Relationship between agricultural waste and greenhouse gases in Dong Thap Province
Based on the assessment of the status of greenhouse gas (GHG) emissions in each field of agricultural production in Dong Thap Province according to IPPC and related studies.
Project has proposed solutions to reduce GHG emissions in each respective field and estimate the effectiveness of GHG emission reduction.
The results show that the total GHG emissions in 2021 and 2022 are 8,697.91 and 8,872.88 thousand tons of CO2 equivalent/year; GHG emissions is mainly from farming activities (accounting for 73% to 78%), followed by agricultural waste (16% to 20%), aquaculture (about 6%) and livestock farming (< 1%).
However, when applying the proposed solutions, the effectiveness of reducing GHG emissions reaches 73,4%. If afforestation is applied and maintained, Dong Thap Province will continue to reduce GHG emissions by about 80%. Besides, to be effectively and successful in GHG emissions reducing, it is necessary to have financial support from the Government and people’s awareness in environmental protection.
1. Introduction
Vietnamese agriculture accounts for about 30 percent of national GHG emissions. The main types of GHG emissions in the agricultural field in-clude CH4, N2O and CO2. Quantifying emissions of each type of GHG in ag-ricultural production show that agri-cultural activities are also the cause of global climate change.
In Dong Thap Province, the agri-cultural sector accounts for about 8.62 percent GRDP, the agricultural land accounts for about 75.39 percent of the natural area of the Province [3]. To be able to evaluate the status of GHG emissions as well as the potential and effectiveness of reducing GHG emis-sions in agriculture, Dong Thap Province needs to deploy GHG emissions calculations in agricultural production sectors.
Estimating GHG emissions can help the Province set quantitative emissions reduction targets in the next period, monitor and evaluate efforts to reduce GHG emissions compared to usual emissions scenarios according to timelines consistent with the national GHG inventory activity.
2. Data Collection
2.1. Overview of agriculture in Dong Thap Prov-ince in 2022
Dong Thap Province’s agriculture sector has proactively implemented many production transformation solutions to promote growth, ensure food security and bring high eco-nomic efficiency to farmers.
– Livestock farming: The Province’s livestock industry has prospered, with many large-scale investment projects ap-plying high technology in the form of production chains have been built and operated. The livestock industry is con-tinuing to shift from small-scale farms, not ensuring biose-curity and low efficiency to medium and large-scale farms ensuring biosecurity.
– Fishery: Aquaculture production and fishery catching reached 616.9 thousand tons, an increase of 1.05% com-pared to 2021, of which aquaculture production reached 596.7 thousand tons, accounting for 96.7%. Aquaculture area is concentrated in Tam Nong, Cao Lanh and Chau Thanh districts.
– Crop production: Total production cerealsreached 3,270.5 thousand tons, a decrease of 104.3 thousand tons compared to 2021, of which paddy production reached 3,235 thousand tons, a decrease of 104 thousand tons (Spring paddy production reached 1,384.8 thousand tons, a decrease of 50.2 thousand tons; Autumn paddy production reached 1,850.2 thousand tons, a decrease of 53.8 thousand tons). Perennial crops and fruit crops (oranges, tangerines, mangoes, longans) increased compared with in 2021.
– Pesticides (plant protection chemicals): Dong Thap Province’s paddy area ranks third in the country and its fruit tree area is quite large. Therefore, every year, people use many pesticides to pre-vent pests and diseases. According to the report of DongThap Plant Protec-tion and Cultivation Sub-Department, the total amount of fertilizer used is 350,642 tons per year, and pesticides are 8,974 tons per year.
– Fertilizers: Farmers are used to us-ing chemical fertilizers for crops and are not used to using organic fertilizers. The amount of fertilizer used for rice cultiva-tion is gradually decreasing with area; For other crops such as vegetables, corn, pota-toes… the amount of fertilizer used gradu-ally increases over cultivated area.
2.2. Agricultural waste
By-products in farming: According to statistics from the Institute for Agricul-tural Environment (2018), The amount of by-products from paddy is the largest with over 45 million tons of straw/year, followed by sugarcane with the amount of sheaths and old leaves is over 20 million tons/year, next leaf stalks of corn, cassava plant, vegetables and coffee husks[11]. Ag-ricultural by-products are being left over and burned. They are not used effectively, causing emissions and environ-mental pollution. With the ratio of straw/paddy is 1.05/1 (Trần Anh Tuấn et al., 2019), the estimated number of straw by-products gen-erated is about 3,396.75 thousand tons in 2022.
– Livestock waste: livestock waste is mainly manure, dead animal carcasses, leftover ani-mal food, bedding materials and other waste, with moisture from 50% to 83% and high NPK ratio. With the emission coefficient ref-erenced from the study of Vũ Chí Cường (2013), the total amount of livestock waste is 1,531.75 tons of solid waste and 1,170 tons of liquid waste.
– Aquaculture waste: Waste in aquaculture is wastewater, sludge… formed mainly from shrimp and fish feces, leftover food, algae, chemicals (lime, zeo-lite…) used in the farming process, with solid waste generated from shrimp farming is 123 tons/crop/ha and wastewater is more than 5,000 m3/ha, the amount of solid waste generated from pangasius farming is about 33.3 tons of sludge/ha (including mud and water)[4]. Meanwhile, resources for aquatic environ-mental protection activities (including finance and human resources) are still limited.
3. Potential GHG Emissions from Agricultural Activities in Dong Thap Province
3.1. GHG emissions due to agricultural activities in Dong Thap Province
In this report, CH4, CO2 and N2O was chosen to calculate the ability emissions in 2021 and 2022 in Dong Thap Province. The GHG emission coefficient is calculated according to the guidance of The Intergovernmental Panel on Climate Change (IPCC) (2006), domestic and foreign research relat-ed to the field of agriculture and agricultural waste.
3.1.1. GHG emissions in livestock farming
According to the guidance of IPCC (2006), based on num-ber of livestock, GHG emissions are calculated as follows:
Total C O2 emissions = Number of livestock x emission coef-ficient x conversion factor.
– CH4 emission coefficient from food digestion (intestinal fermentation) of Cow is 27 (kg/head), Pig is 1(kg/head) and Buffalo is 49(kg/head).
– CH4 emission coefficient from waste management pro-cess of Cow is 2.4 (kg/head), Pig is 7 (kg/head), Buffalo is 2.8 (kg/head), Poultry is 0.02 (kg/head).
– N2O emission coefficient from waste management pro-cess of Cow is 39.59 (kg/head), Pig is 13.49 (kg/head), Buffalo is 44.38 (kg/head), Poultry is 0.02 (kg/head).
3.1.2. GHG emissions in aquaculture
– Based on aquaculture area, GHG emissions are calculated as follows: CH4 emission coefficient from shrimp, fish is 0.63 kg CH4 /ha.day (Hiraishi et al.,2013), aquaculture time of about 210 days/year for shrimp and 240 days/year for fish. CO2 emission coefficient from shrimp, fish is 60.4 ± 1.45 kg CO2/ha/day (Nam., 2016)[6], aquacul-ture time of about 210 days/year for shrimp and 240 days/year for fish.
– Based on aquaculture production and N2O emission coefficient is 0.00169 kg N2O – N/kg seafood: total N2O emissions = aquaculture production x 0,00169 x 44/28.
3.1.3. GHG emissions in farming
Rice cultivation: Estimated CH4 content released into the environment from paddy fields as follows. GHG emissions due to fertilizer use:Report calculated for two main types: Urea fertilization and lime.
– Emission coefficient of lime is kg 0.12 kg CO2/kg lime (GL, 2006), average demand of lime 3,1kg/ha, thus CO2 emissions from using lime is 0.37 kg CO2/ha.
– According to research by Chojnacka et al. (2019), the CO2 emission coefficient of urea is 3.47 kg CO2eq/kg urea, average demand of urea 240kg/ha thus CO2 emissions from using urea is 832.8 kg CO2/ha.
* GHG emissions from pesticide: To calculate emissions from pesticides, it is necessary to estimate the amount of GHG emissions from agricultural pesticide production. Williams et al (2009) [1]used a linear regression method combined with an average energy value of types for pesticide pro-duction according to Green (1987), has calculated the global warming potential (100 years) is 0.069 kg CO2eq per MJ of pesticide energy. Total CO2 emissions from specific pesticides are as follows.
3.1.4. GHG emissions from agricultural waste
In currently, no research to calculate GHG emission from waste biomass from farm-ing as well as sludge from aquaculture. Therefore, emission coefficient of garden waste in the composition of domestic waste and wastewater (IPCC, 2006) was applied.
3.2. Synthesize and compare GHG emission calculation results
Note: GHG emissions are mainly from farming activities accounting for 73% to 77%, followed by agricultural waste generation activities, accounting for 16% to 20%, emissions from aquaculture are low and livestock farming has the lowest proportion.
4. Proposed Solutions
4.1. Solutions to reduce emissions in farming
4.1.1. For rice cultivation
– Applying the Alternate Wet and Dry paddy plant-ing technique (AWD): Paddy fields are watered inter-mittently except for the rooting and flowering stages to reduce the time of flooding, which will reduce CH4 emissions approximately 51% compared to the tradi-tional [9]. However, this solution requires quite a large investment cost for irrigation pumping systems and dikes; therefore, if the Government does not support, it will not be attractive to farmers
– Converting land from 2 to 3 paddy crops to 1 pad-dy crop and 1 vegetable crop: The conversion has con-tributed to reducing the GHG rate by 25% [9]. This is also a solution has been applied in some localities and has potential to be replicated because it brings higher economic efficiency than specialized rice cultivation. However, this solution requires specific planning on land, markets and investment costs to renovate irriga-tion systems and processing facilities.
– Reuse 100% of biomass waste from farm-ing activities: Limit burning of waste bio-mass and completely reuse them, such as composting from straw to fertilize plants and produce fuel from husk, waste from fruit trees is fermented to produce feed containing probiotics for livestock.
4.1.2. Solutions to reduce emissions in man-aging and using fertilizers and pesticides
Use fertilizers appropriately: There should be specific recommendations on using fertilizers for soil, should not fertilize too much urea, leading to high NOx con-centrations in the soil, that causing direct and indirect emissions of N2O, NOx, NH3and GHG effects; should use slow-release Nitrogen to reduce Nitrogen loss when fer-tilizing plants, while also helping to reduce GHG emissions into the environment. At the same time, people could use garden waste, sewage sludge and other organic waste from agriculture to compost, create organic fertilizer. According to the project “Sustainable paddy production and reduc-tion of GHG emissions AgResults”, using organic fertilizer in rice cultivation has helped cut 50% of GHG emissions into the environment.
Using biosafe pesticides, which are cur-rently encouraged, including herbal pesti-cides and microbial pesticides…
– Herbal pesticides: A type of pesticide that uses toxins which was extracted from plants or vegetable oils to inhibit and kill pests, such as: Neem tree juice (kill pests and aphids), solution from chili, garlic, ginger (kill pests and insects), Chrysanthe-mum tea (kill endothermic animal, insects and invertebrates), solution from nicotiana rustica (kills pests, butterfly pupae, aphids and mollusks such as slugs), millettia pachyloba drake (kill Taiwania circumdata, Empoasca sp., and mango hopper).
– Microbial pesticides: Active ingredients include microorganisms such as bacteria, viruses, fungi, algae or protozoa, which ex-crete fluids containing antibiotics, capable of eliminate pests. This bacterium secretes proteins that help repel insects to protect plants, especially potatoes and cabbage. Other types of microbial pesticides use the principle of competition for survival, bringing non-harmful microorganisms to plants and being natural enemies of harmful microor-ganisms to take over the habitat and repel micro-organ-isms from plants.
According to the results of the model “Rice cultiva-tion reduces GHG emissions”, the “1 right – 6 reduc-tion” technical process has reduced the number of pes-ticides used in paddy fields by 30%.
– Provide land management policies: It is necessary to advise people to manage well cropland, keep clear soil, avoid flooding, clean up plant and animal residues, and apply properly manure to limit decomposing Nitrogen into GHGs by bacteria.
Although many solutions to reduce GHG emissions in the agricultural field have been researched and pro-posed; However, the applicability and replication of each technology depends largely on the economic ef-ficiency that the technology can bring to farmers in addition to its environmental efficiency. Therefore, the Government needs to have supportive policies to con-tinue researching these solutions in each specific area to ensure that people continue to apply and replicate GHG emission reduction technologies in agriculture.
4.1.3. Maintain forest ecology
Tree planting activities will increase the ability to absorb CO2 and help exploit and use 100% of bio-mass from forests… so afforestation will be highly effective in reducing GHG emissions. Applying the calculation of GHG emissions according to IPCC (2006), the amount of CO2 will be reduced by about -544.60 thousand tons of CO2/year (2022).
4.2. Solutions to reduce emissions in live-stock farming
CH4 emissions from the rumen of cattle: There should be a program to provide nutritional cakes or other nutritional products to reduce the amount of methane produced from the digestive activities of cattle. According to Van Zijderveld et. al. (2011), digestive products couldconvert nitrate into NH3, reducing CH4 production in the cow’s rumen by up to 50%.
Model for utilizing by-products from live-stock farming:
– Model of utilizing livestock waste to pro-duce organic fertilizer and biogas as cooking fuel; treating livestock wastewater with a bio-gas tank not only reduces odors but also col-lects gas for cooking.
– Model of utilizing animal manure to raise earthworms: Cow manure, pig manure and fillers such as grass, straw, water hyacinth, potato plants, peanut stems… or dry leaves are used as a substrate for earthworm farming. Cinnamon is used to produce organic food, anaerobic decomposition creates biogas, and produces bioenergy.
Note: The efficiency of reducing GHG emissions is about 73,4%. When applying and maintaining afforestation, GHG emissions will be reduced to about 80%.
4.3. Solutions to reduce emissions in aquaculture
Pond wastewater treatment: Recirculating water in aquaculture to reduce eutrophication is a sustainable method to reduce environmental impact by both re-ducing wastewater discharge and helping to control disease. This solution contributes to reducing the eu-trophication rate compared to traditional farming by 43.66% – 47.13%[12]
Treatment of sludge from aquaculture ponds:
– Sludge from ponds is used to fertilize agricultur-al land. Currently, pond areas use settling ponds to re-move suspended solids in waste quite effectively; how-ever, it is necessary to have attention to the residue of dissolved nutrients in the waste source.
– Phosphorus recovery: Current trends show that phosphorus resource regeneration is mainly imple-mented to reduce operating costs. Nutrient recovery is recognized to help control fouling in the sludge pipe-line, improve sludge dewatering, reduce polymer con-sumption, treatment sludge volume, energy recovery. At the same time, with demanding high livestock farm-ing and lacking land area for sludge treatment can be solved thanks to Phosphorus recovery techniques.
– Nitrogen recovery: The main goal of Nitrogen re-covery (reactive Nitrogen recovery) is to shorten the ni-trogen cycle and convert Nitrogen in the waste stream into artificial fertilizer (precursor form). About 30% of the Nitrogen in the waste stream, representing 4% of the Nitrogen in the wastewater, can be recovered. Al-though Nitrogen recovery less than agricultural fertil-izer needs, but Nitrogen recovery can be part of a sus-tainable solution.
5. Conclusion
The report analyzed and evaluated the situation and trends of GHG emissions in each field of agricultural production and agricultural waste, thereby providing analysis and assessment of opportunities and challeng-es for reducing GHG emissions in Dong Thap Province. The potential to reduce GHG emissions in the ag-ricultural sector is huge. However, the biggest challenge comes from limited funding to invest in waste reduction technology; in addition to the awareness, conscious-ness, responsibility to protect the environment and re-duce GHG emissions of local people are still limited.
Specific measures to reduce GHG emissions for each type of agricultural production in Dong Thap Province are as follows: Review and issue technical guidance do-cuments on GHG inventory for departments and re-levant units to refer to before implementing contents on GHG emission mitigation in agriculture; Expand cooperation with strategic partners such as C40 Orga-nization, JICA, World Bank…. to seek funding sources; issue handbooks to guide actions to reduce GHGs in each production fields in agriculture.
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Author: Nguyen Van Phuoc, Ho Chi Minh City Union of Science and Technology Associations.
Author: Nguyen Tran Thu Hien, Ngo Thi Thu Hieu, Nguyen Thi Thu Hien, Ho Chi Minh City Association for Water and Environment
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