LONDON — Record high world food prices threaten to limit the use of land for low-carbon energy crops just as British efforts to pioneer growth of the giant grass miscanthus in Europe are poised to gather pace.

Miscanthus giganteus is an Asian elephant grass that grows 3 meters, or 10 feet, high and whose tawny leaves are now at their tallest, before harvest time next month. The grass is being promoted alongside willow, sawdust and straw as biomass for producing heat and power when burned, without causing net emissions of the greenhouse gas carbon dioxide.

Burning biomass returns to the atmosphere the same carbon dioxide that the plants took in when they were growing and so can cut net emissions compared with fossil fuels.

Miscanthus needs little or no manufactured fertilizer and is harvested annually over a 15- to 20-year period.