Light-weighting
of passenger cars using high-strength steel or
aluminum is a common emissions mitigation strategy. We provide a first
estimate of the global impact of light-weighting by material substitution
on GHG emissions from passenger cars and the steel and aluminum industries
until 2050. We develop a dynamic stock model of the global car fleet
and combine it with a dynamic MFA of the associated steel, aluminum,
and energy supply industries. We propose four scenarios for substitution
of conventional steel with high-strength steel and aluminum at different
rates over the period 2010–2050. We show that light-weighting
of passenger cars can become a “gigaton solution”: Between
2010 and 2050, persistent light-weighting of passenger cars can, under
optimal conditions, lead to cumulative GHG emissions savings of 9–18
gigatons CO<sub>2</sub>-eq compared to development business-as-usual.
Annual savings can be up to 1 gigaton per year. After 2030, enhanced
material recycling can lead to further reductions: closed-loop metal
recycling in the automotive sector may reduce cumulative emissions
by another 4–6 gigatons CO<sub>2</sub>-eq. The effectiveness
of emissions mitigation by material substitution significantly depends
on how the recycling system evolves. At present, policies focusing
on tailpipe emissions and life cycle assessments of individual cars
do not consider this important effect
