Rice straw is a rice by-product produced when harvesting paddy. Each kilogram of milled rice produced results in roughly 0.7-1.4 kilos of rice straw depending on varieties, cutting-height of the stubbles, and moisture content during harvest. Rice straw is separated from the grains after the plants are threshed either manually, using stationary threshers, or more recently, by using combine threshers.
The rapid introduction of combine harvesters is a game changer as combines spread rice straw in the field, which gives options in collecting them. Manual collection is unprofitable because of the high labor cost. Incorporation in the soil is also not possible in systems with two to three crops per year because the turnaround time is too short for decomposition. These constraints lead widely to farmers burning the rice straw directly in the field, causing the release of greenhouse gas emissions and human health problems. With the development of recent technologies, rice residues can be processed and managed with better practices. Scalable processing and management options of rice straw can be classified as in-field and off-field options.
The in-field management choices of rice straw such as open-field burning and incorporation can have both positive and negative impacts on the efficiency and sustainability of rice production. Management of rice straw influences the energy and nutrient balance, efficiency of fertilizer inputs, emissions of methane and atmospheric pollutants, and the pest and disease risks within rice agro-ecosystems. Changing social, climatic, environmental, and economic circumstances, particularly in Asia, are driving transformations in rice agro-ecosystems that will undoubtedly result in changes in the in-field residue management strategies of rice farmers.
More details about in-field management can be found in this link:
Off-field rice straw management includes removing rice straw from the field to use for other purposes. Besides using rice straw for bioenergy production, rice straw can be used for other non-energy purposes such as growing mushrooms, cattle feed, mulching for other crops, high-end, and industrial material production using silica contained in rice straw.
More details about off-field options can be found in this link
- How does burning of rice straw affect CH4 and N2O emissions? A comparative experiment of different on-field straw management practices, detailed in publication: http://www.sciencedirect.com/science/article/pii/S0167880916306302.
- Energy efficiency and cost-benefits of rice straw mechanized collection, detailed in publication: http://www.sciencedirect.com/science/article/pii/S0378429016302854.