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Managing rice straw remains a challenge in Asia where more rice, and hence, more straw, is grown each year to meet rising demand. The widespread burning of rice straw is a major contributor to dangerously high levels of air pollution in South-and Southeast Asia associated with health issues. At the same time, researchers, engineers, and entrepreneurs are developing a range of alternative uses that turn rice straw into a commodity around which sustainable value chains can be built to benefit rural people. The best alternative to burning rice straw in any one location depends on context. However, available information remains scattered in different media and no publication yet exists that helps people learn about, and decide between, rice straw management options. This book provides a synthesis of these options and integrates knowledge on relevant areas: sustainable rice straw management practices, rice straw value chains, and business models. The book is also based on new research and practice data from research organizations and innovators in Vietnam, the Philippines, and Cambodia.

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Ninety percent of the world's rice is produced and consumed in Asia. Millions of rice producers are resource-poor farmers with a rice area of less than one hectare. Yield increase and the introduction of double-cropping systems have ensured that rice production has kept up with an increasing demand. However, the increased quantities of grain and the second harvest, which is often in the wet season, have increased the problems in traditional postharvest systems. This can be particularly severe in the humid tropics, where post-harvest losses occur because of outdated management practices and technologies, and delays in post-harvest operations. Fungal infestation of rice grains can lead to discoloration, which results in price reductions in most markets. This can also result in rice being contaminated with mycotoxins, which is less visible to consumers. Contamination with ochratoxins, aflatoxins, and other mycotoxins have occasionally been reported in the literature. In the past, this was not seen as a significant problem and the focus was on other commodities such as maize and peanuts. However, recent studies and a massive recall of food products in Japan in September 2008, including sake, shoshu, and rice crackers made from imported rice from China and Vietnam, which were tested positive for aflatoxins, and also for pesticide residues, have renewed interest in looking at mycotoxin problems in rice. Exploratory studies in the Philippines compared best practice post-harvest management with the traditional management practices often used by smallholder farmers and small processors. It was concluded that synthesis of aflatoxin B1 is very likely in suboptimal post-harvest systems, with levels far above legislative limits. This indicates that there might be a considerable mycotoxin problem in rice from smallholder post-harvest operations. Improved post-harvest management options and technologies are available for diversified small-scale post-harvest systems. Small-scale combine harvesters, affordable and simple mechanical dryers and hermetic storage systems can help to avoid delays in the post-harvest chain and thus reduce mycotoxin contamination of rice. The development of strategies to scale out these improved practices and technologies to a large number of smallholder farmers will continue to be the main challenge.

The research provided scientific evidences for improved rice straw management. Rice cultivation with in-field burning of rice straw is the worst option with the lowest energy efficiency and highest air pollution emission. This article comprises a comparative assessment of energy efficiency and the environmental footprint of rice production using four different rice straw management scenarios, namely, straw retained, straw burned, partial straw removal, and complete straw removal. Paddy yield, grain quality, and energy balance were assessed for two seasons while greenhouse gas emissions (GHGE) were measured weekly starting from land preparation through to the cropping and fallow period. Despite the added energy requirements in straw collection and transport, the use of collected rice straw for mushroom production can increase the net energy obtained from rice production systems by 10–15% compared to burning straw in the field. Partial and complete removal of rice straw reduces GHGE by 30% and 40% compared to complete straw retention, respectively.

The introduction of combine harvesters has made rice straw collection a major challenge and has brought bottlenecks to the rice straw supply chain. Due to this and the lack of knowledge on the straw's alternative uses, farmers burn the biomass in the field for ease of land preparation. This practice creates negative impacts on human health and the environment. However, as an alternative to burning, some Asian countries are developing increasing demands for rice straw for mushroom production, cattle feedstock, power generation, and building materials. Mechanized straw collection has become necessary to increase capacity and to lower transportation costs. Baling machines can collect and compact rice straw in varying forms and densities. In the Mekong River Delta of Vietnam, adoption of rice straw balers have significantly improved rice straw management. A baler hauled by a 30-HP tractor has a collection capacity equal to five people, solving the labor shortage problem in rice straw collection. In addition, the volumetric weight of mechanically compacted straw bales is 50-100% higher than that of loose straw, which significantly reduces handling and transportation costs. High-density compaction (e.g., stationary compaction, briquetting, and pelletizing) can further increase the volumetric weight of baled straw from 400% to 700%, reducing transportation costs by more than 60%. Mechanized rice straw collection and densification have contributed to improvement of the supply chain and resulted in sustainable management of rice straw. This chapter discusses the different technologies for rice straw collection, enumerating

Laser-controlled land leveling (LLL) can help improve rice production's spatial and temporal management, leading to optimized water and crop management. This research resulted in sustainable performance indicators to illustrate that LLL is a sustainable technology for rice production. The assessment was conducted in Cambodia, the Philippines, Thailand, Vietnam, and India. Benefits of LLL include saving land use, water, and agronomic inputs, increasing yield, and decreasing postharvest losses resulting in saving energy of 3.0–6.9 GJ ha−1 and decreasing emissions by 1151–1486 kg CO2-eq ha−1. Additionally, LLL application can obtain a net profit of USD 52–84 ha−1 per rice production season in the countries studied. The result demonstrated that LLL is a sustainable technology as well as strongly supports sustainable rice production. The study would lead to better adoption of this technology through its evidence-based promotion.