Reducing material requirements while decarbonising the Spanish economy: from a green growth to a postgrowth paradigm

The transition to a low-carbon economy is expected to increase material requirements, as low-carbon technologies (LCTs) typically require more materials than fossil fuel-based energy systems. Here, we extend the MEDEAS-Spain Integrated Assessment Model (IAM) to improve the representation of material requirements, stocks, and flows. Key novelties are: (i) the use of sectoral material demand intensities for each economic sector, (ii) the consistent representation of material stocks and flows, (iii) for an exhaustive list of 43 mineral materials covered. We perform an impact analysis on the material requirements and associated environmental impacts (final energy consumption, greenhouse gas (GHG) emissions, and material footprint) of a baseline and three decarbonisation scenarios (reaching a 100% renewable electricity mix) to 2050. First, the PNIEC-LTDS scenario represents the national energy and climate plan (consistent with a green growth paradigm). Second, the CappedEcon scenario presents a final demand capped to its 2025 level (moderate demand-side measures). Third, the Sufficiency scenario is parametrised by downscaling monetary final demand across sectors to a level sufficient to provide decent living standards for the entire Spanish population; a novel approach within IAMs that aligns well with a postgrowth paradigm. The results show that the material requirements of LCTs deployment are substantial. For the PNIEC-LTDS scenario, LCTs are responsible for more than 30% of total cumulative (2025–2050) requirements for copper (36%), chromium (70%), cobalt (84%), graphite (81%), lithium (66%), and nickel (82%). The material footprint increases by 47% between 2025 and 2050 for the PNIEC-LTDS scenario. However, material requirements are mostly driven by final consumption for the rest of economic activities (74% of the cumulative material footprint for the PNIEC-LTDS scenario). In contrast, the Sufficiency scenario achieves a large reduction in GHG emissions (fossil-fuel emissions are reduced by 93% compared to 2025) and in material footprint compared to the other scenarios (and reduced by 55% compared to 2025). The robustness of the results is ensured through a range of uncertainty analyses. Our results therefore suggest that reducing the level of final demand (with sector-specific reductions), in line with the transition to a postgrowth paradigm, could be crucial to reconcile a rapid and large deployment of LCTs with a reduction in material footprint.