Recovering Kiwifruit Pruning Residues for Biomass Production

Abstract

Three systems for recovering kiwifruit pruning residues were compared for their cost-effectiveness. The systems were a shredder with a built-in dumping container; a shredder with drop-down re-usable bins, of the type normally used for fruit collection, working with a dedicated bin-collection system; and a round baler equipped with an add-on bale storage unit. All systems were light enough to be towed or carried behind a compact vineyard tractor. Harvesting and processing productivity, including all delays, ranged from 1.8 to 3.7 tonnes per scheduled machine hour (SMH). After standardization, calculated recovery cost varied between 8.4 and 28.6 Euros t-1 for the residue delivered at the field edge. The shredder with a built-in dumping container emerged as the best performer, favored because of a faster pick-up and a more efficient single-pass work mode. Overall, this system is simpler, more productive, and offers the lowest processing cost. The annual utilization of all the dedicated recovery implements tested should at least be 50 ha year-1 (approx. 500 t year-1) in order to obtain acceptable cost results. Kiwifruit orchards offer a very high residue yield, about four times higher than vineyards and olive tree groves. This favors cost-effective recovery and makes them a significant potential source of energy biomass, the exploitation of which may also simplify residue management and improve plant health conditions.