Why choose Miscanthus Giganteus?
Use of Miscanthus Giganteus and other biomass is considered by the EU and UK as a significant factor to meet its 2020 and 2050 targets, in reducing greenhouse gas (GHG) emissions. The Climate Change Act 2008 of UK, aims unilaterally, for reduction of domestic greenhouse gas emissions of 34% by 2020 and of at least 80% by 2050. The 2020 Renewable target for UK is that, 15% of its energy consumption is derived from renewables. In 2010, only 3% of its energy consumption was from renewables.
However, concerns have been raised about the sustainability of biomass use, especially in the context of alternate use of land for food production, and of the biomass for use in construction, bedding, paper etc; in addition there are the environmental impacts on biodiversity, air, water and soil to be considered too. Due to the increasing attention these concerns have received, they have been extensively reviewed by the government and the scientific community (1).
Present scenario in UK
In 2008, renewables and bioenergy contributed 222PJ to the total 9805PJ UK consumption of primary energy. Approximately 207PJ were obtained from imported and domestically produced biomass, of which ~116-170PJ were domestically produced biomass (inclusive of municipal waste) (1).
Of the total biomass, that is used for production of biofuels, used in bioethanol (blend of petrol and liquid biofuel) and biodiesel (blend of diesel and liquid biofuel), as well as electricity production, approximately 15% originate from UK crops. In 2013, this came from 51 thousand hectares which is 0.8% of the arable area in the UK. Arable land in UK is approximately 77% of its total land area (1,2,3).
The biomass that is imported, comes from neighbouring European countries, but also from as far as the US, Canada, Latin American countries, and Asia (Malaysia and Indonesia). Among the major biomass material imported are corn, oilseeds, palm, soy, corn, sugarbeet, sugarcane, wheat, and residues from neglected forests and unused co-products (e.g. sawmill residues). In 2010, Europe consumed most (13 million tonnes) of the wood pellets produced worldwide (16 million tonnes) (3). However, there have been instances when corporate practice in developing countries exporting biomass, have been unsatisfactory and unsustainable (1).
Domestic UK production of biomass has come from oilseed rape (1% of area), sugar beet (7% of the area) and wheat (2% of the area), while miscanthus giganteus is grown only on 0.1% of the total arable area in England. The area under Miscanthus giganteus was 7,000 ha, and short rotation crops (SRC), like willow was 3,000 ha in 2013 (2).
Strategy
To ensure that the biomass use would be effective in reducing GHG emissions in the short and long term, the UK government, on recommendations from the Committee on Climate Change, decided to boost its supply from domestic sources, as reliable global supplies would decrease by 2050. The portion of energy to be derived from biomass would be capped at 10-12%. Figure 1 shows the possible contributions from different sources based on several scientific studies that were reviewed.
Figure 1: ‘Range of predictions for the contribution to UK primary energy from domestically sourced biomass feedstocks' (Source: UKERC literature review of existing studies on UK biomass resources 2010).
To ensure secure as well as sustainable sources, the government made many recommendations (that are not all covered here, as they are too extensive and do not directly pertain to this article). To make energy production and use sustainable, the government foresees, more direct heating of homes and industries, use of low carbon generated power, combining heat and electricity production, use of purpose grown crops (energy crops) for biofuel production instead of corn, and including more domestic and agricultural wastes.
Use of straw (from wheat, barley, oats) and sugarbeet to produce biofuels will continue at current amounts, with only a little increase. A major expansion of area under Miscanthus Giganteus, other perennial grasses like reed canary grass, switchgrass and SRC would be encouraged. The reasons for this are many (1,2).
1. More sustainable
The perennial grasses, specifically Miscanthus Giganteus and SRC are seen as being more sustainable since they have a lower carbon impact (0.5 to 6.1 t CO2 e/ha/yr), than the annual food crops (3.4 to 11t CO2 e/ha/yr), provided, the biomass crops did not replace food crops and lead to indirect land use emissions (1).
In 2014, researchers from Bangor University and the Thünen Institute in Germany concluded that crop-biogas and liquid biofuels are not the best way to use biomass to reduce GHG emissions, when the land, technique, inputs and subsidy used are taken into consideration. They could on the contrary lead to increased GHG emissions due to indirect land use change emissions. According to them, Miscanthus Giganteus (woody grass) heating pellets and waste-biogas, effect at least ten times more GHG mitigation per tonne of dry matter biomass and per hectare of land used (4).
2. Profitability
The total area in UK used for agriculture is 18.26 Mha. To make biomass generation more sustainable, Miscanthus Giganteus and SRC are considered key. There is an area of ‘0-93 and 3.63 Mha in England and Wales' available for their production. It is estimated that SRC can be planted on 0.62-2.43 Mha (3-13%) of agricultural land with a profit margin of £241/ha. Miscanthus can be planted on 0.72 – 2.80 Mha at a profit margin of £526/ha to generate 59.3 Twh (1) .
3. Yield
Miscanthus Giganteus yields significantly more than food crops used for making biofuels, or even perennials like switchgrass or SRC.
In UK, Miscanthus Giganteus yields average 12-15 oven dried tonnes (odt) per hectare (equating to 15-18 fresh tonnes per hectare). Though there has been a lot research on SRC yields, data in this regard is scarce. SRC are usually harvested once in 3-4 years. Willow SRC at first harvest gives 7-12 odt/ha/yr and poplar a yield of 8 odt/ha/yr. Annual UK cereal straw production is 9 to 10 million tonnes per year; with yields of 3.5 tonnes/ha for wheat and oats and 2.75 tonnes/ha for barley (2).
In a study published in 2008, from Illinois,US, Miscanthus Giganteus was compared to corn and switchgrass. The production of ethanol feedstock per acre of switchgrass was similar to corn. Switchgrass is more sustainable than corn as it requires less chemical inputs and is perennial (so it involves less cultural practices), thereby reducing use of fossil fuels and GHG emissions. It was estimated that if corn or switchgrass were used to offset 20 percent of gasoline use (US goals), 25% of US current cropland would be necessary. Since Miscanthus produces 2 1/2 times the amount of ethanol produced per acre of corn or switchgrass, only 9.3 % of land would be necessary. Producing ethanol by using Miscanthus Giganteus as feedstock could reduce the land necessary to produce biofuels (5).
In addition Miscanthus Giganteus uses little or no chemical inputs reducing its carbon impacts further, in comparison to switchgrass a perennial or the annual corn crop. The difference between Miscanthus, and switchgrass or corn, is its high yields. Miscanthus Giganteus begins growing six weeks earlier than corn and continues well into October, while corn is harvested in August.
Miscanthus Giganteus manages to capture 1% of solar energy and convert it to biomass. Though switchgrass is perennial it does not capture the same amount of solar energy as Miscanthus (5). The lower yield from switchgrass makes it less suitable as a biomass crop (6).
4. Land quality
Growing cereal crops requires good arable land. Miscanthus and SRC are suitable for growth on land of low productivity, or those contaminated with heavy metals, even though yield may be less than optimal. Using Giant Miscanthus and SRC can reduce indirect land use change emissions and minimise impacts to food production. So, area under bioenergy crops can be easily expanded, using millions of hectares of that need to be remediated (2).
5. Environmental impact
Giant Miscanthus and SRC have less environment impact on soil, air and biodiversity. They support more flora (weeds), birds, invertebrates, as well as soil microflora and microfauna compared to cereal crop fields (2).
6. Chemistry
Since, Miscanthus Giganteus has lower concentrations of moisture and ash, in comparison to other bioenergy crops, it is being considered as a key candidate for use in biomass-to-liquid fuel conversion and biorefineries (7).
Conclusion
Considering yield, profitability and chemistry, Miscanthus Giganteus proves to be the better option even among perennials and SRC. In addition, it has less environmental impacts and is more sustainable compared to cereal crops.
Currently, only 0.01 Mha of land in UK is being used for bioenergy crops, providing 0.21 Twh equivalent. Some of the reasons, preventing an increase in the area under Miscanthus, is grower acceptance, planting and harvesting capacity, and social resistance. The government wants to increase area under Miscanthus by 20% every year, to cover 0.04 Mha (0.22% of UK's agricultural area) by 2020, to generate 0.855 Twh equivalent (1).
Ongoing research will lead to improvements in productivity of Miscanthus, ‘and even though its expansion on a large scale has begun, Miscanthus is still in its infancy as an agricultural product', and is a crop with great potential (5).
Sources
1. UK Bioenergy Strategy
2. Department of Environment, Food,and Rural Affairs. 2014 (nonfood-statsnotice2012-10june15.pdf)
3. Bioenergyreview. Technical paper2. Global and UK energy supply scenario. Committee on Climate change. 2011. (1463CCC-Bio-TP2_Supply-scen_FINALwithBkMks.pdf)
4. http://www.bangor.ac.uk/news/research/waste-biogas-is-at-least-ten-times-more-effective-than-crop-biogas-at-reducing-greenhouse-gas-emissions-22025
5. http://news.illinois.edu/NEWS/08/0730miscanthus.html
6. http://phys.org/news/2015-06-switchgrass-biofuel.html#jCp
7. http://www.bioenergycenter.org/besc/publications/brosse_miscanthus_yr5.pdf