An Effective Biochar Application for Reducing Nitrogen Emissions from Buffalo Digestate Storage Tank

Abstract

Open manure storage contributes to the release of ammonia (NH3) into the atmosphere. Tank floating covers represent an effective technique to reduce NH3 emissions and biochar has been gain attention as a floating cover and as manure additive. Nevertheless, the mechanisms involved in the process still need to be elucidated since they are influenced by the biochar specific properties, application methods and dose. This work aims to study: (i) the biochar adsorption performances in an NH3 aqueous solution under conditions relevant to manure storage and (ii) the effect of different biochar application methods and dosage on NH3 emissions from buffalo digestate storage. The results show that a 43% reduction in NH3 emissions can be achieved by using biochar as a floating cover of 2 cm rather than as an additive. Moreover, the results show that the biochar produced at 550 °C acts as an adsorbent material for both NH4+ and NH3, by being adsorbed on the biochar surface in the form of NH4+ after H+ abstraction from the acid groups. A minimum cover height of 2 cm is required to give compactness and provide an additional resistance to the gas transfer, which is even more relevant than the adsorption in reducing NH3 emissions.

Keywords

• ammonia emissions
• floating cover
• manure management
• biochar application