Breakthrough science and innovation

N. Palmer (CIAT)

Measuring greenhouse gas emissions from burning rice straw

Southeast Asia

Following the rice harvest in Asia, smoke from burning rice straw drifts across the region, harming human health and adding greenhouse gases (GHGs) to the atmosphere. Farmers burn straw because it is a cheap and easy way of getting rid of stubble in the fields. What is not known, even though farmers have regularly burned off their fields for decades, is what emissions result from burning. Without this knowledge, it is not possible to calculate the total emissions over the entire rice production cycle, nor the total emissions from the agricultural sector. This gap in knowledge precludes comparing different ways of dealing with rice straw in order to reduce emissions.

Scientists assess the total carbon and nitrogen lost when rice straw is burnt – a common practice after the harvest in Asia

Scientists assess the total carbon and nitrogen lost when rice straw is burnt – a common practice after the harvest in Asia. IRRI

To fill this gap in knowledge, CCAFS scientists at the International Rice Research Institute (IRRI) set up experiments to study 3 aspects of straw burning. First, they measured the methane and nitrous oxide GHG emissions generated by burning rice straw. Second, they studied the effect of the moisture content of straw on the amount of GHGs emitted. Third, they assessed the carbon and nitrogen losses from burning.

When they analysed the results in 2014, scientists found that the more moisture the straw contains, the higher the methane emissions. And the higher the moisture content of the straw the more carbon is lost from burning. Levels of nitrous oxide emissions and nitrogen lost by burning are consistently low and are not affected by moisture content.

The results of these innovative experiments are important for measuring the global warming potential of rice production and assessing mitigation options by improving straw management practices. The findings will help agricultural advisors recommend how farmers can deal with rice straw in a sustainable manner that minimizes local air pollution and contributes to mitigating climate change.