This task aimed to determine the efficiency of current harvesting systems for energy crops (woody and herbaceous), and their individual components in terms of productivity, crop quality leaving the farm, cost and environmental impact.
Productivity and costs are closely aligned. Time taken and fuel used to harvest a unit area was recorded along with crop losses (in the field at harvest and in storage), along with fuel quality attributes (such as moisture content, inorganic composition etc.). The following deliverable reports a benchmarking of currently-commercialized systems for willow short rotation coppice. Among the various types tested, medium-scale foragers came out as the most promising system to produce chips, and was improved during the project based on a model designed by CRL, a project partner. A demonstration of the improved system was carried out in 2014 (see here for more details).
Rothamsted Research and CRL also made improvements to the cutting head and the cutting
mechanism of an existing smaller scale SRC harvester so that it presents the
stems to the intake mechanism better and causes less damage to the stool and
thereby does not affect the re-growth potential.
For grasses, Nobili and SSSA (2 project partners) developed a prototype grass energy crop harvester. The aim of the modifications was to increase the capacity with changes to the cutting mechanism and the working width. It was applied to Sorghum, Miscanthus and Giant Reed crops.
Tests for both systems (SRC and grasses) are described in this deliverable, prior to a commercial-scale demonstration reported in this other deliverable.
Harvest losses potentially contribute to soil carbon as long as the loss is left and incorporated in the soil surface by the use of machinery and/or via natural processes. Immediately post-harvest the stored crop was monitored for temperature, moisture content and dry matter changes. Particle size and overall bark content were quantified. Additional quality attributes such as inorganic composition (metals) will be measured pre and post storage. Post storage, the fuel consumed during secondary processing (e.g. chipping of billets or rods) of SRC woody crops weree measured as this parameter is not well quantified, but it is reported by the industry that partly dried wood requires greater power and therefore fuel to chip it.