Technologies to remove carbon dioxide from the atmosphere

The Virgin Earth Challenge is a prize of $25m for whoever can demonstrate to the judges' satisfaction a commercially viable design which results in the removal of anthropogenic, atmospheric greenhouse gases so as to contribute materially to the stability of Earth’s climate.

Among the 11 shortlisted organizations are:

• biochar (Biochar Solutions, Black Carbon and Full Circle Biochar)
• carbon capture, particularly from ambient air (Carbon Engineering, Kilimanjaro Energy and Climeworks)
• enhanced weathering (Smart Stones)

Above three technologies (biochar, carbon air capture and enhanced weathering) have great potential to help out with carbon dioxide removal (CDR) from the atmosphere. To combat global warming, further technologies should be considered, such as in Solar Radiation Management (SRM) and Arctic Methane Management (AMM).

How effective each technology is in one area is an important consideration; importantly, each such technologies can also have effects in further areas.

Further areas

Global warming is only one out of multiple areas where action is required; an example of another area is the hole in the ozone layer over Antarctica; effective action has already been taken in this area, but the growing hole in the ozone layer over the Arctic shows that further action is necessary.

A safe operating space for humanity is a landmark 2009 study that identifies nine essential areas where sustainability is stressed to the limits, in three cases beyond its limits.

The inner green shading represents the proposed safe operating space for nine planetary systems. The red wedges represent an estimate of the current position for each variable. The boundaries in three systems (rate of biodiversity loss, climate change and human interference with the nitrogen cycle), have already been exceeded. From: A safe operating space for humanity, Rockström et al, 2009.

Areas and applicable technologies

The table below shows these nine areas on the left, while technologies that could be helpful in the respective area feature on the right.

As said, each of technologies may be able to help out in multiple areas. As an example, by reducing carbon dioxide levels in the atmosphere, biochar and carbon air capture can also indirectly reduce carbon dioxide in oceans and thus help out with ocean acidification. Enhanced weathering could additionally reduce carbon dioxide in the oceans directly, thus presenting itself even more prominently as a proposal to achieve sustainability in this area.

Similarly, algae bags located in the mouth of a river could help out in multiple areas. They could produce biofuel and thus help reduce aviation emissions, while in the process catching fertilizer runoff, thus reducing emissions of nitrous oxide (the largest ozone-depleting substance emitted through human activities in a 2009 NOAA study) and also reducing depletion of oxygen in oceans.

Implementing the most effective policies

Policy support for such technologies is imperative. Just like some technologies can help out in several areas, some policies can cover multiple areas. As an example, a policy facilitating a shift to cleaner energy can both reduce greenhouse gases and aerosols such as soot and sulfur. Sulfur reflects sunlight back into space, so reducing sulfur emissions results in more global warming, but conversely global warming can be reduced by releasing sulfur over water at higher latitudes.

How many different policies would be needed to support such technologies? What are the best policy instruments to use?

Traditionally, government-funded subsidies and standards have been used to contain pollution, sometimes complemented with levies and refundable deposits; this can also work for chemical pollution. Standards have also proven to be effective in reducing the impact of CFCs on the ozone layer, while - as said - policies could at the same time also be effective in other areas, in this case reducing the impact of CFCs as greenhouse gases.

However, standards don't raise funding for support of such technologies, while taxpayer-funded subsidies make everyone pay for the pollution caused by some. Hybrid methods such as cap-and-trade and offsets are prone to corruption and fraud, which compromises their effectiveness. Local feebates are most effective in facilitating the necessary shifts in many areas.

Two sets of feebates

To facilitate the necessary shift away from fuel toward clean energy, local feebates are most effective. Fees on cargo and flights could fund carbon air capture, while fees on fuel could fund rebates on electricity produced in clean and safe ways. Fees could also be imposed on the engines, ovens, kilns, furnaces and stoves where fuel is burned, to fund rebates on clean alternatives, such as EV batteries and motors, solar cookers and electric appliances. Such feebates are pictured as yellow lines in the top half of the image below.

Support for biochar and olivine sand could be implemented through a second set of feebates, as pictured in the bottom half of the image below. Revenues from these feebates could also be used to support further technologies, as described in the paragraph below.

Further technologies should be considered for their effectiveness in specific areas, including:

• release of oxygen to help combat methane in the Arctic and to help combat loss of stratospheric ozone
• use of plastic sheets to capture methane
• use of radio waves to enhance methane decomposition
• diversion of water from rivers to avoid warm water flowing into the Arctic Ocean
• release of aerosols over water at higher latitudes
• surface & cloud brightening to reflect more sunlight back into space

Further reading:

Feebates
Biomass
Carbon Air Capture and Algae Bags
Enhanced weathering
Oxygenating the Arctic
Ozone hole recovery
Enhanced methane decomposition
Desalination
Vortex towers could vegetate deserts
Carbon-negative building
LEDs: When will we see the light?
Thermal expansion of the Earth's crust necessitates geo-engineering
Towards a Sustainable Economy
The way back to 280 ppm

The idea behind the "Biochar Economy" is to try to embed biochar production into as many processes as possible, as pictured on above image, from open source ecology.

In carbon-negative 'Biochar Economies', biochar is proposed to also act as a kind of local 'gold standard' for local currency supply.

Your comments are welcome!

Related posts by Sam Carana
Biochar
Fees on Livestock to fund Biochar
The way back to 280 ppm

Dutch Professor Olaf Schuiling has been working on rock grinding for many years. Remember the Virgin Earth Challenge, launched early 2007 with the promise to award $35 million to the best method to remove greenhouse gases? Schuiling said: Let's grind more rocks! Last thing Schuiling heard was that he was among the final ten contenders.

Schuiling's method is simple. Crush olivine rock to small pieces and it will bind with carbon dioxide. This process - called weathering - happens in nature but takes a long time. Crushing and grinding olivine rock will speed up the process and is therefore often called enhanced weathering. It works best in wet tropical countries, but can be done everywhere around the world.

Schuiling proposes to cover beaches, levees and railway tracks with the material, and proposes olivine to be added to building materials like pavement and concrete. It can also be added to soil and water. Adding olivine can fertilize the soil and improve its ability to retain water, and can work well in combination with biochar and other ways to increase organic carbon in the soil. When added to the sea, it can reduce acidification, and stimulate growth of diatoms and other forms of biomass in the sea.

This is a win-win solution, Schuiling says, as it helps grow more food, while combating global warming. To add another win, it can also produce drinking water that is healthier than rain water. Schuiling recommends cities to build olivine hills, to remove carbon dioxide from the air while filtering water.

Below is a video with more background, in Dutch with English subtitles.  Also have a look at this poster.

Concentration of carbon dioxide in the atmosphere reached 394.97 ppm at Mauna Loa in May — 41% above the 280ppm it had been for thousands of years before the Industrial Revolution started.

Given the dangers of global warming, carbon dioxide needs to get back to 280ppm. Emission cuts alone will not be able to accomplish this, so what more can be done?

Large drops in carbon dioxide have taken place in history, and are attributed to weathering, i.e. rocks breaking down and carbonates being deposited on ocean floors. However, it takes nature many, many years to do this. To make this happen at accelerated rates, carbon dioxide removal methods can be deployed that are typically referred to as mineral carbonation and accelerated weathering.

At first glance, one may suggest implementation of policies such as cap-and-trade or cap and capture to make those who put carbon into the atmosphere pay for its removal. More effective, though, is a combination of two types of feebates, working separately, yet complimentary, to get emissions cut 80% by 2020 and carbon dioxide on the way back to 280ppm.

Many carbon dioxide removal methods are energy-intensive. As long as the energy used is expensive and polluting, not much can be achieved. A rapid shift to clean energy is necessary, which is best facilitated through energy feebates as described in my previous post.

As the number of solar and wind facilities grows, large amounts of clean electricity will become available at off-peak hours, when there's little demand for electricity. This will make such electricity cheap, bringing down the cost of methods such as accelerated weathering, which can take place at off-peak hours. Such energy will also make carbon dioxide removal more effective, since the energy is clean to start with.

Energy feebates can best clean up energy, while other feebates can best raise revenue for carbon dioxide removal. Energy feebates can phase themselves out, completing the necessary shift to clean energy within a decade. Carbon dioxide removal will need to continue for much longer, so funding will need to be raised from other sources, such as sales of livestock products, nitrogen fertilizers and cement.

A range of methods to remove carbon dioxide would be eligible for funding. To be eligible for rebates, methods merely need to be safe and remove carbon dioxide. Methods could remove carbon dioxide from the atmosphere and/or from the oceans.

Rebates favor methods that also have commercial viability. In case of accelerated weathering, this will favor production of building materials, road pavement, etc. Such methods could include water desalination and pumping of water into deserts, in efforts to achieve more vegetation growth. Selling a forest where once was a desert could similarly attract rebates.

Some methods will be immediately viable, such as afforestation and biochar burial. It may take some time for methods such as accelerated weathering to become economically viable, but when they do, they can take over where afforestation has exhausted its potential to get carbon dioxide back to 280ppm.