Difference between revisions of "Carbon sequestration"

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[https://www.nature.com/articles/s41477-018-0108-y Farming with crops and rocks to address global climate, food and soil security]  
 
[https://www.nature.com/articles/s41477-018-0108-y Farming with crops and rocks to address global climate, food and soil security]  
 
David J. Beerling, Jonathan R. Leake, Stephen P. Long, Julie D. Scholes, Jurriaan Ton, Paul N. Nelson, Michael Bird, Euripides Kantzas, Lyla L. Taylor, Binoy Sarkar, Mike Kelland, Evan DeLucia, Ilsa Kantola, Christoph Müller, Greg Rau, James Hansen; Nature Plants; 19 Feb 2018
 
David J. Beerling, Jonathan R. Leake, Stephen P. Long, Julie D. Scholes, Jurriaan Ton, Paul N. Nelson, Michael Bird, Euripides Kantzas, Lyla L. Taylor, Binoy Sarkar, Mike Kelland, Evan DeLucia, Ilsa Kantola, Christoph Müller, Greg Rau, James Hansen; Nature Plants; 19 Feb 2018
: The magnitude of future climate change could be moderated by immediately reducing the amount of {{CO2}} entering the atmosphere as a result of energy generation and by adopting strategies that actively remove {{CO2}} from it. Biogeochemical improvement of soils by adding crushed, fast-reacting silicate rocks to croplands is one such {{CO2}}-removal strategy. This approach has the potential to improve crop production, increase protection from pests and diseases, and restore soil fertility and structure. Managed croplands worldwide are already equipped for frequent rock dust additions to soils, making rapid adoption at scale feasible, and the potential benefits could generate financial incentives for widespread adoption in the agricultural sector. However, there are still obstacles to be surmounted. Audited field-scale assessments of the efficacy of {{CO2}} capture are urgently required together with detailed environmental monitoring. A cost-effective way to meet the rock requirements for {{CO2}} removal must be found, possibly involving the recycling of silicate waste materials. Finally, issues of public perception, trust and acceptance must also be addressed.
+
{{Quote|The magnitude of future climate change could be moderated by immediately reducing the amount of {{CO2}} entering the atmosphere as a result of energy generation and by adopting strategies that actively remove {{CO2}} from it. Biogeochemical improvement of soils by adding crushed, fast-reacting silicate rocks to croplands is one such {{CO2}}-removal strategy. This approach has the potential to improve crop production, increase protection from pests and diseases, and restore soil fertility and structure. Managed croplands worldwide are already equipped for frequent rock dust additions to soils, making rapid adoption at scale feasible, and the potential benefits could generate financial incentives for widespread adoption in the agricultural sector. However, there are still obstacles to be surmounted. Audited field-scale assessments of the efficacy of {{CO2}} capture are urgently required together with detailed environmental monitoring. A cost-effective way to meet the rock requirements for {{CO2}} removal must be found, possibly involving the recycling of silicate waste materials. Finally, issues of public perception, trust and acceptance must also be addressed.}}
  
 
[https://insideclimatenews.org/news/20022018/global-warming-solutions-carbon-storage-farm-soil-crushed-volcanic-rock-research How Crushed Volcanic Rock in Farm Soil Could Help Slow Global Warming — and Boost Crops] Georgina Gustin; Inside Climate News; 20 Feb 2018
 
[https://insideclimatenews.org/news/20022018/global-warming-solutions-carbon-storage-farm-soil-crushed-volcanic-rock-research How Crushed Volcanic Rock in Farm Soil Could Help Slow Global Warming — and Boost Crops] Georgina Gustin; Inside Climate News; 20 Feb 2018
: Pulverizing volcanic rock and spreading the dust like fertilizer on farm soils could suck billions of tons of carbon from the atmosphere and boost crop yields on a warming planet with a growing population.
+
{{Quote|Pulverizing volcanic rock and spreading the dust like fertilizer on farm soils could suck billions of tons of carbon from the atmosphere and boost crop yields on a warming planet with a growing population.}}
  
 
[https://www.nature.com/articles/d41586-018-02184-x Why current negative-emissions strategies remain ‘magical thinking’] Nature; 21 Feb 2018
 
[https://www.nature.com/articles/d41586-018-02184-x Why current negative-emissions strategies remain ‘magical thinking’] Nature; 21 Feb 2018
: Decarbonization of the world’s economy would bring colossal disruption of the status quo. It’s a desire to avoid that change — political, financial and otherwise — that drives many of the climate sceptics. Still, as this journal has noted numerous times, it’s clear that many policymakers who argue that emissions must be curbed, and fast, don’t seem to appreciate the scale of what’s required.
+
{{Quote|
 +
Decarbonization of the world’s economy would bring colossal disruption of the status quo. It’s a desire to avoid that change — political, financial and otherwise — that drives many of the climate sceptics. Still, as this journal has noted numerous times, it’s clear that many policymakers who argue that emissions must be curbed, and fast, don’t seem to appreciate the scale of what’s required.
  
: According to the Intergovernmental Panel on Climate Change (IPCC), carbon emissions must peak in the next couple of decades and then fall steeply for the world to avoid a 2 °C rise. A peak in emissions seems possible given that the annual rise in carbon pollution stalled between 2014 and 2016, but it’s the projected decline that gives climate scientists nightmares.
+
According to the Intergovernmental Panel on Climate Change (IPCC), carbon emissions must peak in the next couple of decades and then fall steeply for the world to avoid a 2 °C rise. A peak in emissions seems possible given that the annual rise in carbon pollution stalled between 2014 and 2016, but it’s the projected decline that gives climate scientists nightmares.
  
: The 2015 Paris agreement gave politicians an answer: negative emissions. Technology to reduce the amount of carbon already in the atmosphere will buy society valuable time. The agreement went as far as arguing that incorporating one such technology — bioenergy with carbon capture and storage (BECCS) — could even see the global temperature increase kept to 1.5 °C.
+
The 2015 Paris agreement gave politicians an answer: negative emissions. Technology to reduce the amount of carbon already in the atmosphere will buy society valuable time. The agreement went as far as arguing that incorporating one such technology — bioenergy with carbon capture and storage (BECCS) — could even see the global temperature increase kept to 1.5 °C.
  
: What would negative emissions look like? A Perspective this week in Nature Plants offers another glimpse, and it’s not pretty (D. J. Beerling et al. Nature Plants http://dx.doi.org/10.1038/s41477-018-0108-y; 2018). The review focuses on the idea of enhanced weathering, which aims to exploit how many rocks react with carbon dioxide and water to form alkaline solutions that, over time, find their way into the sea. It’s one of a number of proposed negative-emissions technologies.
+
What would negative emissions look like? A Perspective this week in Nature Plants offers another glimpse, and it’s not pretty (D. J. Beerling et al. Nature Plants http://dx.doi.org/10.1038/s41477-018-0108-y; 2018). The review focuses on the idea of enhanced weathering, which aims to exploit how many rocks react with carbon dioxide and water to form alkaline solutions that, over time, find their way into the sea. It’s one of a number of proposed negative-emissions technologies.
  
: In theory, enhanced weathering could lock up significant amounts of atmospheric carbon in the deep ocean. But the effort required is astounding. The article estimates that grinding up 10–50 tonnes of basalt rock and applying it to each of some 70 million hectares — an area about the size of Texas — of US agricultural land every year would soak up 13% of the annual global emissions from agriculture. That still leaves an awful lot of carbon up there, even after all the quarrying, grinding, transporting and spreading.
+
In theory, enhanced weathering could lock up significant amounts of atmospheric carbon in the deep ocean. But the effort required is astounding. The article estimates that grinding up 10–50 tonnes of basalt rock and applying it to each of some 70 million hectares — an area about the size of Texas — of US agricultural land every year would soak up 13% of the annual global emissions from agriculture. That still leaves an awful lot of carbon up there, even after all the quarrying, grinding, transporting and spreading.
  
: It’s not hard to see why many climate scientists have dismissed the near-impossible scale of required negative emissions as “magical thinking”. Or why the European Academies’ Science Advisory Council said in a report this month: “Negative emission technologies may have a useful role to play but, on the basis of current information, not at the levels required to compensate for inadequate mitigation measures.”
+
It’s not hard to see why many climate scientists have dismissed the near-impossible scale of required negative emissions as “magical thinking”. Or why the European Academies’ Science Advisory Council said in a report this month: “Negative emission technologies may have a useful role to play but, on the basis of current information, not at the levels required to compensate for inadequate mitigation measures.”
 +
}}
 +
 
 +
[https://www.technologyreview.com/2020/06/22/1004218/how-green-sand-could-capture-billions-of-tons-of-carbon-dioxide/ How green sand could capture billions of tons of carbon dioxide] by James Temple; MIT Technology Review; 22 June 2020
 +
{{Quote|'''Scientists are taking a harder look at using carbon-capturing rocks to counteract climate change, but lots of uncertainties remain.'''
 +
 
 +
Mineral weathering is one of the main mechanisms the planet uses to recycle carbon dioxide across geological time scales. The carbon dioxide captured in rainwater, in the form of carbonic acid, dissolves basic rocks and minerals—particularly those rich in silicate, calcium, and magnesium, like olivine. This produces bicarbonate, calcium ions, and other compounds that trickle their way into the oceans, where marine organisms digest them and convert them into the stable, solid calcium carbonate that makes up their shells and skeletons.
 +
 
 +
The chemical reactions free up hydrogen and oxygen in water to pull more carbon dioxide out of the air. Meanwhile, as corals and mollusks die, their remains settle onto the ocean floor and form layers of limestone and similar rock types. The carbon remains locked up there for millions to hundreds of millions of years, until it’s released again through volcanic activity.
 +
 
 +
This natural mechanism draws down at least half a billion metric tons of carbon dioxide annually. The problem is that society is steadily pumping out more than 35 billion tons every year. So the critical question is: Can we radically accelerate and scale up this process?
 +
 
 +
The idea of leveraging weathering to combat climate change isn’t new. A paper published in Nature [https://royalsocietypublishing.org/doi/full/10.1098/rsbl.2016.0905 proposed using silicates] to capture carbon dioxide 30 years ago. Five years later, Exxon researcher Haroon Kheshgi [https://www.sciencedirect.com/science/article/abs/pii/036054429500035F suggested employing quicklime] for the same purpose, and that same year Klaus Lackner, a [https://www.technologyreview.com/2019/02/27/136958/one-mans-two-decade-quest-to-suck-greenhouse-gas-out-of-the-sky/ pioneer in carbon removal], evaluated a variety of potential rock types and methods.
 +
 
 +
But enhanced weathering has gotten little attention in the decades since relative to more straightforward approaches like planting trees, altering agricultural practices or even [https://www.technologyreview.com/2018/06/07/66808/maybe-we-can-afford-to-suck-cosub2sub-out-of-the-sky-after-all/ building CO2-sucking machines]. That’s largely because it’s hard to do, says Jennifer Wilcox, a chemical engineering professor who studies carbon capture at Worcester Polytechnic Institute in Massachusetts. Every approach has its particular challenges and trade-offs, but getting the right minerals at the right size to the right place under the right conditions is always a costly and complex undertaking.
 +
 
 +
More researchers, however, are starting to take a closer look at the technology as the importance of carbon removal grows and
 +
[https://www.sciencedirect.com/science/article/pii/S0009254120301674?via%3Dihub more studies conclude] that there are ways to bring its costs in line with other approaches. If it’s cheap enough on a large scale, the hope is that corporate carbon offsets, public policies like carbon taxes, or sellable by-products from the process, such as [https://www.vox.com/energy-and-environment/2019/11/13/20839531/climate-change-industry-co2-carbon-capture-utilization-storage-ccu the aggregate used in concrete], could create the necessary incentives for organizations to carry out these practices.
 +
 
 +
A handful of projects are now under way. Researchers in Iceland have been [https://www.bbc.com/news/world-43789527 steadily piping a carbon dioxide solution] captured from power plants or carbon removal machines into basalt formations deep underground, where the volcanic rock coverts it into stable carbonate minerals. The Leverhulme Centre for Climate Change Mitigation, in Sheffield, England, is running field trials at the University of Illinois at Urbana-Champaign to assess whether [http://lc3m.org/research/theme-2/ basalt rock dust added to corn and soy fields] could act as both a fertilizer and a means of drawing down carbon dioxide.
 +
 
 +
Meanwhile, Gregory Dipple at the University of British Columbia, along with colleagues from other universities in Canada and Australia, is exploring various uses for the ground-down, highly reactive minerals produced as a by-product of nickel, diamond, and platinum mining. One idea is to simply lay them across a field, add water, and effectively till the slurry. They expect the so-called mine tailings to rapidly draw down and mineralize carbon dioxide from the air, forming a solid block that can be buried. Their models show it could eliminate the carbon footprint of certain mines, or even make the operations carbon negative.
 +
 
 +
“This is one of the great untapped opportunities in carbon dioxide removal,” says Roger Aines, head of the Carbon Initiative at Lawrence Livermore National Lab. He notes that a cubic kilometer of ultramafic rock, which contain high levels of magnesium, can absorb a billion tons of carbon dioxide.
 +
 
 +
“We mine rock on that scale all the time,” he says. “There’s nothing else that has that kind of scalability in all the solutions we have.”
 +
 
 +
'''In the wild'''
 +
 
 +
Project Vesta [https://projectvesta.org/nature-based-climate-change-technology-hits-key-milestone-in-demonstrating-gigaton-scale-carbon-dioxide-removal/ unveiled plans] to move ahead with its pilot study in the Caribbean in May. That closely followed online payment company Stripe’s
 +
[https://projectvesta.org/stripe-and-project-vesta-and-what-this-means-for-us/ announcement that it would pre-pay] the nonprofit to remove 3,333 tons of carbon dioxide for $75 per ton, as part of its
 +
[https://stripe.com/blog/negative-emissions-commitment commitment to spend at least $1 million annually] on negative-emissions projects.
 +
 
 +
Project Vesta has secured local permission to begin conducting sampling at the beaches and intends to announce the location once it’s finalized approvals to move ahead with the experiment, says Tom Green, the executive director. He estimates the total cost for the project at around $1 million.
 +
 
 +
The central goal of the study, which will leave the second beach in its normal state as a control, is to begin addressing some of scientific unknowns that surround coastal enhanced weathering.
 +
 
 +
Research and lab simulations have found that waves will significantly accelerate the breakdown of olivine, and one
 +
[https://climitigation.org/wp-content/uploads/2017/10/Rolling-stones-fast-weather-of-olivine.pdf paper concluded] that carrying out this process across 2% of the world’s “most energetic shelf seas” could offset all annual human emissions.
 +
 
 +
But a major challenge is that the materials need to be finely ground to ensure that the vast majority of the carbon removal unfolds across years rather than decades. Some researchers have found that this would be so costly and energy intensive, and produce such significant emissions on its own, that
 +
[https://www.sciencedirect.com/science/article/abs/pii/S1750583609000656 the approach would not be viable]. Still, others conclude it’ll remove significantly more carbon dioxide than it produces.
 +
 
 +
Project Vesta hopes to get scientists to the site to begin the actual experiment by the end of the year. After they spread the olivine across one of the beaches, they’ll closely monitor how rapidly the particles break down and wash away. They’ll also measure how acidity, carbon levels, and marine life shift in the cove, as well as how much those levels shift further from the beach and how conditions at the control site compare.
 +
 
 +
The experiment is likely to last a year or two. Ultimately, the team hopes to produce data that demonstrates how rapidly this process works, and how well we can capture and verify additional carbon dioxide uptake. All those findings can be used to refine scientific models.
 +
 
 +
Another area of concern, which they’ll also monitor closely, is https://www.frontiersin.org/articles/10.3389/fclim.2019.00007/full potential environmental side effects].
 +
 
 +
The minerals are effectively geological antacid, so they should reduce ocean acidification at least on very local levels, which may benefit some sensitive coastal species. But olivine can also contain trace amounts of iron, silicate, and other materials, which could stimulate the growth of certain types of algae and phytoplankton, and otherwise [https://royalsocietypublishing.org/doi/full/10.1098/rsbl.2016.0905 alter ecosystems] and food chains in ways that could be difficult to predict, says Francesc Montserrat, a guest researcher in marine ecology at the University of Amsterdam and a scientific advisor to Project Vesta.
 +
}}
  
 
== [[CCS|Carbon Capture and Storage]]* ==
 
== [[CCS|Carbon Capture and Storage]]* ==

Revision as of 15:58, 29 June 2020


Sequestering carbon which would otherwise be released as CO
2
, or captured from atmospheric CO
2
, helps mitigate climate change by removing the main greenhouse gas from the atmosphere.

CO
2
could be captured from the atmosphere by biological methods such as growing trees, and increasing the carbon content of soils, by chemical methods such as passing air over substances which absorb atmospheric CO
2
, or even by freezing CO
2
out of the air.

CO
2
can be captured, usually chemically, from the burning of carbon-containing fuels; this is commonly known as Carbon Capture and Storage (CCS). This is usually intended for abating the CO
2
emissions from burning fossil fuels but it can be used with the burning of bio-energy crops to achieve negative emissions, i.e. removing CO
2
from the atmosphere via the biofuel crops. This is referred to (e.g. by the IPCC) as BECCS.

When CO
2
is captured by mechanical/chemical methods it has to be disposed of; this can be in underground repositories such as the formations from which natural gas has been extracted, by chemically reacting it to produce stable compounds or even storing it as 'dry ice' in pits in the Antarctic. In enhanced weathering ground-up rocks are spread over a wide area of land and react with CO
2
and water to produce alkaline solutions which get washed into the oceans.

Overview of technologies

Greenhouse Gas Removal Royal Society, Royal Academy of Engineering; Sept 2018

Greenhouse gas removal (GGR) methods
  • Forestation – Growing new trees and improving the management of existing forests. As forests grow they absorb CO
    2
    from the atmosphere and store it in living biomass, dead organic matter and soils.
  • Habitat restoration – Restoration of peatlands and coastal wetlands to increase their ability to store carbon. This also prevents carbon release through further degradation, often providing a number of other co-benefits.
  • Soil carbon sequestration – Changing agricultural practices such as tillage or crop rotations to increase the soil carbon content.
  • Biochar – Incorporating partially-burnt biomass into soils. Biomass is grown and burned in the absence of oxygen (pyrolysis) to create a charcoal-like product which can stabilise organic matter when added to the soil.
  • Bioenergy with carbon capture and storage (BECCS) – Utilising biomass for energy, capturing the CO
    2
    emissions and storing them to provide life cycle GGR.
  • Ocean fertilisation – Applying nutrients to the ocean to increase photosynthesis and remove atmospheric CO
    2
    .
  • Building with biomass – Using forestry materials in building extends the time of carbon storage of natural biomass and enables additional forestry growth.
  • Enhanced terrestrial weathering – Ground silicate rocks spread on land react with CO
    2
    to remove it from the atmosphere.
  • Mineral carbonation – Accelerating the conversion of silicate rocks to carbonates either above or below the surface to provide permanent storage for CO
    2
    .
  • Ocean alkalinity – Increasing ocean concentration of ions like calcium to increase uptake of CO
    2
    into the ocean, and reverse acidification.
  • Direct air capture and carbon storage (DACCS) – Using engineered processes to capture atmospheric CO
    2
    for subsequent storage.
  • Low-carbon concrete – Altering the constituents, the manufacture, or the recycling method of concrete to increase its storage of CO
    2
    .

Atmospheric CO
2
removal

Emissions reduction: Scrutinize CO
2
removal methods
Phil Williamson; Nature; 10 Feb 2016

The viability and environmental risks of removing carbon dioxide from the air must be assessed if we are to achieve the Paris goals

The Search Is on for Pulling Carbon from the Air Annie Sneed; Scientific American; 27 Dec 2016

Scientists are investigating a range of technologies they hope can capture lots of carbon without a lot of cost
Nations worldwide have agreed to limit carbon dioxide emissions in hopes of preventing global warming from surpassing 2 degrees Celsius by 2100. But countries will not manage to meet their goals at the rate they’re going. To limit warming, nations will also likely need to physically remove carbon from the atmosphere. And to do that, they will have to deploy “negative emissions technology”—techniques that scrub CO
2
out of the air.
Can these techniques, such as covering farmland with crushed silica, work? Researchers acknowledge that they have yet to invent a truly cost-effective, scalable and sustainable technology that can remove the needed amount of carbon dioxide, but they maintain that the world should continue to look into the options. “Negative emissions technologies are coming into play because the math [on climate change] is so intense and unforgiving,” Katharine Mach, a senior research scientist at Stanford University. Last week at the American Geophysical Union conference in San Francisco, researchers presented several intriguing negative emissions strategies, as well as the drawbacks.

Biological

China's Great Green Wall Helps Pull CO
2
Out of Atmosphere

China contributed the most to a global increase in carbon stored in trees and other plants

Terrestrial Biomass and the Effects of Deforestation on the Global Carbon Cycle - Results from a model of primary production using satellite observations Christopher S. Potter; BioScience Oxford Journals; 1999

In this article, I examine several different methods for estimating changes in terrestrial biomass sources of atmospheric carbon dioxide using a combination of global satellite observations, ecosystem model (such as NASA-CASA) predictions of aboveground biomass for the late 1980s, and data on country-by-country changes in global forest cover for the years 1990–1995 (FAO 1997). When the NASA-CASA model is used, the analysis suggests that yearly net terrestrial losses of carbon dioxide from changes in the world's forest ecosystems are 1.2–1.3 Pg of carbon for the early 1990s. This estimate, which accounts for forest area regrowth and expansion sinks in temperate and boreal forest zones, is based on the most recent global maps for observed climate, soils, plant cover, and changes in forest areas from natural and human forces.

Deforestation emissions on the rise - Amazon study suggests denser forest yields will mean more carbon release Jeff Tollefson; Nature News; 29 Jul 2009

Carbon dioxide emissions from deforestation in the Amazon are increasing as loggers and land developers move deeper into dense regions of the forest, a new study suggests. Researchers have analyzed Brazilian deforestation data from 2001–2007 in an effort to quantify emissions as deforestation moves from the forest outskirts to the interior, where more carbon is bound up in plants and soil. Areas that are not formally protected, and thus are most likely to be cleared in the future, contain roughly 25 percent more carbon than areas cleared in 2001, according to the study.

Soil carbon sequestration

What is Soil Carbon Sequestration? UN Food & Agriculture Organisation - Soils Portal

Atmospheric concentrations of carbon dioxide can be lowered either by reducing emissions or by taking carbon dioxide out of the atmosphere and storing in terrestrial, oceanic, or freshwater aquatic ecosystems. A sink is defined as a process or an activity that removes greenhouse gas from the atmosphere. The long-term conversion of grassland and forestland to cropland (and grazing lands) has resulted in historic losses of soil carbon worldwide but there is a major potential for increasing soil carbon through restoration of degraded soils and widespread adoption of soil conservation practices.

How Much Carbon Can Soil Store Soil Quality website

  • Increasing the total organic carbon in soil may decrease atmospheric carbon dioxide and increases soil quality.
  • The amount of organic carbon stored in soil is the sum of inputs to soil (plant and animal residues) and losses from soil (decomposition, erosion and offtake in plant and animal production).
  • The maximum capacity of soil to store organic carbon is determined by soil type (% clay).

Management practices that maximise plant growth and minimise losses of organic carbon from soil will result in greatest organic carbon storage in soil.

Recent interest in carbon sequestration has raised questions about how much organic carbon (OC) can be stored in soil. Total OC is the amount of carbon in the materials related to living organisms or derived from them. In Australian soils, total OC is usually less than 8 % of total soil weight (Spain et al., 1983) and under rainfed farming it is typically 0.7 – 4 %. Increasing the amount of OC stored in soil may be one option for decreasing the atmospheric concentration of carbon dioxide, a greenhouse gas.
Increasing the amount of OC stored in soil may also improve soil quality as OC contributes to many beneficial physical, chemical and biological processes in the soil ecosystem (figure 1) (see Total Organic Carbon fact sheet). When OC in soil is below 1 %, soil health may be constrained and yield potential (based on rainfall) may not be achieved (Kay and Angers, 1999).

A sprinkle of compost helps rangeland lock up carbon

Soil Association: Soil Carbon and organic farming - a review of the evidence of agriculture's potential to combat climate change summary full report

THE FARM THAT GROWS CLIMATE SOLUTIONS Eric Toensmeier; ENSIA; 9 Mar 2016

Editor’s note: The following is adapted from The Carbon Farming Solution: A Global Toolkit of Perennial Crops and Regenerative Agriculture Practices for Climate Change Mitigation and Food Security by Eric Toensmeier (2016). The book introduces the concept of carbon farming, explains how it can help mitigate climate change, and explores strategies for adoption around the world. Published with permission from Chelsea Green Publishing.

Study finds fungi, not plant matter, responsible for most carbon sequestration in northern forests Bob Yirka; phys.org; 29 Mar 2013

(Phys.org) —A new study undertaken by a diverse group of scientists in Sweden has found that contrary to popular belief, most of the carbon that is sequestered in northern boreal forests comes about due to fungi that live on and in tree roots, rather than via dead needles, moss and leaf matter. In their paper published in the journal Science, the team describes their findings after taking soil samples from 30 islands in two lakes in northern Sweden. Scientists have known for quite some time that northern forests sequester a lot of carbon—they pull in carbon dioxide after all, and "breath" out oxygen. But what the trees actually do with the carbon has been a matter of debate—most have suggested that it's likely carried to needles and leaves then eventually drops to the forest floor where over time decomposition causes it to leech into the soil. If that were the case, this new team of researchers reasoned, then the newest carbon deposits should appear closest to the surface of the forest floor. But this is not what they found—instead they discovered that newer deposits were more likely to be found at deeper levels in the soil. This was because, they learned, the trees were carrying much of the carbon they pulled in down to their roots (via sugars) where it was being sequestered by a type of fungi (ectomycorrhizal, aka mycorrhizal fungi) that eats the sugars and expels the residue into the soil.

Chemical Carbon removal

A Canadian start-up is removing CO
2
from the air and turning it into pellets

A pilot project to suck CO
2
out of the atmosphere and turn it into pellets that can either be used as fuel or stored underground for later has been launched by a Vancouver-based start-up called Carbon Engineering. While the test facility has so far only extracted 10 tonnes of CO
2
since its launch back in June, its operations will help inform the construction of a $200 million commercial plant in 2017, which is expected to extract 1 million tonnes per day - the equivalent of taking 100 cars off the road every year. It plans to start selling CO
2
-based synthetic fuels by 2018. "It's now possible to take CO
2
out of the atmosphere, and use it as a feed stock, with hydrogen, to produce net zero emission fuels," company chief executive Adrian Corless told the AFP.

Giant Fans Will Soon Suck CO
2
out of the Atmosphere and Turn It into Fuel

Enhanced weathering

Farming with crops and rocks to address global climate, food and soil security David J. Beerling, Jonathan R. Leake, Stephen P. Long, Julie D. Scholes, Jurriaan Ton, Paul N. Nelson, Michael Bird, Euripides Kantzas, Lyla L. Taylor, Binoy Sarkar, Mike Kelland, Evan DeLucia, Ilsa Kantola, Christoph Müller, Greg Rau, James Hansen; Nature Plants; 19 Feb 2018

The magnitude of future climate change could be moderated by immediately reducing the amount of CO
2
entering the atmosphere as a result of energy generation and by adopting strategies that actively remove CO
2
from it. Biogeochemical improvement of soils by adding crushed, fast-reacting silicate rocks to croplands is one such CO
2
-removal strategy. This approach has the potential to improve crop production, increase protection from pests and diseases, and restore soil fertility and structure. Managed croplands worldwide are already equipped for frequent rock dust additions to soils, making rapid adoption at scale feasible, and the potential benefits could generate financial incentives for widespread adoption in the agricultural sector. However, there are still obstacles to be surmounted. Audited field-scale assessments of the efficacy of CO
2
capture are urgently required together with detailed environmental monitoring. A cost-effective way to meet the rock requirements for CO
2
removal must be found, possibly involving the recycling of silicate waste materials. Finally, issues of public perception, trust and acceptance must also be addressed.

How Crushed Volcanic Rock in Farm Soil Could Help Slow Global Warming — and Boost Crops Georgina Gustin; Inside Climate News; 20 Feb 2018

Pulverizing volcanic rock and spreading the dust like fertilizer on farm soils could suck billions of tons of carbon from the atmosphere and boost crop yields on a warming planet with a growing population.

Why current negative-emissions strategies remain ‘magical thinking’ Nature; 21 Feb 2018

Decarbonization of the world’s economy would bring colossal disruption of the status quo. It’s a desire to avoid that change — political, financial and otherwise — that drives many of the climate sceptics. Still, as this journal has noted numerous times, it’s clear that many policymakers who argue that emissions must be curbed, and fast, don’t seem to appreciate the scale of what’s required.

According to the Intergovernmental Panel on Climate Change (IPCC), carbon emissions must peak in the next couple of decades and then fall steeply for the world to avoid a 2 °C rise. A peak in emissions seems possible given that the annual rise in carbon pollution stalled between 2014 and 2016, but it’s the projected decline that gives climate scientists nightmares.

The 2015 Paris agreement gave politicians an answer: negative emissions. Technology to reduce the amount of carbon already in the atmosphere will buy society valuable time. The agreement went as far as arguing that incorporating one such technology — bioenergy with carbon capture and storage (BECCS) — could even see the global temperature increase kept to 1.5 °C.

What would negative emissions look like? A Perspective this week in Nature Plants offers another glimpse, and it’s not pretty (D. J. Beerling et al. Nature Plants http://dx.doi.org/10.1038/s41477-018-0108-y; 2018). The review focuses on the idea of enhanced weathering, which aims to exploit how many rocks react with carbon dioxide and water to form alkaline solutions that, over time, find their way into the sea. It’s one of a number of proposed negative-emissions technologies.

In theory, enhanced weathering could lock up significant amounts of atmospheric carbon in the deep ocean. But the effort required is astounding. The article estimates that grinding up 10–50 tonnes of basalt rock and applying it to each of some 70 million hectares — an area about the size of Texas — of US agricultural land every year would soak up 13% of the annual global emissions from agriculture. That still leaves an awful lot of carbon up there, even after all the quarrying, grinding, transporting and spreading.

It’s not hard to see why many climate scientists have dismissed the near-impossible scale of required negative emissions as “magical thinking”. Or why the European Academies’ Science Advisory Council said in a report this month: “Negative emission technologies may have a useful role to play but, on the basis of current information, not at the levels required to compensate for inadequate mitigation measures.”

How green sand could capture billions of tons of carbon dioxide by James Temple; MIT Technology Review; 22 June 2020

Scientists are taking a harder look at using carbon-capturing rocks to counteract climate change, but lots of uncertainties remain.

Mineral weathering is one of the main mechanisms the planet uses to recycle carbon dioxide across geological time scales. The carbon dioxide captured in rainwater, in the form of carbonic acid, dissolves basic rocks and minerals—particularly those rich in silicate, calcium, and magnesium, like olivine. This produces bicarbonate, calcium ions, and other compounds that trickle their way into the oceans, where marine organisms digest them and convert them into the stable, solid calcium carbonate that makes up their shells and skeletons.

The chemical reactions free up hydrogen and oxygen in water to pull more carbon dioxide out of the air. Meanwhile, as corals and mollusks die, their remains settle onto the ocean floor and form layers of limestone and similar rock types. The carbon remains locked up there for millions to hundreds of millions of years, until it’s released again through volcanic activity.

This natural mechanism draws down at least half a billion metric tons of carbon dioxide annually. The problem is that society is steadily pumping out more than 35 billion tons every year. So the critical question is: Can we radically accelerate and scale up this process?

The idea of leveraging weathering to combat climate change isn’t new. A paper published in Nature proposed using silicates to capture carbon dioxide 30 years ago. Five years later, Exxon researcher Haroon Kheshgi suggested employing quicklime for the same purpose, and that same year Klaus Lackner, a pioneer in carbon removal, evaluated a variety of potential rock types and methods.

But enhanced weathering has gotten little attention in the decades since relative to more straightforward approaches like planting trees, altering agricultural practices or even building CO2-sucking machines. That’s largely because it’s hard to do, says Jennifer Wilcox, a chemical engineering professor who studies carbon capture at Worcester Polytechnic Institute in Massachusetts. Every approach has its particular challenges and trade-offs, but getting the right minerals at the right size to the right place under the right conditions is always a costly and complex undertaking.

More researchers, however, are starting to take a closer look at the technology as the importance of carbon removal grows and more studies conclude that there are ways to bring its costs in line with other approaches. If it’s cheap enough on a large scale, the hope is that corporate carbon offsets, public policies like carbon taxes, or sellable by-products from the process, such as the aggregate used in concrete, could create the necessary incentives for organizations to carry out these practices.

A handful of projects are now under way. Researchers in Iceland have been steadily piping a carbon dioxide solution captured from power plants or carbon removal machines into basalt formations deep underground, where the volcanic rock coverts it into stable carbonate minerals. The Leverhulme Centre for Climate Change Mitigation, in Sheffield, England, is running field trials at the University of Illinois at Urbana-Champaign to assess whether basalt rock dust added to corn and soy fields could act as both a fertilizer and a means of drawing down carbon dioxide.

Meanwhile, Gregory Dipple at the University of British Columbia, along with colleagues from other universities in Canada and Australia, is exploring various uses for the ground-down, highly reactive minerals produced as a by-product of nickel, diamond, and platinum mining. One idea is to simply lay them across a field, add water, and effectively till the slurry. They expect the so-called mine tailings to rapidly draw down and mineralize carbon dioxide from the air, forming a solid block that can be buried. Their models show it could eliminate the carbon footprint of certain mines, or even make the operations carbon negative.

“This is one of the great untapped opportunities in carbon dioxide removal,” says Roger Aines, head of the Carbon Initiative at Lawrence Livermore National Lab. He notes that a cubic kilometer of ultramafic rock, which contain high levels of magnesium, can absorb a billion tons of carbon dioxide.

“We mine rock on that scale all the time,” he says. “There’s nothing else that has that kind of scalability in all the solutions we have.”

In the wild

Project Vesta unveiled plans to move ahead with its pilot study in the Caribbean in May. That closely followed online payment company Stripe’s announcement that it would pre-pay the nonprofit to remove 3,333 tons of carbon dioxide for $75 per ton, as part of its commitment to spend at least $1 million annually on negative-emissions projects.

Project Vesta has secured local permission to begin conducting sampling at the beaches and intends to announce the location once it’s finalized approvals to move ahead with the experiment, says Tom Green, the executive director. He estimates the total cost for the project at around $1 million.

The central goal of the study, which will leave the second beach in its normal state as a control, is to begin addressing some of scientific unknowns that surround coastal enhanced weathering.

Research and lab simulations have found that waves will significantly accelerate the breakdown of olivine, and one paper concluded that carrying out this process across 2% of the world’s “most energetic shelf seas” could offset all annual human emissions.

But a major challenge is that the materials need to be finely ground to ensure that the vast majority of the carbon removal unfolds across years rather than decades. Some researchers have found that this would be so costly and energy intensive, and produce such significant emissions on its own, that the approach would not be viable. Still, others conclude it’ll remove significantly more carbon dioxide than it produces.

Project Vesta hopes to get scientists to the site to begin the actual experiment by the end of the year. After they spread the olivine across one of the beaches, they’ll closely monitor how rapidly the particles break down and wash away. They’ll also measure how acidity, carbon levels, and marine life shift in the cove, as well as how much those levels shift further from the beach and how conditions at the control site compare.

The experiment is likely to last a year or two. Ultimately, the team hopes to produce data that demonstrates how rapidly this process works, and how well we can capture and verify additional carbon dioxide uptake. All those findings can be used to refine scientific models.

Another area of concern, which they’ll also monitor closely, is https://www.frontiersin.org/articles/10.3389/fclim.2019.00007/full potential environmental side effects].

The minerals are effectively geological antacid, so they should reduce ocean acidification at least on very local levels, which may benefit some sensitive coastal species. But olivine can also contain trace amounts of iron, silicate, and other materials, which could stimulate the growth of certain types of algae and phytoplankton, and otherwise alter ecosystems and food chains in ways that could be difficult to predict, says Francesc Montserrat, a guest researcher in marine ecology at the University of Amsterdam and a scientific advisor to Project Vesta.

Carbon Capture and Storage*

CO
2
Disposal

Basalt mineralisation

CarbFix Iceland

Rapid carbon mineralization for permanent disposal of anthropogenic carbon dioxide emissions Juerg M. Matter, Martin Stute, Sandra Ó. Snæbjörnsdottir, Eric H. Oelkers, Sigurdur R. Gislason, Edda S. Aradottir, Bergur Sigfusson, Ingvi Gunnarsson, Holmfridur Sigurdardottir, Einar Gunnlaugsson, Gudni Axelsson, Helgi A. Alfredsson, Domenik Wolff-Boenisch, Kiflom Mesfin, Diana Fernandez de la Reguera Taya, Jennifer Hall, Knud Dideriksen, Wallace S. Broecker; Science; 10 Jun 2016

Carbon capture and storage (CCS) provides a solution toward decarbonization of the global economy. The success of this solution depends on the ability to safely and permanently store CO
2
. This study demonstrates for the first time the permanent disposal of CO
2
as environmentally benign carbonate minerals in basaltic rocks. We find that over 95% of the CO
2
injected into the CarbFix site in Iceland was mineralized to carbonate minerals in less than 2 years. This result contrasts with the common view that the immobilization of CO
2
as carbonate minerals within geologic reservoirs takes several hundreds to thousands of years. Our results, therefore, demonstrate that the safe long-term storage of anthropogenic CO
2
emissions through mineralization can be far faster than previously postulated.

Underground injections turn carbon dioxide to stone Eli Kintisch; AAAS Science; 10 Jun 2016

Researchers working in Iceland say they have discovered a new way to trap the greenhouse gas carbon dioxide (CO
2
) deep underground: by changing it into rock. Results published this week in Science show that injecting CO
2
into volcanic rocks triggers a reaction that rapidly forms new carbonate minerals—potentially locking up the gas forever.