Negative carbon emissions refer to offsetting or removing more carbon dioxide from the atmosphere than what is being emitted. This requires two elements: a way to collect carbon, which is typically done by pulling CO₂ back out of the atmosphere, and a means for safe and permanent disposal. Fossil carbon is used mainly for its energy; however, it also injects 10 gigatons of carbon into the environment every year. Most of it is released into the atmosphere as CO₂.

The preindustrial atmosphere contained about 60 years of current emissions.

CO₂ is the largest and most persistent heat-trapping gas in the atmosphere, thus its atmospheric quantities are not sustainable. Human-produced CO₂ emissions can cause potentially catastrophic and irreversible damage to our earth systems. Some CO2 that is emitted into the atmosphere will be moved by natural forces and placed into the ocean, causing ocean acidification. Some of those CO₂ emissions will also be relocated into the biosphere as well. With this being said, about half of today's emissions will linger for hundreds of years. It will take tens of thousands of years, for the excess carbon to be removed from the mobile surface carbon pool made up of the atmosphere, ocean, and biosphere. Avoiding the most severe effects of climate change requires not only the reduction of the rate of emissions through rapid decarbonization (i.e., added renewable energy, end-to-end energy efficiencies, sustainable fuels, and point source carbon capture and storage), but also, the elimination of all net emissions. If the resulting stabilization of carbon occurs at too high a level, decades of carbon removal will become necessary. It is very likely that the world has entered such an overshoot trajectory. Negative emissions are necessary to balance out emissions that are difficult to avoid, such as those from airplanes and ships. They are also important as they can aid the process of returning to sustainable levels of carbon in the environment thus removing society from its current overshoot.

The impact of excessive greenhouse gas concentrations can be a tough concept to grasp as it is a seemingly invisible, ongoing phenomenon continuing over time. Computer models and simulations conducted by researchers assist in understanding the eventual outcomes of our behavior. These models show the potential for substantial, climatic changes in the near future. While these models are not perfect, there is general agreement that continued increases in CO₂ concentrations will have an overall 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 will also increase the cost of mitigating the damage. The longer the world waits, the more CO₂ will accumulate in the atmosphere due to the fact that the planet has significantly diminished its ability to naturally sequester CO₂.

Negative carbon emissions are necessary to stabilize CO₂ concentrations. This will offset the most difficult emissions to decarbonize. The amount of negative carbon emissions required will depend on society’s tolerance for damages resulting from climate change. In the long term, the carbon budget must be balanced.

350 parts per million (PPM) of CO₂ has been declared a sustainable threshold for carbon emissions. This threshold has since been surpassed with an emissions trajectory placing the world well beyond 450 PPM. This has been deemed as "safe" to limit the most severe effects. The current trajectory shows that Earth is on track to surpass 500 PPM (a continued growth in emissions by 2% has been observed for more than half a century. This would have the world breach 900 PPM before the century is over). Drawing down 100 PPM, requires at least 1500 gigatons of CO₂ disposal. This is more CO₂ than has been emitted in the 20th century.

The ocean acts like a “sponge,” soaking up about half of the CO₂ emissions that human activity

has put in the atmosphere. As a result, ocean acidification is another environmental problem

driven by excess carbon in the environment. Fortunately, as the atmospheric concentration is

reduced, the ocean will return most of the CO₂ that it has previously absorbed. Similarly, the

biosphere will eventually give back the excess carbon it stored as well. As a result, direct air capture can return the earth to a carbon state that is sustainable without the need for additional technologies for removing carbon from the oceans and biosphere. On the other hand, this will not happen without some sort of trade-off. For every ton of carbon released, direct air capture will have to remove one ton. Overall, if the CO₂ in the atmosphere is lowered, excess carbon will return from nearly all the reservoirs it has been stored in.

As the last resort for emitters to neutralize their carbon footprint, the availability of negative

carbon emissions removes the argument that nothing can be done or that there are no options to aid the health of the environment. 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 emissions released from fossil-based energy, another ton can be removed.

It has been argued that the availability of direct air capture could slow down mitigation responses. The opposing argument is more likely correct. Today, many emissions are very

difficult to mitigate. For example, aviation, heavy trucking, ocean shipping, cement, and steel industries seek out exceptions because they cannot deal with their emissions. Natural gas is accepted as a great bridge fuel because the world needs deployable electric power. Once air capture costs less than $100 per ton, there is no need to make exceptions. Nobody can hide behind the argument that mitigation for their sector is simply too expensive. Therefore, a push to low-cost, direct air capture would accelerate a trend to zero emissions and nobody would need to be grandfathered in.

The MechanicalTree™ represents a collection of nearly 30 years of research conducted by Klaus Lackner, his colleagues, and his students in collaboration with Carbon Collect Ltd. This research has led to a scalable solution to remove carbon dioxide from the atmosphere. It combines a columnar design and a ‘passive,’ low energy approach to Direct Air Capture. The tree-like figure is approximately 1.5 meters in diameter and extends to a height of around 10 meters when fully extended to capture CO₂. It will collapse intermittently to just under 3 meters for recovery and to process the captured CO₂. The passive technology substantially lowers the capture cost of CO₂, making direct air capture commercially feasible for the first time. Passive Direct Air capture is referred to as PDACTM. The MechanicalTree™ requires very little energy to operate considering its passive design. The tree is composed of a stack of disks containing a sorbent material. When fully loaded with CO₂, these disks drop into the base container where the CO₂ is released - and the process is repeated. A cluster of 12 MechanicalTrees™ sits on a plot roughly equivalent to two 40-foot shipping containers. The cluster extracts around one ton of carbon from the atmosphere per day.

MechanicalTree™ considers the substantial potential for commercial and industrial scale carbon farming. This indicates that the ideal scenario of attaining under $100 per ton of captured, atmospheric CO₂ has been released for large scale carbon removal. Essentially, the functions of carbon capture can now mimic nature. Similar to that of a tree, CO₂ can be captured passively through the reliance of wind speed. Carbon can also be absorbed without any mechanical assistance, additional power or energy. It can then be released without requiring a complex, intensive process which are typically found in active direct air capture systems. This technology is the only passive, direct air capture technology in the world as other technologies focus on more energy intensive and higher cost methods.

Planting natural trees is always a good idea, but that alone cannot reach the scale required for balancing the world’s carbon budget. Afforestation and reforestation are important and necessary actions to augment the overall health of an ecosystem. While these are essential practices, there is not enough available, arable land to plant enough trees without compromising agricultural land. Planting trees would of course be beneficial, however, that idea alone is not a feasible solution to address the current and growing level of excess atmospheric carbon dioxide. Furthermore, when trees biodegrade much of the carbon which is previously sequestered is re-released into the atmosphere. MechanicalTrees™ are at least a thousand times more effective in reducing atmospheric CO₂ than via biomass. This enables significant scaling advantages and a much smaller environmental footprint compared to other proposed methods.

There cannot be a direct comparison between a forest storing CO₂ and MechanicalTrees™ capturing CO₂ for storage and reuse. Forests provide vital resources for various habitats and ecosystems as well as materials, recreational benefits, and the ability to naturally capture CO₂. Where feasible, reforestation is highly desirable and not in direct competition with

MechanicalTree™ farms. These are complementary strategies for managing excess buildup of

CO₂ in the atmosphere.

Carbon Collect’s MechanicalTree™ is designed to capture approximately 80kg. per day of CO₂ that is then conditioned for reuse or storage. At this rate, around 29,000 kg. could be captured within one year. A range between 4.5 and 40.7 tons of CO₂ is removed per hectacre during the first 20 years of tree growth. Actual productivity could be lower depending on local conditions and operating strategy. This design basis translates to roughly 10,000 tons per hectare.

The MechanicalTree™ delivers with a much cleaner product when compared to that of flue gas capture. The composition in the MechanicalTree™ offtake is H₂O, N₂, and O₂. CO₂ captured

from flue gas contains a lot more – specifically, contaminants from particulates and dust –

including SO₂, N₂O, Hg and others, so the clean-up costs are higher.

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. In this respect, it slows the rate of emissions.

For instance, direct air capture permits the use of carbon dioxide in the synthesis of liquid hydrocarbon fuels, such as methanol. This ultimately allows fossil-based energy sources to stay in the ground. Commercialization endeavors that use captured CO₂ can play a crucial role in developing and scaling up this technology.

Most importantly, the introduction of synthetic fuels made from CO₂, H₂O, and renewable

energy, makes it possible to store and transport renewables to every corner of the energy

infrastructure. Liquid fuels can provide transportation and produce power when renewable

energy is not available. The configuration between supply and demand over hours, and possibly days, will do better with batteries and other short term storage devices. Levelling out seasonal and annual mismatches will work much more cost-effectively with chemical storage. Here, liquid hydrocarbon fuels stand out. Direct air capture can collaborate with renewable energy providers to take over the entire energy system. On the other hand, however, this does not take away the need for net negative emissions to balance out emissions that happened decades ago.

Put simply, society should strive to discontinue all point sources of greenhouse gas emissions. This is an ideal situation and will be hard to do in the first half of this century. In any event, point sources are about one third of the emissions problem and one cannot solve CO₂ emissions by addressing just one third of the problem.

One third of the problem may have a cheaper solution. Point source carbon capture, capturing carbon dioxide from a flue gas from a fossil fuel based centralized energy sources (i.e., coal, natural gas), provides the opportunity to capture CO₂ at up to 300 times higher concentration than in the atmosphere. Given the likelihood of fossil fuels remaining a main energy resource in this century, the advancement of applications that can capture and permanently store the carbon released in these processes is crucial. Nonetheless, point source capture is not enough anymore to limit the overshoot.

Direct air capture is advantageous in many ways, some of which include but are not limited to:

• Scale rapidly through modularity

• Compensate for mobile CO₂ emissions (which account for roughly half of all global emissions) as well as CO₂ which cannot be captured from point source emitters

• Reduce transportation costs and risks associated with moving CO₂ captured via CCS to areas for sequestration

• Ensure 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.

Direct air capture (DAC) and passive direct air capture (PDAC™) produce 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 captured CO₂:

1) Recycling

CO₂ Recycling uses removed carbon dioxide as a feed stock for a variety of processes. At lower concentrations, CO₂ can be used to invigorate biomass growth for agriculture in greenhouses or biofuels. It also can be used to make materials like plastics. At higher concentrations it can be used to carbonate beverages, enable enhanced oil recovery, and synthesize renewable liquid hydrocarbons such as ethanol for synthetic fuels.

2) Disposal

CO₂ Disposal assures the safe and permanent storage of CO₂ from ambient air. Sequestration through mineralizing rocks and ocean liming are some disposal methods.

Sequestering CO₂ in saline aquifers is a top priority given the following:

• The prevalence of assessed saline aquifers with the requisite geologic features for sequestration

• The substantial capacity of each saline aquifer to take huge volumes of CO₂

• The relatively low degree of difficulty for drilling and other subterranean requirements (onshore relatively shallow water wells)

Average wholesale price of industrial CO₂ in the US ranges from $100 - $200 per ton. Factors affecting price include volume and logistics where low volume equates to higher cost. Other factors are also considered in that cost equation, for example, transportation of CO₂. Delivering carbon dioxide to off-grid locations or those that require traveling a far distance can cause higher transport costs.

Commercial CO₂ may be delivered as compressed gas, usually in cylinders. It can also be delivered as refrigerated liquid for larger volume applications such as beverage carbonation. Both compression and refrigeration are required for transportation and storage, adding cost. These might be avoided with onsite PDAC™. There is a growing demand for ‘renewable CO₂.

Countries and industries all enforce different regimes which place wildly different values on sequestration of CO₂. Our expectation is that over the next few years regulatory carbon pricing will reach $100 per ton of CO₂ sequestered.

Some examples include:

• USA 45Q legislation – Sequestration: for each ton of CO₂ sequestered, the 45Q legislation offers a tax credit of $85 per ton; Enhanced Oil recovery (EOR): for each ton of CO₂ sequestered for EOR, the 45Q legislation offers a tax credit of $60 per ton

• USA California Low Carbon Fuel Standard: each ton of CO₂ used to make renewable fuels attracts a carbon credit of $180 per ton (this value fluctuates)

• USA Carbon tax legislative initiatives not yet in effect: A number of carbon tax legislation initiatives are in process including the so-called Baker-Schulz legislation which will mandate a $40 per ton tax on carbon emissions of oil companies when effected

• Europe ETS Offsets Market: In Europe, carbon offsets are tradable. The current value of 1 ton of carbon offset is approximately $30 per ton and expected to rise substantially in the short term.

• Emissions Fines. A number of governments, companies, and industries face fines due to their excess carbon emissions including:

• Ireland: EU applicable fines

• Eskom (South African Utility): Fines expected to exceed South Africa Rand 11.5bn (US $800m) due to excess emissions (link here)

• Transport industry: Automotive and shipping sectors are facing $ tens of billions of fines to address excess carbon emission (link here)

Industrial and Agricultural

CO₂ is widely used in industry (i.e., urea, carbonated beverages) and agriculture (i.e., algae, greenhouses). CO₂ captured from the atmosphere can be used as a renewable source of CO₂.

Sequestration of CO₂

Geologic sequestration is the process of injecting CO₂ into deep subsurface rock formations for long-term storage. Underground injection of CO₂ for purposes such as enhanced oil recovery (EOR) and enhanced gas recovery (EGR) is a long-standing practice. CO₂ injection specifically for geological sequestration involves different technical issues and potentially much larger volumes of CO₂ and larger scale projects than in the past.

In the US, sequestration of CO₂ requires a Class VI1 well to inject the carbon dioxide into deep rock formations

Class VI well requirements are designed to protect underground sources of drinking water (USDWs).

Requirements address:

• Siting

• Construction

• Operation

• Testing

• Monitoring

• Closure