Mitigating Greenhouse Gas and Ammonia Emissions from Stored Slurry through the Addition of Brewing Sugar and a Biological Additive

Abstract

Livestock slurry stores are a key source of ammonia (NH 3 ) and greenhouse gas (GHG) emissions. This study evaluated the potential to reduce NH 3 , CO 2 , CH 4 and N 2 O emissions by adding effective microorganisms (EM) and brewing sugar to beef cattle slurry in a replicated small-scale (1 litre slurry volume) experiment. The effect of EM and brewing sugar was explored at two concentrations (5 v / w and 10% w / w respectively) and in two environments (cold and warm) over a period of 30 days slurry storage. Greenhouse gas emissions were measured by taking headspace samples from the closed vessels over a 1 hour period, whilst relative NH 3 loss was quantified at the same time by placing an acid trap within the closed headspace. Brewing sugar addition induced 'selfacidification' of the slurry, via lactic acid production and accumulation, resulting in a decrease in slurry pH from pH 7.8 to <4.5. This was effective in lowering average NH 3 loss in the cold and warm environments by 40% and 70%, respectively. Methane emissions were also reduced following the addition of brewing sugar, by up to 75%, resulting in a reduction in the cumulative total GHG (N 2 O + CH 4 + CO 2 ) emission (expressed as CO 2 equivalent; CO 2 e) of 34% and 85%, respectively. The total greenhouse gas emission (CO 2 e) during slurry storage was dominated by CH 4 , representing at least 59% of total CO 2 e emitted. Effective microorganisms had little impact on NH 3 and GHG emission, and are not deemed a useful mitigation strategy for these gases.

One-Time Acidification of Slurry: What Is the Most Effective Acid and Treatment Strategy?

“…Instead of adding acids to the slurry, the addition of easily degradable organic compounds such as sucrose, glucose, sugar beet residues, or brewing sugar can also be used, as the fermentation of these products contributes to the formation of organic acids, which in turn lead to a reduction in the pH value [34,35].…”