DAC's role in gigaton-scale carbon removal may be minimal

The United States’ capacity for carbon removal is likely to surpass the country’s gigaton scale 2050 goal, according to a report released today by the Lawrence Livermore National Laboratory.

What’s more, most of that removal can be accomplished without direct air capture — the buzzy tech deployed by the likes of Climeworks and Heirloom. DAC has attracted billions in federal funding and immense interest from Big Tech.

The technical potential for low-temperature adsorbent DAC and storage (like the system developed by Climeworks) is near 900 billion annual tons, the report found, but most of that capacity won’t be necessary if lower-cost, easier to implement pathways are prioritized.

For example, by 2050, cropland-soil management and forest-based solutions alone can remove nearly 100 million tons of carbon dioxide. 

And biomass carbon removal and storage combined with purpose-grown crops could account for 900 million tons per year in that time, without impacting cropland or food prices(though the total potential depends on how much available biomass is used for competing decarbonization efforts, such as for sustainable aviation fuel.)

The land hurdle

However, to get all the way to net zero by mid-century, removal technologies including DAC and geologic storage will eventually become necessary. LLNL’s county-level analysis identified several regions of the U.S. as most optimal for development.

The report found that with current technologies, the million ton per year facility requires around 250 megawatts of electricity, which means that the current electrical grid in the U.S. isn’t sufficient to power meaningful amounts of net carbon removal via DAC. Accordingly,— identifying the ideal geographies for new projects is primarily based on additional renewable deployment potential.

The report identifies 120 million hectares that could be developed for additional energy to support DAC. (That’s land that is additional to space already identified as necessary for grid decarbonization efforts.) Unfortunately, some of the best locations for DAC based on wind and solar potential don’t have geological storage potential, or access to a carbon dioxide transport pipeline. 

Accounting for those features reduces ideal development locations to around 33 million hectares that have potential; the report found that  West Texas, the upper and lower Rocky Mountains, and parts of the Midwest have the largest potential for billion-ton-scale DAC and storage deployment powered by renewable energy. 

(Regions including Appalachia and Alaska have high potential for natural gas-powered DAC with carbon capture, the report added.)

Other barriers

But even for the limited amount of DAC that’s likely to be required for U.S. removal goals, challenges persist. First, DAC will continue to be the most expensive removal option out of those analyzed, the report found, and its 2050 success and scale is therefore highly dependent on regulatory mechanisms and a maturing carbon-removal marketplace.

Then there’s the immediate need to develop “scientifically guided and rigorous standards” for monitoring, reporting, and verification across DAC technologies. Developers must understand their scope 1, 2, and 3 emissions when doing carbon accounting, LLNL said.

Finally, there’s the reality that using renewable energy to decarbonize the grid may take precedence over powering DAC. 

Generation and use of renewable electricity for DAC projects must therefore be “carefully considered from an additional standpoint to ensure that the electricity would not have otherwise been used to decarbonize a local electrical grid or other sectors of the economy,” the report concluded.