Utilisation of boiler ash from biomass heating plants as fertiliser substitut

The utilisation of ash which comes from recently established biomass heating plants in Schleswig Holstein is suggested as a fertiliser substitute for arable land. In a case study the quality of different ash fractions of a combined heat and power (CHP) plant was investigated, which is using untreated wood chips from hedgerow biomass. Pot experiments with oats were set up in two different soils — a nutrient poor sandy soil with a pH of 4.7 and a sandy loam soil with pH 5.6. Two different ash treatments were used — 2 t/ha and 6 t/ha — representing an adequate supply of potassium, phosphorus and lime, respectively. Yield of oat in poor sandy soil was significantly increased (100 %) in the 2 t ash treatment. The increase in sandy loam soil was about 60 % of the unfertilised control. The ash treatment of 6 t/ha (approximately 2000 kg CaO-equivalents) on the sandy soil increased pH by 0.7 and on the sandy loam soil by 0.5 units relatively to the unlimed control.