Negative-emission Waste-to-Cement via Tandem Supercritical Water Oxidation and Hydrothermal Mineralization

Abstract

Cement production and municipal solid waste management contribute 16% of global CO2 emissions. Here, we describe Hydrothermal Oxidation and Mineralization (HTOM) as a new process for production of alternative construction material (ACM) with a compressive strength (9.230.98 MPa) more than double what is required for non-loadbearing concrete (4.14 MPa) while storing CO2. HTOM consists of two oxidative reactions: (1) supercritical water oxidation (SCWO) converts the organic fraction of food waste to a high-pressure CO2 stream while producing thermal bioenergy that can be recovered using a turbine, then (2) the high-pressure CO2 stream is used for rapid mineralization of soluble calcium to calcium carbonate, reaching 100% conversion within 20 minutes. ASPEN/HYSYS simulations and a GREET lifecycle analysis demonstrate that HTOM has the potential to offset 0.99 kg of CO2 per kg of ACM produced by simultaneously diverting fugitive landfill emissions, capturing waste energy, and offsetting traditionally CO2-intensive cement mortar production.