Dare to Hope - Climate Restoration - Three ways to get CO2 levels back to pre-industrial 300 ppm by 2050 - potentially pay for themselves - many more ways to remove CO2 in IPCC AR6 chapters 7 and 12
Dare to Hope - Climate Restoration - Three ways to get CO2 levels back to pre-industrial 300 ppm by 2050 - potentially pay for themselves - many more ways to remove CO2 in IPCC AR6 chapters 7 and 12
We have to reach zero emissions first, and to do that we need to greatly reduce the CO2 emissions especially from energy. That then leaves a portion of emissions that we can’t stop emitting of maybe 5% maybe more depending on how well we can decarbonize various industries especially the plastics industry. So we then need ways of absorbing that extra CO22 and the main way through to 2050 is through land use change, Agricultre and forestry. After 2050 we may need to use other methods such
It's only after 2050 that we need other ideas like Bio Energy Carbon Capture and Storage. That was the main way to do it in the 2018 report but the 2023 report says we need to supplement it with other methods, assuming the carbon sinks in forests do saturate.
BECCS is still an important part of the way forward but especially in the 2050s and onwards we may need to use other methods for the remaining 5% or 10% or whatever it turns out to be that we can't substitute directly with renewables.
There’s a long section about this now in AR6 / WGIII CHAPTER 7 which is the report that focuses on mitigation and what we can do to achieve net zero, and the chapter in that report about carbon capture. Then there’s another long section in chapter 12.
It’s surprising to me how few authors are aware of this material. I recommend everyone to at least glance at Cross-Chapter Box 8, Figure 1: Carbon Dioxide Removal taxonomy before you start an article on the topic.
This is true not just of journalists, also even of many experts. So many experts write blog posts or op eds about the impossibility of carbon dioxide removal at scale without reading the IPCC report chapters on the topic. That is why they did the IPCC reports, not just for the general public, but for experts too. Most of them are very expert on their topic but only aware of a tiny part of the picture, like spending your life studying one piece in a giant jigsaw puzzle.
This is a summary of the main methods:
.
Many ways to do carbon dioxide removal
- might need these in 2nd half of century
to stay at zero emissions once we get there
Cross-Chapter Box 8, Figure 1: Carbon Dioxide Removal taxonomy
. Climate Change 2022: Mitigation of Climate Change
However it is possible to be far more ambitious if we want to, once we get to net zero. Few even of the most ambitious activists have this as a demand. It is not just zero emissions by 2050 or 2035 or 2030. That would stabilize our CO2 levels at the level where the planet is warmer by another half degree than it is now, 1.5 C warmer on average above pre-industrial.
However, a group of researchers now aim to get our climate’s CO2 levels back to the levels of the nineteenth century by 2050. That is right, to roll back all the way to preindustrial 300 ppm by 2050. They call this objective “Climate restoration”.
These are people who not only dare to hope but are going forward and working on the ways it can be done. This would be additional to our objectives to reduce emissions to carbon zero. We currently ADD over 40 gigatons a year. If the aim was to go back to preindustrial 300 ppm, instead we would aim to REMOVE 50 gigatons a year.
This blog post also looks at carbon dioxide removal to stay at net zero. We may need to do carbon dioxide removal by the second half of the century.
AR6 / WG3 said that there's a possibility that forests and ecosystems may saturate and we may need to use measures of removing carbon dioxide from the atmosphere in the second half of this century with a long section about many ways we can do it including solutions like biochar which increases fertility of soils as an extra benefit, seaweed farms, adding alkaline rocks like crushed basalt to croplands, adding olivine sand to the oceans by spreading them on beaches or tipping them into the sea to reduce its acidity, and increasing soil carbon content in many ways each of those could in principle remove tens of gigatons a year if done at scale.
We ,may not want to go back to pre-industrial. We might decide as a civilization that we prefer the warmer 1.5 C or nearly 2 c temperature once we are adapted to it. The issue is the speed rather than the end temperature. See my:
But suppose we did want to go back to preindustrial by removing 50 gigatons a year or more.
These are the three projects that could pay for themselves and each individually also has the potential to scale up to 50 gigatons a year
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The paper I am summarizing is this one:
from their resources page.
Their home page is here:
Then there’s Project Drawdown which looks at many ways to remove CO2 in the atmosphere. You can browse their analysis of various solutions here
. Drawdown Climate Solutions Library
I have already done a blog post about the giant kelp seaweed farming which has vast potential. One estimate is that if it was scaled up hugely, this could sequester 53 gigatons a year from 9% of the ocean surface - that’s more than current global emissions. It would also work by reversing ocean acidification. That is a lot of seaweed farming - and it is important to look at the effects of such large scale farming - the proponents argue that if it is used in the deep sea then these areas are effectively deserts - rather similar to greening terrestrial deserts - and that they would be overwhelmingly beneficial to the seas - but this needs to be checked with research underway and giant kelp seaweed farming gradually expanding in use.
could produce sufficient biomethane to replace all of today’s needs in fossil-fuel energy, while removing 53 billion tonnes of CO₂ per year from the atmosphere… This amount of biomass could also increase sustainable fish production to potentially provide 200 kilograms per year, per person, for 10 billion people. Additional benefits are reduction in ocean acidification and increased ocean primary productivity and biodiversity. (PDF) Negative Carbon Via Ocean Afforestation
See also post in “The Conversation”: How farming giant seaweed can feed fish and fix the climate
My giant kelp article is here:
- but there are several other ideas I didn't know could potentially scale like this.
Just looking at these ideas helps move the goal posts - resets the boundaries of what is possible.
Please don’t misunderstand. I am not saying this is easy. It is going to be a significant challenge to reach carbon zero by 2050 never mind carbon negative.
However, whether or not we eventually do this - just knowing that this is technologically possible can help us have more hope and counteract the cynicism and skepticism of those who keep saying our situation is hopeless. There is so much resetting of goal posts at the doomsday end of the scale with authors vying to make the situation seem more and more dire. Why not do some resetting of the goal post at the other end of the scale?
Our situation is only hopeless if we give up hope. There is much we can do and much we are already doing too!
CARBON NEGATIVE LIMESTONE AGGREGATE
One is limestone made from CO2 reacted with calcium containing reducing rocks (e.g. slag) - they say it could be paid for by sales of the limestone.
The first use of carbon negative concrete was in 2016 to pave the boarding area to San Francisco international airport - so if you live in San Francisco and go to that airport to take a flight you walk over the world's first carbon negative concrete :). They say there is potential to sequester 50 gigatons a year just from synthetic limestone, if this takes off and substitutes for all the quarried aggregate currently mined.They synthetic limestone would replace the sand and crushed rock currently used for aggregate in concrete.
CO2 is emitted in the process of making cement because it is done by converting calcium carbonate to calcium oxide, driving off CO2, and also because it requires use of energy which is usually fossil fuel based.
The COSIA Carbon XPRIZE Challenge is a competition to convert CO2 into products with highest net value from either a coal or gas power plant. In April 2018, ten finalists were given $5 million each to demonstrate their technologies large scale in the real world. The winner gets a $7.5 million grand prize announced in March 2020.
Five of the ten are focused on carbon minerallization technology. One of them is a team from Aberdeen that hopes to use CO2 capture to make the entire concrete industry carbon negative. The Carbon Capture Machine precipitates it into calcium and magnesium carbonates (much like stalactites in caves) as a carbon negative replacement for ground calcium carbonate (GCC) which is needed for concrete. If this works on a commercial scale it can decarbonize the concrete industry, or 6% of the world’s annual CO2 emissions. If they can make it commercially viable, GCC has a market value of $20 billion.
This project seems to be a similar idea
There the geomass refers to “common rock waste and/or industrial waste materials that contain available alkalinity, which recharges the capture solution, and metal ions such as calcium, magnesium, and iron”.
This is how they describe the process:
The carbonate rocks produced are used in place of natural limestone rock mined from quarries, which is the principal component of concrete. CO2 from flue gas is converted to carbonate (or CO3=) by contacting CO2 containing gas with a water-based capture solutions. This differentiates Blue Planet from most CO2 capture methods because the captured CO2 does not require a purification step, which is an energy and capital intensive process. As a result Blue Planet’s capture method is extremely efficient, and results in a lower cost than traditional methods of CO2 capture.
…
Using Blue Planet products the carbon footprint of a cubic yard of concrete can be not just reduced, but the cubic yard of concrete can become carbon-negative by two specific methods: First, by replacing conventional fine and coarse aggregate (sand & gravel) with Blue Planet synthetic limestone aggregate, which is 44% by mass CO2 now converted to a permanent crystalline solid state in CaCO3, the entire carbon footprint of the portland cement can be completely off-set and can further be more than offset, taking the carbon footprint into the negative carbon range. For instance a typical cubic yard of concrete may have 3000 lb.s of aggregate; if it is all Blue Planet synthetic limestone, then 44% of it is sequestered CO2 (from a power plant or other industrial plant), or 1320 lbs of CO2 is offset.
. Economically Sustainable Carbon Capture - Blue Planet
. Carbon Upcycling makes new CO2ncrete from CO2 and chemicals, competing directly with the $400 billion concrete industry - in places like California with a carbon tax and mandate for low carbon building materials.
. CarbonCure Technologies injects CO2 into wet concrete while it is being mixed. They are aleady in commercial use with 100 installations across the US, retrofitting concrete plants for free then charging a licensing fee. It may take up to 20 years to be used on scale for reinforced concrete, because that’s needed as a durability testing period.
For more on this see Between a Rock and Hard Place: Commercializing CO2 Through Mineralization
USING IRON AS FERTILIZER FOR DEEP SEA OFF SHORE OCEAN PASTURES
Another is iron fertilization of the oceans. The iron would be used over 1% of the ocean. However, unlike some ideas it would not be just dumped willy nilly but as a kind of fertilizer as a part of ocean management to restore fisheries. Also it would be used in the deep sea off shore so as not to impact on coastal ecosystems.
Each island or coastal state restoring pastures would likely to have around 30 pastures half fertilized and half fallow each year. Ten such projects would give you the 300 pastures needed to sequester 50 gigatons a year.
MARINE AGRICULTURE
Then there is the giant kelp I already covered before. It can grow 2 feet per day. (It is very eficient at photosynthesis which is why it is so dark in colour - it absorbs nearly all the sunlight that falls on it and converts it to energy by using "antenna" pigments to take advantage of the green light as well that ordinary plants reject).
As with the iron fertilization only about 1-2% of the ocean needs to be used for seaweed farming. They don't mention in the white paper but a natural place for large scale seaweed farming might be the big ocean gyres like the Sargasso sea - in total they cover about the right area of the ocean. But to start with likely secluded regions with good weather condtions. We have seaweed farming already - a traditional practice from China and Korea that is now expanding throughout the world and has been shown to work well even at high latitudes.
Those are the three main big ones that each individually could sequester that 50 Gigatons if we were to do some big initiative to make sure they scale up as much as this quickly. There is a lot of work needed from the conceptual idea that we could do this to actualy doing it and of course it needs careful impact assessment. However, none of this seems impossible if we had the will and their preliminary look at impact suggets they would be low impact too
Those three projects would pay for themselves - just as seaweed farming already pays for itself, but would need encouragement to expand so rapidly as that
.
OTHER FORMS OF OCEAN CAPTURE
There are several ocean based ways of removing carbon - and all have the advantage they also reduce the acidity of the oceans
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The three main categories are
Seaweed Cultivation for Carbon Sequestration - Cultivating seaweeds (macroalgae) and sequestering the carbon embedded in it. Cultivation opportunities include existing coastal farms and expansion into offshore waters. Sequestration options include burial in the deep sea/land and/or harvesting for bioenergy, as well as production of long-lived bio-products.
Ocean Alkalinity Enhancement - Surface addition of alkaline minerals (either mined or manufactured) to seawater to increase alkalinity and, therefore, carbon storage in seawater.
Direct Ocean Capture - Use of chemistry, electrochemistry, gas exchange, or other methods to capture and/or store atmospheric CO2 from seawater.
Microalgae Cultivation and Sequestration•Cultivating microalga[quote from: Ocean based CDR.]
See also
DIRECT AIR CAPTURE - EXPENSIVE BUT COULD DO IT RIGHT NOW
We could also do it with direct air capture - this means without doing anything to the Earth's ecosystems, no marine pastures, no giant kelp farms. Not using the CO2 for anthing (so not the limestone either). Just pumping into the ground.
Sometimes people say this technology doesn’t exist yet. That is not true. The technology is straightforward and does exist and is already technically feasible but currently very expensive.
Using current technology for direct air capture “as is”, you are talking about a few percent of the total world economy to sequester 50 gigatons a year.
It currently costs $600 per ton to sequester CO2 and pump it into deep basalt formations where it is permanently fixed. The formations exist to do this, direct capture from the atmosphere, and Climeworks predict this will go down to $100 per ton by 2025. At that price it would cost —$3 trillion a year for 30 years compared to a world economy of $80 trillion and $1.9 trillion a year military spending. At current prices it is $18 trillion a year.
However costs of direct air capture likely go down further than that eventually.
They also talk about various other projects that can sequester some but not all the CO2 but don’t pay for themselves.
OCEAN ALKALIZATION
This involves just dumping alkaline rock in the sea to reverse acidification which would then pull CO2 out of the atmosphere. This would cost around $100 a ton, similar to direct air capture but with the side effect of also reversing acidification of the oceans. It is not likely to be done as there is no other major benefit from it and it is expensive, similarly to the direct air capture. But technically we could do this.
BIOENERGY WITH CARBON CAPTURE AND SEQUESTRATION (BECCS).
They say this is similar in cost to direct air capture. However this seems a bit pessimistic, depending how it is done. We can do some of this using agricultural wastes which currently are often generated far from where the plants are grown. Instead of letting it rot and produce methane, it could be burnt and the CO2 sequestered. Some element of BECCS is likely to happen anyway for these reasons.
Biofuels can also be grown in arid regions where few other crops are possible. For example the desert plant agave can be used for biofuels on land that is not currently used for agriculture (though, agave can also be grown for silage for animals - see later).
Also - for instance there is the idea of using cover crops grown in winter for biofuels. This does not compete with the commercially grown crops as it is grown at a time when there is no other crop on the ground and in high latitude farming the ground is bare over winter. It improves the soil as well as providing biofuels. The first ever commercial carbon zero flight used biofuel manufactured this way.
Quantas did the first sustainable flight from the US to :Australia using biofuels in 2018. It used Brassica Carinata which is a type of mustard seed that is planted off-season so doesn’t compete with crops and gives landowners a supplementary income. It reduces erosion, conserves soil nutrients and is water efficient.
In a 15 hour flight, it used 24,000kg of blended biofuel. It saved 18,000kg in carbon emissions. .
There is also the possibility of algae for biofuel, which has never quite been commercially viable but may be so in the near future. I cover some of these ideas in my
Another recent paper found that by using bacteria to convert the biowaste into jet fuel they can make a biofuel that is more energy intensive and so lets a plane travel further with the same sized tank. It makes lignin as a byproduct and if this can be converted into a commercially viable product to offset some of the cost of production of the fuel - then it may offset enough of the cost to make it cost -competitive with normal jet fuel.
Australia is also the native home to the Eucalyptus tree which produces terpene which is an excellent precursor for jet fuel. Scientists are working on using the genes of wild Eucalyptus to breed new varieties that could be grown for jet fuel.
Then there’s also the possibility of jet fuel from algae. The idea of making fuel from algae was big for five years from about 2005 to 2010 with many optimistic startups that failed.
It turned out to be far harder to do than originally expected. It works on paper but when you try to scale it up then it can easily end up that you use more energy making the fuel than you get from burning it.
However advances in processing the algae as well as new varieties of algae are helping to make them more feasible again. This may be possible in the near future but is not feasible quite yet.
This is about a new more efficient way of getting the lipids from the algae
Their conclusion seems valid, biofuels can’t take us all the way to 50 gigatons a year of carbon capture and storage (except maybe through some game changer such as very efficient easy growth of algae). However, there are many ways we can make commercial use of BECCS that might offset some few gigatons a year potentially, depending how things develop.
AGRICULTURE, FORESTRY, AND IMPROVED LAND USE (AFOLU).
This is already part of many of the plans for carbon zero by 2050, but can only offset a few percent of emissions. These proijects are underway already in many places and do pay for themselves, I am not sure why they say they can't pay for themselves.
For some examples of the vast numbers of reafforestation projects and projects to reverse desertification around the world see my
I also have a section about this in my
These things are already happening so it is a bit puzzling that they don’t seem to think they are viable compared to the other ideas they favour more.
The improved agricultural yields and nature services usually more than pay for the costs of the projects in the long term and though they may have upfront costs the profits can sometimes be considerable.
There is an interesting paper about this on Carbon Brief and I discuss it in my vlog here:
The Carbon Brief post: Guest post: Ten ways to use CO2 and how they compare
The paper: The technological and economic prospects for CO2 utilization and removal
As I mention there, one example of a way to improve the land with greatly increased carbon sequestration is Terra preta.
We tend to think of the Amazon as being virgin forest with modern humans cutting it down for the first time. However, though much of it has never been cut down, the conquistadors report that when they first came to the Amazon river there were vast areas of agricultural land to either side of the river. This land all got abandoned and the forests grew up over them when their civilization collapsed as a result of the European conquests. However the traces still remain in the form of this biochar mixed into the soil of the tropical rainforest in these regions.
They used to burn wood in low temperature like charcoal to make biochar and incorporate this into the soil
We can also see traces of this past from the geoglyphs for the areas of the amazon that used to be agriculture then turned back to forest again and now revealed with deforestation. This is an example:
Geoglyphs at Fazenda Colorada in the Rio Branco area of the Amazon rainforest. The square area is where they lived. The earthworks may be defensive like earthworks in many parts of the world, but unusually the ditch is inside rather than outside the earthwork so it is not like a moat. Imagine a castle but with the moat inside the walls. One suggestion by academics is that the moat may have been used for aquaculture, maybe for keeping freshwater turtles. This site is carbon dated to around 1283 (1244-1378). Paper here.
Here is a long talk about this ancient culture, about how they changed the environment to make habitats for various plants and animals and attempts to understand their archaelogical remains including these geoglyphs.
BBC Four - Unnatural Histories, Amazon
Land Carvings Attest to Amazon’s Lost World
We are still working on how best to use Terra preta in modern agriculture but it has potential for a great deal of carbon sequestration at the same time as improving yields.
This summary graph sums up some of the results from the paper
:
. Guest post: Ten ways to use CO2 and how they compare
Looking at just the profitable sequestration scenarios and the maximum for each and ignoring the ones with potential to store for just days or weeks, then they are
Biochar - earn $65 per tonne, up to 1 Gt Co2, so that would be earnings of $65 billion from Biochar
Soil improvement, earning of $20 to $90 per tonne, up to 1.9Gt CO2 per year, total earnings $38 to $171 billion per year
Forestry - up to 1.5Gt CO2, earning $40 through to cost of $10 per tonne CO2. Total earnings up to $60 billion per year though at lower end it costs $15 billion a year.
In this way, they found a total of up to 4.4 Gt a year sequestration (or more than a tenth of our current emissions), earning up to $296 billion a year.
I’ve left out the enhanced oil recovery as we would not have much of that by 2050 if we reach zero emissions by then.
They also leave out the seaweed farming - it is not a comprehensive study but a selected study of ten potential forms of CO2 use.
Some have a lot of potential but current costs are high - this can go down with reducing costs.
CO2 fuels: 1-4.2Gt CO2 a year at up to $670 per tonne of CO2 (these are fuels made synthetically from CO2, water, and some other trace quantities of materials)
Microalgae 0.2-0.9GtCO2 per year. Costs between $230 and $920 per tonne of CO2
Curing cement, 0.1-1.4Gt CO2. Could be earnings of $30 per tonne through to costs of $70 per tonne.
They also mention
Enhanced weathering
Crushing rocks, such as basalt, and spreading them on land can result in the accelerated formation of stable carbonate from atmospheric CO2. It is likely that doing this on agricultural lands will result in enhanced yields. However, the very early-stage nature of this pathway means that we have not made 2050 estimates for it.
Guest post: Ten ways to use CO2 and how they compare
The paper
The technological and economic prospects for CO2 utilization and removal
For synthetic fuel, there is one idea from Australia that could make it more practical and of economic value. Normally with renewables you store the excess capacity, for instance in pumped hydro storage, and then you return it to the grid at times of demand.
But - suppose instead you just over-produce the renewables and then use the excess power to make synthfuels?
Australia has a vast capacity for renewables, far more than it’s population needs, of around 12 terawatts. More than the total installed electricity capacity of the world.
The idea here is to press ahead with renewables to far more than the population needs for istelf and to use much of that excess capacity to make ammonia:
But it could be used for aviation fuel as well. Another possibility is for Tasmania.
Tasmania is close to 100% renewables. What is more they are planning to double the capacity and export power to the Australian mainland and act as the "battery of the nation" to balance renewables in Australia.
How Tasmania is transforming into a renewable energy powerhouse - Create
The hydro power would also let them make hydrogen fuel with the equipment running constantly, which means they can make more efficient use of it and so undercut the cost of those who use the same equipment but with only solar and wind and intermittently. So hydrogen may become a major Tasmanian export.
Tasmania sees renewable hydrogen as major economic opportunity for island state
LAND USE CHANGES WITH VAST POTENTIAL
[I NEED TO CHECK THE FIGURES IN THIS SECTION]
Going back to the CLIMATE RESTORATION white paper, they also mention some projects that could have vast potential if they were used by farmers worldwide but they say that farmers would not be likely to adopt them - so they are pessimistic again. But the projects are interesting, and I don’t understand why they are so pessimistic about widespread adoption by farmers when they would benefit farmers - they do explain but their explanation doesn’t convince me.
It’s about farmers being risk averse - but - they are risk averse because they have hardly any funds, and they can lose their farm if they take a financial risk that in a wealtheir country would be something they can take on and even get insurance for, if it doesn’t work out. Wealthier countries can help with funding for pilot projects, direct grants, low interest or zero interest loans, low cost insurance etc. I.e. it’s not something we need to take as a fixture in our world that poor farmers are risk averse, we can address this and deal with the reasons they are risk averse.
Anyway, let’s look at them and you can see what you think yourself about whether they have the potential they seem to have:
REGENERATIVE GRAZING - 98.5 GIGATONS A YEAR POTENTIAL WORLDWIDE
Regenerative grazing if it was rolled out worldwide would sequester 98.5 gigatons a year. This means making sure that pastures worldwide are managed optimally, that would include replanting the grass if needs be. It is how the best pasture is managed but many countries just can't afford to do it, although it is better for the farmers too.
This is all they say about this idea:
The logistical challenge of scaling new agricultural practices is considerable: Farmers, especially in poor regions, tend to be risk averse. It is unlikely that all farmers would engage in the retraining, retooling, and capital investment required to engage in improved land management practices that increase CO2 storage.
Yes of course they are risk averse, indeed they may not have any way to access loans at all, and if they default on the loan they lose their farm. They need support with grants and low interest loans, as well as the example of neighbour farmers who have done it and succeeded. A project that benefits them agriculturally such as improved pasture that doubles the number of cows they can keep would surely take off quickly enough around the world if there was enough funding put into it e.g. through action such as the Green Climate Fund or similar scaled up to make such a project possible.
We are talking about big investment here, but investment that eventually pays back with improved pastures, and better food security worldwide and reduced pressure on forests (increase the pasture productivity in Brazil and there would not be any need to deforest any more).
I go into this with the example of Brazil towards the end of this article:
There is more reforestation than deforestation in all the continents except Africa and South America. If it weren't for humans the Scottish hills would be covered in trees right to the summit for all except the very highest hills and all the landscape would be wooded. We have more forest cover every year in the UK. Also much of it now is natural forest - it used to be that most trees planted were commercial plantations but now it's turned around.
I talk about that here:
Also in
BIOLOGICALLY ENHANCED COMPOST - 184 GIGATONS A YEAR POTENTIAL WORLDWIDE
Another method is BEAM which is a project developed in Mexico that involves specially biologically enhanced compost which sequesters more carbon and improves the soil and increases crop yields. They estimate 184 gigatons a year for this.
They conclude that
Just transitioning 10 percent of agricultural production to best practice regenerative systems will sequester enough CO2 to reverse climate change and restore the global climate.
Ten percent of agricultural lands under BEAM would sequester 18.4 Gt of CO2/yr. Ten percent of grasslands under regenerative grazing would sequester 9.8 Gt of CO2/yr. This would result in 28.2 Gt of CO2/yr being sequestered into the soil which is just under double the amount of sequestration needed to draw out more CO2 than is currently being emitted.
These examples are shovel-ready solutions as they are based on existing practices. There is no need to invest in expensive, potentially dangerous and unproven technologies such as carbon capture and storage or geo-engineering. All that is needed is to scale up the existing good regenerative agriculture practices.
Reversing Climate Change through Regenerative Agriculture - Regeneration International
OTHER REGENERATIVE FARMING METHODS
There is a survey of several other calculations like this in this document available from the FAO, of various methods that can sequester tens of gigatons of CO2 per year if rolled out over degraded land worldwide:
24 comparision trials in Meditterranean climates between organic and non organic systems - 3.5599 tons of CO2 per hectare per year- globally 17.4 Gt per year if extrapolated
Carbon sequestration at Sekem, oldest organic farm in Egypt. Continued to sequester 3.303 tons per hectare for 30 years. Globally these practices could sequester 16 Gt per year
Rodale Compost Utilization Trial sequestered 8.2208 tons per year. globally would sequester 40 Gt/yr. (La Salle and Hepperly 2008)
Convesion of degraded farms to to management intensive grazing. Evaluated for 3 years out of 7, they sequestered 8 tons per hectare per year of carbon. If used worldwide on grazing lands it’s 98.5 gt CO2/yr.(Grasslands: 3,356,940,000 ha (FAO, 2010) x 29.36 = 98.5 gt CO2/yr)
Other systems are being evaluated and in process of peer review and publishing.
. GLOBAL SYMPOSIUM ON SOIL ORGANIC CARBON,Rome, Italy, 21-23 March2017
With the Sekem fields, the carbon was sequstered fast to start with then more slowly and a lot was sequestered as it was desert soil but was continuing to sequester soils 30 years later by comparing fields of different ages since they were desert
Video about the Sekem project:
AGAVE FARMING - POTENTIAL WORLDWIDE
This is another interesting idea from Mexico, using agave, a plant that can grow in very dry conditions, to make a kind of a silage that animals can eat.
This plant is traditionally grown for Tequilla in Mexico - an alcoholic drink. However this is wasteful of the plant itself. using less than half of the sugar and cellulose. It could be used for biofuels:
Agave for tequila and biofuels: an economic assessment and potential opportunities
However another new idea is to ferment it and use it for silage - fermented food for cattle.
This is good news for drylands in Mexico as well as other areas of the world. It is from Zamarripa, the farmers have found a low cost way to ferment the agave leaves into sillage by first chopping them up. They can then be interplanted with trees to make a forest that is able to grow on land with a long dry season.
It lets them use them as food for goats and sheep and they then make the roots into mescal eventually (alcoholic drink).
This system could potentially sequester up to around three quarters (74%) of Mexico's CO2 emissions as well.
The bountiful harvest of this regenerative, high-biomass, high carbon-sequestering system will eventually include not only extremely low-cost, nutritious animal silage, but also high-quality organic lamb, mutton, cheese, milk, aquamiel (agave sap), pulque (a mildly alcoholic beverage) and distilled agave liquor (mescal), all produced organically and biodynamically with no synthetic chemicals or pesticides whatsoever, at affordable prices, with excess agave biomass and fiber available for textiles, compost, biochar and construction materials.
Developing a native species/agroforestry/livestock system on 5 million to 10 million acres of land unsuitable for food crops in a large country like Mexico (which has 357 million acres of cropland and pastureland, much of which is degraded) could literally sequester 37% to 74% of the country’s net current fossil fuel emissions (current net emissions are 492m tons of CO2e).
Agave uses the CAM system of photosynthesis which is more efficient than the other methods, and also uses less water. It opens its stomata only at night and has shallow roots that take advantage of any rain and moisture as soon as it falls.
Agave americana for instance can produce 40 tons per hectare of cellulose, and Agave tequilina can produce 90 tons per hectare of stems and 30 tons per hectare of sugar per year. Details from this paper from the institute of Green Economy, if they got their figures right.
DEGRADED LAND AREA POTENTIAL
There are about 2 billion hectares of land worldwide that are degraded, suitable for restoration - an area larger than South America.
These systems are not likely to reach their full potential as they would require all farmers worldwide on those lands to adopt those systems.
However, if even 10% of degraded land was converted to these systems to enhance more CO2 sequestration potential it could contribute a significant part of the 40 Gt per year for climate restoration by 2050.
SO IS THIS POSSIBLE?
I leave it to you to think it over. For sure we have to aim for carbon zero as soon as possible, and carbon zero by 2050 seems a reasonable goal. However there do seem to be many methods by which we could aim higher (or lower in CO2 levels) than just carbon zero at a higher global temperature of 1.5 C above pre-industrial.
The calculations seem to be correct and many here are peer reviewed. It seems to be technologically feasible to return to 300 ppm by 2050, or perhaps later, by 2100, seems feasible. It is a question of the politics, finance, and impact assessments.
THERE ARE DISADVANTAGES OF GOING BACK TO PRE-INDUSTRIAL LEVELS OF CO2
We have a CO2 fertilization effect that is benefiting modern agriculture, do we want to reverse that and have crops with lower yields because of lower CO2 levels? We have already adapted to warmer climates in many places, do we want to go back to cooler climates? It would be a rather sudden reduction in temperature, e.g. for fruit trees in the US and trees grown for the first time in Iceland with species already selected for a warmer world. What about the new businesses that are starting up using the nearly ice free summer Arctic seas?
Also we have already averted our next ice age 1500 years from now. If we get back to 300 ppm by 2050 and continue reducing it, we may be leading our world to a new ice age within a millennium and a half.
This is one of the points made in “Trajectories of Earth in the anthropocene” - a much misunderstood and misreported paper. There are no timescales in this, which is a purely concept study. Most of their tipping points unfold over centuries to thousands of years.
But their main point was, we get to set the CO2 levels on Earth as a result of our own human actions. So - where is the best place to set it? This is one of their diagrams
:
There they say that we would notmally be heading towards an ice age in the blue loop. But instead we seem to be looping around in the smaller “Stabilized Earth” which is actually a rather good scenario to end up in.
If we stay well within 2 C, which is the ideal target of the Paris agreement, to stay within 1.5 C, then we are good for hundreds of thousands of years into the future, to have a stable temperature without the huge fluctuations of the ice ages.
If we go all the way back to 300 ppm we probably have not gone back far enough to risk a near future ice age - as in 1500 years from now - but if we continue down to well below 300 ppm we might well.
In a recent study the authors selected only the models that most accurately tracked the previous ice ages, and used that to study whether or not we are due to plunge into the next ice age. They found that if they ran the models with CO2 levels of 240 ppm, similar to the Halocene, then the next ice age would be as soon as 1500 years into the future.
But if they used the pre-industrial levels of CO2 of 280 ppm, then the next ice ages should be 50,000 and 90,000 years from now (with a possibility of a slowly approaching ice age 20,000 years from now). Just that extra 40 ppm made all the difference. They are unsure why we had more CO2 this time around. Perhaps human activity even in pre-industrial society was enough to raise the levels by 40 ppm, which isn't very much, or at least contributed to the levels.
They found that with 500 Gt of emissions, not far off what we have already reached, we may already have enough CO2 in the atmosphere to make a difference to the ice sheets over thousands of years. If it reaches 1000 GT then the chance of an ice age in the next 100,000 years is notably reduced and with 1500 GT of emissions then it is very unlikely that we get an ice age in the next 100,000 years. And with higher levels of emissions, then we will end the pattern of ice ages altogether. You can read it in full under Nature's sharing initiative if you click on the link " published in the journal Nature" in the article in the Guardian here: Fossil fuel burning 'postponing next ice age
It's not so bad at all to have prevented the next ice age. The climate is much more stable during the interglacials, while during ice ages then you can get dramatic changes of climate within decades. Also the Earth is more habitable for us during the interglacials.
I don't think we necessarily need to make this aim of 300 ppm our objective. Also if we do get back to 300 ppm, we might want to take measures to make sure it goes no lower (unless for some reason we want future generations to experience an ice age - but if they retain technology, they would be able toremove the CO2 easily enough if they wnated to)..
But knowing it can be done gives us more options for the future, whatever we decide.
SECTION ON SOME OF THESE IDEAS IN 2018 IPCC REPORT ON THE DIFFERENCE BETWEEN 1.5 AND 2 C
This is what it says
Several studies have either directly or indirectly explored the dependence of 1.5°C-consistent pathways on specific (sets of) mitigation and CDR technologies (Bauer et al., 2018; Grubler et al., 2018; Holz et al., 2018b; Kriegler et al., 2018a; Liu et al., 2018; Rogelj et al., 2018; Strefler et al., 2018b; van Vuuren et al., 2018). However, there are a few potentially disruptive technologies that are typically not yet well covered in IAMs and that have the potential to alter the shape of mitigation pathways beyond the ranges in the IAM-based literature. Those are also included in Supplementary Material 2.5 SM 1.2, . The configuration of carbon-neutral energy systems projected in mitigation pathways can vary widely, but they all share a substantial reliance on bioenergy under the assumption of effective land-use emissions control.
[bioenergy + land use emissions control]
There are other configurations with less reliance on bioenergy that are not yet comprehensively covered by global mitigation pathway modelling. One approach is to dramatically reduce and electrify energy demand for transportation and manufacturing to levels that make residual non-electric fuel use negligible or replaceable by limited amounts of electrolytic hydrogen. Such an approach is presented in a first-of-its kind low-energy-demand scenario (Grubler et al., 2018) which is part of this assessment.
[low energy demand]
Other approaches rely less on energy demand reductions, but employ cheap renewable electricity to push the boundaries of electrification in the industry and transport sectors (Breyer et al., 2017; Jacobson, 2017). In addition, these approaches deploy renewable-based Power-2-X (read: Power to “x”) technologies to substitute residual fossil-fuel use (Brynolf et al., 2018). An important element of carbon-neutral Power-2-X applications is the combination of hydrogen generated from renewable electricity and CO2 captured from the atmosphere (Zeman and Keith, 2008).
[Don’t reduce energy demand instead rely on cheap renewables electricity]
Alternatively, algae are considered as a bioenergy source with more limited implications for land use and agricultural systems than energy crops (Williams and Laurens, 2010; Walsh et al., 2016; Greene et al., 2017).
[Or use algae which don’t need so much land as energy crops]
Furthermore, a range of measures could radically reduce agricultural and land-use emissions and are not yet well-covered in IAM modelling. This includes plant-based proteins (Joshi and Kumar, 2015) and cultured meat (Post, 2012) with the potential to substitute for livestock products at much lower GHG footprints (Tuomisto and Teixeira de Mattos, 2011).
[or reduce agriculture and land use emissions e.g. using plant bsed meat substitutes]
Large-scale use of synthetic or algae-based proteins for animal feed could free pasture land for other uses (Madeira et al., 2017; Pikaar et al., 2018). Novel technologies such as methanogen inhibitors and vaccines (Wedlock et al., 2013; Hristov et al., 2015; Herrero et al., 2016; Subharat et al., 2016) as well as synthetic and biological nitrification inhibitors (Subbarao et al., 2013; Di and Cameron, 2016) could substantially reduce future non-CO2 emissions from agriculture if commercialized successfully.
[or use synthetic or algae-based proteins for animal feed and methanogen inhibitors (for methane burps from cows) and vaccines and synthetic and biological nitrificaton inhibitors.]
Enhancing carbon sequestration in soils (Paustian et al., 2016; Frank et al., 2017; Zomer et al., 2017) can provide the dual benefit of CDR and improved soil quality.
[Or enhanced carbon sequestration in soils -to improve soil quality and capture carbon]
A range of conservation, restoration and land management options can also increase terrestrial carbon uptake (Griscom et al., 2017).
[Or conservation, restoration and land management - e.g. reversing desertification]
In addition, the literature discusses CDR measures to permanently sequester atmospheric carbon in rocks (mineralization and enhanced weathering, see Chapter 4, Section 4.3.7) as well as carbon capture and usage in long-lived products like plastics and carbon fibres (Mazzotti et al., 2005; Hartmann et al., 2013).
[Or sequester in rocks through mineralization and advanced weathering, capture and use in long lived products like plastics and carbon fibres]
Progress in the understanding of the technical viability, economics and sustainability of these ways to achieve and maintain carbon neutral energy and land use can affect the characteristics, costs and feasibility of 1.5°C-consistent pathways significantly.
[Progress here can make big differences to the costs and feasibility of 1.5 C consistent pathways]
. Chapter2 see 2.3.1.2 Mitigation options in 1.5°C pathways, page 111 ff:
SUMMARY OF AR6 / WG3 CHAPTER 7
We currently emit 40 gigatons a year. But this will go down to just a few gigatons a year by 2050 just through the transition to renewables and decarbonizing a lot of industry
.
Many ways to do carbon dioxide removal
- might need these in 2nd half of century
to stay at zero emissions once we get there
Cross-Chapter Box 8, Figure 1: Carbon Dioxide Removal taxonomy
Methods are categorised based on removal process (grey shades) and storage medium (for which timescales of storage are given, yellow/brown shades). Main implementation options are included for each CDR method. Note that specific land-based implementation options can be associated with several CDR methods, e.g., agroforestry can support soil carbon sequestration and provide biomass for biochar or BECCS.
Here are some of the main points, I will summarize each section in bullet points.
. Climate Change 2022: Mitigation of Climate Change
First there’s huge carbon capture potential for land use changes, reducing food loss waste etc.
It’s clear we have plenty of potential here through to 2050. But these methods could saturate. .
enhanced soil management could remove 1.9 gigatons a year (0.4-6.8) ,
grasslands 1.0 gigatons a year (0.2-2.6)
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Critical assessment and conclusion.
In conclusion, there is medium confidence that enhanced soil carbon management in croplands has a global technical mitigation potential of 1.9 (0.4-6.8) gigatons per year, and in grasslands of 1.0 (0.2-2.6) gigatons per year, of which, 0.6 (04-0.9) and 0.9 (0.3-1.6) gigatons per year is estimated to be available at up to USD100 per ton of CO2 respectively. Regionally, soil carbon management in croplands and grasslands is feasible anywhere, but effectiveness can be limited in very dry regions, and for grasslands it is greatest in areas where degradation has occurred (e.g. by overgrazing) and soil organic carbon is depleted. Barriers to implementation include regional capacity for monitoring and verification (especially in developing countries), and more widely through concerns over saturation and permanence.
Improved management of the land, including forests, peatlands, coastal wetlands savannas and grasslands could remove or prevent 7.3 gigatons a year (3.9–13.1).
7-5
AFOLU = Agriculture, Forestry and Other Land Uses
Between 2020 and 2050, mitigation measures in forests and other natural ecosystems provide the largest share of the economic (up to USD100 tCO2-eq-1) AFOLU mitigation potential, followed by agriculture and demand-side measures (high confidence). In the global sectoral studies, the protection, improved management, and restoration of forests, peatlands, coastal wetlands, savannas and grasslands have the potential to reduce emissions and/or sequester 7.3 mean (3.9–13.1 range) gigatons per year .
Agriculture could remove 4.1 gigatons a year (1.7–6.7).
Agriculture provides the second largest share of the mitigation potential, with 4.1 (1.7–6.7) gigatons per year (up to USD100 per ton CO2) from cropland and grassland soil carbon management, agroforestry, use of biochar, improved rice cultivation, and livestock and nutrient management.
Diet change, reducing food waste, building with wood, and use of biochemicals and bio-textiles can remove 2.2 gigatons a year.
Demand-side measures including shifting to sustainable healthy diets, reducing food waste, and building with wood and biochemicals and bio-textiles have a mitigation potential of 2.2 (1.1–3.6) gigatons per year. Most mitigation options are available and ready to deploy. Emissions reductions can be unlocked relatively quickly, whereas CDR needs upfront investment. Sustainable intensification in agriculture, shifting diets, and reducing food waste could enhance efficiencies and reduce agricultural land needs, and are therefore critical for enabling supply-side measures such as reforestation, restoration, as well as decreasing CH4 and N2O emissions from agricultural production. In addition, emerging technologies (e.g., vaccines or inhibitors) have the potential to substantially increase CH4 mitigation potential beyond current estimates. AFOLU mitigation is not only relevant in countries with large land areas. Many smaller countries and regions, particularly with wetlands, have disproportionately high levels of AFOLU mitigation potential density. {7.4, 7.5}
Concerted, rapid and sustained effort by all stakeholders, from policy makers and investors to land owners and managers is a pre-requisite to achieving high levels of mitigation in the AFOLU sector (high confidence). To date USD 0.7 billion per year is estimated to have been spent on AFOLU itigation. This is well short of the more than USD400 billion per year that is estimated to be necessary to deliver the up to 30% of global mitigation effort envisaged in deep mitigation scenarios (medium confidence).
This estimate of the global funding requirement is smaller than current subsidies provided to agriculture and forestry. Making this funding available would require a change in flows of money and determination of who pays. A gradual redirection of existing agriculture and forestry subsidies would greatly advance mitigation.
7-14
Figure 7-3
Significant removals only happening in Europe so far and still not enough to ofset emissions from landuse change.
7-42
Most mitigation options are available and ready to deploy. Emissions reductions can be unlocked relatively quickly, whereas CDR need upfront investment to generate sequestration over time. The protection of natural ecosystems, carbon sequestration in agriculture, sustainable healthy diets and reduced food waste have especially high co-benefits and cost efficiency. Avoiding the conversion of carbon-rich primary peatlands, coastal wetlands and forests is particularly important as most carbon lost from those ecosystems are irrecoverable through restoration by the 2050 timeline of achieving net zero carbon emissions (Goldstein et al. 2020). Sustainable intensification, shifting diets, reducing food waste could enhance efficiencies and reduce agricultural land needs, and are therefore critical for enabling supply-side measures such as reduced deforestation, restoration, as well as reducing N2O and CH4emissions from agricultural production - as seen in the Illustrative Mitigation Pathway IMP-SP (Section 7.5.6). Although agriculture measures that reduce non-CO2, particularly of CH4, are important for near term emissions reductions, they have less economic potential due to costs. Demand-side measures may be able to deliver non-CO2 emissions reductions more cost efficiently.
Biochar could remove 2.6 gigatons a year (0.2–6.6) (a way of increasing the fertility of the soils by converting organic waste to charcoal) with 1.1. gigatons of that available at less than $100 per ton (0.3–1.8).
- Here though there’s upfront payment for the biochar it improves agricultural yields long term.
Biochar has significant mitigation potential through CDR and emissions reduction, and can also improve soil properties, enhancing productivity and resilience to climate change (medium agreement, robust evidence).
There is medium evidence that biochar has a technical potential of 2.6 (0.2–6.6) gigatons per year, of which 1.1 (0.3–1.8) gigatons per year is available up to USD100 per ton of CO2 . However mitigation and agronomic co-benefits depend strongly on biochar properties and the soil to which biochar is applied (strong agreement, robust evidence). While biochar could provide moderate to large mitigation potential, it is not yet included in IAMs, which has restricted comparison and integration with other CDR strategies.
They couldn’t assess the potential for regenerative agriculture - ways of doing agriculture that are built in to be carbon negative (see next section for an example: carbon negative cattle farming) as the literature isn’t extensive enough yet.
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Agroecology (AE) including Regenerative Agriculture (RA)
Despite absence of a universally accepted definition (see Annex I), RA is gaining increasing attention and shares principles of AE. Some descriptions include carbon sequestration as a specific aim (Elevitch et al. 2018). Few studies have assessed mitigation potential of RA at a system level (e.g. Colley et al. 2020). Like AE, it is likely that RA can contribute to mitigation, the extent to which is currently unclear and by its case-specific design, will vary (medium confidence)
Reducing food lost waste could save 2.1 gigatons a year (0.1–5.8)
Food Loss Waste (FLW)
Food loss and waste (FLW) refer to the edible parts of plants and animals produced for human consumption that are not ultimately consumed (UNEP 2021b). Food loss occurs through spoilage, spilling or other unintended consequences due to limitations in agricultural infrastructure, storage and packaging (Parfitt et al. 2010). Food waste typically takes place at the distribution (retail and food service) and consumption stages in the food supply chain and refers to food appropriate for human consumption that is discarded or left to spoil (HLPE 2014). Options that could reduce FLW include: investing in harvesting and post-harvesting technologies in developing countries, taxing and other incentives to reduce business and consumer level waste in developed countries, mandatory FLW reporting and reduction targets for large food businesses, regulation of unfair trading practices, and active marketing of cosmetically imperfect products
There is medium confidence that reduced FLW has large global technical mitigation potential of 2.1 (0.1–5.8) gigatons per year including savings in the full value chain and using GWP100 and a range of IPCC values for CH4 and N2O. Potentials at 3.7 (2.2–5.1) gigatons per year 15 are considered plausible. When accounting for diverted agricultural production only, the feasible potential is 0.5 (0.0–0.9) gigatons per year 16 .
Case studies
Regreening the Sahel, Northern Africa
More than 200 million trees have regenerated on more than 5 Mha in the Sahel (Sendzimir et al. 2011). The Maradi/Zinder region of Niger is the epicentre of experimentation and scale up. This vast geographic extent generates significant mitigation potential despite the relatively modest per unit area increase in carbon of about 0.4 Mg C per hectare per year
In addition to the carbon benefits, these agroforestry systems decrease erosion, provide animal fodder, recharge groundwater, generate nutrition and income benefits and act as safety nets for vulnerable rural households during climate and other shocks
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Limiting warming to likely 2C or below can result in large scale transformation of the land surface (high confidence) (Popp et al. 2017; Rogelj et al. 2018a,b; Brown et al. 2019; Roe et al. 2019). The scale of land transformation depends, inter alia, on the temperature goal and the mitigation options included (Popp et al. 2017; Rogelj et al. 2018a; IPCC 2019a).
Pathways with more demand-side mitigation options show less land transformation than those with more limited options (van Vuuren et al. 2018; Grubler et al. 2018; IPCC 2019a).
Most of these pathways show increases in forest cover, with an increase of 322 million ha (-67 to 890 million ha) in 2050 in 1.5°C pathways with no or limited overshoot, whereas bottom up models portray an economic potential of 300-500 million ha of additional forest (Chapter 7). Many IAM pathways also include large amounts of energy cropland area, to supply biomass for bioenergy and BECCS, with 199 (56-482) million ha in 2050 in 1.5°C pathways with no or limited overshoot. Large land transformations, such as afforestation/reforestation and widespread planting of energy crops, can have implications for biodiversity and sustainable development (see Section 3.7, Chapter 7 - Subsection 7.7.4, Chapter 12 - Section 12.5)
METHODS FOR THE SECOND HALF OF THIS CENTURY IF CARBON STOCKS SATURATE
In the long term in the second half of the century it may be more challenging to use methods that enhance vegetation and soil carbon stocks.
As we saw in this blog post some methods pay for themselves. Others are very low cost. For an example of a simple approach we could use today is to crush olivinge and spread it on beaches. Since it removes CO2 from teh oceans it reverses acidification too and is a very low impact way that is equivalent to carbon dioxide capture and removal that it just directly reduces the CO2 in the atmosphere.
To remove 2% of global emissions would cost $32 billion a year at $40 per ton for 0.8 gigatons. This is an amount the world could easily find if needs be as we work on other methods to refine them and bring them to maturity.
METHODS FOR THE SECOND HALF OF THIS CENTURY IF CARBON STOCKS SATURATE
In the long term in the second half of the century it may be more challenging to use methods that enhance vegetation and soil carbon stocks.
As we saw in this blog post some methods pay for themselves. Others are very low cost. For an example of a simple approach we could use today is to crush olivinge and spread it on beaches. Since it removes CO2 from teh oceans it reverses acidification too and is a very low impact way that is equivalent to carbon dioxide capture and removal that it just directly reduces the CO2 in the atmosphere.
To remove 2% of global emissions would cost $32 billion a year at $40 per ton for 0.8 gigatons. This is an amount the world could easily find if needs be as we work on other methods to refine them and bring them to maturity.
We MAY need methods like this in the second half of this century and beyond.
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In the very long term (latter part of the century and beyond), it will become more challenging to continue to enhance vegetation and soil carbon stocks, so that the associated carbon sinks could diminish or even become sources (high confidence) (IPCC 2019a; de Coninck et al. 2018) (WGI Chapter 5).
Sustainable forest management, including harvest and forest regeneration, can help to remediate and slow any decline in the forest carbon sink, for example by restoring degraded forest areas, and so go some way towards addressing the issue of sink saturation (IPCC 2019) (WGI Chapter 5; WGIII Chapter 7). The accumulated carbon resulting from mitigation options that enhance carbon sequestration (e.g., reforestation, soil carbon sequestration) is also at risk of future loss due to disturbances (e.g., fire, pests)
The giant kelp seaweed farming:
converting 9% of the oceans to macroalgal aquaculture could take up 19 GtCO2 in biomass, generate 12 Gt per annum of biogas, and the CO₂ produced by burning the biogas could be captured and sequestered
Research in progress, not yet known how long the carbon would remain in the deep ocean and what the additional impacts would be.
See: 12-52
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In the very long term (latter part of the century and beyond), it will become more challenging to continue to enhance vegetation and soil carbon stocks, so that the associated carbon sinks could diminish or even become sources (high confidence) (IPCC 2019a; de Coninck et al. 2018) (WGI Chapter 5).
Sustainable forest management, including harvest and forest regeneration, can help to remediate and slow any decline in the forest carbon sink, for example by restoring degraded forest areas, and so go some way towards addressing the issue of sink saturation (IPCC 2019) (WGI Chapter 5; WGIII Chapter 7). The accumulated carbon resulting from mitigation options that enhance carbon sequestration (e.g., reforestation, soil carbon sequestration) is also at risk of future loss due to disturbances (e.g., fire, pests)
12-52
Marine biomass CDR options Proposals have been made to grow macroalgae (Duarte et al., 2017) for BECCS (N‘Yeurt et al. 2012; Duarte et al. 2013; Chen et al., 2015), to sink cultured macroalgae into the deep sea, or to use marine algae for biochar (Roberts et al., 2015). Naturally growing sargassum has also been considered for these purposes (Bach et al., 2021). Froehlich et al. (2019) found a substantial area of the ocean (ca. 48 million km2 39 ) suitable for farming seaweed. N’Yeurt et al. (2012) suggested that converting 9% of the oceans to macroalgal aquaculture could take up 19 GtCO2 in biomass, generate 12 Gt per annum of biogas, and the CO₂ produced by burning the biogas could be captured and sequestered. Productivity of farmed macroalgae in the open ocean could potentially be enhanced through fertilizing via artificial upwelling (Fan et al., 2020) or through cultivation platforms that dive at night to access nutrient-rich waters below the, often nutrient-limited, surface ocean. If the biomass were sunk, it is unknown how long the carbon would remain in the deep ocean and what the additional impacts would be. Research and development on macroalgae cultivation and use is currently underway in multiple parts of the world, though not necessarily directly focused on CDR.
They go into much more detail on many other methods in chapter 12. We covered some of them already but there are many more. I thought I’d use just one as an example as it is reasonably mature, we could do it already and seems scaleable with no real issues likely and directly removes CO2 from the atmosphere without regional effects on climate. Each one separately can be scaled up to remove up to nearly 100 gigatons a year so would be enough for any carbon dioxide removal we wish to do just by itself.
enhanced weathering, adding crushed rock to croplands can remove tens of gigatons a year - mining rocks that naturally absorb CO2 and crushing them so they absorb them faster - could take up tens of gigatons a year (in tropics, one estimate 88.1 gigatons, for basalt crushed and added to croplands, and a total of 95 gigatons a year) (12.3.1.2 Enhanced weathering)
Ocean alkalinity enhancement is a similar idea but pouring the crushed rock into the sea, it also reveseses acidification and could take up between 1 and 100 gigatones a year (12.3.1.3 Ocean-based methods)
This takes up CO2 from seawater which reduces the acidity of the oceans directly, and that then also makes the oceans more able to take up CO2 from the atmosphere and so offsets the CO2. The risks and impacts are mainly to do with how the marine ecosystems respond, and depends on how much you add and which minerals you use, so that would need to be studied but the corals especially would benefit from reversing acidification.
Discussed in IPCC / AR6 / WG3 pages 12-49 to 12-51. Now also as a separate document 1268 to 1271 of Chapter 12: Cross-sectoral Perspectives
Also covers two other methods, electrochemical processing of seawater, and making synthetic alkaline materials.
QUOTE CDR through ‘ocean alkalinity enhancement’ or ‘artificial ocean alkalinisation’ (Renforth and Henderson 2017) can be based on:
(i) the dissolution of natural alkaline minerals that are added directly to the ocean or coastal environments;
(ii) the dissolution of such minerals upstream from the ocean (e.g., enhanced weathering, Section 12.3.1.2);
(iii) the addition of synthetic alkaline materials directly to the ocean or upstream; and
(iv) electrochemical processing of seawater.
In the case of (ii), minerals are dissolved on land and the dissolution products are conveyed to the ocean through runoff and river flow. These processes result in chemical transformation of CO2 and sequestration as bicarbonate and carbonate ions (HCO 3–, CO 3 2–) in the ocean.
Page 1270 of Chapter 12: Cross-sectoral Perspectives
Methods include adding olivine sand to coastal areas like the green Papakolea Beach near the southern tip of Hawaii Island Olivine Sand - Sandatlas
Enhanced weathering of silicate minerals such as olivine could add alkalinity to the ocean, for example, by placing olivine sand in coastal areas
Page 1270 of Chapter 12: Cross-sectoral Perspectives
I don't know if they'd add enough sand to make the beaches noticeably green.
Other methods include getting ships to drop slaked lime into the sea, and electrochemical methods.
The cost for the olivine sand approach is about $20 to $40 per ton.
Any of these sea alkalinity reversing methods can store 1 to 100 gigatonnes a year. If we need to offset, say, 2% of current emissions in addition to what we can do by other methods that's 2% of 40 gigatonnes or 0.8 gigatonnnes which at $40 per ton would cost the world:
$32 billion a year to add green sand to beaches in coastal areas around the world.
E.g. suppose every country with a GDP of more than $2 trillion a year (ten of them, total GDP $67.4 trillion) contributed 1/2000th of their GDP, so they pay between $1 billion a year for Italy ranging up to just short of $13 billion a year for the USA that would pay for the world to offset 2% of current emissions in the second half of the century.
. The Top 25 Economies in the World
If it was spread over the entire economy of the world at over $100 trillion a year each country would need to contribute 1/3000th of its GDP, not that much different since so much of the global economy is in the top 10 countries with $2 trillion a year GDP or more.
Not saying this is how we do it. There would be many ways to find the funding. Some of the other solutions pay for themselves and even turn a profit and may be better. But it's to show this isn't an insurmountable problem.
A non profit is testing the idea in a cove in an undisclosed carribean island. They would source the olivine locally and they think they can do it for $10 per ton of CO2 which would make the global cost for removing 0.8 gigatonnes only $8 billion.
ever-been-to-a-green-sand-beach-the-newest-geohack-to-fight-climate-change
I recommend reading chapter 12 for many other options not covered in this blog post.
COULD BEEF FARMING BECOME CARBON NEGATIVE IN THE US THROUGH ADAPTIVE MULTI-PADDOCK SYSTEMS?
[Relevant to soil sequestration[
There is a lot of potential for soil sequestration in well managed grassland.
It's early stage research but if farmers can do best practice to manage the grassland to sequester lots of carbon it could potentially be carbon negative.
The US beef production currently emits 63.3 megatons of CO2 equivalent per year. This is based mainly on feeding maize to cattle (their scenario A). By changing to grass finished beef (scenario B) they achieve the same amount of meat produced but with many benefits to the soil, water etc because they spread the manure over larger areas naturally, grassland can be seeded with a mix including nitrogen fixing plants such as clover so that they don’t need nitrogen fertilizerss. and well managed grazing is good for birds, pollinators, fish and microbes.
To do this they would need to include some of the Conservation Reserve Program which pays farmers to set aside land from agriculture for 15 years at a time which benefit from disturbance.
. Conservation Reserve Program
If they do this then depending on how the grass is managed, the emissions can be similar to feeding them grain ,but with the right management system can even be carbon negative. It could sequester -3.59 tons per hectare per year carbon accumulation
QUOTE The soil C estimates for Scenarios A [Fed maize] and B [Grass finished] come from Sanford (2014), a 20-yr randomized and replicated experiment in southern Wisconsin showing losses of soil C from all annual grain systems at an average rate of ∼250 kg C ha–1 yr–1 (Scenario A) while rotationally grazed pastures gained slightly in surface 30 cm but lost C from 30 to 100 cm so that on net they were unchanged over 20 years.
QUOTE However, other reviews reported modest soil C gains in annual crops using no-till (Blanco-Canqui, 2021) and cover crops (Jian et al., 2020), so I explored a range of ecosystem C balance outcomes when varying the soil C parameter (Table 2). Similarly, recent studies of managed grazing have reported significant (320 kg C ha−1 yr−1; Becker et al., 2022) to moderate (840 kg C ha−1 yr−1; Franzluebbers, 2010) to very high (~3,590 kg C ha–1 yr–1; Stanley et al., 2018) accumulations of soil C under well-managed grazed pastures. The value of soil C increase making Scenario B net zero was ∼1,630 kg C ha–1 yr–1, while the Stanley et al. (2018) soil C change resulted in a system C balance equivalent to taking ∼23 coal-fired power plants offline!
That very high figure of -3.59 tons per hectare per year carbon accumulation, that could make it carbon negative is based on a method called adaptive multi-paddock.
The idea is to have large numbers of animals in a small space and then move them around. They graze the grass very hard for a short time then the grass is let to grow and this sequesters the most carbon.
They don't have set schedules. Rather they mimic what a herd of bison would do. The herd stays in one spot until it's eaten most of the grass then moves on.
So they might have four paddocks and they keep the cows in a paddock until they have grazed all the grass, then they move them to the next paddock and keep doing that round and round moving to the next paddock as they finish the previous one.
This sequesters much more carbon than the same number of cows grazing one large field all year round. This sequesters the most carbon.
QUOTE Some literature has identified beneficial ecosystem services resulting from the adoption of a carefully managed system known as adaptive multi-paddock (AMP) grazing. This approach applies an adaptive strategy that incorporates short grazing intervals with relatively high animal stocking densities, which are designed to allow plant recovery, promoting optimal plant communities and protecting soils
Method described here and graphic from here
:
. AMP Grazing | Standard Soil |
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