Co-firing of upgraded biomass towards flexible CO2 reduction for coal-fired power plants in China

The increasing trend in CO 2 emissions from fossil fuels has accelerated the renewable energy development, especially in China, the world's largest CO 2 emitter, which targets carbon peaking by 2030 and carbon neutrality by 2060. Co-firing of raw biomass is a promising carbon–neutral energy option in China, but its application is limited to only 10% incorporation with stable combustion performance. Therefore, in this study comprehensively assessed biomass upgrading methods, including torrefaction, pelletization, pyrolysis, and gasification, demonstrated that upgraded biomass exhibited significant potential as an attractive, feasible, and sustainable alternative fuel for a low-carbon approach to co-firing in existing PC power plants. The existing research work revealed that the recent Chinese energy policies support the co-firing of biomass, while biomass upgrading technologies are under development and need bioenergy-supported policies. The results showed that upgraded biomass enables higher co-firing ratios in PC boilers, achieving up to 50% substitution on an energy basis and reducing net CO 2 emissions by up to 50% compared with full coal combustion. Co-firing of the upgraded biomass not only maintains the high efficiency of PC and CFB furnaces, but also has the potential to lower their carbon footprint and NO x emissions. Additionally, the effectiveness of the co-firing strategy for achieving carbon neutrality is evaluated. This review paper can assist in identifying the potential methods that can increase the biomass-to-coal ratio during direct co-firing in existing PC furnaces without requiring large modifications.