Labor-intensive techniques for recovering energy biomass from forest tending operations

The study investigated the collection of renewable energy feedstock from the early thinning of red pine (Pinus brutia Ten.) forests, using labor-intensive semi-mechanized work techniques especially suitable for developing economies. The production of energy biomass may improve the financial sustainability of early thinning operations, promoting better forest management. The study was conducted on 165 trees, distributed among 6 stands in order to obtain general representation. Each tree record included tree weight by product type and the time to fell, extract and process the tree into commercial products. The experiment showed that early thinning may offer between 1.3 and 4.9 t (dry) of log product per hectare (10000 m2), but this amount can be doubled or tripled by changing to whole-tree chipping. Collection cost varied from 86 to 212 € t−1. Over 80% of total collection cost was represented by processing into logs or chips. Whole-tree chipping allowed a ten-fold increase of processing productivity, but the additional cost of the chipper offset any productivity gains. Therefore, one should consider transporting whole trees to the user plant or to an engineered wood yard, for storage and centralized processing. Future research should explore this opportunity, and determine the maximum transportation distance for cost-effective whole-tree transportation.