Carbon Capture from Biomass Boiler Flue Gas Emissions using Microalgae : A Case Study

Sammanfattning: Capture and storage of carbon dioxide (CO2) is expected to play an important role in climate change mitigation efforts intended to limit global warming to 1.5 °C. Bioenergy with carbon capture and storage (BECCS), in which carbon is captured during energy generation from sustainably sourced biomass fuels, is of particular interest in Sweden. Danone AB, an international food and beverage manufacturing company, operates a facotry in Skåne, Sweden, and will begin operating a medium-scale biomass-fired industrial bioler at the end of 2023 with annual projected emissions of 4-5 kilotons CO2. This case study investigates two post-combustion carbon capture technologies, industrial cultivation of microalgae and amine solvent absorbtion, and their potential with regard to implementation at the Lunnarp factory as BECCS solutions. Microalgae capture carbon through photosynthesis and biomass growth, while amine solvents selectivley absorb carbon from the boiler flue gas. Microalgae is a developing technology; amine absorption is the most mature carbon capture method and was used as a benchmark for comparison. Both technologies were evaluated considering complete capture of the boiler carbon emission.  Carbon capture using microalgae had significantly higher capital investment costs at 36-78 million € depending on the cultivation technology, compared to 4.3-6.4 million € for amine absorption. Microal-gae also require a large amount of land, 36 to 145 hectares depending on the cultivation technology, to achieve the necessary 2300-3000 tons per year of algae production.This is significantly more land than is currently available at the Lunnarp facility (5 hectares). The footprint for amine absorption is much smaller, requiring less than 1 hectare. Growth of microalgae biomass requires the use of nitrogen and phosphorus fertilizer to provide necessary nutrients, with associated offsetting carbon emissions of 600- 900 tons CO2 per year. Both capture processes have relatively similar energy requirements: 4-11 GWh/year for microalgae (assuming heating demand is met by factory waste heat) and 4-7 GWh/year for amine absorption. Because the heating temperature for amine absorption is too high for utilization of factory waste heat, that energy has associated offsetting CO2 emissions of 1300-1800 tons per year. Implementation of microalgae carbon capture presents significant challenges, including the space required, high capital costs, and establishing the market potential for an annual quantity of algae production greater than the current production level of all other algae producers in Europe combined. Amine absorption, while cheaper and more efficient, would have its ownc hallenges with post-capture handling considering the lack of CO2 transportation and storage infrastructure in Sweden. For either technology, there exist multiple potential partner companies or organizations that could work together with Danone to provide the experience and technical expertise in their respective fields. Such organizations include Pond Tech and Scandinavian Algae Company for microalgae cultivation and Mitsubishi Heavy Industries for amine absorption technology, specifically small-scale modular carbon capture. Regardless of the technology, concerns exist regarding the sustainability of carbon capture with regard to the security of sequestered CO2 and the diversion of resources and investment from other climate mitigation efforts such as renewable energy production.