Effects of Two Manure Additives on Methane Emissions from Dairy Manure.

Liquid manure is a significant source of methane (CH), a greenhouse gas. Many livestock farms use manure additives for practical and agronomic purposes, but the effect on CH emissions is unknown. To address this gap, two lab studies were conducted, evaluating the CH produced from liquid dairy manure with Penergetic-g (12 mg/L, 42 mg/L, and 420 mg/L) or AgrimestMix (30.3 mL/L). In the first study, cellulose produced 378 mL CH/g volatile solids (VS) at 38 °C and there was no significant difference with Penergetic-g at 12 mg/L or 42 mg/L. At the same temperature, dairy manure produced 254 mL CH/g VS and was not significantly different from 42 mg/L Penergetic-g. In the second lab study, the dairy manure control produced 187 mL CH/g VS at 37 °C and 164 mL CH/g VS at 20 °C, and there was no significant difference with AgrimestMix (30.3 mL/L) or Penergetic-g (420 mg/L) at either temperature. Comparisons of manure composition before and after incubation indicated that the additives had no effect on pH or VS, and small and inconsistent effects on other constituents. Overall, neither additive affected CH production in the lab. The results suggest that farms using these additives are likely to have normal CH emissions from stored manure.