Last updated: April 2016
Approximately 600 million tonnes of CO2 (equivalent of methane) are thought to be emitted from rice paddies globally, equal to “1.2% of total global emissions”, at least 10% of agricultural emissions and about “three times the footprint of all cement produced in Europe”. This value does not even account for the fertilisers used during rice production (approximately 1 tonne of fertiliser is used for every 3 tonnes of rice produced), the agricultural machinery used or the transport emissions released to bring rice to your dinner table.
On the flip side, by 2050 the International Food Policy Research Institute (IFPRI) predicts that rice prices will have increased 32-37% as a result of climate change, due to predicted yield decreases and crop damage caused by extreme weather events and sea level rise.
Why do rice paddies release methane?
Rice is typically grown in flooded fields (paddies), which result in oxygen being prevented from entering the soil. This creates anaerobic (without oxygen) soil conditions, which are perfect for methane-producing bacteria. Methane escapes into the atmosphere through gas spaces in the rice’s roots and stems, and bubbles up through the soil and water.
Vietnamese woman transplanting rice in a flooded paddy along the Red River near Haiphong, Vietnam. Photo credit: Steve Estvanik
When drained, rice paddies release less methane. However, if fertilisers have been over-applied or available soil nitrogen is higher than the plant needs (due to the inefficient application of fertilisers), drained paddies potentially emit increased levels of nitrous oxide, another potent greenhouse gas (GHG). Effective water and nutrient management are therefore key to reducing rice’s GHG emissions.
Rice’s role in a sustainable food future
A growing body of evidence suggest that rice’s methane emissions can be significantly reduced through changes in production methods alone.
1. Interrupting or reducing periods of flooding in paddy fields can reduce methane emissions released by soil bacteria, in some cases by up to 90%. A number of methods including mid-season drainage and sowing seeds directly into dry fields can play a role in reducing both GHG emissions and fresh water use. (Rice production uses more than 30% of the world’s irrigation water).
2. Increasing rice yields on existing farmland can help prevent agricultural expansion and associated land-use change. Varieties of rice that can cope with higher temperatures (predicted with climate change) should be cultivated. Production methods such as System of Rice Intensification (SRI) could all assist in increasing yields.5 (SRI is a method of rice production that has been developed by smallholder farmers around the world. It focuses on improving soils and the health of plants rather than altering seed which has been the main focus of scientific research for years. For example, SRI involves keeping soils moist but not flooded, using organic matter as fertilisers rather than artificial fertilisers, spacing healthier plants farther apart, weeding between rice plants, and ploughing the soil between plants to increase oxygen in the soil).
However, technical barriers and inconsistent results regarding the benefits of the above systems currently prevent widespread adoption.
Where can I buy ‘sustainable rice’?
In short, you can’t. Of all the companies covered in our product guide to rice very little information about rice production methods was found, with the exception of those companies that offer organic rice products. And even organic certification does not ensure practices such as mid-season drainage are used. Only Mars stated its aim of sourcing 100% of its rice sustainably by 2020, based on the first ever global standard for sustainable rice6 – launched in October 2015 by The Sustainable Rice Platform (SRP).
The SRP is a “multi-stakeholder partnership [of public sector, private sector and NGO members] that aims to promote resource efficiency and sustainability both on-farm and throughout the rice supply chain”. SRP’s 29 members at the time of writing included Bayer, Mars Foods, Syngenta, the Rainforest Alliance and UTZ certified.
Currently no company covered in our guide to rice meets the SRP’s standards or is commercially cultivating rice using the methods described above.
What can I do?
Globally reducing our intake of rice and replacing it with more local and lower-carbon staples such as wheat or barley, is one action we can take toward lower-carbon diets.
However, it is important to remember the social implications of such a decision. Rice is not only a staple food for 3.5 billion people and a key source of income for millions of smallholder farmers, but has become integrated into the cultures of many rice-producing countries and is even considered sacred in the traditional societies of South East Asia.
In the long term companies should be pressured into pledging to source more sustainable rice and supporting initiatives that make this possible. Writing to companies and letting them know your thoughts can play a part in making this happen.
Top tips for using less energy and wasting less when cooking rice
Pre-soak rice for at least 30 minutes before cooking to help reduce cooking time.
Match your pan size with the hob size, flame or hot plate to reduce heat loss.
Use approximately one and a half cups of water for every cup of white rice and two cups of water for every cup of brown rice.
Use an electric rice cooker, pressure cooker or saucepan with its lid on, to reduce energy use.
Turn off or lower the heat when the water starts to boil and leave until all water is absorbed (and the rice is cooked).
If you have a choice, gas is preferable to electric hobs in terms of carbon dioxide emissions, unless you only use renewable energy. Gas hobs result, on average, in 170g CO2 per use compared to 320g CO2 per use for electric hobs.
Don’t bin leftover rice! Cool it down quickly by plunging the pan into a bowl of cold water (to prevent the bacteria Bacillus Cereus from flourishing) and use leftover rice to make stuffed vegetables, a cold salad or fried rice balls.