Greenhouse gas emissions from open-type anaerobic wastewater treatment system in natural rubber processing factory

• Survey of greenhouse gas emissions in natural rubber factory was conducted.
• 94.4% of total COD was removed by the open-type wastewater treatment system.
• Methane and nitrous oxide were emitted as main greenhouse gas.
• Nitrous oxide was 65% of total emitted greenhouse gas.

We evaluated greenhouse gases (GHGs) emissions from an open-type anaerobic system (OAS) treating ribbed smoked sheets (RSS) wastewater in a processing factory. The emitted biogas comprised 57.7%–60.8% methane, 14.5%–31.5% carbon dioxide, 10.8%–24.7% nitrogen, and 329–423 ppm of nitrous oxide. In the OAS, the chemical oxygen demand (COD) degraded as the methane emission rate increased from influent to effluent. Finally, 94.4% of the total COD was removed. More than 90% of the removed COD converted to methane. Methane emitted from the bottom and the wall surface of the OAS. Methane-producing bacteria was detected by a cloning analysis of the 16S rRNA gene. The predominant species differed depending on the degradation characteristics of the RSS wastewater in the OAS. The emission rate of methane and nitrous oxide ranged between 2.58 and 8.85 NL/(m2 hr) and between 0.074 and 0.410 NL/(m2/hr), respectively. Moreover, 0.153 t-CO2eq of GHGs were emitted from 1 m3 of RSS wastewater treatment. Nitrous oxide accounted for 65% of the total GHGs emissions because of its high global warming potential. Therefore, both nitrous oxide and methane that emitted from the treatment of wastewater from a natural rubber processing factory must be considered as significant contributors to the GHGs.