The negative effects of open-field rice straw burning on the environment and human health are well documented in local and international literature. Farmers have thus been encouraged to refrain from burning rice straw and adopt more environment- and human-friendly rice straw management practices. This research project aimed at assessing the environmental consequences of rice straw burning and other straw management practices in terms of greenhouse gas (GHG) emissions, and evaluating the cost-effectiveness and adoption of selected rice straw management alternatives. The study evaluated emissions of methane (CH4) and nitrous oxide (N2O) gases only since carbon dioxide (CO2) emissions from rice cultivation and associated practices are assumed to be reabsorbed during the next growing season. Given the average yield and total rice area of the country by season and ecosystem, and the current use of rice straw based on our survey of farmers, rice stubble and straw contribution to CH4 and N2O emissions in paddy fields is around 16 M tons carbon dioxide equivalent 1 (CO2-eq) in the base year. Incorporating stubble less than 30 days before crop establishment appears to be the largest contributor, accounting only for the current year. On a per hectare-basis and considering a time horizon of five years with associated assumptions on cost savings and secondary benefits, incorporating stubble more than 30 days before crop establishment, and incorporating composted rice straw in the field yielded the lowest cumulative CH4 and N2O emissions. The most cost-effective option for farmers is to incorporate stubble and straw in the soil more than 30 days before crop establishment. Rapid straw composting and incorporation of rice straw compost entails much higher additional cost but it also significantly mitigates GHG emission, hence it is the next most cost-effective option. Incorporating rice stubble and straw less than a month before crop establishment, on the other hand, appears to result in a net increase in ton CO2-eq given the assumed time horizon. Literature points to the potential of rice straw as raw material for power generation and bioethanol production and the corresponding reduction in GHG emissions, but this study has not evaluated the cost-effectiveness of these options, hence, this is recommended for further study. The estimated GHG emissions are generally indicative and the economic analysis must be interpreted in relative terms. Further study on water management and tillage options as mitigation options is recommended for a broader perspective useful for farmers, policy-makers and other rice stakeholders. A mix of socio-economic, farm, and awareness and attitude variables determine why farmers choose to burn, incorporate, or remove rice straw. Training on rice production for farmers, increasing the demand for rice straw for other uses, developing options for reducing the cost of collection and transportation of rice straw, and intensifying information campaigns and drives regarding environmental regulations and policies are recommended.
