Life cycle assessment of an alternative enzymatic-biological treatment for effluents from industrial processing of potatoes

Abstract

Enzymatic processes offer an option for the treatment of rich-starch effluents from the industrial processing of potatoes, which has been usually provided by means coagulation-flocculation units followed by settling, filtering or mechanical separation stages. Pre-treatment of these effluents with amylase enzymes increases the biodegradable-soluble COD fraction (bsCOD) by hydrolysis of starch and other complex molecules therein present. For this reason, it has been thought the coupling of an enzymatic pre-treatment with a combined biological process (anaerobic + aerobic) as an alternative treatment for these starchy liquid streams. This “enzymatic-biological” concept would allow valuable biogas for its own operational needs and to reduce relevant environmental impacts regarding to the typical physicochemical processes, such as elevated consumption of energy and chemicals, as well the production of hardly biodegradable sludge. The apparent environmental advantages claimed by the enzymatic-biological treatment concept (alternative scenario) have been elucidated through a comparative life cycle assessment (LCA) against a solely physicochemical-based treatment (baseline scenario). Inventory data for the enzymatic pre-treatment were obtained and fitted from lab-scale tests, whilst average operational data were assumed for the anaerobic and aerobic units, as well for the baseline scenario. Environmental benefits have been unfolded by evaluating three mid-point environmental categories prioritized in this study, namely, global power warming, eutrophication potential and non-renewable energy consumption. The LCA results suggest the possible replacement of the physicochemical-based approach to treat starchy streams by applying the alternative enzymatic-biological process proposed in this study.