Influence of process parameters on the environmental impact of 2,3-butanediol production by fermentation

Abstract

Producing bio-based chemicals such as 2,3-butanediol using biological processes can play an important role in combatting global warming and addressing fossil oil depletion. To identify sustainable processes, this study sought to incorporate environmental considerations right from fermentation optimization at laboratory scale. As the literature review revealed discrepancies in Life Cycle Assessment of fermentation processes, the study began with a comprehensive Life Cycle Inventory for 2,3-butanediol fermentation. Five impact categories showed significant normalized values (in person.year): ionizing radiation human health (3.2.10−2), human toxicity cancer effects (7.10−3), freshwater ecotoxicity (2.6.10−3), ozone depletion (2.3.10−3), and human toxicity non-cancer effects (1.8.10−3). The main contributors to these impact categories (hotspots) were identified as: energy demand, carbon source, potassium hydroxide for pH adjustment, antifoam, and nitrogen source. The energy demand for heating was found to represent up to 45 % of the ionizing radiation human health impact. The study also examined the influence on fermentation performance and on environmental impact of: 1) oxygen supply rate in batch mode, and 2) sugar feeding rate in fed-batch mode. When the fermentation and separation steps were considered together, the fermentation conditions producing the highest 2,3-butanediol concentration (74.7 g.L−1) also resulted in the lowest impacts across all environmental impact categories.