Greenhouse Gas Emissions from a Full-Scale Vermifilter for Sewage Treatment: Effects of Seasonality and Sewage Parameters

Biological processes may generate CO2, CH4, and N2O. Few studies have evaluated the impact of vermifilters (VFs) on the generation of these gases. The objective of this study was to evaluate the GHG emissions of a full-scale VF used for sewage treatment, as well as the effects of seasonality and operational condition. The study monitored the influent and effluent of a VF in a rural area. Emissions fluxes were measured using the static chamber method in fall–winter and spring–summer. The results showed that in terms of annual per capita emissions (kgCO2eq/cap·y), VFs generated less GHGs than conventional and non-conventional wastewater treatment plants (WWTPs), with CO2, CH4, and N2O emissions ranging between 0.8 and 7.5 kg/cap·y, 0.1–0.5 kgCO2eq/cap·y, and 5.7–9.5 kgCO2eq/cap·y, respectively. Regarding the effects of seasonality, CO2 increased by 139% in spring–summer compared to fall–winter, while N2O increased by 139% in fall–winter compared to spring–summer. A positive correlation between influent COD concentrations and CO2 emissions (r = 0.7) was observed, whereas the influent carbon/nitrogen ratio (C/N) and N2O emissions (r = −0.6) presented a negative correlation. These results evidenced that seasonality and sewage characteristics influenced GHG emissions in a full-scale VF.