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Ammonia, methane, and nitrous oxide emission reduced by acidification of liquid manure


Stored livestock manure is a source of ammonia (NH3) and the greenhouse gasses methane (CH4) and nitrous oxide (N2O). One way to reduce these emissions may be to acidify the manure slurry. In an article recently published in Journal of Environmental Quality, researchers evaluate emissions from acidified (pH 5.2-5.5) and unacidified (pH 7.2) liquid dairy manure.

The authors report that reducing pH to below 6 by adding sulfuric acid can reduce the emission of NH3 by 62% during 47 days of storage and CH4 by 68% during 57 days of storage. These effects of acidification declined with time as pH gradually increased.

A large fraction of total carbon loss was as CO2, which must be accounted for when modeling transformation of organic matter and greenhouse gas emissions from manure stored in animal houses and outside. The loss of dissolved organic carbon (DOC) was closely related to the accumulated emission of C in CH4 and CO2, thus it is proposed that DOC can be used as a predictor of C emission.

Additionally, the researchers found the concentration of volatile fatty acids (VFA) and total ammoniacal nitrogen (TAN) was higher in surface layers than in the center of stored liquid manure, possibly due to organic matter floating to the surface, a process that will make modeling NH3 emissions complicated.

Read the full article in JEQ. Free preview June 7 - June 14