Prospective Life Cycle Assessment Suggests Direct Reduced Iron Is the Most Sustainable Pathway to Net-Zero Steelmaking

Decarbonizing the steel industry is essential due to
its substantial
contribution to climate change. This study explores pathways to achieve
net-zero CO2eq emissions in the iron and steelmaking industry
while minimizing environmental burdens beyond climate change. We conducted
a comprehensive attributional life cycle assessment using the net-zero-CO2eq-emissions framework, incorporating both conventional and
prospective life cycle assessment methods, to evaluate various decarbonization
strategies within the United Kingdom. All value chains were constrained
to achieve net-zero CO2eq emissions. Our findings indicate
that, under a “current time” scenario, the natural gas-fired
direct reduced iron with electric arc furnace is the most favorable
option. This is mainly because hydrogen-based direct reduced iron
production relies on the UK’s current electricity grid, which
has a carbon intensity of 293.28 g CO2eq per kWh. As greenhouse
gas emissions decrease toward 2050 (approximately 70% for hydrogen-based
direct reduced iron), the choice between natural gas and hydrogen
will become increasingly region-specific. All net-zero-CO2eq steelmaking case studies perform similarly on human health indicators,
while the direct reduced iron with electric arc furnace options have
60–82% lower impacts on the ecosystem end point indicator than
the blast furnace basic oxygen furnace routes.