What are negative carbon emissions?
Negative carbon emissions are natural or man made processes capable of providing a permanent net-negative balance of atmospheric carbon dioxide (CO2). This requires two elements: a way to pull the CO2 back, and safe, permanent disposal.
Why do we need negative carbon emissions?
CO2 is the largest and most persistent heat-trapping gas and excess man made CO2 emissions can cause potentially catastrophic and irreversible damage to our earth systems. While natural forces will remove some of the CO2 that is emitted to the atmosphere, a large fraction of today’s emissions will linger for thousands of years. Therefore, avoiding the most severe effects of climate change requires not only the reduction of the rate of emissions through rapid decarbonization (ie. added renewable energy, end-to-end energy efficiencies, sustainable fuels, and point source carbon capture and storage), but the stabilization of all emissions below a dangerous threshold. The existence of negative carbon emissions permits stabilization through a carbon neutral balance for sources unable or unwilling to decarbonize. Furthermore, in the likely event that the atmospheric concentration exceeds safe thresholds, we will need a method to draw down concentrations.
Why the urgency for the development of negative carbon emissions technologies?
The impact of excessive greenhouse gas concentrations is not immediate. Therefore, computer models and simulations are used to try to understand the eventual outcome of our behaviors today. While these models are not perfect, there is general agreement among them all that continued increases in CO2 concentrations will have a general negative impact on the global quality of life. In other words, it could be too late for action by the time the scope of the damage is understood. Delayed action also increases the cost of mitigating the damage. The longer we wait, the more CO2 will remain in the atmosphere, due to the diminished effectiveness our planet has in its ability to naturally sequester it. The sooner the cost of one ton of CO2 sequestered via negative carbon emissions technologies is less than the cost of damage of one additional ton of CO2 emitted into the atmosphere, the lower the costs of mitigating the damage from climate change.
How many negative carbon emissions do we need?
In the short term, negative carbon emissions will be required to stabilize CO2 concentrations to offset the most difficult emissions to decarbonize. In the longer term, the amount of negative carbon emissions required ultimately depends on our tolerance for damages from climate change. A sustainable threshold of 350 parts per million (ppm) of CO2 in the atmosphere has been passed. The current emissions trajectory places us well beyond 450 ppm, which has been deemed as “safe” to limit the most severe effects. Drawing down 100 ppm, requires at least 1500 gigatonnes of CO2 disposal. As CO2 rates become drawn down, it should be noted that the ocean will give back roughly half of the anthropogenic carbon emissions, thus requiring roughly twice as much work. The ocean has been acting like a “sponge”, soaking up about ½ of the CO2 we have put in the atmosphere. As the atmospheric concentration is reduced, the ocean will actually “produce” the CO2 it had previously absorbed and deliver it back into the atmosphere.
What is direct air capture and why is it the focus of the Center on Negative Carbon Emissions?
Air capture or direct air capture (DAC) is the technological removal of carbon dioxide from ambient air.
CNCE focuses on removing carbon dioxide directly from the air because it treats the root cause of climate change as all carbon emissions end up in the air (not counting the CO2 that ends up in the ocean). Furthermore it provides an unambiguous metric: the amount of CO2 removed.
How does CNCE capture Carbon dioxide?
There are several different methods to capture carbon dioxide that involve pressure, temperature, or humidity. We are developing and improving a material that operates on a humidity swing to capture and release carbon dioxide. It consists of a sorbent (anionic exchange resin), made of quaternary ammonium ion embedded in polystyrene, that absorbs (adsorbs) carbon dioxide when it is dry and releases it when wet, as a CO2 – enriched stream of air of up to 5% or 50,000 parts per million.
There’s only 1 part Carbon dioxide for 2500 parts air. How can that be economically removed?
With humidity swing technology, paying for huge volume of air required becomes virtually free because we rely on normal wind to move the air for us. The concentration is a minor consideration in the overall process. While it is true that it is a little “harder” to remove small concentrations over large concentrations, the difference is insignificant given the increased efficiencies gained in other parts of the process. This is fundamentally different from how a normal filter might work for conventional carbon capture and storage technology. The same idea is used to economically and efficiently remove trace amounts of unwanted contaminants from water
Why not just plant trees?
Afforestation and reforestation are important and necessary actions to augment the overall health of an ecosystem. However, there is not enough arable land without compromising agricultural land on the planet to plant enough trees to address the excess carbon dioxide in the atmosphere. Furthermore when trees biodegrade some of the carbon which is previously sequestered is re-released into the atmosphere. Our technology is theoretically at least 1000 times more effective in reducing atmospheric CO2 than via biomass which permits significant scaling advantages and a much lower footprint than other proposed methods.
Would the availability of negative carbon emissions let emitters off the hook?
The availability of negative carbon emissions as the last resort for emitters to neutralize their footprint removes the argument that nothing can be done or that there are no options. Without the option to account for carbon neutrality there is no hook. Put another way, the tool to offset CO2 emissions permits the insistence that CO2 emissions can be held stable. The availability of this tool with proper policies will thus accelerate the transition to a carbon neutral economy and the development of more cost effective solutions.
What role does carbon recycling have in negative emissions?
While carbon recycling does not reduce the net amount of CO2 in the atmosphere, it works to close the carbon cycle in applications that would otherwise increase the atmospheric concentration, thus slowing the rate of emissions. For instance, the ability to capture carbon dioxide from air permits its use in the synthesis of liquid hydrocarbon fuels, such as methanol, ultimately allowing fossil based energy sources to stay in the ground. Commercialization endeavors that can use captured CO2 can play a crucial bootstrap in developing and scaling up this technology.
Why not just first capture Carbon dioxide from concentrated sources?
Carbon capture and storage (CCS), or capturing carbon dioxide from a flue gas from a fossil fuel based centralized energy sources (ie. coal, natural gas), provides the opportunity to capture the gas of up to 300 times as great of a concentration. Given the likelihood of fossil fuels to remain the main energy resource in this century, the advancement of applications that can capture and permanently store the carbon released in these processes is crucial. However, air capture holds several key advantages in addition to CCS, including the ability to:
- Scale rapidly through modularity
- Compensate for mobile CO2emissions (which account for roughly half of all global emissions) as well as the CO2 unable to be captured from point source emitters
- Reduce transportation costs and risks associated with moving CO2captured via CCS to areas for sequestration
- Insure against risk of fugitive emissions or failed carbon capture and storage plans
- Produce a source of carbon for recycling that comes from the air and does not add new fossil based carbon into the atmosphere.
Would the availability of negative carbon emissions let emitters off the hook?
The availability of negative carbon emissions as the last resort for emitters to neutralize their footprint removes the argument that nothing can be done or that there are no options. Without the option to account for carbon neutrality there is no hook. Put another way, the tool to offset CO2emissions permits the insistence that CO2 emissions can be held stable. The availability of this tool with proper policies will thus accelerate the transition to a carbon neutral economy and the development of more cost effective solutions.
How would the availability of negative emissions affect emitting sources?
The availability of negative carbon emissions fundamentally changes the nature of climate change mitigation because it creates a backstop against which emitting sources can become carbon neutral. Negative emissions can assure that for every ton of fossil based energy that comes out of the ground, another one can be put away. These negative emissions solutions thus become the most expensive carbon abatement technology and through the force of policy can encourage emitting sources to find cheaper ways to lower their carbon footprint.
What can be done with the Carbon dioxide once it is captured?
The humidity swing produces an enriched stream of CO2. This can be concentrated further or can be used as is, based on the type of application. Ultimately, there are two ways of dealing with the CO2 captured: recycling and disposal.
- CO2 Recycling uses the CO2 that is removed from air, as a feed stock for a variety of processes that might require 1-99% concentration. At lower concentrations, CO2 can be used to invigorate biomass growth for agriculture in greenhouses or bio-fuels. It also can be used to make materials like plastics. At higher concentrations it can be used to carbonate beverages, and enable enhanced oil recovery and synthesize renewable liquid hydrocarbons like methanol.
- CO2 Disposal assures the safe and permanent storage of CO2 from air. Sequestration by mineralizing rocks and, ocean liming are some of the disposal methods of CO2. Mineral sequestration involves converting CO2 into carbonates using rocks like Olivine and Serpentine. Ocean Liming involves adding lime to salt water which reacts with CO2 to form Calcium Carbonate.