Efficiency of different strategies for pig slurry bioacidification to reduce ammonia and greenhouse gas emissions during long term storage

Slurry bioacidification is a promising approach to reduce ammonia (NH₃) and greenhouse gas emissions (CH₄, CO₂) during manure storage. This study investigated the effectiveness of different bioacidification strategies by adding varying amounts of glucose, brown juice (a by-product of green protein biorefining), sulfuric acid, or a combination of these to pig slurry to maintain low pH over long-term storage to reduce emissions. Preacidification to pH 5.5 using sulfuric acid, as well as the addition of a high dose of brown juice (50 %), effectively reduced and maintained pH during 42 days of storage, significantly reducing NH₃ and CH₄ emissions. A combination of preacidification to pH 6.5 to decrease the pH initially together with the addition of 50 % of brown juice, which provides a large amount of C and lactic acid bacteria to promote self-acidification, was found to be a promising strategy to reduce NH₃ and CH₄ emissions. This strategy will enhance environmental sustainability by reducing the need for sulfuric acid and carbon substrates to mitigate gaseous emissions from long-term manure storage. Further field studies are needed before bioacidification can be recommended as an alternative to traditional acidification methods.