Life cycle environmental impacts of using food waste liquid fodder as an alternative for pig feeding in a conventional Cuban farm.

This work aimed to compare cleaner production alternatives for pig production in the Cuban context through the Life Cycle Assessment (LCA) approach emphasizing the utilization of food waste (FW) as a substitute for traditional grain-based pig feeding. A conventional waste management method (lagooning) was assessed, including more environmentally friendly approaches (use of anaerobic digestion (AD) process); including the substitution of a fraction of solid fodder with food waste liquid fodder (LF), obtained from food waste. The analysis was based on one porcine equivalent livestock unit. The environmental impact categories assessed were global warming, terrestrial ecotoxicity, human carcinogenic toxicity, freshwater ecotoxicity, terrestrial acidification, and freshwater eutrophication. The major environmental benefits for pig production were observed when the maximum capacity of pigs was considered. In addition, favorable environmental performance was achieved by considering the substitution of solid fodder by LF, the AD as a waste management process, and the valorization of the solid and liquid effluents. The avoided products-related activities were the main contributor to freshwater ecotoxicity, human carcinogenic toxicity, and terrestrial ecotoxicity impact categories (up to 71 %). The sensitivity analysis showed that the variation in LF composition (protein concentration) could have a remarkable impact in all impact categories. Climate change performed as the more sensible impact category, suggesting that greenhouse gas (GHG) emissions, such as CO2 and N2O, are important drivers to change the environmental impact and need more attention. This research demonstrates that the environmental profile of the process can be improved by applying a cleaner production approach (AD as a waste management alternative and LF substituting solid fodder).

Energetic, economic and environmental assessment for the anaerobic digestion of pretreated and codigested press mud.

This study investigates the feasibility of anaerobic digestion (AD) of press mud previously pretreated, using two methods: Liquid Hot Water (LHW) and Thermo-Alkaline (TA), from an economic, energetic and environmental point of view. Two scenarios, a sugar mill with and without distillery were studied, considering monodigestion and vinasse codigestion. The results have shown that the LHW and TA pretreatments are self-sufficient in terms of thermal requirements since they can recover heat from the biogas engine, but the maximum electric and thermal net energy (64 MWh d-1 and 95 MWh d-1, respectively) was obtained during co-digestion with vinasse. The results of the environmental Life Cycle Analysis (LCA) show that the alternatives improve the environmental profiles, in both scenarios. The endpoint impact category "Human health" had the highest contribution because of both: the burning of fossil fuel at refinery to supply the required electricity; and the production of Ca(OH)2 when vinasse was fed. The AD of pretreated press mud by LHW in CSTR reactors was the most viable for the scenario of a sugar mill without distillery, while the alternative co-digestion with the vinasse of the press mud without pretreatment was the most viable for the scenario of a sugar mill with distillery. This research shows that both the environmental and energetic profiles and the profitability of methane production can improve when the pretreatment and co-digestion of these wastes from the sugar - alcohol production process are considered.

Modeling the anaerobic digestion of cane-molasses vinasse: extension of the Anaerobic Digestion Model No. 1 (ADM1) with sulfate reduction for a very high strength and sulfate rich wastewater.

This research presents the modeling of the anaerobic digestion of cane-molasses vinasse, hereby extending the Anaerobic Digestion Model No. 1 with sulfate reduction for a very high strength and sulfate rich wastewater. Based on a sensitivity analysis, four parameters of the original ADM1 and all sulfate reduction parameters were calibrated. Although some deviations were observed between model predictions and experimental values, it was shown that sulfates, total aqueous sulfide, free sulfides, methane, carbon dioxide and sulfide in the gas phase, gas flow, propionic and acetic acids, chemical oxygen demand (COD), and pH were accurately predicted during model validation. The model showed high (±10%) to medium (10%-30%) accuracy predictions with a mean absolute relative error ranging from 1% to 26%, and was able to predict failure of methanogenesis and sulfidogenesis when the sulfate loading rate increased. Therefore, the kinetic parameters and the model structure proposed in this work can be considered as valid for the sulfate reduction process in the anaerobic digestion of cane-molasses vinasse when sulfate and organic loading rates range from 0.36 to 1.57 kg [Formula: see text]  m(-3) d(-1) and from 7.66 to 12 kg COD m(-3) d(-1), respectively.