Carbon dioxide removal (CDR) refers to a number of technologies, the goal being the removal of carbon dioxide from the atmosphere. Among these technologies are bio-energy with carbon capture and storage, biochar, oceanic fertilization, weathering improvements, and direct air capture when combined with storage. CDR is a different approach than removing CO 2 from a pile of emissions from a large fossil fuel source, such as a power plant. The latter reduces emissions into the atmosphere but can not reduce the amount of carbon dioxide already in the atmosphere. Because the CDR removes carbon dioxide from the atmosphere, it creates negative emissions, offsetting emissions from small and scattered point sources such as domestic heating systems, airplanes and vehicle exhaust. This is considered by some to be a form of climate engineering, while other commentators describe it as a form of carbon capture and storage or extreme mitigation. Whether the CDR will meet the general definition of "climate engineering" or "geoengineering" typically depends on the scale to be performed.
CDR needs have been expressed openly by individuals and organizations involved with climate change issues, including IPCC chairman Rajendra Pachauri, UNFCCC executive secretary Christiana Figueres and the World Watch Institute. Institutions with key CDR-focused programs include the Lenfest Center for Sustainable Energy at the Earth Institute, Columbia University and the Climate Decision Making Center, an international collaboration operated by Carnegie-Mellon University's Department of Engineering and Public Policy.
The effectiveness of air catchment mitigation is limited by public investment, land use, geological reservoir availability, and leakage. The reservoir is estimated to be sufficient to store at least 545 GtC. Storing 771 GtC will cause an atmospheric reduction of 186 ppm. To return atmospheric CO 2 content to 350 ppm, we need a 50 ppm atmospheric reduction plus an additional 2 ppm per year of current emissions.
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Carbon dioxide removal is different from reducing emissions, because the first generates carbon dioxide flow from the Earth's atmosphere, while the latter reduces the entry of carbon dioxide into the atmosphere. Both have the same net effect, but to achieve the level of carbon dioxide concentration below the current level, the elimination of carbon dioxide is very important. Also to meet higher concentration levels, carbon dioxide removal is increasingly considered important as it provides the only possibility to fill the gap between the reductions needed to meet the mitigation targets and global emission trends.
In the OECD Environmental Outlook to 2050 released at the United Nations Climate Change Conference 2011, the authors commented on the need for negative emissions, which states "Achieving a lower concentration target (450 ppm) depends significantly on use of BECCS ".
Carbon dioxide absorbers such as concentrated crops or other major producers that bind carbon dioxide to biomass, such as in forests and seaweed beds, are not carbon negative, because sinks are not permanent. This type of carbon dioxide absorber transfers carbon, in the form of carbon dioxide, from the atmosphere or hydrosphere to the biosphere. This process can be undone, for example by forest fires or logging.
The carbon dioxide absorber that stores carbon dioxide in the earth's crust by injecting it below the surface, or in the form of insoluble carbonate salt (mineral absorption), is considered to be negative carbon. This is because they transfer carbon from the atmosphere and store it indefinitely and possibly for long periods of time (thousands to millions of years). However, Carbon Capture technology remains the best, theoretical and yet achieves an efficiency of more than 33%. Furthermore, this process can be quickly canceled, for example by earthquakes or mining.
Maps Carbon dioxide removal
Method
Bio-energy with carbon capture & amp; storage
Bio-energy with carbon capture and storage, or BECCS, uses biomass to extract carbon dioxide from the atmosphere, and carbon capture and storage technology to concentrate and permanently store it in deep geological formations.
The current BECCS (as of October 2012) is the only CDR technology deployed on a full-scale industry, with 550 000 ton CO 2 /year in total operating capacity, divided between three different facilities (as of January 2012).
Imperial College London, UK Center for Meteorology Hadley Center for Climate Prediction and Research, Tyndall Climate Change Research Center, Walker Institute for Climate Systems Research, and Grantham Institute for Climate Change issued a joint report on carbon dioxide removal technology as part of AVOID: Avoiding dangerous climate change of the research program, states that "Overall, from the technology studied in this report, BECCS has the greatest maturity and no major practical obstacles to its introduction into today's energy systems. support early adoption. "
According to the OECD, "Achieving a lower concentration target (450 ppm) is heavily dependent on the use of BECCS".
Biochar
Biochar is made by biomass pyrolysis, and is being investigated as a carbon sequestration method. Biochar is a charcoal used for agricultural purposes that also helps in carbon sequestration, carbon capture or retention. It is made using a process called pyrolysis, which is basically a heating action of high temperature biomass in environments with low oxygen levels. What remains is a material known as charcoal, similar to charcoal but made through an ongoing process, resulting in the use of biomass. Biomass is an organic material produced by living organisms or living organisms recently, most commonly being plants or plant-based materials. GHG emission offsets, if biochar should be implemented, would be a maximum of 12%. This is equivalent to about 106 metric tons of CO 2 equivalent. At the intermediate conservative level, it will be 23% less than that, at 82 metric tons. A study conducted by the British Biochar Research Center has stated that, at a conservative level, biochar can store 1 gigaton of carbon per year. With greater effort in the marketing and acceptance of biochar, the benefits could be the storage of 5-9 gigatons of carbon per year in biochar soil.
Increased weathering
Improved weathering refers to a chemical approach for removal of carbon dioxide involving land or marine engineering. An example of improved land-based weathering techniques is in-situ silicate carbonation. The ultramafic rock, for example, has the potential to store emissions from hundreds to thousands of years of CO 2 according to estimates. The ocean-based technique involves increasing the alkalinity, eg, milling, dispersing and dissolving olivine, limestone, silicate, or calcium hydroxide to overcome ocean acidification and disclosure of CO 2 . Improved weathering is considered one of the cheapest geoengineering options. One example of a research project on enhanced weathering feasibility is the CarbFix project in Iceland.
Direct air capture (DAC)
Carbon dioxide can be removed from ambient air through chemical processes, sequestered, and stored. Traditional modes of carbon capture such as precombustion and postcombustion CO 2 capture from a large point source can help slow down the rate of increase in atmospheric CO 2 concentrations, but only direct removal of CO 2 from air, or "direct air capture" (DAC), can actually reduce global CO concentration 2 when combined with long-term CO storage 2 .
Several engineering proposals have been made to remove CO 2 from the atmosphere, but work in this area is still in its infancy. Among the proposed main technologies, three of which are prominent: Causticization with alkali and alkali-earth hydroxides, carbonation, and organic-inorganic hybrid sorbents consisting of amines supported by porous adsorbents. The 2016 article reviews research in these areas.
One of the proposed methods is with so-called artificial trees . This concept, proposed by climatologist Wallace S. Broecker and science writer Robert Kunzig, envisions a large number of artificial trees around the world to remove ambient CO 2 . This technology is now spearheaded by Klaus Lackner, a researcher at the Earth Institute, Columbia University, whose artificial tree technology can suck up to 1,000 times more CO 2 than air can actually do by real trees a ton of carbon per day if the artificial tree is about the size of an actual tree. CO 2 will be captured in the filter and then removed from the filter and stored.
The chemical used is a variant of the one described below, as it is based on sodium hydroxide. However, in the more recent design proposed by Klaus Lackner, the process can be performed at only 40 Â ° C using a polymer-based ion exchange resin, which takes advantage of moisture changes to induce the release of captured CO. > 2 , instead of using a kiln. This reduces the energy needed to operate the process.
Another substance that can be used is the Metal-organic framework (or MOF's). A special MOF has been specifically created to lock CO 2 by Joeri Denayer.
In 2008, Discovery Channel covered the work of David Keith, from the University of Calgary, who built the tower, 4 feet wide and 20 feet (1,2ÃÆ'â € "6.1 meters), with a fan at the bottom that sucked in air, which out again above. In the process, about half CO 2 is removed from the air.
This device uses the chemical process described in detail below. The system shown on the Discovery Channel is a 1/90,000 scale test system from the capture section; reagents are regenerated in separate facilities. The main cost of the full plant will be the cost to build it, and the energy input to regenerate the chemicals and produce a pure stream of CO 2 .
To put this into perspective, people in the US are emitting about 20 tons of CO 2 per person per year. In other words, everyone in the US will need a tower like the one featured by the Discovery Channel to clear this CO 2 from the air, requiring 2 megawatt-hours of electricity annually to operate. For comparison, refrigerators consume about 1.2 megawatt-hours per year (figure 2001). However, by incorporating many such small systems into one large system, the cost of construction and energy use can be reduced.
It has been proposed that the Solar updraft tower to generate electricity from the hot air currents is also used at the same time to rub the CO 2 amine gravity. Some heat will be needed to grow the amine.
Similar Scrubber CO 2 has also been built by Carbon Engineering. In addition to focusing only on capturing CO 2 , the company also emphasizes the reuse of CO 2 , for example in fuel production, which would thus be carbon-neutral..
Direct air capture has been proposed as a way of producing neutral carbon organic chemicals, by harvesting atmospheric compounds and then using them in the production and synthesis of polymers and fuels.
Climeworks, based in Switzerland, built the first direct industrial-scale air capture plant in Hinwil, in the canton of Zurich, Switzerland. It starts in May 2017, and can rub up to 900 metric tons of CO 2 per year using heat from local waste incineration plants. CO2 is then pumped into a local greenhouse, where it is used to help grow vegetables such as tomatoes and cucumbers.
Climeworks and Reykjavik Energy also started a small test in a direct air capture plant in Hellisheidi, Iceland in October 2017. Using waste heat from local geothermal power plants, the test plant captures up to 50 tons of CO 2 per year tied up with water and injected over 700 meters underground into basaltic basalt rocks. CO 2 reacts with the basal to form solid carbonate minerals.
Sea fertilization
Fertilization of the sea or seafood is a type of climate engineering based on the introduction of nutrients into the upper oceans to increase seafood production and to remove carbon dioxide from the atmosphere. A number of techniques, including fertilization by iron, urea and phosphorus have been proposed.
Example CO 2 scrubbing chemistry
Calcium oxide
Calcium oxide (lime) will absorb CO 2 from atmospheric air mixed with steam at 400 ° C (forming calcium carbonate) and releasing it at 1,000 ° C. This process, proposed by A. Steinfeld, can be done by using renewable energy from thermally concentrated solar power. Lime is made by heating limestone to release CO 2 in it. Lime is mixed with sand for a brick building as a mortar, where it hardens with absorption of CO 2 .
Sodium hydroxide
Air is pumped through a CO 2 buffer as the first step of this process. CO 2 absorber for DAC is designed either as a reverse spray tower or as a current falling-edge film contractor to maximize the contact area between air and solvent and thereby maximize the absorption of the drive. The solvent is regenerated in the causticizing unit by reacting Na 2 CO 3 with Ca (OH) 2 , which also transfers the captured CO 2 to solid crystal form CaCO 3 . The mechanical filter is then used to separate the crystal of CaCO 3 to form water. Since the crystals wet out of the filter, the crystals are dried in a steam dryer. Then the dried crystals are heated in a furnace to produce a pure COO and pure CO 2 gas. CaO is then hydrated to regenerate Ca (OH) 2 used for causticization reaction. Pure CO 2 flow is then compressed and ready to be transported for geological uptake, EOR, or other commercial applications.
1 M NaOH (aq) is a typical solvent concentration because this concentration is limited by the causticization reaction regenerating the solvent not too far from practically a maximum of 2 M NaOH. The furnace/kiln can be moved in a renewable fashion or by burning fuel in place by producing pure oxygen at the air separation unit at the site.
NaOH is economically competitive with other absorbents (eg Amina) used for the DAC process. The DAC process is energy intensive. Calcination (at the furnace) is the most energy-intensive step of this process.
Economic issues
An important issue for CDR methods is their costs, which differ greatly among different technologies: some of which are not sufficiently developed to perform cost assessments. In 2011 the American Physical Society estimated the cost for direct air capture to $ 600/ton with optimistic assumptions. A study of 2018 found this estimate was lowered to between $ 94 and $ 232 per tonne. The IEA and Ecofys Greenhouse Gas R & D Program provides estimates that 3.5 billion tonnes can be removed annually from the atmosphere with BECCS (Bio-Energy with Carbon Capture and Storage) at carbon prices as low as EUR50 per ton, while reports from Biorecro and Global The Carbon Capture and Storage Institute estimates the cost of "under EUR100" per tonne for large-scale BECCS deployments.
Risks, issues and criticism
CDR is slow to act, and requires long-term political and engineering programs to effect. CDR is even slower to affect the acidified oceans. In the path of concentration of Business as usual, the deep ocean will remain acidified for centuries, and as a consequence many marine species are threatened with extinction.
See also
- Bio-energy with carbon capture and storage (BECCS)
- Biochar
- Carbon retrieval and storage
- Scrubber carbon dioxide
- Carbon neutral fuel
- Climate change mitigation
- Climate change mitigation scenario
- Climate engineering
- GHG removal
- List of emerging technologies
- Lithium peroxide
- Low carbon economy
- Virgin Earth Challenge
References
Source of the article : Wikipedia
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