Natural carbon sequestration to offset the thawing permafrost

If your not familiar with why climate change is the most pressing issue humanity as ever faced then please read this first.
There are 2 related issues in the Arctic. One is the release of carbon from the sub-sea of the Arctic ocean that is dealt with in this article. The other is the release of carbon from the permafrost which is what this article deals with.

What is the problem;

World-wide, permafrost contains 1700 billion tons of organic material equalling almost half of all organic material in all soils.[5] This pool was built up over thousands of years and is only slowly degraded under the cold conditions in the Arctic. The amount of carbon sequestered in permafrost is four times the carbon that has been released to the atmosphere due to human activities in modern time.[28] (link)

Should a substantial amount of the carbon enter the atmosphere, it would accelerate planetary warming. A significant proportion will emerge as methane, which is produced when the breakdown occurs in lakes or wetlands. Although it does not remain in the atmosphere for long, methane traps more of the sun’s heat. The Arctic region is one of the many natural sources of the greenhouse gas methane.[37] Global warming accelerates its release, due to both release of methane from existing stores, and from methanogenesis in rotting biomass.[38] Large quantities of methane are stored in the Arctic in natural gas deposits, permafrost, and as submarine clathrates. Permafrost and clathrates degrade on warming, thus large releases of methane from these sources may arise as a result of global warming.[39][40] (link)

The majority of permafrost carbon is deep. If we were to decrease emissions, use the tools nature has given us, large amounts of carbon would be sequestered and the current rate of warming would slow. That would mean the releases from the permafrost would slow.

Currently we have a situation where during summer the top layer is heated dramatically, Arctic winters are increasing at a rate of 0.34C per decade. So with the current annual average temperature of -5C we have precious little time. It will be some time before the deeper permafrost can thaw, but every decade that more carbon is released into the atmosphere the warming rate will increase.

When, not if, the permafrost melts the organic matter will be converted into CO2 and methane. The challenge is to convert this organic matter into a form that can be sequestered. There are a number of natural mechanisms that can be used to achieve this. Nature gives us the tools, why we don't we use them?

First how much carbon is there? From this CSIRO article;

Involving collaboration between scientists from Australia, Russia, the US, the UK, Canada and Europe the three-year study concluded that accounting for carbon stored deep in the permafrost more than doubles – to more than 1500 billion tonnes – previous estimates of the world’s high-latitude carbon inventory.

It is not possible for all of that carbon to be released, from here;

The amount of carbon that will be released from warming conditions depends on depth of thaw, carbon content within the thawed soil, and physical changes to the environment.^[7] The likelihood of the entire carbon pool mobilizing and entering the atmosphere is low despite the large volumes stored in the soil. Although temperatures are projected to rise, it does not imply complete loss of permafrost and mobilization of the entire carbon pool. Much of the ground underlain by permafrost will remain frozen even if warming temperatures increase the thaw depth or increase thermokarsting and permafrost degradation.^[4]

How much will be released per year, is at best a guess but current estimates are;

This corresponds to an average annual emission rate of 4-8 billion tons of CO₂ equivalents in the period 2011-2040 

Carbon dioxide equivalent” or “CO₂e” is a term for describing different greenhouse gases in a common unit. For any quantity and type of greenhouse gas, CO₂e signifies the amount of CO₂ which would have the equivalent global warming impact.

Best case 4, worst case, 8 billion tons of CO2e. Billions tonnes is written as Gt. Assuming the carbon is released as methane (CH4), and methane has a ratio of 1 to 25 CO2e. So this represents 8 /25 = 0.3 Gt CH4. 75% of the weight of methane is carbon so the final emission estimate is for 0.24 Gt of carbon emitted per year.

In this article I will attempt to describe the various ways in which carbon can be sequestered (stored) naturally and rapidly. This is not a purely scientific exercise with little practical value. There are simple changes we can make in our day to day lives that can dramatically affect the atmospheric carbon. These are dealt with at the end of the article.

Soil carbon

From the excellent booklet. 

If the bulk density of the soil is known, it is a simple matter to relate % soil carbon to tonnes of carbon per hectare. Most Australian soils have a bulk density of between 1.0 and 1.8 grams/cm3, or expressed in another way between 1.0 and 1.8 tonnes per cubic metre. In the following example we will assume that the bulk density is 1.4 grams/cm3 or 1.4 tonnes/per cubic metre. (Note: bulk density can vary with depth, so we will assume this is an average for the 0 to 30 cm range).
This example demonstrates just how much carbon is stored in the soil at even a relatively low percentage of soil organic carbon. It also demonstrates that if soil carbon levels were improved, a significant amount of carbon dioxide could be taken from the atmosphere and stored in the soil, for a small increase in soil carbon.
In the previous example, suppose the soil carbon was increased from 2.0% to 3.0% (an increase of 1%). The extra carbon stored in this soil to a depth of 30 cm would be 42 tonnes per hectare.

So the world has 12 billion hectares of arable land, improving that soil by 1% would result in a sequestration of 504 billion tonnes of carbon. To put that in perspective, in a simplistic world, that would neutralize the entire permafrost problem in 3 decades if we achieved a 1% improvement in all soil every decade. Keep in mind that that estimate was only for the first 30cm of soil depth. Carbon has been found at significant levels down to 1.1m. However, the rate of sequestering would fall off quickly as more carbon was accumulated in the soil due to saturation.

The greatest gains would be in the most impoverished soil.

Of the 41 samples analysed, Strzelecki (1845) found …

The top 10 soils in the high productivity group had organic matter levels ranging from 11% to 37.75% (average 20%). The lowest ranking 10 soils in the low productivity group had organic matter levels ranging from 2.2% to 5.0% (average 3.72%) The soils with the highest organic matter levels also had the highest moisture holding capacity, with an 18-fold difference in capacity to hold moisture between the lowest and the highest (Strzelecki 1845).

Strzelecki’s data indicate that organic matter levels in the early settlement period were around five to ten times higher than in many soils today. The soil test data from Strzelecki is consistent with the writings of first settlers, who described soils in the early settlement period as soft, spongy and absorbent. The 1840s journal of George Augustus Robinson for example, contains numerous references to the extremely fertile and productive soils encountered by pastoralists in the mid-1800s (Presland 1970)

On a practical level. The best way to improve soil locally is to take vermicast liquid (worm pee), aerate it for 3 days, or until it foams. Then spray it onto the soil preferably late in the day. That rebuilds the soil ecosystem. If that was done with bamboo biochar dug into the soil and inoculated plants the gains are large. An article on how to inoculate your plants is here. Another permaculture one here.

The gains in improving degraded soil would be higher than that of high performing soil. Therefore, it would follow that the place with the greatest need, and creating the best gains, would be Australia.

Hemp

From this article;

... one tonne of harvested stem contains:

0.7 tonnes of cellulose (45% Carbon)
0.22 tonnes of hemicellulose (48% Carbon)
0.06 tonnes of lignin (40% Carbon)
It follows that every tonne of industrial hemp stems contains 0.445 tonnes Carbon absorbed from the atmosphere (44.46% of stem dry weight).
Converting Carbon to CO2 (12T of C equals 44T of CO2(IPCC)), that represents 1.63 tonnes of CO2 absorption per tonne of UK Hemp stem harvested. On a land use basis, using Hemcore’s yield averages (5.5 to 8 T/ha), this represents 8.9 to 13.4 tonnes of CO2 absorption per hectare of UK Hemp Cultivation.
For the purposes estimation, we use an average figure of 10T/ha of CO2 absorption, a figure we hold to be a reasonably conservative estimate. This is used to predict carbon yields, but CO2 offsets will be based on dry weight yields as measured at the weighbridge.
The roots and leaf mulch (not including the hard to measure fibrous root material) left in situ represented approximately 20% of the mass of the harvested material in HGS’ initial field trials. The resulting Carbon content absorbed but remaining in the soil, will therefore be approximately 0.084 tonnes per tonne of harvested material. (42% w/w) (5).
Using Hemcore’s UK yield estimates (5.5 – 8 T/ha) this represents 0.46 to 0.67 tonnes of Carbon per hectare (UK) absorbed but left in situ after Hemp cultivation.
That represents 1.67 to 2.46 T/ha of CO2 absorbed but left in situ per hectare of UK Hemp Cultivation.
Final figures after allowing 16% moisture (Atmospheric ‘dry’ weight) are as follows:
CO2 Absorbed per tonne of hemp stem 1.37t
CO2 Absorbed per hectare (stem) (UK) 7.47 to 11.25t
CO2 Absorbed per hectare (root and leaf) UK) 1.40 to 2.06t

Its uses 

Let's start by saying that if you choose to smoke it you are at risk of harming yourself. With that out of the way, the industrial uses of hemp are so many that I would defer to the wikipedia article rather than repeating it all here.

In modern times hemp is used for industrial purposes including paper, textiles, clothing, biodegradable plastics, construction (as with Hempcrete and insulation), body products, health food and bio-fuel.

The benefits

Hemp can be grown on existing agricultural land (unlike most forestry projects), and can be included as part of a farm’s crop rotation with positive effects on overall yields of follow on crops. This, along with super versatility in diverse soil conditions and climates, makes hemp cultivation a viable and genuine potential large scale contributor to GHG mitigation.

Human excretia

On average every day you produce 227 grams of faeces. Of that 40 - 50% is carbon. That is approximately 91 grams of carbon. It adds to 33kg per year per person. There are 7 billion of us, that means 231 million tonnes of carbon in our waste every year. Remembering the thawing permafrost will emit 0.24 Gt which is 240 million tonnes. So we would virtually be at a balance. It is time that we got serious about using the sludge from waste treatment plants to treat our soil. 

Composting toilets are a form of carbon sequestration.

Azolla

Azolla is a symbiotic plant that some 50 million years ago caused 2850ppm CO2 to be removed from the atmosphere. Azolla's carbon fixing rate is 1.86 tonnes CO2 in 1 ha per year (link).

A study of Arctic Paleoclimatology reported that Azolla may have had a significant role in reversing an increase in greenhouse effect that occurred 55 million years ago that caused the region around the north pole to turn into a hot, tropical environment. This research conducted by the Institute of Environmental Biology at Utrecht University claims that massive patches of Azolla growing on the (then) freshwater surface of the Arctic Ocean consumed enough carbon dioxide from the atmosphere for the global greenhouse effect to decline, eventually causing the formation of Ice sheets in Antarctica and the current "Icehouse period" which we are still in. This theory has been termed the Azolla event.(link)

The reason it is so effective at removing CO2 is that it reproduces at such a fast rate. First let's do the math;

• Total surface area in the world's largest reservoirs is 28,806km^2. That is 2.9 million ha. Not all of that would be productive, but that list is only the largest reservoirs. At 1.86 tonnes per ha that means 2.9 x 10^6 x 1.86 = 5.4 million tonnes sequestered per year.
• The Black Sea has a net positive inflow of freshwater. Given the problems of nitrogen and phosphorus in the black sea it would seem to be a good candidate as an azolla sink. Its area is 43.6 million ha. The carbon sequestered would be 81.2 million tonnes per year.
• The great lakes have 24.4 million ha. The carbon sequestered would be 45.4 million tonnes per year.
• The Caspian sea has an area of 37.1 million ha. The carbon sequestered would be 66.8 million tonnes per year.

Not all these sites may be suitable due to climate. If it was feasible total sequestration would be 198.8m tonnes per year, again close to a balance with the permafrost emisssions. The benefits would be cleaner water and an entirely new industry producing a range of products (below).

Given that the average person in the US produces 18 CO2 tonnes per year the scope of the problem is huge. 
However, azolla is much more than a simple tool for carbon sequestration. It has a lot of very practical uses and is a fascinating plant in its own right. 

Animal feed

It is palatable to: molluscs, ducks, chickens, pigs, cows, goats, sheep and rabbits (and probably lots of others too)

...azolla is finding increasing use for sustainable production of livestock feed.^[17] Azolla is rich in proteins, essential amino acids, vitamins and minerals. describe feeding azolla to , chickens and egg production of layers, as compared to conventional feed. OneFAO study describes how azolla integrates into a tropical biomass agricultural system, reducing the need for inputs.^[18]Azolla has also been suggested as a food stuff for human consumption. However, no long term studies of the healthiness of eating Azolla have been made on humans.^[19]

The pressing question is why can it not be used for human consumption? If it could, it would change the agricultural landscape. The use of azolla in recipes appears to be limited to a small number of researchers.
From this site;

Azolla is rich in essential amino acids, proteins, vitamins and minerals and can therefore be advantageously used for animal fodder. Humans can also eat the plant; it tastes a bit like lettuce and is very healthy and nutritious. Azolla is sold in some health food stores in dried and powdered form and can easily be eaten every day as part of the salad. 

Some people are certainly getting on-board;

There is a 42-page article in the journal of Economic Botany #34 (2) 1980 pgs 111-153. There it is mentioned as a green manure, fish food and animal food including pigs. It also helps to purify water, is used in soap production and chewed to ease a sore throat. However, on page 144 it says:
"Bui* (1966) implied that with suitable processing Azolla could become a good source of human food. Dr. P. K. Singh** (personal communicatioin) wrote from Cuttack, India, that he has eaten Azolla regularly in several fried preparations; he reports that these preparations are tasty and do not cause digestive difficulties. He was taking steps to popularize the cultivation of Azolla in small trays for human consumption."
*Bui Huy Dap. 1966. Planting and cultivation of spring rice. Khoa Hoc Ky Thuat Nong Nghiop(Agricultural Science and Technology) 59: 645-653.1967. Some characteristic features of rice growing in Vietnam. Vietnamese Studies 13,Agricultural Problems 9 Rice. 2: 67-73 9 9 1971. Agronomic research. Vietnamese Studies 27, Agricultural Problems, Some TechnicalAspects 3: 73-88. 9 1976. The xuan (spring) rice as revolutionary factor in the rice production in North Vietnam 9Sel'Skokhoziastvennia Biologiia (Moscow) I l: 299-303., and Tan Nhu Nguyen. 1976. Practice of Azolla fertilization in Vietnam. Unpublished IRRIMemo based on visit to IRRI between April 15-24.
**Singh, P. K. 1977a. Multiplication and utilization of fern "'Azolla'" containing nitrogen-fixing algalsymbiont a green manure in rice cultivation. !1 Rizo 26:125-137.1977b. Azolla plants as fertilizer and feed. Indian Farming. 27: 19-22.1977c. The use of Azolla pinnata as a green manure for rice. Int. Rice Res. Newslett. 2/77.p. 7.1977d. Azolla fern plant-rice fertilizer & chicken feed. Kerala Karshakan 26: 5-6.

Fertilizer

The nitrogen-fixing capability of Azolla has led to Azolla being widely used as a biofertiliser, especially in parts of southeast Asia. Indeed, the plant has been used to bolster agricultural productivity in China for over a thousand years. When ricepaddies are flooded in the spring, they can be inoculated with Azolla, which then quickly multiplies to cover the water, suppressing weeds. The rotting plant material releases nitrogen to the rice plants, providing up to nine tonnes of protein per hectare per year.[8] (link)

This makes it a great input to worm farms and compost piles.

Prevents algal blooms in dams

Azolla is a nutrient feeder and prevents Algal blooms in farm dams as a result, keeping water more usable for stock. This is a much more important point than it would first appear. The implication is that using azolla to clean water catchment areas could prevent Algal blooms like the one in Ohio.

Grey water 

The main limiting factors on Azolla growth are salt, temperature and phosphorus. Phosphorus is plentiful in grey water. Making Azolla a perfect companion for cleaning grey water prior to its use in other areas. This site has a lot of useful information on practical applications. It removes BPA a toxic organic pollutant.

It is concluded that Azolla able remove BPA by Phytodegradation from the aqueous solutions. Since conventional methods of BPA removal need to high cost and energy, phytoremediation by Azolla as a natural treatment system can decrease those issues and it can be a useful and beneficial method to removal of BPA.(link)

It can remediate diesel polluted soil

In laboratory experiments, a consortium composed of A. pinnata-derived bacteria displayed dense growth in a 4% diesel-containing mineral salts medium and was found to lower the fluorescence from aromatic compounds by approximately 50% after 19 d. (BIODEGRADATION OF DIESEL FUEL BY AN AZOLLA-DERIVED BACTERIAL CONSORTIUM Michael F. Cohen,1 Jolene Williams,2 and Hideo Yamasaki1,3,*)

Biochar

It seems little research has been performed on converting azolla to biochar.

Reclamation of Saline Soils

From this research;

Although, Azolla is relatively sensitive to salt, cultivation in saline environment for a period of two consecutive years decreased salt content from 0.35-0.15 and desalinate rate (71.4%) was 1.8 times faster than through water leaching and 2.1 times faster than Sesbania and also reduced the electrical conductivity, pH of acidic soil and increased calcium content of soil

 70 Waseem Raja et al./ International Journal of Research in Biological Sciences 2012; 2(2): 68-72 conductivity, pH of acidic soil and increased calcium content of soil

Biodegradable plastic

Could it also be used to make bioplastic (link)? There is an existing patent for exactly that process (Macrophyte-based bioplasticWO 2013029018 A1)

Bamboo

Bamboo is the world's fastest growing plant. (Azolla is a symbiotic organism so doesn't count here). The implications are enormous. A lot of the information from this site is so appropriate that I will reproduce it verbatim;

One species of bamboo, the guadua angustifolia, found in Venezuela, Ecuador, and Colombia, has been shown to grow up to 25 meters in height and 22 centimeters in diameter, with each plant weighing up to 100 kilograms (Rojas de Sánchez, 2004). This doesn’t match the stature of many trees, but it is still big enough to be significant. It is not all about size, however. How fast a plant grows has a part in determining how much CO2 it can absorb in a given time. In this respect, bamboo wins hands-down: it grows faster than many trees, growing up to 1.2 meters per day. In fact, bamboo holds the Guinness World Record for the world’s fastest growing plant.  

 ...

 Ricardo Rojas Quiroga—an environmental engineering student at the Universidad Nuestra Señora de La Paz—studied Guadua angustifolia, a species of bamboo that grows in the Carrasco National Park of Bolivia. He measured the density and masses of bamboo plants in the forest, estimating the amount of carbon stored per hectare. Rojas concluded that, in addition to forming part of one of the most biodiverse ecosystems in the world, each hectare of the bamboo forest of Carrasco National Park stores levels of carbon comparable to some large tree species such as Chinese fir and oak. This finding is consistent with that of many previous studies, a review of which can be found in this 2010 report by INBAR. ... China has a native giant species of bamboo called Moso bamboo.   

The INBAR 2010 article actually states the carbon sequestration abilities at 150 t/ha over a 10 year period in a managed bamboo plantation. It is important distinction that natural bamboo forests do not work this way. It is only when the bamboo is harvested at 5 year intervals (species and location dependent) that the levels of sequestering can be achieved.

When bamboo is harvested and not dried typically that carbon is sequestered for 80 years under normal use, however artifacts have been dug up that date back to 2,200BC, which incidentally was the world's first timetables written on bamboo. There is an incredible diversity in the uses of bamboo. 



Bamboo can be used for products  from building, to food, utensils to medicine, clothing to musical instruments, even biochar and charcoal fuels. This is exactly what we need right now. A fast growing plant, that demands to be pruned and it's uses vary from carbon neutral to a natural sequestration. Usually a bamboo plantation can be harvested within 3 years of planting, as against decades for traditional trees.

How could this be applied to the permafrost problem. There are a large number of bamboo species (more here) that are cold climate hardy. Most of the cold growing varieties are running types, normally considered invasive. The invasiveness can be managed by digging trenches around plantations. Shoots extending into the trenches are pruned. That means it is a viable plantation crop for higher latitudes. It would be a matter of balancing cold hardiness with size to find a suitable species for a financial return. In addition to that is the matter of stabilizing the soil structure to minimize erosion in the thawing permafrost, for that purpose, any species that could handle the temperatures would be appropriate. Siberian bamboo (Miscanthus sacchariflorus), while not strictly a bamboo, could be encouraged.

Of course standard bamboo is not likely to grow in the Arctic circle anytime soon, but if things continue the way they are that might not be out of the question.

Lets do the math with Moso bamboo;
there is a worst case 0.24 Gt of emissions of carbon.
A hectare of bamboo can sequester 150 tonnes of carbon over a 10 year period. So we are averaging 1.5 tonnes per year.
So that would mean 0.24Gt / 1.5t per ha/yr = 0.16 billion ha/yrs. That figure is now our constant. Using that constant we can now determine how quickly (inverse to space) we want to sequester carbon in Bamboo.

There are 14m ha currently in production between China and India.
So we have;
(0.16 * 10^9 ha/yrs) / 14 * 10^6 ha = 11.4 years to reclaim the annual emissions. So 11 years is too long, anything over 1 year will mean an accumulation of atmospheric carbon. 
For a carbon neutral balance we need 0.16 billion ha of bamboo plantations. In 2008 there was approximately 12 billion hectares of productive land. That is, 1.3% of all farmland on the face of the Earth would have to be used. Given the uses of bamboo, that is actually not that bad.

So we need to fund Bamboo plantations both in cold climate areas and in other parts of the world. The way to do this is simple, and it is something everyone can participate in. Buy bamboo products. Every product you buy, from nappies to kitchen counter tops, see if there is a bamboo derived product available.

There is a caveat. Carbon may be released from permafrost as CO2, or CH4. Limited studies have demonstrated that particular species of trees (pine, spruce and birch) do actually absorb CH4 which is fortunate as those trees are found in Boreal forests. However, little is known about the absorption of CH4 into bamboo leaves. Without further studies, Bamboo would then seem only to deal with the CO2 problem. Once converted to biochar however, it can directly sequester methane into the soil (see Biochar).

Biochar

Adding Bamboo Biochar to soils increases the soils ability to sequester CH4 from the atmosphere. Could you apply biochar to the soil to trap the CH4 methane emitting from the permafrost?

When you have water logged soils that are generating methane they have methanogenic communities of bacteria. It's the bacteria that generate the methane. This study demonstrated that Bamboo Biochar could cut CH4 emissions from water logged soils by 50%, but the conclusion was that straw biochar was actually better for the job at 90%;

... when soils were amended with biochar, CH4 emissions were reduced. CH4 emissions from the paddy soil amended with BC and SC at high rate were reduced by 51.1% and 91.2%, respectively, compared with those without biochar. Methanogenic activity in the paddy soil decreased with increasing rates of biochar, whereas no differences in denaturing gradient gel electrophoresis patterns were observed. CO2 emission from the waterlogged paddy soil was also reduced in the biochar treatments.

It also reduces entric fermentation methane from this study. 

Twelve local “Yellow” cattle with initial live weight ranging from 80 to 100 kg were assigned in a completely randomized block design to a 2*2 factorial arrangement of four treatments with three replications.  

Live weight gain was increased 25% by adding biochar to the diet DM and tended to be decreased when nitrate replaced urea as the source of NPN. DM feed conversion was improved by biochar and by urea replacing nitrate. DM feed intake was not affected by supplementation with biochar nor by the NPN source. Both biochar and nitrate reduced methane production by 22 and 29%, respectively, the effects being additive (41% reduction) for the combination of biochar and nitrate.

How would this work for permafrost areas? Trapping the CH4 at the point of emission would be ideal, however, digging in biochar throughout massive areas of Siberia would be a great challenge. It would seem better then to convert bamboo into biochar where it is grown and then distribute the biochar as a soil conditioner to farms. The soil would then act as a sink for the methane generated from the permafrost.

Mushrooms

Don't underestimate the humble mushroom, they were here first. 1.3 billion years ago they were the first land organism.

mycorrhizal fungi, can sequester carbon in the soil. This is important because carbon stored in soil over long periods can help to offset the release of greenhouse gases to the atmosphere. Most fungal species act as decomposers that elicit a net release of CO₂ to the atmosphere, but mycorrhizal fungi could be a notable exception. (link)

Fungi are simply amazing. Mycorrhizal fungi will form highways in the soil. Those highways can transfer nutrients and carbon to trees. The scale of fungi activity can be significant representing 50-70% of stored carbon in a forest.

Boreal forest soils function as a terrestrial net sink in the global carbon cycle. The prevailing dogma has focused on aboveground plant litter as a principal source of soil organic matter. Using 14C bomb-carbon modeling, we show that 50 to 70% of stored carbon in a chronosequence of boreal forested islands derives from roots and root-associated microorganisms. Fungal biomarkers indicate impaired degradation and preservation of fungal residues in late successional forests. Furthermore, 454 pyrosequencing of molecular barcodes, in conjunction with stable isotope analyses, highlights root-associated fungi as important regulators of ecosystem carbon dynamics. Our results suggest an alternative mechanism for the accumulation of organic matter in boreal forests during succession in the long-term absence of disturbance. (link)

Not only were fungi the first land based organism, they are also the biggest.

That's right you are looking at it. It's right there, beneath the soil.

A mushroom of this type in the Malheur National Forest in the Blue Mountains of eastern Oregon, U.S. was found to be the largest fungal colony in the world, spanning 8.9 km² (2,200 acres) of area.[203][204] This organism is estimated to be 2400 years old. The fungus was written about in the April 2003 issue of the Canadian Journal of Forest Research. While an accurate estimate has not been made, the total weight of the colony may be as much as 605 tons. If this colony is considered a single organism, then it is the largest known organism in the world by area, and rivals the aspen grove "Pando" as the known organism with the highest living biomass. (link)

There is simply no other practical natural solution that could compare with this. The question then is, could this be used with bamboo? The conclusion from this study was Yes;

Thus, the results showed that utilization of effective AM fungi can enhance the productivity of bamboo.

You cannot miss this video.

TED video by Paul Stamets

What is required is tree planting and soil inoculation with spores. The species of tree required? Those that already exist in Boreal forests. 

Boreal forests

Pine, spruce and birch. The reason for these species is that they have been proven to sequester carbon from not just CO2, but also CH4. That is we only need to encourage and harvest what is already there. It must be harvested though, should they be allowed to age and decay the carbon is released.
From this article;

The report from the Canadian Boreal Initiative and the Boreal Songbird Initiative, entitled "The Carbon the World Forgot", estimates that the boreal forest—which survives in massive swathes across Alaska, Canada, Northern Europe, and Russia—stores 22 percent of all carbon on the earth's land surface. According to the study the boreal contains 703 gigatons of carbon, while the world's tropical forests contain 375 gigatons. 

From here, there are currently 1.6 billion hectares of boreal forests. The sequestration rate of these forests is highest in the first 20 years of the trees life. The rate is roughly 0.3 C ha/yr (link). That is, they must be extended, harvested, and replanted.

If a Mycorrhizal habitats are established in the boreal forests the carbon sequestration would be huge. This is what fungi love, decaying organic matter.

Fungi form oxalic acid C2H2O4 to breakdown matter, it does this by combining CO2 molecules. That is carbon sequestration.

Conclusion

We need to expand the use of Bamboo, extend and sustainably manage the Boreal forests. Both these actions should be done with the use of AB fungi. But most of all, we need to improve the soil.

There is a symbiotic relationship that can be enhanced between bamboo and fungi. The sequestration of carbon through either process would be significant. By using them together we could get the problem under control. There is an advantage as well when biochar is inoculated with fungi.
Obviously inoculating permafrost soil with AM fungi is a bit of a stretch for the average person, but making a difference at a personal level, is still something everyone can do. We need to;

• Eat more vegetarian food (so the land use can be changed). Grow our own to free up land and change the demand/supply equation for farmland. 
• We need to start using Azolla much more, particularly as food, green manure and as an energy source.
• Where possible don't use steel, bricks or cement for building. Use sustainably farmed wood, bamboo and hempcrete.
• Grow our own bamboo. There are clumping and running varieties. If you get the running type make sure you prepare the plot first (or you'll regret it).
• Make biochar for your vegetable patches. Making biochar is not as hard as it sounds. What I do is use a new clean empty paint tin. Punch a hole in the side of it. Fill it with wood chips and place it in the slow combustion heater with the hole pointed towards the fire. The syngas is burnt as it escapes. What is left in the tin is biochar.
• Buy hemp and bamboo products for everything possible.

There is no bypassing the fact that we must get CO2 emissions under control now. If the permafrost is allowed to release significant methane it would be very difficult to control.
We must begin to focus more on working with living processes. If we continue to ignore life, our ignorance will kill us. 
You would think I would finish this on a positive call to action, but unless we implement drastic changes in the way we emit CO2, and engineer a solution to the subsea permafrost the temperature will continue to warm at an increasing rate. We need a massive cultural shift.

There is hope given the mathematics, there is definitely hope. However given our societies fragmentation, I cannot see how we could make the necessary changes in time to mitigate some serious damage. I come back to the conclusion that we should prepare for exile, but there is definitely a solution.
If there was any government policy that should be pushed it is probably this, all seeds sold by nurseries should be inoculated, and Australia's soil needs to be repaired.
Perhaps Australia needs a new special visa. It could be called the EDP visa for Eat, Dig a hole and Poop.