Estimates and predictions of greenhouse gases emissions from open rice straw burning in quang ninh district, Quang Binh province

1140 ESTIMATES AND PREDICTIONS OF GREENHOUSE GASES EMISSIONS FROM OPEN RICE STRAW BURNING IN QUANG NINH DISTRICT, QUANG BINH PROVINCE MSc. Hoang Anh Vu vuhoang304@gmail.com MSc. Vo Thi Nho ngocnho256@gmail.com The faculty of Agriculture, Forestry and Fisheries, Quang Binh University, Quang Binh, Viet Nam. Abstract: Quang Ninh district, Quang Binh province is an agricultural district, which workers in the agricultural sector accounted for more than 60%. In 2018, the quantity of rice straw in Quang Ninh district was approximated of about 74,103tons. In the summer-autumn season, the quantity of rice straw was about 43,853 tons (account 59% of the year). The result of 200 local farmers showed that open rice straw burning is the most common activity in the summer-autumn season (73%). In the winter-spring crop, 60% of rice straw is used for animal husbandry, 13% of rice straw is mixed with cow dung, manure for composting. Based on the quantity of rice straw burning on the fields, the greenhouse gas emissions CO2, CH4, CO, PM10 was estimated by using research results of Gadde B et al 2009 and the ABC EIM guidelines. The results using research results of Gadde B et al 2009 show that CO2 emissions are the largest with 44,405.9 tons/year (accounting for 96.2% of total emissions). In addition, there are small quantities of other gases such as CO (1055.4 tons/year), CH4 (36.5tons/year), PM10(112.5tons/year). The total emissions from open rice straw burning in Quang Ninh district by using research results of Gadde B et al 2009 have similar values by using the ABC EIM guidelines on case of average emissions. Utilizations of rice straw to produce microbiological organic compost is suitable practices that need to study to reduce rice straw open burning activity in the next time. Keywords: Quang Ninh district; air pollution; green house gas emissions; rice straw. 1. Introduction One of the causes of climate change is the emission of greenhouse gases from agriculture and industry. In agricultural production, when harvesting rice, 10 years ago Vietnamese farmers chose to collect the straw for cattle feeding and fuel for 1141 cooking, but with the decrease in number of cattle and buffalos due to increased mechanisation, development of industrial cattle feed and use of gas stove, most modern farmers choose to burn their rice straw, while only some incorporate the straw into the soil by ploughing instead, as a cheap disposal method. Recent research reveals that while in the rural areas, 30-40% of the rice straw is burnt on the field; the figure in the suburban area is at 60-70% [5]. That practices will pollute the air, especially increasing greenhouse gases including dust PM25, PM10, SO2, NOx, CO, CO2[3]... The determination amount of greenhouse gases arising from the burning of straw is the basis to proposal of mitigation solutions. Quang Ninh district, Quang Binh province is an agricultural district, which workers in the agricultural sector accounted for more than 60%. In 2018, the total food output is 85,760 tons [1]. The strengthening agricultural production led to increase the quantity of agricultural waste such as rice straw, pesticides packaging, cow dung... At present, Quang Ninh district haven’t a reasonable plan to collect and treat agricultural solid waste. So, Farmers treat waste in the traditional way such as burning, burying or disposing directly into the environment. This activity will have an adverse impact on the soil, water, air environment and people's health. In the world, there have been some studies on emissions from burning straw such as research of Gadde B et al in 2009, the ABC EIM guidelines. However, in Vietnam, studies related to the burning of straw in the field are limited due to human resources and funding. This study was conducted to examine and calculate the amount of emissions from straw burning in the field, the case study: Quang Ninh district, Quang Binh province. The results of the study are the basis for the proposed solution to reduce the burning of straw. 2. Materials and Method 2.1. Study Area Quang Ninh is a district of Quang Binh province in the North Central Coast of Vietnam. Because of the rich soils and the suitable climate conditions, Quang Ninh district is the highest rice-producing area in Quang Binh province according to the density of rice paddy fields and greatest rice production, with 2 growing seasons per year. The first growing season in Quang Ninh district typically called Winter-Spring crop begins at the end of December, and the harvest is from the end of June to mid- July. The second growing called Summer-Autumn crop begins 15–20 days after the first season has ended, and the harvest is from mid-November to early December. However, recently in Summer-Autumn crop, most local farmers cultivate rice in the form of regeneration [2]. 1142 Figure 1. The location of Quang Ninh district, Quang Binh province[1] 2.2. Data collection The data collection methods used in the conduct of the case studies consisted of household survey, focus group discussions (FGD), and key informant interviews (KII). (1) Household survey were used to gather information from 200 farmer households lived in Quang Ninh district about the area of rice cultivation in two crops of winter-spring and summer-autumn crop and the productivity of the crop. (2) FGDs were held to enable the primary stakeholder participants to discuss openly their perceptions and views. The method also aimed to gather information such as: the current method to treat of straw of the local people, people's views on the harmful effects of burning straw. (3) KIIs were conducted with key community leaders to determine the straw burning in the field -related problems in Quang Ninh district. 2.3. Data analysis 2.3.1. Ratio of the amount of straw / rice yield Ratio of the amount of straw / rice yield can be calculated as: 𝑆𝐺𝑅 = 𝑤𝑟 𝑤𝑙 × 100 % (Eq.1) 1143 Where SGR is ratio of the amount of straw / rice yield (%); Wr is dry weight of straw (kg) and Wl is rice yield (kg). 2.3.2. The amount of straw burned in the field The amount of straw burned in the field in 2018 can be calculated as: 𝑄𝑠𝑡 = 𝑄𝑝 × 𝑆𝐺𝑅 × 𝑘 (tons) (Eq.2) Where Qp is rice yield in 2018 (tons); SGR is ratio of the amount of straw / rice yield (%) and k is percentage of straw burned in the field (%) . 2.3.3. The emissions from burning straw The greenhouse gas emissions can be calculated by using research results of Gadde B et al 2009 and the ABC EIM guidelines. a. According to research by Gadde B et al 2009 The emissions from burning straw can be calculated as: 𝐸𝑖 = 𝑄𝑠𝑡×𝐸𝐹𝑖×𝐹𝑐𝑜 1000 (tons/year) (Eq.3) Where Ei is the emission of air pollutant i from burning straw (tons/year); Qst is the amount of straw burned in the field (tons); EFi- the emission factor (EF) of pollutant i in kg/tons dry matter burnt and Fco is the combustion factor (dimensionless), The IPCC recommended Fco value of 0.8 for rice residues was used in this study. Table 1. The emission factor EFi according to research by Gadde B et al 2009[3] Pollutants CO2 CH4 CO SO2 NOx PM10 PM2.5 EFi (kg/tons) 1460 1.2 34.7 2.0 3.1 3.7 12.95 b. According to the ABC EIM guidelines The emissions from burning straw can be calculated as: 𝐸𝑖 = 𝑄𝑠𝑡×𝐸𝐹𝑖×µ 1000 (tons/year) (Eq.4) Where Ei is the emission of air pollutant i from burning straw (tons/year); Qst is the amount of straw burned in the field (tons); EFi- the emission factor (EF) of pollutant i in kg/tons dry matter burnt and µ is the performance of straw burning, µ=0.85. Table 2. The emission factor EFi according the ABC EIM guidelines[4] Pollutants CO2 CH4 CO SO2 NOx PM10 PM2.5 Emission levels Low 791 9.6 64.2 0.18 0.62 3.5 3.2 Medium 1,200 9.6 93 0.18 1.81 9.1 8.3 High 1674 9.6 180 0.4 3.43 9.1 8.3 1144 3. Results The research has determined the amount of straw produced after harvest in Quang Ninh district in 2018 and the ratio of the amount of straw / rice yield. The research has estimated the amount of greenhouse gas emissions from burning of straw in Quang Ninh district using research results of Gadde B et al 2009 and using the ABC EIM guideline. The research has proposed solution to reduce the burning of straw in Quang Ninh district. 4. Discussion and Conclusion 4.1. Ratio of the amount of straw / rice yield SGR According to survey results, in Quang Ninh district, there are two rice crops: Winter-Spring and Summer-Autumn. The average rice yield of Summer-Autumn and Winter-Spring crop is respectively 5.8 tons/ha and 2.5 tons/ha. In Summer-Autumn crop, Farmers cultivate rice in the form of regeneration. Table 3. The ratio of the amount of straw / rice yield in Winter-Spring crop Sample Winter-Spring crop Averaging The biggest The smallest Sample 1 0.86 0.90 0.83 Sample 2 0.73 0.80 0.69 Sample 3 0.75 0.83 0.70 Sample 4 0.80 0.85 0.77 Sample 5 0.81 0.85 0.78 Averaging 0.79 (Source: Summary of questionnaire results) Table 4. The ratio of the amount of straw / rice yield in Summer-Autumn crop Sample Summer-Autumn crop Averaging The biggest The smallest Sample 1 1.06 1.12 0.92 Sample 2 1.07 1.10 1.00 Sample 3 0.96 1.05 0.91 Sample 4 0.90 1.00 0.85 Sample 5 1.00 0.92 1.05 Averaging 1.00 (Soure: Summary of questionnaire results) 1145 Table 3 and 4 show that the ratio of the amount of straw / rice yield in Winter- Spring crop (the average value of 0.79) is lower than Summer-Autumn crop (the average value of 1.00). The ratio of the amount of straw / rice yield value in this study is almost identical to result of research by Gadde B et al 2009 (the ratio of the amount of straw / rice yield is 0.75). 4.2. The types of straw treatment in Quang Ninh district According to that survey, in Quang Ninh district, there are four common types of rice straw treatment and management: burning, composting, feeding and giving to neighbours. 73% of rice straw generated in the Summer-Autumn season was burnt directly on the field. In the Winter-Spring season, due to frequent rain, the rate of burning rice straw was decrease into 14%. This survey also confirms that most of farmers tended to continue burning rice straw in the following years. Table 5. Types of rice straw treatment in Quang Ninh district Types of rice straw treatment Percentage (%) Winter-Spring crop Summer-Autumn crop Burning 19 73 Composting 13 5 Feeding 60 22 Giving to neighbours 8 - (Source: Summary of questionnaire results) In the Winter-Spring season, 60% farmers chose to collect the straw for cattle feeding and fuel for cooking. But, In the Summer-Autumn season with the decrease in number of cattle and buffalos due to increased mechanisation, development of industrial cattle feed and use of gas stove, most farmers choose to burn their rice straw. Moreover, in recent years, combine harvester has been used more and more, the amount of straw spread on the fields is difficult to collect. 4.3. The amount of straw burned in the field in Quang Ninh District The amount of straw burned in the field in 2018 was estimated using Eq. (2) and the ratio of the amount of straw / rice yield (%) in table 3 and percentage of straw burned in the field in table 5. 1146 Table 6. The amount of straw burned in the field in Quang NinhDistrict in 2018 Season Winter- Spring Summer- Autumn Total Rice yield (tons) 55,510 30,250 85,760 The ratio of the amount of straw / rice yield 0.79 1.00 The amount of straw (tons) 43,853 30,250 74,103 percentage of straw burned (%) 19 73 The amount of straw burned in the field (tons) 8,332 22,083 30,415 (Source: the author's calculation results) 4.4. Estimation of greenhouse gas emissions from burning of straw in Quang Ninh District The amount of greenhouse gas emissions from burning of straw in Quang Ninh district was estimated using Eq. (3), Eq. (4) and the amount of straw burned in the field in 2018 in table 6. a. According to research by Gadde B et al 2009 Table 7. The greenhouse gas emissions from burning of straw in Quang Ninh district in 2018 Pollutants CO2 CH4 CO SO2 NOx PM10 PM2.5 Ei (tons/yr) Winter- Spring 12,164.7 10 289.1 16.7 25.8 30.8 107.9 Summer- Autumn 32,241.2 26.5 766.3 44.2 68.5 81.7 286 Total 44,405.9 36.5 1055.4 60.9 94.3 112.5 393.9 (Source: the author's calculation results) The results using research results of Gadde B et al 2009 show that CO2 emissions are the largest with 44,405.9 tons/year (accounting for 96.2% of total emissions). In addition, there are small quantities of other gases such as CO (1055.4 tons/year), CH4 (36.5 tons/year), PM10 (112.5 tons/year). 1147 b. According to the ABC EIM guidelines Table 8. The greenhouse gas emissions from burning of straw in low emission level in 2018 Air Pollutant Low emission Medium emission High emission Winter- Spring Summer- Autumn Total Winter- Spring Summer -Autumn Total Winter- Spring Summer- Autumn Total CO2 6591 17468 24059 9998 26500 36498 13948 36967 50915 CH4 80 212 292 80 212 292 80 212 292 CO 535 1418 1953 775 2054 2829 1500 3975 5475 NOx 1 4 5 1 4 5 3 9 12 SO2 5 14 19 15 40 55 29 76 105 PM10 29 77 106 76 201 277 76 201 277 PM2.5 27 71 98 69 183 252 69 183 252 Total 7268 19,264 26,532 11,014 29,194 40,208 15,705 41,623 57,328 (Source: the author's calculation results) The results using the ABC EIM guidelines show that CO2 emissions are the largest from 24,059 to 50,915 tons/year corresponding to low to high emission. CO2 emissions accounts for 96.2% of total emissions. Next, the amount of CO gas emissions from 1,953 to 5,475 tons/year, accounting for an average of about 7% of total emissions. The total emissions generated in the high emission is 57,328tons, 2.16 times higher than the low emission (26,532 tons) and 1.4 times compared medium emission (40,208 tons). The total emissions from open rice straw burning in Quang Ninh district by using research results of Gadde B et al 2009 have similar values by using the ABC EIM guidelines on case of average emissions. 4.5. Proposed Solutions Compost is the relatively stable product that results after organic materials decompose. Compost usually contains relatively low amounts of major nutrients but they contain micronutrients, enzymes and microorganisms that are not often found in inorganic fertilizer. The process of decomposing rice straw generates high temperature, keeping pathogen level low and reducing the viability of weed seeds may contain in rice straw. Straw must be removed from the field before piling and spreading in the field. The decomposing will take at least 1 to 1.5 month. Recently, in Vietnam, a newly invented biotic product, namely Fito-Biomix RR, will shorten the process of decomposing straw. So, with a cheap price, easy implementation, farmers tends to using of rice 1148 straw to produce microbiological organic compost when they have spare time and area for composting process. This management method could be applied in most of regions in Vietnam. 4.6. Conclusion The research has determined the amount of straw produced after harvest in Quang Ninh district in 2018 is 85,760 tons. The ratio of the amount of straw / rice yield is 19% in winter-spring crop and 73% in summer-autumn crop. The amount of greenhouse gas emissions from burning of straw in Quang Ninh district was estimated: According to research by Gadde B et al 2009: CO2 emissions are the largest with 44,405.9tons/year (accounting for 96.2% of total emissions). In addition, there are small quantities of other gases such as CO (1055.4 tons/year), CH4 (36.5 tons/year), PM10 (112.5 tons/year). According to the ABC EIM guidelines: CO2 emissions are the largest from 24,059 to 50,915 tons/year corresponding to low to high emission. CO2 emissions accounts for 96.2% of total emissions. Next, the amount of CO gas emissions from 1,953 to 5,475 tons/year, accounting for an average of about 7% of total emissions. The total emissions generated in the high emission is 57,328tons, 2.16 times higher than the low emission (26,532 tons) and 1.4 times compared medium emission (40,208 tons). Utilizations of rice straw to produce microbiological organic compost is suitable practices that need to study to reduce rice straw open burning activity in the next time. 5. References 1. People's Committee of Quang Ninh district, (2018), Socio-economic report of Quang Ninh district in 2018, Unpublished document. 2. DENRO (Districtial Environment and Natural Resource Office), (2015), Integrated Resource Management Plan. Unpublished document. 3. Gadde B., Bonnet S., Menke C., and S. Garivate, (2009), Air pollutant emissions from rice straw open field burning in India, Thailand and the Philippines, Journal of Environmental Pollution, Vol. 157,p1554-1558. 4. Ram M. Shrestha, N. T. K. Oanh, D. A.Permadi United, T. Kanabkaew, (2013), Atmospheric Brown Clouds Emission Inventory Manual, United Nations Environment Programme. 5. Tran S.N, Nguyen T.Q.N, Nguyen H.C, Nguyen V.C.N, Le H.V and Ingvorsen K, (2014), To quantify the seasonal rice straw and its use in different provinces in the Vietnamese Mekong Delta, Can Tho University Science Journal.