There are many items to include when considering the sustainability of biomass for cofiring, and some of them are hard to quantify. The focus of this webinar is on the greenhouse gas emission aspects of sustainability. The reduction of greenhouse gas emissions achieved by substituting biomass for coal depends on a number of factors such as the nature of the fossil fuel reference system, the source of the biomass, and how it is produced. Relevant issues in biomass production include the energy balance, the greenhouse gas balance, land use change, non-CO2 greenhouse gas emission from soils, changes to soil organic carbon, and the timing of emissions and removal of CO2 which relates to the scale of biomass production. Certification of sustainable biomass is slow to emerge at the national and international level, so various organisations are developing and using their own standards for sustainable production. The EU does not yet have sustainability standards for solid biomass, but the UK and Belgium have developed their own.