Microbial acclimation with whey reduces gaseous emission during slurry storage with positive effects on biogas production

DINUCCIO ELIO; SCARPECI TELMA ELEONORA; ROLLÈ LUCA; GIOELLI FABRIZZIO

Online

Congreso; LVI SAIB Meeting XV SAMIGE Meeting; 2020

SAIB-SAMIGE

Livestock manure is the main source of ammonia (NH3) emissions and an important source of greenhouse gases (GHG) carbon dioxide, methane, and nitrous oxide. These gaseous emissions can be reduced by acidifying the manure. Inorganic acids could be used to lower the pH but have several drawbacks, such as the subsequent biogas production inhibition. On the other hand, easily fermentable biomass such as whey has the ability to lower the pH of a suspension and to stimulate the activity of endogenous anaerobic microorganisms to produce organic acids. The Biogas Wipptal plant (LIFE12 ENV/IT/000671 OPTIMAL - OPTImised nutrients Management from Livestock production in Alto Adige) treats livestock waste of 75 dairy farms in the Italian Alto Adige region, generating biogas and organic fertilizers. Some of these establishments also generate a large amount of whey during cheese making, which is not being used for biogas production. The aim of this work was to assess the effect of whey acidification of raw cattle slurry on NH3 and GHG emissions during storage, and the performance of anaerobic co-digestion of acidified slurry with whey. A series of preliminary tests were conducted to determine an optimal dose of whey to be applied to dairy cattle slurry to achieve a target pH of 5.5. Two trials were subsequently performed to assess GHG and NH3 emissions during acidified slurry storage. In AS1-100 trial, whey was added in one dose at the beginning of the experiment and in AS1-10 trial a 10% of the same amount of whey was added daily for 10 days. In relation to non-acidified slurry (AS1-0), the emissions from AS1-100 trial dropped 83% for NH3 and 33% for GHG, and in the case of AS1-10 trial, the decrease of gases emitted were 86% and 54% for NH3 and GHG, respectively. A drop in the total GHG emissions observed in acidified slurries during the storage phase were mainly due to the lower CH4 loss followed by CO2 and N2O emissions. Batch-type anaerobic co-digestion of whey and acidified slurries resulted in a significant increase in methane production of 33% (AS1-100) and 53% (AS1-10) compared to the co-digestion of whey with AS1-0. These results indicate that the performance of biogas production improved when acidified slurries were used. This fact could be due to the acclimation of microorganisms present in the slurry to whey during the storage phase. In conclusion, there is a synergistic effect of mixing manure and whey in reducing the emission of GHG and NH3 during storage and, on the other hand, in anaerobic co-digestion of this mix for biogas production. Adoption of these results by dairy farms and cheese factories could solve the economic and environmental problems of GHG and NH3 emissions during manure storage, and treatment and disposal of whey generated as cheese byproduct, increasing at the same time energy and environmental sustainability of these establishments.