Biomethane Production Research Articles

Economic and environmental viability of biofuel production from organic wastes: A pathway towards competitive carbon neutrality

Production of renewable C1 transport biofuels (such as biomethane and biomethanol) through the integration of anaerobic digestion (AD) with carbon capture, utilization and sequestration technologies may offer a solution to reduce greenhouse gas (GHG) emissions. This paper presented a detailed techno-economic and environmental assessment of four cases for biomethane or biomethanol production by incorporating AD, CO2 utilization via biomethanation (CU), solid digestate pyrolysis (Py) and methanol synthesis (MeOH). The results reflected the current state of technologies and potential future scenarios within a mature market. Under optimistic scenarios (scaled-up systems and reduced hydrogen price of 1 €/kg), the minimum potential GHG abatement cost for the AD-Py-CU case was −111.1 €/t CO2-eq when biomethane was sold at 1.03 €/Nm3 (a contract gas price in 2022), while the abatement cost rose to −58.2 €/t CO2-eq when H2 was purchased at 3.40 €/kg. When methanol was sold at 425 €/t (global weighted average value), the marginal abatement cost for the AD-Py-CU-MeOH (with H2 at 1.0 €/kg) case was 136.5 €/t CO2-eq, which is higher than current carbon credits at 33.5 €/t CO2. This study suggests that biomethane produced by incorporating AD, CO2 biomethanation and pyrolysis technologies may be economically and environmentally competitive over natural gas.

Biomass price as a key factor for the further development of biogas and biomethane use – Methodology and policy implications

Intentionally planted biomass is one of the important possible sources for biomethane production. The production cost of biomass plays a key role in both a farmer's decision to grow it and the efficiency of biomethane production. Unlike conventional agricultural crops, biomass grown for biogas or biomethane plants does not have a direct market price. The paper presents a methodology for determining the limit of biomass production price based on modelling lost revenue from planting conventional crops over the lifetime of the biogas or biomethane plant, considering local agrotechnical practices and soil and climatic conditions. The application of the methodology is demonstrated by providing maize biomass for a reference biogas plant and conditions of the Czech Republic. The production price of maize silage is in the range of 25.6–29.4 EUR/tFM for base line scenario of conventional crop prices. The increase in commodity prices in 2021 and 2022 leads to an increase in the biomass production price up to 34–43 EUR/tFM. The paper also discusses the influence of the biomass input price on the cost of biomethane production.

Box-Behnken design and life cycle assessment for nickel oxide nanoparticles application in biomethane production

Box-Behnken design and life cycle assessment for nickel oxide nanoparticles application in biomethane production

Biochar facilitates biofuel production through batch single-stage and two-stage digestion of grass silage and cattle slurry

Grass silage and cattle slurry are the most abundant feedstocks for biogas in an Irish context. This work describes how to optimize their biomethane yield. Hydrolysis and biomethane yields from co-digestion of grass silage and slurry were enhanced in a biochar-supplemented two-stage digestion process. Biochar addition at the optimal dosage of 10 g/L in batch two-stage digesters led to the highest methane yield of 253 L per kilogram (kg) volatile solid (VS), which was 24% higher than that from two-stage digesters without biochar supplementation. For a batch single-stage digester, the biomethane yields were lower than the two-stage but 10 g/L biochar addition led to an increase to 218 L/kg VS as compared to 198 L/kg VS for the group without biochar supplementation. Volatile fatty acid accumulation increased with the enhancement of biomethane production in the biochar-supplemented two-stage reactors. The addition of biochar in single-stage and two-stage anaerobic digesters presented positive effects on the electrochemical properties of the digester contents, reflected by the increased charge storage capacity, reduced solution resistance and improved digester content conductivity. The methane yields in two-stage anaerobic digestion were shown to be strongly correlated (R2 = 0.92) with the concentration of extracellular polymeric substances. This evidenced that the interlaced conductive network established by extracellular polymeric substances and biochar was essential for direct interspecies electron transfer and biomethane production. This study demonstrated that biochar-supplemented two-stage anaerobic digestion is an optimal route for energy recovery from grass silage and cattle slurry.

An Overview of Anaerobic Digestion of Agricultural By-Products and Food Waste for Biomethane Production

In a world facing increasing environmental and energy challenges, anaerobic digestion of agrifood by-products and food waste could contribute to the production of green energy while reducing greenhouse gas emissions into the atmosphere. Anaerobic digestion is a biological process capable of breaking down and stabilising organic matter in the absence of oxygen and converting it into a renewable source of energy, known as biogas. Biomethane production also enables the generation of electricity and produces digestate, a by-product of the digestion process that can be used as a soil conditioner or fertiliser. This review aims to highlight how substrate pretreatment, together with the optimisation of operating parameters, application of additives, recirculation of digestate and frequent feeding, can increase biogas production. An overview of the basics of the anaerobic digestion of agrifood by-products and food waste is provided, including feedstock characteristics (nutrient content, particle size and inhibitory compounds) and process parameters (process configuration, pH, temperature, total and volatile solids, total Kjeldahl nitrogen, ammonium, chemical oxygen demand, carbon/nitrogen ratio, retention time, organic loading rate, etc.). In addition, recent studies in the field of processes, equipment and pretreatments that can significantly improve the anaerobic digestion process of agricultural and food wastes were classified and discussed. Finally, the challenges and future perspectives of biogas production from the agrifood sector are addressed.

Microbial electrolysis cell assisted anaerobic digestion system boosted the methane production from polylactic acid by optimizing the methanogenesis pathway

Anaerobic digestion (AD) is a method for disposing of biodegradable plastics, which offers a solution to the worldwide plastic pollution. However, it is not yet relevant to the recycling of plastics due to its limits in reactive energetics and chemical kinetics. A microbial electrolytic cell-assisted anaerobic digestion system (MEC-AD) was used in this work to degrade polylactic acid, and various pretreatment techniques and applied voltages were examined to provide the greatest bio-methane production. Results showed that hydrothermal pretreatment is the most advantageous considering both the cost and efficiency. The methane output in the MEC-AD was greater, according to a further comparison of the methanogenic performance of both system from hydrothermally pretreated polylactic acid. The system produced the most methane when exerted a voltage of 0.3 V, and its incubation period was 0.6 times of shorter than that of the AD system. The methanogen responses for hydrogenotrophic methanogenesis in the MEC-AD system were significantly enriched as a result of the externally applied voltage. MEC-AD produces 1.17 times more net profit than AD system and has a greater energy recovery rate. This study investigated an economical method for treating polylactic acid and offered an innovative proposal for recycling plastic waste materials.

Role of biomethane to offset natural gas

The use of biomethane, produced through anaerobic digestion of organic waste, holds promise as an energy source for mitigating climate change. This study quantifies the technical potential of biomethane, considering neither socio-economic nor political constraints, and then compares it to worldwide natural gas use and imports. Furthermore, it calculates the potential emission reduction achieved by substituting natural gas with biomethane. We find that biomethane can offset 29% of natural gas use and two-thirds of natural gas net-imports worldwide. Considering the European energy crisis arising from the Russian-Ukrainian conflict, we analyze the potential for each European country to generate enough biomethane to decrease their reliance on imported Russian natural gas. Our estimates indicate that almost one-third of European countries, including the United Kingdom, France, Spain, Ireland, Slovenia, Romania, Greece, Sweden, and Portugal, have the potential to completely replace their natural gas imports from Russia by utilizing domestic biomethane production. Our study also evaluates how biomethane can reduce greenhouse gas emissions by substituting fossil natural gas, while considering methane leaks in both biomethane and natural gas supply chains and carbon emissions from fossil natural gas combustion. Our results indicate that replacing fossil natural gas with biomethane will decrease emissions from natural gas systems by 11%, equivalent to 1.1 Gt CO2-eq per year. These findings illustrate the potential of biomethane in reducing our dependence on fossil natural gas and mitigating its emissions.

Ruminal content biochar supplementation for enhanced biomethanation of rice straw: Focusing on biochar characterization and dose optimization

Anaerobic digestion (AD) of agricultural wastes is a promising approach for energy recovery and crop residue management. However, its recalcitrant chemical structure hinders microbial hydrolysis and reduces biomethane production under AD. Biochar supplementation has been proven to promote the digestibility and biomethanation of lignocellulosic substrates. Therefore, this study investigated the influence of different pyrolysis temperatures (450 °C, 550 °C, and 650 °C) on the physicochemical properties of biochar. Furthermore, the impact of ruminal content biochar supplementation (1 %, 2 %, and 3 %) on the AD of rice straw with rumen fluid as inoculum has been investigated. The ruminal content biochar (RUCB) supplemented reactors showed an increment in biomethane yield and the highest cumulative biomethane yield 243.11 mL/g volatile solids (VS)) was recorded at 2 % RUCB supplementation, followed by 227.12 mL/g VS at 1 % RUCB supplementation and 162.86 mL/g VS at 3 % RUCB supplementation (P > 0.05). Compared to the control reactors (128.68 mL/g VS), RUCB supplemented reactors exhibited 1.88-fold, 1.76-fold, and 1.26-fold increments in biomethane yield due to pH stabilization and facilitation of microbial biofilm formation on the biochar. The correlation analysis showed that biomethane production is positively correlated with VS reduction (R2 = 0.9852). This study proposed a potential strategy to utilize ruminal content waste as a feedstock for biochar production and its application in AD for accelerating the biomethanation of rice straw.

A comprehensive analysis of key factors influencing methane production from CO2 using microbial methanogenesis cells

With increasing attention on carbon capture and utilization (CCU) technologies for the conversion of CO2 into chemical products, microbial methanogenesis cells (MMCs) have been extensively studied over the past few decades for biomethane production. Using rapidly accumulating data for MMCs with varying configurations and operating conditions, a comprehensive analysis was conducted here to investigate the critical factors that influence methane production rates (MPR) in these systems. A comparison of MPR and set potentials or current densities showed weak linear relationships (R2 < 0.6, p < 0.05), indicating the significant contributions of other important factors impacting methane production. A non-quantitative analysis of these additional parameters indicated the potential importance of using metal catalysts for anode materials where oxygen evolution reaction occurs, while most previous MMC research focused more on cathode materials where the biocatalytic reaction occurs. The use of undefined mixed anaerobic cultures as inocula was found to be sufficient for producing high MPRs, as the electrochemical environment at the cathode provides a strong selective pressure to converge on desirable methanogenic cultures. Other operational parameters, such as catholyte pH control and CO2 supply methods, were also important factors impacting MPR in MMCs, indicating the cumulative impact of these various factors will require careful consideration in future research.

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.

PROSPECTS FOR THE PRODUCTION OF ADVANCED BIOFUELS IN UKRAINE

Perspective directions for the development of motor biofuels market in Ukraine are considered. It is shown that Ukraine has a significant potential for the production of liquid biofuels for the transport sector. Today, it is mainly biodiesel and bioethanol of the first generation, since the technologies for obtaining advanced biofuels from lignocellulosic feedstocks are not yet sufficiently developed in the country. However, as these technologies improve, one of directions for the development of motor biofuels market will be the expansion of production opportunities for second generation (advanced) biofuels with a significant share of their export to EU countries. Directive (EU) 2018/2001 on renewable energy sources (RED II) limits the share of 1st generation biofuels in achieving the goals for the consumption of renewable energy in transport. The share of such biofuels in a certain EU country can be no more than 1 % higher than the share of these biofuels in the gross final energy consumption of road and rail transport of that country in 2020, but no more than 7 %. For Ukraine, this means that the share of 1st generation biofuels in the final energy consumption in transport in 2030 cannot exceed 1.85 %, since in 2020 this indicator was 0.85 %. A possible option for solving this problem is to coordinate with the European Commission the issue of increasing the quota of 1st generation biofuels for Ukraine to 7 % in 2030, which is equivalent to the consumption of 503 ktoe/y. In the future, it seems appropriate to develop the production of advanced bioethanol from byproducts of grain corn cultivation as well as advanced biodiesel from oilseed energy crops grown on unused agricultural land. According to RED II, such biodiesel is not subject to restrictions on biofuels produced from food or feed crops. Production and consumption of biomethane is also a promising direction for the introduction of renewable energy in transport. It is shown that the total potential of biogas production in Ukraine is currently 8.16 Mtoe/y, of which a quarter can be allocated for the transport needs. By 2050, the production potential of biogas as a motor fuel may increase to 4.7 Mtoe/y, mainly due to the use of cover crops as feedstock to obtain biogas. Bibl. 21, Tab. 4.

Comments on the paper “Enhanced bio-methane and bio-hydrogen production using banana plant waste and sewage sludge through anaerobic co-digestion” by Jokhio et al., International Journal of Hydrogen Energy 48 (2023) 21360-21371

Comments on the paper “Enhanced bio-methane and bio-hydrogen production using banana plant waste and sewage sludge through anaerobic co-digestion” by Jokhio et al., International Journal of Hydrogen Energy 48 (2023) 21360-21371

Dynamic simulation and thermoeconomic analysis of a power to gas system

Power to gas technology is an innovative solution to promote the use of renewable energy technologies, also including e-fuels. This work presents a techno-economic analysis of a novel concept of a renewable power to gas plant. A 2.4 MW solid oxide electrolyzer fed by a 3.1 MW photovoltaic field is coupled with a biomethane production unit to produce synthetic methane by means of a 2.4 MW methanation unit. The hydrogen produced by the electrolyzer is used for the methanation reaction aiming at producing natural gas at net zero carbon emissions. The CO2 is obtained as a byproduct of the membrane separation in a biogas upgrading unit. The methanation unit and the electrolyzer models are developed in MatLab and integrated in TRNSYS to perform a dynamic simulation of all the components and the system as a whole. Dynamic simulation results show a 42% increase in the production of natural gas from renewable energy sources. The thermoeconomic analysis shows a remarkable primary energy saving index of 176% and a total amount of 896 tons of CO2 equivalent emissions saved. As expected, the critical point is the economic feasibility since the simple payback is 9 years in case local incentives and subsidies are considered. The parametric analysis on the photovoltaic capacity shows that the simple payback dramatically depends on such design parameter, varying from 6 years in the best case scenario to 92 years in the worst case scenario.

Enhanced anaerobic digestion of brewers’ spent grain: effect of inoculum, poultry manure application and iron (iii) chloride supplementation on biogas production and its kinetics

AbstractThe brewery industry generates a huge quantity of brewers’ spent grain (BSG) which can pose waste disposal and pollution problems. Anaerobic digestion of BSG, a recalcitrant lignocellulosic waste, is slow but can be enhanced by bioaugmentation, biostimulation and co-digestion to obtain a higher biogas yield. Hence, the effect of inoculum from brewery wastewater sludge (BWWS), iron (III) chloride (FeCl3) and co-digestion with poultry manure (PM) on the production of biogas from BSG was investigated. Cumulative biogas and biomethane yields of 588.19 NL/kgVS and 400.34 NLCH4/kgVS, respectively, were obtained from a slurry consisting of a blend of 60% BSG and 40% PM plus 15 mg L-1 FeCl3 in BWWS, after 30 day retention time at 37 oC. However, mono-digestion of BSG in only water yielded 402.17 NLbiogas/kgVS and 262.86 NLCH4/kgVS. The synergistic effects of inoculum from BWWS, FeCl3 and poultry manure on anaerobic digestion of BSG resulted in 46% and 52% increases in biogas and methane yields, respectively, compared with BSG mono-digestion. The biogas and biomethane production kinetics were well described by the dual pooled first order, logistic and modified Gompertz models.

Co‐production of biobutanol and biomethane from distillers' grain waste by an integrated process

AbstractBackgroundDistillers' grain waste (DGW) is the main by‐product in the Baijiu‐making process and its management remains a great challenge for the Baijiu industry. To address this issue, an integrated biobutanol and biomethane production process was established to obtain valuable products from DGW and reduce environmental pollution.ResultsIn the integrated process, DGW was hydrolyzed and detoxified to produce biobutanol, while the distillery waste derived from solvent extraction process was used for biomethane fermentation. After the optimization of overliming detoxification of DGW hydrolysate by artificial neural network and genetic algorithm, totals of 10.65 ± 0.07 g L−1 butanol and 4.51 ± 0.21 g L−1 isopropanol were attained with negligible amounts of acetone and ethanol (i.e. 0.14 ± 0.00 and 0.52 ± 0.06 g L−1, respectively). Anaerobic digestion of the distillery waste was efficient, and the chemical oxygen demand removal rate approached 92.3 ± 0.1% with a methane yield of 167.8 ± 1.2 mL g−1 TCODremoved. Moreover, the anaerobic digestion effluent could be recycled as a potential substitute for process water in biobutanol fermentation without having any negative effect on enzymatic hydrolysis of DGW, and the butanol production also reached 8.19 ± 0.29 g L−1.ConclusionThe present study provides a new idea for comprehensive utilization of DGW towards energy and resource recovery, without secondary pollution. © 2023 Society of Chemical Industry.

Production of Biogas and Biomethane as Renewable Energy Sources: A Review

An economy based on renewable energy sources is the hallmark of responsible companies. Climate policy and energy crisis commitments have led to a search for alternative ways to produce energy. Bioenergy is considered the most consistent renewable energy source due to its economic and environmental benefits. Biogas and biomethane are promising forms of renewable energy derived from widely available evergreen raw materials. Agricultural, animal, industrial and food wastes are excellent substrates used to produce clean and sustainable energy in a circular economy context. Their conversion into biogas and biomethane through the anaerobic digestion (AD) process is an efficient solution to the treatment of waste of different origins. The production and use of biomethane favor important environmental advantages, such as the reduction in greenhouse gas emissions compared with those deriving from the use of conventional fossil fuels. This review would like to highlight modern trends and approaches to evaluate processes and strategies to control biogas and biomethane production. In particular, the use of livestock waste for the digestion process and the reuse of the by-product as fertilizer, as well as the potential development of biogas and biomethane as prospects for the improvement and optimization of renewable energy sources, are discussed.

Recovery of Energy and Carbon Dioxide from Craft Brewery Wastes for Onsite Use

Interest in craft beers is increasing worldwide due to their flavor and variety. However, craft breweries have high water, energy, and carbon dioxide (CO2) demands and generate large quantities of high-strength waste and greenhouse gases. While many large breweries recover energy using anaerobic digestion (AD) and recapture CO2 from beer fermentation, little is known about the economic feasibility of applying these technologies at the scale of small craft breweries. In addition, compounds in hops (Humulus lupulus), which are commonly added to craft beer to provide a bitter or “hoppy” flavor, have been shown to adversely affect anaerobic microbes in ruminant studies. In this study, biochemical methane potential (BMP) assays and anaerobic sequencing batch reactor (ASBR) studies were used to investigate biomethane production from high-strength craft brewery waste, with and without hop addition. A spreadsheet tool was developed to evaluate the economic feasibility of bioenergy and CO2 recovery depending on the brewery’s location, production volume, waste management, CO2 requirement, energy costs, and hop waste addition. The results showed that co-digestion of yeast waste with 20% hops (based on chemical oxygen demand (COD)) resulted in slightly lower methane yields compared with mono-digestion of yeast; however, it did not significantly impact the economic feasibility of AD in craft breweries. The use of AD and CO2 recovery was found to be economically feasible if the brewery’s annual beer production is &gt;50,000 barrels/year.

Recycling of catering waste for sequential production of biohydrogen and biomethane; pre-treatments, batch, and continuous mode studies

Dark fermentation has emerged as a sustainable bio-based economy for bio-fuels production in accord with “carbon neutrality”. Herein, catering waste was collected, pre-treated with a series of multilevel (acidic, alkaline, Triton X100, ultrasonication, and microwave radiation) pathways, and employed as substrates to inspect their characteristics on two-stage mesophilic biohydrogen/biomethane production process through batch assays under initial pH of 6.5, and 7.5, respectively. The findings revealed that the optimized pre-treated catering waste (CW) with Triton X-100 recorded the highest biohydrogen, and biomethane production yield of 5.9 mL/g VS added (BHP of 368.5 mL), and 17.7 ± 26.8 mL/g VS (BMP 1108.5 mL), at 37 °C, respectively. Overall, the kinetic data was strongly matched with the Gompertz equation (R2 = 0.92–0.99). Afterward, the pre-treated Triton X-100-CW was introduced into a second series of continuous experiments (continuously stirred tank reactors) for sequential production of biohydrogen/ biomethane. An average yield of biohydrogen and biomethane production of 22.24 ± 2.29 mL/g VS, and 98.7 ± 10.4 mL/g VS was accomplished at hydraulic retention time (HRT), and organic loading rate (OLR) of 1.0 day, 91.5 gCOD/L.day and 10.0 days, 7.2 gCOD/L.day, respectively. Economically, the configured system displays a total energy yield of 1.634 KWh/KgVS, and the inspected 1600 kg CW produces about 2614.41 KW/day. As such, the present work broadens a salience pattern for scalable upcycling of CW organic constituent stream into biohydrogen/biomethane for potential applications in the energy sector.

A biorefinery model for the production of oil and biomethane using castor plants

AbstractCastor (Ricinus communis L.) is an important oilseed crop worldwide whose inedible oil is widely used in the industrial, pharmaceutical, and agricultural sectors. Castor plants show high conversion potential for use as biorefining feedstocks. The present study was conducted to investigate the effects of two nitrogen fertilization levels (0 and 120 kg N ha−1) on seed and oil yield. From a biorefinery perspective, the residual biomass of seed processing was analyzed in terms of fiber composition and biomethane production carrying out a biological pretreatment using two white‐rot fungi (Pleurotus ostreatus and Irpex lacteus). Nitrogen fertilization resulted in an increase in seed and oil yields and a difference in capsule husk composition. Fungal pretreatment of capsule husks showed promising effects on anaerobic digestion, increasing the biomethane yield compared to untreated biomass. The highest lignin degradation and the lowest cellulose loss during pretreatment were obtained with I. lacteus, and this fungal pretreatment resulted in the highest biomethane yield (103.2 NmL g−1 volatile solids) for the fertilized biomass.

Sweet Sorghum as a Potential Fallow Crop in Sugarcane Farming for Biomethane Production in Queensland, Australia

Biogas from lignocellulosic feedstock is a promising energy source for decentralized renewable electricity, heat, and/or vehicle fuel generation. However, the selection of a suitable energy crop should be based on several factors such as biomass yields and characteristics or biogas yields and economic returns if used in biorefineries. Furthermore, the food-to-fuel conflict for the use of a specific energy crop must be mitigated through smart cropping techniques. In this study, the potential use of sweet sorghum as an energy crop grown during the fallow periods of sugarcane cultivation was evaluated. Nine sweet sorghum cultivars were grown on sandy loam soil during September 2020 in North Queensland, Australia. The overall results showed that the crop maturity had a profound influence on chemical composition and biomass yields. Further, the total insoluble and soluble sugar yields varied among the tested cultivars and were dependent on plant height and chemical composition. The biomass yields ranged from 46.9 to 82.3 tonnes/hectare (t/ha) in terms of the wet weight (w/w) of the tested cultivars, with the SE-81 cultivar registering the highest biomass yield per hectare. The gross energy production was determined based on the chemical composition and methane yields. Biochemical methane potential (BMP) studies in batch experiments at 37 °C showed that methane yields of 175 to 227.91 NmL CH4/gVSadded were obtained from the tested cultivars. The maximum methane yield of 227.91 NmL CH4/gVSadded was obtained for cultivar SE-35. However, SE-81 produced the highest methane yields on a per hectare basis (3059.18 Nm3 CH4/ha). This is equivalent to a gross energy value of 761.74 MWh/year or compressed biomethane (BioCNG) as a vehicle fuel sufficient for 95 passenger cars travelling at 10,000 km per annum. Overall, this study demonstrated that sweet sorghum is a potential energy crop for biogas production that could be cultivated during the fallow period of sugarcane cultivation in Queensland.