Air emissions from the fuel supply system of a Swedish CHP plant and the effects of stricter emission regulations

The purpose of this work was to quantify the energy use and production of air emissions by supply systems for different biofuels used in a typical Swedish combined heat and power plant. In addition, the effects of the future reductions in the total amounts of exhaust gas emissions, as a result of stricter emission regulations for transport and off-road equipment, were studied. A model was developed and used for the calculations. Input data were collected from a plant situated some 100 km from Stockholm in Sweden. Biofuels used by the plant include chips from limbs and tops, by-products from sawmills and chips from willow energy plantations. The results show that residues from sawmills are very favourable in terms of the studied environmental parameters. Air emissions from limbs and tops is 5–8 times greater than that from sawmills. The use of a terminal for temporary storage means that additional transport and loading operations are necessary which result in a 30% increase in air emissions. The most important effects of the stricter emission regulations are that emissions of nitrous oxides (NOx) caused by the supply system will decrease by up to 70% within 10 years and that the unburned hydrocarbon (HC) emissions will decrease by 30–35%.