Renewable Natural Gas Research Articles

Policy impact on economic and environmental sustainability of anaerobic digestion: Industrial case study Insights.

This paper thoroughly examines how policy incentives impact the economic and environmental sustainability of anaerobic digestion (AD) systems. It uses techno-economic and life cycle analyses, along with real industry data, to explore the entire AD process-from feedstock acceptance to digestate disposal. It evaluates the effects of various U.S. policy crediting programs on the economic viability of different AD pathways for treating sewage sludge and food waste. Tipping fees are identified as the primary driver of profitability, while policy credits play a crucial role in enhancing economic feasibility, particularly for renewable natural gas production. However, future regulatory changes could reshape this economic landscape. All AD pathways are found to significantly reduce greenhouse gas emissions, though economic outcomes are highly sensitive to digestate disposal costs and feedstock tipping fees. Co-digestion with food waste is proposed as a strategy to reduce dependence on policy credits and improve long-term economic stability.

Opportunities and Challenges of Fuel Cell Electric Vehicle-to-Grid (V2G) Integration

This paper presents an overview of the status and prospects of fuel cell electric vehicles (FC-EVs) for grid integration. In recent years, renewable energy has been explored on every front to extend the use of fossil fuels. Advanced technologies involving wind and solar energy, electric vehicles, and vehicle-to-everything (V2X) are becoming more popular for grid support. With recent developments in solid oxide fuel cell electric vehicles (SOFC-EVs), a more flexible fuel option than traditional proton-exchange membrane fuel cell electric vehicles (PEMFC-EVs), the potential for vehicle-to-grid (V2G)’s implementation is promising. Specifically, SOFC-EVs can utilize renewable biofuels or natural gas and, thus, they are not limited to pure hydrogen fuel only. This opens the opportunity for V2G’s implementation by using biofuels or readily piped natural gas at home or at charging stations. This review paper will discuss current V2G technologies and, importantly, compare battery electric vehicles (BEVs) to SOFC-EVs for V2G’s implementation and their impacts.

The Role of Low-Carbon Fuels and Carbon Capture in Decarbonizing the U.S. Clinker Manufacturing for Cement Production: CO2 Emissions Reduction Potentials

Low-carbon fuels, feedstocks, and energy sources can play a vital role in the decarbonization of clinker production in cement manufacturing. Fuel switching with renewable natural gas, green hydrogen, and biomass can provide a low-carbon energy source for the high-temperature process heat during the pyroprocessing steps of clinker production. However, up to 60% of CO2 emissions from clinker production are attributable to process-related CO2 emissions, which will need the simultaneous implementation of other decarbonization technologies, such as carbon capture. To evaluate the potential of fuel switching and carbon capture technologies in decarbonizing the cement industry, a study of the facility-level CO2 emissions is necessary. This study evaluates the potential for using a single low-carbon fuel as an energy source in clinker production for cement manufacturing compared to conventional clinker production (which uses a range of fuel mixes). In addition, conventional carbon capture (operated with natural gas-based steam for solvent regeneration) and electrified carbon capture configurations were designed and assessed for net-zero emission targets. Carbon emissions reductions with and without biogenic emissions credits were analyzed to ascertain their impact on the overall carbon accounting. Results show that carbon emissions intensity of cement can vary from 571 to 784 kgCO2eq/metric ton of cement without carbon capture and from 166.33 to 438.66 kgCO2eq/metric ton of cement with carbon capture. We find that when biogenic carbon credits are considered, cement production with a sustainably grown biomass as fuel source coupled with conventional carbon capture can lead to a net-negative emission cement (−271 kgCO2eq/metric ton of cement), outperforming an electrified capture design (35 kgCO2eq/metric ton of cement). The carbon accounting for the Scope 1, 2, and biogenic emissions conducted in this study is aimed at helping researchers and industry partners in the cement and concrete sector make an informed decision on the choice of fuel and decarbonization strategy to adopt.

Unlocking Potential for Low-Carbon Hydrogen Production from U.S. Natural Gas Resources.

Hydrogen will potentially play a key role while transitioning to a net-zero economy. This study addresses resource, environmental, economic, policy, and societal issues related to low-carbon hydrogen production by steam methane reforming with carbon capture and storage in Wyoming and other natural-gas-rich states. For low-carbon hydrogen produced from natural gas and electricity supplies and which stores CO2 in saline reservoirs in Wyoming, the levelized cost of hydrogen (LCOH) ranges from $1.62-2.00/kg H2, and the life cycle emissions range from 3.85-5.74 kg CO2-eq/kg H2. If claimed, the 45Q tax credit decreases the LCOH by 19%. Although the supplies of renewable natural gas feedstock and zero- or low-carbon electricity can lower the carbon footprint to make hydrogen projects qualified for the 45V tax credit, the 45Q tax credit is still a stronger economic incentive. To reduce the supply cost, a hydrogen cluster can be developed in the state by leveraging the colocation and coavailability of multiple natural resources and transport infrastructure. Developing a hydrogen cluster can directly create several thousand construction jobs and several hundred permanent jobs in Wyoming. Low-carbon hydrogen production can also be scaled up in other states across the nation.

Methanothermobacter thermautotrophicus and Alternative Methanogens: Archaea-Based Production.

Methanogenic archaea convert bacterial fermentation intermediates from the decomposition of organic material into methane. This process has relevance in the global carbon cycle and finds application in anthropogenic processes, such as wastewater treatment and anaerobic digestion. Furthermore, methanogenic archaea that utilize hydrogen and carbon dioxide as substrates are being employed as biocatalysts for the biomethanation step of power-to-gas technology. This technology converts hydrogen from water electrolysis and carbon dioxide into renewable natural gas (i.e., methane). The application of methanogenic archaea in bioproduction beyond methane has been demonstrated in only a few instances and is limited to mesophilic species for which genetic engineering tools are available. In this chapter, we discuss recent developments for those existing genetically tractable systems and the inclusion of novel genetic tools for thermophilic methanogenic species. We then give an overview of recombinant bioproduction with mesophilic methanogenic archaea and thermophilic non-methanogenic microbes. This is the basis for discussing putative products with thermophilic methanogenic archaea, specifically the species Methanothermobacter thermautotrophicus. We give estimates of potential conversion efficiencies for those putative products based on a genome-scale metabolic model for M. thermautotrophicus.

Power system planning in the energy transition era: the case of Vietnam's power development plan 8

ABSTRACT This review examines Vietnam's eighth Power Development Plan (PDP8), analyzing how it reveals tensions between traditional energy planning concepts and emerging realities. PDP8 aimed to balance renewable energy and natural gas priorities amidst Vietnam's rapidly changing energy landscape. The planning process struggled to incorporate uncertainties like technology cost declines and global energy crises. Although following a conventional optimization approach, PDP8 underwent repeated delays and pivots, pointing to misalignment between rational planning ideals and implementation constraints. The case study highlights the limitations of ‘plan to build’ methods focused on rigid engineering blueprints. Instead, Vietnam's energy transition requires strategic approaches that embrace flexibility and scenario analysis. Based on years of participative observation, two interview surveys, and extensive corpus analysis, the review traces PDP8's evolution towards more open-ended strategies. While still detailing infrastructure projects, PDP8 defines adaptive implementation mechanisms and conditional goals dependent on external finance. This shift from project lists to navigational thinking illustrates the need for energy planning to incorporate uncertainty and maintain the capacity to adjust. PDP8 represents a transitional compromise between traditional ten-year planning and emerging ‘plan to drive’ concepts focused on navigating change with annual updates to the Plan.

Ex-situ single-culture biomethanation operated in trickle-bed configuration: Microbial H2 kinetics and stoichiometry for biogas conversion into renewable natural gas

Biomethanation converts carbon dioxide (CO2) emissions into renewable natural gas (RNG) using mixed microbial cultures enriched with hydrogenotrophic archaea. This study examines the performance of a single methanogenic archaeon converting biogas with added hydrogen (H2) into methane (CH4) using a trickle-bed bioreactor with enhanced gas–liquid mass transport. The process in continuous operation followed the theoretical reaction of hydrogenotrophic methanogenesis (CO2 + 4 H2 → CH4 + 2 H2O), producing RNG with over 99 % CH4 and more than 0.9 H2 conversion efficiency. The Monod constants of H2 uptake were experimentally determined using kinetic modelling. Also, a dimensionless parameter was used to quantify the ratio between the H2 mass transfer rate and the maximum attainable H2 consumption rate. Single-culture biomethanation averts the formation of secondary metabolites and bicarbonate buffer interferences, resulting in lower demands for H2 than mixed-culture biomethanation.

Developing hydrogen energy hubs: The role of H2 prices, wind power and infrastructure investments in Northern Norway

Hydrogen is seen as a key energy carrier to reduce CO2 emissions. Two main production options for hydrogen with low CO2 intensity are water electrolysis and natural gas reforming with Carbon Capture and Storage, known as green and blue hydrogen. Northern Norway has a surplus of renewable energy and natural gas availability from the Barents Sea, which can be used to produce hydrogen. However, exports are challenging due to the large distances to markets and lack of energy infrastructure. This study explores the profitability of hydrogen exports from this Arctic region. It considers necessary investments in hydrogen technology and capacity expansions of wind farms and the power grid. Various scenarios are investigated with different assumptions for investment decisions. The critical question is how exogenous factors shape future regional hydrogen production and export. The results show that production for global export may be profitable above 90 €/MWh, excluding costs for storage and transport, with blue hydrogen being cheaper than green. Depending on the assumptions, a combination of liquid hydrogen and ammonia export might be optimal for seaborne transport. Exports to Sweden can be profitable at prices above 60 €/MWh, transported by pipelines. Expanding power generation capacity can be crucial, and electricity and hydrogen exports are unlikely to co-exist.

Low‐carbon economic schedule of the H2DRI‐EAF steel plant integrated with a power‐to‐hydrogen system driven by blue hydrogen and green hydrogen

AbstractHydrogen direct reduction iron coupled with electronic arc furnace (H2DRI‐EAF) technology, as an important technology for decarbonisation in the iron and steel industry, has the advantages of high electrification and low carbon emissions. However, the large demand for hydrogen in this technology relies significantly on the production of electrolytic hydrogen, leading to a substantial increase in power consumption in the steel production process. Moreover, the use of an unclean power source in electrolytic hydrogen production leads to increases in indirect carbon emissions, reducing the low‐carbon attributes of the technology. This study investigates the integrated flexible operation mode of a steel plant. An illustrating method is utilised for modelling the entire steel production process and power to hydrogen (PtH2) process in detail for the H2DRI‐EAF steel plant, which includes natural gas, photovoltaic, wind power self‐provided power plants, and carbon capture and storage (CCS) systems. A mixed integer linear programming (MILP) model is developed for the comprehensive scheduling of the steel mill. The results of the case studies indicate that by reliably integrating the production of renewable energy and natural gas power plants, the PtH2 system can fully consume the renewable energy output while ensuring the smooth progress of steel production and maximising the reduction of carbon emissions from hydrogen production and the total cost of steel production.

Impacts of material characteristics on the anaerobic digestion kinetics and biomethane potential of American bourbon and whiskey stillage

Stillage of American whiskey (e.g., bourbon) manufacturing is an abundant byproduct that is distinguished from fuel ethanol and malt whisky stillage materials by its highly inconsistent nature due to variability in mash bill composition. The impact of stillage physicochemical characteristics on biomethane production through anaerobic digestion was assessed by characterizing American whiskey stillage samples before batch biochemical methane potential tests of whole stillage. A maximum methane yield of 419 Nml CH4/g VS was obtained under food to microbe ratio (F: M) of 0.5 and organic loading rate (OLR) of 10 g VS/L while digester instability was noted under F: M ratios exceeding 0.5 under batch production. Methane production was significantly influenced by the mash bill composition with lowest methane yields obtained with higher rye content (rye whiskey) and highest methane yields obtained with higher corn content (bourbon or corn whiskey). A multiple linear regression model including C, P, N, and Na was able to accurately describe the methane yield (R2 = 0.93). This study provides valuable insights to aid the design of anaerobic digesters generating renewable natural gas from heterogeneous American whiskey stillage.

Wastewater hydrogen nexus (WwHeN): Greening the wastewater industry via integration with the hydrogen economy✰

As industries rally toward achieving net zero emissions, hydrogen and hydrogen-based fuels are emerging as key players in decarbonization efforts. Although the primary technology for producing renewable natural gas has been well implemented in the wastewater industry, the “decarbonization based goal setting” is trailing. This perspective assimilates existing literature presented in other contexts to highlight the need for framing the decarbonization dialog by using green hydrogen as a potential pathway for the wastewater industry. Specifically, we note the importance of (a) developing the decarbonization or net zero focus in the wastewater industry, and (b) colocating the wastewater industry with hydrogen production facilities. We also delve into technological, cost, and operational considerations to understand the readiness level of key stakeholders to identify future research and development opportunities for the wastewater hydrogen nexus.

National Greenhouse Gas Emission Reduction Potential from Adopting Anaerobic Digestion on Large-Scale Dairy Farms in the United States.

Waste-to-energy systems can provide a functional demonstration of the economic and environmental benefits of circularity, innovation, and reimagining existing systems. This study offers a robust quantification of the greenhouse gas (GHG) emission reduction potential of the adoption of anaerobic digestion (AD) technology on applicable large-scale dairy farms in the contiguous United States. GHG reduction estimates were developed through a robust life cycle modeling framework paired with sensitivity and uncertainty analyses. Twenty dairy configurations were modeled to capture important differences in housing and manure management practices, applicable AD technologies, regional climates, storage cleanout schedules, and methods of land application. Monte Carlo results for the 90% confidence interval illustrate the potential for AD adoption to reduce GHG emissions from the large-scale dairy industry by 2.45-3.52 MMT of CO2-eq per year considering biogas use only in renewable natural gas programs and as much as 4.53-6.46 MMT of CO2-eq per year with combined heat and power as an additional biogas use case. At the farm level, AD technology may reduce GHG emissions from manure management systems by 58.1-79.8% depending on the region. Discussion focuses on regional differences in GHG emissions from manure management strategies and the challenges and opportunities surrounding AD adoption.

Technology assessment for the transition to a renewable electric grid

To reduce carbon emissions, generation of electricity from combustion systems is being replaced by renewable resources. However, the most abundant renewable sources – solar and wind – are not dispatchable, vary diurnally and are subject to intermittency, and produce electricity at times in excess of demand (excess production). To manage this variability and capture the excess renewable energy, energy storage technologies are being developed and deployed such as battery energy storage (BES), hydrogen production with electrolyzers (ELY) paired with hydrogen energy storage (HES) and fuel cells (FCs), and renewable natural gas (RNG) production. While BES may be better suited for short duration storage, hydrogen is suited for long duration storage and RNG can decarbonize the natural gas system. California Senate Bill 100 (SB100) sets a goal that all retail electricity sold in the State must be sourced from renewable and zero-carbon resources by 2045, raising the questions of which set of technologies and in what proportion are required to meet the 2045 target in the required timeframe as well as the role of the natural gas infrastructure, if any. To address these questions, this study combines electric grid dispatch modeling and optimization to identify the energy storage and dispatchable technologies in 5-year increments from 2030 to 2045 required to transition from a 60% renewable electric grid in 2035 to a 100% renewable electric grid in 2045. The results show that, by utilizing the established natural gas system to store and transmit hydrogen and RNG, the deployment of battery energy storage is dramatically reduced. The required capacity for BES in 2045, for example, is 40 times lower by leveraging the natural gas infrastructure with a concomitant reduction in cost and associated challenges to transform the electric grid.

Bibliometric Analysis of Renewable Natural Gas (Biomethane) and Overview of Application in Brazil

Bibliometric Analysis of Renewable Natural Gas (Biomethane) and Overview of Application in Brazil

Optimizing Economic Dispatch with Renewable Energy and Natural Gas Using Fractional-Order Fish Migration Algorithm

This work presents a model for solving the Economic-Environmental Dispatch (EED) challenge, which addresses the integration of thermal, renewable energy schemes, and natural gas (NG) units, that consider both toxin emission and fuel costs as its primary objectives. Three cases are examined using the IEEE 30-bus system, where thermal units (TUs) are replaced with NGs to minimize toxin emissions and fuel costs. The system constraints include equality and inequality conditions. A detailed modeling of NGs is performed, which also incorporates the pressure pipelines and the flow velocity of gas as procedure limitations. To obtain Pareto optimal solutions for fuel costs and emissions, three optimization algorithms, namely Fractional-Order Fish Migration Optimization (FOFMO), Coati Optimization Algorithm (COA), and Non-Dominated Sorting Genetic Algorithm (NSGA-II) are employed. Three cases are investigated to validate the effectiveness of the proposed model when applied to the IEEE 30-bus system with the integration of renewable energy sources (RESs) and natural gas units. The results from Case III, where NGs are installed in place of two thermal units (TUs), demonstrate that the economic dispatching approach presented in this study significantly reduces emission levels to 0.4232 t/h and achieves a lower fuel cost of 796.478 USD/MWh. Furthermore, the findings indicate that FOFMO outperforms COA and NSGA-II in effectively addressing the EED problem.

Geochemical impact of biomethane and natural gas blend injection in deep aquifer storage

Biomethane is one of the main renewable gases available today to offset fossil gas and decarbonize the energy system. The EU is seeking to rapidly replace part of the natural gas usually stored in deep saline aquifers by biomethane which contains up to 10000 ppm of O2. This study presents for the first-time assessment of deep aquifers’ resilience to biomethane and natural gas blend injection into two sandstone reservoirs with different mineral paragenesis from the Paris Basin (France). Multiphase reactive transport modeling allowed to evaluate changes in gas and water quality, mineralogy and moreover, to identify major resilience properties of storage facilities necessary to buffer the oxygen reactivity and induced acidification coming from gas–water–rock interactions. In the presence of pyrite, the injected oxygen is consumed during pyrite oxidation and contributes to the acidification of the formation water close to the injection point. However, the injection of 1% mole fraction of CO2(g) contained in the gas blend is found to be the main acidification factor. The analysis of reservoir resilience showed three protection levels of pH buffering capacity, which can effectively mitigate an increase in oxygen content up to 1000 ppm: (i) calcite dissolution, (ii) plagioclase and clay dissolution and (iii) clay sorption capacity. Models predict that the gas blend injection could induce minimal but long-term change in the mineralogy without significantly impacting the global porosity. Overall, both sandstones can preserve the quality of the gas plume despite partial CO2(g) exsolution induced by the geochemical perturbation of the formations. The developed models will be used as a basis for assessment of renewable natural gas storage facilities in the long-term.

Analysis of Gas Characteristics Produced in an Updraft Type Gasification Reactor with Various Gas Agent Flow Rates

Gasification is a process of converting compounds containing carbon to change both liquid and solid materials into combustible gaseous fuel (CO, H2, CO2, CH4 and H2O) through a combustion process with a limited air supply, namely 20-40% of the air stoichiometry. The aim of this research is to obtain syngas that is renewable natural gas quality. The gasification reactor used in this research has a reactor diameter of 600 mm and a reactor height of 1500 mm. Research on the characterization of the gasification process in updraft gasifiers made from horse manure using the thermal decomposition method where the gas agent used is air. Variations in the flow rate of the gas agent used are 10, 15, 20 and 30 lt/minute. The results of the research that has been carried out show that the greater the flow rate of the gas agent, the CO gas levels will increase with an average increase of 15%, however the increase in CO gas is followed by a decrease in CH4 gas levels, namely an average of 13%. Likewise, CO2 gas levels decreased by an average of 14%.

Sustainability and environmental impact in the LNG value chain: Current trends and future opportunities

The liquefied natural gas (LNG) industry plays a crucial role in the global energy landscape, offering a cleaner alternative to traditional fossil fuels. However, the LNG value chain presents environmental challenges that must be addressed to ensure long-term sustainability. This paper examines current trends and future opportunities for enhancing sustainability and reducing environmental impact across the LNG value chain. The LNG value chain comprises several stages, including natural gas extraction, liquefaction, transportation, regasification, and distribution. Each stage presents unique sustainability challenges, such as methane emissions during extraction and transportation, energy-intensive liquefaction processes, and the carbon footprint of regasification and distribution. Current trends in the LNG industry focus on mitigating these challenges through various strategies. These include the adoption of advanced technologies for methane detection and reduction, the use of renewable energy sources for liquefaction, and the implementation of efficient regasification and distribution practices. Additionally, there is a growing emphasis on stakeholder engagement, transparency, and reporting to enhance sustainability performance across the value chain. Future opportunities for improving sustainability in the LNG value chain lie in the continued development and deployment of innovative technologies. These include carbon capture and storage (CCS) technologies to reduce emissions, the use of renewable natural gas (RNG) as a feedstock, and the integration of LNG with renewable energy sources to create hybrid energy systems. Addressing sustainability and environmental impact in the LNG value chain requires collaboration among industry stakeholders, governments, and regulatory bodies. By implementing best practices, embracing innovation, and prioritizing sustainability, the LNG industry can continue to play a vital role in the transition to a cleaner and more sustainable energy future.

Characteristics of hydrogen enrichment on RNG combustion under various engine speeds in a retrofitted gas engine

Renewable natural gas (RNG) is attractive for energy policy goals in the world. A regional system is designed to explore RNG combustion for power generation in localities. Generally, 50 % methane (CH4) and 50 % carbon dioxide (CO2) in volume are utilized to represent RNG for investigations. However, CO2 reduces the burning rate and narrows the flammability limits, thus decreasing the engine thermal efficiency. Therefore, how to increase the thermal efficiency of RNG combustion through adding H2 or changing engine speed is the main task here. This study investigates a port fuel injection (PFI) engine fueled with hydrogen (H2) blended into the RNG. In order to obtain the higher efficiency, the effect of engine speed on combustion characteristics should be clarified as well as H2 influence demonstrated. Therefore, 1500, 2000 and 2500 revolutions per minute (rpm) of engine speed were tested. When H2 was added, the volume percentage changed from 5 % to 20 % by keeping the volume ratio of CH4 and CO2 at 1:1. Finally, combustion characteristics of CH4, CH4+CO2 and CH4+CO2+H2 were compared and discussed. Results showed that compared with H2, engine speed could only increase the efficiency slightly. “Arched” and “fish-hook” curves are fitted respectively to select the optimal working region. Through cylinder pressure analysis, engine speed could enlarge the Pmax only at some certain but increase coefficient of variation (COV) gradually. However, H2 increases Pmax but decreases COV significantly. Moreover, NOx decreases gradually with engine speed owing to the short reaction duration in combustion. However, NOx increases again with higher H2 concentration. Among the current conditions, for higher efficiency and lower NOx, three conditions are finally selected to be recommended for running.

Techno‐economic and life cycle analysis of renewable natural gas derived from anaerobic digestion of grassy biomass: A US Corn Belt watershed case study

AbstractRestoring native grassland vegetation can substantially improve ecosystem service outcomes from agricultural watersheds, but profitable pathways are needed to incentivize conversion from conventional crops. Given growing demand for renewable energy, using grassy biomass to produce biofuels provides a potential solution. We assessed the techno‐economic feasibility and life cycle outcomes of a “grass‐to‐gas” pathway that includes harvesting grassy (lignocellulosic) biomass for renewable natural gas (RNG) production through anaerobic digestion (AD), expanding on previous research that quantified ecosystem service and landowner financial outcomes of simulated grassland restoration in the Grand River Basin of Iowa and Missouri, United States. We found that the amount of RNG produced through AD of grassy biomass ranged 0.12–45.04 million gigajoules (GJ), and the net present value (NPV) of the RNG ranged −$97 to $422 million, depending on the combination of land use, productivity, and environmental credit scenarios. Positive NPVs are achieved with environmental credits for replacement of synthetic agricultural inputs with digestate and clean fuel production (e.g., USEPA D3 Renewable Identification Number, California Low Carbon Fuel Standard). Producing RNG from grassy biomass emits 15.1 g CO2‐eq/MJ, which compares favorably to the fossil natural gas value of 61.1 g CO2‐eq/MJ and exceeds the US Environmental Protection Agency's requirement for cellulosic biofuel. Overall, this study demonstrates opportunities and limitations to using grassy biomass from restored grasslands for sustainable RNG production.