Worries about feeding the world's most populous nation could limit the growth of China's environmentally-friendly biofuels industry, officials and executives said on Friday.
Biofuels made from agricultural products ranging from sugarcane and wheat to waste oil from cooking, are becoming increasingly attractive as crude prices climb.
Beijing bureaucrats, concerned about rural poverty and rising oil imports, are attracted to a technology that offers a chance to cut dependence on foreign petroleum and boost the value of farmers' output.
Its biofuel programme, originally developed in part to help tackle surplus corn stocks in the north-east, involves subsidised production of over 1 million tonnes of the fuel.
Five provinces already blend 10 percent of ethanol into all their gasoline and over 20 cities scattered across the country are also pioneering the "gasohol" mix.
But even with the additional advantage of helping clear city skies clouded by smog - up to 70 percent caused by car emissions, according to Gao Haiyang, from China's Automotive Technology and Research Centre - the programme is unlikely to expand across the country just yet.
"Basically this country has such a large population that the top priority for land use is food crops ... and at the moment they don't want to exacerbate competition for new materials," said Sergio Trindade, president of SE2T International.
China has long been concerned about its food security, and although it has abandoned a Maoist-era insistence on self-sufficiency, is still keen to meet much of its needs with domestic production.
China's scientists hope that farming by-products like straw and corn stalks, or even forest residues, could offer a longer-term solution.
These are usually burnt, but contain cellulose that can be broken down into ethanol - although currently it is too expensive to be commercially viable.
"Cellulose provides a renewable fuel option without concerns about food safety and land requirements," said Li Shizhong, Professor at the Biomass Engineering Centre at the China Agricultural University.
He said China was capable of developing cheap but reliable technology in as little as a decade, and called for a national target of 12 million tonnes of ethanol output by 2015 to 2020.
With the domestic market for fuel blending estimated at around 5 million tonnes, he suggested that some of the extra production could be channelled to the chemicals industry as a feedstock for ethylene.