Influence of the chip format on the development of mass loss, moisture content and chemical composition of poplar chips during storage and drying in open-air piles

Abstract

In order to use wood chips from short-rotation coppices cost-efficiently, it is necessary to optimise the storage process depending on the planned use of the chips. The goal of all storage is to ensure low dry matter losses. Wood chips intended for energy-related use should have low moisture and ash contents, as well as a low fines fraction. If wood chips are to be put to material use, e.g. as peat substitute, a reduction of the C:N ratio during storage is necessary.The objective of this study was to identify favourable storage conditions to ensure low dry matter losses and high quality of wood chips for energy-related use. Furthermore, the study aimed to examine, whether disintegration processes during storage change the C:N ratio to such an extent that wood chips can be used as raw material for plant substrates.Three wood chip piles with different chip formats (small, medium, large - produced with a forage harvester and a mower chipper) were stored for seven months and compared regarding storage properties and physicochemical parameters.After seven months, medium wood chips displayed with a moisture content of 26w-%, dry matter losses of only 17% and a fines fraction of <5w-% the best results for energy-related use. Small chips with dry matter losses of 19%, moisture contents of 34w-% and a fines fraction of 12.6w-% displayed very unfavourable conditions for energy-related use. However, small chips showed the highest reduction of the C:N ratio (from 145:1 to 57:1) due to the storage process.