Chemical Properties and Ash Slagging Characteristics of Solid Fuels from Urban Leaf Litter

Urban leaf litter occurs in significant, yet unknown, quantities and is regularly disposed of or composted. Instead, it could be widely used as a regional resource for solid fuel production. Samples of five tree genera (Acer, Aesculus, Fagus, Tilia, Quercus) were taken after leaf abscission and analyzed for elemental composition (C, H, N, S, Ca, Cl, Cu, K, Mg, Mn, Na, P, Zn) and ash slagging behavior. Ash content was generally high (13.8 % dry matter) due to soil adherence. Mashing and subsequent mechanical separation significantly reduced concentrations of Cl, K and S in the resulting press cake, resulting in concentrations of 0.01, 0.36 and 0.07 % dry matter respectively (mass flow into press cake: 25.6, 51.54 and 73.83 %, respectively). Average lower heating value of the press cake was 19.22 MJ kg−1 dry matter (ash free). Processing elevated the mean ash softening temperature from 1233 °C for raw materials to 1245 °C for press cakes. However, processing did not alter ash content, which indicates that additional washing is necessary for a further increase in fuel quality.