The impact of biomass quality and quantity on the performance and economics of co-firing plants with and without CO2 capture

Co-firing biomass with coal has been proposed as a near term option for CO2 mitigation because it can be retrofitted to coal plants without major modifications. If CO2 capture is also implemented, negative emissions may result. Such negative emissions provide additional CO2 credits that can reduce the overall cost of capture. This paper investigates the impact of biomass quality and quantity on the performance and economics of co-firing plants with and without capture. We consider three biomass feedstocks (wood chips, conventional wood pellets and torrefied wood pellets) at three co-firing levels (5%, 20% and 40%). The results show that increasing biomass quality improves plant performance with a moderate increase in cost of electricity. At the highest co-firing level the plant emission intensity would be about 0.5 t CO2/MWh without capture and −0.5 t CO2/MWh with capture while the change in cost of electricity is relatively small at no more than 9.5%. General correlations for cost of electricity are developed that quantify the impact of fuel prices, carbon price and renewable energy certificates on cost of electricity as a function of biomass quality and quantity. At present, co-firing requires relatively modest incentives while the addition of capture requires higher incentives.