Environmental implications of anaerobic digestion for manure management in dairy farms in Mexico: a life cycle perspective

Abstract

The environmental profile of milk production in Mexico was analysed for three manure management scenarios: fertilization (F), anaerobic digestion (AD) and enhanced anaerobic digestion (EAD). The study used the life cycle assessment (LCA) technique, considering a 'cradle-to-gate' approach. The assessment model was constructed using SimaPro LCA software, and the life cycle impact assessment was performed according to the ReCiPe method. Dairy farms with AD and EAD scenarios were found to exhibit, respectively, 12% and 27% less greenhouse gas emissions, 58% and 31% less terrestrial acidification, and 3% and 18% less freshwater eutrophication than the F scenario. A different trend was observed in the damage to resource availability indicator, as the F scenario presented 6% and 22% less damage than the EAD and AD scenarios, respectively. The magnitude of environmental damage from milk production in the three dairy manure management scenarios, using a general single score indicator, was 0.118, 0.107 and 0.081 Pt/L of milk for the F, AD and EAD scenarios, respectively. These results indicate that manure management systems with anaerobic digestion can improve the environmental profile of each litre of milk produced.

Anaerobic digestion of agro-industrial waste: Anaerobic lagoons in Latin America

“…Anaerobic lagoons have the lowest methane productivity as a manure management strategy; concerning these, completely-mixed digesters with temperature control can increase their productivity up to 11 times (Cantrell et al, 2008;Rivas-Garcia et al, 2015). Implementing these systems on dairy farms increases the total costs ( digester + generator + O&M) by about 485% compared to lagoon-based systems (Beddoes et al, 2007); however, in the short and medium-term, they bring considerable economic and environmental benefits, which can help promote alternative markets for the valorization of manure in dairy and pig production in Latin America.…”

“…In general, 812 348 m 3 d −1 of biogas are produced daily. Considering the low heating value of biogas and efficiency in electrical co-generation of 0.2 (for co-generation systems in Mexican anaerobic lagoons (Rivas-Garcia et al, 2015), there is a potential for electrical generation of 345.8 GWh y −1 . Apparently, this amount of energy is high; however, its distribution and use are complicated; Latin America Dairy and pig farms are decentralized, and due to their low biogas productivity, they do not generate the proper technical conditions to use biogas in electric generators, generally.…”

“…In LATAM, most AW management processes are not precisely WtE-AD since only 15% have an electric generator (approximately 36% of the total capital cost is associated with this equipment). 65% of the digesters installed for AW management are covered anaerobic lagoons (over 4,000 according to own results), of which 84% operate under the mono-digestion regime of livestock manure, with scarce temperature and agitation controls, leading to problems of methane inhibition, generally with yields ranging from 0.01-0.02 m 3 CH 4 m −3 dig d −1 (Rivas- Garcia et al, 2015).…”

Feasibility and Barriers for Anaerobic Digestion in Mexico City

“…The production of digestate is a source of income. The price of the bio-fertilizer was estimated by relating the N content to the average selling price per Mg of N-fertilizer in the urea and ammonium sulphate in Mexico; these prices were obtained from the Ministry of the Economy, at $1.55 USD/kg N (€1.38/kg) [63]. The gate fee is considered to be equal to the amount paid to the landfills, at €10/Mg MSW [64].…”

Wind tunnel study of ammonia transfer from a manure pit fitted with a dairy cattle slatted floor

“…[2][3][4][5] Hence, as from 2001, European Union's National Emission Ceiling (NEC) Directive imposed the maximum allowed NH 3 emission levels to be reached by each country member. Since then, many research studies have been developed with the attempt to test mitigation strategies in order to abate NH 3 emissions from production systems of the main livestock categories, including cattle barns.…”