Using sustainably-grown biomass as the sole fuel, or co-fired with coal, is an effective way of reducing thenet CO2 emissions from a combustion power plant. There may be a reduction in efficiency from the use ofbiomass, mainly as a result of its relatively high moisture content, and the system economics may also beadversely affected.The economic cost of reducing CO2 emissions through the replacement of coal with biomass can beidentified by analysing the system when fuelled solely by biomass, solely by coal and when a coal-biomassmixture is used.The technical feasibility of burning biomass or certain wastes with pulverised coal in utility boilers hasbeen well established. Cofiring had also been found to have little effect on efficiency or flame stability,and pilot plant studies had shown that cofiring could reduce NOx and SOx emissions.Several technologies could be applied to the co-combustion of biomass or waste and coal. The assessmentstudies here examine the potential for co-combustion of (a) a 600 MWe pulverised fuel (PF) powerplant, (i) cofiring coal with straw and sewage sludge and (ii) using straw derived fuel gas as return fuel;(b) a 350 MWe pressurised fluidised bed combustion (PFBC) system cofiring coal with sewage sludge; (c)250 and 125 MWe circulating fluidised bed combustion (CFBC) plants cofiring coal with straw and sewagesludge; (d) 25 MWe CFBC systems cofiring low and high sulphur content coal with straw, wood andwoody matter pressed from olive stones (WPOS); and (e) 12 MWe CFBC cofiring low and high sulphurcontent coal with straw.The technical, environmental and economic analysis of such technologies, using the ECLIPSE suite of processsimulation software, is the subject of this study. System efficiencies for generating electricity are evaluatedand compared for the different technologies and system scales. The capital costs of systems areestimated for coal-firing and also any additional costs introduced when biomass is used. The Break-evenelectricity selling price is calculated for each technology, taking into account the system scale and fuel used.Since net CO2 emissions are reduced when biomass is used, the effect of the use of biomass on the electricityselling price can be found and the premium required for emissions reduction assessed. Considerationis also given to the level of subvention required, either as a Carbon dioxide Credit or as a Renewable Credit,to make the systems using biomass competitive with those fuelled only with coal.It would appear that a Renewable Credit (RC) is a more transparent and cost-effective mechanism to supportthe use of biomass in such power plants than a Carbon dioxide Credit (CC).
- Biomass Co-combustion
- Fluidised bed
- Economic analysis
- Environmental credits
McIlveen-Wright, D., Huang, Y., Rezvani, S., Mondol, J. D., Redpath, D., Anderson, M., Hewitt, N., & Williams, BC. (2011). A Techno-economic assessment of the reduction of carbon dioxide emissions through the use of biomass co-combustion. Fuel, 90(1), 11-18. https://doi.org/10.1016/j.fuel.2010.08.022