For cookstove and biodigester carbon projects, the fraction of nonrenewable biomass (fNRB) is an essential variable that is inherently difficult to model. fNRB is central to the calculation of emission reductions and over-crediting risks can arise when fNRB is overestimated. Recent independent research has provided new subregional values for fNRB across Sub-Saharan Africa, which sheds new light on the risks related to this parameter — critical for calculating emission reductions.

In this resource, we outline the three major approaches available to project developers for calculating their fNRB estimate and the tools that Calyx Global uses — including the most recent literature and data — to independently cross-check these projects’ estimates. Finally, we outline a few scenarios in which a project-defined fNRB value may yield a risk of over-crediting.