There was an avalanche of net-zero commitments in 2020, most of them targeting a “zero-carbon economy” by 2050. While progress has been made in renewable energy and electric passenger vehicles, other sectors—including industry, heavy transportation, and agriculture—that are major sources of emissions have not yet developed cost-competitive low-carbon technologies. Analysis by the International Energy Agency found that 75% of the emissions reductions necessary to achieve net-zero scenarios depend on technologies that have not yet reached commercial maturity. Where are the technology gaps? What is required to fill them? Can the economics work without a substantial price on carbon? Is hydrogen a silver bullet?