Several factors make the decarbonization of chemicals uniquely challenging. First, chemical processes predominantly rely on fossil fuels as a feedstock and energy source (Figure ). Second, demand for chemical commodities has historically grown with the gross domestic project (GDP), a trend that is expected to continue despite more aggressive levels of end-product recycling. For example, demand for primary chemicals (e.g., light olefins (ethylene, propylene), aromatics, methanol, and ammonia) is projected to increase 40-60% by 2050 from 2017 levels depending on the rates of plastic recycling (Figure ). Third, existing chemical manufacturing involves processes interconnected through mass and energy flows, complicating production method changes for a single product in isolation. For example, using ethane from natural gas in steam cracking instead of naphtha from petroleum increases ethylene yields at the expense of lower propylene and aromatics yields, which drives the need for new propylene and aromatics units, as observed in the U.S. over the last decade. Fourth, the most carbon-intensive chemical products are commodities with large manufacturing volumes and relatively small profit margins, disincentivizing innovation investments. For example, ethylene, the largest chemical precursor to plastics, has a global annual production of over 150 MT/year and a similar scale of commensurate CO2 emissions. Fifth, chemical processes are central to large economies (e.g., U.S., E.U., China), and regulators and policymakers have reluctantly proposed emission-reduction changes to manufacturing processes due to potentially negative economic impacts. Collectively, these factors mean that reducing the carbon footprint of the chemical industry requires a holistic and cross-disciplinary effort to overhaul the foundational principles underlying the production of chemical commodities and their interaction with economy-wide decarbonization efforts. . Chemicals demand projections are taken from the Reference Technology Scenario (RTS) and Clean Technology Scenario (CTS) in the Future of Petrochemicals report. As described elsewhere , RTS represents a baseline scenario informed by "existing and announced policies and established behavioral and exogenous considerations. The CTS scenario, in contrast, models additional constraints such as direct sectoral CO2 emissions to be reduced by 45% by 2050 vs. 2017 and other sustainability drivers such as increased plastic recycling.