Energy biomass from the low-investment fully mechanized thinning of hardwood plantations

Agroforestry practises can accrue significant benefits to farm owners and have a good potential for expansion worldwide. Among the many possible options, Black walnut plantations are especially popular in the Temperate zone, and are often based on the association with nurse trees, to be removed within the first two decades after establishment. The authors designed and tested two low-investment fully mechanized operations for producing chips or traditional firewood from the thinning of walnut plantations. The mechanized small-scale chipping operation incurred the lowest cost and offered a dramatic improvement over manual harvesting. On the other hand, mechanized firewood harvesting was financially less effective than traditional motor-manual operations. For the price levels assumed in this study, small-scale mechanized chipping offered higher profits than motor-manual firewood production all along the tree size range. Furthermore, chipping achieved a break even with smaller trees than firewood production, allowing for financially viable early thinning, timely performed before the nurse trees overtop the crop trees.

► Timely thinning can yield 25–50 green tons of energy biomass per hectare.
► The mechanized small-scale chipping operation incurred the lowest cost.
► Mechanized firewood harvesting was less effective than motor-manual operation.
► Chipping achieved a break even with smaller trees than firewood production.