Unearthing the hidden resource: Biomass from rootstock recovery

Termination of depleted orchards generates a large amount of residue, often turned into wood fuel. This operation is particularly difficult with rootstocks, which are laborious to extract and offer a very low-quality fuel. The authors tested a new technology, designed for efficient rootstock extraction. Contrary to conventional excavator-based technology, the new technology is able to cut and lift rootstocks in one single pass. A side-by-side comparative test was conducted on 16 sample plots, in a pear orchard. Clean rootstock weight ranged between 3 and 7 kg, and sample plot yield var- ied from 4 to 9 t ha-1 fresh rootstocks, depending on varietal. The new technology was five times more productive than the conventional technology, and allowed reduction of rootstock extraction cost by a factor of 3.8. The output-input energy balance was twice as favorable for the new technology, com- pared with the traditional one. No significant changes were found for what concerned rootstock con- tamination: the weight of raw rootstocks consisted of over 50% of soil, which would require a separate cleaning operation. Adoption of the new technology described in this paper may dramatically increase the viability of root biomass supply.