Effects of Acacia Mearnsii Tannins on Greenhouse Gas Emissions from Cattle manure: A Anaerobic Digestion Study

Abstract

The objective of this work was to evaluate the effect of diets with different levels of Acacia mearnsii tannins (0, 0.5, 1.0 and 1.5% of dietary DM) in two distinct cattle genotype (Holstein and Nellore) on the greenhouse gas (GHG) emissions of cattle manure analyzed in anaerobic digestion. Batch type experimental digesters were used, located inside a climatic chamber (30 to 35ºC). The use of Acacia mearnsii extract up to 1.5% of the DM of the cattle diet did not promote changes in the efficiency of removal of nutrients from the manure, or in the production of biogas and its compounds (CH₄, CO₂ and N₂O). The speeds of CH₄ and CO₂ production were more accentuated for Holstein, which can be a positive factor for reducing Residence Time. Therefore, tannins can be used as additives to modify rumen fermentation, without having any effect on the anaerobic digestion process of cattle manure.