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Rice is the most important cereal in Asia. However, it also results in the generation of large quantities of rice-derived residues (i.e., rice straw and rice husk). Due to the residues richness in lignocellulosic components, they potentially have considerable value in material and/or energy production without illegal burning in open fields. This work focused on investigating the thermochemical properties and inorganic/metal element contents of rice straw and rice husk. The former included proximate analysis, calorific value, thermogravimetric analysis (TGA) and energy dispersive X-ray spectroscopy (EDS). The latter covered the ten elements most relevant to their slagging/fouling indices. The results showed that they are suitable for energy use as biomass fuels, but rice husk was superior to rice straw because of the high silica content in the rice husk and the significant contents of potassium, sulfur and phosphorus in the rice straw. Using several slagging and fouling indices, the evaluation results were also consistent with their contents of inorganic elements or oxides. To increase the fuel properties of rice-derived residues, they could be pretreated with alkaline leaching, thus causing lower emissions of particulates and reduced slagging tendency when co-firing them with coal in industrial boilers. [ABSTRACT FROM AUTHOR]

Anaerobic digestion is applied to recover energy from rice straw (RS) which is a lignocellulosic agricultural residue produced in huge quantities in Asia and Africa. Because of the high solids content of this feedstock, high solids anaerobic co-digestion in batch mode must be further investigated. In this study, optimal operating conditions for the anaerobic co-digestion of RS with cow dung (CD) in batch mode, with and without leachate recirculation, were assessed under mesophilic temperature conditions. Preliminary experiments carried out in 2 L batch reactors confirmed that the concentration of RS in the mixture of substrates S0, in g VSRS/kg of mixture is an important parameter. Only batch reactors with the lowest S0 values (29 g VSRS/kg) produced biogas and rest of the reactors followed a long lag phase. The use of digestate from a previous batch as an inoculum was investigated with S0 values of 29 and 55 g VSRS/kg. Use of the digestate with S0 of 29 g VSRS/kg improved both initial degradation kinetics and the methane yield measured after 60 days. However, at S0 of 55 g VSRS/kg, the degradation kinetics were affected and after two months, 32 % of the biodegradable organic matter could not be eliminated. When leachate recirculation was performed in 6L leach-bed reactors (LBRs) with S0 between 30 and 65 g VSRS/kg, the highest methane yield was recorded at the lowest S0 value. It can be concluded that under batch mode, an RS concentration around 30 g VSRS/kg may be recommended for industrial applications. [ABSTRACT FROM AUTHOR]

Biohydrogen produced from agricultural waste through dark co-fermentation is an increasingly valuable source of renewable energy. Rice straw (RS) and pig manure (PM) are widely available waste products in Asia with complementary levels of carbon and nitrogen that together have a high biohydrogen production potential. However, no research has yet determined the ideal inoculum pretreatment method and mixing ratio for biohydrogen production using these resources. In this study, we tested biohydrogen production using three different inoculum pretreatment methods (acid, alkali and thermal) at five RS/PM ratios (1:0, 5:1, 3:1, 1:1 and 0:1, based on total solids). All three pretreatments promoted biohydrogen production with the increase of bioactivity of biohydrogen-producing organisms (compared with a control group), though acid was clearly superior to thermal or alkali. Using acid pretreatment and RS/PM ratio of 5:1 corresponded with a relatively low N H 4 + -N concentration (655.17 mg/L), a maximal cumulative biohydrogen production of 44.59 mL/g VSadded with a low methane production (<0.1%), a large butyric acid accumulation (1035.30 mg/L) and a biohydrogen conversion rate of 2.12%. The optimal pH for biohydrogen production from co-fermentation of RS and PM ranged from 5.0–5.5. [ABSTRACT FROM AUTHOR]

With the ever-increasing energy demands, fossil fuels are gradually depleting and eventually, these nonrenewable sources of energy will be exhausted. Hence, there is an urgent need to formulate alternative fuels that are both renewable and sustainable. Biomass is one of the reliable sources of energy because it is replenishable. Rice is the staple food in many countries, particularly in Asia. The number of paddy fields has increased tremendously over the years and is expected to increase in the future in response to the growing world population. This will lead to significant amounts of agricultural wastes annually, particularly rice straw. In some countries, open burning and soil incorporation are used to manage agricultural wastes. Open burning is the preferred method because it is inexpensive. However, this method is highly undesirable because of its detrimental impact on the environment resulting from the release of carbon dioxide and methane gas. Hence, it is important to develop an energy-harvesting method from rice straw for power generation. More studies need to be carried out on the availability and characteristics of rice straw as well as logistic analysis to assess the potential of rice straw for power generation. This paper is focused on reviewing studies pertaining to the characteristics and potential of rice straw for power generation, current rice straw management practices, and logistic analysis in order to develop a suitable energy-harvesting method from rice straw in Malaysia. [ABSTRACT FROM AUTHOR]

In Southeast Asia and Vietnam, rice residues are routinely burned after the harvest to prepare fields for the next season. Specific to Vietnam, the two prevalent burning practices include: a). piling the residues after hand harvesting; b). burning the residues without piling, after machine harvesting. In this study, we synthesized field and laboratory studies from the literature on rice residue burning emission factors for PM 2.5 . We found significant differences in the resulting burning-practice specific emission factors, with 16.9 g kg −2 (±6.9) for pile burning and 8.8 g kg −2 (±3.5) for non-pile burning. We calculated burning-practice specific emissions based on rice area data, region-specific fuel-loading factors, combined emission factors, and estimates of burning from the literature. Our results for year 2015 estimate 180 Gg of PM 2.5 result from the pile burning method and 130 Gg result from non-pile burning method, with the most-likely current emission scenario of 150 Gg PM 2.5 emissions for Vietnam. For comparison purposes, we calculated emissions using generalized agricultural emission factors employed in global biomass burning studies. These results estimate 80 Gg PM 2.5 , which is only 44% of the pile burning-based estimates, suggesting underestimation in previous studies. We compare our emissions to an existing all-combustion sources inventory, results show emissions account for 14–18% of Vietnam's total PM 2.5 depending on burning practice. Within the highly-urbanized and cloud-covered Hanoi Capital region (HCR), we use rice area from Sentinel-1A to derive spatially-explicit emissions and indirectly estimate residue burning dates. Results from HYSPLIT back-trajectory analysis stratified by season show autumn has most emission trajectories originating in the North, while spring has most originating in the South, suggesting the latter may have bigger impact on air quality. From these results, we highlight locations where emission mitigation efforts could be focused and suggest measures for pollutant mitigation. Our study demonstrates the need to account for emissions variation due to different burning practices. [ABSTRACT FROM AUTHOR]

An in-situ, rapid, and low cost management of the huge amount of rice straw (RS) is a great challenge in south Asia. On the other hand, mobilisation of soil phosphorus (P) from inorganically fixed pools could improve its efficiency sustainably. To solve these problems concurrently this study was conducted to test whether the application of RS+P solubilizing microbes (PSMs) could solubilise a significant amount of the fixed P from soil and they could influence P transformation, silicon (Si) concentration, organic acid (OA) production, and enzyme activity in the rhizosphere to improve the yield of wheat. The specific objective of this study was to identify the sufficient amount of RS for solubilisation of fixed P to meet its demand to crops and develop a fertiliser application strategy accordingly. Application of RS (at 12 Mg ha−1) +PSM could solubilise ∼2.96–3.26 % of inorganically fixed P in soil depending on soil temperature. It reduced the hysteresis effect by 10 % over control. Oxalic acid, citric acid, formic acid, malic acid, and tartaric acid could be identified in the rhizosphere of wheat. Application of RS (at 12 Mg ha−1) +PSM+ 75%P enhanced the activities of dehydrogenase, alkaline phosphatase activity, cellulase, and peroxidase by ∼1.80, 1.79, 2.14, and 1.40 times over control in the wheat rhizosphere, respectively, at maturity stage. It also enhanced the plant available P by 21 % over mineral fertiliser application during wheat growth. It also boosted Si concentration by 61 % over control in rhizosphere. Application of RS (at 12 Mg ha−1) +PSM+ 75%P resulted in a 45 % greater grain yield of wheat than control. It also improved root length, volume, and P uptake by 1.74, 2.40, and 1.61 times respectively over control. Path analysis indicated that P solubilisation by Si and OAs significantly contributed to P availability in the rhizosphere of wheat. Hence, RS (at 12 Mg ha−1) +PSM+ 75%P of mineral P fertiliser could be recommended to the cultivators for saving 25% P fertiliser without affecting yield. • Ability of rice straw (RS)+PSM to solubilise inorganic P in wheat rhizosphere studied. • Application of RS+PSM could solubilise ∼3.3% of inorganic P. • It resulted in a 45 % greater grain yield of wheat than control. • It improved root length and volume by 1.74 and 2.40 times respectively over control. • RS+PSM enhanced NaHCO 3 -P by 19–30 % over mineral P application at wheat harvest. [ABSTRACT FROM AUTHOR]

Rice is a conventional crop that is produced majorly in the South and the South-East regions of Asia, leading to the generation of a considerable amount of biomass (Rice Straw) in the fields during the harvesting process. Whereas, husked rice, rice bran and broken rice are handled carefully during the processing of rice, however, rice straw is left in the agricultural fields and subjected to open-field burning for the easiest way to get rid of this waste. During the burning process, particulate matter (PM 2.5 , PM 10) and Greenhouse gases (CO, SO x , NO x) are emitted to the atmosphere and tend to cause an adverse effect on soil characteristics, human health and the environment. Considering these problems, many studies have been carried out for the valorization of rice straw in the various technologies as a raw material for composting, paper production, power generation, mushroom production, gasification and pyrolysis, construction material, pellet production, silica extraction, feed for ruminants, biofuel production, as an adsorbent and biochar production. The present paper aims to review the aforementioned technologies on the basis of different parameters for the generation of value-added products. The data presented in the paper is expected to aid local authorities, researchers and stakeholders to improvise the current practices or to invent new possibilities for the sustainable management of rice straw. • The potential use of rice straw in the different applications is elaborated. • The environmental impacts and mitigation strategies for the open-field burning of rice straw are discussed. • The future predictions along with economic aspects associated with the sustainable utilization of rice straw are presented. • The advantages and disadvantages involved in the further inventions to reduce the impact of rice straw are explained. [ABSTRACT FROM AUTHOR]

Volvariella volvacea, the edible straw mushroom, is a highly nutritious food source that is widely cultivated on a commercial scale in many parts of Asia using agricultural wastes (rice straw, cotton wastes) as growth substrates. However, developments in V. volvacea cultivation have been limited due to a low biological efficiency (i.e. conversion of growth substrate to mushroom fruit bodies), sensitivity to low temperatures, and an unclear sexuality pattern that has restricted the breeding of improved strains. We have now sequenced the genome of V. volvacea and assembled it into 62 scaffolds with a total genome size of 35.7 megabases (Mb), containing 11,084 predicted gene models. Comparative analyses were performed with the model species in basidiomycete on mating type system, carbohydrate active enzymes, and fungal oxidative lignin enzymes. We also studied transcriptional regulation of the response to low temperature (4°C). We found that the genome of V. volvacea has many genes that code for enzymes, which are involved in the degradation of cellulose, hemicellulose, and pectin. The molecular genetics of the mating type system in V. volvacea was also found to be similar to the bipolar system in basidiomycetes, suggesting that it is secondary homothallism. Sensitivity to low temperatures could be due to the lack of the initiation of the biosynthesis of unsaturated fatty acids, trehalose and glycogen biosyntheses in this mushroom. Genome sequencing of V. volvacea has improved our understanding of the biological characteristics related to the degradation of the cultivating compost consisting of agricultural waste, the sexual reproduction mechanism, and the sensitivity to low temperatures at the molecular level which in turn will enable us to increase the industrial production of this mushroom. [ABSTRACT FROM AUTHOR]

Abstract: Burning of agricultural residues, such as rice straw, is a sizeable source of smoke aerosol particularly in Asia. During a field study on the subtropical island of Taiwan ambient aerosol was examined for seasonal patterns in terms of size-resolved chemical composition. Ambient concentrations, size distributions and diagnostic ratios of three anhydrosugars (levoglucosan, mannosan, and galactosan), used as molecular tracers for biomass burning, are reported here. Levoglucosan concentrations showed a strong seasonal dependence in the ambient levels as well as size distributions. During the wet (summer monsoon) season levoglucosan was observed with average concentrations of 437, 882 and 1116ngm−3 in PM2.5, PM10 and TSP, respectively. In contrast, winter/dry season levoglucosan levels were lower with 436, 448, and 559ngm−3 on average in PM2.5, PM10 and TSP, respectively. The particle-size distributions were characterized by a drastically increased coarse (PM2.5−10) fraction in the summer season, which was 36 times higher than during winter, likely due to higher fuel moisture content as well as enhanced condensation, coagulation and hygroscopic growth of the relatively fresh smoke particles derived from rice straw burning. Furthermore, the relative abundance of the three anhydrosugars was examined for characteristic signatures in respect to different types of biomass. [Copyright &y& Elsevier]

For the first time, a versatile, novel and environmentally-friendly aerogel was successfully fabricated from rice straw – one of the most abundant agricultural waste in South-east Asia. The final product is able to be applied in a wide range of applications including oil-spill cleaning, thermal insulation and acoustic absorption. The fabrication process is simple, cost-efficient and totally green without disposal of harmful by-products into the environment. Specifically, rice straw fibers were dispersed along with reinforcers (PVA or cationic starch) followed by freeze-drying to form shaped aerogels. Those samples were then turned into hydrophobic by coating with MTMS using chemical vapor deposition (CVD) method to produce aerogels with exceptional water repellency (WCA exceeding 1500). The morphology, pore structure and physical properties of the aerogels were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), thermal conductivity, water contact angle (WCA) measurements, oil adsorption and sound absorption measurements. The aerogel samples exhibit extremely low densities (0.05–0.06 g/cm3), high porosities (~97%), excellent heat reduction properties with low thermal conductivities (0.034–0.036 W/m.K), good mechanical properties (Young modulus up to 47 kPa) and oil adsorption efficiency proven with the capacity up to 13 g/g. In addition, huge potential of rice straw aerogels in sound absorption applications is also demonstrated with high noise reduction coefficient (up to 0.6). The samples still retain their thermal insulation, sound insulation capability and hydrophobicity after 2-month exposure in ambient environment. Image 1 • Rice straw is converted into aerogel by a simple and efficient fabrication process. • PVA and cationic starch are used as crosslinking agents. • Rice straw – PVA aerogel is the strongest sample. • Exceptional hydrophobicity is found for the aerogels with high water contact angles. • The aerogels have high potential in thermal insulation, sound absorption and oil spill cleaning. [ABSTRACT FROM AUTHOR]

Point pollution of pesticides originating from the washing of spraying machines could be controlled by biobed system and it is in use in temperate countries. The biobed system is yet to be established in tropical countries. An indigenous biobed system was prepared using local resources like rice straw, farm yard manures (FYM) and paddy field soil to suit the tropical climate. Lowermost 3 cm layer of the biobed system was filled with rice husk biochar to prevent leaching of pesticides from the system. This model system was tested with high doses of imidacloprid (178 mg/column), a commonly used pesticide against number of insect-pests in different crops, for its degradation. The bio-mix trapped a major part of the imidacloprid on the top most layer of the biobed column and only a very small part of imidacloprid recovered from the leachate. The biobed system could degrade 70.13% of applied imidacloprid within 15 days of the experiment and only 5.27% of the total pesticide recovered 90 days after incubation. Addition of biochar layer adsorbed imidacloprid from the outgoing leachate from the biobed column. Biomixture boosted microbial activity more particularly fungal population, which might be responsible for imidacloprid degradation. Microbial biomass carbon, and soil enzymes indicated faster dissipation of imidacloprid from the top layer of the biobed. This simple but efficient biobed system using local resources can fulfill the need of the small and marginal farmers of Asian countries for pesticide decontamination., (Copyright © 2020 Elsevier Ltd. All rights reserved.)