Cofiring of coal with waste fuels (Fernando, 09-2007)

There has been considerable interest in cofiring both biomass and waste fuels in coal-fired power plants in recent years. This is principally due to concerns regarding the emissions of greenhouse gases from these plants. Biomass and some waste fuels can be considered to be renewable and not to produce net CO2 emissions when combusted hence cofiring these fuels in coal-fired plants reduces net greenhouse gas emissions. Another reason for cofiring wastes is that, as there is less space available for landfilling waste, it is desirable to find alternative routes for waste disposal. Waste fuels are also generally much cheaper than coal or biomass. This report concentrates on the direct cofiring of bio-derived fuel and wastes in coal-fired plant.

Wasre fuels such as sewage sludge, RDF, tyres and MBM have been cofired in all types of plant but to a much lesser extent than fuels such as herbaceous and woody fuels. Similar technical issues affecting the operation of the plant arises with all these fuels which need to be addressed. These relate to the differing composition of coal and waste fuels. The issues which arise include handling, storage, combustion and corrosion. The legislation applicable to plant cofiring waste is invariably stricter than plant cofiring biomass and more rigorous emission controls will be needed. Public opposition to cofiring waste will also be greater. Nevertheless cofiring waste in coal-fired plant may be more environmentally acceptable than other methods of waste disposal.