Table 3.

Assumptions, challenges and opportunities around a UK-based lignocellulosic biofuel system.

Source of UK system	Assumptions implicit in proposals	Challenges to assumptions (& potential opportunities)
Marginal land I for perennial crops (land that should be used as it is unsuitable or less suitable for food production)	There is sufficient land of this type available in the UK Production for lignocellulosic biofuel is technically and economically possibly on such land, despite lower quality It is possible in a market economy to restrict energy crops to such land, avoiding higher-quality land where yield (and profits) would be higher	In interviews, farmers agreed in principle to the idea that perennial energy crops should be grown on marginal land. But, for the most part, they did not consider their own land to be of marginal quality & in this sense, available for perennial crops. Legacy, pride in their work, skills developed over time with existing infrastructure and machinery, and their role in the wider rural community were crucial to farming identity. Farmers are not just profit-maximisers; they face multiple pressures due to changing sustainability demands, Common Agricultural Policy reforms, power of large supermarket chains as main buyers, etc. Changing to perennial crops may be an added challenge in this context.
Marginal land II for perennial crops (land that is currently economically marginal that is more likely to be used)	If some food production is displaced on this type of land (identified in Ref. [59] as grades 3 and 4), technological improvements (higher yields) will compensate Grassland (also identified as economically marginal in Ref. [59] is assumed to be suitable for conversion to cropland – but this is contested by others highlighting the release of soil carbon emissions	Farmers overwhelmingly took food production to be the moral purpose of farming, though their view of technological improvements compensating for displaced food is unclear Livestock farmers took their grassland to be of ‘prime quality’ in the sense of prime for grazing for their animals Where they judged some parts of their land to be economically marginal, multiple competing uses were foreseen
Crop residues (case of wheat straw)	Surplus of cereal straw estimated to exist in the UK with potential for bioenergy uses	Two-thirds of farmers in recent survey indicated they would be willing to supply wheat straw for bioenergy [19], though this would include different bioenergy applications, not only liquid fuel In interviews, farmers indicated they have little control over the end-use for baled straw as these decisions are taken by straw merchants while straw merchants indicated preference to preserve their existing customer base in non-fuel sectors There are tensions between bioenergy aspirations for using straw and the UK Code of good Agricultural Practice which recommends incorporating straw into soil, a message reinforced by agronomists