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Abstract—Open burning of rice straw causes release of airpollutants, which contributes to enhance climate change relatedissues. Moreover, the burning practice was a reason of losingcarbon content from crop land to the atmosphere. This studyfocuses on estimation of carbon content loss to the atmospherethrough open burning of rice straw and suggests alternative ricestraw management practices to reduce field openburning inThailand. Field experiments were conducted to collect samplesof rice straw to quantify residue to product ratio (RPR) andanalyze their carbon content by elemental analysis. Ash sampleswere also collected to analyze their carbon content. Carbonlosses to the atmosphere through field burning were thenestimated. To better understand traditional practices of openburning in Thailand, statistics related to seasonal riceproduction/harvesting were also investigated. Finally, economicand environmental benefits associated to alternative rice strawmanagement options were considered and discussed againsttraditional open burning practices.Index Terms—Rice straw, residue to product ratio, field openburning, carbon released.I. INTRODUCTIONOpen burning of biomass is a serious problem in Thailand,especially in dry season. In April to May, thick smoke hazecould be detected by satellite and the monitoring maximumconcentration of 24-hr average PM10 in north regionexceeded the National Ambient Standard (120 µg/m3). Thegovernment has tried to control this problem by set upNational policies and plans to control fire and haze i.e.National Master Plan for Open Burning Control (2005),National Action Plan on Fire and Haze Control (2012-2017),National Fire and Haze Control Plan of Action (2013), and soon. Major sources of smoke and haze problem were forestfire, agricultural fire, and open burning of waste [1]. Thisstudy focuses on a source of agricultural fire, which is openburning of rice straw in paddy fields.Following harvesting of rice, there are various practices toclear the land for next cultivation. The common practice isburning, which is the most convenient, cheapest, and fastestway to eliminate rice straw, especially in irrigated paddy field.Burning of rice straw in the field releases pollutants to theatmosphere and contributes to enhance global problems suchas climate change. During burning, carbon is released into theair in various forms. Major fractions of carbon released fromManuscript received December 5, 2012; revised February 6, 2013. Thiswork was supported in part by the Joint Graduate School of Energy andEnvironment, and Petch Phrachomklao King Mongkut’s UniversityofTechnology Thonburi.The authors are with the Joint Graduate School of Energy andEnvironment, Bangkok, Thailand (e-mail: kkanittha@ Yahoo,[email protected]).crop burning consist of CO2 (1,515±117 g/kgdm), CO (92±84g/kgdm), TC (4 g/kgdm), and CH4 (2.7 g/kgdm) [2]. These airpollutants contribute to enhance climate change [3], [4].Although biogenic carbon is emitted to the atmosphere as aresult of open burning, the CO2 fraction is reabsorbed viaphotosynthesis in the next cultivation in the form carbonbiomass. However this is not the case for other forms ofcarbon such as CO, TC or CH4. Therefore in this study theamount of carbon loss to the atmosphere is also accountedfor.In this study, benefits from alternative rice strawmanagement practices are also analyzed to serve as aguideline for good management practices after riceharvesting.II. MATERIALS AND METHODSA. Field Experiments in the Paddy FieldsField experiments were conducted in paddy field inirrigated and non-irrigated areas. At the study sites, rice wascultivated by broadcast and harvested by machine. Inirrigated areas, rice can be cultivated more than once a year.The cultivation is done during the rainy season, called “majorrice” and off-rainy season, called “second rice.” Experimentswere carried out for both major rice and second rice. Innon-irrigated areas, water from rain is relied upon so that ricecan only be cultivated once a year during the rainy season,called “major rice.” However, in areas where there aresufficient resources in natural water, rice can also be plantedduring the dry season, called “second rice.”Samples of rice straw were collected to determine theresidue to product ratio (RPR) which is obtained by dividingthe dry weight of rice straw with that of paddy rice. Thisstudy focuses on rice straw burning, the top part of residueswhich mostly burn after harvesting. To quantify dry weight,the samples were dried at 70°C (to remain carbon component)for at least 24 hr until the weight was stable. After burning,samples of ash were collected to consider dry weight andcarbon content.Overall, the amount of rice straw in the country wasquantified by multiplying the RPR obtained from fieldexperiments with rice production statistics in Thailand [5].The base year of this study is 2010 because cultivation of ricein this year followed normal practice; there was no severeflood or drought in the selected year.B. Analysis of Carbon ContentRice straw and ash samples were analyzed for their carboncontent by ultimate analysis. The experiments wereconducted by thermal method with Elemental AnalyzerAlternative Rice Straw Management Practices to ReduceField Open Burning in ThailandK. Kanokkanjana and S. GarivaitInternationalJournal of Environmental Science and Development, Vol. 4, No. 2, April 2013119DOI: 10.7763/IJESD.2013.V4.318(Thermo Fisher Scientific, Model Flash EA 1112 NC Series,UK). Helium was used as carrier gas. The chemical standardwas BBOT, containing 6.51%N, 72.53%C, and 6.09%H.Approximate 4 mg of samples were analyzed in each batchwith three replicate. Operated temperature of the EA machinewas at 950 °C.C. Carbon Released from Open Burning of Rice StrawResults of ultimate analysis were applied in the followingequation to determine the amount of carbon released to theatmosphere.ashburnedreleased CCC −= (1)Quantity of carbon released from open burning of ricestraw (Creleased) was obtained by subtracting amount of carbonthat remain in ash after burning (Cash) from carbon contentcontained in burned rice straw (Cburned). To obtain Cburned andCash, percentage of carbon content in rice straw and ash fromultimate analysis results were multiplied with dry weight ofrice straw and ash.In order to estimate total amount of Creleased from openburning of rice straw based on season of burning in Thailand,data on quantity of rice straw produced and fraction burned inthe field were retrieved from secondary sources [6].D. Economic AnalysisBenefits to farmers from selling rice straw were alsoinvestigated in this study. Information on the local price ofrice straw was collected via interviews of farmers at the studysites and also based on secondary data. Straw utilization iscategorized into two types, loose rice straw and baled ricestraw (rectangular shape).III. RESULTS AND DISCUSSIONSA. Total Amount of Rice Straw in ThailandTotal amount of rice straw (Table I) was quantified basedon results of field experiments, residue-to-production ratio(RPR), and statistics of rice production. For major rice,production data is from 2009/2010, over the period August2009 to April 2010. For second rice, production data is from2010/2011, over the period February 2010 to October 2010[5].TABLE I: TOTAL AMOUNT OF RICE STRAW IN THAILAND, 2010Categories RPR Products(million tons/y) Rice straw(million tons/y)Irrigated (major) 1.06±0.55 8.14 8.63±4.48Irrigated (second) 0.65±0.28 6.64 4.32±1.86Non-irrigated(major) 0.55±0.11 15.118.31±1.66Non-irrigated(second) - 3.501.93±0.39There are no results for RPR of second rice at thenon-irrigated paddy field. Hence the RPR value of major riceat the same area was applied to estimate the amount of ricestraw produced in non-irrigated area (second rice).The total amount of rice straw produced was found toamount to 23 million tons annually, including 13 million tonsfrom irrigated paddy fields and 10 million tons fromnon-irrigated paddy fields. The RPR in irrigated paddy fieldswas found to be lower than the RPR in non-irrigated paddyfields mainly because of the lower yield at the study sites.The varieties of rice cultivated in major and second rice weredifferent so periods of planting to harvesting were alsodifferent. The major rice varieties required longer period ofcultivation than the second rice varieties, consequently,larger amounts of biomass were produced in the paddy fieldswhere major rice varieties were planted. Hence, the largestsources of rice straw were found to be the major rice varietiesthat are planted in irrigated areas. These are mainly located inthe central part of the country. The smallest sources of ricestraw were found to be the second rice varieties that arecultivated in non-irrigated areas. As non-irrigated areas relymainly on natural resources of water, rain essentially, majorrice was mostly cultivated; only few areas had second rice.Therefore, areas of second rice plantation in non-irrigatedareas were small, another reason for the low amount of strawfound to be produced in such areas during the dry season.B. Amount of Burned Rice Straw in the FieldThe quantity of rice straw burned in paddy fields wereestimated based on the quantity of rice straw found to beproduced in this study and the fraction that is burned in thefield based on secondary information [6]. The results arepresented in Table II along with the amount of ash generatedfrom open burning of rice straw.TABLE II: OPEN BURNING OF RICE STRAW IN THE FIELDCategoriesFractionof burnedrice straw(%)Burned ricestraw(milliontons/y)% ash inburnedstrawAsh(thousandtons/y)Irrigated(major) 49±2 4.23±2.20 15.87±0.88 672±348Irrigated(second) 87±11 3.73 ±1.61 20.61±4.51 770±331Non-irrigated(major) 20±3 1.65 ±0.33 24.70±3.07 408±82Non-irrigated(second) 41±8 0.79 ±0.16 - 196±39From Table II, the amount of rice straw burned in the fieldafter harvesting is found to amount to 10.41 million tons forthe year 2010. Major burned areas concern paddy fieldslocated in irrigated areas accounting for 77% of the totalamount of rice straw burned, the remaining 23% comingfrom burning in non-irrigated areas. Of the 23%, only8% iscontributed by rice straw burning after harvesting second rice.After harvesting rice in irrigated paddy fields, farmerspromptly prepare the land for the next cultivation. The fallowperiod in irrigated paddy fields is therefore quite short, about1 to 2 weeks. Because of abundant water resourcesavailability, rice in irrigated paddy fields can be cultivatedcontinuously throughout the year. The most convenient,cheapest, and fastest way to eliminate rice straw to clear theland is combustion. Therefore, open burning is mainly foundin irrigated areas.The total amount of ash generated from open burning inpaddy fields was found to amount to 2.05±0.80 million tons,which represents 20% of the total amount of rice strawInternational Journal of Environmental Science and Development, Vol. 4, No. 2, April 2013120burned. Therefore, the quantity of mass lost from thecombustion process is 80%, released into the atmosphere inthe form of gaseous and particulate matters. Following theassessment of the amount of biomass consumed as a result ofrice straw burning, this study focuses on its carbon content ascarbon is an important component contributing toclimatechange.C. Carbon Released from Open Burning in the PaddyFieldThe results of carbon analysis showed that there were40%C by mass (±0.7%C, SD) in rice straw and 17%C bymass (±1.5%C, SD) in ash. From the carbon analysis results,the amount of carbon in rice straw, burned rice straw, and ashcould be estimated. In addition, the quantity of carbonreleased from open burning of rice straw was calculated aspresented in Table III.TABLE III: CARBON CONTENT IN RICE STRAW, BURNED RICE STRAW, ASH,AND CARBON RELEASED TO THE ATMOSPHERE FROM OPEN BURNING OFRICE STRAW IN THE FIELDCategories C rice straw(milliontons/y)C burned(milliontons/y)C ash(thousandtons/y)C released(milliontons/y)Irrigated(major) 3.47±1.80 1.70±0.88 117±61 1.58±0.82Irrigated(second) 1.74±0.75 1.50±0.65 135±58 1.37±0.59Non-irrigated(major) 3.34±0.67 0.66±0.13 71±14 0.59±0.12Non-irrigated(second) 0.77±0.15 0.32±0.06 34±7 0.29±0.06Total 9.32±3.37 4.19±1.73 358±140 3.83±1.59From Table III, total amount of carbon contained in therice straw was found to amount to 9.32±3.37 million tons Cand in burned rice straw to 4.19±1.73 million tons C. Theremaining carbon in ash that would be back to the landamounts to 358±140 thousand tons C and the fractionreleased to the atmosphere to 3.83±1.59 million tons C. Asmajor areas of paddy fields burned were found in irrigatedrice fields, consequently, largest amounts of carbon werefound to be released from irrigated paddies during major andsecond rice cultivation, respectively.The fraction of carbon released to the atmosphere that canbe recycled via photosynthesis as carbon biomass in the nextcrop is that corresponding to CO2. According to [7] thecorresponding percentage of CCO2 that can be re-incorporatedinto biomass via such process is 93% translating into3.56±1.48 million tons C. Therefore, the net amount ofcarbon released to the atmosphere from open burning of ricestraw would amount to 268±111 thousand tons C. Mostotherforms of carbon released are CO, TC (BC and OC), and CH4[2]. These gases (CO and CH4) and aerosols (BC and OC)contribute to enhance climate change; however, the problemscould be avoided by suitable management practices of ricestraw.D. Season of Harvesting in ThailandAs observed from Fig. I, period of rice harvesting variesdepending on rice varieties. The harvesting season of majorrice is mainly found during the dry season, while second riceis observed during the wet season. Production of major ricespans over the period August to May of the next year. Thehighest production is found in November. Lowest productionis observed during February - April.Fig. 1. Harvesting season of major and second rice in Thailand, 2009/2010.Second rice is harvested during February - October. Theperiod of major rice and second rice harvesting overlaps overthe period February - April, which correspond to the lateharvesting season of major rice and early harvesting seasonof second rice. Although rice harvesting is lower during thisperiod, serious haze problems are usually observed duringthis time. This is mainly because of open burning from othersources i.e. forest fires, waste incinerations, and openburning of other agricultural residues [1]. February to April isthe period corresponding to the dry season in Thailand, timeduring which relative humidity is at its lowest and goodconditions for ignition of vegetation at their highest. Hence,open burning activities should be carefully monitored andcontrolled in that time.E. Alternative Rice Straw Management PracticesIn order to identify suitable managementpractices of ricestraw in Thailand and reduce open field burning, informationwere collected from farmers via interviews and combinedwith other data from secondary sources.The prohibited period of open burning in Thailand wouldbe from January to April because of serious smoke and hazeproblems, especially in the northern region. The NationalFire and Haze Control Plan of Action (2013) was announcedto control open burning in nine provinces of the northernregion of the country during January 21 to April 10, 2013 [1].Due to dry weather, the quality of straw was good becausethe straw contained low moisture. There was no problemoffungi in dry straw. In addition, the soil in the paddy field wasdried and hard enough for a large machine, a straw baler, tocollect straw in the field. Social benefit of collecting strawout of the field was considered.Cost and benefit of selling straw during dry season wereanalyzed. Most straw was sold by two ways, loose straw andbaled straw. The loose straw would be sold directly to theconsumer that would collect in the field by themselves andtransport by pickup truck. The loose straw was mainly usedin agricultural area, i.e. mulching young plants. Price of thestraw would be per area (4.17-10.42 USD/ha, 30 THB/USD).Advantage of selling loose straw was no cost of strawcollecting. Disadvantage of selling loose straw was onlysmall amount collected because of huge volume of loosestraw.International Journal of Environmental Science and Development, Vol. 4, No. 2, April 2013121Farmers also sold the baled straw that was collected by thestraw baler. The owner of the baler machine is anintermediate merchant thatwould buy the baled straw fromthe farmers and sell to the customers. The cost of the baledstraw consists of the cost of baling (15-20 THB/pack) andcost of moving baled straw out of the field (3-5 THB/pack).The benefit of selling the baled straw was analyzed per pack.The weight of the baled straw is 10-15 kg/pack. Theadvantage of selling the baled straw is high benefit. Thedisadvantage is the lack of straw baler in Thailand. Acomparison of cost-benefit between the loose straw and thebaled straw is presented in Table IV.TABLE IV: COST AND BENEFIT OF RICE STRAWCategories Cost (USD/thousand tons) Benefit (USD/thousand tons)Loose straw - 1.36-2.05Baled straw(dry season) 48,000-66,667 109,333-146,667Baled straw(wet season) 48,000-66,667 66,667-106,667Note: 30 THB/USDFrom Table IV, the highest net benefit is form selling thebaled straw produced during the dry season. The cost ofbaling rice straw is the same between wet and dry seasons;however, the benefit is different because abundant grass wasavailable for feedstock during the wet season so the demandfor baled straw was low during this time. High demands ofbaled straw were found during the dry season so the pricewas nearly double. Net benefits (benefit minus cost)fromselling straw were found to amount to 1.36-2.05USD/thousand tons of loose straw, 18,667-40,000USD/thousand tons of baled straw (wet season), and61,333-80,000 USD/thousand tons of baled straw (dryseason), respectively.Although loose straw gains the lowest net benefit, mostfarmers sell loose straw as straw baler is scarce in Thailand.Thai engineers could produce straw baler but the balingmachine requires labor for manual fastening byrope and so itis not widely used. Most intermediate merchants buy secondhand automatic machines importedfrom other countriesbecause they require little labor and operate more quickly [8].The main reason of burning rice straw in the field insteadof selling is that it is difficult to manage and requirestransport of large volumes of rice straw. Although straw canbe baled into a compressed pack, the volume is still too highfor transport by truck without issues of illegal overloading.Although open burning of rice straw contributes to releasepollutants to the atmosphere, the combustion also providessome benefits. The open burning may help to remove insectsand diseases from the field. The remaining ash left in the fieldafter burning may enable to adjust soil pH and improve soiltexture, useful for rice cultivation. Therefore, open burningcould be done during May to October because the releasedgases and aerosols would be deposited back into the soilthrough raining. In addition, straw collection by machineduring this period is difficult because of wet soil. Moreover,wet straw could not be stored because of fungi problem.The period November to December is the season of majorrice harvesting in non-irrigated paddy fields. As the fallowperiod for the non-irrigated paddy fields is quite long (rice isusually cultivated only once), therefore, the generated strawshould be ploughed back into the soil as organic amendmentto improve soil quality.The rice straw should be collected for various utilizationsi.e. feedstock, material for furniture manufacturer/homebuilding, handicraft, media for mushroom cultivation,mulching in the garden, decorating places, and so on. Theseutilizations could gain value of rice straw instead of burningthat released carbon into the atmosphere for 47.36%.IV. CONCLUSIONSOpen burning of rice straw in the paddy fields releasespollutants into the atmosphere that contribute to enhanceclimate change issues. Alternative management options forrice straw have been suggested in this study including tocollect the straw in dry season (January to April), burn in wetseason (May to October), and plow the straw into the soilinnon-irrigated paddy fields (November to December). Thealternative practices of rice straw management therebyidentified could enable reducing the amount of straw burnedin the field from 10.41±4.29 million tons to4.89±2.34million tons. The released carbon would also be reduced from3.83±1.59 million tons C to 1.81±0.87 million tons Cincluding CCO2 1.69±0.81 million tons C and other carbonforms totaling 0.13±0.06 million tons C.ACKNOWLEDGMENTSK. K. and S.G. Authors express their gratitude to the JointGraduate School of Energy and Environment, KingMongkut’s University of Technology Thonburi and theCenter for Energy Technology and Environment, Ministry ofEducation Thailand, for financial support. The Earth SystemsScience Research and Development Center, PetchPhrachomklao King Mongkut’s University of TechnologyThonburi, and the Higher Education Research Promotion andNational Research University Project of Thailand are highlyappreciated for their research fund support. K. K. and S.G.Authors extend further appreciation to Dr. Sebastien Bonnet,the Aerosol from Biomass Burning to the AtmosphereResearch Group (ABBA), the field experiment team, and thefarmers at the studied sites for their contributions to thiswork.REFERENCES[1] Pollution Control Department of Thailand, “Thailand Country Report:Land and Forest Fire and Haze Situation in 2012 and Preparations for2013,” presented at the Joint Graduate School of Energy andEnvironment, Bangkok, Thailand, December 4, 2012.[2] M. O. Andreae and P. Merlet, “Emission of trace gases and aerosolsfrom biomass burning,” Global Biogeochemical Cycles, vol. 15, no. 4,pp. 955-966, December 2001.[3] J. S. Levine, Biomass Burning and Global Change, 1st ed., London,England: The MIT Press, Introduction, pp. xxxv-x1iii, 1996.[4] M. O. Andreae and P. J. Crutzen, “Atmospherice Aerosols:Biogeochemical Sources and Role in Atmospheric Chemistry,” Science,vol. 276, pp. 1052-1058, May 1997.[5] Office of Agricultural Economics of Thailand, “Thailand CountryReport: Fundamental Agricultural Statistics 2010,” 2011.[6] P. Cheewapongphan and S. Garivait, “Greenhouse gases emission fromrice field residues open burning,” Proc. 1st National Carbon NeutralConf., pp. 501-511, Nonthaburi, Thailand, 2010.International Journal of Environmental Science and Development, Vol. 4, No. 2, April 2013122[7] K.. Kanokkanjana and S. Garivait, “Carbon Released from OpenBurning of Agricultural Residues in Thailand,” presented at theiLEAPS SC- Science Conference, Garmisch-Partenkirchen CongressCentre, Germany, September 18-23, 2011.[8] A. Bridhikitti and K. Kanokkanjana, “Sustainable rice strawmanagement for urban air pollution reduction in bang Bua ThongNonthaburi Province, Thailand,” Case Study Series: ADP 5/2009, pp.1-23, R. Perera, Ed. Thailand: Asian Institute of Technology, 2009.Kanittha K. was born in Bangkok, Thailand on April 6,1979. Educational backgrounds of K. K. are Master ofScience in Environmental Engineering andManagement from Asian Institute of Technology (AIT),Patumthani, Thailand; Bachelor of Science inEnvironmental Resources Chemistry fromKingMongkut’s Institute of Technology Ladkrabang(KMITL), Bangkok, Thailand; and Bachelor of Economics fromRamkhamhaeng University (RU), Bangkok, Thailand.Currently, she is a Ph. D. Candidate in Environmental Technology at TheJoint Graduate School of Energy and Environment (JGSEE), the Center forEnergy Technology and Environment (CEE) located at King Mongkut’sUniversity of Technology Thonburi (KMUTT) in Bangkok, Thailand.Research interests concern atmospheric environment. Current researchinterest is emissions released from open burning of agricultural residues.Previous research interest is simulating dispersion air quality models at pointsources in industrial areas.Miss Kanittha got First class honored when graduated Bachelor degree,scholarship granted by Her Majesty the Queen during Master degree,Fellowship granted by The Joint Graduate School of Energy andEnvironment (JGSEE); and research fund granted by Earth SystemScience(ESS), National Research University (NRU), and Petch Phrachomklao(KMUTT) during Ph.D. candidatRegardsSamar Singh