Rice Straw Burning Research Articles

Size distribution of atmospheric particulates and particulate-bound polycyclic aromatic hydrocarbons and characteristics of PAHs during haze period in Lampang Province, Northern Thailand

Size distributions of atmospheric particulates and particulate-bound polycyclic aromatic hydrocarbons (p-PAHs) in different inhalable fractions (9.0–5.8, 5.8–4.7, 4.7–3.3, 3.3–2.1, 2.1–1.1, 1.1–0.7, 0.7–0.4, and 2.1 μm). Experimental results show that the average concentration of particulate matter less than 10 μm during the haze period was 3.5 times higher than that during the non-burning period. The atmospheric aerosols during the haze period contained the largest fraction of particles in nuclei mode while the emission during rice straw burning introduced the largest fraction of particles in accumulation mode. The size distributions of total PAHs during the haze period and rice straw burning were shifted towards the smaller particles relative to their particle size distribution. The size distributions of total PAHs were bimodal during the haze period and unimodal during rice straw burning. The fractions of five- and six-ring PAHs bound on the particles were predominantly detected during the haze period whilst those of three- and four-ring PAH compounds were mainly found in smoke emitted from rice straw burning. The ratio of carcinogenic and noncarcinogenic PAH compounds during the haze period was composed of more carcinogenic PAHs than that during rice straw burning.

STUDY OF THE COMBUSTION MECHANISM OF OIL SHALE SEMI-COKE WITH RICE STRAW BASED ON GAUSSIAN MULTI-PEAK FITTING AND PEAK-TO-PEAK METHODS

In this research, a series of experiments on combustion of Huadian oil shale semi-coke and rice straw as well as their mixture were conducted at different heating rates (10, 20, 50 and 80 °C/min) under atmospheric pressure, using a Perkin Elmer thermogravimetric analyzer. Combustion characteristics were investigated at different proportions of materials (L1, L2, L3, L4 and L5) and at different heating rates. The results revealed that the point of ignition and burnout shifted to lower temperature with increasing rice straw proportion in the mixture. In the combustion process, the inter- action between the mixture components mainly occurred in the temperature range of 400 to 600 °C. It was found that in this stage the reaction of bimodal components of semi-coke and rice straw took place. Besides, using the Gaussian multi-peak fitting method it was established that the derivative mass loss (DTG) curves displayed an overlapping peak, which consisted of three sub-peaks corresponding to the components of the blend. Moreover, based on the three sub-peaks, kinetic parameters and feature values were found employing the peak-to-peak method. The results showed that the reaction order of various sub-peaks for samples L1, L2, L3 and L4 was 1.17 to 2.27. The activation energies of sub-peaks were determined to be 21.89- 99.79 KJ/mol throughout the analysis of the combustion mechanism. It was concluded that the model can be applied to determining combustion charac- teristics.

Emissions Inventory for Rice Straw Open Burning in Taiwan Based on Burned Area Classification and Mapping Using Formosat-2 Satellite Imagery

ABSTRACTRice straw open-field burning is practiced in many countries and has been proven to be a significant source of emissions during the harvest season. Current approaches to obtain the fraction of rice straw subject to open burning vary significantly, and can lead to incorrectly estimating air pollutant emissions. This study proposes a remote sensing approach by classifying high-resolution imagery taken by Formosat-2 (FS-2) to map burned areas of rice paddy fields during harvest season to provide visualized and accurate estimations. We requested FS-2 image acquisition over the Chianan Plain, which is the greatest rice-producing area of Taiwan, during 3 weeks following the harvesting of the fall crops in 2009. Simultaneously, a mobile team on the ground examined the state of the rice paddies when FS-2 was scheduled to take the images. Based on these data, a procedure that integrated a ground truth-based classification scheme, land use data, spectral signatures, and supervised decision rules was applied to identify burned sites. The results were verified using the field data, with an overall accuracy of 87% for distinguishing among the 6 cover types of rice paddies, showing that 27.3% of the paddies within the study area were openly burned. Based on the mapping results, a comprehensive inventory of the air pollutant emissions from straw open burning in Taiwan is presented. To facilitate the management of emission sources and to improve local air quality, we encourage the use of FS-2 imaging to monitor the open burning of rice straw.

Anhydrosugar characteristics in biomass smoke aerosol—case study of environmental influence on particle-size of rice straw burning aerosol

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.

Biomass-burning에서 배출되는 미세입자 (PM2.5)의 배출원 구성물질 성분비 개발에 관한 연구

This study was performed to develop the source profiles for fine particles () emitted from the biomass burning. The multi-method research strategy included a usage of combustion devices such as field burning, fireplace, and residential wood burning to burn rice straw, fallen leaves, pine tree, and oak tree. The data were collected from multiple sources and measured water-soluble ions, elements, elemental carbon (EC), and organic carbon (OC). From this study, it turned out that OC (34~67%) and EC (1.2~39%) are the major components emitted from biomass burning. In the case of burning rice straw at field burning, OC (66.6%) was the most abundant species, followed by EC (4.3%), (3.6%), Cl (2.1%), and (1.9%). Burning rice straw, fallen leaves, pine tree, and oak tree at fireplace, the amount of OC was 58.5%, 52.7%, 52.5%, and 61.2%, and that of EC was 1.2%, 18.4%, 36.5%, and 2.7%, respectively. The ratio of OC for the burning of pine tree and oak tree from the residential wood burning device was 56.9% and 34.3%, and that of EC was 25% and 38.6%, respectively. Applying the measured data with respect to the proportion of components emitted from biomass burning to reference model, it turned out that self-diagnosed result was appropriate level, and the result based on the model is in highly corresponding to actual timing of biomass burning.

Emission inventory of carbonaceous pollutants from biomass burning in the Pearl River Delta Region, China

Emissions from burning major agricultural residue were measured through laboratory simulations using a self-designed dilution chamber system. Emission factors of CO2, CO, non-methane hydrocarbons (NMHCs), oxygenated volatile organic compounds (OVOCs), PM10, PM2.5, OC and EC in PM2.5 were measured for burning rice straw in flaming and smoldering combustion, and for burning of sugarcane leaves. NMHCs emitted from crop straw open burning were dominated by C2 hydrocarbons (ethene, ethane, ethyne), contributing (53.4 ± 4.6)% in volume in rice straw burning emissions and 41.8% in sugarcane burning emissions, respectively. Acetone and aldehyde were major OVOCs species in open straw burning emissions. A survey was conducted to determine the fraction of field crop biomass burned during harvesting season and the amounts of household firewood and crop residue consumption in 2008. Information obtained from the survey, together with measured EFs for field burning of rice straw and sugarcane, and EFs from literatures for field burning of other agricultural residues, biofuel combustion and forest fires, were used in developing the source inventories of carbonaceous pollutants in the PRD region. The annual emissions of CO, VOCs (including NMHCs and OVOCs), NOx, PM2.5, OC and EC from burning biomass were estimated to be 186.38, 15.94, 4.93, 15.56, 7.10, 2.25 kt in the year 2008, respectively. These estimates are lower than previously published estimates by 23–63%. Open burning patterns (flaming and smoldering) and rural biofuel use contribute to the differences. Field burning of straw contributed mainly to VOCs, PM2.5 and OC emissions while the residential sector was the dominant source of EC, CO and NOx. The contributions of biomass burning to entire PRD emissions are estimated as 3.37–6.53%, respectively, for PM, and 1.82–3.17%, respectively, for VOCs, and 0.52–2.77%, respectively, for NOx.

SORPTION AND DESORPTION BEHAVIORS OF METHYLENE BLUE IN SOILS AMENDED WITH RICE-STRAW-DERIVED ASH AND BIOCHAR

The ash (Ash) and biochar (BC) derived from the partial combustion of rice-straw are ubiquitous in soils and sediments and can potentially affect the environmental fate of organic contaminants. In this study, the effects of Ash and BC on the sorption and desorption behaviors of methylene blue (MB) were investigated. Ash was obtained from the direct burning of the rice-straw, and BC was separated from Ash by HCl treatment. SEM, BET, FT-IR, and pore size distribution analyses were used to characterize the Ash and BC prepared. Sorption capacities of MB on Ash-amended soil (AS) and BC-amended soil (BS) increased significantly with increasing contents of Ash and BC in soils. Sorption isotherms of soil amended with various amounts of Ash or BC fitted better to the Langmuir equation. The significant increase of apparent desorption hysteresis could be observed with increasing content of Ash or BC in the soils, especially in the case of BC, presumably due to the presence of micropores, hydroxyl groups and relatively higher specific surface area. It is believed that the presence of small amounts of BC produced from the rice-straw-derived ash in soil can have a marked effect on the transfer behavior of dye contaminations.

Influence of the Atmosphere on the Transformation of Alkali and Alkaline Earth Metallic Species during Rice Straw Thermal Conversion

The influence of the atmosphere on the transformation of alkali and alkaline earth metallic (AAEM) species during rice straw thermal conversion was investigated by a fixed-bed reactor at 1073, 1173, and 1273 K. Two types of atmospheres were considered: 100% (v/v) N2 to simulate pyrolysis and 1% (v/v) O2 in N2 balance to simulate combustion. The release of the AAEM species during pyrolysis and combustion of the rice straw was quantified by a mass balance based on the weight measurements and inductively coupled plasma (ICP) analysis of the rice straw and the solid residue. Solid residues and released and condensed particles obtained in experiments were processed by water leaching and 1% HNO3 washing and analyzed by ion chromatography (IC) to determine the possible chemical form of the AAEM species contained in them. The experimental results showed that the oxidizing atmosphere facilitated the release of K at 1073, 1173, and 1273 K by enhancing the decomposition of K2CO3 and char K in the char during the char combustion stage of the rice straw combustion experiment. However, the oxidizing atmosphere suppressed the release of Na, Ca, and Mg at 1073, 1173, and 1273 K. For Na, the release suppression was caused by its promoted interaction with silicate in the oxidizing atmosphere. For Ca and Mg, such suppression was supposed to be caused by the suppressing effect of the oxidizing atmosphere on the release of Ca and Mg from char Ca and char Mg in the char of the rice straw.

Estimating air pollutant emission factors from open burning of rice straw by the residual mass method

Air pollutant emission factors produced by open burning of rice straw were estimated using the residual mass method which incorporated ambient air-quality and meteorological data of measured stations. The residual mass method regarded the residual mass of air pollutants as emissions caused by the open burning of rice straw. Lasting from November 27–28, 2002, the selected episode resulted in the most serious air pollution in the recent decade in terms of open burning of rice straw, significantly degrading air quality in central-south Taiwan. Emission factors from open burning of rice straw, as modeled by the residual mass method, were 30.3±1.45, 5.14±0.13, 3.44±0.09, 6.28±0.34, and 0.058±0.003gkg−1 for CO, NMHCs, NOx, PM10 and SO2, respectively. The maximum daily emissions of CO and PM10 were 1000kgkm−2 and located at central-south Taiwan. Additionally, emissions of CO and PM10 in EPS were 7.67 and 9.33 times higher than MON during the rice straw burning episode. The spatial emission of EPS and MON were also presented with the residual mass method. Comparing our results with those of other studies revealed that calculated emission factors in this study were in an acceptable range.

Characterization of ambient air quality during a rice straw burning episode

Spatiotemporal characteristics and impact of ambient air-quality attributed to open burning of rice straw were analyzed and estimated with measured data. Two multivariate analytic methods, factor analysis and cluster analysis, were adopted to analyze the temporal and spatial impact on ambient air-quality during the rice straw burning episode. Temporal features of three scenarios were cited to compare the concentrations for ambient air-quality between the rice straw burning episode and non-episodes over two typical stations by factor analysis. Factor analysis demonstrated that the first rotational component, identified as being highly correlated to the open burning of rice straw, accounts for about 40% of the concentration variance for ambient air-quality. In typical air-quality stations, the average hourly incremental concentrations between the episode and non-episodes were greater than 300 μg m(-3) for PM(10), 1.0 ppm for CO and 35 ppb for NO(2) during the impact of rice straw burning. Factor analysis presented that the first rotated component was highly correlated with several primary pollutants (NO(2), NMHC, PM(10) and CO) during the rice straw burning episode, while every component was only highly correlated with a unique air pollutant during non-episodes. The delineation isopleths indicated that factor analysis could serve as a better method than cluster analysis and provides cross-county cooperation for local governments located in the same separated district during the rice straw burning season. The results of factor analysis revealed that CO is the best index to demonstrate the impact of rice straw burning than the other six air pollutants measured during the episode. Backward trajectory analysis supplied a cause-effect relationship between measured stations and specific rice planted regions during the rice straw burning episode.

Exploiting Potentials from Interdisciplinary Perspectives with Reference to Global Atmosphere and Biomass Burning Management

Biomass burning emitted aerosols are subject of concern in different disciplinary researches from different perspectives (climate change science from shift of balance in radiative forcing having severe repercussions on global ecosystem, while air pollution science from public health concern). By exploring particle number emission factors (PNEF), particle size distributions, and volatility of emitted ultrafine particles from burning rice straw, potential annual release of aerosols from rice straw combustion to the global atmosphere is estimated, and the issue of their management from such interdisciplinary perspectives is discussed. Between an estimated as low as 15% and as high as 75% of rice straw being burnt globally, the global annual estimate of emitted aerosols mounted from an order of 1021 particles/yr to the order of 1022 particles/yr. From looking at different estimates made therein, we advocate Dp ≤ 0.25 μm (PN0.25 equivalent) for adopting emission control standards. In volatility analysis flaming combustion and open burning indicated internal mixing of black carbon and organic carbon in emitted ultrafine particles, while smoldering combustion emitted ultrafine particles having little black carbon component. Up to 65% contrast in remaining volume in volatility analysis between the flaming and smoldering combustions, and positioning of open burning in between them, give us the idea of potential management of such biomass burning with controllable distinct choices. Therefore, the concept of exploiting potential from interdisciplinary dimensions is coined to enable more efficient management with least amounts of additional resources utilized, by resolving complexities through mutual cooperation of concerned disciplinary researches. It also shows a new avenue in our affairs in managing global atmosphere for the global ecosystem and public health.

Volatility and mixing states of ultrafine particles from biomass burning

Fine and ultrafine carbonaceous aerosols produced from burning biomasses hold enormous importance in terms of assessing radiation balance and public health hazards. As such, volatility and mixing states of size-selected ultrafine particles (UFP) emitted from rice straw, oak, and pine burning were investigated by using volatility tandem differential mobility analyzer (VTDMA) technique in this study. Rice straw combustion produced unimodal size distributions of emitted aerosols, while bimodal size distributions from combustions of oak (hardwood) and pine (softwood) were obtained. A nearness of flue gas temperatures and a lower CO ratio of flaming combustion (FC) to smoldering combustion (SC) were characteristic differences found between softwood and hardwood. SC emitted larger mode particles in higher numbers than smaller mode particles, while the converse was true for FC. Rice straw open burning UFPs exhibited a volatilization behavior similar to that between FC and SC. In addition, internal mixing states were observed for size-selected UFPs in all biomasses for all combustion conditions, while external mixing states were only observed for rice straw combustion. Results for FC and open burning suggested there was an internal mixing of volatile organic carbon (OC) and non-volatile core (e.g., black carbon (BC)), while the SC in rice straw produced UFPs devoid of non-volatile core. Also, it was found that volatility of constituting OC in FC and SC particles was different.

Polychlorinated dibenzo-p-dioxins, dibenzofurans, and dioxin-like polychlorinated biphenyls in rice straw smoke and their origins in Japan

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (DL-PCBs) contained in the smoke generated from rice straw burning in post-harvest paddy fields in Japan were analyzed to determine their congener profiles. Both the apportionment of toxic equivalent (TEQ) by using indicative congeners and the comparison of the homolog profiles showed that the PCDDs/PCDFs/DL-PCBs present in the rice-straw smoke were greatly influenced by those present as impurities in pentachlorophenol (PCP) and chlornitrofen (CNP, 4-nitrophenyl-2,4,6-trichlorophenyl ether) formulations that had been widely used as herbicides in paddy fields in Japan. Further, in order to investigate the effects of paddy-field soil on the PCDDs/PCDFs/DL-PCBs present in rice-straw smoke, PCDD/PCDF/DL-PCB homolog profiles of rice straw, rice-straw smoke and paddy-field soil were compared. Rice-straw smoke was generated by burning rice straw on a stainless-steel tray in a laboratory. The results suggested that the herbicides-originated PCDDs/PCDFs/DL-PCBs and the atmospheric PCDDs/PCDFs/DL-PCBs contributed predominantly to the presence of PCDDs/PCDFs/DL-PCBs in the rice-straw smoke while the contribution of PCDDs/PCDFs/DL-PCBs formed during rice straw burning was relatively minimal. The major sources of the PCDDs/PCDFs/DL-PCBs found in the rice-straw smoke were attributed primarily to the paddy-field soil adhered to the rice straw surface and secondarily to the air taken by the rice straw. The principal component analysis supported these conclusions. It is concluded that rice straw burning at paddy fields acts as a driving force in the transfer of PCDDs/PCDFs/DL-PCBs from paddy-field soil to the atmosphere.

Experimental research on agglomeration in straw-fired fluidized beds

Agglomeration is a major problem in straw combustion in a fluidized bed. This paper presents the results of rice straw combustion experiments carried out under different operating conditions in a bubble-fluidized bed (BFB). The influences of bed material size and type, feeding mode, temperature, and fluidization number on agglomeration were discussed, and the mode of alkali accumulation in the bed was analyzed. The results indicated that low bed temperature, short fuel in-bed residence time, high fluidization number, and small bed material particles are conducive to agglomeration prevention. Successful extended combustion in a small BFB and in a bench-scale circulating fluidized bed was carried out without agglomeration under selected parameters. This work suggests the possibility for combusting high-alkali straw using fluidization technology.

Growth, yield and water productivity of zero till wheat as affected by rice straw mulch and irrigation schedule

Intensive cultivation of rice and wheat in north-west India has resulted in air pollution from rice straw burning, soil degradation and declining groundwater resources. The retention of rice residues as a surface mulch could be beneficial for moisture conservation and yield, and for hence water productivity, in addition to reducing air pollution and loss of soil organic matter. Two field experiments were conducted in Punjab, India, to study the effects of rice straw mulch and irrigation scheduling on wheat growth, yield, water use and water productivity during 2006–2008. Mulching increased soil water content and this led to significant improvement in crop growth and yield determining attributes where water was limiting, but this only resulted in significant grain yield increase in two instances. There was no effect of irrigation treatment in the first year because of well-distributed rains. In the second year, yield decreased with decrease and delay in the number of irrigations between crown root initiation and grain filling. With soil matric potential (SMP)-based irrigation scheduling, the irrigation amount was reduced by 75 mm each year with mulch in comparison with no mulch, while maintaining grain yield. Total crop water use (ET) was not significantly affected by mulch in either year, but was significantly affected by irrigation treatment in the second year. Mulch had a positive or neutral effect on grain water productivity with respect to ET (WP ET) and irrigation (WP I ). Maximum WP I occurred in the treatment which received the least irrigation, but this was also the lowest yielding treatment. The current irrigation scheduling guidelines based on cumulative pan evaporation (CPE) resulted in sub-optimal irrigation (loss of yield) in one of the two years, and higher irrigation input and lower WP I of the mulched treatment in comparison with SMP-based irrigation scheduling. The results from this and other studies suggest that farmers in Punjab greatly over-irrigate wheat. Further field and modelling studies are needed to extrapolate the findings to a wider range of seasonal and site conditions, and to develop simple tools and guidelines to assist farmers to better schedule irrigation to wheat.

Removal of 2-chlorophenol from water using rice-straw derived ash

Removal of 2-chlorophenol from water using rice-straw derived ash (RSDA) was evaluated in this study to compare with commercial activated carbon. RSDA was obtained by burning rice-straw at 400°C and 700°C for 1 h. This ash can provide a better adsorbent for 2-chlorophenol. The adsorption capacities of RSDA at 400°C and 700°C are 37 and 52 mg g−1 at pH 4, respectively, and decrease to 9.0 and 40 mg g−1 at pH 10. Adsorption of either neutral or anionic 2-cholorphenol by the RSDA are shown as L-shaped nonlinear isotherms, suggesting surface adsorption rather than partitioning is occurring. At higher-burning temperatures, the surface area, porosity, point of zero charge and aromaticity of the resultant RSDA increase, but the oxygen content and surface acidity decrease. The combined effects result in a higher 2-chlorophenol adsorption of RSDA at 700°C, which shows a slight pH effect on the adsorption of 2-chlorophenol, due to the lower content of oxygen-containing functional groups. Oxygen-containing functional groups contribute to surface acidity and H-bonding sites for adsorbed water, which compromises the interaction between 2-chlorophenol and the adsorbents. Thus, it suggests that rice-straw derived carbon (RSDC) can be used as an effective low-cost substitute material for activated carbon for removal of chlorophenols from wastewater.

Tracking sources of severe haze episodes and their physicochemical and hygroscopic properties under Asian continental outflow: Long-range transport pollution, postharvest biomass burning, and Asian dust

[1] Aerosol physicochemical and hygroscopic properties were measured from 12 October to 21 November 2005 at a downwind area of the Asian continental outflow (Gwangju, Korea) to characterize severe haze episodes. Using optically measured elemental carbon (EC) at 660 nm (Opt.EC) and 880 nm (BC) wavelengths and Mie theory, it was estimated that the higher BC/Opt.EC ratio during the cloudy day of the long-range transport (LTP) period was mainly due to EC particle growth from in-cloud processing with secondary aerosols such as sulfate and organic aerosols. Single scattering albedo (SSA) of biomass burning (BB) aerosol increased sharply from 0.89 to 0.94 under a relative humidity >70%, suggesting that organic aerosols emitted from rice straw burning contained high amounts of hydrophilic compounds. The contribution of aerosol water content to the total light extinction coefficient (bext) was determined as 51.4% and 68.4% during the BB and BB + LTP periods, respectively, indicating that the haze episodes were highly enhanced by an increase in aerosol water content. The Asian dust event was characterized by the highest SSA (0.92 ± 0.02), the lowest mass scattering efficiency of fine particles (2.5 ± 1.0 m2 g−1), and the lowest hygroscopic nature (humidity-dependent light scattering enhancement factor, f(80%), which is defined by the ratio of light scattering coefficient at 80% relative humidity to that at dry condition, = ∼1.37). Based on the Angstrom exponent (α) values observed at the source region of the Asian continent and the downwind area of South Korea during the BB + LTP period, it was found that the α value of urban aerosols decreased ∼11% for 1–2 days of the transport, probably due to the increase in particle size through water uptake. Increasing rates of surface PM10 mass concentrations at western coastal areas of the South Korean peninsula were in the range 2.4–14.4 μgm−3 h−1 at the beginning of the BB + LTP period (24 October 2005, 0700–2300 LT). Based on in situ and remote measurement techniques, Asian aerosol outflow over the South Korean peninsula is of the order of 388–3789 tons h−1 at the beginning of the LTP event.

Energy from Combustion of Rice Straw: Status and Challenges to China

As the biggest agricultural country, China has an abundant rice straw energy resource. The characteristics of typical china rice straws are presented as high moisture contents, high volatile contents, high ash contents and low bulk density. At present, rice straw is mainly used as fuel, feedstuff, fertilizer and industrial raw material. With improved living conditions in rural areas, farmers tend to rely more on commercial fuel, which leads to even more open field burning of rice straw, and brings air pollutions and potential energy waste as well. The Chinese government is studying relevant policies on acceleration of comprehensive utilization of rice straw with the goal of utilization rate exceeding 80% in 2015. In this paper, focus is on the combustion of rice straw to extract energy, and related challenges face to china is put forward in this paper also.

Fluidised bed combustion and gasification of rice husk and rice straw – a state of art review

Rice is cultivated in all the main regions of world. The worldwide annual rice production is 666 million tons for the year 2008. The combustion and gasification of rice husk/rice straw in fluidised bed reactors seems to be an attractive possibility of future for power generation, the solution of waste disposal problems and the reduction of greenhouse gases. In this paper, overview of fluidised bed reactors based on rice husk/rice straw and some data collected/measured from rice husk-rice straw power plant is presented. Combustion efficiency from 60% to 98%, combustion at bed temperature from to 600°C–850°C, carbon conversion efficiency up to 98% and cold gas efficiency up to 67% is reported. Gas heating value up to 6.6 MJ/m 3 and 5.5 MJ/kg is reported. Combustion intensity up to 530 kg/h/m 2 is reported. SOx and NOx emitted from fluidised bed combustors based on rice husk and rice straw are generally very less under normal operating conditions.

Effects of rice straw ash amendment on Cu solubility and distribution in flooded rice paddy soils

Rice straw burning is a common post-harvest practice on rice paddy land, and it leads to the accumulation of rice straw ash (RSA) in paddy soil. To understand the role of RSA in determining the mobility and bioavailability of metal contaminants, this study investigated the effects of RSA amendment on the solubility and distribution of Cu in contaminated rice paddy soils with flooding incubation. The addition of RSA to the soils suppressed the release of Cu into the soil solutions, which was primarily attributed to the metal-binding capacity of the RSA. Additionally, after the soils were flooded, the increase in soil pH and decrease in redox potential resulted in the transformation of Cu into less soluble forms. The RSA amendment appeared to enhance the changes in pH and redox potential of the flooded soils and, consequently, the immobilization of Cu in the soils. The results suggest that the RSA can retard the bioavailability and movement of the metal in contaminated soils and, thus, lower the potential environmental risk of Cu toxicity.