This study reviewed how ten recent roadmaps in the context of sustainability included learning effects. Specific measures were categorized according to (i) two kinds of scenarios, being a current policy scenario or a scenario aiming at improvements; (ii) seven types of changes, i.e. a demand in-/decrease, a demand-shift, an input decrease, an input-shift, an output decrease, a decrease in the upstream environmental impact of the inputs and a decrease in the downstream environmental impact of the outputs; (iii) two types of effects, being a direct and an indirect effect; (iv) three types of technologies, being mature technologies, emerging technologies, and new technologies; and (v) three types of estimations, being an expert estimate of a value, an expert estimate of a change and an extrapolation of historical data. In addition, five recommendations, based on an earlier review of learning effects in the scientific literature, were assessed for these ten roadmaps.
The results showed that where scientific publications often consider learning effects on the environmental or economic product level, the roadmaps focussed more on improvements in the technical component level. Historical data was only used by one roadmap. The transition towards renewable energy was included as an indirect event in the background by almost all roadmaps. However, the global warming impact of this future energy mix was assumed to be zero, which disregards the impact of material extraction and waste management required for renewable energy. It is therefore recommended to also incorporate the impact of the material footprint of the renewable energy transition when discussing future scenarios. All the included measures can be related to the circular economy strategies, although the targets of all roadmaps primarily focus on minimizing climate impact. This illustrates how circular economy strategies act as a means to an end, although this is not acknowledged by the roadmaps themselves. A roadmap with a circular economy as a target should therefore keep in mind that a circular economy is not a goal in itself but is a strategy to achieve a more sustainable society.