An increasing number of utilities in Europe - but in North America and South Africa as well - are co-firing biomass or consider co-firing of biomass in one or more of their power stations. A few power stations have even taken a step further by considering full conversion from coal to solid biomass fuel. When considering biomass fuel both technical matters as well as economics, including fuel properties and fuel supply must be taken into account. DNV KEMA has long time established experience in advising utilities on this matter. In this paper DNV KEMA summarizes the implication of biomass (co-)firing ranging from a limited amount of ～ 10% up to 100% replacement of coal by biomass. Topics that are addressed in this paper are: 1. choice of biomass fuel such as wood chips, wood pellets or refined pellets and required modifications to adapt the unit to the selected fuel 2. fuel handling; fuel preparation and effects on combustion performance 3. thermodynamic effects like boiler efficiency 4. boiler derate 5. effects on boiler integrity with respect to slagging, fouling, corrosion 6. emissions and flue gas cleaning 7. effects on fly ash quality and composition. Based on case studies performed by DNV KEMA examples of trends and technical consequences are given. Apart from the technology, the economics play a major role in the viability of biomass co- firing. Nearly all successful biomass co-firing and biomass to coal conversion projects have been based on substantial financial incentives that resulted from political decisions. Therefore also an outline of the economics is presented.
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