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The effects of steam and sulfuric acid pretreatment on anaerobic digestion (AD) of whiskey byproducts (including draff, thin and thick stillage) were investigated in order to improve the digestion performance under both mesophilic and thermophilic temperatures. The results of biomethane potential assays suggested that thermophilic AD facilitated the release of free ammonia (ca. 1200 mg/L) from byproducts, resulting in strong ammonia inhibition and volatile fatty acid accumulation. In contrast, no free ammonia inhibition (ca. 700 mg/L) was observed under mesophilic AD; the methane yield from mesophilic AD was between 375.3 ± 13.6 mL/g volatile solid (VS; acid-treated sample) and 389.1 ± 8.5 mL/g VS (untreated sample). Although acid pretreatment (2% acid under 135 °C for 15 min) did not improve the methane yield from mesophilic AD, it reduced the digestion time by 14.3% compared to that of the untreated sample. Microbial community analysis showed that irrelevant of pretreatment, hydrogenotrophic methanogens of Methanobrevibacter (28.9%–49.8% in abundance) and Methanoculleus (26.0%–55.9% in abundance) were the dominant archaeal genus under mesophilic AD. In comparison, hydrogenotrophic Methanothermobacter (over 97% in abundance) were dominant in thermophilic AD. This study could be exploited to aid in decarbonizing the whiskey industry by optimizing the biogas process in a circular economy system.

In this study, the links between performance and microbial communities were investigated with municipal solid waste (MSW) at two feedstock ratios and eight organic loading rates (OLRs). The co-digestion systems were stably operated at OLRs of 2.0–6.0 g VS/(L·d). The performance of the co-digestion system varied with the feedstock ratio. Compared with the 50:50 (hybrid Pennisetum:MSW) system, the 75:50 system, GM31, obtained increases of 1.93–17.68% and 0.29–23.29% for the specific biogas and methane yields, respectively. Whereas a shift in bacterial and methanogen communities occurred as the operating conditions changed, particularly with OLR variations. The genera Saccharofermentans, Prevotella, Clostridium, Syntrophomonas, and Proteiniphilum became the dominant bacteria for the conversion of carbohydrates and nitrogen compounds as the OLR increased. Meanwhile, a shift from acetoclastic to hydrogenotrophic or multifunctional methanogens was observed.

This study investigated the effects of organic loading rates (OLRs) and temperature on the performance and stability of anaerobic digestion treating the organic fraction of municipal solid waste (OFMSW) in a semi-continuous mode. Furthermore, a preliminary energy analysis was conducted to determine the optimal application parameters for anaerobic digestion of OFMSW. Results showed that the maximum achievable OLR was 9.00 g VS/(L·d), with a volumetric biogas yield of 4.03 L/(Ld) and 4.31 L/(Ld) for mesophilic and thermophilic systems, respectively. However, the preliminary energy analysis showed higher energy conversion efficiency was achieved for the system operated at an OLR of 7.50 g VS/(L·d). The system operated at the thermophilic condition had a higher total energy due to more electricity and heat energy generated than the mesophilic one. Therefore, the recommended operating conditions for the anaerobic digestion of OFMSW is an OLR of 7.50 g VS/(L·d) and thermophilic condition. Based on the annual yield of OFMSW in China, the estimated net output energy was 69970.61 GWh per year.

To overcome the inherent complexity of lignocellulosic biomass and improve its biological conversion efficiency, the central composite surface response methodology was used to optimize the process variables (temperature, reaction time and liquid-to-solid ratio) in liquid hot water pretreatment for biomethane production from the anaerobic digestion of Hybrid Pennisetum (a typical energy crop in southern China). Temperature, reaction time and water content were varied between 160–200 °C, 20–60 min and 60–90 mL respectively. The biomethane yields from pretreated material were considered as response variables to different processes conditions. Results showed untreated Hybrid Pennisetum had a biomethane potential of 218.6 L/kg volatile solid (VS) (corresponding to a biodegradability of 62.6%). The effect of liquid hot water pretreatment on the biomethane yield was distinct. Pretreatment severities less than 4.55 resulted in increased biomethane yields. However, further increasing the severity led to lower biomethane yields. The optimum biomethane yield (290.6 L/kg VS) was obtained from pretreated Hybrid Pennisetum at 175 °C for 35 min, with the highest biodegradability of 83.2%. Energy balance showed that, under the optimal pretreatment condition, the highest energy conversion efficiency of 76.1% was attained in theory. If the process energy inputs are included, a process energy efficiency of 51.7% could be realized with proper heat recovery.

This study investigated whether bioaugmentation can improve the anaerobic digestion (AD) performance of food waste (FW), as well as the effects of addition dosage and frequency on the bioaugmentation’s performance and economic feasibility. The findings demonstrated that all the bioaugmented digesters, regardless of dosage and frequency, performed more effectively in biogas production than the non-bioaugmentation control. Furthermore, relatively higher dosages or frequencies increased AD performance. Introducing 0.25 g L−1 d−1 of bioaugmentation seed every three days increased OLR and volumetric biogas production 8-fold and 12-fold, respectively, compared to the non-bioaugmentation control. Whole-genome sequencing analysis showed that bioaugmentation enhanced the population of the acetoclastic Methanothrix (belong to the order Methanosarcinales). Moreover, high abundance of Methanothrix (exceeding 80%) contributed to a better AD performance. Economic analysis of an up-scale biogas plant suggested that an appropriate bioaugmentation process increased income, thus increasing the profit to 3696 CNY d−1 if treated at 21 t FW.

The anaerobic digestion (AD) performance for breakfast, lunch, and dinner kitchen waste (KW) produced by the canteen at Guangzhou University was assessed by a batch experiment under mesophilic and thermophilic conditions. The AD concentrations were 9.54 g VS/L, 20.12 g VS/L, and 39.99 g VS/L, respectively. The concentration of 20.12 g VS/L under thermophilic conditions had the best AD performance among all the KW. The maximum specific methane yield of 591 ± 30 mL/g VS was obtained from dinner KW (D-KW). Due to the differing organic composition, the specific methane yield of D-KW and lunch KW (L-KW) was 41.16% and 19.76% higher than that of breakfast KW (B-KW) under the optimal condition, respectively, whereas that of D-KW was 17.96% higher than that of L-KW. The specific methane yield was significantly correlated to the crude fat content. When the concentration was increased to 39.99 g VS/L, accumulation of toxic materials was observed and the AD process stopped. The potential biogas yield, based on production of 5904.43 tons of KW per year at the Guangzhou Higher Education Mega Center (HEMC), is 1.08 million m3 biogas, equivalent to 2.15 million KW h of electricity.

This study investigated the co-digestion performance of Pennisetum hybrid and cow manure via batch mode tests to optimize the feedstock ratio. On the basis of the batch test results, the long-term operational performance of the co-digestion system at different ratios was assessed at mesophilic temperature and organic loading rates (OLRs) of 2.0–5.5 g of volatile solids (VS) L–1 day–1 via semi-continuous mode. Batch tests showed that the maximum specific methane yield of 170.35 ± 11.61 mL/g of VS was obtained at a Pennisetum hybrid/cow manure ratio of 100:0, with the specific methane yield decreasing with an increased proportion of cow manure. In the semi-continuous experiments, the mono-digestion of Pennisetum hybrid failed at the OLR of 2.0 g of VS L–1 day–1. This failure was accompanied by the accumulation of volatile fatty acids (VFAs). The stable operational OLR increased by 1.0–1.5 times with the addition of cow manure. The volumetric biogas yield increased with the augmentation of the OLR from 2.0 t...

This study is the first to integrate gamma-valerolactone/water (GVL/water) pretreatment with anaerobic digestion (AD) for biogas production and lignin nanoparticles (LNPs) synthesis. The hydrothermal treatment was conducted at 135 to 180 °C with GVL at 0 to 90%. After pretreatment, the compositions of hybrid pennisetum were changed with the removal of lignin, hemicellulose, and cellulose to different extent. Subsequent anaerobic digestion achieved a maximal specific methane yield of 228.00 ± 4.37 mL/g VS, compared with that at 165.11 ± 1.99 mL/g VS for the control. The highest actual methane yield (150 mL/g RM) was achieved by pretreatment with GVL/water (50/50) at 150 °C for 90 min. LNPs at 200 to 2000 nm were synthesized from the liquid waste with a yield at ~4 mg/mL. The mass balance of this integrated method was discussed. In general, the maximal valorisation of hybrid pennisetum was achieved based on a catalyst-free of GVL/water pretreatment.

Bioresource evaluation is prerequisite and important to reduce cost of feedstock collection and avoid battle for feedstock to promote the healthy development of bioenergy industry. This study estimated Thai bioresources from arable field crops, horticultural plants and livestock with product quantity or livestock number, residue-product ratio or manure productivity, and moisture content. Rice straw and husk, para rubber residues and cattle manure separately have the top amount in arable field crop biomass, horticultural residues and livestock manures. The northeastern region has the most amounts of arable field crop biomass and livestock manures, and the southern region possesses the largest quantities of horticultural residues. The available energy potentials from residues of arable field crops and horticultural plants can reach to maximum of 4.91 × 105 TJ and 7.65 × 105 TJ, respectively, which can theoretically share 21.67% of current total primary energy supply. The available biogas potential from livestock manures is nearly ten times than its current generation. After analysis the status of technologies and government policies for Thai bioenergy industry, it indicates that the utilization of bioenergy in the form of electricity, heat and transportation fuels has promising prospect in Thailand. The provinces of Thailand which are more suitable for developing bioenergy industry are suggested. This work may guide the reasonable layout of bioenergy industry in Thailand via the presence of bioresouces distribution in every province.

Elephant grass might be a potential source of fine chemical precursors and bioenergy. In the present study, we investigated the dynamics of hydrolysis of elephant grass. Three models were used to fit the hydrolysis rate constants—flat, spherical, and cylindrical models. The hydrolysis rate constants obtained using the spherical model presented the best fit between the experimental and theoretical values. Furthermore, we determined the secondary reinforcement points and interventions that can be introduced to speed up the hydrolysis process. Our findings will provide information for studies on the hydrolysis of elephant grass and promote its application in the biogas industry as an alternative biofuel.

Material flow analysis (MFA) was applied to study the process of biogas production from switchgrass using a mid-temperature (35 ± 1 °C) batch anaerobic digestion process. The flow distributions of energy and material, including carbon (C) and nitrogen (N), were analyzed, as were the material and energy conversion efficiencies. The results showed that biogas and CH4 production were 268.80 and 135.31 NmLgVS-1 added, respectively, and the average CH4 content in biogas was 50.34%. Based on the MFA of the anaerobic digestion process, 30.6%, 3.6%, and 65.8% of C was converted into biogas, biogas slurry, and biogas residue, respectively; and 11.7% and 88.3% of N was converted into biogas slurry and biogas residue, respectively. The conversion efficiencies of the material and energy from switchgrass to biogas were 36.1% and 30.1%. Because of the low conversion efficiencies of matter and energy during biogas production, it is necessary to strengthen the secondary use of the fermentation residue. This study provides a basis for the optimization of the anaerobic digestion process and efficient utilization of resources and energy of energy-grass.

Alkaline pretreatment with NaOH was used to improve methane yield from Pennisetum Hybrid. The pretreatments were carried out with different NaOH solutions (2–8% w/w) at three temperatures (35, 55 and 121 °C) for different periods of time (24, 24 and 1 h). All treated and untreated Pennisetum Hybrid were digested under mesophilic conditions (37 °C) to biogas, significant effects of the pretreatments on the yield of methane were observed. Results showed the modified Gompertz equation was reliable (determination coefficients (R2) greater than 0.96) to describe the kinetic behavior of anaerobic digestion of Pennisetum Hybrid. The best result, obtained by the treatment at 35 °C 2% NaOH for 24 h, resulted in the methane yield of 301.7 mL/g VS, corresponding to 21.0% improvement in the methane yield. Compositional, SEM, XRD and FTIR analysis confirmed that lignin removal, structural modification and cellulose crystalline variation were responsible for the improvement.

Pretreatment methods play an important role in the improvement of biogas production from the anaerobic digestion of energy grass. In this study, conventional thermal and microwave methods were performed on raw material, namely, Pennisetum hybrid, to analyze the effect of pretreatment on anaerobic digestion by the calculation of performance parameters using Logistic function, modified Gompertz equation, and transference function. Results indicated that thermal pretreatment improved the biogas production of Pennisetum hybrid, whereas microwave method had an adverse effect on the performance. All the models fit the experimental data with R (2) 0.980, and the Reaction Curve presented the best agreement in the fitting process. Conventional thermal pretreatment showed an increasing effect on maximum production rate and total methane produced, with an improvement of around 7% and 8%, respectively. With regard to microwave pretreatment, maximum production rate and total methane produced decreased by 18% and 12%, respectively.

The existing energy is almost provided by carbon-containing fossil sources such as oil and coal. The rapid consumption of these fossil resources causes an accelerated release of CO 2 which is a major cause of global warming and associated climate change. “Green” bio-methane (also named biogas) has the advantage for both reducing over dependency on fossil energy and reducing emissions o CO 2 and other greenhouse gases (GHGs). The purpose of this work is to introduce the biogas utilization ways widely applied in China and indicate the development orientation on clean, effective and economical utilizations. Firstly, biogas in china should gradually walk out from rural family, come into centralized anaerobic digestion (CAD). Secondly, combined production of heat and power (CHP) and upgrading to vehicle fuel should be popularized extensively. Thirdly, biogas fuel cell systems and biogas chemical industry (BCI) should be exploited as a technique reservation.

Low-carbon circular economy strategies within the whiskey industry necessitate minimal use of fossil-based energy including heat and electricity. Renewable energy generated from process by-products such as draff and pot ale offers opportunities for circular bioeconomy systems. However, such a system is yet to be defined and assessed in detail. In this study, biological valorization (dark hydrogen fermentation and anaerobic digestion) of whiskey by-products was comparatively evaluated in terms of fundamental principles and thermodynamics of biochemical reactions. Four scenarios based on a whiskey plant size of 2 million L/a were evaluated to determine the potential energy recovery (in the form of electricity and heat) and CO2 emissions reduction. The recommended scenario with anaerobic digestion of pretreated by-products resulted in a biogas production of 1.72 million m3 (containing 1.03 million m3 biomethane, corresponding to an energy yield of 10,300 MWh). If the produced biogas is used for producing heat and electricity in a combined heat and power system, 446% of the annual electricity demand (740 MWeh) and 25% of the heat demand (4,230 MWthh) of the traditional distillery can be covered, leading to a reduction in energy related CO2 emissions of 61% from whiskey production (2,300 ton CO2). Preliminary economic analysis shows that the proposed system has an annual net income of €741,176 with a payback period of 3.94 years. Net present value of the system is €4,933,456 with a discounted payback period of 4.77 years. Future research on a detailed techno-economic feasibility and life cycle assessment of such a system should be investigated before practical implementation.