'Turn off the taps before mopping the floor': Renewables more cost effective than direct air capture
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Direct air capture has been touted as ‘essential’ in meeting the EU’s climate goals – but is now really the time for investment?
The argument for pumping money into direct air capture (DAC) “weakens substantially” when it comes to renewable energy, according to a new analysis.
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DAC technologies, which use chemical reactions to pull carbon dioxide out of the air, have increasingly become part of the conversation on climate action.
Last year, the European Parliament’s think tank published a study arguing that a ‘diverse portfolio’ of CO2 removals, including DACs, is ‘essential’ to meet the EU’s 2050 climate-neutral goal and keep global warming within the 1.5 to 2°C limit.
“However, emission reductions need to be prioritised,” the paper reads. “If the global emission budget is exceeded initially, and removals are applied afterward, a decline in the temperature cannot be guaranteed.”
What is direct air capture?
DAC technologies come in many different forms, but most processes follow the same steps. First, ambient air is drawn into the system, where CO2 is isolated and separated through either a chemical or physical process.
This CO2 then leaves the system in its purest form, where it can be locked out of the atmosphere or reused.
Related“Captured CO2 can be injected deep underground for sequestration in certain geologic formations,” explains the World Resources Institute.
“It can also be used in products, though the amount of carbon dioxide stored and how long it stays there varies. Materials like concrete can sequester CO2 for centuries, while products like beverages or synthetic fuel quickly re-release carbon into the atmosphere.”
Direct air capture vs renewable energy
A new study published in the science journal Communications Sustainability, found that money spent deploying wind or solar delivers more combined climate and public health benefits than the same amount invested in DAC – even under “extremely optimistic assumptions”.
Researchers at PSE Healthy Energy in California modelled the advantages of cost-equivalent deployments of DAC, utility-scale solar, and onshore wind across 22 US grid regions from 2020 through 2050.
The team first tested a DAC scenario based on current commercial performance, where about 5,500 kilowatt-hours of energy is required to capture one American tonne of CO2 at a cost of $1,000 (around €851). They then tested an ambitious progress scenario in which DAC's energy use falls by more than two-thirds and its cost by half (1,500 kWh and $500 – €425 – per tonne).
Renewables still delivered more climate and health benefits per dollar nationally in both tests. Under today’s commercial performance, grid-connected DAC actually produced more greenhouse gases and air pollution damage through 2050 than it offset.
This is because if DAC is connected to a grid powered even in part by fossil fuels, building DAC will generate new sulfur dioxide, nitrogen oxides, and fine particulate matter concentrated in the communities near the power plants supplying that electricity.
Renewable deployment does the opposite, producing health benefits in every region and scenario modelled.
Scientists also modelled a ‘breakthrough’ (800 kWh and $100 – €85 – per tonne) at the extreme low end of published projections. Under this scenario, solar and wind continued to beat DAC across large portions of the country.
Ensuring climate mitigation has the most 'bang for the buck'
“There's a rapidly growing variety of interventions out there to mitigate greenhouse gases, and potentially affect public health as well,” says Dr Jonathan J. Buonocore, senior author and assistant professor of environmental health at Boston University School of Public Health.
“Our research here shows the power of cost-effectiveness analysis to ensure that capital invested in climate mitigation has the most 'bang for the buck' for the climate, while having the fewest side effects.”
The authors note that the analysis is not an argument against DAC technologies, which may still help decrease legacy atmospheric CO2 once ongoing emissions are largely abated.
“If your sink is overflowing, turn off the tap before you begin mopping the floor,” says Dr Yannai Kashtan, lead author and air quality scientist at PSE Healthy Energy.
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