Biodegradability Testing of Transformer Insulating Liquids: Decoding the OECD 301 for the electrical industry

This work is founded on a significant and unusual database of biodegradability test results collected over the last decade for different transformer insulating liquids. It presents an extensive analysis of biodegradability testing of transformer insulating liquids using OECD 301 protocols, highlighting challenges with poorly water-soluble substances, test method comparisons (301 B vs. 301 F), effects of dispersants, variability in test results across different labs and batches, and the relevance of these tests in the electrical industry context where oil spills are rare, concluding with recommendations for future standard developments and harmonisation to improve environmental impact assessments and transformer technology sustainability.