Abstract
The development of new options to reduce ammonia (NH3) emissions during slurry manure storage is still required due to the shortcomings of the current technologies. This study aimed to identify to what extent untreated and acid-treated biochar (BC) and pure acids could reduce ammonia nitrogen (NH3-N) volatilization and increase nitrogen retention in slurry digestate. The NH3-N emissions were effectively reduced by H2SO4 and H3PO4 acids, untreated BC when applied mixed into the digestate and acidified BC treatments applied on the surface of the digestate. Acidification increased the specific surface area and number of O-containing surface functional groups of the BC and decreased the pH, alkalinity and the hydrophobic property. Compared to untreated BC, the ability of BC to reduce NH3-N emissions was greater when it was acidified with H2SO4 and applied to the digestate surface. The effect on digestate pH of acidified BC when applied mixed into the digestate was not different, except for H2O2, from that of the addition of the respective pure acid to digestate. The total N concentration in digestate was not significantly correlated with NH3-N emissions. These findings indicate that acidified BC could be an effective conditioner to reduce NH3-N emissions from slurry digestate storage.
Highlights
80–90% of global ammonia (NH3 ) emissions originate from agriculture [1], and 64% are associated with livestock production [2,3]
The aim of the present study was to investigate (i) the ability of hay BC to reduce NH3 N emissions from digestate, (ii) to what extent the suppression effect of NH3 -N emissions of BC can be enhanced through acidification, (iii) which method is more effective for the application of untreated and acidified BC, and (iv) whether untreated and acidified BC addition reduces total N (Ntot ), NH4 + -N and nitrate-nitrogen (NO3 − -N)
The NH3 -N emissions were significantly influenced by the digestate conditioner, time and BC application method (p < 0.001)
Summary
80–90% of global ammonia (NH3 ) emissions originate from agriculture [1], and 64% are associated with livestock production [2,3]. The major sources of NH3 emissions are livestock housing, manure storage [4] and application of manure to grassland or arable land [5]. NH3 emissions are linked to several global environmental problems such as acidification of soils [6], eutrophication in terrestrial and aquatic ecosystems [7] and the formation of particulate matter in the atmosphere [8]. Deposition of NH3 in soil, water and air can have repercussions for plant biodiversity and human and ecosystem health at both local and regional scales [9]
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