Combination of H2SO4-acidification and temperature-decrease for eco-friendly storage of pig slurry

Abstract

Owing to the economic benefit and efficiency, H2SO4-acidification is often applied for reducing CH4 emissions during storage of pig slurry (PS). However, it encounters with several problems related with safety and the concomitant H2S emissions. To reduce the required amount of H2SO4, in this study, the storage at low temperature (20−35 °C) was applied to the mild-acidified PS (pH 6.5 and 7.0). 55.1 kg CO2 eq./ton PS of CH4 was emitted from the control (non-acidified at 35 °C), which was reduced to 14.4–40.2 kg CO2 eq./ton PS at 20−30 °C. Temperature-decrease led to the increase of the abundance of methanogens (Methanobrevibacter and Methanolobus) that can grow at low temperature and the drop of specific methanogenic activity value. To achieve 70 % CH4 reduction, 1.6 kg H2SO4/ton PS was needed in PS acidification, which was decreased to 0.5 kg H2SO4/ton PS by decreasing temperature from 35 °C to 25 °C. CH4 production potential of the PS stored at 35 °C-pH 6.5 and 25 °C-pH 7.0 was increased by 21–33 % compared to the control. The GHG reduction of 33.6–41.9 kg CO2 eq./ton PS and the profit of 6.6 USD/ton PS could be attained by applying acidification or combined storage, indicating that the temperature-decrease can be effectively combined with H2SO4-acidification.