Feasibility of significant CO₂ emission reductions in thermal power plants: Comparison of biomass and CCS

In the future greenhouse gas emission targets will be more ambitious and therefore solutions for of CO₂ emissions reduction more than 80% are sought. In thermal power plants these high levels of emission reductions can be reached with CCS technologies or by utilizing high shares of biomass based fuels. Following from the national targets of Finland, the power plants being planned at the moment need to take these targets into account in the planning phase as options that need to be fulfilled at least in the future if not immediately. In this paper high plant level CO₂ emission reduction targets are analysed for two large power plants that are planned to be constructed in Finland in the near future. Both are located close to urban areas and supply also district heat to neighboring cities. Both also face high political pressure to significant emission reductions in comparison to existing system. This paper is based on a case study of a planned combined heat and power (CHP) plant in Finland having fuel power of 420MWfuel. The boiler island is plant based on circulating fluidized bed (CFB) boiler technology enabling combustion of high shares of biomass. The paper is shortly describing technologies that are needed for reduction of CO₂ emissions when carbon capture based on oxyfuel technology and biomass firing based on high shares of forest residues are considered. The implications of applying these technologies and suitability for CHP environment are considered and economic feasibility of the solutions compared. Also the possibilities and feasibility of reaching negative emissions with combination of biomass firing and CCS is briefly assessed. Results show significant emission reduction potential associated to both technologies. The major costs associated to CCS are caused by the equipment investment, loss of electricity production due to energy penalty and transportation and storage of CO₂. The costs associated to biomass combustion with high shares are mainly caused by higher prices of biomass fuel in comparison to coal and lower power-to-heat ratio. Large biomass share has an increasing impact also on plant investment and O&M costs. On the other hand, significant savings are achieved in terms of CO₂ allowances. When discussing the biomass option one must also address questions related to availability of sustainable biomass, effecting pricing and competition of raw material between different uses such as forest industry or liquid biofuels production. And this further highlights the discussion on carbon stocks and carbon debt especially when Bio-CCS is considered. If the profound emission reduction targets are to be met, economically the difference between the technologies considered is not clear in all circumstances. All the most important parameters for the economic lifetime of the power plant include significant uncertainty therefore in this paper main focus has been in sensitivity analysis. The study reveals some major economical restrictions of the applicability of these emission reduction solutions. The pros and cons of the technologies in the light of feasibility and the role of these technologies as carbon abatement tools are discussed. The major factor effecting the technology decision is plant location in relation to availability of biomass, coal and CO₂ transportation&storage options, as well as heat demand (possibility to utilize CHP) in addition to political atmosphere and acceptability of technologies.