Methodology for generating life cycle assessments (LCAs) using artificial intelligence to scale expert reasoning and modeling in alignment with ISO 14040 and ISO 14044 standards. The approach infills data gaps, flags inconsistencies, and provides a transparent chain of reasoning. Generative LCA improves accuracy, is designed to pass third-party audits, and includes safeguards against common generative AI limitations such as hallucinations with an auditable data lineage.