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

Biological processes may generate CO 2 , CH 4, and N 2 O. 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 (kgCO 2 eq/cap·y), VFs generated less GHGs than conventional and non-conventional wastewater treatment plants (WWTPs), with CO 2 , CH 4 , and N 2 O emissions ranging between 0.8 and 7.5 kg/cap·y, 0.1–0.5 kgCO 2 eq/cap·y, and 5.7–9.5 kgCO 2 eq/cap·y, respectively. Regarding the effects of seasonality, CO 2 increased by 139% in spring–summer compared to fall–winter, while N 2 O increased by 139% in fall–winter compared to spring–summer. A positive correlation between influent COD concentrations and CO 2 emissions (r = 0.7) was observed, whereas the influent carbon/nitrogen ratio (C/N) and N 2 O emissions (r = −0.6) presented a negative correlation. These results evidenced that seasonality and sewage characteristics influenced GHG emissions in a full-scale VF.