Biomass combustion and carbon capture and storage (CCS) individually represent significant options for decarbonising the power generation sector and when combined may permit a carbon-neutral or even carbon-negative process. Despite this potential, little research has been published that examines the combustion of biomass in atmospheres with application in CCS processes. This work reports on bench- and laboratory-scale testing of biomass and coal combustion in atmospheres enriched in O-2 and CO2 which are relevant for retrofitting power stations for oxyfuel combustion. At bench-scale, thermogravimetric analysis shows substituting N-2 as the combustion diluent with CO2 has little impact on the combustion properties of the fuels but that increasing the O-2 concentration accelerates combustion of coal and biomass chars. Results from cofiring three biomasses with coal at 20 kW scale suggest substitution of N-2 with CO2 significantly reduces temperatures, carbon burnout and emissions of NO while combustion in O-2-enriched conditions has the opposite effects. Emissions of NO and SO2 were found to reduce compared to air in combustion atmospheres enriched with O-2 and CO2 while combustion temperatures and carbon burnout slightly increased. (C) 2014 Elsevier Ltd. All rights reserved.