Win/Win CO₂ Solutions Group Policy and Analysis Brief

Measuring the Amount of Carbon Captured in Natural Systems

A concern sometimes raised about the win/win ecosolutions approach that we are advocating to deal with excess CO₂ is that in order to significantly impact global levels of this gas sequestration would have to take place in an immense amount of land.  That means, they say, that it is not realistically possible to be confident that enough carbon is being removed to make a significant difference.  But as we explain in some detail below, this concern is unfounded.

It is true that measuring exactly how many tons of carbon are being sequestered on any individual acre is currently time-consuming and relatively expensive.  While this level of analysis is essential in research studies documenting carbon sequestration rates, these studies are done on relatively small study areas.  It is impractical to perform this same level of testing on every acre that would be part of the win/win ecosolutions approach.  (We highlight some examples of these studies finding that very large amounts of carbon can be sequestered here.)

However, the fact is that it is not necessary to know precisely how much carbon is being sequestered on any particular acre everywhere in the world to validate this approach as the best way to remove excess CO₂.  What is necessary is for those who have this concern to learn to “think outside their boxes” to understand why.

First, a few observations about their “boxes” and why for them this may be an understandable concern.  For most of them, their box only contains what we call “mechanical” approaches to removing excess CO₂.  These include such things as removing CO₂ from stack gas emissions or building “air capture” machines whose sole purpose is to pull CO₂ out of the atmosphere for some use or disposal, usually deep underground injection.  These mechanical approaches are, after all, how these engineers and others involved in developing these types of CO₂ strategies have been trained to think.  But it certainly does not mean that their approach is the best option.  Understandably, they are largely ignorant of alternative approaches outside their fields so they can only go around inside their own “boxes” with their “hammers” looking for “nails.”

But to be fair to them, this approach is also driven in part by the kind of regulatory or incentive CO₂ removal frameworks and approaches that are currently receiving the most attention (and funding!) and which require precise measurements.  These include “cap and trade” systems, carbon offsets, some aspects of carbon taxes and subsidies paid per ton of CO₂ removed.  For example, the U.S. government currently pays a subsidy for every qualifying ton of CO₂ removed under the “45Q” program so it is essential to document that a ton of CO₂ was actually removed from the atmosphere before the subsidy payment is made.

The role of vested self-interest on the part of those who question alternative approaches like these win/win ecosolutions also can never be ignored.  For these engineers and the corporations and institutions they work for, the prospects of research grants, lucrative consulting opportunities, contracts to build these mechanical devices around the world and much more all encourage them to stay inside their boxes.  In fact, it is these kinds of potential financial benefits that motivate at least part of the coalition of diverse special interests that have been pushing—successfully–for appropriating hundreds of millions of dollars in the U.S. alone for research, development and demonstration grants and subsidies for these approaches.  Much more is being similarly spent around the world.

In a larger sense, certainly, it is also understandable that policymakers and citizens who are motivated primarily by their concern that the increasing concentration of CO₂ poses an urgent and existential threat want to be confident that enough CO₂ is being removed to deal with that threat. Precise tonnage numbers are comforting.

Thinking “outside these boxes” about these win/win/win ecosolutions, however, certainly does not mean simply “hoping” that they are working on a large enough scale to achieve the goal of removing excess atmospheric carbon.  But doing so does require recognizing two major differences between this and the mechanical approaches that are currently getting the most attention and funding.  One is that unlike these other approaches, which are all at various stages of being invented or demonstrated to even be practical, nature has “proven” over millions of years that carbon sequestration in natural systems “works.”  Under a given set of a relatively small number of favorable variables, such as temperature, moisture, length of growing season, soil type, plant species, etc. the processes of photosynthesis, plant growth, and healthy soil communities will sequester carbon.  Guaranteed.  When regenerative techniques such as scientific grazing management, use of diverse cover crops, pasture cropping, restoring biodiversity and others are employed these naturally occurring sequestration rates can be vastly accelerated.  So long as these conditions remain relatively stable, much of this carbon is sequestered very long term.

Further proof of the magnitude at which this is happening globally is that the world’s soils currently contain about 3 times the total amount of carbon now in the atmosphere, most of that put there by natural processes (and that does not include carbon in the plants and animals living on the surface).  What is referred to as the earth’s “terrestrial sink” already absorbs about a quarter of the human-generated CO₂ being emitted each year? In fact, the ability of the terrestrial sink to continue storing roughly this proportion of the increasing amounts of CO₂ being generated by human activity is surprising to many scientists and is probably attributable largely to the increasing levels of this gas stimulating more rapid plant growth.

An informative global illustration of the power of plants to quickly act as a carbon sink by pulling CO₂ out of the atmosphere is the seasonal variation in atmospheric CO₂ levels (measured in parts per million or “ppm”).  As the “sawtooth curve” of atmospheric CO₂ concentrations shows, this level in the entire atmosphere varies by around 5 ppm annually depending on whether plants in the northern hemisphere are actively growing during the warmer months and photosynthesizing at maximum rates (and therefore pulling more CO₂ out of the atmosphere) compared to the winter months when the level of photosynthesis decreases and CO₂ concentrations rise.

With mechanical systems, the only proof that they are working, and how well, is the number of tons of CO₂ they are actually removing that otherwise would be added to the atmosphere.  And of course, this is the only way to determine the costs per ton removed for that particular mechanical approach or the subsidies that should legitimately be paid.

The second way it is essential to think differently about how much atmospheric carbon is being sequestered in natural systems is directly related to what some claim is the weakness of this approach: the massive scale on which it would be implemented.  There is, in fact, so much land area available on which to apply the specific management approaches that are proven to sequester vast amounts of additional carbon beyond what is happening currently that we can confidently live with much less precise measurements of how much is being sequestered on any specific acre of land.

To increase confidence levels even further that enough additional carbon is being sequestered we can simply do the equivalent of “over-engineering” in mechanical systems.  That is, we simply apply these proven carbon sequestering and synergy generating techniques to additional acreage beyond what we might already be confident in predicting is enough land to remove the targeted amount of CO₂ annually.  Keeping in mind that these same techniques are currently being applied on millions of acres around the world solely for the direct economic and environmental benefits they generate and are being applied without regard to the value that might be calculated from reducing atmospheric CO₂ loadings in the process, there would be little or no cost for such “over-engineering.”  This additional carbon is now being sequestered literally for free because the many important targeted environmental and economic co-benefits are already paying for the cost of implementing these techniques.

So if the goal is to achieve net zero emissions or net negative emissions (see our FAQ explaining these terms) we simply apply these proven carbon sequestration management techniques on enough acres so that the total average carbon being sequestered per acre more than achieves that goal.  As the research on the accelerated rates at which carbon can be sequestered shows, there is more than enough land available worldwide to do this. (See “What is the Potential for Sequestering Atmospheric Carbon in Natural Systems” here.)  

This is completely unlike the situation with mechanical systems, where over-engineering can result in higher costs, waste of materials and other negatives.  With sequestration in natural systems, over-engineering only results in more win/win/win/win co-benefits for the planet along with additional atmospheric carbon being removed.  These co-benefits and the additional sequestration begin in the first growing season and accelerate as the health of the ecosystem and soil communities is restored and improved.  As we point out in other places on this site, sequestration in natural systems is the only currently available, practical, cost-effective and proven approach for achieving net zero or net negative emissions levels within the timeframe that many consider to be essential to averting climate disaster.

It should also be noted that making such projections based on available science and estimating global averages for the amount of carbon being sequestered has already been accepted by many in the international community.  It is the basis for the 4 per Thousand international agreement which estimates that increasing the soil carbon stocks in the world’s forest and agricultural soils by just 0.4% per year would result in achieving net zero global CO₂ emissions for at least several decades, which we consider to be an extremely conservative estimate.  (See our discussion of this agreement here.)

All this being said, there are in fact currently available ways to get very solid estimates of the amount of atmospheric carbon being sequestered and the accuracy of those estimates is improving all the time.   For one thing, we have good data and an improving understanding of some of the key variables affecting sequestration rates as mentioned above.  There is, to cite another example, good weather data available for much of the world through ground and satellite measurements.

In addition, the federal and state governments in the U.S. have already done sophisticated science-based soil surveys of more than 95% of the nation’s counties and will soon have completed them for all counties  Many other countries are completing similar soil surveys.  The UN Food and Agriculture Organization has assembled similar maps for all the countries in the world.

Another particularly exciting new development is the sophisticated integration in recent years of satellite and other remote imagery in providing essential data on which to make decisions for the best land management practices.  Some Landsat data goes back 30 years so we have a valuable land history for large areas of the globe.  With modern computer programs, satellite remote sensing can even detect particular plant species, especially when combined with sample “ground truthing” documentation.  This allows us to document and better understand the changes (for better or worse) that have occurred on a particular parcel of land.  But it also provides a reliable and cheap baseline by which to monitor and document the changes as degraded land transitions from being a source of CO₂ (as much of the land in the world is currently) to sequestering carbon. For healthier land, we can monitor how it is becoming an even more efficient carbon sink.  A rough estimate of how much carbon is being sequestered is also possible using this satellite data.  An excellent article on the practical application of this technology to help better understand and manage semi-arid rangelands is available here.

Another example of new technology is the increasing use of unmanned aerial vehicles, or drones, to gather detailed imagery and landscape perspective cheaply and combine it with satellite imagery.  To cite another example, Sandia and Los Alamos National Laboratories have developed a highly reliable backpack unit for in-field testing of soil for levels of carbon as well as other soil elements such as nitrogen and phosphorous.  This will be particularly useful in developing countries.  History assures us that such innovative technological developments and imaginative ways to apply them will continue and will allow us to achieve ever greater precision in estimating how much carbon is actually being sequestered in any particular acre anywhere in the world.

As this happens we also will be able to continue to refine and improve models to provide yet another tool to estimate carbon sequestration on a large scale.  Such models are already being used to estimate the rates of carbon sequestration on national and multinational scales.  See, for example, the results of a model used to try to understand the soil carbon dynamics on the agricultural land of China.  Use of another model testing six different agricultural practice scenarios on the potential for soil carbon sequestration in Europe is reported here.

When dealing with any model it is wise to keep always in mind the admonition of famed British statistician George E.P. Box that “All models are wrong but some are useful.”  Both of these models use assumptions that are inadequate (and even wrong) in light of what is actually being demonstrated on the ground today around the world or are simply overly simplistic.  The model of soil sequestration in China, for example, estimated carbon sequestration in only the top layer of soil (30 cm/12 in.) when we know that sequestration is almost certainly always occurring at greater depths than that.  (See the examples of research that highlights this fact here).  So, while as Box says, it is a “given” that these models are wrong, they are also less useful than they could or should be because of these fundamental limitations.  With more sophisticated and varied inputs and with additional data points to test their retroactive predictive ability, much better soil sequestration models can certainly be developed that will allow us to be even more accurate in estimating how much carbon is actually being sequestered in natural systems on a very large scale.

The bottom line is that with just a basic understanding of the natural processes and dynamics of carbon sequestration in natural systems it becomes clear that this is as valid as any other approach to confidently dealing with removing excess atmospheric carbon.

Vested self-interest and the broad public interest rarely coincide completely.  And that is clearly the case here. If the costs, value of co-benefits, the speed of implementation and the potential to make a major difference in reducing and reversing the levels of atmospheric carbon are fairly compared between sequestration in natural systems and alternative mechanical approaches, the natural systems emerge as clearly superior. There is no question that adopting these win/win/win/win ecosolutions as the primary approach to dealing with excess CO₂ is the one that best serves the public interest.