Rice straw-wood particle composite for sound absorbing wooden construction materials

In this study, rice straw-wood particle composite boards were manufactured as insulation boards using the method used in the wood-based panel industry. The raw material, rice straw, was chosen because of its availability. The manufacturing parameters were: a specific gravity of 0.4, 0.6, and 0.8, and a rice straw content (10/90, 20/80, and 30/70 weight of rice straw/wood particle) of 10, 20, and 30 wt.%. A commercial urea-formaldehyde adhesive was used as the composite binder, to achieve 140-290 psi of bending modulus of rupture (MOR) with 0.4 specific gravity, 700-900 psi of bending MOR with 0.6 specific gravity, and 1400-2900 psi of bending MOR with a 0.8 specific gravity. All of the composite boards were superior to insulation board in strength. Width and length of the rice straw particle did not affect the bending MOR. The composite boards made from a random cutting of rice straw and wood particles were the best and recommended for manufacturing processes. Sound absorption coefficients of the 0.4 and 0.6 specific gravity boards were higher than the other wood-based materials. The recommended properties of the rice straw-wood particle composite boards are described, to absorb noises, preserve the temperature of indoor living spaces, and to be able to partially or completely substitute for wood particleboard and insulation board in wooden constructions.     

Mechanical and thermal properties of particle boards made from farm residues

Five farm residues were used for the manufacture of low-density particle boards in a hot platter press using urea formaldehyde as the binding material. Mechanical and thermal properties of the boards were evaluated. The maize-cob board was superior to other boards in mechanical and screw/nail holding strength, suggesting its use for interior applications, while paddy-straw board and coconut-pith board were found to be suitable for insulation purposes.     

Composite boards from guar and sorghum (Dura) stalks

Laboratory trials were carried out to determine the suitability of guar and sorghum stalks from Sudan as basic materials for composite insulation boards manufacture using cement as binder. Lignocellulosic material-to-cement ratios of 1:15 and 1:2 were used. The results show that these raw materials could successfully be used for insulation boards, with density of 530–700 kg/m³, satisfactory strength, and very good heat-insulation properties making them suitable for building.     

Production and characterization of cellulases and hemicellulases by Acremonium cellulolyticus using rice straw subjected to various pretreatments as the carbon source

Cellulases and hemicellulases are key enzymes in the production of alternative fuels and chemicals from lignocellulosic biomass-an abundant renewable resource. Carbon source selection is an important factor in the production of cellulases and hemicellulases. Rice straw--a potential ethanol source--has recently gained considerable interest in Asian countries. Here, we investigated the production of cellulases by using rice straw subjected to various pretreatments as substrates in order to produce cellulases at low costs; we also identified the enzymes' characteristics. Rice straw cutter milled to <3mm was pretreated by wet disk milling, dry ball milling, or hot-compressed water treatment (HCWT). Pretreated rice straw and commercial cellulose, Solka Floc (SF), were used as carbon sources for cellulase production by the fungus Acremonium cellulolyticus. Filter paper cellulase, β-xylanase, and β-xylosidase production from ball- and disk-milled samples were higher than those from SF. Enzymatic activity was absent in cultures where HCWT rice straw was used as carbon source. Wet disk-milled rice straw cultures were more suitable for enzymatic hydrolysis of pretreated rice straw than SF cultures. Thus, wet disk milling may be a suitable pretreatment for producing substrates for enzymatic hydrolysis and generating inexpensive carbon sources for cellulase production.     

Oyster mushroom cultivation with rice and wheat straw

Cultivation of the oyster mushroom, Pleurotus sajor-caju, on rice and wheat straw without nutrient supplementation was investigated. The effects of straw size reduction method and particle size, spawn inoculation level, and type of substrate (rice straw versus wheat straw) on mushroom yield, biological efficiency, bioconversion efficiency, and substrate degradation were determined. Two size reduction methods, grinding and chopping, were compared. The ground straw yielded higher mushroom growth rate and yield than the chopped straw. The growth cycles of mushrooms with the ground substrate were five days shorter than with the chopped straw for a similar particle size. However, it was found that when the straw was ground into particles that were too small, the mushroom yield decreased. With the three spawn levels tested (12%, 16% and 18%), the 12% level resulted in significantly lower mushroom yield than the other two levels. Comparing rice straw with wheat straw, rice straw yielded about 10% more mushrooms than wheat straw under the same cultivation conditions. The dry matter loss of the substrate after mushroom growth varied from 30.1% to 44.3%. The straw fiber remaining after fungal utilization was not as degradable as the original straw fiber, indicating that the fungal fermentation did not improve the feed value of the straw.     

Kinetic study of hydrolysis of xylan and agricultural wastes with hot liquid water

We investigated the kinetics of hot liquid water (HLW) hydrolysis over a 60-min period using a self-designed setup. The reaction was performed within the range 160–220 °C, under reaction conditions of 4.0 MPa, a 1:20 solid:liquid ratio (g/mL), at 500 rpm stirring speed. Xylan was chosen as a model compound for hemicelluloses, and two kinds of agricultural wastes–rice straw and palm shell–were used as typical feedstocks representative of herbaceous and woody biomasses, respectively. The hydrolysis reactions for the three kinds of materials followed a first-order sequential kinetic model, and the hydrolysis activation energies were 65.58 kJ/mol for xylan, 68.76 kJ/mol for rice straw, and 95.19 kJ/mol for palm shell. The activation energies of sugar degradation were 147.21 kJ/mol for xylan, 47.08 kJ/mol for rice straw and 79.74 kJ/mol for palm shell. These differences may be due to differences in the composition and construction of the three kinds of materials. In order to reduce the decomposition of sugars, the hydrolysis time of biomasses such as rice straw and palm shell should be strictly controlled.     

Wet disk milling pretreatment without sulfuric acid for enzymatic hydrolysis of rice straw

Rice straw has recently attracted interest in Japan as a potential source of raw material for ethanol production. Wet disk milling, a continuous pretreatment to enhance the enzymatic digestibility of rice straw, was compared with conventional ball milling and hot-compressed water treatment. Pretreated rice straw was evaluated by enzymatic hydrolysis using Acremonium cellulase and characterized by X-ray diffraction and scanning electron microscopy. Glucose and xylose yields by wet disk milling, ball milling, and hot-compressed water treatment were 78.5% and 41.5%, 89.4% and 54.3%, and 70.3% and 88.6%, respectively. Wet disk milling and hot-compressed water treatment increased sugar yields without decreasing their crystallinity. The feature size of the wet disk milled rice straw was similar to that of hot-compressed water-treated rice straw. The energy consumption of wet disk milling was lower than that of other pretreatments. Thus, wet disk milling is an economical, practical pretreatment for the enzymatic hydrolysis of lignocellulosic biomass, especially herbaceous biomass such as rice straw.     

Characteristics of rice straw and sewage sludge as composting materials in Valencia (Spain)

This work supports the idea that composting can be useful for minimizing the rice straw and sewage sludge environmental impact. Several physical, chemical and microbiological properties of these raw materials were analyzed. The characteristics of the rice straw were complementary to those of the sewage sludge for the application of composting. The C/N ratios suitable for a rapid increased in microbial activity were the lowest (17-24). A temperature of 62 degrees C during 48 h removed pathogenic microorganisms from rice straw and sewage sludge mixture. The results obtained in the present work suggested that these materials could be use in the composting process.     

Improving probiotic spore yield using rice straw hydrolysate

Spore-forming Bacillus sp. has been extensively studied for their probiotic properties. In this study, an acid-treated rice straw hydrolysate was used as carbon source to produce the spores of Bacillus coagulans. The results showed that this hydrolysate significantly improved the spore yield compared with other carbon sources such as glucose. Three significant medium components including rice straw hydrolysate, MnSO₄ and yeast extract were screened by Plackett–Burman design. These significant variables were further optimized by response surface methodology (RSM). The optimal values of the medium components were rice straw hydolysate of 27% (v/v), MnSO₄ of 0·78 g l⁻¹ and yeast extract of 1·2 g l⁻¹. The optimized medium and RSM model for spore production were validated in a 5 l bioreactor. Overall, this sporulation medium containing acid-treated rice straw hydrolysate has a potential to be used in the production of B. coagulans spores.     

Natural cellulose fibers from soybean straw

This paper reports the development of natural cellulose technical fibers from soybean straw with properties similar to the natural cellulose fibers in current use. About 220 million tons of soybean straw available in the world every year could complement the byproducts of other major food crops as inexpensive, abundant and annually renewable sources for natural cellulose fibers. Using the agricultural byproducts as sources for fibers could help to address the concerns on the future price and availability of both the natural and synthetic fibers in current use and also help to add value to the food crops. A simple alkaline extraction was used to obtain technical fibers from soybean straw and the composition, structure and properties of the fibers was studied. Technical fibers obtained from soybean straw have high cellulose content (85%) but low% crystallinity (47%). The technical fibers have breaking tenacity (2.7 g/den) and breaking elongation (3.9%) higher than those of fibers obtained from wheat straw and sorghum stalk and leaves but lower than that of cotton. Overall, the structure and properties of the technical fibers obtained from soybean straw indicates that the fibers could be suitable for use in textile, composite and other industrial applications.     

Rice straw, the role of silica and treatments to improve quality

Rice straw is unique relative to other cereal straws in being low in lignin and high in silica. Unlike other cereal straws taller varieties of rice straws tend to be leafy while the leaves are less digested than stems. This may contribute to higher straw value with rice yield. There is genetic variation in straw quality but has not been exploited and tends to be smaller than environmental variation. Effort in plant breeding has been to develop short varieties with higher grain yield. This development has reduced straw quantity but not nutritive value. The relationship between plant genetics and silica metabolism is virtually uninvestigated, although reviews from plant physiology indicate it is a major factor.

Silica and lignin in that order are the primary limiting factors in rice straw quality. Silicon is a nutrient element which has been overlooked largely because of its assumed inertness, but also because of its geochemical abundance that so greatly exceeds its metabolic use by plants and animals. Silicon is involved in several major roles in rice: carbohydrate synthesis, grain yield, phenolic synthesis and plant cell wall protection. These vectors interact with each other to eliminate statistical association of silica and lignin with straw digestibility when varieties are compared. Yield of grain is highly related to silica content of straw, which reflects soil availability. There are no detailed studies on rice straw lignin. Most papers reporting lignin contents in rice straw have used acid-detergent lignin by either the sulfuric acid or permanganate versions. There are undoubtedly soluble phenolics in rice straw that need investigation. The effects of ammonia and urea on silica is to crack the silicified cuticular layer. Silica is not dissolved by these reagents in contrast to the action of sodium hydroxide.

Treatments on rice straw follow those applied to other lignified materials. In order of frequency of reports, urea followed by ammonia with comparatively fewer papers on sodium hydroxide, steam and pressure treatments or exploded by pressure release, and only one or two papers on acid treatments and white rot fungi. There are reports on animal supplementation and a few growth studies with young animals. Field surveys in India and the southeast Asian countries only report the use of urea, although it appears less efficient than ammonia. Farmer acceptance is related to their perceptions on costs, labor, equipment, health, safety, i.e. the exposure to ammonia vapor, economic and other social factors. The various papers reporting treatments have used animal digestion trials; a variety of in sacco, in vitro digestions with rumen organisms or cellulase, some in combination with pepsin digestion or neutral-detergent extraction. Gas production from in vitro rumen fermentation has also been used. Results are expressed mainly on dry matter basis and fewer reports on organic matter. Results are difficult to compare and standardization of procedures is badly needed. However, most treatments with ammonia and urea show some increase in digestibility and intake where measured in in vivo trials. In vitro and in sacco evaluations tend to overestimate improvement in digestibility.     

Influence of Moisture Content,Particle Size,and Binder Ratio on Quality and Economics of Rice Straw Briquettes

Rice straw as solid residues are biomass residue materials that are not optimally used by farmers in Punjab and potentially become environmental pollutant. A large amount of rice straw (17 million tons) is generated and left as much in combine harvested rice fields in Punjab, India. It is very difficult to manage such huge amount of rice straw thus, farmers resort to burning it which leads to greenhouse gas emissions like CO₂ due to open field burning and loss of rich organic matter present in the soil. Further due to imposition of restrictions by the state government, the practice of burning rice straw has now become an offense. So farmers are looking for alternatives which are economically viable. Rice straw can be effectively used as bio energy as it has about the same heating value (15 kJ kg^?1) as that of wood, half that of good quality coal and one third of oil. The operational conditions required to produce high-quality chopped rice straw briquettes have not been determined and this study determined the optimal moisture content, particle size, and binder ratio required to produce rice straw briquettes. The optimized conditions resulted in formation of high-density (1030.38–1159.22 kg m^?3) briquettes with durability ranging from 71.9 to 92.3% with minimum power requirement for briquetting (36.60 kW), maximum calorific value of 15.61 MJ kg^?1, and minimum ash content (16.34%).Total cost of making chopped rice straw briquettes was 0.041 USD per kg and 0.00281 USD per mega joule of energy. Cost of briquetting from chopped rice straw with 10 and 20% cotton stalks was 0.050 and 0.051 USD per kg, respectively, and 0.0033 USD per mega joule of energy. Also, the briquettes prepared from chopped rice straw with and without cotton stalk as a binder were economically viable.     

不同有机废弃物改良新复垦耕地的综合效果评价

由废弃地整理复垦形成的耕地存在土壤有机质和有效养分低、土壤板结、微生物活性弱和土壤耕作性状不良等问题,快速、有效地提高土壤肥力质量是全面提升该类耕地质量和生产性能的重要组成部分.本文通过田间小区试验研究了城郊有机废弃物对新复垦耕地土壤培肥的综合效果,并比较了不同类型城郊有机废弃物在培育耕地质量方面的差异.试验设置了施用等量猪粪、鸡粪、水稻秸秆、蔬菜收获残留物、城市污泥、沼渣、猪粪/水稻秸秆堆肥、生活垃圾堆肥和对照（不施有机肥）9个处理（年用量30 t·hm^-2）,连续进行3年的定点试验.结果表明： 施用任何有机物对改善土壤肥力均有明显的作用.其中,提升土壤碳库管理指数以施用猪粪、鸡粪、猪粪/水稻秸秆堆肥、水稻秸秆和沼渣的效果最为显著;增加土壤水稳定性团聚体和降低土壤容重以施用猪粪/水稻秸秆堆肥和沼渣的效果最佳;施用污泥、猪粪/水稻秸秆堆肥和生活垃圾堆肥可增强土壤保蓄能力;施用猪粪、鸡粪和猪粪/水稻秸秆堆肥对增加土壤有效态养分的效果最为明显;各类有机物均显著提高了土壤微生物数量和酶活性.长期施用污泥、生活垃圾堆肥及畜禽粪存在着土壤重金属污染的风险,但短期施用对土壤环境质量影响不明显.总体上,对土壤肥力的改善效果由大至小依次为：猪粪/水稻秸秆堆肥>鸡粪>猪粪>沼渣>生活垃圾堆肥>水稻秸秆>城市污泥>蔬菜收获残留物;对土壤的相对污染程度由大至小为：城市污泥>生活垃圾堆肥>猪粪>鸡粪>沼渣>猪粪/水稻秸秆堆肥>蔬菜收获残留物>水稻秸秆.     

Evaluation of effectiveness of pretreating rice straw with n-butylamine for improvement of sugar yield

Summary n-Butylamine (n-BA) pretreatment extracted a part of the holocellulose (cellulose and hemicellulose) in rice straw into the liquid phase, as a mixture of oligosaccharides and a small amount of monosaccharides. However, there was loss of sugars resulting mainly from decomposition of monomers by a long exposure to a high n-BA concentration. Approximately 70% of the total sugars in the pretreatment solutions was converted enzymatically into reducing sugars (mainly monomers). On the other hand, more than 90% of holocellulose in the residual rice straw after the optimal pretreatment was solubilized enzymatically in 120 h of reaction time with 10 w/v% substrate and 6 mg protein/ml cellulase. The main action of n-BA on rice straw was delignification, and highly crystalline cellulose was not swollen. Thus the enhancement of the enzymatic solubilization rate of rice straw appeared to be due to the increase of surface area accessible to the enzyme by delignification. It was demonstrated by the relationship of the vapour-liquid equilibrium of the n-BA/water system that the n-BA used was recovered easily. The loss of n-BA, at most, was 30% in the case of the weight ratio of n-BA to rice straw of 0.1.     

Optimization of cellulase-free xylanase production by thermophilic Streptomyces thermovulgaris TISTR1948 through Plackett-Burman and response surface methodological approaches

Cellulase-free xylanase production by thermophilic Streptomyces thermovulgaris TISTR1948 was cultivated in a basal medium with rice straw as sole source of carbon and as an inducible substrate. Variable medium components were selected in accordance with the Plackett-Burman experimental design. The optimization conditions of physical factors (pH and temperature levels) were then combined in further studies through the response surface methodology approach. Only two significant components, rice straw and yeast extract, were chosen for the optimization studies. A second-order quadratic model was constructed by central composite design (CCD). The model revealed that both pH and temperature levels were significant, and were dependent on xylanase production. Under these experimental designs, the xylanase yield increased from 51.11 to 274.49 U/mL (3,400 to 10,000 U/g of rice straw) or about 537% higher than an unoptimized basal medium. The optimum conditions to achieve maximum yield of xylanase were 27.45 g/L of rice straw and 5.42 g/L of yeast extract under relatively neutral conditions of pH 7.11, 50.03 °C, and a incubation period.     

Amelioration of growth reduction of lowland rice caused by a temporary loss of soil-water saturation

Decreases in nutrient availability after loss of soil-water saturation are significant constraints to productivity in lowland rainfed rice soils. The effectiveness of soil amendments like lime and straw in ameliorating these constraints are poorly understood. This pot experiment was conducted in Cambodia to investigate changes in soil chemical properties and nutrient uptake by rice after applying lime or straw to continuously flooded or intermittently flooded soil. In continuously flooded soils, exchangeable Al decreased to below 0.2 cmolc/kg. Liming (pH 6.5–6.8) the continuously flooded soil decreased the levels of acetate extractable Fe and P, plant P uptake and shoot dry matter, but had no effect on either Bray-1 or Olsen extractable P values. By contrast, the addition of straw (3.5 g dry straw/kg soil) increased Bray-1, Olsen, and acetate extractable P, plant P uptake, shoot P, and shoot dry matter. The non-amended soils became strongly acidic after loss of soil water saturation: extractable Al increased to 1.0 cmol_c/kg, a potentially harmful level for rice. By contrast, extractable P decreased markedly under loss of soil water saturation as did plant P uptake, shoot P, and shoot dry matter. With loss of soil water saturation, liming substantially depressed the levels of Al but it did not increase plant P uptake, shoot P, and shoot dry matter. Straw addition not only decreased extractable Al levels to well below 0.6 cmol_c/kg under loss of soil water saturation, but it also increased extractability of soil P, plant P uptake, shoot P, and shoot dry matter. Thus, in rainfed environments, the incorporation of straw may be more effective than liming to pH 6.8 for minimising the negative effects of temporary loss of soil-water saturation on P availability, P uptake, and growth of rice.     

Comparison of the rates of enzymatic hydrolysis of pretreated rice straw and bagasse with celluloses

The rates of enzymatic hydrolysis of pretreated rice straw and bagasse have been studied and compared with the hydrolysis rates of microcrystalline cellulose powder (MCCP) and Solka Floc. The effects of particle size reduction and enzyme loading on the rates of hydrolysis of rice straw and bagasse were also studied. It was found that the rates of hydrolysis of pretreated rice straw and bagasse are much higher than that of MCCP and Solka Floc. For both rice straw and bagasse, particle size reduction had very little effect in enhancing the rate of hydrolysis. Lignin present at <10% did not seem to hinder the accessibility of the enzyme to the cellulose surface. An enzyme loading > 40 Ug^?1 had no effect on the hydrolysis rate of rice straw or bagasse.     

Physio-chemical characterization of indigenous agricultural waste materials for the development of potting media

Organic residues are an important factor that directly affects fruiting tree seedlings' health at earlier stages. It provides a suitable environment for seedling growth by providing better nutrient ions, water, and aeration. However, low organic contents and high shrinkage of most organic materials mostly deteriorate ideal potting media characteristics. Low aeration, high water, and nutrients leaching decrease seedling growth and cause a significant loss of valuable resources. That is why the current study was conducted to screen out the best indigenous materials based on particle size to produce good characteristics bearing potting media. For that, eight different ingredients, i.e., “sugarcane”, “coconut coir”, “wheat straw”, “rice straw”, “corn cob”, “leaf litter”, “farmyard manure”, and “sunflower heads” were collected. Initially, all the materials were air-dried and processes as per requirement. After grinding, three particles size (fine = < 2 mm, medium = 3 mm and coarse = 5 mm) were separated by sieving. Results showed that decreasing particle size in “rice straw”, “corn cob”, “farmyard manure,” and “sunflower head” decreased leachate pH. Higher EC in leachates was negatively correlated with particle size in all potting media ingredients. Except for farmyard manure, fine particle size increases the water-holding ability of potting media ingredients. However, air-filled porosity was associated with a decrease in particle size of potting media in gradients. In conclusion, farmyard manure, “sunflower heads”, “leaf litter” and “sugarcane” should be incorporated while making a combination for potting media. More investigations are suggested by mixing different particle size ingredients to prepare potting media.     

Seasonal variation in methane flux from rice paddies associated with methane concentration in soil water,rice biomass and temperature,and its modelling

To attempt to develop physicochemical and physiological modelling for methane transport from the rhizosphere to the atmosphere through rice plants, methane flux, methane concentration in the soil water, and the biomass of rice were measured in lysimeter rice paddies (2.5 × 4 m, depth 2.0 m) once per week throughout the entire growing season in 1992 at Tsukuba, Japan. The addition of exogenous organic matter (rice straw) or soil amendments with the presence or absence of vegetation were also examined for their influence on methane emissions. The total methane emission over the growing season varied from 3.2 g CH₄ m^-2 y^-1 without the addition of rice straw to 49.7 g CH₄ m^-2 y^-1 with rice straw and microbiological amendment. In the unvegetated plot with the addition of rice straw, there was much ebullition of gas bubbles, particularly in the summer. The annual methane emission due to the ebullition of gas bubbles,from the unvegetated plot with the addition of rice straw was estimated to be almost the same as that from the vegetated site with the addition of rice straw. In the early growth stage, the methane flux can be analyzed by the diffusion model (Flux=Methane concentration × Conductance of rice body) using parameters for methane concentration in the soil water as a difference in concentration between the atmosphere and the rhizosphere, and for the biomass of rice as a conductance of rice body. On the other hand, although the diffusion model was inapplicable to a large extent from the middle to late growth stage, methane flux could be estimated by air temperature and concentration in the soil water. Thus, methane transport from the rhizosphere to the atmosphere through rice plants consisted of two phases: one was an explainable small part by diffusion in rice body; the other was a large part strongly, governed by air temperature. The existence of gas bubbles in the soil may be related to the transition between the two phases     

Production of levulinic acid from steam exploded rice straw via solid superacid, S2O8(2-)/ZrO2-SiO2-Sm2O3

In this study, solid superacid was employed to catalyze the decomposition of steam exploded rice straw (SERS) for the production of levulinic acid, a versatile platform chemical. The results revealed that solid superacid, S(2)O(8)(2-)/ZrO(2)-SiO(2)-Sm(2)O(3), could be used as a substitute for homogenous acid to catalyze the production of LA from SERS and LA yield increased with the addition of solid superacid. It was also found that steam explosion combined with superfine grinding of rice straw could effectively increase LA yield for reducing particle size of rice straw and enhancing the accessibility of cellulose. Under optimal conditions of 200°C, 10 min, 13.3% of solid superacid to pretreated rice straw, and 1:15 of solid-liquid ratio, LA yield of the superfine grinding SERS was 70% of the theoretical yield, which was equivalent with the homogeneous acid-catalyzed production of LA.