Do clean technologies learn from their dirty counterparts? Using patents granted by USPTO from 1976 to 2020, we evaluate the “intellectual distance” between clean and dirty technologies. Our measure of intellectual distance is intuitively similar to “degrees of separation” where 1 indicates that a clean patent directly cites a prior dirty patent, and 2 indicates that there is an intermediary technology. We find that less than one-tenth of clean patents directly cite prior dirty art. Since citations are a proxy for learning, this implies that for the most part, leveraging dirty knowledge to pivot into clean sectors is not straightforward. However, there is a high degree of heterogeneity. Some clean technologies such as geothermal energy, carbon capture and storage, and offshore wind learn significantly from dirty technologies, due to shared knowhow related to drilling, pollution-control and operating out at sea. Our analysis identifies “clean adjacent sectors” that build upon dirty knowledge inputs, which could be plausible diversification options for dirty firms.
Jee, S.J. & Srivastav, S. (2021). 'Pivoting from Dirty to Clean: The Intellectual Distance between Clean and Dirty Technologies'. INET Oxford Working Paper No. 2021-22.