Biogas upgrading to biomethane as a local source of renewable energy to power light marine transport: Profitability analysis for the county of Cornwall

Optimizing biogas methanation over nickel supported on ceria-alumina catalyst: Towards CO2-rich biomass utilization for a negative emissions society

Biogas methanation emerges as a prominent technology for converting biogas into biomethane in a single step. Furthermore, this technology can be implemented at biogas plant locations, supporting local economies and reducing dependence on large energy producers. However, there is a lack of comprehensive studies on biogas methanation, particularly regarding the technical optimization of operational parameters and the profitability analysis of the overall process. To address this gap, our study represents a seminal work on the technical optimization of biogas methanation obtaining an empirical model to predict the performance of biogas methanation. We investigate the influence of operational parameters, such as reaction temperature, H2/CO2 ratio, space velocity, and CO2 share in the biogas stream through an experimental design. Based on previous research we selected a nickel supported on ceria-alumina catalyst; being nickel a benchmark system for methanation process such selection permits a reliable data extrapolation to commercial units. We showcase the remarkable impact of studied key operation parameters, being the temperature, the most critical factor affecting the reaction performance (ca. 2 to 5 times higher than the second most influencing parameter). The impact of the H2/CO2 ratio is also noticeable. The response surfaces and contour maps suggest that a temperature between 350 and 450 °C and an H2/CO2 ratio between 2.5 and 3.2 optimize the reaction performance. Further experimental tests were performed for model validation and optimization leading to a reliable predictive model. Overall, this study provides validated equations for technology scaling-up and techno-economic analysis, thus representing a step ahead towards real-world applications for bio-methane production.

Economic assessment for vegetable waste valorization through the biogas-biomethane chain in Italy with a circular economy approach

The current geo-political framework and the environmental concern about pollution and global warming are leading Europe to rethink its energy production, moving forward to the incentivization the renewable energy market. In this scenario, the use of waste from the agri-food sector shows a huge potentiality to enhance the transition in line with the circular economy principles. Biogas production represents an environmental friendly strategy to successfully recover large amounts of waste and by-products to produce renewable energy. Furthermore, in light of the rising need of green biofuels, biogas can be converted into biomethane, allowing the implementation of a full circular model. The objective of this paper is to perform an economic assessment to evaluate whether the upgrading of an existing biogas plant, in which the diet includes also vegetable waste from a plant producing frozen vegetables, could be profitable considering different scenarios, to reach a sustainable circular model. The analysis will be conducted through the Discounted Cash Flow method, considering four main indexes: NPV, DPBT, IRR, and PI. The results highlight the unprofitability of the biogas-biomethane chain if the upgrading system is performed maintaining the same characteristics of the starting plant. On the other hand, if changes in the digester's diet occur, the investment becomes immediately profitable in the considered time-span. The circular economy model is not completely accomplished, as profitability can only be reached if silage maize is partially kept as feedstock. Moreover, the conversion of the plant is not economically feasible if an adequate subsidy is not provided. The economic assessment of the upgrading system for biogas to biomethane is an essential element to be provided to the agribusiness entrepreneurs, as they need all the relevant economic aspects to decide to invest and adopt this solution to establish an innovative circular business model in agriculture.

The Maritime Sector and Its Problematic Decarbonization: A Systematic Review of the Contribution of Alternative Fuels

The present study seeks to select the most important articles and reviews from the Web of Science database that approached alternative fuels towards the decarbonization of the maritime sector. Through a systematic review methodology, a combination of keywords and manual refining found a contribution of 103 works worldwide, the European continent accounting for 57% of all publications. Twenty-two types of fuels were cited by the authors, liquefied natural gas (LNG), hydrogen, and biodiesel contributing to 49% of the mentions. Greenhouse gases, sulfur oxide, nitrogen oxide, and particulate matter reductions are some of the main advantages of cleaner sources if used by the vessels. Nevertheless, there is a lack of practical research on new standards, engine performance, cost, and regulations from the academy to direct more stakeholders towards low carbon intensity in the shipping sector.

Thermoeconomic Analysis of Biomethane Production Plants: A Dynamic Approach

This work analyses the two most diffused technologies for biogas upgrading, namely water scrubbing and membrane separation. In order to carry out such analysis, these two technologies are coupled with photovoltaic panels and an electric energy storage system. The optimal water scrubbing renewable plant achieves a primary energy saving of 5.22 GWh/year and an operating cost saving of 488 k€/year, resulting in the best plant. It was compared to a reference system based on a cogenerator unit, directly supplied by biogas, producing thermal and electric energy, and delivered to the district heating network and to the electric grid. The profitability of both plants depends on the electric energy and biomethane exporting price. The proposed bigas upgrading plant achieves a payback period lower than 10 years with a biomethane selling price greater than 0.55 €/Sm3 and a primary energy saving index around 25–30% with a null share of thermal energy exported by the cogeneration plant.

The Effects of Using Pretreated Cotton Gin Trash on the Production of Biogas from Anaerobic Co-Digestion with Cow Manure and Sludge

Anaerobic co-digestion (AcoD) has been practiced for decades to convert waste into value-added energy products, especially biogas. This study aimed to assess the potential of biogenic methane (CH4) production from the co-digestion of pretreated cotton gin trash (CGT), cow manure, and sludge. CGT contains high cellulosic content, making it a reliable feedstock for biogenic methane production. To further improve the biogas quantity and quality, the CGT was subjected to physical pretreatments, i.e., hot water (HW), ultra-sonication (US), and a combination of both (HW+US). After 91 days of AcoD, 79–110 L of biogas was produced by the treatments. Among the treatments, HW+US-pretreated CGT presented maximum biogas production capacity, at 110 L. Besides, this treatment showed the high-quality biogenic CH4 content, 52.4% of the total biogas volume, with an improved conversion rate of 0.37 L/g of volatile suspended solids consumed. In addition, this study discussed the structural changes in feedstock due to pretreatments and correlated them with the corresponding biogenic methane production. The study reports the potential of pretreated CGT conversion to CH4. It will impact the circular economy by contributing to on-farm energy requirements and reducing the financial expenditures incurred in this regard.