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Anaerobic digestion (AD) is an essential technology for wastewater management, resource recovery and biogas production, and it is considered as an efficient and reliable treatment method for many wastewaters. Operating parameters have been shown to directly affect the stability and treatment performance of AD, especially temperature. For 180 days, the AD of recycled paper mill wastewater (RPMW) was carried out in a modified anaerobic inclining-baffled (MAIB) reactor under various temperature conditions, i.e. 29 °C (low mesophilic), 37 °C (mesophilic) and 55 °C (thermophilic). It was found that total COD removal of 94, 96 and 76%, and methane yields of 0.125, 0.196 and 0.256 L CH4/g CODremoved were attained at temperatures of 29, 37 and 55 °C, respectively. Throughout the three transition periods, the pH level in the MAIB reactor fluctuated slightly within the range of 5.8–6.5 without affecting the system stability. The results concluded that thermophilic condition strongly influenced the MAIB reactor performance, leading to lower COD removal, higher methane yield and gradually recovered pH level. Highlights Novel modified anaerobic inclining-baffled (MAIB) reactor, which combines the development of attached and settled microorganisms, was operated for the treatment of recycled paper mill wastewater (RPMW).; The operational temperature intensive analysis of MAIB was investigated at thermophilic and mesophilic conditions.; The system compartmental characteristics were also analyzed and discussed.

Distinct microbial assemblages evolve in anaerobic digestion (AD) reactors to drive sequential conversions of organics to methane. The spatio-temporal development of three such assemblages (granules, biofilms, planktonic) derived from the same inoculum was studied in replicated bioreactors treating long-chain fatty acids (LCFA)-rich wastewater at 20 °C at hydraulic retention times (HRTs) of 12–72 h. We found granular, biofilm and planktonic assemblages differentiated by diversity, structure, and assembly mechanisms; demonstrating a spatial compartmentalisation of the microbiomes from the initial community reservoir. Our analysis linked abundant Methanosaeta and Syntrophaceae-affiliated taxa (Syntrophus and uncultured) to their putative, active roles in syntrophic LCFA bioconversion. LCFA loading rates (stearate, palmitate), and HRT, were significant drivers shaping microbial community dynamics and assembly. This study of the archaea and syntrophic bacteria actively valorising LCFAs at short HRTs and 20 °C will help uncover the microbiology underpinning anaerobic bioconversions of fats, oil and grease.

The production of biogas from food waste is a good approach to the minimization of food waste and increase in the production of renewable energy. However, the use of food waste as a feedstock for biogas production currently poses a difficulty due to an ineffective hydrolysis process, which is a pretreatment procedure and the initial step of the biogas conversion process. This restriction results from the food waste polymers’ solubilization and breakdown. This has an impact on the volume of biogas produced during the methanogenesis stage. It is essential to increase the biodegradation of organic compounds (OC) during the hydrolysis process to increase biogas generation. This study focuses on the enhancement of biogas production by the anaerobic digestion (AD) of food waste (FW). FW was hydrolyzed by the immobilized biofilm and digested anaerobically in a semi-continuous digester. Four different digesters including the control were prepared. The control digester composed of no hydrolyzed food waste had no immobilized biofilm while the other three digesters had immobilized biofilm-hydrolyzed food waste with inoculum concentrations of 10%, 30%, and 50%. The results showed that the 50% digester had the highest biogas yield of about 2000 mL/500 mL. The 10%, 30%, and control digesters had a biogas yield of 1523 mL, 753 mL, and 502 mL respectively. Thus, the analysis of total volatile solid (TVS) reduction in the digesters with 10%, 30%, and 50% inoculum and the control have increased to 43.4% for the digesters with 30% and 10%, 60% for the digester with 50% inoculum, and only 29% for the control. Total chemical demand (TCOD) removal increased to 29%, 33%, 43%, and 56% for the control, and 10%, 30%, and 50%, respectively for the inoculum-to-feed ratio. From these results, the 50% inoculum-to-feed ratio has shown the highest biogas production and highest degradation based on TVS reduction and TCOD reduction. Based on this study, the biofilm pretreatment method can be considered a promising method for the enhancement of biogas volume and biodegradation. Biogas production was high (2000 mL) for hydraulic retention time (HRT = 20) days but the HRT = 15 days was also able to produce a significant amount (1400 mL) of biogas and the 50% inoculum-to-feed ratio has shown the highest volume of biogas production.

Greenhouse fruit and vegetable production uses large amounts of energy and other resources, and finding ways of reducing its impact may increase sustainability. Outputs generated from solid-state anaerobic digestion (SS-AD) are suitable for use in greenhouses, which creates a need to investigate the consequences of the possible interactions between them. Connecting the fruit and vegetable production with the resource flows from an SS-AD process, e.g., biogas and digestate, could increase circularity while decreasing the total environmental impact. There are currently no studies where a comprehensive assessment of the material flows between greenhouses and SS-AD are analyzed in combination with evaluation of the environmental impact. In this study, material flow analysis is used to evaluate the effects of adding tomato related waste to the SS-AD, while also using life cycle assessment to study the environmental impact of the system, including production of tomatoes in a greenhouse and the interactions with the SS-AD. The results show that the environmental impact decreases for all evaluated impact categories as compared to a reference greenhouse that used inputs and outputs usually applied in a Swedish context. Using the tomato related waste as a feedstock for SS-AD caused a decrease of biomethane and an increase of carbon dioxide and digestate per ton of treated waste, compared to the digestion of mainly food waste. In conclusion, interactions between a greenhouse and an SS-AD plant can lead to better environmental performance by replacing some of the fertilizer and energy required by the greenhouse.

Sewage sludge is successfully used in anaerobic digestion (AD). Although AD is a well-known, universal and widely recognized technology, there are factors that limit its widespread use, such as the presence of substances that are resistant to biodegradation, inhibit the fermentation process or are toxic to anaerobic microorganisms. Sewage sludge generated by the pharmaceutical sector is one such substance. Pharmaceutical sewage sludge (PSS) is characterized by high concentrations of biocides, including antibiotics and other compounds that have a negative effect on the anaerobic environment. The aim of the present research was to determine the feasibility of applying Advanced Oxidation Processes (AOP) harnessing Fenton’s (Fe2+/H2O2) and Fenton-like (Fe3+/H2O2) reaction to PSS pre-treatment prior to AD. The method was analyzed in terms of its impact on limiting PSS toxicity and improving methane fermentation. The use of AOP led to a significant reduction of PSS toxicity from 53.3 ± 5.1% to 35.7 ± 3.2%, which had a direct impact on the taxonomic structure of anaerobic bacteria, and thus influenced biogas production efficiency and methane content. Correlations were found between PSS toxicity and the presence of Archaea and biogas yields in the Fe2+/H2O2 group. CH4 production ranged from 363.2 ± 11.9 cm3 CH4/g VS in the control PSS to approximately 450 cm3/g VS. This was 445.7 ± 21.6 cm3 CH4/g VS (1.5 g Fe2+/dm3 and 6.0 g H2O2/dm3) and 453.6 ± 22.4 cm3 CH4/g VS (2.0 g Fe2+/dm3 and 8.0 g H2O2/dm3). The differences between these variants were not statistically significant. Therefore, due to the economical use of chemical reagents, the optimal tested dose was 1.5 g Fe2+/6.0 g H2O2. The use of a Fenton-like reagent (Fe3+/H2O2) resulted in lower AD efficiency (max. 393.7 ± 12.1 cm3 CH4/g VS), and no strong linear relationships between the analyzed variables were found. It is, therefore, a more difficult method to estimate the final effects. Research has proven that AOP can be used to improve the efficiency of AD of PSS.

Forty percent of the food generated in Canada is wasted, making it the most significant component of municipal solid waste. Food waste characteristics, such as high moisture and oil content, and variable composition, make it difficult to manage with conventional waste treatment methods. Part of food waste is disposed of in landfills, generating greenhouse gases and significantly increasing the carbon footprint. Various treatment methods such as composting and anaerobic digestion have been employed to treat and manage the remaining waste efficiently. This study provides an overview of the impact of composting as a food waste treatment method in Canada and paves way for the research of the usefulness of composting in addition to other food waste treatment methods such as anaerobic digestion. Average composting data for Canada was used to determine the change in the carbon footprint by the diversion of food waste using CCaLC2 software. It was determined that the overall carbon footprint of 1.38 and 1.33 mega-tons of CO2 was reduced from the composting of food waste in the years 2014 and 2016, which were approximately 18% and 20% of the total footprint of Canada municipal solid waste, respectively. The carbon footprint data collected herein were compared to the data from England, Sweden, and the USA to reveal the high effectiveness of composting in Canada.

Perfluorooctanoic acid (PFOA) that accumulates in wastewater and excess sludge interact with the anaerobes and deteriorate the energy recovery and pollutants removal performance in the anaerobic digestion (AD) system. However, the interaction between PFOA and microbial metabolism in the AD systems remains unclear. This study aimed to clarify the effects and mechanism of PFOA on the AD process as well as the removal pathways of PFOA in an AD system. The results showed that the methane recovery efficiency was inhibited by 7.6–19.7% with the increased PFOA concentration of 0.5–3.0 mg/L, and the specific methanogenesis activity (SMA) was inhibited by 8.6–22.3%. The electron transfer system (ETS) was inhibited by 22.1–37.3% in the PFOA-containing groups. However, extracellular polymeric substance (EPS) gradually increased due to the toxicity of PFOA, and the ratio of protein to polysaccharide shows an upward trend, which led to the formation of sludge aggregates and resistance to the toxic of PFOA. The PFOA mass balance analysis indicated that 64.2–71.6% of PFOA was removed in the AD system, and sludge adsorption was the main removal pathway, accounting for 36.1–61.2% of the removed PFOA. In addition, the anaerobes are proposed to have the potential to reduce PFOA through biochemical degradation since 10.4–28.2% of PFOA was missing in the AD system. This study provides a significant reference for the treatment of high-strength PFOA-containing wastes.

Limited reserves of fossil fuel resources and negative environmental impacts increased energy demands toward renewable energy technologies. Bioenergy is one of the solutions, and biogas production from wastes and residues by anaerobic digestion (AD) is a promising technology. Municipal solid wastes, sludge from wastewater treatment plants, agricultural plant wastes, forestry residues and manure are the widely used sources in AD for biogas production. Aquatic plants can be evaluated as a renewable energy source. If waste and residues of these plants are not utilized in beneficial use, greenhouse gases (GHG) will be emitted through land-filling or direct combustion. Wastes should be converted to biogas with a high yield to decrease the quantity of wastes and biogas with a high-energy content. Substrate to inoculum ratio, temperature regime, C/N ratio, pH, volatile fatty acid and ammonia content are important process parameters for AD. Modified Gompertz, Cone and first-order equations are widely used model equations for kinetic parameters that are used in kinetic models (Monod, modified Andrew, Ratkowsky) for identification of optimum substrate concentration and temperature for each specific feed. This chapter evaluates effective process parameters on AD of aquatic plants for biogas production and application of kinetic analysis for assignment of optimum conditions., Scientific and Technological Research Council ofTurkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [114Y500]; Ministry of Science, Industry and Technology of Turkish Republic [0330.STZ.2013-2], The authors acknowledge the Scientific and Technological Research Council ofTurkey (TUBITAK, Project No: 114Y500) for the financial support. We also thankThe Ministry of Science, Industry and Technology of Turkish Republic supporting our preliminary tests through the grant so-called SAN-TEZ (Project No: 0330.STZ.2013-2). We are grateful to IZSU Ci.gli Advanced BiologicalWastewater Treatment Plant, Izmir for giving us waste sludge for biogas production. We thank to Mr. G. Serin, M.Sc. students M. C. Akbas and B. Kaletas for assistance in laboratory studies. the authors acknowledge publisher "John Wiley and Sons" for permission of reuse of full article Gungoren Madeno.glu et al. [7].

The main aim of this study was to evaluate the biomethane potential (BMP) of fruit waste by incorporating additives such as sewage sludge biochar at different inoculum-to-substrate ratios (ISRs) of 2, 1.5, and 1 (wt./wt.). The results showed an improvement in the maximum methane production by 13, 20, and 27% upon the addition of sewage sludge biochar produced at 350°C for ISR of 2, 1.5, and 1 (wt./wt.), respectively, and an increase 12, 18, and 22% for the added biochar produced at 550°C for ISR of 2, 1.5, and 1 (wt./wt.), respectively, compared to the BMP tests performed without the addition of biochar (i.e., the control). Biochar addition reduced volatile fatty acid (VFA) formation during the digestion of fruit waste as compared to the control reactor, which is a strong indication that the metabolic process of the system was streamlined to methanogenesis. The maximum methane yield for the tested fruit substrates was 285.7 mL CH4/g in the presence of biochar prepared at a low temperature (350°C). This value is higher than one obtained with same amount of biochar prepared at a higher temperature (550°C). The results from this study showed that the effectiveness of the anaerobic digestion process depends on the ISR, biochar dose, and the pyrolysis temperature used for the production of the sewage sludge digestate biochar.

Hydrothermal carbonisation (HTC) can be integrated with anaerobic digestion (AD) for the treatment of digestate, resulting in a solid hydrochar or bio-coal and a process water, which can be recirculated back into AD to produce biogas. The properties of digestate-derived hydrochars do not lend themselves to producing high quality bio-coal and blending with lignocellulosic feedstocks can improve its properties. This study investigates the co-processing of sewage sludge (SS) digestate with three lignocellulosic biomass (grass, privet hedge, and woodchip). The calorific value of the resulting bio-coal is increased following co-processing, although feedstock interactions result in non-additive behaviour. The largest increase in calorific value was observed for co-processing with woodchip. There is evidence for non-additive partitioning of metals during co-processing resulting in only moderate improvements in ash chemistry during combustion. Co-processing also effects the composition of process waters, influencing the potential for biogas production. Experimental biomethane potential (BMP) tests indicate that grass clippings are the most suitable co-feedstock for maintaining both calorific value and biogas production. However, above 200 °C, BMP yields appear to decrease, suggesting the process water may become more inhibitory. Co-processing with wood waste and privet hedge produce the higher CV bio-coal but significantly reduced BMP.

Anaerobic digestion (AD) serves as a potential bioconversion process to treat various organic wastes/wastewaters, including sewage sludge, and generate renewable green energy. Despite its efficiency, AD has several limitations that need to be overcome to achieve maximum energy recovery from organic materials while regulating inhibitory substances. Hence, bioelectrochemical systems (BESs) have been widely investigated to treat inhibitory compounds including ammonia in AD processes and improve the AD operational efficiency, stability, and economic viability with various integrations. The BES operations as a pretreatment process, inside AD or after the AD process aids in the upgradation of biogas (CO2 to methane) and residual volatile fatty acids (VFAs) to valuable chemicals and fuels (alcohols) and even directly to electricity generation. This review presents a comprehensive summary of BES technologies and operations for overcoming the limitations of AD in lab-scale applications and suggests upscaling and future opportunities for BES-AD systems.

[EN] This research work proposes an innovative water resource recovery facility (WRRF) for the recovery of energy, nutrients and reclaimed water from sewage, which represents a promising approach towards enhanced circular economy scenarios. To this aim, anaerobic technology, microalgae cultivation, and membrane technology were combined in a dedicated platform. The proposed platform produces a high-quality solid- and coliform-free effluent that can be directly discharged to receiving water bodies identified as sensitive areas. Specifically, the content of organic matter, nitrogen and phosphorus in the effluent was 45 mg COD.L-1 , 14.9 mg N.L-1 and 0.5 mg P.L-1 , respectively. Harvested solar energy and carbon dioxide biofixation in the form of microalgae biomass allowed remarkable methane yields (399 STP L CH 4.kg(-1) CODinf ) to be achieved, equivalent to theoretical electricity productions of around 0.52 kWh per m 3 of wastewater entering the WRRF. Furthermore, 26.6% of total nitrogen influent load was recovered as ammonium sulphate, while nitrogen and phosphorus were recovered in the biosolids produced (650 +/- 77 mg N.L-1 and 121.0 +/- 7.2 mg P.L-1)., This research was supported by the Spanish Ministry of Economy and Competitiveness (MINECO, Projects CTM2014-54980-C2-1-R and CTM2014-54980-C2-2-R) jointly with the European Regional Development Fund (ERDF), which are gratefully acknowledged. This research was also supported by the Spanish Ministry of Education, Culture and Sport via two pre-doctoral FPU fellowships (FPU14/05082 and FPU15/02595) and by the Spanish Ministry of Economy and Competitiveness via two pre-doctoral FPI fellowships (BES-2015-071884, BES-2015-073403) and one Juan de la Cierva contract (FJCI-2014-21616). The authors would also like to acknowledge the support received from Generalitat Valenciana via two VALithornd post-doctoral grants (APOSTD/2014/049 and APOSTD/2016/104) and via the fellowships APOTI/2016/059 and CPI-16-155, as well as the financial aid received from the European Climate KIC association for the 'MAB 2.0' Project (APIN0057_ 2015-3.6-230_ P066-05) and Universitat Politecnica de Valencia via a pre-doctoral FPI fellowship to the seventh author.

Nowadays, organic waste and especially household waste represents a significant global issue due to population growth. The anaerobic digestion (AD) process is an essential operation contributing powerfully to the valorization of organic waste including food waste in terms of renewable energy generation (biogas) and the rich-nutrient residue that can be utilized as bio-fertilizer. Thus, this process (AD) allows for good recovery of household waste by generating biogas and compost. However, the AD operation has been affected by several key factors. In this paper, we aim to involve different critical parameters influencing the AD process, including temperature, pH, organic loading rate (OLR), carbon to nitrogen ratio (C/N), and total solid content (TS(%)). Further, the paper highlights the inhibition caused by the excessive accumulation of volatile fatty acids (VFAs) and ammoniac, which exhibits the positive effects of co-digestion, pretreatment methods, and mixing techniques for maintaining process stability and enhancing biogas production. We analyze some current mathematical models explored in the literature, such as distinct generic, non-structural, combined, and kinetic first-order models. Finally, the study discusses challenges, provides some possible solutions, and a future perspective that promises to be a highly useful resource for researchers working in the field of household waste recovery for the generation of biogas.

This paper presents a deterministic approach for sizing a solar photovoltaic (PV) and energy storage system (ESS) with anaerobic digestion (AD) biogas power plant (BPP) to meet a proportional scaled-down demand of the national load in Kenya, Africa. The aim is to achieve a minimal levelized cost of energy (LCOE) for the system while minimizing the energy imbalance between generation and demand due to AD generator constraint and solar resource. This system also aims to maximize the sizing of PV as to follow the future trend of high penetration of PV. LCOE for the system and a levelized cost of delivery (LCOD) are calculated for the hybrid energy system with the presence of energy storage. Four years of solar data collected from Johannesburg, Africa, are used for system sizing purposes. An in-depth study of the optimization problem has been given and particle swarm optimization with the interior point method is chosen for solar panel sizing. The optimal sizing ratio for the generation sources AD and PV is 2.4:5. The results show that the hybrid system will be cost effective compared to the AD-only system when the discount rate drops below 8% with the current technology costs.

The effect of biochar addition on the anaerobic digestion (AD) of food waste was evaluated. From the five biochars tested, Fe, Co, Ni, and Mn were leached in very small quantities (

Rice straw is an abundant and sustainable substrate for anaerobic digestion (AD), but it is often deficient in essential trace elements (TEs) for proper microbial growth and metabolism. A lack of TEs leads to AD imbalances and suboptimal biogas yields. However, the total TE concentration is not a sufficient indicator of the amount of TEs available to the microorganisms. Therefore, this study investigated the degree of bioavailability of iron (Fe) and cobalt (Co) during the AD of rice straw, and correlated it to the biomethane yields and volatile fatty acids (VFAs) produced. When the two TEs were dosed at 205 µg Fe/g TS and 18 µg Co/g TS of rice straw, the biomethane production was approximately 260 mL CH4/g VS, i.e., similar to that obtained when Fe and Co were not added. Despite an increased bioavailable fraction of 23 and 48% for Fe and Co, respectively, after TEs addition, the AD performance was not enhanced. Moreover, VFAs did not exceed 250 mg HAc/L both in the presence and absence of added TEs, confirming no enhancement of the methanogenesis step. Therefore, the bioavailability of Fe and Co was not a limiting factor for the biomethane production at low total VFAs concentration.

Biochemical energy recovery using digestion and co-digestion of faecal matter collected from urine diverting dehydrating toilet faeces (UDDT-F) and mixed organic market waste (OMW) was studied under laboratory- and pilot-scale conditions. Laboratory-scale biochemical methane potential (BMP) tests showed an increase in methane production with an increase in OMW fraction in the feed substrate. In subsequent pilot-scale experiments, one-stage and two-stage plug flow digester were researched, applying UDDT-F:OMW ratios of 4:1 and 1:0, at about 10 and 12% total solids (TS) slurry concentrations. Comparable methane production was observed in one-stage (Ro-4:1,12%) (314 ± 15 mL CH4/g VS added) and two-stage (Ram-4:1,12%) (325 ± 12 mL CH4/g VS added) digesters, when applying 12% TS slurry concentration. However, biogas production in Ram-4:1,12% digester (571 ± 25 mL CH4/g VS added) was about 12% higher than in Ro-4:1,12%, significantly more than the slight difference in methane production, i.e. 3–4%. The former was attributed to enhanced waste solubilisation and increased CO2 dissolution, resulting from mixing the bicarbonate-rich methanogenic effluent for neutralisation purposes with the low pH (4.9) influent acquired from the pre-acidification stage. Moreover, higher process stability was observed in the first parts of the plug flow two-stage digester, characterised by lower VFA concentrations.

The effect of biochar addition on the anaerobic digestion (AD) of food waste was evaluated. From the five biochars tested, Fe, Co, Ni, and Mn were leached in very small quantities (

The present study aimed to determine the effect of a 17.6 mT static magnetic field (SMF) on the efficiency of anaerobic digestion (AD) of municipal sewage sludge (MSS). The SMF had a significant impact on methane (CH4) production efficiency, the levels of fermentation rate (ηFMSS) vs. removal rate (ηVS), and the structure of the anaerobic bacteria consortium, but it did not affect cumulative biogas production. The highest CH4 yield (431 ± 22 dm3CH4/kgVS) and the highest methane content in the biogas (66.1% ± 1.9%) were found in the variant in which the SMF exposure time was 144 min/day. This variant also produced the highest ηFMSS and ηVS values, reaching 73.8% ± 2.3% and ηVS 36.9% ± 1.6%, respectively. Longer anaerobic sludge retention time in the SMF area significantly decreased AD efficiency and caused a significant reduction in the number of methanogens in the anaerobic bacteria community. The lowest values were observed for SMF exposure time of 432 min/day, which produced only 54.8 ± 1.9% CH4 in the biogas. A pronounced reduction was recorded in the Archaea (ARC915) and Methanosaeta (MX825) populations in the anaerobic sludge, i.e., to 20% ± 11% and 6% ± 2%, respectively.

One of the greatest challenges facing the societies now and in the future is the reduction of green house gas emissions and thus preventing the climate change. It is therefore important to replace fossil fuels with renewable sources, such as biogas. Biogas can be produced from various organic waste streams or as a byproduct from industrial processes. Beside energy production, the degradation of organic waste through anaerobic digestion offers other advantages, such as the prevention of odor release and the decrease of pathogens. Moreover, the nutrient rich digested residues can be utilized as fertilizer for recycling the nutrients back to the fields. However, the amount of organic materials currently available for biogas production is limited and new substrates as well as new effective technologies are therefore needed to facilitate the growth of the biogas industry all over the world. Hence, major developments have been made during the last decades regarding the utilization of lignocellulosic biomass, the development of high rate systems, and the application of membrane technologies within the anaerobic digestion process in order to overcome the shortcomings encountered. The degradation of organic material requires a synchronized action of different groups of microorganisms with different metabolic capacities. Recent developments in molecular biology techniques have provided the research community with a valuable tool for improved understanding of this complex microbiological system, which in turn could help optimize and control the process in an effective way in the future.

Biochemical reactions occurring during anaerobic digestion have been modelled using reaction kinetic equations such as first-order, Contois and Monod which are then combined to form mechanistic models. This work considers models which include between one and three biochemical reactions to investigate if the choice of the reaction rate equation, complexity of the model structure as well as the inclusion of inhibition plays a key role in the ability of the model to describe the methane production from the semi-continuous anaerobic digestion of green waste (GW) and food waste (FW). A parameter estimation method was used to investigate the most important phenomena influencing the biogas production process. Experimental data were used to numerically estimate the model parameters and the quality of fit was quantified. Results obtained reveal that the model structure (i.e. number of reactions, inhibition) has a much stronger influence on the quality of fit compared with the choice of kinetic rate equations. In the case of GW there was only a marginal improvement when moving from a one to two reaction model, and none with inclusion of inhibition or three reactions. However, the behaviour of FW digestion was more complex and required either a two or three reaction model with inhibition functions for both ammonia and volatile fatty acids. Parameter values for the best fitting models are given for use by other authors.

DOI: 10.1016/j.proeng.2016.06.397 This paper presents a case study to investigate the potential for upgrade of a bio-waste treatment plant. The paper also discusses development potentials in order to optimize the plant for maximum energy and environmental benefits. Data gathered over two consecutive years about the production of biogas, energy and bio-rest were considered and mass balance analysis of inputs and outputs of the plant were carried out. An estimate of the energy and environmental impact of the plant were carried out, and it was observed that the plant had significant environmental benefits. However, the study demonstrates, through material balance analysis of the plant’s operation, that the amount of produced methane and hence, generated electricity can be further increased by optimising the operation of the plant.

Anaerobic digestion of kitchen waste faces the challenge of frequent composition variation and rapid digester acidification due to its highly degradable nature. Considering this challenge, one year long pilot scale anaerobic digestion study was conducted in the anaerobic digester of 25 ​m3/day capacity with seasonal kitchen waste (fruits and vegetable waste). The seasonal variation in kitchen waste content was studied by dividing a year into six seasons (each season comprising 60 days), namely, spring, summer, monsoon, autumn, early winter, and prevernal winter. Considering all the properties of kitchen waste, the anaerobic digestion experiment was conducted with the organic loading rate (OLR) of 0.60–0.72 ​kg VS/m3/day. The specific biogas production for all the seasons was found to be 0.56–0.68 ​m3/kg VS, with the volumetric methane content of 54.3–62.8%. The average seasonal specific methane production was observed in the range of 0.30–0.41 ​m3/kg VS. The anaerobic digestion conversion efficiency of 55.3–67.0% was found for the anaerobic digestion of the wastes. The problem of the rapid acidification of kitchen waste has been rectified with the addition of protein-rich de-oiled pongamia cake in place of alkali chemicals. The economic analysis of kitchen waste based anaerobic digestion showed the maximum economic benefits of biogas production as INR 30,783 for its utilization as LPG and INR 37,777 for its utilization as electricity for the summer season compared to all other seasons. The extra economic benefits earned by the utilization of the digested slurry as organic manure, as it contains a good amount of nitrogen (N) 2.3–2.6%, phosphorus (P) 0.6–0.9%, and potassium (K) 0.7–1.1%.

In this study, a simulation was carried out using BioWin 3.1 to test the capability of the software to predict the biogas potential for two different anaerobic systems. The two scenarios included: (1) a laboratory-scale batch reactor, and (2) an industrial-scale anaerobic continuous lagoon digester. The measured data related to the operating conditions, the reactor design parameters and the chemical properties of influent wastewater were entered into BioWin. A sensitivity analysis was carried out to identify the sensitivity of the most important default parameters in the software’s models. BioWin was then calibrated by matching the predicted data with measured data and used to simulate other parameters that were unmeasured or deemed uncertain. In addition, statistical analyses were carried out using evaluation indices, such as the coefficient of determination (R-squared), the correlation coefficient (r) and its significance (p-value), the general standard deviation (SD) and the Willmott index of agreement, to evaluate the agreement between the software prediction and the measured data. The results have shown that after calibration, BioWin can be used reliably to simulate both small-scale batch reactors and industrial-scale digesters with a mean absolute percentage error (MAPE) of less than 10% and very good values of the indexes. Furthermore, by changing the default parameters in BioWin, which is a way of calibrating the models in the software, as well, this may provide information about the performance of the digester. Furthermore, the results of this study showed there may be an over estimation for biogas generated from industrial-scale digesters. More sophisticated analytical devices may be required for reliable measurements of biogas quality and quantity.

Highlights • Different methanogenic communities in mesophilic and thermophilic reactors. • High VFA levels do not cause major changes in archaeal communities. • Real-time PCR indicated greater diversity than ANAEROCHIP microarray., A study was conducted to determine whether differences in the levels of volatile fatty acids (VFAs) in anaerobic digester plants could result in variations in the indigenous methanogenic communities. Two digesters (one operated under mesophilic conditions, the other under thermophilic conditions) were monitored, and sampled at points where VFA levels were high, as well as when VFA levels were low. Physical and chemical parameters were measured, and the methanogenic diversity was screened using the phylogenetic microarray ANAEROCHIP. In addition, real-time PCR was used to quantify the presence of the different methanogenic genera in the sludge samples. Array results indicated that the archaeal communities in the different reactors were stable, and that changes in the VFA levels of the anaerobic digesters did not greatly alter the dominating methanogenic organisms. In contrast, the two digesters were found to harbour different dominating methanogenic communities, which appeared to remain stable over time. Real-time PCR results were inline with those of microarray analysis indicating only minimal changes in methanogen numbers during periods of high VFAs, however, revealed a greater diversity in methanogens than found with the array.

This paper aims to evaluate the economical and environmental impact of waste incineration, landfill gas recovery system (LFGRS), and anaerobic digestion (AD) for municipal solid waste (MSW) management in Malaysia and subsequently assess the potential of each technology for energy uses and carbon reduction. An existing landfill, Taman Beringin, in Malaysia is selected as the case study, which is one of the largest national sites for waste management. The results present that incineration is the most economical profitable and climate-friendly WTE alternative as compared to an conventional landfill. With the production of 1430 MWh/d of heat and 480 MWh/d of electricity from 1000 t/d of MSW input, waste incineration is able to reach 287% of profit increment or 450 TUSD/d and 2250 tCO2/d of carbon avoidance by fossil fuel replacement as compared to baseline.

Hydrothermal Liquefaction (HTL) for algal biomass conversion is a promising technology capable of producing high yields of biocrude as well as partitioning even higher quantity of nutrients in the aqueous phase. To assess the feasibility of utilizing the aqueous phase, HTL of Nannochloropsis sp. was carried out in the temperature range of 275 to 350 °C and Residence Times (RT) ranging between 5 and 60 min The effect of reaction conditions on the NO 3 − , PO 4 3 − , SO 4 2 − , Cl − , Na + , and K + ions as well as Chemical Oxygen Demand (COD) and pH was investigated with view of recycling the aqueous phase for either cultivation or energy generation via Anaerobic Digestion (AD), quantified via Lifecycle Assessment (LCA). It addition to substantial nutrient partitioning at short RT, an increase in alkalinity to almost pH 10 and decrease in COD at longer RT was observed. The LCA investigation found reaction conditions of 275 °C/30 min and 350 °C/10 min to be most suitable for nutrient and energy recovery but both processing routes offer environmental benefit at all reaction conditions, however recycling for cultivation has marginally better environmental credentials compared to AD.

Heterogeneous substrates fed into agricultural biogas plants originate from many sources with resulting quality fluctuations potentially inhibiting the process. Biogas yield can be substantially increased by optimisation of the organic dry matter load. In this study, near infrared spectroscopy was applied on-line in a re-circulating loop configuration operating identically as a full-scale setup. Ammonium could be modelled in the industrially relevant range 2.42 – 8.52 g L-1 with an excellent accuracy and precision, slope ~1.0, r2 = 0.97, corresponding toa relative Root Mean Square Error of Prediction (RMSEP) of 6.7 %. Also, dry matter in the similar plant relevant range 5.8 – 10.8 weight-percent could be predicted with acceptable accuracy (slope ~1.0, r2 = 0.83, and a relative RMSEP below 8.0 %. Based on these performance characteristics ,it was concluded that near infrared spectroscopy can be applied for optimising the efficiency of current and future biogas plants, as well as in biorefinery contexts converting heterogeneous bioslurry, energy crops, and wastes into value-added products. Adding model transfer capabilities, it is indicated that handheld instrumentation can play a vital role in bringing NIR technology directly in the field, and onto the plant floor – the implications for reliable biogas NIR process monitoring and control are significant.

The versatility of anaerobic digestion (AD) as an effective technology for solving central challenges met in applied biotechnological industry and society has been documented in numerous publications over the past many decades. Reduction of sludge volume generated from wastewater treatment processes, sanitation of industrial organic waste, and benefits from degassing of manure are a few of the most important applications. Especially, renewable energy production, integrated biorefining concepts, and advanced waste handling are delineated as the major market players for AD that likely will expand rapidly in the near future. The complex, biologically mediated AD events are far from being understood in detail however. Despite decade-long serious academic and industrial research efforts, only a few general rules have been formulated with respect to assessing the state of the process from chemical measurements. Conservative reactor designs have dampened the motivation for employing new technologies, which also constitutes one of the main barriers for successful upgrade of the AD sector with modern process monitoring instrumentation. Recent advances in Process Analytical Technologies (PAT) allow complex bioconversion processes to be monitored and deciphered using e.g. spectroscopic and electrochemical measurement principles. In combination with chemometric multivariate data analysis these emerging process monitoring modalities carry the potential to bring AD process monitoring and control to a new level of reliability and effectiveness. It is shown, how proper involvement of process sampling understanding, Theory of Sampling (TOS), constitutes a critical success factor. We survey the more recent trends within the field of AD monitoring and the powerful PAT/TOS/chemometrics application potential is highlighted. The Danish co-digestion concept, which integrates utilisation of agricultural manure, biomass and industrial organic waste, is used as a case study. We present a first foray for the next research and development perspectives and directions for the AD bioconversion sector. The versatility of anaerobic digestion (AD) as an effective technology for solving central challenges met in applied biotechnological industry and society has been documented in numerous publications over the past many decades. Reduction of sludge volume generated from wastewater treatment processes, sanitation of industrial organic waste, and benefits from degassing of manure are a few of the most important applications. Especially, renewable energy production, integrated biorefining concepts, and advanced waste handling are delineated as the major market players for AD that likely will expand rapidly in the near future. The complex, biologically mediated AD events are far from being understood in detail however. Despite decade-long serious academic and industrial research efforts, only a few general rules have been formulated with respect to assessing the state of the process from chemical measurements. Conservative reactor designs have dampened the motivation for employing new technologies, which also constitutes one of the main barriers for successful upgrade of the AD sector with modern process monitoring instrumentation. Recent advances in Process Analytical Technologies (PAT) allow complex bioconversion processes to be monitored and deciphered using e.g. spectroscopic and electrochemical measurement principles. In combination with chemometric multivariate data analysis these emerging process monitoring modalities carry the potential to bring AD process monitoring and control to a new level of reliability and effectiveness. It is shown, how proper involvement of process sampling understanding, Theory of Sampling (TOS), constitutes a critical success factor. We survey the more recent trends within the field of AD monitoring and the powerful PAT/TOS/chemometrics application potential is highlighted. The Danish co-digestion concept, which integrates utilisation of agricultural manure, biomass and industrial organic waste, is used as a case study. We present a first foray for the next research and development perspectives and directions for the AD bioconversion sector.

Background Solid bio-wastes (or organic residues) are worldwide produced in high amount and increasingly considered bioenergy containers rather than waste products. A complete bioprocess from recalcitrant solid wastes to methane (SW2M) via anaerobic digestion (AD) is believed to be a sustainable way to utilize solid bio-wastes. However, the complex and recalcitrance of these organic solids make the hydrolysis process inefficient and thus a rate-limiting step to many AD technologies. Effort has been made to enhance the hydrolysis efficiency, but a comprehensive assessment over a complete flow scheme of SW2M is rare. Results In this study, it comes to reality of a complete scheme for SW2M. A novel process to efficiently convert organic residues into methane is proposed, which proved to be more favorable compared to conventional methods. Brewers’ spent grain (BSG) and pig manure (PM) were used to test the feasibility and efficiency. BSG and PM were enzymatically pre-hydrolyzed and solubilized, after which the hydrolysates were anaerobically digested using different bioreactor designs, including expanded granular sludge bed (EGSB), continuously stirred tank reactor (CSTR), and sequencing batch reactor (SBR). High organic loading rates (OLRs), reaching 19 and 21 kgCOD · m−3 · day−1 were achieved for the EGSBs, fed with BSG and PM, respectively, which were five to seven times higher than those obtained with direct digestion of the raw materials via CSTR or SBR. About 56% and 45% organic proportion of the BSG and PM can be eventually converted to methane. Conclusions This study proves that complex organic solids, such as cellulose, hemicellulose, proteins, and lipids can be efficiently hydrolyzed, yielding easy biodegradable/bio-convertible influents for the subsequent anaerobic digestion step. Although the economical advantage might not be clear, the current approach represents an efficient way for industrial-scale treatment of organic residues with a small footprint and fast conversion of AD.

Background Solid bio-wastes (or organic residues) are worldwide produced in high amount and increasingly considered bioenergy containers rather than waste products. A complete bioprocess from recalcitrant solid wastes to methane (SW2M) via anaerobic digestion (AD) is believed to be a sustainable way to utilize solid bio-wastes. However, the complex and recalcitrance of these organic solids make the hydrolysis process inefficient and thus a rate-limiting step to many AD technologies. Effort has been made to enhance the hydrolysis efficiency, but a comprehensive assessment over a complete flow scheme of SW2M is rare. Results In this study, it comes to reality of a complete scheme for SW2M. A novel process to efficiently convert organic residues into methane is proposed, which proved to be more favorable compared to conventional methods. Brewers’ spent grain (BSG) and pig manure (PM) were used to test the feasibility and efficiency. BSG and PM were enzymatically pre-hydrolyzed and solubilized, after which the hydrolysates were anaerobically digested using different bioreactor designs, including expanded granular sludge bed (EGSB), continuously stirred tank reactor (CSTR), and sequencing batch reactor (SBR). High organic loading rates (OLRs), reaching 19 and 21 kgCOD · m−3 · day−1 were achieved for the EGSBs, fed with BSG and PM, respectively, which were five to seven times higher than those obtained with direct digestion of the raw materials via CSTR or SBR. About 56% and 45% organic proportion of the BSG and PM can be eventually converted to methane. Conclusions This study proves that complex organic solids, such as cellulose, hemicellulose, proteins, and lipids can be efficiently hydrolyzed, yielding easy biodegradable/bio-convertible influents for the subsequent anaerobic digestion step. Although the economical advantage might not be clear, the current approach represents an efficient way for industrial-scale treatment of organic residues with a small footprint and fast conversion of AD.

The present work investigates electricity production using a high efficiency electrochemical generator that employs as fuel a biogas from the dry anaerobic digestion of the organic fraction of municipal solid waste (OFMSW). The as-produced biogas contains several contaminants (sulfur, halogen, organic silicon and aromatic compounds) that can be harmful for the fuel cell: these were monitored via an innovative mass spectrometry technique that enables for in-line and real-time quantification. A cleaning trap with activated carbons for the removal of sulfur and other VOCs contained in the biogas was also tested and monitored by observing the different breakthrough times of studied contaminants. The electrochemical generator was a commercial Ni anode-supported planar Solid Oxide Fuel Cell (SOFC), tested for more than 300 h with a simulated biogas mixture (CH4 60 vol.%, CO2 40 vol.%), directly fed to the anode electrode. Air was added to promote the direct internal conversion of CH4 to H2 and CO via partial oxidation (POx). The initial breakthrough of H2S from the cleaning section was also simulated and tested by adding ∼1 ppm(v) of sulfur in the anode feed; a full recovery of the fuel cell performance after 24 h of sulfur exposure (∼1 ppm(v)) was observed upon its removal, indicating the reliable time of anode exposure to sulfur in case of exhausted guard bed.