Microorganisms show promise for reducing emissions from manure

Microorganisms show promise for reducing emissions from manure Lisa Lock Scientific Editor Andrew Zinin Chief Editor Dairy farmers sometimes use additives in their cattle housing to reduce emissions from slurry. Emissions of substances such as ammonia occur when urine and feces mix on the floor of the housing. At the same time, dairy farmers want to increase the fertilizing value of the manure when it is applied to agricultural land. De Boer investigated whether the product Kopros B could fulfill both functions by testing whether the treatment changes certain properties of the manure. Kopros needs to be sprayed onto the housing floor periodically. The microorganisms are expected to multiply in the manure on the floor and subsequently continue to act in the slurry pit. Estimated ammonia reduction of almost a third Measurements of various manure properties indicated that applying Kopros could reduce both methane and nitrogen emissions. Based on these findings, the report showed that ammonia emissions from the cattle housing decreased by 30% or more during the study period. This percentage was derived from changes in manure composition and does not represent a directly measured reduction in emissions. One possible explanation for lower ammonia emissions is that the microorganisms used form a protective biofilm on the housing floor or on the surface of the slurry in the pit. A biofilm is a thin, slimy layer of microorganisms that attach themselves to a surface. Whether such a biofilm actually forms and has this effect remains to be investigated. Effects after manure application The higher pH and ammonium content following treatment with Kopros mean that the manure could produce higher emissions after being applied to agricultural land. However, the treated slurry is also less viscous, allowing it to infiltrate the soil more quickly and counteracting the effects of the higher pH and ammonium content. Further research is needed to determine the overall effect on ammonia emissions after manure application. How was the research conducted? For the study, a dairy cattle house with a slatted floor was divided into a treated and an untreated section. Each section had its own slurry pit. In the treated section, Kopros was applied to the slatted floor every four weeks. The cows in both sections received the same basic diet. From late September 2025 to mid-February 2026, manure samples were regularly collected from both pits. Which manure properties were measured? The study analyzed various properties, including pH, organic matter content, nitrogen, ammonium and volatile fatty acids. Ammonia emissions from the cattle housing were not measured directly. What were the results of these measurements in the cattle housing? The treatment altered several properties of the manure. The concentration of volatile fatty acids decreased by more than 60%. This substantial reduction is consistent with observations on farms that treated manure has a less pronounced odor. The treated manure also contained less organic matter. The pH increased, as did the concentrations of ammonium nitrogen and total nitrogen. The substantial decrease in volatile fatty acids, including acetic acid, may indicate lower methane production. Direct methane measurements are needed to confirm this. The nitrogen-to-phosphorus ratio in the treated manure was higher (after correction) than in the untreated manure. Phosphorus does not volatilize from manure. A higher nitrogen-to-phosphorus ratio therefore indicates that less nitrogen was lost through volatilization from the treated section of the cattle housing. What are the next steps? De Boer recommends testing the treatment under controlled and representative conditions, using an untreated control and direct measurements of ammonia and methane emissions. Further research is also needed into the possible formation of a biofilm, changes in the manure microbiome and the effects after manure application. More information H.C. de Boer, Effects of Kopros on ammonia emissions and nitrogen action of cattle manure, (2026). DOI: 10.18174/721447 Provided by Wageningen University