'Energy grasses', grown specifically to generate power, are attracting excitement as an alternative energy source, but some of the claims are greatly exaggerated, says Jiang Gaoming.
Plants such as biannual or perennial grass, and shrubs like sorghum, willow and miscanthus, have been hailed as a biomass alternative to fossil fuels.
They are quick growing, can be harvested repeatedly, and are tolerant to arid and saline conditions so can be grown on otherwise unproductive land. But harvesting costs are high and land sources are geographically scattered and may be home to important biodiversity.
Gaoming warns that producing enough energy grass to meet demand would involve large inputs of fertiliser and water that could, in some areas, even offset the original goal of replacing fossil fuels.
Energy grasses may relieve the energy crisis to some extent, he says, but their potential failings need more scrutiny, particularly since large-scale planting could end up competing with food crops for land and resources.