56 Local Carbon Capture Elizabeth Bernhardt, Meghan Blumstein Technology Overview Carbon capture is the act of either trapping CO2 emitted from burning fossil fuels or other industrial processes to prevent it from reaching the atmosphere or collecting CO2 already in the atmosphere to prevent it from contributing to global warming. We propose a combination of nature-based and engineered methods of carbon capture, paired with permanent sequestration. Post-combustion Capture The MIT Central Utility Plant currently fires two 22 MW combustion turbine generators (CTGs) using natural gas which could be retrofitted with post-combustion capture equipment to separate CO2 from the exhaust stream. Post–combustion capture typically relies on a molecule – a liquid or a solid – to selectively bond with CO2 when exhaust gas is passed through it. Liquid sorbents, like amines, are commercially mature (TRL 9) and relatively inexpensive (USD $60/tCO2) (Global CCS Institute 2020). Solid sorbents are less mature (TRL 7) and more expensive (Global CCS Institute 2020). Any sorbent requires an energy input (usually heat) to break the bond with CO2 and separate out pure CO2, after which the CO2 (usually cooled to a liquid or highly pressurized) must be transported to a separate location for sequestration. For MIT, it is most feasible to transport the CO2 by truck, as pipeline infrastructure does not exist in the area and would potentially be infeasible to permit and build. MIT may consider trucking captured CO2 for geological storage to basaltic formations in the Connecticut River Valley approximately 100 miles from campus. Most of New England lacks the types of sedimentary rock formations typically used for CO2 storage (TRL 7-9), and storage in basaltic formations has a TRL of 3-5 (IEA 2023). However, CarbFix, in partnership with Climeworks, is a recent commercialization of geological storage in basalt formations. Alternatively, the CO2 could be sold to local businesses exploiting the natural ability of some rocks to absorb CO2 – known as mineralization. Some concrete companies like CarbonCure are using captured CO2 to theoretically improve the strength of their concrete. The full life cycle of technologies needed to capture, transport, and store CO2 from the CUP has been demonstrated pilot scale or beyond. One of the primary concerns with implementation is that the electrical and steam requirements of operating the capture and separations processes would limit the capacity of the CUP to supply heat and energy to campus. This could be mitigated by installing equipment to process a portion of the CUP’s exhaust after campus energy demand has been reduced by other means. Despite this challenge, post-combustion capture remains the most mature, engineered method of capturing CO2 emissions.
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