Sustaera ($11M to capture CO2 from the air using monolithic substrate assembly and renewable electricity)

Sustaera, an American startup founded in 2021, develops direct air capture (DAC) technology to remove carbon dioxide (CO₂) directly from the air. Sustaera is a spin-out of Susteon, a climate tech company focused on hydrogen, carbon capture, and carbon utilization. Sustaera uses renewable electricity to quickly liberate captured CO₂ in the sorbents under a mild temperature via heating underneath conductive desorption materials that are coated on the channel walls of monolithic substrate, which significantly minimizes energy input compared to conventional DAC technologies. Sustaera's DAC system can capture 1,000+ tons/year of carbon dioxide, and the company was selected as one of the top 15 teams to receive a $1M Milestone Prize in the XPRIZE Carbon Removal competition.

Challenges: carbon emissions and Direct Air Capture

Carbon emissions

Since the early 1900s, carbon dioxide (CO₂) levels in the atmosphere have increased by 50% due to human activities. When fossil fuels (such as coal, oil, and natural gas) are burned for energy production, transportation, and industrial processes, CO₂ is released into the atmosphere. This excess CO₂ acts as a greenhouse gas, trapping heat and causing the air and ocean temperatures to rise. CO₂ emissions play a crucial role in driving climate change.

This warming effect has caused the global average temperature to rise by about 1.1 ºC since the pre-industrial period. This has led to rising in the frequency and intensity of extreme weather events, melting of polar ice caps and glaciers and rising sea levels, shifts in species ranges and increased risk of species extinction, agriculture and food security,  and ocean acidification.

To mitigate these impacts, the Paris Agreement aims to limit global warming to well below 2 ºC above pre-industrial levels. The Intergovernmental Panel on Climate Change (IPCC) estimates that a “carbon budget” of about 500 GtCO₂, which corresponds to about ten years at current emission rates, provides a 66% chance of limiting global warming to 1.5 ºC.

Direct Air Capture

Direct Air Capture (DAC) is a process that extracts CO₂ directly from the atmosphere, as opposed to industrial emissions with a high CO₂ content. The captured CO₂ can then be either permanently stored in deep geological formations, thereby achieving CO₂ removal (CDR), or used as a climate-neutral feedstock for a range of products that require a source of carbon.

The basic principle of DAC involves using large-scale machines or facilities equipped with specialized filters or sorbents which are designed to attract and bind with CO₂ molecules from the air while allowing other gasses, such as nitrogen and oxygen, to pass through. After the CO₂ is captured, it is separated from the sorbent through a regeneration process, resulting in the release of CO₂.

DAC technology employs a variety of methods, but chemical sorbents or solvents are typically used to capture CO₂. These sorbents can chemically react with CO₂ to form solid compounds or dissolve the CO₂ in a solvent. The captured CO₂ is then released from the sorbent or solvent via heating or other processes, allowing for its storage or utilization.

Direct air capture technology challenges

DAC plays an important and growing role in net-zero pathways. Capturing CO₂ directly from the air and permanently storing it removes the CO₂ from the atmosphere, providing a way to balance emissions that are difficult to avoid, including from long-distance transport and heavy industry. DAC has seen a surge in interest and investment over the past few years, and a growing number of companies are entering the market due to the realization that carbon removal will increasingly be needed to meet national and global climate goals, as well as the advantages of DAC relative to other carbon removal technologies.

However, this technology is still in its infancy and faces several challenges that are stunting its global adoption and deployment.

One of the main challenges is that CO₂ is present in the air at a much lower concentration than other commonly targeted sources, such as flue gasses resulting from energy generation and industrial processes. This makes it technically challenging and requires a lot of energy.

As carbon dioxide removal from ambient air is an energy-intensive process, DAC technology is more expensive per ton of CO₂ removed than many mitigation strategies and natural climate solutions. Today, the price range for DAC ranges between $250 and $600. By the end of this decade, however, the cost of DAC technology is projected to fall to $250-$300/mtCO₂e (million tons of CO₂ equivalent) for a multi-megaton capacity range. If further industrialization is accomplished within the ecosystem of this emerging industry, prices may fall to between $100 and $200/t.

The sociopolitical acceptance of DAC is also a challenge. Currently, there is no established market for carbon removal, and the demand for carbon removal is not yet sufficient to support the large-scale deployment of DAC. Some advocates worry the carbon capture process may not be scaled up fast enough to make an impact. However, the demand for carbon removal is expected to increase as more countries and companies set net-zero targets and seek to offset their emissions. In addition, governments and other stakeholders must provide substantial funding and support.

Sustaera Technology

Sustaera’s DAC technology removes CO₂ directly from the air using renewable electricity and  monolithic structured material assemblies. In a monolithic structured material assembly, a monolithic substrate with a honeycomb-like structure is positioned between two mesh electrodes. The monolithic substrate’s channel walls are coated with layers of conductive desorption, sorbent support, and sodium carbonate (Na₂CO₃) sorbent.

The Na₂CO₃ sorbent absorbs CO₂ from the airflow within the channels until they become saturated. To regenerate sorbent, the conductive desorption layer receives renewable electricity input via the mesh electrodes and in-situ heats the sorbent layer to quickly liberate CO₂ at temperatures below 120 ºC in a few minutes. In contrast to conventional DAC technologies, which require high temperatures to regenerate sorbents, Sustaera's technology minimizes energy input and reduces costs significantly.

Sustaera direct air capture technology

The diagram below depicts the system of the Sustaera DAC technology.

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