BECCS – bioenergy with carbon capture and storage – combines the use of a low-carbon fuel source (e.g. wood), with the permanent capture and sequestration of the CO2 released from combustion. This enables what is termed ‘net negative emissions’, which means that this process effectively removes CO2 from the atmosphere, as when plants grow, they absorb the CO2, which is then captured when it is used. Extensive experimental testing at the PACT facilities has investigated a range of biomass fuels coupled with different CCS technologies, including post-combustion and oxy-fuel methods. This is vital for scaling-up project so they can be used on a larger, commercial scale and make a real-world impact on emissions reductions.
The main research here has investigated the impurities in the fuels that can detrimentally impact the capture process. Key species and pollutants can have negative effects, especially on the solvents that are used to capture CO2. Through state-of-the-art methodologies, we have evaluated the implications of these – in particular metal aerosols and fine particles – to identify those that have the greatest impact; from this strategies can be devised to limit the detrimental effects these can have. This could involve, for example pre-cleaning the biomass fuels prior to use, or adding further gas cleaning stages before CO2 capture.
BECCS is critical for achieving UK and global carbon reduction commitments and the Hub Bio-CAP-UK project has demonstrated the importance of practical trials to build industrial confidence in the technology. Pilot testing will be performed using the UKCCSRC-PACT facilities to demonstrate, for greenfield applications, the potential of oxy-fuel capture technology for increased waste fuel flexibility, and, for retrofits, process integration at the pilot scale with a fully instrumented 250 kW grate-fired boiler burning Solid Recovered (waste) Fuel (SRF) with a 150kW solvent-based PCC plant. Extensive analysis of combustion gases, metal aerosols and particulate formation will identify key species and pollutants from the combustion process and their impact on the solvents and operation of the solvent-based carbon capture plant in waste-to-energy (WtE) conditions. Data and samples from previous projects by the applicants (e.g. Bioenergy Supergen, Bio-Cap-UKCCSRC) will inform the tests under a range of real operating conditions (air/oxy-firing) to evaluate the impact of alkali/transition/heavy metals and other species on: (i) the oxidative degradation and corrosion of CO2 capture solvents, initiated and aggravated by transition metal carryover and (ii) possible contamination of the high-purity captured CO2 stream with a range of inorganic elements. This will enable better understanding of the partitioning of elements from the combustion of these waste fuels under a range of realistic pilot scale conditions, leading to the formation of comprehensive and novel datasets on the fates of specific elements.
Mohamed Pourkashanian, Lin Ma, Karren Finney