Rice is the staple food of more than 3.5 billion people—half of the world’s population—and 91% of it is grown and consumed in Asia. For every 4 tons of rice grain, 6 tons of straw are produced. In Asia, this amounts to about 550 million tons of straw and 110 million tons of husks each year. The husks are removed from the grains at a mill where they can be used as fuel. By contrast, rice straw remains in the fields after harvest and is costly to gather up. In flooded rice systems, where two to three crops are planted each year, long-term trials show that all aboveground crop residues can be removed without depleting soil carbon. Therefore, incorporating rice straw into the soil is not necessary and can be a major cause of methane emissions as its residues break down anaerobically.
To exacerbate the problem, incorporating straw into the soil delays soil preparation and the development of the next crop. Because of this, rice straw is often considered a waste product and is burned in the fields, resulting in airborne emissions hazardous to humans and the ecosystem.
The Rice Straw Project aims to assess alternative options in using rice straw to produce clean energy. Researchers in the U.K. and at IRRI are collaborating on four work packages:
Feedstock/logistical: Rice straw is a bulky and low-value material that is left in the field. The cost of handling and transporting it are high in terms of manpower, energy, and money.
Technological: Rice straw is an inconvenient material to use for fuel because of its physical and chemical properties. Little is known about technologies that can be used to convert it into a modern energy resource in the field. The project incorporates anaerobic digestion trials on rice straw, which is one promising option.
Social and institutional: It is important to understand the social context in which straw is produced and energy demanded. Focus groups are being held to assess the priorities, preferences, and responses of rice farmers, energy users, and local communities.
Dissemination: It is important to disseminate the information from the project among users such as farmers, NGOs, governments, and the international scientific community.