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Environmental credentials of miscanthus highlighted in academic paper

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An academic paper has been published that demonstrates to policy makers the environmental benefit of converting around 5% of lower grade, UK marginal agricultural land to miscanthus.

A key driver of this study was noted Miscanthus researcher, Dr. John Clifton-Brown, who worked with lead authors Dr. Jon McCalmont from Aberystwyth University and Dr. Astley Hastings from the University of Aberdeen.

“This paper was originally called the ‘policy paper’ because we wanted to create a clear, understandable document summarising current scientific research for policy makers. We started out by following an approach taken by the Intergovernmental Panel on Climate Change (IPCC), where confidence levels are attached to short statements based on supporting research evidence. The evidence presented is drawn from a wide range of published, peer reviewed scientific literature reported from field experiments in various environments over the last 20 years,” explains John.

According to John, the paper is a document that demonstrates how miscanthus can be beneficial in the agricultural environment and presents the evidence that is currently available to support this across six key areas. The first of which confronts the land availability issue:

1. Potential UK land availability

Based on advanced geo-spatial analyses, the paper concludes that there is enough lower grade agricultural land (also referred to as marginal land) in the UK to produce significant volumes of miscanthus biomass without impacting essential food production.

“The research team used digital mapping and advanced analyses to deduce their findings,” explains Astley Hastings.

“Of approximately 18 million hectares of farm land available in the UK, there is about 8.5 million hectares that is lower grade. 10 % of that land would amount to 850,000 hectares; however, not all of this would be suitable but around half, 425,000 hectares, could be viable miscanthus area.

“This is exciting because this estimate is broadly in line with governmental biomass strategy document which suggests that 350,000 hectares could be a practical level of land to populate with dedicated, perennial energy crops,” says John. “Ultimately it shows that our approach is in the same range outlined by the government, and explains why it’s a practical level for miscanthus planting in the UK.

2. Soil carbon

The paper looks at the resulting carbon levels when converting both grassland, and arable land to miscanthus.

“What we found was that converting semi-permanent grassland to miscanthus by traditional establishment (spraying, ploughing, tilling and planting) can result in an initial short term soil carbon loss, but research strongly suggests that this can be recovered within 2-3 years of the crop’s life,” says lead author Jon McCalmont, “and any initial short term carbon displacement is heavily outweighed by offsetting fossil fuel use.”

“And in arable crops where soil carbon is often depleted, converting to miscanthus will actually increase levels, long term,” he adds.

3. Nitrous Oxide (N2O) emission

Nitrous oxide is a very significant greenhouse gas and represents the primary climate change impact of UK agriculture.

“Gas emitted from nitrogen fertilisation in agriculture can be relatively high, especially in livestock farming, and comparatively, miscanthus emits much less than other farming practices,” says Jon. “While there is certainly scope for further research, the literature suggests that N2O emission can be eight times lower in unfertilised miscanthus than in annual crops, and up to 100 times lower than intensive pasture land.”

4. Water Balance

John Clifton Brown’s own research has shown that water-use efficiency in miscanthus is among the highest of any crop. “It’s extremely effective in converting water to biomass,” he explains.

“In terms of impact on the environmental water balance the study showed miscanthus can improve soil hydrology and leaching characteristics. Drainage water quality is improved and nitrate leaching is significantly lower than in arable.

“Improved soil structures mean greater water holding capacity, although high productivity does mean a greater demand for water. Soils may still be drier in a drought year though run-off and soil erosion would be greatly reduced in wetter years compared to conventional arable.

5. Biodiversity

The paper demonstrates how miscanthus provides a good habitat for wildlife when compared to more conventional, annual systems.

“Birds, for instance, can move in and out of the crop at the edge of the field; they like it, different species take advantage of the developing canopy structure across the year. Miscanthus cover is there for 10 months of the year undisturbed, much longer than other crops,” says Jon McCalmont. With a background in conservation land management these issues are close to this lead author’s heart.

“Any agricultural crop produced for the benefit of human consumption is going to present trade-offs in the environment, but in comparison to annual, intensive crops, miscanthus presents clear benefits in field boundary quality, cover and greatly reduced soil disturbance.”

“Because there are minimal or no chemical inputs on miscanthus crops, headlands and hedges are also directly impacted – with improved quality for wildlife. And earthworm diversity is also improved on arable land with levels more comparable to grassland soils,” adds Jon.

6. Greenhouse gas emission

The paper concludes that taking into account the potential to sequester carbon in soils, the reduced nitrous oxide emissions and the mitigation of fossil fuel use by using miscanthus as a bioenergy feedstock, the carbon intensity is one thirtieth of that of coal and one sixteenth that of natural gas from the North Sea and will contribute to supporting the governments climate change emissions targets.

“This was determined by using a spatial model of the life cycle assessment of miscanthus as a heating fuel, using advanced analysis of crop yield predictions and soil biochemistry,” adds Astley.

References: McCalmont J P, Hastings A, McNamara N P, Richter G M, Robson P, Donnison I S, and Clifton-Brown J, (August 2015). Environmental costs and benefits of growing Miscanthus for bioenergy in the UK. GCB Bioenergy, online.

Link to full environmental paper: