Parallel Session 18 – Making the most of biogenic carbon – BECCUS

Thursday 24 October 2024, 14.00-15.30 BRT

Moderator: Trond Bratsberg (ENOVA, Norway)

Speakers:

• Christiane Hennig (DBFZ, Germany): Bioenergy with carbon capture and storage or utilization (BECCUS): From innovation to deployment
• Niclas S. Bentsen (University of Copenhagen, Denmark): The potential for Carbon Dioxide Removal (CDR) through bioenergy with carbon capture and storage (BECCS) – Case studies on wood chips and straw fired combined heat and power production in Denmark
• Saija Rasi (LUKE, Finland): Carbon dioxide utilization possibilities from acidic fermentation process
• Frederico Gomes Fonseca (DLR, Germany): Valorization of Waste Agricultural Residues from North-Western Germany: A Pathway to Biofuels and Long-term Carbon Storage within the UNLOC Concept
• Jean Felipe Leal Silva (UNICAMP, Brazil): BECCUS of waste CO₂ from ethanol production: techno-economic analysis and life cycle assessment

Selected conclusions and key messages:

• BECCS implies capturing and permanently storing biogenic CO2 from processes where biomass is converted into fuels or directly burned to generate energy. This leads to a net removal of CO2 from the atmosphere, which is one of the options for CDR* or negative emissions. BECCU implies capturing and utilizing biogenic CO2 to make for example additional e-fuels or polymers. E-fuels are a direct substitute for fossil fuels, leading to emission reduction. While several BECCU projects have been announced, current actions on governmental level seem to shift the focus from BECCU to BECCS.
• A few countries in Europe are very proactive in realizing BECCS. This is driven by national climate targets, progressing in national legislation and support schemes for BECCS. Key mechanism thus far has been bidding rounds. Also private companies see CDR (through certificates) as a business opportunity and require high quality negative emissions (such as related to BECCS) to achieve their decarbonisation targets.

• Two Danish BECCS cases were presented, one added on a straw-fired CHP plant and one on a wood chip fired CHP plant. Both cases adhere to the principles of CDR. The GHG savings and ‘carbon payback time’ of the BECCS installations were calculated compared to the installations without CCS. These carbon payback times are less than 1 year in one case and less than 4 years in the other case. The advantage is not immediate as more biomass is needed to provide heat for the carbon capture process. Moreover, the CO2 supply chain requires more facilities and transport.
• In Finland, there are less CO2 storage options, so carbon capture and usage (CCU) receives more attention. Biogenic CO2 is produced in anaerobic digestion and acid fermentation. So far, this CO2 is the least utilized, but it could be used in various industrial processes, for example in gas fermentation.
• The traditional fate of corn stover in Germany is that it is left on the field or used for animal feed, bedding or local heating. Current developments are looking at the option to produce advanced ethanol from corn stover. An alternative pathway is to convert the corn stover through a pyrolysis pathway. In the example, a production of 2.5 tons of maize corn can be expected per hectare per year, with a similar production of stover. A fraction of the stover is traditionally returned to the soil, allowing for the use of around 1.5 tons of stover per hectare per year. The stover can be processed using autothermal pyrolysis, producing a condensate fraction that can be upgraded to biofuels; a char fraction that can be used to produce activated carbon; and a gas stream where the CO2 can be purified and used for gas fermentation to produce acetic acid (with supply of green hydrogen). Activated carbons with alkali deposits have been reported to bind CO2 strongly, so these can be used for direct air capture.
• Conventional Brazilian ethanol has a carbon intensity of 20—25 gCO2e/MJ. CO₂ as by-product from sugar-to-ethanol fermentation is readily available at high concentration and high purity. When this CO₂ is captured and stored, the carbon intensity of the ethanol can be reduced to -8.5 gCO₂e/MJ. When these negative emissions are rewarded, the overall project has a higher internal rate of return than the ethanol plant without CCS. This is different for the case where the CO₂ is combined with hydrogen (derived from surplus electricity of the bagasse CHP) to produce advanced ethanol via gas-to-ethanol fermentation using the bacteria autoethanogenum. The electricity surplus of the biorefinery is not enough to convert all CO₂ in a gas-to-ethanol pathway. Moreover, replacing the electricity revenue with the additional revenue from advanced ethanol does not offset the additional gas-to-ethanol process costs.

* CDR is a human activity that captures CO2 from the atmosphere and stores it for decades to millennia. CDR principles are: (1) the CO2 captured must come from the atmosphere, not from fossil sources; (2) the subsequent storage must be durable, such that CO2 is not soon reintroduced to the atmosphere; and (3) the removal must be a result of human intervention, additional to the Earth’s natural processes.

Schematic diagram of carbon dioxide cycles for CCS and CCU in bioenergy routes (left) and comparison with fossil routes (right). Source: IEA Bioenergy.