Gaseous Biofuels Research Articles

Study of the Technical and Operational Parameters of Injectors Using Biogas Fuel

Using biogas fuel in a modern internal combustion engine equipped with gas equipment of the fourth and fifth generations can create several difficulties. This is due to the low heat of combustion of untreated biogas, the presence of moisture, and the specifics of the injectors. The main problem of the studies we considered is that there are no data on the operating parameters of biogas fuel injectors. Studies on the parameters of the Matrix, Barracuda, Valtek, Hana, and Keihin injectors in relation to biogas fuel were carried out according to performance indicators, the linearity of operation, the resistance of the injectors, the ability to maintain factory parameters, and service life. According to the indicators of performance and linearity of work, Valtek injectors have the highest deviation in productivity and linearity of work, with an average of 38.8%, and the lowest deviation of Barracuda injectors is 7.5%. Keihin (15.3%) and Hana injectors (19.1%) also showed good performance indicators, and therefore can be used effectively for biogas fuel systems. As a result of research on the response time of the injectors, it was established that the best indicators were found for Hana (1.75 ms) and Keihin (1.99 ms) injectors. Valtek injectors showed good response rates (2.07 ms), as did Barracuda injectors (2.19 ms), but the highest response time was found in Matrix injectors, with 2.44 ms. Keihin injectors had the lowest average resistance value of 1.25 ohms, and Valtek injectors had the highest resistance value of 3 ohms. According to the research results, Keihin, Matrix, and Barracuda injectors provide the best ability to maintain factory performance when using biogas fuel at 2 to 5%, and Valtek had the worst performance up to 20%. Keihin, Barracuda, and Hana experimental injectors had the highest service life, which is from 200 to 250 thousand km of car mileage. The lowest indicators were found for Valtek and Matrix injectors, the service life of which varies from 70 to 100 thousand km of mileage.

Sustainable Production of Biofuels from Biomass Feedstocks Using Modified Montmorillonite Catalysts.

The rampant exploitation of fossil fuels has led to the significant energy scarcity and environmental disruption, affecting the sound momentum of development and progress of human civilization. To build a closed-loop anthropogenic carbon cycle, development of biofuels employing sustainable biomass feedstocks stands at the forefront of advancing carbon neutrality, yet its widespread adoption is mainly hampered by the high production costs. Montmorillonite, however, has garnered considerable attention serving as an efficient heterogeneous catalyst of ideal economic feasibility for biofuel production, primarily due to its affordability, accessibility, stability, and excellent plasticity. Up to now, nevertheless, it has merely received finite concerns and interests in production of various biofuels using montmorillonite-based catalysts. There is no timely and comprehensive review that addresses this latest relevant progress. This review fills the gap by providing a systematically review and summary in controllable synthesis, performance enhancement, and applications related to different kinds of biofuels including biodiesel, biohydrogenated diesel, levulinate, γ-valerolactone, 5-ethoxymethylfurfural, gaseous biofuels (CO, H2), and cycloalkane, by using montmorillonite catalysts and its modified forms. Particularly, this review critically depicts the design strategies for montmorillonite, illustrates the relevant reaction mechanisms, and assesses their economic viability, realizing sustainable biofuels production via efficient biomass valorization.

Mass flow and microbial shifts in recirculated two-phase anaerobic digestion for biohythane production: Effect of hydraulic retention time

Biohythane, the promising gaseous biofuel, can be produced by the recirculated two-phase anaerobic digestion (R-TPAD). The effect of hydraulic retention time (HRT) as 30, 20 and 10 days on biohythane production via R-TPAD (recirculation ratio = 0.4) was investigated with co-digestion of food waste and paper waste. The results showed that HRTs of 30 and 20 days maintained stable performance for R-TPAD but HRT of 10 days led to the final decrease in biogas production. The failure in the end was attributed to the wash-out of microbes. The removal efficiencies for COD and carbohydrates were decreased by short HRTs while for VS it remained relatively stable at about 75.7 ± 4.0%. All through the operation, acidogenic phase and methanogenic phase were separated stably and butyrate pathway was the dominant pathway for hydrogen fermentation in the first stage. The microbial community in the first stage reached the highest diversity when total HRT was 20 days, where the hydrogen production rate was the highest. The genera Lactobacillus and Caproiciproducens kept dominating the dark fermentation in the acidogenic phase, and Ruminococcus and Methanosarcina were decreasing in the methanogenic phase. The biohythane yields were 411 mL/g-VSfed, 332 mL/g-VSfed and 253 mL/g-VSfed, respectively, where the H2 contents were 18.4%, 14.7% and 8.8%, respectively.

Performance and environmental sustainability studies on a dual-fuel IC engine working with producer gas of variable calorific values from rural biomass.

Decentralized power generation using renewable gaseous biofuels faces challenges due to their inconsistent quality and availability. Mixing producer gas (PG) with diesel as a secondary fuel is a promising option, but the non-stable calorific value (CV) of PG from different biomasses poses a serious problem for the efficient operation of a dual-fuel engine. This study aims to examine how the CV of PG from various biomasses affects a 3.75-kW dual-fuel IC engine's performance. The experimental facility, which has a dual-fuel engine and a 115-kW thermal gasifier, tested the blends of diesel and PG from different biomasses. We chose biomass based on its availability and PG's CV of 3.4, 4.4, 5.2, and 6.3MJ/Nm3. For this range of CV, the efficiency, energy consumption, and fuel replacement of a dual-fuel engine vary between 20.9 and 26.6%, 17.3 and 13.5MJ/kWh, and 10.8 and 76.9%, respectively. Furthermore, the blend with the maximum CV of PG had a 69.64% lower specific diesel consumption and an 86% higher diesel replacement rate than the blend with the lowest CV of PG. In terms of emission characteristics, the comparison showed a 2.02-7.06% reduction in NOx and a 4.05-55.6% increase in hydrocarbons (HCs) for the tested conditions. The overall observations demonstrated that a significant enhancement in a dual-fuel engine's performance is possible with a higher CV of PG. However, the emissions trade-offs demand additional optimization studies, as well as case-based research, in order to integrate renewable energy and emission management in smaller-scale applications across more geographies.

Investigation effects of different calorific values and operating conditions on biogas flame: a CFD study

ABSTRACT This study investigates different biogas fuels’ and operating conditions’ effects on flame temperatures and emissions (CO, CO2, NOx, and soot). Different calorific values (15.580, 17.880, 20.430, 23.080, and 26.230 MJ/kg) were obtained by changing methane content. Furthermore, various gas pressure (0.5, 1, 2, and 3 atm), excess air coefficient (1.4, 1.8, 2.5, and 4), and oxygen values (21, 23, 25, and 27%) were simulated for 8.6 kW thermal capacity furnace. Increasing the calorific value of biogas fuels, CO, NOx, and soot emissions and flame length tend to increase, while CO2 decreases. Increasing gas pressure, flame temperature, and CO2, CO, and NOx decrease, while soot emissions tend to increase. As a result of the decrease in the air excess coefficient from 4.0 to 1.4, there is a increase in the flame temperature, flame length, and soot, CO, CO2, and NOx emissions. On the other hand, oxygen content from 21% to 27% oppositely affected these parameters, excluding flame length.

Possibilities of Utilising Biomass Collected from Road Verges to Produce Biogas and Biodiesel

Grass collected as part of roadside maintenance is conventionally subjected to composting, which has the disadvantage of generating significant CO2 emissions. Thus, it is crucial to find an alternative method for the utilisation of grass waste. The aim of this study was to determine the specific biogas yield (SBY) from the anaerobic mono-digestion of grass from road verges and to assess the content of Fatty Acid Methyl Esters (FAMEs) in grass in relation to the time of cutting and the preservation method of the studied material. The biochemical biogas potential (BBP) test and the FAMEs content were performed on fresh and ensiled grass collected in spring, summer, and autumn. The highest biogas production was obtained from fresh grass cut in spring (715.05 ± 26.43 NL kgVS−1), while the minimum SBY was observed for fresh grass cut in summer (540.19 ± 24.32 NL kgVS−1). The methane (CH4) content in the biogas ranged between 55.0 ± 2.0% and 60.0 ± 1.0%. The contents of ammonia (NH3) and hydrogen sulphide (H2S) in biogas remained below the threshold values for these inhibitors. The highest level of total FAMEs was determined in fresh grass cut in autumn (98.08 ± 19.25 mg gDM−1), while the lowest level was detected in fresh grass cut in spring (56.37 ± 7.03 mg gDM−1). C16:0 and C18:0, which are ideal for biofuel production, were present in the largest amount (66.87 ± 15.56 mg gDM−1) in fresh grass cut in autumn. The ensiling process significantly impacted the content of total FAMEs in spring grass, leading to a reduction in total saturated fatty acids (SFAs) and an increase in total unsaturated fatty acids (USFAs). We conclude that grass biomass collected during the maintenance of road verges is a valuable feedstock for the production of both liquid and gaseous biofuels; however, generating energy from biogas appears to be more efficient than producing biodiesel.

Renewable gases production coupled to synthetic wastewater treatment through a microbial electrolysis cell

This study describes the use of a microbial electrolysis cells for the production of gaseous biofuels sustained by the oxidation of a synthetic wastewater. During the overall experimental investigation, the MEC’s bioanode removed on average 855 ± 57 mgCOD/d producing an average electric current of 66 ± 7 mA which was diverted into gaseous biofuels like biomethane, biohydrogen and biohythane. Three different MEC cathodic configurations were investigated selecting the electrodic materials (graphite granules GG, and mixed metal oxide MMO) and operating conditions (pH of the catholyte, additional sorption chamber). Biomethane production increased from 26 ± 4–102 ± 8 meq/d when the MMO electrode was used with respect to GG electrodic material. In contrast, the MMO electrode in combination with a CO2 sorption chamber was successfully utilized for simultaneous H2 production and CO2 sorption from a N2/CO2 mixture which simulates an anaerobic digestion biogas. The combination of H2 production and CO2 sorption allowed to obtain a gaseous mixture composed of 9% H2, 5% CO2, and 80% N2 that according to the assumption of replacing the N2/CO2 mixture with real biogas corresponded to a commercial-grade biohythane. Overall, the results highlight the potential of MECs as an efficient approach for biogas upgrading, allowing biohythane production increasing CH4 content and lowering CO2 concentration.

Biotechnological Valorization of Waste Glycerol into Gaseous Biofuels—A Review

The supply of waste glycerol is rising steadily, partially due to the increased global production of biodiesel. Global biodiesel production totals about 47.1 billion liters and is a process that involves the co-production of waste glycerol, which accounts for over 12% of total esters produced. Waste glycerol is also generated during bioethanol production and is estimated to account for 10% of the total sugar consumed on average. Therefore, there is a real need to seek new technologies for reusing and neutralizing glycerol waste, as well as refining the existing ones. Biotechnological means of valorizing waste glycerol include converting it into gas biofuels via anaerobic fermentation processes. Glycerol-to-bioenergy conversion can be improved through the implementation of new technologies, the use of carefully selected or genetically modified microbial strains, the improvement of their metabolic efficiency, and the synthesis of new enzymes. The present study aimed to describe the mechanisms of microbial and anaerobic glycerol-to-biogas valorization processes (including methane, hydrogen, and biohythane) and assess their efficiency, as well as examine the progress of research and implementation work on the subject and present future avenues of research.

The Simulation of Biogas Combustion in Top Open Burner

The top open furnace is commonly used for the heating processes. The efficiency of the top open furnace is low due to the amount of heat wasted through the top open. This study was using ANSYS Fluent, a two-dimensional computational fluid dynamic (CFD) model that was used to build the top open furnace. Exhaust gas recirculation (EGR) was installed in the boiler in order to collect the exhaust gas and reuse it to dilute the oxygen supply. To check the combustion of low calorific gas (LCV) gas, which is biogas composed of 60% methane and 40% carbon dioxide by mass fraction, the computational study started with a standard combustion with EGR. Medium-sized mesh is used for the smoothing grid. This mesh uses inflation to enable the size of the cells and the stack element. The findings of the numerical sensitivity test show that the boundary conditions along the combustion chamber wall can affect the flame temperatures. The MILD regime was reached using biogas fuels when the right parameters were used.

Adaptive Back-Propagation Neural Network and Particle Swarm Optimization-Based Approach for Optimizing the Output Power Biogas Fueled Electric Generator

Adaptive Back-Propagation Neural Network and Particle Swarm Optimization-Based Approach for Optimizing the Output Power Biogas Fueled Electric Generator

Evaluation of hardwood or softwood bark biomass as feed materials for aqueous-phase reforming gasification process

In the present study, pine (Pinus brutia) and poplar (Populus alba) tree barks, softwood and hardwood representative biomass were evaluated for production of gas biofuel, hydrogen by aqueous-phase reforming. The proximate composition, elemental composition, higher heating values (HHVs), proximate thermogravimetric and differential thermogravimetric analysis (TGA/DTG), fourier transform infrared (FT-IR), and volatile composition of these biomass materials were determined and their effect on gasification performance of the softwood and hardwood biomass were evaluated. Gasification was performed by aqueous-phase reforming of solubilized liquid fraction of the biomass materials in presence of carbon-supported Pd catalyst which was synthesized in the present study. Softwood contained significantly higher levels of ash and volatile matter, with lower hemicellulose but higher lignin content. Gasification results showed that softwood produced slightly higher amounts of hydrogen with significantly lower carbon monoxide compared to hardwood. Although solid hardwood bark composition was expected to produce more gaseous products, the results observed were opposite. The dissolution of biomass in pressured hot water prior to gasification resulted in a more dilute hydrolysate in softwood compared to hardwood, positively influencing the gasification performance. Despite of many advantages of the aqueous-phase reforming (APR) gasification process used in the present study, the process still needs to be improved further to make the process more economical. To increase the advantage of this process, new catalysts that are more robust and active and have high stability in organic-rich APR conditions should be developed.

Enhancing bio-hydrogen and bio-methane production of concentrated latex wastewater (CLW) by Co-digesting with palm oil mill effluent (POME): Batch and continuous performance test and ADM-1 modeling

This study aimed at investigating the biohydrogen and biomethane potential of co-digestion from palm oil mill effluent (POME) and concentrated latex wastewater (CLW) in a two-stage anaerobic digestion (AD) process under thermophilic (55 ± 3 °C) and at an ambient temperature (30 ± 3 °C) conditions, respectively. The batch experiments of POME:CLW mixing ratios of 100:0, 70:30, 50:50, 30:70, and 0:100 was investigated with the initial loadings at 10 g-VS/L. The highest hydrogen yield of 115.57 mLH2/g-VS was obtained from the POME: CLW mixing ratio of 100:0 with 29.0 of C/N ratio. While, the highest subsequent methane production yield of 558.01 mLCH4/g-VS was achieved from hydrogen effluent from POME:CLW mixing ratio of 70:30 0 with 21.8 of C/N ratio. This mixing ratio revealed the highest synergisms of about 9.21% and received maximum total energy of 19.70 kJ/g-VS. Additionally, continuous hydrogen and methane production were subsequently performed in a series of continuous stirred tank reactor (CSTR) and up-flow anaerobic sludge blanket reactor (UASB) to treat the co-substate. The results indicated that the highest hydrogen yield of POME:CLW mixing ratio at 70:30 of 95.45 mL-H2/g-VS was generated at 7-day HRT, while methane production was obtained from HRT 15 days with a yield of 204.52 mL-CH4/g-VS. Thus, the study indicated that biogas production yield of CLW could be enhanced by co-digesting with POME. In addition, the two-stage AD model under anaerobic digestion model no. 1 (ADM-1) framework was established, 9.10% and 2.43% of error fitting of hydrogen and methane gas between model simulation data and experimental data were found. Hence, this research work presents a novel approach for optimization and feasibility for co-digestion of POME with CLW to generate mixed gaseous biofuel potentially.

BACKGROUND FOR THE USE OF HYDROGEN IN UKRAINE IN THE ENERGY AND AUTOMOTIVE SECTORS

Based on the global trends, the article substantiates the place of hydrogen and hydrogen technologies in the further decarbonisation of the energy sector and road transport in Ukraine. The variety of methods of production, transportation and storage, and the use of hydrogen of different purity require complex trade-offs between the cost of the technology and the amount of possible emissions of harmful substances into the environment at all related stages of application of these technologies. Hydrogen fuels and hydrogen technologies should be positioned as one of the areas of energy transition of economic sectors to decarbonisation, which will lead to the development of climate-neutral technologies. Traditional reciprocating internal combustion engines (ICE) can be upgraded to run on purely hydrogen fuel, but this requires the use of new materials due to the high specific energy intensity of hydrogen. The combustion of hydrogen in ICE combustion chambers is hindered by nitrogen oxide (NOX) emission restrictions. A possible option is to use a mixture of hydrogen and natural gas or to upgrade dual-fuel internal combustion engines. This is the most realistic option for Ukraine at this point. In light of the decarbonisation process, the main advantage of fuel cells (FC) is the absence of hydrocarbon combustion and, accordingly, the ability to reduce air pollution with the greenhouse gas CO2. Existing FC can operate not only on hydrogen but also on natural gas. In the energy sector, hydrogen technologies compete not with traditional methods of generating heat and electricity, but with bioenergy, heat pumps, and technologies for capturing and storing carbon and its oxides. In the automotive sector, hydrogen technologies compete with liquid and gaseous biofuels, electric vehicles and hybrids with internal combustion engines and batteries. The potential application of hydrogen technologies for decarbonisation processes will only be unlocked once a hydrogen market and the relevant infrastructure are in place. The segment and price of hydrogen technologies depend on by the method of production process chosen, as well as the infrastructure components, including storage, transportation and fuelling stations. The safe operation and implementation of hydrogen technologies in Ukraine requires qualified engineering staff. The training of such specialists for the energy and transport sectors can be taken on by universities by universities in the speciality 142 – energy engineering.

A Review of Liquid and Gaseous Biofuels from Advanced Microbial Fermentation Processes

Biofuels are the sustainable counterparts of fossil fuels to meet the increasing energy demands of the current and future generations. Biofuels are produced from waste organic residues with the application of mechanical, thermochemical and biological methods and processes. While mechanical and thermochemical conversion processes involve the use of heat, pressure, catalysts and other physicochemical attributes for the direct conversion of biomass, biological conversion requires microorganisms and their enzymes as biocatalysts to degrade the fermentable substrates into biofuels and biochemicals. This article highlights the advances and opportunities in biological conversion technologies for the development of a closed-loop biorefinery approach. This review highlights the distinction between biological and thermochemical conversion technologies, including a discussion on the pros and cons of the pathways. Different categories of biological conversion processes, such as enzymatic saccharification, submerged fermentation, solid-state fermentation and simultaneous saccharification and fermentation are also discussed in this article. The main essence of this article is the description of different fermentative technologies to produce next-generation biofuels, such as bioethanol, biobutanol, biomethane, biohydrogen and biodiesel. This article provides a state-of-the-art review of the literature and a technical perspective on the bioproduction of bioethanol, acetone–ethanol–butanol fermentation, anaerobic digestion, photo/dark fermentation, and the transesterification of lignocellulosic substrates to produce the above-mentioned biofuels. In addition, recommendations for improving bioprocessing efficiency and biofuel yields are provided in this comprehensive article.

Improving biomethane production from biochar-supplemented two-stage anaerobic digestion of on-farm feedstocks

On-farm feedstocks such as grass silage and cattle slurry present recalcitrant characteristics that can limit microbial conversion in biofuel production. Introducing a biochar supplement in two-stage anaerobic digestion may facilitate feedstock hydrolysis and improve energy yields in biohydrogen and biomethane production. The biomethane potentials were first investigated in batch trials without biochar supplement; results indicated a biomethane yield of 230 L per kilogram (kg) volatile solid (VS) in single-stage digestion and 275 L/kg VS in two-stage digestion. In continuous trials, operated at an organic loading rate of 4.0 g VS/L/d, the second-stage digester in two-stage digestion showed a methane yield of 237 L/kg VS with 10 g/L biochar addition; this was 7% higher than the second-stage digester without biochar addition. At the same loading rate of 4.0 g VS/L/d, the biomethane yield in continuous single-stage digestion with 10 g/L biochar addition was 212 L/kg VS; this was 3% higher than the single-stage digester without biochar addition. Biochar was found to enhance the hydrolysis of recalcitrant solid components in the hydrogen-producing phase, promote biomethane production in methanogenesis, and stabilize the digestion process. The highest energy yield of 8.5 MJ hydrogen and methane per kg VS was achieved in the two-stage digestion with 10 g/L biochar addition at a loading rate of 4.0 g VS/L/d. The results demonstrated that the application of a biochar supplement could effectively enhance gaseous biofuel production in two-stage anaerobic digestion.

A concise review of technologies for converting forest biomass to bioenergy

The use of biomass is vital in reducing the negative effects of rising fossil fuel consumption. Given its quantity and diversity, forest biomass has garnered a lot of interest among the many kinds of biomass. This study evaluates the various strategies for transforming woody waste into usable biofuels. Carbon dioxide emissions from traditional energy generation systems could be mitigated through the direct utilization of forest biomass. Low energy conversion rates, as well as soot emissions and residues, are some of the problems that come up when directly using forest biomass. The sustainability of direct energy generation from forest biomass is also seriously threatened by the lack of constant access to biomass. Co-combustion with coal and pelletizing biomass is two solutions proposed for this issue. Co-combustion of forest biomass with coal has the potential to lower the process's emissions of carbon monoxide, nitrogen oxides, and sulfides. This article reviews and discusses the biochemical and thermochemical mechanisms that can transform forest biomass into a variety of liquid and gaseous biofuels. Future research using cutting-edge sustainability assessment tools like life cycle assessment, exergy, etc. should investigate the sustainability of forest biomass conversion processes to bioenergy further.

Catalytically Active and Carbon-Resistive Anode Catalyst for Solid-Oxide Fuel Cells Operated at Low Temperatures (500–600 °C)

The development of active catalysts is always challenging in the field of energy devices. In this work, Li-doped, Ni–Cu-based, and Ni-free nanocomposite anode catalysts are synthesized and studied for solid-oxide fuel cells (SOFCs) operated at a low temperature using hydrogen and biogas as fuels. The catalysts with compositions Ni0.6Li0.2Cu0.2-oxide/La0.2Ce0.8O2-δ (NLC622-LDC), Ni0.2Li0.2Cu0.6-oxide/La0.2Ce0.8O2-δ (NLC226-LDC), and Ni0.0Li0.2Cu0.8-oxide/La0.2Ce0.8O2-δ (NLC028-LDC) are synthesized using the glycerol-assisted gel combustion route (GGCR). The structural analysis revealed the cubic structure of metallic oxide materials such as NiO and CuO phases while the cubic fluorite structure of CeO2 as an ionic oxide phase. The optical band gaps (Eg’s) of anode catalysts NLC622-LDC, NLC226-LDC, and NLC028-LDC are found to be 2.08, 2.29, and 2.37 eV, respectively. Furthermore, the anode catalyst with a higher nickel concentration shows better electrical conductivity and a lower activation energy of 3.47 S cm–1 and 0.67 eV at 600 °C, respectively, as compared to those of a nickel-free anode catalyst with lower nickel content. The electrochemical behavior of nanocomposites is studied at 600 °C using Nyquist plots. Electrochemical impedance analysis is carried out to see the effect of hydrocarbon fuel like biogas at the anode side. Finally, the electrochemical performance of NiLiCu-LDC catalyst-based fuel cells is tested under hydrogen and biogas fuels. Overall, the fuel cell based on the NLC622-LDC anode catalyst has higher OCV and power density with both fuels, hydrogen and biogas. Therefore, NLC622-LDC is a highly catalytically active anode catalyst which demonstrated significantly better performance for SOFCs operated at a low temperature (500–600 °C) without any carbon resistance.

Agricultural Plant Residues as Potential Co-Substrates for Biogas Production

Plant biomass can be used in many directions for bioenergy production. Biogas can be produced from a most diverse group of substrates compared to liquid or solid biofuels. The choice of substrates and technologies is crucial because it will allow getting the expected results. Not without significance is also the price and availability of substrates. Therefore, waste and residues are increasingly being used. Accordingly, the aim of the review was to analyze the potential of biogas production from agricultural plant residues and the effectiveness of using this feedstock as a co-substrate in anaerobic digestion. In this article, selected agricultural plant residues are collected, and their advantages and disadvantages as substrates for biogas production are described. Moreover, the effective technology of biogas production by anaerobic digestion on an industrial scale and calculations to obtain biogas and methane efficiency of the substrates are also included. In addition, the summarized biogas efficiency of selected plant agricultural waste under mesophilic conditions studied by many researchers is shown. On the basis of the analyzed results of this research, it can be concluded that agricultural plant residues have great potential as co-substrates for biogas production. It is important to experimentally determine both the biogas and the methane efficiency of the substrate, representing a potential raw material for the production of gaseous biofuels. The use of artificial neural networks in the prediction of biogas emission is future-proof and should facilitate the management of biogas plants. The use of waste from the cultivation and processing of plant raw materials will not only help to manage this waste rationally, but also contribute to the increase in production of renewable energy sources. Accordingly, the circular economy in terms of the management of agricultural plant residues to produce biogas will have a multi-faceted, positive impact on the environment. On the basis of this review, it can be concluded that numerous agricultural plant residues can be used as potential co-substrates for biogas production.

Emerging trends in role and significance of biochar in gaseous biofuels production

Emerging trends in role and significance of biochar in gaseous biofuels production

Effects of oxytetracycline on mesophilic and thermophilic anaerobic digestion for biogas production from swine manure

Anaerobic digestion (AD) technology is a valuable method for producing biogas fuels and treating livestock wastes such as swine manures concurrently. However, the effect of emerging antibiotics on the AD process is still undiscovered. In this study, the influence of oxytetracycline (OTC) on the AD process was investigated under mesophilic (35 ± 0.5 °C) and thermophilic (55 ± 0.5 °C) conditions, respectively. The presence of OTC significantly inhibited the production of methane in AD process, where the methane yields decreased by 58.6% and 73.3% in mesophilic and thermophilic ADs when the initial concentration of OTC was 400 mg/L, respectively. Besides, OTC can be markedly degraded by the AD process with a removal efficiency higher than 90% when the OTC initial concentration is lower than 10 mg/L. Furthermore, a higher concentration OTC led to a lower biomethane yield, energy conversion efficiency, and contaminant removal during both mesophilic and thermophilic ADs. With adding of 400 mg/L OTC, Clostridium sensu stricto 1 (32.9%) and Anaerolinea (29.3%) are dominant to biodegrade organic matter during mesophilic and thermophilic AD systems. Correspondingly, Methanosaeta was functional in producing biomethane in both mesophilic (60.8%) and thermophilic (56.4%) AD systems. Additionally, Methanolinea was bearable to high concentrations of OTC during mesophilic and thermophilic AD processes.