Abstract
Acidification of slurry is a common practice to reduce ammonia and methane emissions. Sulfuric acid is usually used for this process. However, this has been criticized due to the high sulfur input into soils. Therefore, the objective of this study is to show the effectiveness of a one-time acidification with alternative acids also in combination with other treatment strategies. The amount of acid as well as the change of pH value during storage were investigated. For most variants, a strong pH increase occurred within the first ten days after acidification. Mineral acids (sulfuric or hydrochloric acid) resulted in a lower pH increase compared to organic acids (lactic, acetic, and citric acid). Under anaerobic storage conditions, the pH remained significantly lower. The addition of glucose before acidification resulted in lower pH values during the first week, but in the long term, the conversion of glucose to carbonate led to higher pH values. A previous separation process was able to reduce the amount of acid. Although the pH increase was not that strong in the first days after acidification, it was much faster and stronger afterwards due to the lower buffer capacity in the separated slurry. A long-term pH reduction was achieved by acidification to pH 3.0, but this was associated with an increased amount of acid. On the basis of the results, a combination of organic acids with anaerobic storage can be recommended as an alternative to sulfuric acid.
Highlights
The agricultural sector contributes to gaseous emissions [1,2,3]
These can be reduced by acidification, solid–liquid separation, or dilution of the slurry, whereas covering may even increase methane emissions [5]
The aim of this study is to investigate the long-term stability of the pH value in slurry after a one-time acidification with different organic and mineral acids
Summary
The agricultural sector contributes to gaseous emissions [1,2,3]. Methane (CH4) is a harmful gas that substantially affects climate change and has a global warming potential 25 times higher than carbon dioxide [4]. The storage of slurry leads to methane emissions from livestock production [5,6]. These can be reduced by acidification, solid–liquid separation, or dilution of the slurry, whereas covering may even increase methane emissions [5]. Ammonia (NH3) is a major problem in slurry management due to its impact on the environment such as eutrophication, soil acidification, and the release of fine particulate aerosols or nitrous oxide emissions [7,8,9]. Ammonia emissions may occur in barns, when stored, or during the land application of slurry [10]. There are various techniques for reducing ammonia emissions such as covering or acidification [2,5]
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