Notes on Greenpeace’s Carbon Dioxide Removal Report
The Peril of Potentially Empty Promises
In mid-January, Greenpeace released an unheralded Report “Net Expectations”, that they state intends to help investors assess the potential of Carbon Dioxide removal (CDR) to meet their newfound commitment to net-zero CO2 emissions. The report not only provides guidance for companies regarding CDR, but also serves as an early warning regarding widespread plans for adoption of CDR. As we shall see, their report sheds light on potential pitfalls, problems, risks, and early warning signs in the hastily erected infrastructure and governance concerning Carbon Dioxide Removal.
Over the last decade or so, climate scientists have solidified their theoretical understanding of how to stabilize Earth’s temperature. The growing body of scientific literature strongly suggests that stabilizing the atmospheric concentrations of CO2 will stabilize the Earth’s temperature. As Greenpeace notes, doing so will require “carbon dioxide emissions to reach net zero”. With net-zero emissions, Earth’s atmospheric concentrations of carbon dioxide should stabilize, and so too will the associated ‘forcing’ of the Earth’s energy imbalance that causes climate change, and has already caused the Earth’s temperature to rise by about 1.2°C above pre-industrial temperatures. If the global community succeeds in reducing carbon dioxide emissions rapidly enough as we move towards net-zero, we have a chance to limit warming to the Paris Agreement targets of 1.5°C, and less optimally, 2°C.
Zeroing in on Net-Zero
What is meant by “Net-Zero”? The term refers to net-zero emissions of carbon dioxide (and to a lesser extent, other Greenhouse gases), such that every year, the amount of CO2 added to the atmosphere equals the amount removed from the atmosphere. In addition to natural CO2 removal provided by trees, ocean uptake, and the weathering of the world’s mountains by CO2 laden rainwater, there is a growing push to utilize natural and artificial technologies to remove carbon dioxide from the atmosphere and store it in trees or underground. While there are many such Carbon Dioxide Removal technologies, the Greenpeace report focuses on a handful of these CDR options.
For starters, there’s the natural technology, Afforestation and Reforestation or AR: planting and replanting forests. A related CDR technology is Bio Energy with Carbon Capture and Storage or BECCS: planting trees, then burning them for energy and capturing the resultant CO2 emissions and storing it underground. Lastly, there’s Direct Air Carbon Capture and Storage or DACCS: a high energy process that forces air through a tunnel at high temperatures wherein the Carbon Dioxide in that air attaches to a sorbent, and is then removed and injected into the ground, where it can no longer contribute to the greenhouse effect that is driving climate change.
Some astute and/or skeptical readers may be wondering why we even need carbon dioxide removal at all. If the point is to get net-zero emissions, why bother with negative emissions when that necessarily implies a positive emission counterpart to cancel out and achieve zero change in atmospheric CO2? Shouldn’t we just stop burning fossil fuels entirely? Long story short, there is uncertainty about renewable energy’s ability to replace “hard to eliminate” emissions, from energy intensive industrial processes, peak energy use hours, and for those days where the sun doesn’t shine and the wind doesn’t blow. Stanford’s Professor Mark Jacobson argues it’s possible to meet all of the world’s energy needs with renewable energy (wind, water, solar, and geothermal), and started “The Solutions Project”, which details how every state and most countries could meet 100% of their energy needs with today’s renewable energy technology. Conversely, a group led by Jesse Jenkins, Eric Larson, and Chris Greig of Princeton published a massive report outlining 5 distinct pathways to decarbonize the entire US economy, some of which feature a larger role for CDR technology like carbon capture and storage. It is this uncertainty about whether or not we need Carbon Dioxide Removal to meet emission reduction goals, and the extent to which we need for CDR, that informs Greenpeace’s Report.
Visualizing Pathways to Net-Zero
What exactly does a pathway to net-zero emissions look like, and how large of a role will CDR play in limiting warming to Paris Agreement Goals? The Intergovernmental Panel on Climate Change (IPCC) Special Report on 1.5°C has this useful graphic detailing three potential scenarios for reaching net-zero emissions. In the graph on the top right, there’s a legend of what each shaded region represents, and the bottom four graphs show four hypothetical scenarios for reaching net zero emissions globally. All four of the IPCC scenarios rely on some form of CDR to offset “hard to eliminate emissions”. In the graphs, these “hard to eliminate” emissions are the orange, green, and teal portions on the right-hand side of the graph from 2050 onward. If it’s not clear, the black line corresponds roughly to “net” annual global CO2 emissions.
There are some key things to note that aren’t well articulated by the above IPCC graphic. For starters, the orange area is emissions avoided through Fossil Fuel & Industry Carbon Capture and Storage (labelled FF&I CCS). All scenarios rely on this FF&I CCS smokestack Carbon capture to some extent. The Greenpeace report doesn’t consider this ‘Carbon Dioxide Removal’, as the CO2 captured from smokestacks was never ‘technically’ in the atmosphere in the first place. All the same, the seemingly benign orange area in the graph is rife with problems and concerns of its own (that I’ll come back to later) with direct implications for CDR technology that is being increasingly leaned on to meet Paris Agreement targets as global emissions continue to climb. Another unobvious acronym is AFOLU, which stands for “Afforestation or Land Use”, meaning the amount of CDR attributable to afforestation or land use change (land use meaning, say, restoring spongy marshland, or other non-forest changes). Lastly, it was unclear to me on first glance that the white area in the scenario graphs was ‘CO2 emissions from electricity’, and its possibly unclear to other readers that GtCO2 is Gigatonnes of carbon dioxide (which refers to global annual CO2 emissions).
If we are to limit global warming to 1.5°C, some variation of one of the above emission reduction scenarios will be required. As Greenpeace notes, the scenarios all include some form of CDR because a small percentage of emissions are unavoidable or hard to eliminate. Given those pesky emissions continue and aren’t replaced by renewables or nuclear, society must offset those CO2 emissions with CDR in order to stabilize or reduce CO2 concentrations, and thereby global average temperature.
Companies’ Net-Zero Plans
The Greenpeace Report highlights that some companies have finally begun planning to reduce or eliminate their greenhouse gas emissions. Three hundred companies have signed the “Business ambition for 1.5°C pledge”, which would see these companies reduce their emissions quickly enough to keep the world on a 1.5°C pathway. While not necessarily in line with Paris Agreement’s 1.5°C target, Greenpeace also notes thousands of companies are part of the United Nation’s “Race to Zero Campaign”, predictably aimed at getting CO2 emissions to net-zero. However, some of these companies plans are relatively vague and non-committal, and many of the world’s companies have yet to make any serious commitment to getting their CO2 emissions to net-zero. In the words of Peter F. Drucker, “Unless commitment is made, there are only promises and hopes; but no plans”.
However, Greenpeace does highlight a handful of companies that have published more specific plans for emissions reduction, with more or less ambition. American Airlines plans to offset emissions equivalent to 50% of it’s present total, begging the question what, if any plan they have for the other half. British Airways is more ambitious, which claims it will offset 95% of present annual emissions with CDR. As far as oil companies, Shell wants to plant a forest the size of Spain to offset CO2 emissions for their continued reliance on oil in their business model. Similarly, shipping company Maersk plans to achieve net-zero emissions in 2050 with CDR, and power companies Duke and Southern also anticipate using CDR to offset power emissions.
This rosy picture of corporations voluntarily planning to offset CO2 emissions with Carbon Dioxide Removal is unfortunately riddled with dozens of thorny problems that complicate the surface simplicity of the companies plans for emission reductions. For example, some companies inappropriately plan to use CDR to offset easy to abate emissions from fossil fuel power that could be easily swapped for renewables. As Greenpeace notes, “It is broadly agreed that CDR should be used only to offset emissions that cannot be avoided”. Since power could be supplied by renewables, it’s arguably unjust for them to rely on CDR, given potential ‘available land budgets’ we’ll get to later. Same goes for oil companies, whose products have powered internal combustion engines (ICE) that will need to go the way of the horse and buggy, so they can be replaced by electric vehicles that are powered by renewable energy and a massively expanded electric grid.
Other early signs of weakness in the early stages of global planning for CDR include relying on carbon markets. In the past few decades, international carbon offset markets have been rife with integrity problems, dubious accounting, double counting, and offsets that would’ve happened anyway without an emissions trading scheme. These historical problems with carbon markets are explored in depth in a recent book by David Victor and David Cullenward, “Making Climate Policy Work”, and in articles referenced at various points in the Greenpeace report.
The Greenpeace links identify problems with Emissions Trading Schemes such as additionality, where it’s not clear that emissions are lower than they would’ve been “under the most plausible alternative scenario”. It also points to ETS problems on credibility of climate governance from entities that are supposed to certify carbon credits are reliably generated. One study Greenpeace cites found that two carbon market projects in Madagascar and the Democratic Republic of the Congo were “virtual emission reduction machines” that not only inflated the generated carbon credits, but the ‘carbon offsets would’ve happened anyway, even without an ETS. Furthermore, these virtual emission reduction machines did nothing to impact economic forces driving local deforestation; deforestation which further weakens the ‘value’ of the offsets.
Key Problems with Reliance on CDR to Meet Temperature Goals
In a section of the Report titled, “Limits and Uncertainties”, Greenpeace identifies a host of potential problems staring down the potential buildout of a global Carbon Dioxide Removal regime. A key point of the Report is that relying on CDR is a risky and dangerous strategy to get to net-zero emissions (again, net-zero CO2 emissions is a necessary step to stop global temperature increases from climate change). It highlights a variety of limits regarding how widely CDR can be deployed, and uncertainties about it’s technical, political, financial, and climatic feasibility.
First and foremost, relying on CDR technology that is unproven at scale is a major risk to achieving internationally agreed upon targets for limiting global warming to safe levels, “The IPCC warns that reliance on CDR is a major risk to humanity’s ability to achieve Paris goals.” In particular, it is unclear if existing CDR technology can be scaled up to the massive levels highlighted in the IPCC SR 1.5 scenarios, wherein they are deployed to remove anywhere from 5–20 Gigatonnes of CO2/year. As of the present moment, smokestack CCS and BECCS are hardly deployed at all, and deforestation has continued apace globally: per the United Nations, “the rate of deforestation was estimated at 10 million hectares per year,” which outpaces present Afforestation/Reforestation efforts. As of yesterday, the only existing smokestack CCS in the US, Petra Nova (the orange figure in IPCC reduction scenarios), shut down because — wait for it — “the price of oil it could get with extracted CO2 wasn’t worth the cost of actually doing the extracting”. We’ll get back to that head-scratching point later. Lastly, as Greenpeace notes, present day deployment of DACCS is limited to 15 pilot plants globally, “with a combined capture capacity of about 0.01 MtCO2/year” a pittance that is one ten thousandth of a single Gigatonne of CO2/year.
Greenpeace’s report also quotes the IPCC special report on 1.5°C, “CDR deployed at scale is unproven, and reliance on {CDR} is a major risk in the ability to limit warming to 1.5°C.”. Furthermore, the IPCC specifically states that the longer the delay to reduce CO2, then “the heavier the implied reliance on net negative emissions after mid-century to return warming to 1.5°C”. Given the lack of proof of scalability for CDR technology and ongoing deforestation problems, there is already significant cause for concern in relying on CDR to meet Paris Agreement temperature goals. And we haven’t even gotten to some of the more significant problems with relying on Carbon Dioxide Removal to meet the world’s temperature goals.
Where does the funding come from?
Some types of CDR, such as smokestack CCS and DACCS, are quite expensive. Per the Greenpeace Report, DACCS projects are currently very expensive “$600–1,000/tCO2”, and even the hoped for price drop will still be expensive “$100–300/tCO2”. As noted, many companies are loath to pick up those costs for fear their businesses will lose their ‘competitive edge’ against other companies not adopting the same expensive CDR technology to offset their CO2 emissions. The Petra Nova story from earlier highlights another potential problem: the vulnerability of expensive mitigative tech like smokestack CCS to external pressures. This past year’s covid-caused recession made carbon dioxide removal less cost competitive, thereby hurting companies’ profits (a pandemic which may itself be made more likely by climate change and deforestation).
Why was it less competitive? Because oil prices went down, and it wasn’t profitable to sell the captured CO2 to oil companies as a fracking aid. Since the costs of CCS couldn’t be recouped by, ironically and tragically, selling the captured carbon to oil companies for fracking. So, the company behind the Petra Nova CCS operation, NRG, effectively said “the hell with it”, ceased the CCS operation, and went back to burning coal without capturing the emissions. The Petra Nova story is an illustrative example of the perils of relying on markets to drive emission reductions and CDR, where the moment cost-competition and profits are on the line, CCS that is *necessary* to stop climate change is completely stopped.
If companies won’t foot the bill for expensive CDR projects, where can we expect the funding to come from? It is possible that federal governments could pass CDR standards, such that for every tonne of CO2 a company emits, they have to offset a proportional amount, hypothetically starting at 50% of total emissions in 2030, and increasing to 100% in 2050, which would force all CO2 emitting companies into a level playing field. Of course, that doesn’t tell you much about monitoring (or how the monitoring will be paid for), nor should we assume that companies will go along willingly and without objection.
While capitalist economic theory asserts that free markets and competition ‘drive innovation’: some sound counterpoints exist from Mariana Mazzucato in her groundbreaking book “The Entrepreneurial State, Debunking public vs. private sector myths”, in which she argues that the Public Sector is a much larger innovator than classical economic theory supposes. In practice, some of the most fervent and crazed private sector ‘innovation’ has been aimed at getting around standards and regulations. Volkswagen infamously rigged their vehicles to emit less CO2 while being tested, with a secret switch that made it look like their cars were meeting fuel efficiency standards; off the showroom floor their cars went back to belching carbon dioxide in droves.
As an alternative, local or national government could foot the CDR bill, although that would almost assuredly come with an attendant increase in taxes. With economic inequality at an all time high, it’s not clear that raising taxes on fuel consumption which would likely disproportionately impact the poor, would be popular or even tenable. The recent Yellow Vest protests in France over proposed fuel tax hikes are perhaps an early sign that regressive (disproportionately impacting the poor) tax policies to fund CDR would be a bitter pill to the working class of the world. More progressive (disproportionately impacting the wealthy -> whose taxation does not impact their ability to eat) taxes like a wealth tax, income tax on the top 1% (who have gobbled up most of the recent economic gains), or taxes on high volume Wall Street Trading — that tends to fund polluting industries anyway — would fit and foot the funding bill. Albeit, doubt is everlasting about politicians whose campaign funding comes from oil companies and those standing to be taxed in these scenarios ever finding the backbone to tax the rich.
Who will pay for CDR? The answer is not obvious, and this first of many problems is a key sign of weakness in the global buildup of a CDR regime. If you’re not sure how you’re going to pay for a plan, is it really much of a plan at all? As the prices of renewable energy and electricity continues to plummet, it’s not entirely clear why the a priori focus of policymakers isn’t funding the buildout of technology that stops emissions in the first place, rather than a distant, veritable pipe dream for removing emissions later.
Hundreds of Years of COsolitude: Regulating CDR
Another key problem facing any global CDR regime is that of regulation, that I briefly touched on regarding emissions trading schemes. In addition to the questionable forestry offsets for early ETS’s, the entire premise of BECCS, DACCS, and smokestack CCS (notably, the orange and yellow shaded areas in the IPCC’s 1.5°C scenarios) is based upon a capitol S Storage. For starters, Greenpeace notes of the current 21 extant CCS operations worldwide, “only one captures CO2 from bioenergy” and “all but five of these are used for enhanced oil recovery” (EOR). As alluded to earlier a la Petra Nova, (almost like new petrol…), the Texas based coal company’s CCS plant used it’s captured carbon dioxide as a fracking aid to blast into the ground to help reach hard to access oil. By this writer’s calculations, the carbon dioxide captured from the Petra Nova operation and ‘stored’ in the ground is *LESS THAN* the amount of CO2 to be released from the barrels of oil that the CCS with EOR enabled.
Who will regulate CCS projects to ensure that the ‘storage’ isn’t utilized to *increase* CO2 emissions? Who will regulate the actual devices to ensure that they are capturing as much CO2 as they claim they are, as opposed to just cheating the system like Volkswagen did with fuel efficiency standards? For the proposed amount of CCS, BECCS, and DACCS in the IPCC scenarios, a vast global — or patchwork of national — regulatory apparatuses (apparati?) would be required.
The regulatory problems don’t stop there, and indeed the problem lasts for centuries, if not millennia. As Greenpeace notes, CO2 (and natural gas) “pipelines have often leaked” in one case so dramatically that the CO2 settled into valleys and suffocated local deer and other animals, and also that “storage sites found to be less secure than previously believed”. In another disastrous example of unregulated CCS-EOR pipelines bursting, 45 people in Mississippi were hospitalized after a pipeline burst. A CO2 burial process that is not regulated in the first place and monitored for leakage for centuries maintains the risk of catastrophic failure, should some of the CO2 leak or burst out due to cheaply built pipelines or improper storage. The IPCC’s four proposed scenarios all entail 5–20 gigatonnes of Storage per year, the potential for leakage is not some challenge to be left unregulated.
On the Resilience of CDR to Climate Impacts
Will CDR be Resilient to the climate change impacts unleashed by relying on CDR to prolong current emissions, and indeed, is supposed to offset? This question isn’t addressed in the Greenpeace Report, but if countries and companies of the world are hoping to utilize BECCS in the future to offset current emissions, a la IPCC SR 1.5 Scenario 4, then a very pertinent question becomes how will the “bio” of BECCS withstand the incoming heat that delayed action portends?
Per the latest update from Climate Action Tracker, the countries of the world have current climate policy that would see the world warm 2.9°C relative to pre-industrial temperatures by 2100. Countries’ pledges and targets are marginally better and are estimated to yield 2.6°C warming. This is still a far cry from Paris Agreement targets of 1.5°C and 2.0°C. Both current policies and pledges are *projected* to yield this much warming, assuming they are carried out. This is no small order for countries like the US and Australia, whose resident Conservative parties continue to resist any and all action to mitigate climate change by decreasing fossil fuel use. At any point, a failed election, a political coup, lack of political willpower, unambitious taxation, or countries operating by the same ‘cost competitive’ logic that drives corporations to cheat, could yield worse emissions— and therefore global avg. temperature — outcomes than current policies and pledges foretell.
A key distinction: the IPCC’s 1.5°C scenarios I’ve highlighted previously are *NOT* the same thing as the sum of countries’ current policies or pledges to reduce emissions. The IPCC scenarios detail what *would be required* in the event that countries and corporations drastically ramp up their ambition to mitigate climate change. The distinction between relying on CDR, and in particular, BECSS at 1.5°C or nearly 3°C is no small matter, in no small part because the IPCC’s SR 1.5 estimates (the same one with scenarios relying on CDR) 20%-35% of natural vegetation will be threatened by 3°C warming.
With 20%-35% (eyeballing it) of global vegetation threatened by climate change at 3°C, this raises the specter of whether plant based CDR technologies can be scaled up. It’s not clear it’s wise to rely on bio-tech (trees) that is vulnerable to the very CC impacts it’s supposed to help mitigate, by virtue of delaying actions to reduce emissions, hoping that we can reduce carbon stocks in the atmosphere at some later point. Extreme heat, drought, and wildfire all pose risk to the potential use of AR and BECCS to offset current plans to continue extracting and burning fossil fuels. Wildfires (and the Amazonian tipping point) may well see the world’s forests become a net source, rather than sink, of CO2 emissions. The resilience of natural Carbon Dioxide Removal (CDR) to climate change appears to be vulnerable to the warming current policies foretell. The potential dangers of waiting too long should be a clarion call to reduce emissions now, instead of relying on vulnerable natural technologies to clean up our Carbon mess at some distant point in the future.
A Global Available Land Budget for Natural CDR
An often-overlooked element of the CDR problem is that the world is finite. There is not limitless, suitable land for forests for AR or BECCS, and CDR must also compete with scarce land resources for food production. The Greenpeace report quotes an IPCC estimate “that the maximum sustainable CO2 removal in 2050 by new forests is somewhere between 500 and 3,600 Mt [Megatonnes] per year. Similarly, this is the ~maximum available BECCs. A first problem facing our available land budget: AR and BECCS compete for this finite space.
On its own, BECCS will require massive amounts of land. One figure cited in the Greenpeace report estimates that using BECCS to sequester 12 GtCO2/year would require a landmass one to two times the size of India! The report highlights that this is equivalent to “25–46% of total world crop-growing area”. Conversely, it doesn’t explicitly address the added problem of population growth, but the United Nations estimates the world will have another 2.5 billion people in it by 2050, and add another billion for 11 billion total by 2100. In addition to AR and BECCS competing with each other for scarce land resources, if the UN’s population estimates come to fruition, those technologies will also be competing with future human’s food and habitats.
When gauging the feasibility of corporations’ and countries’ plans to rely on natural CDR like AR and BECCS, one must remember this fundamental global land budget that we all have to share. Our global land budget is one of the primary reasons that power companies and oil majors shouldn’t be able to offset their planned emissions: we have a limited land supply, and their energy could be replaced with renewables. There is not an infinite supply of land to suck CO2 out of the atmosphere, and governance of planned CO2 removal needs to start recognizing that fact ASAP.
To illustrate some early indications of the folly of relying on massive future forest offsets to zero-out current planned CO2 emissions, let’s re-examine Shell’s planned afforestation. The above image from a 2019 Bastin et al. paper in Science estimates that there’s room for an additional 900 million hectares of canopy cover. Per Greenpeace, Shell is considering (not planning on) “planting 50 Mha [megahectares] of forest to offset its own emissions”, which Greenpeace notes “could effectively claim one tenth of the sustainably available total” (per a separate estimate of available land).
For some context, Shell is one the 10 largest oil companies in the world. If each of these 10 companies ‘lay claim’ or ‘propose to’ plant 50 Mha of forests to offset their planned emissions, those 10 oil companies would use up somewhere between *50–100%* (per Bastin or Greenpeace accounting) of the global available land budget. The ludicrousness of this is hard to stress. There are five hundred fortune five hundred companies in the US, and tens of thousands of large companies around the world, to say nothing about countries planning to offset their emissions with AR or BECCs. Why should any one corporation get to “claim” 5–10% of the available land budget, necessary for natural CDR like AR and BECCS, to shore up its own profits by continuing to stoke the climate crisis? Is it wise to use up currently unused agricultural land to offset emissions that could simply be replaced by renewables? In addition to governance and regulation problems with storage, here we find another unaddressed problem. There is currently no systematized global governance or regulation of the finite available land that could potentially be used for various CDR projects.
Granted, DACCS and smokestack CCS are also options, but they are more cost prohibitive and DACCS is less efficient, unproven at scale, used for enhanced oil recovery, and abandoned when cost competition is on the line. And mid-writing process, I just discovered that DACCS also has prohibitive land requirements at scale. A paper published last year estimates that “to remove 1Gt of CO2 using solar-powered DAC would require a land area ten (10) times the size of the state of Delaware”. A quick calculation reveals that 10 Delawares is about 6.7 megahectares, for a single GtCO2 (presumably per year). If you want to remove 12 GtCO2/year with DACCS, it would require a landmass roughly the size of Brazil.
All three of these technologies, AR, BECCS, and DACCS are therefore competing with not only each other, but also with food production for a finite amount of space that may well shrink as the world’s population grows. The available land budget problem is a serious crisis for the incipient regime of global CDR, and one of the strongest cases for just paying to reduce emissions now by building up renewable energy capacity and electrifying everything.
Towards an Available Energy Budget
In addition to scaling, cost, and land use challenges, DACCS faces another monumental obstacle to widespread deployment. Direct Air Carbon Capture and Storage requires epic levels of energy. As Greenpeace notes, “Capturing three quarters of present CO2 emissions would require half of present global electricity generation”. Which is perhaps a bit of an overstep: globally, we emit about 38 GtCO2/year, and none of the IPCC scenarios entail using DACCS to shoulder the burden of sequestering 29 GtCO2/year. However, to sequester a single GtCO2 you’d not only need 10 Delawares of land, but still about the equivalent of 2% of current global electricity generation, no small number.
Greenpeace doesn’t discuss the implications of such a large energy requirement, but they are important. The world’s task in the coming decades is to transition most of energy supply from fossil fuels to renewables, and revamping transportation to be largely powered by electricity from renewables. In order to meet the 1.5°C or 2°C targets will already require a massive scale-up of renewable energy. Per Carbon Brief’s estimates, 1.5°C necessitates CO2 emissions reductions of about 7%/year every year for the next decade. Meaning, if the world is to strictly maintain its current amount of energy supply, it will need a corresponding uptick in development of renewable energy.
Lest we forget, much of modern capitalist economics is predicated upon endless compound growth. Historically, global economic output is tightly coupled with energy usage. To meet the world’s energy demand, the renewable transition would have to accommodate both lost fossil fuel energy output and the economic imperative of growth (which, is hotly debated as to whether this is even advisable… but I won’t go into the degrowth movement here, both for brevity’s sake and because I don’t know the discourse well enough). If we add in the additional burden of powering DACCS to remove CO2 from the atmosphere, there will be quite the strain on the world’s energy grid.
One of the reasons that DACCS is so expensive per tonne and requires so much energy: it’s incredibly inefficient. As readers of my blog may well know, atmospheric CO2 is at about 418 ppm, or parts per million. For every million ‘parts’ of air, only 0.04% of it is carbon dioxide. With such small quantities, pulling CO2 out of the atmosphere isn’t very efficient, no matter how much energy you use to blast air at high heat through a tunnel and into sorbents and solvents for CO2 to bind with. In sum, DACCS has myriad problems and challenges to potential widespread use. It’s expensive, inefficient, energy intensive, requires a lot of land, competes for scarce land resources with other CDR tech, is unproven at scale, and will also face serious governance challenges.
Challenges for Trees, and Speaking for the Trees
It is a simple and wondrous truth that our best technology in the fight against climate change is an ancient biological one. Trees and the forests they compose are not merely the tools of would-be geo-engineers, bent on using CDR for AR and BECCS to further enable human’s addiction to fossil fuels. Earth’s forests pull CO2 out of the atmosphere year in and year out to help themselves grow.
One little appreciated fact about natural forests that Greenpeace highlights is that they “store six times as much carbon as agroforestry, and 40 times as much as plantations, according to one study”. Natural forests are true wonders of the world, and their carbon sequestering potential makes it all the more important to conserve the few wild, natural forests left on Earth, in addition to planning to plant more forests. Since natural forests sequester more CO2, AR efforts may be best focused on allowing forests to rewild, as opposed to relying on agroforestry and tree plantations.
However, there are some recent scientific studies published during the pandemic, that cast a shadow on the potential for trees to suck our CO2 sorrows away like inverted dementors. Back in May a team of scientists led by Martin J. P. Sullivan published a paper, “Long-term thermal sensitivity of Earth’s tropical forests”. The study analyzed tropical forests around the world and found that daily maximum temperature is “the most important predictor of aboveground biomass”, with temperatures above 32.2°C more greatly reducing the ability of forests to store CO2.
While 32.2°C is quite hot, and many readers may be wondering how likely it is that trees regularly face that temperature threshold, recall that this was a study of tropical rainforests. In the Brazilian city of Manaus, nestled on the banks of the Amazon river, daily high temperatures already average anywhere from 30.4°C to 32.9°C (note: it’s unclear if this is the historical average {pulled down by older, less climate-changed temperatures} or a more recent average of the last 30 years or so). The world is presently at about 1.2°C above pre-industrial temperatures. With country’s current emission reduction pledges, global average temperature could rise further to 2.9°C by the end of the century, which could well push Manaus above the threshold 32.2°C daily maximum temperature year-round. This would significantly hamper tropical rainforests from doing the heavy lifting in pulling CO2 out of the atmosphere.
Another paper published in the shadow of Covid was led by Christopher Trisos, and assessed the estimated timing that various “ecological assemblages” are exposed to dangerous climate conditions. In the same vein as the Sullivan paper, it discussed the impact of higher emission climate scenarios on tropical forests (and other ecosystems). The authors found that an estimated 2% of global ecological assemblages could be impacted with 2°C warming, and a further 15% with 4°C warming. Importantly, those percentages are of worldwide ecosystems, and the authors stress that the majority of the impacts would be felt tropical rainforests and coral reefs. Of particular concern for humanity and advocates of CDR: the tropics are where much of the available land for AR and BECCS exists. If, in relying on expensive, unproven, energy intensive CDR to remove CO2 from the atmosphere at some indefinite later date, we postpone getting off of fossil fuels in the short term, the CO2 that we emit in the meantime may well avert the possibility of CDR working in the future, by passing thresholds beyond which tropical forest ecosystems cannot survive.
Recall the above Graphic of 1.5°C scenarios from the IPCC. The latter two on the bottom right feature significant overshoot of the 1.5°C target, and may put us close to that 2°C threshold that Trisos identifies for “abrupt ecological disruption”. Again, the IPCC scenarios do *NOT* equal *actual* emission reduction policy or pledges. Per Climate Action Tracker, current policies and pledges have us on a path for anywhere form 2.6°C to 2.9°C warming. Unless nations ramp up their ambition and policy to reduce their CO2 emissions, they may well shoot themselves in the foot with the silver bullet of CDR they had hoped would clean up the carbon mistakes they are planning on making.
A third study from last year’s pandemic Spring by Brodribb et al. reviewed the available literature on tree adaptability that turns the oft claimed ‘climate downplayer’ notion that tress will ‘absorb more CO2 with higher temperatures on it’s head. With increasing global average temperatures comes higher frequency, intensity, and duration of droughts. As temperature rises, it is increasingly likely that forests with more consistent climates (i.e. tropical rainforests) will be exposed to droughts of higher intensity and duration than many tree species have evolved/adapted to in their current ecological niche. In short, the higher global temperature goes, the more likely tree die-off becomes. Whether trees die by wildfire or drought and decomposition, much of their stored CO2 is released to the atmosphere, exacerbating climate change.
This provides greater urgency for getting off of fossil fuels as soon as possible, and reducing our reliance on forests to ‘offset’ continued GHG emissions. In particular because many of these forests will also be exposed to increased wildfire risk. In Australia this past summer, wildfires released more CO2 to the atmosphere than Australia’s annual fossil fuel emissions. Remembering, as we must, that current climate policy and pledges have us on track for 2.6°C-2.9°C by 2100, our planned reliance on AR and BECCS to offset plans to continue relying on fossil fuels is looking more and more like fossil folly.
Irreversibility Problems with Planned Reliance on CDR
In addition to all of the above outlined problems with relying on future Carbon Dioxide Removal to offset the next few decades’ emissions, it’s important to note that CDR can’t turn back the clock on all things climate change. While it’s theoretically possible for widespread deployment of CDR to pull Gigatonnes of CO2 out of the atmosphere, thereby reducing it’s warming forcing, CDR cannot undo other climate change impacts.
Planning to burn more CO2 now to be removed later, if successful, will not remove the massive amount of heat that’s been stored by the oceans. Worldwide, ocean’s have absorbed an estimated ~90% of the heat contributed by global warming, and CDR cannot remove this heat, which has deleterious impacts on fish, coral reefs, and other ocean life. Similarly, CDR cannot act as an ‘undo’ button for key climate tipping points, like the melting of ice sheets. Even if CDR allows humanity to offset ‘hard to eliminate’ emissions into the 22nd century and stabilize temperature, if we pass thresholds that cause significant melting of the Greenland or Antarctic Ice Sheets, CDR will not magically undo that ice sheet loss and bring dead glaciers back from the grave. Nor the associated sea level rise when the ‘lost’ ice ‘finds’ a new home a few feet above current sea level.
Ocean heat content isn’t the only killer of sea life. In addition to CO2 warming the atmosphere, it also gets absorbed by the world’s oceans, acidifying them to levels that are above the historical adaptive range of a lot of marine species. Similar to the world’s trees, marine species are also vulnerable to rapid changes in their habitat outside the historical range. In the case of ocean acidification, it’s already dissolving the shells of Dungerness crabs in the Pacific Northwest and other mollusks like sea butterflies in Antarctica.
Understudied Public Health Considerations
Suppose one of the scenarios with higher negative emissions from the IPCC’s Special Report on 1.5°C comes to pass. The world is relying on on CDR, and in particular BECCS to pull 5–20 GtCO2 from the atmosphere annually, with a corresponding increase in burned biomass. While it’s true that BECCS captures the resultant CO2 emissions to store them in the ground, none of these scenarios factor in the potential for an increase in unmitigated aerosols and particulate matter from a meteoric rise in bio-energy.
It’s hypothetically possible that governments could add legislation mandating that BECSS facilities *also* capture resultant aerosol/particulate matter emissions created by burning biomass. However, this would presumably raise the costs of BECCS as an energy source and carbon capture solution, making it less viable on the market.
Furthermore, there are early signs that particulate matter from burned biomass may be more hazardous for human health than other sources of particulate matter. While it has long been assumed that the toxicity of Particulate Matter 2.5 (PM 2.5, as in less than or equal to 2.5 micrometers) has equivalent toxicity across emission source, recent research suggests this may not be the case. In a paper released in March, 2021 by Aguilera et al., the researchers found a significantly higher rate of increase in respiratory hospitalizations (1.3%-10%) from wildfire-specific PM 2.5, relative to non-wildfire PM 2.5 (.67%-1.3%). The researchers point out that as wildfires have been increasing in frequency, intensity, duration, and length of the year in which they can occur, this is a pressing public health issue.
To this author’s knowledge, there are no papers explicitly studying potential adverse health impacts of relying heavily on BECCS to meet CDR needs. While the Aguilera paper doesn’t specifically look at pollution impacts on respiratory hospitalizations from burning biomass, en masse, it does suggest that burning biomass could be incredibly hazardous for public health, yielding more toxic PM 2.5 than is yielded from other emission sources. This is an area that’s been woefully understudied, and suggests IPCC scenarios that rely heavily on BECCS (in conjunction with increased wildfires from climate impacts), may have drastically underestimated negative impacts on public health, if it is indeed the case that PM 2.5 from biomass has worse impacts on public health than other PM 2.5 sources.
Furthermore, given the higher energy demands of urban areas, one could expect the air quality and public health impacts to be larger in cities. Heavy reliance on BECCS would likely offset some of the expected health benefits in reduced mortality from poor air quality (estimated at 8.7 million annually by Vohra et al. 2021), as well as other public health impacts like asthma attacks and hospitalization burden. Indeed, a group of public health organizations wrote to the US government in 2016, cautioning against heavy reliance on bio-energy generally, citing potential risks to public health. To quote from the letter, “Biomass is far from “clean” — burning biomass creates air pollution that causes a sweeping array of health harms, from asthma attacks to cancer to heart attacks, resulting in emergency room visits, hospitalizations, and premature deaths”.
Implications, Warnings, and Conclusions
Carbon dioxide removal is being sold as a key, if not essential tool in the climate change mitigation toolbox. This has been pushed in no small part by the fossil fuel industry, whose keen interest in CCS should give pause to enthusiasm over its potential utilization. However, as the Greenpeace Report highlights, there are significant flaws to its potential widespread deployment. To recap, it’s expensive, energy-intensive, has a limited land-budget, competes with food production and habitats, different CDR options compete with each other for land, it is unproven at scale, is currently used to *increase* oil recovery, is prone to stoppages when it’s not ‘economical’, has many axes of governance problems, is prone to cheating, is poorly regulated, planned BECCS plantations are less efficient than natural forests, and the Storage of CCS is uncertain due to the potential for leaks in pipelines or storage. Greenpeace doesn’t say it explicitly, but the implication is that it’s much better to just reduce emissions now, instead of crossing our collective fingers that CDR will solve our CO2 problems.
Furthermore, recent studies on forest and tree survivability with warming we’re currently headed for, ice sheet tipping points, and the irreversibility of ice sheet loss, sea level rise, and biodiversity loss (under-explicated in this article) are further warnings against relying on CDR. Negative emissions technology is not a panacea that will solve all of our climate change problems. CDR may in fact be of some use, but planning to rely on it heavily is increasingly looking like planning to fail.
Of course, this should not be cause for despair, rather cause for increased motivation and determination to eliminate CO2 emissions as soon as possible. Recent studies have demonstrated that reaching net-zero emissions should stabilize global average temperature. In addition to the aforementioned works of Mark Jacobson of Stanford and Jesse Jenkins team at Princeton on decarbonizing America’s electric grid, Robert Pollin and Noam Chomsky’s book “Climate Crisis and the Global Green New Deal”, and a recent report by Rewiring America also detail strategies for how we could electrify a significant portion of the world’s energy grid (powered by renewables) in the near future. There may yet be a role for CDR, but the problems and warning signs are significant enough that policy approaches to mitigating climate change should prioritize immediate efforts to reduce CO2 emissions with renewable energy replacements, instead of relying on an “unproven” technology to save us from ourselves.
