This study applied granular activated carbon (GAC) to improve the anaerobic digestion of long-chain fatty acid (LCFA). New kinetics were considered to describe the effect of GAC on the LCFA degradation, including i) The adsorption kinetics of GAC for LCFA, ii) The β-oxidation pathway of LCFA, iii) The attached biomass improved by direct interspecies electron transfer (DIET). The developed model simulated the anaerobic digestion of stearic acid, palmitic acid, myristic acid, and lauric acid with 1.00 and 2.00 g l-1 of GAC. The simulation results suggested that adding GAC led to the increase of km,CnGAC and km,acGAC. As the concentration of GAC increased, the values of kinetic parameters increased while the accumulated acetate concentration decreased. Thus, GAC improved the kinetic parameters of the attached syntrophic communities.

This study investigated biochemical methane potential (B0) of manure residues and solid-liquid separation fractions from Australian dairies. This is important for country-specific sector emissions and biogas potential estimates. A range of samples were collected from 12 farms across 4 Australian states, and B0 was measured. A first B0 value for grazing dairy effluent is reported, at 161 LCH4·kgVS-1. The B0 of manure residues from intensive dairies with total mixed ration feeding was not significantly different, at 202 LCH4·kgVS-1. Passive solid-liquid separation decreased B0 with potential fugitive methane losses. Mechanical separation preserved B0, allowing organic matter diversion to reduce fugitive methane emissions. Cleaning method at a dairy significantly influenced residue total solids content, important for solid-liquid separation and selection of anaerobic digestion technology. Overall, B0 for Australian dairy residues was estimated at 76.2 million m3N methane per annum, with a total energy content of 2.8 petajoules·annum-1.

Biogas is a valuable renewable energy source that can help mitigate greenhouse emissions. The dry reforming of methane (DRM) offers an alternative hydrogen production route with the advantage of using two main greenhouse gases, CO2 and CH4. However, its real application is limited mainly due to catalyst deactivation by coke formation and the reverse water gas shift (RWGS) reaction that can occur in parallel. Additionally, the typical dry reforming temperature range is 700-950 °C, often leading to catalyst sintering. A low-temperature DRM process could be in principle achieved using a membrane reactor (MR) to shift the dry reforming equilibrium forward and inhibit the RWGS reaction. In this work, biogas reforming was investigated through the simulation of MRs with thin (3.4 µm) and thick (50 µm) Pd-Ag membranes. The effects of the feed temperature (from 450 to 550 °C), pressure (in the range of 2-20 bar), and biogas composition (CH4/CO2 molar ratios from 1/1 to 7/3) were studied for the thin membrane through the calculation and comparison of several process indicators, namely CH4 and CO2 conversions, H2 yield, H2/CO ratio and H2 recovery. Estimation of the CO-inhibiting effect on the H2 molar flux through the membrane was assessed for a thick membrane. Simulations for a thin Pd-Ag MR show that (i) CO2 and CH4 conversions and H2 yield increase with the feed temperature; (ii) H2 yield and average rate of coke formation increase for higher pressures; and (iii) increasing CH4/CO2 feed molar ratio leads to higher H2/CO ratios, but lower H2 yields. Moreover, simulations for a thick Pd-Ag MR showed that the average H2 molar flux decreases due to the CO inhibiting effect (ca. 15%) in the temperature range considered. In conclusion, this work showed that for the considered simulation conditions, the use of an MR leads to the inhibition of the RWGS reaction and improves H2 yield, but coke formation and CO inhibition on H2 permeation may pose limitations on its practical feasibility, for which proper strategies must be explored.

Plant herbs specifically serai wangi (SW) and peppermint (PPM) are selected for its insect repellent properties as the use of chicken manure (CM) in anaerobic digestion (AD) potentially attract flies due to the digestate produced. Hence, the addition of SW and PPM in the AD system of CM could deter flies\' infestation while producing biogas. Previous work has shown that AD of sawdust (SD) and CM with these plant herbs were able to produce biogas and reduce the flies attraction towards the digestate. However, the combination of SW and PPM for AD of CM has yet to be investigated. This work describes the effect of mixing SW and PPM on the co-AD of SDCM with respect to biogas production, methane yield and kinetic analysis. The mixture of SW and PPM was varied at different concentrations. The composition of methane in biogas was characterized every 10 days by using gas chromatography (GC) equipped with a thermal conductivity detector (TCD). The results suggest that co-AD of 10SW10PPM exhibited the highest biogas production (52.28 mL/gvs) and methane yield (30.89 mL/gvs), which the purity of methane increased by 18.52% as compared to SDCM. However, increasing the concentration of SW and PPM does not significantly improve the overall process. High R2 (0.927-0.999), low RMSE (0.08-0.61) and low prediction error (<10.00%) were displayed by the modified Gompertz, logistic and Cone models. In contrast, Monod and Fitzhugh model is not preferred for the co-AD of SDCM with a mixture of SW and PM, as a high prediction error is obtained throughout the study. Increasing the dosage of PPM decreases the maximum cumulative methane yield, ranging from 31.76 to 7.01 mL/gvs for modified Gompertz and 89.56 to 19.31 mL/gvs for logistic model. The Modified Gompertz obtained a lag phase of 10.01-28.28 days while the logistic model obtained a lag phase of 37.29-52.48 days.

Organic loading influences the effectiveness of producing biogas through anaerobic digestion. This study set out to investigate the effect of organic loading on the anaerobic mesophilic digestion of cow dung, the parameters involved in the digestion process and to evaluate the kinetics. Anaerobic digestion of cow dung at different organic loading (gVS/L) of 14 gVS/L, 18gVS/L, 22 gVS/L, 26 gVS/L and 30 gVS/L were investigated. Increasing the organic loading increased the methane yield of the cow dung. The highest cumulative methane yield was observed at 30 gVS/L with 63.42 mL CH4/gVS while the highest biogas yield was reported at 192.53 mL/gVS with the highest methane content of 89%. In addition, the modified Gompertz model equation with an R2 of 0.9980 demonstrated strong consistency and a good fit between predicted and experimental data. The high number of substrates added to the systems when increasing the organic loading increased the λ and slow down the nutrient transport and hydrolysis. This study provides current information on the effects of organic loading on the anaerobic digestion of cow dung in batch mode, including experimental conditions and operational parameters.

Biogas reactors run on various types of waste, with cattle dung and agricultural wastes being the primary sources in India. As biogas contains 50-60% methane, there is a possibility that the reactors harbour methanotrophs or methane-oxidizing bacteria. We set up serial endpoint dilution enrichments for the cultivation of methanotrophs using slurry from a small biogas reactor and cattle dung samples and obtained cultures of Methylocaldum gracile, a thermotolerant methanotroph. The study was expanded by sampling reactors of another small reactor of 20 L capacity and two 1000 L reactors. Dung samples were obtained from two Indian cattle breeds (Tharparkar and Gir). Pulverized rice straw used for feeding the biogas was also used for experiments. All the enrichment bottles were incubated at 39 °C, the reactors\' in-situ temperature, and the rumen gut temperature. Our study isolated four pure cultures most related to Methylocaldum gracile VKM-14LT, two strains from cattle dung samples, and two from reactors. The study also resulted in the cultivation of four additional cultures of Methylocaldum gracile and Methylocaldum tepidum, which were non-axenic and identified by pmoA gene sequencing. Pure cultures Methylocaldum gracile RS-9 and CDP-2 were studied for optimum temperature and oxygen. Both the strains were thermotolerant and grew in the temperature range of 25-45 °C with the optimum between 37 and 45 °C. The cultures could grow with minimal oxygen (0.5%-1%) in the headspace, with growth up to 10% oxygen. To summarize, we report the cultivation and isolation of methanotrophs from biogas slurries and cattle dung samples. Methylocaldum was the dominant methanotroph cultured, probably due to its thermotolerant nature and the ability to grow under variable oxygen conditions. The present study also expands the existing knowledge about habitats known for the genus Methylocaldum. An analysis of the isolated cultures would help us design strategies for methane mitigation from ruminants.

In the current energy and environmental framework, the environmental impact of the road transport sector and the urban waste management and disposal are extremely important for highly crowded cities. This work assesses the energy, economic and environmental performance of an innovative paradigm for the full decarbonisation of the road transport sector. This problem is integrated with the management of the organic fraction of municipal solid waste. In particular, the proposed technology is based on an anaerobic digestion plant coupled with a biogas upgrading unit, for the production of biomethane. In addition, photovoltaic panels and solar thermal collectors are also considered for matching electrical and thermal demands, in order to achieve a fully-renewable system. To this scope, the system also includes suitable thermal and electric storages. The economic analysis also considers specific public funding policies, currently available for this technology. This system aims to be a novel paradigm in the energy scenario of waste disposal and road transport sector refurbishment. TRNSYS software was adopted to perform an accurate dynamic simulation for a one-year operation of the system. The anaerobic digestion model is developed by the authors in MatLab and integrated in TRNSYS, for dynamic simulation purpose. Results show that the plant is almost self-sufficient due to the integration of storage systems for both the thermal and electric energy. The photovoltaic system is able to reduce by 45% the energy dependence from the grid. Energy and environmental analyses show a Primary Energy Saving of 126% and a reduction of CO2 equivalent emissions by 112%. The economic feasibility analysis shows a promising Simple Payback period of 6 years.

This paper presents an overview of solar biogas simulation and optimizing performance of biogas using a renewable energy source such as solar energy. Biogas has many benefits to our environment and climate. Biogas is a renewable fuel produced by the breakdown of organic matter such as food scraps and animal waste, and we can use the biogas to generate electricity. For simulation of biogas, we used RStoic and RCSTR rectors. A feed rate of 0.333 kg/day wet waste and 0.333 kg/day water was used to achieve the maximum biomethane (CH4) production rate of 85.5627% at a temperature of 318.15 K and 15 days of batch process. In this simulation, we use solar energy to apply heat to the digester unit and provide proper preferable conditions. In this process, carbon dioxide and hydrogen sulfide are additionally generated gases. Generated biomethane (CH4) has many uses such as in biomethane filling stations. In 2015, approximately 697 biomethane (CH4) filling stations used 0.16 billion m3 of biomethane as a transportation fuel.

Despite the potential benefits of anaerobic digestion in the context of climate change and the need to move towards energy transition, there is a lot of resistance to biogas projects. Using a contingent valuation method, we test the extent to which the socio-economic characteristics of populations influence the environmental effort that people are willing to make for the deployment of biogas in a French region. Our results show that young people and people familiar with the biogas process are more inclined to develop biogas. We also highlight that the educational and location aspects should not be neglected in order to increase environmental effort and promote the adoption and development of biogas.

The rapid growth in dairy production leads to increasing outputs of high-load effluent, necessitating new methods of treating such waste. Anaerobic processes have been increasingly popular but are hamstrung by limited nutrient removal efficiency. The aim of the present study was to investigate whether low-cost recycled filling (LCRF) improves the anaerobic treatment of dairy effluent. The addition of LCRF was found to increase both COD removal (86.1 ± 2.6%-92.8 ± 1.6%) and Ptot. removal (22.1 ± 3.5% to 36.9 ± 4.6%) from the wastewater. The LCRF ensured near-neutral pH and stabilized the structure of the anaerobic microbe community (including Archaea) across all pollutant loads tested. This translated to efficient biogas production and high methane content in the LCRF reactors, peaking at 0.35 ± 0.01 m3/kg CODremoved and 68.2 ± 0.6% (respectively) in the best-performing variant.