The starchy cassava root has long been an important ingredient in everything from tapioca pudding and ice cream to paper and animal feed.

But last year, 98 percent of cassava chips exported from Thailand, the world’s largest cassava exporter, went to just one place and almost all for one purpose: to China to make biofuel. Driven by new demand, Thai exports of cassava chips have increased nearly fourfold since 2008, and the price of cassava has roughly doubled.

Each year, an ever larger portion of the world’s crops — cassava and corn, sugar and palm oil — is being diverted for biofuels as developed countries pass laws mandating greater use of nonfossil fuels and as emerging powerhouses like China seek new sources of energy to keep their cars and industries running. Cassava is a relatively new entrant in the biofuel stream.

But with food prices rising sharply in recent months, many experts are calling on countries to scale back their headlong rush into green fuel development, arguing that the combination of ambitious biofuel targets and mediocre harvests of some crucial crops is contributing to high prices, hunger and political instability.