Changes of willow biomass quality as renewable energy feedstock harvested with biobaler

Willow biomass can be collected in the form of entire or chipped shoots. The method depends on the harvest cycle of the plants, availability of necessary machines and the expected use of harvested raw material. Methods of harvesting influence on biomass quality during its acquisition and further in the storage period. Therefore, the aim of the research was to characterize the harvest of willow plantation with the use of a biobaler WB 55 and to assess the quality of the obtained biomass during the 9-month period of its storage. Willow was harvested with biobaler WB 55 in January 2010 on a commercial plantation. The 3.5 ha plantation was situated in the north-east of Poland, in the village of Dorotowo (53°42′9.88″ N 20°25′11.02″ E). An analysis of the biomass quality in terms of its thermophysical and chemical properties was carried out at the laboratory of the Department of Plant Breeding and Seed Production of the UWM in Olsztyn. Willow harvesting with a unit consisting of a 129 kW tractor and biobaler WB 55 was conducted efficiently. The average harvesting efficiency was about 18 bales per hour of the unit operation (8.75 Mg h-1 FM). The fresh matter density in the bales averaged 358.10 kg m-3 FM, whereas in dry matter it was 166.16 kg m-3 DM. With extended duration of storage, the quality of willow biomass as an energy raw material improved. The biomass in the bales steadily lost its moisture, from 53.06% in January to 17.48% in September. On the other hand, the lower heating value increased during that same period from 7.75 MJ kg-1 to 15.65 MJ kg-1. It has been found based on the observations made during the study period that the advantages of a biobaler WB 55 are the easy and efficient harvesting of plants on a plantation and bales can be used for energy production as needed.