Värdeskapande av koldioxid från biogasproduktion
Authors: Gustafsson Marcus , Cordova Stephanie 
Published: September 2023

arbon dioxide (CO₂) has a negative impact on the climate, but it also has several practical areas of use. Many industrial processes emit CO₂ in high concentrations, which could be captured to mitigate emissions while also creating valuable products. One example of such a process is biogas upgrading – a process separating renewable gases, where methane is taken care of for use as vehicle fuel or industrial energy carrier, while CO₂ is released into the atmosphere. The aim of this project has been to chart alternatives and technologies for taking care of green CO₂ from biogas upgrading, so-called carbon capture and utilization (CCU), and to investigate the conditions for applying these in a Swedish context. The work has been guided by the following research questions: * How large is the current and future potential for CCU from biogas production? * What are the possible areas of use for CO₂ from biogas production? * What factors influence the choice of areas of use for CO₂ from biogas production? * How large is the environmental benefit of CCU from biogas production? To answer these questions, calculations of potentials, a multi-criteria assessment and a life cycle assessment were carried out, based on the Swedish biogas production. A reference group comprising representatives for large Swedish companies within biogas production and biogas upgrading technology was used to enable coproduction and networking between the research group and the business sector. The production of CO₂ from biogas was estimated to 160,000 ton/year in 2020, with potential to increase to 540,000 – 840,000 ton/year in a few years and 790,000 – 1,230,000 ton/year in a longer perspective, as a consequence of an expected increase in the Swedish biogas production. A large share of the CO₂ is however produced at relatively small upgrading facilities, which could limit the feasibility for CCU due to high costs for investment and operation. Adding hydrogen to transform all the CO₂ into methane could potentially increase the methane production from biogas from 2 to 3 TWh/year in a short-term perspective and from 11 to 17 TWh/year in a long-term perspective, given sufficient access to hydrogen. Other ways of utilizing CO₂ from biogas include production of biomass or chemicals, concrete curing, pH control of process water and use as a refrigerant. The choice of CCU options can be influenced by environmental, technical, economic and policy-related aspects. From the biogas producers’ perspective, methanation is the option that is the most compatible with the existing production system and business model, while other solutions usually involve another actor taking care of the CO₂. Hydrogen is required for methanation as well as for production of chemicals. Another limiting factor are the high purity requirements on all CO₂ that is distributed and sold on the market. The geographical distribution of the production plants can also be a challenge. Several CCU options can improve the environmental performance of biogas by replacing fossil-based products. The potential climate impact is the lowest if the CO₂ is methanized with renewable hydrogen or mineralized in concrete, but other forms of environmental impact can also be reduced by applying these or other CCU options. For comparison, permanent storage of CO₂ in geological formations (carbon capture and storage, CCS) only reduces the climate impact, while it increases other forms of environmental impact. Furthermore, permanently storing biogenic CO₂ can make it difficult to reduce the use of fossil CO₂ and transition to a more sustainable society. The need for carbon in many essential processes and products suggests that biogenic CO₂ should be utilized and not stored.