Benefits versus risks of growing biofuel crops: the case of Miscanthus

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The giant C4 grasses of the genus Miscanthus holds promise as candidates for the optimal bioenergy crop in the temperate zone with their high yield, cold tolerance, low environmental impact, resistance to pests and diseases, ease of harvesting and handling, and non-invasiveness. The latter is, however, only the case for the triploid and sterile species M. × giganteus, while great caution should be taken with the production of the seed-setting species of the genus. M. sinensis has already spread into nature from ornamental use in several parts of the world, where it is considered a serious invader. Other risks to consider are fire in the mature crop, the spread of pests and diseases and increased water use. These years, the first commercial large scale crop production results are coming through and will show if the promises are to be fulfilled and the risks can be handled. However, breeding, further development of the production chain, and stewardship programmes to avoid potential risks are still needed if Miscanthus is to compete with fossil fuel use and be widely produced.

Research highlights

Miscanthus × giganteus is high yielding, non-invasive, pest and disease resistant & low emission. ► However, seed setting M. sinensis are potentially invasive. ► Other risks are fire, high water use and acting as a vector for diseases in other crops. ► Avenues to counter the risks are proposed.

Introduction

Agriculture disturbs nature by creating conditions favouring growth of the species wanted by man and by stressing undesired species by soil tilling and pesticide treatments. This is also the case for biofuel crops where maximum yield is a key parameter to obtaining a positive energy balance and an economically profitable production. The inherent conflicts of maintaining the delicate balances between agriculture and nature, between food production and biofuel production and between greenhouse gas (GHG) emission and mitigation have been heavily debated in recent years [1, 2, 3, 4, 5•]. While the debate is ongoing, there have been a number of papers presenting the unanimous message that it is technically feasible for our planet to provide food for an increasing population and deliver large quantities of biomass for bioenergy purposes, while preserving natural areas, incorporating environmental concerns [6, 7, 8••], and ensuring a net global GHG reduction even if natural vegetation is displaced [9]. However, the accompanying message is that achieving this potential is a difficult and challenging task. It demands both technical development of agricultural methods and logistical chains and improved social and political development and governance in order to avoid the numerous pitfalls along the transformation route from fossil to biological resource use. This article describes the experiences of developing one of the most promising biofuel crops, Miscanthus, and evaluates benefits and risks with a special focus on the risk of invasiveness.

Section snippets

Why Miscanthus?

The choice of biofuel crop is important for the subsequent biofuel conversion process and for the energy yield. But just as important is the huge difference in environmental impacts of the different crop types due to variations in nutrient use efficiency, water use, pesticide demand, soil carbon impact, etc. A dividing line goes between annual and perennial crops, with the perennials usually providing the best environmental profile due to a lower fertilizer and pesticide requirement, a more

Agronomy of Miscanthus

Severe problems during the 1990s with crop failure in the first winter after establishment have more or less been overcome due to a better understanding of the interaction of climate with genetics, and to the development of new planting methods that have also reduced establishment costs by approximately 80% [24, 25, 26]. Several European companies (e.g. www.energycrops.com and www.nordicbiomass.dk) now offer commercial establishments of Miscanthus by harvesting rhizomes from mother fields and

Uses of Miscanthus

Miscanthus dry straw harvested in spring can be utilised as a solid biomass feedstock for direct combustion or gasification in the form of big bales, chopped material or pellets [17, 34]. Recent efforts have been expended to develop the crop into a biofuel crop using 2nd generation technologies [35, 36]. Fermentation is, however, hampered by the significant content of lignin, although this varies between genotypes [37]. Improved convertibility may be obtained by harvesting the green crop in

Risks associated with Miscanthus production

Many ideal traits for a biofuel crop are also known to contribute to invasiveness [41]. The seed setting species M. sinensis has spread from ornamental plantings into natural areas in Eastern parts of the US from Massachusetts to Florida, where it grows in open disturbed areas and forest edges [28••, 42]. And in Australia M. sinensis has spread into the Blue Mountains where it colonises disturbed areas, and can invade bushland after fire (Figure 2). In Europe M. sinensis varieties have been

The future for Miscanthus?

The wild selection M. × giganteus is already a very competitive and high-yielding genotype with a good environmental profile and very low risk of invasiveness (Table 1). This has led the Environmental Risk Management Authority of New Zealand to approve the release of M × giganteus into the country after concluding that “it is highly improbable that, after release, M. × giganteus could form self-sustaining populations anywhere in New Zealand, taking into account the ease of eradication” (//www.ermanz.govt.nz/

References and recommended reading

Papers of particular interest, published within the annual period of review, have been highlighted as:

  • • of special interest

  • •• of outstanding interest

Acknowledgements

The writing of this paper was funded by the Danish Ministry of Food, Agriculture and Fisheries. Valuable inputs were obtained during the OECD-sponsored conference Biosecurity in the New Bioeconomy organized by CSIRO in Canberra, Australia, in late 2009, as well as from the anonymous reviewers. The OECD Cooperative Research Programme provided support for the authors to attend a Biosecurity in the New Bioeconomy summit organised by CSIRO in Canberra Australia from 17 to 21 November 2009.

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