Producing biochemicals from renewable resources is a key driver for moving towards sustainable societies. Life cycle assessment (LCA) is a standardized tool to measure related progress by quantifying environmental sustainability performance of chemical products along their life cycles. We analysed LCA studies applied to commercialized commodity biochemicals produced through microbial fermentation. The few available studies show inconsistencies in coverage of environmental impacts and life cycle stages, with varying conclusions. Claims of better sustainability performance of biochemicals over fossil-based chemicals are often based on comparing global warming impacts, while ignoring other impacts from bio-feedstock production. To boost sustainable biochemicals, we recommend that LCA practitioners include the broader range of impact indicators and entire life cycles, follow standards and guidance, and address missing data. The biochemical industry should systematically use LCA to direct research, identify impact hotspots, and develop methods to estimate full-scale process performance. This will promote biotechnology as important contributor to solving existing sustainability challenges.