Ammonia Emission Assessment After Buffalo Manure And Digestate Application

Quite recently, considerable attention has been paid to the effect of anaerobic digestion on ammonia emissions from digestate spreading in the field, due to the growing interest in NH3 emission monitoring. Unfortunately, there are still some different studies finding about the effect of anaerobic digestion on ammonia emissions. Thus, more research into this topic is still necessary before obtaining a definitive answer to the increment or not in emission. For this purpose, this paper proposes comparison study between ammonia emissions from buffalo raw (Farmyard) manure and digestate on bare soil under Mediterranean climate, using the wind tunnel equipped with acid traps, to assess the ammonia emission fluxes. The sampling campaign, in three replicates, lasted each time, for 6 days to ensure that most of the ammonia has been emitted before the end of each campaign. The results obtained indicate that a diurnal correlation between emission and external temperature occurs, especially during the first days. Specifically for both fertilizers, ammonia volatilization increased with air temperature raising. Overall, the total digestate cumulative NH3 emission is 54% higher than raw manure emission. This is certainly due to the Total NH4+-N rate, which was 55,8kg ha-1 for the raw manure and 107 kg ha-1 for the digestate, around 1,9 times higher for the digestate TAN content. Finding suggests the need for adjusting digestate application rate based on TAN content, in order to reduce the impact on the environment.