Properties of compression dewatered and baled aspen wood chip fuel use

This project investigated basic relationships of the compression dewatering and baling of wood chips. The following fundamental aspects of experimental, compression dewatered chip bales were investigated: bale durability, moisture content (MC) and distribution, biodeterioration and internal heating. These factors were studied over time with bales of three different densities. Bale physical durability was dependent on restraining forces. As restraining forces decreased (i.e., lower density bales or as bales dried below the fiber saturation point), bale integrity declined. Bales in a controlled environment (65?F and 50% RH) dried in a manner similar to solid wood, that is, rapidly within the first 30 days and then at a slower rate thereafter, reaching a final MC of 15 percent (dry basis) at 98 days. However, MC distribution within bales was highly variable and only partially dependent on time, bale density, and external insulation. It is likely that internal heating, due to respiration and microorganism activity, also influenced MC distribution. Bale density and insulation (simulated stacking) were found to influence the growth of wood-inhabiting organisms that in turn produced varying levels of heat within bales. However, several temperature peaks (up to 35?F above ambient conditions) were found in all bales at approximately the same time, which indicated that factors other than density and insulation also influenced temperature increases within bales. Bales with higher density and slower drying rates supported extensive growth of the white-rot fungus Phanerochaete chrysosporium. Wood in such colonized areas was approximately 20 percent lower in specific gravity than uncolonized wood, but retained the same caloric value per unit of weight.

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