Hardwood whole tree chips: a fuel storage model analysis

Abstract

A pile of mixed hardwood whole tree chips was monitored for one year to identify the effects outside storage would have on the fuel potential of the exposed pile. A 20 foot conical pile was built by gravity feed from an overhead conveyor.

Moisture content, fiber loss, ash, specific gravity, higher heating value (HHV), temperature, packing density and pH were the variables examined and from these changes, Total Net Heating Value was estimated.

Moisture content and packing density showed a significant increase with time. Pile temperature remained below freezing for the first ten weeks of the study then rapidly rose above the ambient air temperature to a maximum of 82 degrees C before falling to near ambient where it remained.

After six months,moisture content within the pile stratified into layers reflecting steep moisture content gradients. The outermost layer became saturated, primarily due to rainfall while spontaneous drying reduced the innermost layer's moisture content.

The Total Net Heating Value (TNHV) was found to decrease 1.14 percent per month or 13.7 percent a year. Increased moisture content accounts for 88.5 percent of the loss. Lower HHV accounts for 11.5 percent of the loss in TNHV.

Storage suggestions and recommendations are included