaerobic co-digestion of pretreated corn stover (CS) with chicken manure (CM) were studied. Results showed that the NaOH-H2O2 pretreatment effect on CS was better than urea pretreatment in terms of anaerobic digestion promotion. The highest cumulative methane yield of 332.7 mL/g VS added was obtained from the CS (NaOH-H2O2 pretreated)/CM ratio of 1:3, and the highest cumulative methane yield of 319.7 mL/g VS added was obtained from the CS (urea pretreated)/CM ratio of 1:2. Synergistic effects were found in CS (NaOH-H2O2 pretreated)/CM ratios of 2:1, 1:2, 1:3 and CS (urea pretreated)/CM ratios of 1:1, 1:2. Synergistic effect was not found at CS (unpretreated)/CM ratios of 1:2 and 1:3. Pretreatment of CS can produce synergistic effect on anaerobic co-digestion and increase cumulative methane yield by 6.54–24.65%. Among the four kinetic models, modified Gompertz model was best fitted in describing the methane production during anaerobic co-digestion (R2 = 0.9845–0.9988).