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[BEIJING] The burning of stalks in fields after harvests is a significant contributor to China's carbon dioxide emissions and other pollutants, according to a new research.

Burning has been widely adopted by Chinese farmers as an easy and cheap way remove stalks after harvests, despite the practice being banned by the government.

In a study published in the August issue of the Chinese Science Bulletin, Cao Guoliang, from the Centre for Atmosphere Watch and Services at the China Meteorology Administration, and colleagues estimated that burning stalks produced 210.2 million tons of carbon dioxide in 2000, the most recent year for official figures on China's total carbon dioxide emissions. This was 6.1 per cent of China's total emissions that year.

The researchers examined national and regional statistics on crop outputs, the use of stalks as cooking fuel in rural households and data on the extent of crop burning in different regions. They combined this with laboratory experiments and existing data on the emissions released from stalk samples of different crops.

They found that regions with larger crop outputs and higher average revenues burn more stalks in the field, as farmers here do not need them for cooking fuel or building fences.

The study revealed that other pollutants from burning stalks account for a significant proportion of the total pollution discharges in China. For example, stalk burning in 2000 accounted for 10.8 per cent of volatile organic compounds and 7.7 per cent of carbon monoxide.

Cao told SciDev.Net that while the proportion of emissions from burning stalks has likely lowered in recent years due to increased emissions from the energy industry, they still remain an important contributor to emissions.

He added that some farmers also believe burning stalks increases the fertilising capabilities of the field — though previous research has shown no significant effects.

Cao says that if low-cost ways to collect stalks and make them into biofuels or construction materials could be developed, there will be triple benefits: reduced pollutant emissions, reduced consumption of other energy resources and increased farmer incomes from selling stalks.

Reference: Chinese Science Bulletin 52, 1826 (2007)