Monitoring of NH3 and CH4 emissions from dairy cows under storage conditions

Abstract

Cattle breeding is almost diffused around the world, with a growth of 7% in the last ten years. The increase in manure production makes cattle farms responsible for ammonia (NH3) and methane (CH4) emissions into the atmosphere. Many treatments have been adopted to reduce gaseous emissions, in order to comply with European regulations. Anaerobic digestion (AD) and solid-liquid separation (SLS) can modify the physical and chemical characteristics of manure, which are related to NH3 and CH4 emissions. The literature on the effect of the combination of both treatments on CH4 and NH3 emissions is still limited. Raw slurry (RS) and liquid fraction of digestate (LFD) were monitored during storage under controlled conditions, measuring NH3 and CH4 emissions with the dynamic chamber technique. The air sampled was analyzed using a gas-sensitive semiconductor and electrochemical sensors (Aeroqual, series 500). Results show that SLS and AD reduced the organic matter of manure, thus CH4 emissions during storage, which accounts for 27% less than RS. On the other hand, AD increased the NH3 emissions (48,5% more than RS) because of the higher Total Ammoniacal Nitrogen content of LFD. Only studying both gasses and considering the emissions in terms of CO2eq, it is possible to observe that RS is responsible for 11.4% of emissions in terms of CO2eq, more than LFD.