Ex-ante life cycle assessment of volatile fatty acid production from dairy wastewater

Abstract

The transition from wastewater treatment plants to wastewater resource recovery facilities has led to research into and development of various new processes. The production from wastewater of volatile fatty acids (VFAs), an intermediate product of anaerobic digestion, is one of these processes. The purpose of this study is to evaluate the environmental sustainability of VFA production from dairy wastewater, which is still in the laboratory research phase, and to investigate the discrepancies between lab-scale and conceptual full-scale life cycle assessment (LCA) results. In laboratory-scale LCA, electricity consumption for mixing and heating is the major contributor to all impact categories. The material usage and disposal of these materials also contribute significantly to the environmental impacts. Full-scale LCA results show that heating of the reactor and addition of NaOH during the operation stage are the main contributors. Scenario analysis is conducted for heating device efficiency and operating temperature. The recommendations are to use alternative chemicals to NaOH or to co-treat dairy wastewater with alkaline wastewater, using a heating device with a high efficiency, and to try experiments at lower temperatures. There are discrepancies between the LCA results based on laboratory data and upscale data, meaning that there is a further need for investigation of upscaling for LCA purposes.