Whatever it Takes to Save the Planet? Central Banks and Unconventional Green Policy

We study the transmission mechanism of a Green QE, defined as a policy that tilts the central bank’s balance sheet toward green bonds, that is bonds issued by non-polluting firms. We merge a DSGE framework with an environmental model, in which CO2 emissions increase the stock of atmospheric carbon, which in turn decreases total factor productivity. Imperfect substitutability between green and brown bonds is a necessary condition for the effectiveness of Green QE. However, even under this assumption, the effect of Green QE in reducing emissions is negligible and in some cases close to nil.