RESUMEN
Sustainability assessment using a life-cycle approach is indispensable to contemporary bioprocess development. This assessment is particularly important for early-stage bioprocess development. As early-stage investigations of bioprocesses involve the evaluation of their ecological and socioeconomic effects, they can be adjusted more effectively and improved towards sustainability, thereby reducing environmental risk and production costs. Early-stage sustainability assessment is an important precautionary practice and, despite limited data, a unique opportunity to determine the primary impacts of bioprocess development. To this end, a simple and robust method was applied based on the standardized life-cycle sustainability assessment methodology and commercially available datasets. In our study, we elaborated on the yeast-based citric acid production process with Yarrowia lipolytica assessing 11 different substrates in different process modes. The focus of our analysis comprised both cultivation and down-stream processing. According to our results, the repeated batch raw glycerol based bioprocess alternative showed the best environmental performance. The second- and third-best options were also glycerol-based. The least sustainable processes were those using molasses, chemically produced ethanol, and soy bean oil. The aggregated results of environmental, economic, and social impacts display waste frying oil as the best-ranked alternative. The bioprocess with sunflower oil in the batch mode ranked second. The least favorable alternatives were the chemically produced ethanol-, soy oil-, refined glycerol-, and molasses-based citric acid production processes. The scenario analysis demonstrated that the environmental impact of nutrients and wastewater treatment is negligible, but energy demand of cultivation and down-stream processing dominated the production process. However, without energy demand the omission of neutralizers almost halves the total impact, and neglecting pasteurization also considerably decreases the environmental impact.
RESUMEN
High Rate Algae Ponds (HRAPs) are a promising technology for the treatment of municipal wastewater in locations with sufficient space and solar radiation. Algae-based processes do not require aeration, and thus have the potential to be less energy-intensive than activated sludge processes. We used a combination of LCA and LCCA analysis to evaluate the sustainability of HRAP systems, using data from the construction and operation of two demonstration-scale systems in Almería and Cádiz, Spain. As a reference for comparison, we used data from an activated sludge-based Sequencing Batch Reactor (SBR) treatment system in operation in Leppersdorf, Germany, which has comparable removal rates for a similar inflow. We focused solely on the actual wastewater treatment aspect of these technologies, excluding sludge treatment from this analysis. Based on our analysis, the current HRAP technology is more energy-efficient than activated sludge-based SBRs and requires only 22% of its electricity consumption. In addition, HRAP is more advantageous both economically (0.18 /m3 versus 0.26 /m3) and environmentally, with both lower global warming and eutrophication potentials (146.27 vs. 458.27 × 10-3 kg CO2 equiv./m3; 126.14 vs. 158.01 × 10-6 kg PO4 equiv./m3). However, the Net Environmental Benefit of SBR was slightly more favorable than of HRAP because of the higher removal rate for nutrients of SBR.