Comparative assessment of using rice straw for rapid composting and straw mushroom production in mitigating greenhouse gas emissions in Mekong Delta, Vietnam and Central Luzon, Philippines

The study aimed to assess two alternative uses of rice straw (rapid composting and straw mushroom production) in mitigating greenhouse gas emissions in Mekong Delta, Vietnam and in Central Luzon, Philippines. The study was surveyed 417 farmer-respondents in addition to focus group discussion in Mekong Delta (O Mon and Cai Lay) and Central Luzon (Muñoz and Santo Domingo). Interviews with current adopters and key informants of rapid composting and straw mushroom production were also done in the sites in order of assess the current rice straw practices, describe farmers' awareness and perception and determine the factors affecting farmers' acceptance of the two alternative uses of rice straw. The greenhouse mitigation potential was estimated through the reduction of methane emission when shifting from the current rice straw practices to the alternative uses and then monetized through the carbon dioxide equivalent (CO2 eq). Economic feasibility was assessed by determining the net present values (NPV) of the incremental net benefit of the alternative uses. The survey shows that majority of the rice straw in Mekong Delta and Central Luzon was burned. In Mekong Delta, a small percentage of rice straw was used to grow mushroom, left in the field and used to feed cattle while rice straw in the Central Luzon was left in the field, used as feed for cattle and for mulching. The study also found that farmers have low awareness on the use of Trichoderma for rapid composting. The factors affecting the acceptability of the Trichoderma using the legit model show that household income and perceptions are significant factors of Mukong Delta and Central Luzon. Farm size is another significant factor in Central Luzon. For straw mushroom production, farmers have good awareness, however, the level of engagement was low. For factors affecting farmers' acceptance to grow straw mushroom, household income and household size are significant in Mekong Delta while household income, farm size and willingness to learn more about straw mushroom are significant in Central Luzon. Among rice straw uses, rapid composting and straw mushroom production emit less methane than other current uses (leaving or incorporating in the field, feeding cattle and burning). Growing mushroom gave the highest net benefit while leaving straw in the field give negative net benefit in both countries. The highest NPV and CO2 eq reduction were from shifting from dump burning to straw mushroom production (Mukong Delta) and shifting from leaving rice straw in the field to straw mushroom production (Central Luzon). Both yield higher NPV and CO2 eq reduction than shifting to rapid composting. To enhance adoption of rapid composting and straw mushroom production, the policy options that can be applied are: 1) upgrade farmers' knowledge about rapid compositing and straw mushroom production, 2) set up supply system of activators and mushroom spore, 3) conduct more research producing and applying rapid compost to paddy and other crops, especially non-flooded crops and improving straw mushroom techniques and spore quality, and 4) set up marketing activities for straw mushroom.