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Significance Statement
The Southeast Asia region such as Thailand, Indonesia and Malaysia with Vietnam has the highest production of natural rubber. The three main types of natural rubber products from this region are technically specified rubber, concentrated latex and ribbed smoke sheets which are produced from natural rubber latex later used in downstream rubber products industries.
High concentrations of organic matter and nitrogen compounds of wastewater are commonly found in production of 1 ton of natural rubber products due to its preservation and coagulation by large amount of ammonia and formic acid respectively. The commonly used open-type anaerobic-aerobic system in natural rubber processing factories of Southeast Asia region possesses various disadvantages such as need for large land areas, long hydraulic retention time, power consumption for aeration, large discharge amounts of excess sludge coupled with foul and greenhouse gas emissions.
In a recent article by Tanikawa et al. (2016) which was published in Journal of Cleaner Production evaluated emissions of greenhouse gases from an open-type anaerobic system treating ribbed smoked sheets wastewater from a natural rubber processing factory in institute of Vietnam.
The researchers conducted a survey twice in October and January at natural rubber processing factory at Rubber Research Institute of Vietnam (RRIV) with type product and capacity of ribbed smoked sheets and 1000 ton/year respectively. A compartment layout of open-type anaerobic system of 1-60 was used with ribbed smoked sheet wastewater flowing through.
Composition of emitted gases from compartments 28, 33, 56 during October survey from open-type anaerobic system comprised of 57.7% to 60.8% for methane, 14.5% to 31.5% for carbon dioxide, 10.8% to 24.7% for nitrogen and 329 to 423ppm to nitrous oxide. Methane emission rate conducted from October to January survey was in the range of 2.58NL/(m2hr) to 8.85NL/(m2hr). 94.4% of total COD was removed by open-type anaerobic system in 12 days hydraulic retention time with removal efficiency of COD in this case higher than other anaerobic treatment system treating wastewater from natural rubber processing. The two observed results show that greenhouse gas emitted from open-type anaerobic system also comprised of nitrous oxide from the nitrogen removal process.
Results from COD mass balance in the open-type anaerobic system showed a higher gas production rate visually confirmed near the wall surface of each compartment when compared to emission rate measured only at the bottom. Sludge was also seen to be attached to surface of the wall by coagulated rubber. This confirmed emission of methane not only from bottom but also wall surface of the open-type anaerobic system and almost all of the organic matter was well degraded anaerobically and converted to methane open-type anaerobic system.
Nitrous oxide emission rate ranged from 0.10NL/(m2hr) to 1.19NL/(m2hr). Concentration of nitrate and nitrite were found to be below 1.55mgN/L and 0.50mgN/L respectively. 18.1% of ammonia was removed in open-type anaerobic system and nitrous oxide emission factor was found to be much higher than direct emissions from wastewater applied by (IPCC, 2006) which was also similar to the emission factor for full scale biological nutrient removal wastewater treatment plants.
Emission rates from 1m3 of treated ribbed smoked sheets wastewater for methane, nitrous oxide and total greenhouse gases were calculated as 0.054 t-CO2eq/m3, 0.99 t-CO2eq/m3 and 0.153 t-CO2eq/m3 respectively. 1.53 t-CO2eq/t-product of greenhouse gas emissions from open-type anaerobic system was higher than greenhouse gases of emission from production of concentrated latex, technically specified rubber and ribbed smoked sheets.
Microbial community analysis indicated methane-producing bacteria mainly utilized hydrogen and carbon dioxide produced by hydrolysis, acidogenesis and acetogenesis of ribbed smoked sheets wastewater in each compartments. At influent, nitrous oxide was accounted approximately for 80% of total emitted greenhouse gases but at the effluent, 65% of nitrous oxide was accounted for open-type anaerobic system.
The research team noted nitrous oxide and methane emission from open-type wastewater systems in natural rubber processing factories must be considered as a major contributor to greenhouse gas effects.
Journal Reference
Daisuke Tanikawa1, Kazuaki Syutsubo2, Takahiro Watari3, Yuma Miyaoka3, Masashi Hatamoto3, Sou Iijima4, Masao Fukuda4, Ngoc Bich Nguyen5, Takashi Yamaguchi3 . Greenhouse gas emissions from open-type anaerobic wastewater treatment system in natural rubber processing factory. Journal of Cleaner Production, Volume 119, 2016, Pages 32–37.
[expand title=”Show Affiliations”]- National Institute of Technology, Kure College, Department of Civil and Environmental Engineering, 2-2-11, Aga-minami, Kure, 737-8506, Japan.
- National Institute for Environmental Studies, Center for Regional Environmental Research, 16-2, Onogawa, Tsukuba, 305-8506, Japan.
- Nagaoka University of Technology, Department of Civil and Environmental Engineering, 1603-1, Kamitomioka, Nagaoka, 940-2188, Japan.
- Nagaoka University of Technology, Department of Bioengineering, 1603-1, Kamitomioka, Nagaoka, 940-2188, Japan.
- Rubber Research Institute of Vietnam, International Rubber Research and Development Board, Km 42 Road 13, Ben Cat District, Binh Duong Province, 827211, Viet Nam.
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