Response Curves for Ammonia and Methane Emissions From Stored Liquid Manure Receiving Low Rates of Sulfuric Acid
Vera Sokolov, Jemaneh Habtewold, Andrew VanderZaag, Kari E. Dunfield, E. G. Gregorich, Claudia Wagner‐Riddle, Jason J. Venkiteswaran, Robert J. Gordon
Abstract
Addition of sulfuric acid (H 2 SO 4 ) to liquid dairy manure (slurry) reduces methane (CH 4 ), nitrous oxide (N 2 O), and ammonia (NH 3 ) emissions. There is interest in understanding how gaseous emissions respond to decreasing rates of acidification, to determine economically optimum application rates. Acidification rates were tested ranging from 0 to 2 g sulfuric acid (H 2 SO 4 ) L −1 slurry in six meso-scale outdoor storage tanks, each filled with 10.6 m 3 slurry and stored for 114 d. Results showed that the rate of acidification for maximum inhibition of CH 4 and NH 3 emissions varied markedly, whereas N 2 O reductions were modest. Reductions of CH 4 increased with acid rate from 0 to 1.2 g L −1 , with no additional response beyond >1.2 g L −1 . In contrast to CH 4 , inhibitions of NH 3 showed a linear response across all rates, although reductions were ≤ 30%. Thus, higher acidification rates would be required to achieve greater NH 3 emission reductions. Our findings indicate that achieving >85% NH 3 emissions reductions would require 4 × more acid than achieving >85% CH 4 reductions. Decisions on optimum H 2 SO 4 rates will depend on the need to mitigate CH 4 emissions (the primary greenhouse gas emitted from stored liquid manure) or reduce NH 3 emissions (which is regulated in some regions). These results will help develop guidelines related to the potential costs and benefits of reducing emissions through acidification.