Reduction of environmental impacts of caffeine extraction from guarana by using ultrasound assistance

Abstract

Extraction of caffeine from guarana seeds was studied, comparing conventional extraction (CE) and ultrasound-assisted extraction (UAE). Preliminary studies permitted the selection of operating conditions for kinetics studies of both processes (water solvent, 10:1mL/g liquid-solid ratio). UAE enabled strong enhancement of caffeine yields and process kinetics compared to CE at room temperature. At higher temperature (50 and 70°C), the advantage of UAE over CE was still clear for extraction kinetics, but not for maximal extraction yield. Performing Life Cycle Assessment of both processes permitted to highlight ultrasound assistance ability to reduce extraction duration (up to 4.9 times), energy consumption (up to 6.2 times) and environmental impacts (more than twice for some impact categories) compared to CE at the same studied temperature. Environmental impacts of CE and UAE processes were studied in more detail using three different functional units. It contributed to a better knowledge of extraction process of caffeine from guarana seeds and allowed selecting the operating conditions maximizing benefits provided by ultrasound assistance. The environmental gains of UAE over CE at maximal temperature were relatively small when targeting a caffeine extraction yield close to the maximal attainable (at this temperature), but increased strongly for lower target yields.