Technology alternatives for tapping the pruning residue resource.

Four commercial harvesters were compared with respect to recovery of pruning residues for energy conversion. These harvesters were tested side-by-side on 17 test fields, totaling 15 ha. The test fields consisted of vineyards and apple and pear orchards. The residue yield was between 0.7 and 9 green tonne per hectare, at a moisture content from 37% to 48%. Yield was highest for the orchards, and lowest for vineyards. Harvesters collected the residues and moved them to the roadside at a cost of between 11 and 60€ per green tonne, depending on field conditions and technology choice. Single-pass harvesting was the cheapest, especially if applied through a dedicated tractor and a towed unit with a large integral container. Two-pass harvesting was the most flexible, but also the most expensive: it should be favored only when space, weather or other management constraints limit the application of the other systems.