Wasted Chinese straw 'could be food and energy source'
[BEIJING] A pilot project that has turned waste straw into rich cattle food and biogas could be expanded to help improve food security and rural energy supply across China, says its leader.
Jiang Gaoming, an ecologist at the Chinese Academy of Sciences, initiated the programme in Pingyi County, in eastern China in an effort to find a better use for the 700 million tonnes of straw produced annually in China, of which 37 per cent is burned. Less than a quarter is used as food.
By adding bacteria to the waste straw his team was able to ferment it to produce "bread grass". This has been used to raise cattle in the village. Dung from the cattle is turned into methane — a source of electricity and cooking fuel — at one of 120 household biogas plants built under houses in the village.
So far 30 cattle are being raised in the village. Interim results from the project show that beef cattle weighing 200 kilograms grew to 420 kilograms in seven months when fed bread grass. A family with three cattle can earn more than 7,000 Chinese yuan (US$1,025) per year from selling the beef, says Jiang.
His goal is to raise 200–300 cattle, build 200 biogas plants, and set up a small biogas power plant for the whole village.
In addition, Jiang estimates that an amount of fertiliser equal to around twice the annual consumption in China can potentially be generated from the sediment and liquid waste from the biogas plant.
But the model has financial obstacles to tackle. With average income less than 4,600 yuan per year in Pingyi County, many farmers cannot afford to buy calves. And large-scale raising of livestock cannot be maintained in places like Pingyi, where urbanisation is decreasing the amount of available arable land.
"We are appealing to the government to provide microcredit loans for the farmers to buy the calves at the beginning," Jiang says. And according to a national plan on the overall use of land passed by the State Council of China last August, the Chinese government has legally protected 120 million hectares of farmland.
Wang Kun, a professor of animal husbandry at China Agricultural University, says Jiang's practice is a good example of ecological agriculture. But considering the low-protein and high-fibre quality of straw, he says, other high-protein food such as clover must be added to guarantee nutrition for the cattle.