Life cycle assessment of milk production system in Brazil: Environmental impact reduction linked with anaerobic treatment of dairy manure

[Display omitted] •LCA of milk to quantifies the magnitude of impacts reduced by anaerobic digestion use.•Anaerobic digesters processing dairy manure produce fertilizer and clean energy.•Anaerobic digestion can help mitigate a large part of the GHG emission in Brazil.•Most of the impacts are related to the digestibility and amount of the feed supply.•With the use of anaerobic digestion climate change impact decrease by 21% and 27%. Earlier Life Cycle Assessment (LCA) analyses have shown that dairy manure treatment by anaerobic digestion reduces the environmental impacts; however, the magnitude of this reduction is currently unknown in Brazil. This paper aims to assess the environmental impacts of milk production farms (with and without anaerobic digester) in Brazil with LCA. Additionally, quantify the reduction of environmental impacts associated with the treatment of dairy manure through anaerobic digestion in three different product systems: (1) the Embrapa farm with anaerobic digestion (AD), (2) the Embrapa farm without anaerobic digestion (NAD1), and (3) the Colinas farm without anaerobic digestion (NAD2). The analysis was performed using software OpenLCA©️, assuming 1 kg of fat and protein-corrected milk as a functional unit. Our results show that anaerobic digestion (AD scenario) promotes biogas and digestate production, which besides providing clean energy and organic fertilizer productions, can help reduce on average 25 % and 38 % of the impacts on acidification, eutrophication, climate change, energy use, photochemical oxidation, and ozone depletion, compared to NAD1 and NAD2, respectively. Then, if Brazil applied anaerobic digester to treat animal manure and encourages biogas production, besides the extra clean energy production, a part of the actions to mitigate CO2 emission could be achieved.