Published Thursday, 26th May 2016 in Research news
With despite uncertainty over future levels of subsidy for energy production there is still considerable interest in using grass as a feedstock for on-farm anaerobic digestors (AD).
Speaking at a seed trade open day near Aberdeen David Lawson, Grassland Specialist with Scotland’s Rural College, stressed that
herbage grass is as productive as most other crops used for AD, with one tonne
of grass dry matter capable of producing 270 cubic metres of methane gas.
Grass seed Trade open day is an opportunity for commercial companies to discuss
the progress of new grass varieties under trial before recommendation to the
National List. The species routinely tested are: Perennial, Italian and
Hybrid Ryegrass, Timothy and Festulolium, along with white and red clovers.
contributes to a UK wide, four year programme in conjunction with SASA, the
Scottish Government’s division offering Science & Advice for Scottish
Agriculture. They evaluate new varieties under both conservation management and
simulated grazing. However accepted varieties must then complete three further
years of trials at SRUC sites in Ayrshire, Edinburgh and the NE before being
approved as fit to thrive in Scottish conditions.
the meeting David Lawson explained the system has led to a year on year
improvement in grassland productivity.
instance, the average dry matter output of the Scottish Recommended varieties
of Perennial ryegrass has increased by 9% from 2010 to 2015. That’s a 9% increase
achieved with no increase in inputs.”
that for anaerobic digestion systems Italian ryegrass is the species most
commonly used, because of its high dry matter productivity, although high
yielding perennial ryegrasses or Timothy can also be used.
according to David Lawson, there are new sustainability criteria for AD which
those planning grass based systems must take into account.
“One of them
concerns the need to minimise the production of green-house gasses from any
crop cultivation, including grass herbage,” he said. “So it is important to
reduce the use of nitrogen fertiliser. Some, but not all, of the nitrogen
needed in the process is supplied by the digestate material left after grass
has been used to make gas. But to reduce the need for fertiliser nitrogen still
further it is becoming very important for farmers to establish clover in their
grass pastures and supply nitrogen naturally. The varieties of clover that will
thrive in Scottish conditions can also be found in the Scottish Recommended
list of Grass and Clover Recommended Varieties is available on the SRUC
website at http://www.sruc.ac.uk/downloads/download/1022/tn673_recommended_grass_and_clover_varieties_2015-2016
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