Product line 4.2. Innovative uses of rice straw and rice husks
Each year, about 550 million tons of rice straw and about 5 and 110 million tons of husks are produced in Africa and Asia, respectively. Although rice residues are major by-products of rice production, they generally have little or no commercial value. In intensive systems, where two or three crops are grown each year, the time for incorporated residues to decompose is very short and the remaining residues may disrupt soil preparation, crop establishment, and early crop growth. Although residue retention is essential for sustainable management of more diversified (rice-upland crops) systems, long-term research has shown that residue removal has no negative consequences for the productivity, sustainability, and soil health of intensive double- and triple-cropping rice monoculture systems. However, where practiced, burning of rice residues causes severe air pollution in some regions, but, the alternative, incorporation into the soil, is a major source of methane emissions from rice fields. Therefore, in this product line, research will be conducted on innovative uses of rice straw and husks, including modifications of the rice plant. This will generate new income opportunities for the rice-farming sector and help to mitigate the effects of climate change.
(1) Develop tools to select for high digestibility of rice straw through understanding the chemical composition and then incorporate selection tools for highly digestible straw into breeding programs. This work will be carried out by ILRI in South Asia, under CSISA. (2) Activities include an inventory of existing bioenergy technology designs; evaluation of a range of concepts for bioenergy production using rice husks or rice straw; adaptation of promising concepts to local conditions and rice straw, and verification on a pilot basis; characterization and management options for biochar usage for carbon sequestration, nutrient recycling, and increased soil fertility and soil health; energy balance, life-cycle analysis, and the carbon footprint for selected bioenergy/biochar systems established; and development of a road map for participation in clean development mechanism (CDM)/carbon trading. (3) Improve rice mills to obtain better separation of husk and bran during milling. (4) Evaluate (i) a range of concepts for the production of biomaterials using rice husks and/or straw and (ii) the commercial viability of these products in sub-Saharan Africa.
4.2.1 Rice straw with increased digestibility for feeding to livestock
4.2.2 Climate change mitigation through renewable, profitable, and sustainable energy production and carbon sequestration options based on rice residues
4.2.3 Innovative, profitable, and sustainable processing options for rice husks and rice straw
4.2.1 ILRI and IRRI scientists will collaborate with farmers in South Asia to determine indicators for suitable rice straw quality for use as a fodder. Both partners will then screen a range of cultivars for the desired traits, and provide rice breeders with a tool to select for these traits. Promising lines will then be recommended to NARES partners in South Asia for further evaluation and use.
4.2.2 IRRI and Cirad will conduct an initial desk study on available bioenergy technologies for crop/rice residues. Together with AfricaRice, AIT, and suitable NGOs or private-sector partners, the most suitable system(s) will be analyzed in detail on a pilot basis. IRRI in collaboration with NARES and an ARI will analyze the integration of bioenergy/biochar systems in rice-based cropping systems. Life-cycle assessment, carbon footprint analysis, and concepts for carbon trading will be developed with Cirad and other suitable partners.
4.2.3 AfricaRice and Cirad will determine the feasibility of developing commercially viable products from rice husks and rice straw in partnership with the private sector.
Tools for selecting for improved digestibility will be used in the rice breeding process of theme 2, as well as for public- and private-sector breeding efforts, so that the trait is mainstreamed into South Asian varieties. The product of those efforts, rice straw with improved digestibility, will be an attractive, self-spreading technology because many smallholder farmers in South Asia are already using straw for feeding livestock. However, competing demands for its use as feed or concerns about soil health may limit adoption in some areas.
The principal audience for feasibility work on bioenergy will be agencies involved in setting standards for carbon finance, so that appropriate standards can be developed for markets for averted emissions. Uptake of bioenergy/biochar technologies requires that the price of the energy produced is competitive on the local market, that the emissions and by-products do not harm the environment, and that by-products from bioenergy production can have additional value such as for carbon sequestration or nutrient recycling. There will be close linkages with product line 4.1. Accelerated impact requires linkages with investments in clean energy. Uptake will be driven by the private sector and NGOs with expertise in that area. For new uses of rice milling by-products, the next users, who conduct local adaptation work, are in national research systems, whereas important intermediate users include private-sector producers of postharvest equipment. The final users of that equipment are processors and small enterprises that will use by-products as inputs.
PL 4.2 currently receives little funding. It is an area in GRiSP in which we gradually wish to build up more expertise and thus also invest more, but also seek substantial co-investments from partners. Product 4.2.1 is currently funded by CSISA; annual investments of $0.5 million are required to support 4.2.2. Product 4.2.3 in Africa is expected to be funded by CIDA.