Life Cycle Assessment of Milled Rice Production: Case Study in Thailand

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1 European Journal of Scientific Research ISSN X Vol.30 No.2 (2009), pp EuroJournals Publishing, Inc Life Cycle Assessment of Milled Rice Production: Case Study in Thailand Sakaorat Kasmaprapruet Chemical Engineering Department, Faculty of Engineering, Thammasat University Pathumtani 12120, Thailand Woranee Paengjuntuek Chemical Engineering Department, Faculty of Engineering, Thammasat University Pathumtani 12120, Thailand Phanida Saikhwan Chemical Engineering Department, Faculty of Engineering, Thammasat University Pathumtani 12120, Thailand Harnpon Phungrassami Chemical Engineering Department, Faculty of Engineering, Thammasat University Pathumtani 12120, Thailand National Center of Excellence for Environmental and Hazardous Waste Management Faculty of Engineering, Thammasat University, Pathumtani 12120, Thailand Abstract Nowadays, concerns with environmental issues are increasing considerably in every agricultural sector. To preferably avoid, or at least reduce the environmental impacts, food production should involve assessing the environmental impact of the entire food chain. One of the well known methodologies used for the evaluation of the environment is a life cycle assessment (LCA). In this paper we presents, as a case study, the results of an LCA analysis of milled rice production, from rice cultivation to the mill, in order to determine the environmental load of rice production. The results show that the global warming potential of rice production per kg was E+03 gco 2 -eq, followed by gso 2 -eq of acidification and gno 3 - -eq of eutrophication. In this study, 95% of the global warming inputs to the system are associated with the cultivation process, 2% with the harvesting process and 2% with the seeding and milling processes. Keywords: Life cycle assessment; rice production; global warming 1. Introduction Rice is the world s most important staple food crop with more than half of the world s population relying on rice as the major daily source of calories and protein. Rice is also a major agricultural product in Thailand. The area cultivated with rice is about 110,400 square kilometers for the year 2008, representing approximately 20 percents of the total area of Thailand (Thai Rice Exporters Association).

2 Life Cycle Assessment of Milled Rice Production: Case Study in Thailand 196 Thailand was the number one rice exporter in the world in the year 2007 (Thai Rice Exporters Association), as shown in Figure1. Many of the environmental problems are caused from rice production: the use of fertilizers increase pollution of the ecosystem; greenhouse gases are generated, especially methane gas; flooding of rice fields cuts off oxygen supply, then anaerobic microorganisms ferment the organic matter in the soil, causing the production of methane (Ferry, 1992). Methane produced from rice paddies accounts for up to 20% of global methane emissions in the world (Thitakamol, 2008). The emission of methane from rice fields is dependent on many factors such as fertilizers, rice characteristics and soil environment (Mitra et al., 1999). In Thailand, the average methane emission in rice paddies is about gch 4 per kilogram of grain (Saenjan and Saisompan, 2004). This LCA study of commercial mills was based on rice mill in Pijit province. Figure 1: World rice exporters (Thai Rice Exporters Association). 2. Methodology 2.1. Life Cycle Assessment There are many techniques in quantifying the impact of agricultural activities on the ecosystem. One such technique used in life cycle assessment is the process of evaluating the effects that a product has on the environment over the entire period of its life cycle. The food industry uses the LCA to identify the steps in the food chain that have the largest impact on the environment in order to target improvement efforts (Ohlsson, 2006). In LCA, the various inputs include resources such as, energy or the chemicals used for the activities throughout the food chain. According to the International Organization of Standardization (ISO), LCA is divided into four phases: goal and scope definition, inventory analysis, life cycle impact assessment and interpretation (ISO14040, 2006) Goal and Scope Definition The first step to perform LCA is to set the goal and scope definition is carried out. The goal of the study should include a statement of the reason for carrying out the study. The objectives of this study were to identify the environmental impacts that occur in the life cycle of milled rice and to suggest and implement energy conservation options in the rice mill. The scope of LCA mostly consists of the

3 197 Sakaorat Kasmaprapruet, Woranee Paengjuntuek, Phanida Saikhwan and Harnpon Phungrassami functional unit (FU), the system boundary, allocation procedures, data requirements and assumptions or limitations. Functional Unit The functional unit is a measure of the function of the studied system and provides a reference unit to which the inventory data can be related. The reference unit translates the abstract functional unit into specific product flows for each of the compared systems, so that product alternatives are compared on an equivalent basis (Weidema et al., 2004). In this study, the functional unit has been defined as one kilogram of milled rice at the mill gate, but excludes the packaging. System Boundary A system boundary is a collection of unit processes by flows intermediate products which perform one or more defined function (ISO14040, 2006). A system boundary is subdivided into a set of unit processes. Unit processes are linked to one another by flows of intermediate products. The system boundary in this study includes the stages of production from cultivation until the product reaches the mill gate, as shown in Figure 2. The system boundary is subdivided into 4 main unit processes, which are described as follow. (1) Rice seeding, cultivation and harvesting: The fields are typically plowed, the plow being drawn by a diesel powered tractor. Seeds are planted by hand in rows in the rice fields, with water levels maintained to prevent weed growth and ensure that there is sufficient water for the plants to grow. Fertilizer such as ammonium sulfate is commonly used in Thailand. Harvesting is the process of collecting the rice crop from the field. Grains are commonly harvested by a diesel tractor. The grain at this stage, however, is not suitable for eating. The husk and the bran has to be removed, which is done in the milling process. (2) Transportation of paddy: The average transport distance was assumed to be 50 kilometers using a diesel powered pick-up. (3) Drying: Drying is the process of heat transfer in order to remove the excess moisture from the grains; rice husk is the source of energy. Now, the rice is ready for milling. (4) De-husking and milling: The husk and the bran are removed in these processes. The output of a milling process comprises the main product, milled rice and by-products such as the husk, the bran layer and the broken rice. Figure 2: A simplified system boundary of milled rice.

4 Life Cycle Assessment of Milled Rice Production: Case Study in Thailand Inventory Analysis Life Cycle Inventory (LCI) of the LCA methodology is essentially the collection of data. This step includes data collection for inputs and outputs of the product system. The data from cultivation and harvesting were reviewed and collected. However, there were some data such as fertilizers and chemicals manufacturing were impossible to be collected, therefore they were cited from some international databases such as database from SimaPro software program. Electricity consumption of rice mill was collected based on knowledge available in Thailand. The detail of data specification is shown in Table 1. The allocation step of this study was performed based on economic allocation as shown in Figure 3. The environmental inputs and outputs are shown in Table 2. Table 1: Data specification. Unit process Specific data General data Production of energy Electricity Diesel Production of raw material Ammonium sulfate 2,4 Dichlorophenoxy acetic acid Carbofuran Production of rice Cultivation Harvesting Drying Milling Figure 3: Economical allocation of a rice mill.

5 199 Sakaorat Kasmaprapruet, Woranee Paengjuntuek, Phanida Saikhwan and Harnpon Phungrassami Table 2: Inventory data of milled rice. Parameters Per 1 kg of rice Environmental inputs E+00 Diesel (MJ) E-02 Electricity (kwh) E-03 Energy used in transportation-diesel (litre) E-01 Rice husk (kg) E-01 Ammonium sulfate (kg) E-04 2,4 Dichlorophenoxy acetic acid (kg) E-03 Carbofuran (kg) Some environmental output Emissions from fuel combustion CO 2 (g) E+02 CH 4 (g) E-02 N 2 O (g) E-04 CO (g) E-02 No x (g) E-01 Emissions due to electricity use CO 2 (g) E+01 CO (g) E-03 No x (g) E-04 SO 2 (g) E-05 Emissions due to transportation CO 2 (g) E+01 CH 4 (g) E-03 N 2 O (g) E-04 CO (g) E-03 No x (g) E-02 Emissions due to rice husk combustion CO (g) E-01 No x (g) E+00 SO 2 (g) E Life Cycle Impact Assessment (LCIA) LCIA aims to examine the product system from an environmental perspective using impact categories and category indicators connected with the LCI results, according to ISO Environmental impacts were quantified in terms of a common unit for that category. Table 3 shows selected impact categories with related units, contributing elements and characterization factors. The used impact assessment categories in this study cover global warming arising from greenhouse gas emissions, acidification from acid gas emissions, eutrophication as a result of nitrifying and phosphorus emissions.

6 Life Cycle Assessment of Milled Rice Production: Case Study in Thailand 200 Table 3: Selected impact categories. Impact category Contributing elements Characterization factors Unit Energy use Energy Consumption 1 MJ CO 2 1 CH 4 25 Global warming a N2 O 320 gco 2 -equivalents CO 2 SO 2 1 NO x 0.7 Acidification a NH gso 2 -equivalents - NO NO No x 1.35 N2 O 2.82 Eutrophication a NH gno - 3 -equivalents N PO P a Based on Denmark s LCA Handbook (Wenzel, 1997). 3. Results and Discussion Results presented in this work are related to three aspects; (i) the energy use in the rice cultivation and rice mill, and (ii) the environmental impacts of the product system boundary Energy Use The data on the energy used in the cultivation and rice processing were collected. In the study, energy usage was divided into fossil fuel, electricity and biomass energy (rice husk). When comparing the total energy required for different activities, the biomass energy was recalculated to its primary energy carrier. The heating value for rice husk is about 14 MJ/kg (Quaak et al., 1999). The contribution in this energy consumption is measured in MJ. Figure 4 shows the average energy demand around the system boundary of rice production. From this chart it can be seen that the drying process is the largest energy consuming process, which consumes 55% of energy in total, followed by the harvesting process (15%), cultivation process (10%), seeding process (10%), transportation (6%) and milling process (4%). Figure 4: Energy demand of rice production in each process.

7 201 Sakaorat Kasmaprapruet, Woranee Paengjuntuek, Phanida Saikhwan and Harnpon Phungrassami 3.2. Environmental Impact Based on LCA Methodology LCA is a step towards using the information in order to develop sustainable farming practices and food processing operations (Narayanaswamy et al., 2002). The emissions of the system boundary have been grouped into impact categories as shown in Table 3. The results of LCA are reported in terms of equivalent quantities of reference substances, for instance, CO 2 for climate change impacts, SO 2 for - acidification, NO 3 for eutrophication, etc. In this paper, three impact categories were considered: global warming, acidification and eutrophication. The summary of environmental impacts associated with the production of 1 kg of rice is shown in Table 4. Table 4: Environmental impacts of rice production per kg. Environmental theme and units Global warming, gco 2 -eq Acidification, gso 2 -eq Eutrophication, gno - 3 -eq Value E E E Global Warming Figure 5 shows the result of global warming characterizations of the different processes in rice production. In this study, 95% of the global warming inputs to the system are associated with the cultivation process, 2% with the harvesting process and 2% with the seeding and milling processes. Thus, the cultivation process contributed a significant share of the total impacts. The impact during cultivation is largely due to methane emission from rice paddy, 43% of the global warming potential. The emissions of methane from rice paddy are expected to continue as the second largest source of total greenhouse gases in Thailand (Wenzel et al., 1997). To reduce methane emissions from paddy fields, the options include using enhanced rice production technology such as minimizing the use of green manure and substituting pre-fermented compost from farm residues, adding nitrate or sulfate containing nitrogen fertilizer to suppress methane gas production or; change rice cultivation practices (Wenzel et al., 1997). In addition, water management had a stronger dominating effect on methane emissions than the type of fertilizers had. It was found that methane emission per unit grain from direct-wet-seeding rice with continuous flooding were gch 4 per kg grain and intermittent soil aerating provided gch 4 per kg grain (Saenjan and Saisompan, 2004). Figure 5: Distribution of global warming potential in rice production chain.

8 Life Cycle Assessment of Milled Rice Production: Case Study in Thailand Acidification The acidification emissions of different processes in rice production are presented in Figure 6. Substances such as SO 2, NO x and NH 3 contributed to acidification. The total acidification for this study was gso 2 -eq. The cultivation process emitted the largest amount of acidification emissions (51%), followed by the drying process (42%), harvesting (3.4%) and, seeding (2.7%). This acidification potential was caused mainly from the combustion of rice husk (35%), followed by the production of ammonium sulfate (18.7%) and the production of carbofuran (15.3%). Figure 6: Distribution of acidification potential in the rice production chain Eutrophication Eutrophication is an impact on ecosystems from substances containing nitrogen or phosphorus. If these substances are added in the ecosystem, the growth of algae or plants will increase. This can cause the occurrence of situations without oxygen in the bottom strata due to increased algal growth (Wenzel et al., 1997). Figure 7 shows the results of eutrophication characterizations of the different processes in the system boundary. The cultivation process had the highest amount of emissions (81%), followed by the drying process (17%), harvesting (0.85%), seeding (0.6%) and, transportation (0.3%). The highest eutrophication impact caused by emission of fertilizer was during the cultivation process. The lowest eutrophication impact was caused by electricity use in the milling process. 4. Conclusion The study shows the results of a simplified LCA performed on 1 kilogram of rice. Seeding, cultivation, harvesting, transportation and milling were checked. The contribution of energy consumption from the drying process was the highest and milling process energy consumption was the lowest. The cultivation process has the biggest environmental impact for the three environmental impact categories considered.

9 203 Sakaorat Kasmaprapruet, Woranee Paengjuntuek, Phanida Saikhwan and Harnpon Phungrassami Figure 7: Distribution of eutrophication in the rice production chain. References [1] Thai Rice Exporters Association, Available online at: [2] Thai Rice Exporters Association, Available online at: [3] Ferry, J.G., 1992, Biochemistry of methanogenesis. Critical Reviews in Biochemistry and Molecular Biology 27(6), [4] Thitakamol, T., 2008, Influence of Distillery Slop on Methane Emission in Rice Paddies. EnvironmentAsia 1(1), [5] Mitra, S., Jain, M.C., Kumar, S., Bandyopadhyay, S.K. and Kalra, N., 1999, Effect of rice cultivars on methane emission. Agriculture, Ecosystems & Environment 73, [6] Saenjan, P. and Saisompan, C., 2004, Economic Return of Rice Production from Methane Mitigated Rice Yields. Journal of Agriculture 20(3), [7] Ohlsson, T., 2006, Food Waste Management by Life Cycle Assessment of the Food Chain. Journal of Food Science 69(3), CRH107-CRH109. [8] ISO14040, 2006, Environmental management-life cycle assessment-principles and framework. [9] Weidema, B., Wenzel, H., Petersen, C. and Hansen, K., 2004, The Product, Functional Unit and Reference Flows in LCA, Environmental News No. 70, Danish Ministry of the Environment. [10] Quaak, M., Knoef, H. and Stassen, H., 1999, Energy from Biomass. A Review of Combustion and Gasification Technology. World Bank Technical Report No Page. 5. [11] Narayanaswamy, V., Altham, J., Berkel, R.V. and McGregor, M., 2002, A Primer on Environmental Life Cycle Assessment (LCA) for Australian Grains, Curtin University of Technology, Available online at: [12] Wenzel, H., Hauschild, M. and Alting, L., 1997, Environmental Assessment of Products: Volume 1 Methodology, tools and case studies in product development, Chapman&Hall, UK.