Global Warming Action Plan

All nations should commit to effective action to deal with climate change. Nations should each be able to decide for themselves how to do this, provided they each meet agreed targets independently and genuinely (i.e. without buying or fabricating offsets or credits, domestically or abroad). Where necessary, border adjustments can help ensure that commitments are indeed met. Some policies may aim to reduce emissions in one area, while causing emissions elsewhere. As an example, biofuel may reduce emissions of carbon dioxide (CO₂) in transport, while increasing agricultural emissions, reducing forests and diverting crop, water and energy from better use. It is important for nations to each achieve results on each of the following points, without achievements in one area being counterproductive elsewhere. It is therefore recommended to take an approach that seeks results on each of the following points.

  Part 1. Reduce oceanic and atmospheric CO₂

Target: Ensure that atmospheric CO₂ levels do not exceed 400 ppm over the next few decades, while aiming for a longer term target of 350 ppm. James Hansen, NASA's top climate scientist, says in Target CO₂: Where Should Humanity Aim? that atmospheric CO₂ should be reduced to 350 ppm. To achieve this target, several policies will need to work in parallel with each other. 

  1.1. Dramatic cuts in CO₂ emissions In many cases, dramatic cuts in CO₂ emissions can be achieved merely by electrifying transport and shifting to generation of energy by clean facilities such as solar panels and wind turbines. Each nation should aim to reduce their CO₂ emissions by a minimum of 8% per year over the next ten years, based on their 2009 emissions, and by 80% by 2020. 

  1.2. Carbon must also be actively removed from the atmosphere and the oceans A study at the University of Calgary concludes that, even if we completely stopped using fossil fuels and put no more CO₂ in the atmosphere, the West Antarctic ice sheet will still eventually collapse (by the year 3000), causing a global sea level rise of at least four meters. This means that - apart from reducing emissions - there should be additional efforts to remove CO₂ from the atmosphere and the oceans, in order to get CO₂ down to levels as pictured on the above graph. Carbon is naturally removed from the atmosphere and the oceans by vegetation, so it makes sense to protect forests and encourage their growth. There are ways to reduce ocean acidification, such as by adding lime to seawater, as discussed at other posts of this geoengineering blog and at this geoengineering group. Carbon capture from ambient air and pyrolysis of surplus biomass with biochar burial are some of the most promising methods to further remove carbon from the atmosphere. Biochar can also help with afforestation and prevent deforestation and land degradation. Funding of carbon air capture could be raised through fees on jet fuel. All nations should commit to such initiatives — care should be taken that emission reductions are not substituted by carbon removal or vice versa. 

  Part 2. Short-term action 

The Arctic sea ice acts as a giant mirror, reflecting sunlight back into space and thus keeping Earth relatively cool, as discussed in this open letter. If this sunlight instead gets absorbed at higher latitudes, then feedback effects will take place that result in much higher temperatures, in a process sometimes referred to as Arctic amplification of global warming. The IPCC didn't take such feedback into account in AR4. A study that used 2007/2008 data as starting point predicts a nearly sea ice free Arctic in September by the year 2037, some predict an even quicker demise. A study by by National Center for Atmospheric Research (NCAR) scientist Jeffrey Kiehl found that carbon dioxide may have at least twice the effect on global temperatures than currently projected by computer models of global climate. Melting of ice sheets, for example, leads to additional heating because exposed dark surfaces of land or water absorb more heat than ice sheets. Albedo change is only one of a number of feedback processes. A rapid rise of Arctic temperatures could lead to wildfires and the release of huge amounts of carbon dioxide and methane that are now stored in peat, permafrost and clathrates, which constitutes further feedback that could cause a runaway greenhouse effect. Heat produced by decomposition of organic matter is yet another feedback that leads to even deeper melting.    

  2.1. Reduce methane and nitrogen oxide emissions Reductions in the emissions of methane and nitrogen oxide can be achieved by a change in diet, improved waste handling and better land use. Effective policies such as feebates can impose fees on nitrogen fertilizers and livestock products, while using the revenues to fund pyrolysis of organic waste. 

  2.2. Emissions of other pollutants than conventional greenhouse gases should also be reduced Both the Kyoto Protocol and the IPCC have focused much on reducing CO₂ emissions, as well as other conventional greenhouse gases such as methane and nitrogen oxide. Melting in the Arctic carries the risk of huge additional emissions from peat, permafrost and clathrates, which calls for more immediate mitigation action. All nations should therefore commit to short-term mitigation — long-term mitigation efforts should not be substituted by short-term mitigation or vice versa. As this NASA study points out, for more effective short-term impact, drastic cuts should also be made in other pollutants, such ozone, soot and carbon monoxide. This is further illustrated by the image on the right that shows what causes most radiative forcing (W/m²) when taking into account all pollutants over a 20-year period, from a study published in Science. Reducing short-lived pollutants could significantly reduce warming above the Arctic Circle, finds a study published in Journal of Geophysical Research. A relatively cheap way to achieve such cuts is by encouraging the use of solar cookers and rechargeable batteries to power LED lights. Many types of equipment and appliances can also be powered this way, even when batteries are recharged by hand cranking or pedaling. Electrification of road transport is a crucial part of short-term action, as illustrated by the image, while generation of energy from clean facilities such as solar panels and wind turbines (as also discussed under part 1.1.) will further contribute to reductions in short-lived pollutants. Furthermore, reductions in short-lived pollutants can be achieved by preservation of forests, which justifies financial assistance by rich countries. As said, such assistance should not be used by rich nations as a substitute for domestic action — action is also required domestically by each nation, on all points. The desired shifts can often best be accomplished locally by budget-neutral feebates, i.e. fees on local sales of fuel, engines and ovens, each time funding the better local products, as illustrated by the image below. 

  2.3. Furthermore, consider ways to reflect more solar radiation back into space Discussions of ways to reflect solar radiation can be found at other posts of this geoengineering blog and furthermore at this geoengineering group. 

  Part 3. Adaptation 

 Look at policies that can help people, flora and fauna adapt to climate change. Rich nations are urged to give financial assistance to poorer nations, as well as to facilitate technology transfer, including by preventing that intellectual property protection acts as a barrier to such transfer. 

  3.1. Prepare for extreme weather events Look at safety issues from the perspective of a changed world. Prepare for hailstorms, heavy flooding, severe droughts, wildfires, etc., and grow food that fits such weather patterns best. 

  3.2. Preserve biodiversity Protection of rain forests is well covered in the media. Biodiversity can be further preserved by means of seed banks, parks and wildlife corridors. 

  3.3. Vegetate Fresh water supply and food security require extensive planning, such as selection of best crop. Build facilities for desalination both for fresh water in cities and to irrigate and vegetate deserts and other areas with little vegetation.

image from: Towards a sustainable Economy Leading global warming experts are invited to contribute comments and thoughts as to what constitutes an effective global warming action plan

2011 starts with lowest Arctic sea ice extent on record

The year 2010 was the warmest year on record, as confirmed by the WMO and as illustrated by the NOAA graph below.

This is the more dramatic given that we’re in the middle of a strong La Niña, which pushes temperatures down, while we’ve been in “the deepest solar minimum in nearly a century.” NOAA has meanwhile published the data for 2010. A chart based on NOAA data is added below, with standard polynomial trendline added.

As the NASA map below shows, temperature anomalies are especially prominent at higher latitudes, close to the Arctic. Arctic sea ice cover in December 2010 was the lowest on record for the month, said the WMO, adding that sea ice around the northern polar region shrank to an average monthly extent of 12 million square kilometres, 1.35 million square kilometres below the 1979 to 2000 December average. Furthermore, 2011 has started with the lowest Arctic sea ice extent on record for this time of the year, as shown on the International Arctic Research Center graph below.

On the NSIDC graph below, monthly September ice extent for 1979 to 2010 shows a decline of 11.5% per decade.

The NSIDC image below shows that, at the end of the summer 2010, under 15% of the ice remaining in the Arctic was more than two years old, compared to 50 to 60% during the 1980s. There is virtually none of the oldest (at least five years old) ice remaining in the Arctic (less than 60,000 square kilometers [23,000 square miles] compared to 2 million square kilometers [722,000 square miles] during the 1980s).

Why is all this so important? The Arctic sea ice acts as a giant mirror, reflecting sunlight back into space and thus keeping Earth relatively cool, as discussed in this open letter. If this sunlight instead gets absorbed at higher latitudes, then feedback effects will take place that result in much higher temperatures, in a process sometimes referred to as Arctic amplification of global warming.

Above image is from a recent study, which found that 2010 set a record for surface melting over the Greenland ice sheet. The study warns that surface melt and albedo are intimately linked: as melting increases, so does snow grain size, leading to a decrease in surface albedo which then fosters further melt. A recent study concludes that the rate of Arctic sea ice decline appears to be accelerating due to positive feedbacks between the ice, the Arctic Ocean and the atmosphere. As Arctic temperatures rise, summer ice cover declines, more solar heat is absorbed by the ocean and additional ice melts. Warmer water may delay freezing in the fall, leading to thinner ice cover in winter and spring, making the sea ice more vulnerable to melting during the next summer.

Thin lines are raw data, bold lines are three-point running means…. (C) Summer temperatures at 50-m water depth (red)…. Gray bars mark averages until 1835 CE and 1890 to 2007 CE. Blue line is the normalized Atlantic Water core temperature (AWCT) record … from the Arctic Ocean (1895 to 2002; 6-year averages)…. (D) Summer temperatures (purple) [calculated with a different method]

The IPCC didn't take such feedbacks into account and didn't foresee a total September sea ice loss in the Arctic for this century. Many scientists have repeatedly warned about this, as mentioned in this early 2009 post and this early 2010 post.

Projections that start with more recent data will take some of this feedback into account. Projections that start with 1992 and 1995 data, as in the pink and purple lines on above image, predict a total loss of September Arctic sea ice by 2040 or 2030. A study that used 2007/2008 data as starting point predicts a nearly sea ice free Arctic in September by the year 2037. Albedo change is only one of a number of feedback processes. A rapid rise of Arctic temperatures could lead to wildfires and the release of huge amounts of carbon dioxide and methane that are now stored in peat, permafrost and clathrates, which constitutes further feedback that could cause a runaway greenhouse effect. Heat produced by decomposition of organic matter is yet another feedback that leads to even deeper melting.

The cumulative impact of multiple feedback processes and their interaction reinforces and accelerates Arctic warming, making downward curved projections more applicable than straight line extrapolation of earlier data. The pink dotted line on above chart shows a scenario that reflects the impact of a number of feedback processes. A study at the University of Calgary concludes that, even if we completely stopped using fossil fuels and put no more CO2 in the atmosphere, we've already added enough carbon in the oceans to cause the West Antarctic ice sheet to eventually collapse (by the year 3000), resulting in a global sea level rise of at least four meters. In other words, we have already passed the tipping point for the West Antarctic ice sheet, and additional emissions could cause its collapse to occur much earlier. According to a study published in the journal Nature Geoscience, ice and snow in the Northern Hemisphere are now reflecting on average 3.3 watts of solar energy per square meter back to space, a reduction of 0.45 watts per square meter between 1979 and 2008. "The rate of energy being absorbed by the Earth through cryosphere decline – instead of being reflected back to the atmosphere – is almost 30% of the rate of extra energy absorption due to CO2 increase between pre-industrial values and today," co-author Karen Shell said. A study by by National Center for Atmospheric Research (NCAR) scientist Jeffrey Kiehl found that carbon dioxide may have at least twice the effect on global temperatures than currently projected by computer models of global climate. Melting of ice sheets, for example, leads to additional heating because exposed dark surfaces of land or water absorb more heat than ice sheets. Without changes, this new study warns, Earth's average temperature appears set to rise this century by 29°F (16°C), to levels never before experienced in human history. Such a rise would make that many areas on Earth would become too hot to live in. Humans and other mammals cannot survive prolonged exposure to temperatures exceeding 95°F (35°C), says Steven Sherwood. Heat stress would make many parts of the globe uninhabitable with global-mean warming of about 7°C (12.6°F). Warming of about 21°F (11-12°C) would make places where most people now live uninhabitable. I have made recommendations to deal with global warming for years, most recently in this Global Warming Action Plan. What do you think should be done?

More on Global Warming: Global Warming Action Plan Arctic Sea Ice Falls Below 2007 Low In case you were confused, global warming is real! The Threat of Methane Release from Permafrost and Clathrates Global Warming - Red Alert! Ten Dangers of Global Warming

More on Geoengineering: Target 2020 Funding of Carbon Air Capture Space Hose Afforestation - bringing life into the deserts Biochar Towards a Sustainable Economy

Adding lime to seawater

Shell Oil is funding a project that is studying the potential of adding lime to seawater to store carbon dioxide (CO2) in the sea.

Due to increased CO2 levels, the oceans have become more acid. Adding lime (calcium hydroxide) to seawater will increase the alkalinity of the water, making the water absorb more CO2 and reducing the release of CO2 from the water into the atmosphere.

Tim Kruger, a management consultant at London-based Corven, believes that this can be done most economically where there's plenty of limestone, and plenty of energy that is too remote to exploit for conventional commercial purposes.

"There are many such places — for example, Australia's Nullarbor Plain would be a prime location for this process, as it has 10,000km3 of limestone and soaks up roughly 20MJ/m2 of solar irradiation every day," said Kruger.

Although the process generates CO2 emissions, on paper it sequesters twice as much of the warming gas than it produces. Kruger says the process is therefore 'carbon negative'.

'This process has the potential to reverse the accumulation of CO2 in the atmosphere. It would be possible to reduce CO2 to pre-industrial levels,' he explained.

"We think it's a promising idea," says Shell's Gilles Bertherin, a coordinator on the project, which is being developed in an "open source" manner. "There are potentially huge environmental benefits from addressing climate change — and adding calcium hydroxide to seawater will also mitigate the effects of ocean acidification, so it should have a positive impact on the marine environment."

Sources and Links:

Shell Oil funds "open source" geoengineering project to fight global warming, at:
Mongabay.com

'Turning back the clock on climate change' - A technology to reverse climate change? To reduce ocean acidification? And that also promises to increase food production? Cath O’Driscoll investigates, at:
Chemistry & Industry Magazine

Adding lime to seawater feasibility study, funded by Shell, at: 

www.cquestrate.com

Removing carbon from air - Discovery Channel

Professor David Keith of the University of Calgary is working on a device that removes carbon dioxide directly from ambient air.

Keith has built a tower, 4 feet wide and 20 feet tall, with a fan at the bottom that sucks air in. Keith expects the air coming out at the top to have approximately 50% less carbon dioxide than the air coming in.

The tower features in an episode of Discovery Channel’s new “Project Earth” series on TV. The series has the largest budget of any in Discovery Channel’s history, and it may eventually attract a global viewership of more than 100 million.

The episode on Keith’s research has already aired in the U.S. - if you're missed it, you can watch it on Discovery Channel’s website, at: http://dsc.discovery.com/tv/project-earth/project-earth.html - click on “Episodes.”

If the program hasn't aired in your country, you may not get access to the online episode, but you can read more at: http://dsc.discovery.com/tv/project-earth/lab-books/fixing-carbon/guide1.html - also click on the links under "MORE CARBON".

The picture below describes the Big Picture of recycling, in which I envisage aviation to fund CO2 air capture. When talking about recycling, most people think about recycling of industrial products only. They may also see composting of organic waste as a (second) way of recycling. Instead of composting, I actually envisage organic waste to be burned by means of pyrolysis, in order to produce agrichar and hydrogen. I also envisage a third way of recycling that includes removing CO2 from the air. This CO2 could also be used for the production of agrichar and for commercial purposes such as to enrich greenhouses and for the production of building material, carbon fiber, etc. Furthermore, this CO2 could be used as fuel for aviation.

To tackle emissions by aviation, we can switch to airplanes and helicopters that are powered by batteries and hydrogen, or switch to fuels other than fossil fuel. Growth of algae could be assisted by such captured CO2, which could also be turned directly into fuel.

By financially supporting air capture of CO2 and the use of such CO2 to produce fuel, aviation could close the circle of this third way of recycling. This could make aviation environmentally sustainable. Since government is such a large user of aviation (both the military and civil parts of government), it makes sense for the government to start funding such air capture as soon as possible. An international agreement, to be reached in Copenhagen in 2009, could further arrange for the proceeds of environmental fees on commercial flights to fund such air capture and its use for fuel.



Further links:
http://dsc.discovery.com/tv/project-earth/explores/carbon.html - Discovery Channel

http://www.ucalgary.ca/news/september2008/keith-carboncapture - David Keith

http://www.ucalgary.ca/~keith/AirCapture.html - David Keith

http://www.ucalgary.ca/~keith/Misc/AC%20talk%20MIT%20Sept%202008.pdf - M.I.T.

views.blogspot.com - by Sam Carana

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The post below is added for archival purposes. It was originally posted by Sam Carana at knol in 2009, which has meanwhile been discontinued by Google. The post received 4513 views at knol.

Funding of Carbon Air Capture

HOW CAN CO2 CAPTURE FROM AMBIENT AIR BEST BE FUNDED?

FEES ON JET FUEL CAN HELP FUND THE DEVELOPMENT OF CARBON CAPTURE FROM AMBIENT AIR.

AIR CAPTURE of CO2 (carbon dioxide) is an essential part of the blueprint to reduce carbon dioxide to acceptable levels. Fees on conventional jet fuel seems the most appropriate way to raise funding to help with the development of air capture technology.

Why target jet fuel? In most other industries, there are ready alternatives to the use of fossil fuel. Electricity can be produced by wind turbines or by solar or geothermal facilities with little or no emissions of greenhouse gases. In the case of aviation, though, the best we can aim for, in the near future at least, is biofuel or synthetic fuel, produced from CO2 captured from ambient air. As discussed below, development of these two forms of renewable energy can go hand in hand. 

Carbon air capture and production of synthetic fuel and bio fuel can go hand in hand

Technically, there seems to be no problem in powering aircraft with bio fuel. Back in Jan 7, 2009, a Continental Airlines commercial aircraft (a Boeing 737-800) was powered in part by algae oil, supplied by Sapphire Energy. The main hurdle appears to be that algae oil is not perceived as price-competitive with fossil fuel-based jet fuel.

Additionally, the aviation industry can offset emissions, e.g. by funding air capture of carbon dioxide. The carbon dioxide thus captured could be partly used to produce fuel, which could in turn be used by the aviation industry, as pictured on the top right image. The carbon dioxide could also be used to assist growth of biofuel, e.g. in greenhouses and in algae bags, as described below.

Algae can grow 20 to 30 times faster than food crops. As the CNN video on the right mentions, Vertigro claims to be able to grow 100,000 gallons of algae oil per acre per year by growing algae in clear plastic bags suspended vertically in a greenhouse. Given the right temperature and sufficient supply of light, water and nutrients, algae seem able to supply an almost limitless amount of biofuel.

The potential of algae has been known for decades. As another CNN report describes, the U.S. Department of Energy (DoE) had a program for nearly two decades, to study the potential of algae as a renewable fuel. The program was run by the DoE's National Renewable Energy Laboratory (NREL) and was terminated by 1996. At that time, a NREL report concluded that an area around the size of the U.S. state of Maryland could cultivate algae to produce enough biofuel to satisfy the entire transportation needs of the U.S.

Apart from growing algae in greenhouses, we should also consider growing them in bags. NASA scientists are proposing algae bags as a way to produce renewable energy that does not compete with agriculture for land or fresh water. It uses algae to produce biofuel from sewage, using nutrients from waste water that would otherwise be dumped and contribute to pollution and dead zones in the sea.

The NASA article conservatively mentions that some types of algae can produce over 2,000 gallons of oil per acre per year. In fact, most of the oil we are now getting out of the ground comes from algae that lived millions of years ago. Algae still are the best source of oil we know.

In the NASA proposal, there's no need for land, water, fertilizers and other nutrients. As the NASA article describes, the bags are made of inexpensive plastic. The infrastructure to pump sewage to the sea is already in place. Economically, the proposal looks sound, even before taking into account environmental benefits.

Jonathan Trent, lead research scientist on the Spaceship Earth project at NASA Ames Research Center, Moffett Field, California, envisages large plastic bags floating on the ocean. The bags are filled with sewage on which the algae feed. The transparent bags collect sunlight that is used by the algae to produce oxygen by means of photosynthesis. The ocean water helps maintain the temperature inside the bags at acceptable levels, while the ocean's waves also keep the system mixed and active.

The bags will be made of “forward-osmosis membranes”, i.e. semi-permeable membranes that allow fresh water to flow out into the ocean, while preventing salt from entering and diluting the fresh water inside the bag. Making the water run one way will retain the algae and nutrients inside the bags. Through osmosis, the bags will also absorb carbon dioxide from the air, while releasing oxygen. NASA is testing these membranes for recycling dirty water on future long-duration space missions.

As the sewage is processed, the algae grow rich, fatty cells that are loaded with oil. The oil can be harvested and used, e.g., to power airplanes.

In case a bag breaks, it won’t contaminate the local environment, i.e. leakage won't cause any worse pollution than when sewage is directly dumped into the ocean, as happens now. Exposed to salt, the fresh water algae will quickly die in the ocean.

The bags are expected to last two years, and will be recycled afterwards. The plastic material may be used as plastic mulch, or possibly as a solid amendment in fields to retain moisture.

A 2007 Bloomberg report estimated that the Gulf of Mexico's Dead Zone would reach more than half the size of Maryland that year and stretch into waters off Texas. The Dead Zone endangers a $2.6 billion-a-year fishing industry. The number of shrimp fishermen licensed in Louisiana has declined 40% since 2001. Meanwhile, U.S. farmers in the 2007 spring planted the most acreage with corn since 1944, due to demand for ethanol. As the report further describes, the Dead Zone is fueled by nitrogen and other nutrients pouring into the Gulf of Mexico, and corn in particular contributes to this as it uses more nitrogen-based fertilizer than crops such as soybeans.

The Louisiana coast seems like a good place to start growing algae in bags floating in the sea, filled with sewage that would otherwise be dumped there. It does seem a much better way to produce biofuel than by subsidizing corn ethanol.

Not Millions, but Billions of Dollars!

Carbon air capture could produce a form of renewable synthetic fuel that could be used to power aviation. Carbon air capture could also help produce biofuel to power aviation. It would therefore make sense to encourage development in carbon air capture by imposing fees on conventional jet fuel and by using the proceeds of those fees to help fund air capture of carbon dioxide.

According to zFacts.com, corn ethanol subsidies totaled $7.0 billion in 2006 for 4.9 billion gallons of ethanol. That's $1.45 per gallon of ethanol (or $2.21 per gallon of gas replaced). As zFacts.com explains, besides failing to help with greenhouse gases and having serious environmental problems, corn ethanol subsidies are very expensive, and the political backlash in the next few years, as production and subsidies double, will damage the effort to curb global warming.

On 15 May, 2009, U.S. Secretary of Energy Steven Chu announced that $2.4 billion from the American Recovery and Reinvestment Act will be used to expand and accelerate the commercial deployment of carbon capture and storage (CCS) technology.

At UN climate talks in Bonn, the world's poorest nations proposed a levy of about $6 on every flight to help them adapt to climate change. Benito Müller, environment director of the Oxford Institute for Energy Studies and author of the proposal, said that air freight was deliberately not included. The levy could raise up to $10 billion per year and would increase the average price of an international long-haul fare by less than 1% for standard class passengers, but up to $62 for people traveling first class.

In the light of those amounts, it doesn't seem unreasonable to expect that fees imposed on conventional jet fuel could raise billions per year. Proceeds could then be used to fund rebates on air capture of carbon dioxide, which could be pumped into the bags on location to enhance algae growth. Air capture devices could be powered by surplus energy from offshore wind turbines. With the help of such funding, the entire infrastructure could be set up quickly, helping the environment, creating job opportunities, making the US less dependent on oil imports, while leaving us with more land and water to grow food, resulting in lower food prices.

Cost of Carbon Air Capture

As to the cost of carbon air capture, GRT puts the current cost to harvest one ton of CO2 at $200 andestimates that, 2-3 years from now, it will cost about $150, while the price will come down to $30 to $20 as the technology is fully mature. 

Currently, carbon air capture isn't more expensive than to capture CO2 from smokestacks. The coal industry wants politicians to subsidize "clean coal", but current cost of capture (i.e. excluding transport and storage) is estimated at $100-150/tCO2 initially, possibly reducing to one third of that as the technology matures. That would price coal out of the market, while it doesn't even cover the cost of transporting the CO2 away from the plant and the subsequent sequestration, policing and monitoring all this over many years, etc.

Carbon air capture can be done at off-peak hours when cost of electricity needed for capture is low. Carbon capture from ambient air can also be done anywhere, meaning that it can take place on location, i.e. where the carbon is to be sequestered, which would save on the cost of transport. Or, even better, carbon capture can take place where the carbon is to be used for industrial or agricultural purposes, such as in greenhouses, algae bags or as soil supplements. By mixing carbon with hydrogen, the carbon can also be used to produce carbohydrates, i.e. synthetic fuel that could be used to power shipping and aviation. Such usage can help pay for the cost of carbon air capture.

Professor David Keith (left) of the University of Calgary is working on a tower, 4 feet wide and 20 feet tall, with a fan at the bottom that sucks air in. The tower looks like it's made mainly of plastic, which could be made with carbon produced by such a tower. Inside the tower, limestone or a similar agent is used to bind the CO2 and to split CO2 off by heating it up. The limestone is recycled within the tower, although it does need to be resupplied at some stage. Anyway, the main cost appears to be the electricity to run it. Keith and his team showed they could capture CO2 directly from the air with less than 100 kilowatt-hours of electricity per ton of CO2. At $0.10/kWh, that would put the electricity cost at $10 per ton.

In the U.S., each person emits about 20 tons of CO2 annually. In other words, each person in the U.S. could remove as much CO2 from the air with such a device, with annual operational costs of $200 for 2 Megawatt-hours of electricity. By comparison, a refrigerator consumes about 1.2 Megawatt-hours annually [2001 figures]. Of course, the additional cost of carbon disposal will make it more attractive to use large facilities at places where there's demand for carbon and where the associated economies of scale would facilitate lower operational costs. 

The following comments were posted by Sam Carana under this knol:

Jul 19, 2010

There are several efforts under development to produce a carbon-neutral fuel. Two of them were recently described in article in New Scientist, entitled: Green machine: Cars could run on sunlight and CO2.
http://www.newscientist.com/article/dn18993-green-machine-cars-could-run-on-sunlight-and-co2.html
See also Sandia
https://share.sandia.gov/news/resources/releases/2007/sunshine.html

Whereas many may think that this is a good way to power cars, I agree with you that it makes more sense to have electric cars. However, aviation is a bit more difficult to clean up, that's why aviation in particular can benefit from such technology, and that would justify that aviation made financial contributions to fund such developments.

As air capture technology matures with financial assistance funded by fees on aviation, it will be in a better position to develop into a more general technology used to reduce CO2 in the atmosphere to more acceptable levels.

Jul 19, 2010

In my above reply, I referred to the use of concentrating solar power (CSP) plants to produce temperatures high enough to split water vapor into hydrogen and oxygen, and ambient carbon dioxide into carbon monoxide and oxygen. A team led by Athanasios Konstandopoulos has successfully managed to also split carbon dioxide into carbon monoxide and oxygen in this way. The hydrogen and carbon monoxide can subsequently be combined into hydrocarbons, i.e. synthetic oil.
http://www.newscientist.com/article/dn19308-the-next-best-thing-to-oil.html

Aug 27, 2010

An article in Nature describes the use of a solar cavity-receiver reactor to heat up non-stoichiometric cerium oxide to a temperature at over 1,500 °C, forcing the release of oxygen. Then, to re-oxidize it with H2O and CO2 at below 900 °C to produce H2 and CO – known as syngas, the precursor of liquid hydrocarbon fuels.
http://www.sciencemag.org/content/330/6012/1797

Jan 28, 2011

Milking algae

Instead of harvesting algae for processing into biofuel, there is prospect for "milking" the algae, i.e. extracting oil from the algae without killing them.

This method is followed by Joule Unlimited.
http://www.theglobeandmail.com/news/opinions/opinion/a-brave-new-world-of-fossil-fuels-on-demand/article1871149/

And also by Algenol, Synthetic Genomics (Craig Venter’s venture) and BioCee
http://theenergycollective.com/tyhamilton/50300/joule-cool-not-alone-quest-sunlight-fuel-game-changer

Jul 5, 2011

British company set to make renewable jetfuel

British company Air Fuel Synthesis plans to capture carbon dioxide from the air, and mix it with hydrogen extracted from water through electrolysis, in order to make liquid hydrocarbon fuels for transport, including for aviation.
http://www.airfuelsynthesis.com/technology.html
http://www.airfuelsynthesis.com/technology/technical-review.html
http://www.airfuelsynthesis.com/faqs.html