Does knowledge for dirty technologies spill over to clean technologies? The answer to this question has implications for the ease with which one can switch from dirty to clean R&D. Directed technical change models assume that there are no spillovers and consequently, find that clean technology subsidies are needed alongside carbon pricing. We empirically measure knowledge spillovers using data on patent citations from 1976-2020. The vast majority of clean technologies do not directly cite dirty technologies but are indirectly connected. Geothermal energy, clean metals and, carbon capture and storage have higher, but still modest, references to dirty knowledge.
Jee, S.J. & Srivastav, S. (2021). 'Knowledge Spillovers between Clean and Dirty Technologies'. INET Oxford Working Paper No. 2021-22.