Biomass Harvest from Natural Willow Rings around Prairie Wetlands

Abstract

The study followed the harvest of natural willow from three wetlands using a prototype modified agricultural round baler nicknamed a Bio-Baler. The study reports fuel characteristics and combustion testing of biomass harvested from natural willow rings. Composition of native willow species in the harvested willow rings was determined. We specifically measured regrowth of the biomass and number of regenerated stems per stump 1 year after harvest to determine how different willow species responded to mechanical biomass cutting with the Bio-Baler. The results of combustion testing for the natural willow were essentially similar to those with “conventional” wood chips or planted willows. The ash content was approximately 1.65%, slightly lower than for planted willow plantations. The calorific value of the natural willow was 19.6 MJ kg−1 (dry basis) similar to what is expected for wood and planted willow. Four Salix species (Salix bebbiana Sarg., Salix petiolaris Sm., Salix eriocephala Michx., and Salix discolor Muhl) were identified in the willow rings. Stem biomass increased for all species except S. bebbiana after willow was harvested with the Bio-Baler. Overall, willow regeneration was not affected by mechanical harvesting compared to hand cutting. Regenerated stem density was 93 stems per square meter for mechanically harvested stumps compared to 105 stems per square meter for hand-pruned stumps. Based on the results, biomass harvested from natural willow rings has acceptable fuel characteristics when compared to purpose-grown willows and mechanical harvest with a Bio-Baler does not have a negative effect on willow regeneration.