No abstract

No abstract

Isobutene (IBN, C4H8) is widely used in industry. Currently, IBN production relies on petrochemical processes. The current work assesses the comparative environmental sustainability of bio‐based IBN production routes based on first‐ and second‐generation sugar compared with fossil IBN by applying the ISO 14044‐based Life Cycle Assessment methodology. In total nine scenarios are examined. Scenarios 1–6 used first‐generation sugar for IBN fermentation and scenarios 7–9 use cereal straw‐based second‐generation sugar. The scenarios also differ in their process energy source. The savings in Global Warming Potential for first‐generation IBN are up to 68% (scenario 1); for second‐generation IBN, the savings reach 105% if an avoided burden approach for utilizing lignin as an energy source is applied (scenario 8). It is found that applying renewable process energy is a prerequisite to maximizing greenhouse gas savings. Special attention has to be drawn to the eutrophication potential, were none of the scenarios show savings. This is driven by sugar crop cultivation owing to fertilizer usage, thermal energy from solid biomass or natural gas due to NOx emissions and nutrient use for fermentation (e.g. ammonia). Scenarios 4, 7 and 8 show savings in the acidification potential compared with fossil IBN. A driver of acidification is biomass‐based process energy generation, mainly due to SO2 and NOx emissions from biomass combustion. In contrast, all scenarios show a better environmental performance concerning the freshwater aquatic ecotoxicity potential, the abiotic depletion and the photochemical ozone creation potential. Process development should focus on conversion efficiencies and a fully renewable process energy supply. © 2022 The Authors. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd.

The current work investigates the feasibility of a novel Carbon Capture and Utilization (CCU) approach—also known as Underground Sun Conversion (USC) or geo-methanation. The overall objective of the current work is a comprehensive assessment on the technical, economic and legal aspects as well as greenhouse gas impacts to be concerned for establishing USC technology concept. This is achieved by applying multidisciplinary research approach combining process simulation, techno-economic and greenhouse gas assessment as well as legal analysis allows answering questions about technical, economic feasibility and greenhouse gas performance as well as on legal constraints related to large scale CCU using geo-methanation in depleted hydrocarbon reservoirs. CO2 from the industry and renewable H2 from the electrolyser are converted to geomethane in an underground gas storage and used in industry again to close the carbon cycle. Process simulation results showed the conversion rates vary due to operation mode and gas cleaning is necessary in any case to achieve natural gas grid compliant feed in quality. The geomethane production costs are found to be similar or even lower than the costs for synthetic methane from Above Ground Methanation (AGM). The GHG-assessment shows a significant saving compared to fossil natural gas and conventional power-to-gas applications. From a legal perspective the major challenge arises from a regulative gap of CCU in the ETS regime. Accordingly, a far-reaching exemption from the obligation to surrender certificates would be fraught with many legal and technical problems and uncertainties.

This analysis estimates the technically available potentials of renewable gases from anaerobic conversion and biomass gasification of organic waste materials, as well as power-to-gas (H2 and synthetic natural gas based on renewable electricity) for Austria, as well as their approximate energy production costs. Furthermore, it outlines a theoretical expansion scenario for plant erection aimed at fully using all technical potentials by 2050. The overall result, illustrated as a theoretical merit order, is a ranking of technologies and resources by their potential and cost, starting with the least expensive and ending with the most expensive. The findings point to a renewable methane potential of about 58 TWh per year by 2050. The highest potential originates from biomass gasification (~49 TWh per year), while anaerobic digestion (~6 TWh per year) and the power-to-gas of green CO2 from biogas upgrading (~3 TWh per year) demonstrate a much lower technical potential. To fully use these potentials, 870 biomass gasification plants, 259 anaerobic digesters, and 163 power-to-gas plants to be built by 2050 in the full expansion scenario. From the cost perspective, all technologies are expected to experience decreasing specific energy costs in the expansion scenario. This cost decrease is not significant for biomass gasification, at only about 0.1 €-cent/kWh, resulting in a cost range between 10.7 and 9.0 €-cent/kWh depending on the year and fuel. However, for anaerobic digestion, the cost decrease is significant, with a reduction from 7.9 to 5.6 €-cent/kWh. It is even more significant for power-to-gas, with a reduction from 10.8 to 5.1 €-cent/kWh between 2030 and 2050.