Direct Air Capture: How the fight against climate change will be won or lost

Fifteen years from now, when the Great Barrier Reef is a thing of the past, when downtown Atlantic City, Bangkok, Boston, Charleston, Dhaka, Galveston, Honolulu, Jakarta, Lagos, Manhattan, Miami, Mumbai, New Orleans, Newark, Rotterdam, San Francisco, Seattle, Tampa, and Venice relocate, and when Australia and California burn, everyone — from farmers to stock brokers, peasants to politicians– will be asking the same question: Are the machines working?

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Those machines will be sucking carbon out of the air and burying it deep in the ground or under the sea. We don’t know exactly where they will be, what they will look like, or even how well they will work. All we know is that we need them (Lackner et al 2013).

Reducing our carbon emissions, which humans have proved incapable of, is not enough now. Even reducing to zero emissions tomorrow is insufficient. We are too far gone in the wrong direction. What’s more, like a ship heading for the end of the world where the water falls off the edge, our foot is still on the accelerator. Slowing down is good, but insufficient to avert disaster; we must turn the ship around and head the other way. We need to not just reduce emissions, we need to reduce the amount of CO2 already in the atmosphere. That means negative emissions– sucking carbon out of the air.

Direct Air Capture vs Flue Capture; Sequestration vs Re-Use

Carbon capture from ambient air, also called Direct Air Capture (DAC), is different from conventional carbon capture at factory chimney flues (i.e. point source carbon capture). First, it’s a lot easier to capture carbon from flues because the CO2 is concentrated. Second, typically the goal of flue carbon capture is to minimize CO2 emissions and often to re-use the CO2 in a process that reduces the need for fossil fuels. If it is re-purposed, you’ve reduced CO2 emissions from fossil fuels, but the CO2 is still released into the atmosphere. This is a process to reduce emissions; it is not net-negative.

There are also plans to capture carbon, from the air or from flues, and use it in a variety of other industrial processes, from putting bubbles in soda to (wait for it)… extracting more oil. These plans are merely meant to reduce emissions and also to incentivize the private sector to capture carbon. But it’s not net-negative.

Feasibility

Back to direct air capture. Here’s the catch: we don’t know if we can do it at the scale needed. Fortunately, humans have been much better at finding technological solutions than political ones. There are more than a dozen pilot projects in Iceland, Switzerland, and elsewhere showing it can be done– on a very small scale. There are a host of questions, but the biggest challenge is sucking it out of the air in an efficient and cost-effective way.

Funding

Feasibility aside, there’s the question of how to pay for it. Suppose we wanted to capture and sequester 7 billion metric tons of CO2 annually, which is the IPCC goal by 2050. Currently we emit 43 billion. Early estimates are that it would cost $700 billion/year (at $100/ton) and require an enormous amount of energy, up to a 12% of annual worldwide energy use. But those are early estimates. Technology gets better and cheaper with time. The Center for Negative Carbon Emissions at Arizona State University thinks it can be done for $210 billion/yr (using $30/ton) and require only 1% of worldwide energy use.

For context, worldwide military spending is $1.8 trillion/yr (or $1,800 billion), nearly half of which is by the US. If the armies of the world ever wanted to save a city, let alone a village, they have the money to do it.

Ultimately, governments will have to pay for carbon capture and sequestration. There is no way to incentivize the private sector to bury a product rather than re-use it. In the near term, we can benefit from private sector carbon capture and re-use because, although it is not net-negative, it can incentivize research into DAC technology. And it does reduce emissions.

DAC on a meaningful level requires international coordination and, of course, cost sharing. The two most obvious models would be to apportion cost share based on current or past CO2 emissions.

Each nation will likely be up to its own to develop their own funding mechanism. A carbon tax is an obvious solution. If DAC costs $100/ton, that translates to 88 cents/gallon at the pump. Other fossil fuel uses would also have to be taxed as well. While this sounds affordable, there are two complicating factors: 1) we can’t just address the gallons of gas we are buying now; we have to address all the gas we have ever bought and all our parents have ever bought; and 2) carbon taxes are regressive, hitting the poor more than the rich (as a percentage of their income). There are ways around that, a subject for another blog post.

The enormity of the task means that technological innovations to lower the cost are critical. This should not be left to small policy initiatives like research grants and tax incentives. This requires the full weight of all the major governments and universities in the world. Progressive governments in Europe and California (where Democrats have super-majorities in both houses of the legislature) could and should embark on DAC projects immediately.

The Free Rider and Moral Hazard Problems

CO2 released anywhere in the world spreads everywhere, and DAC done anywhere reduces CO2 everywhere. This is both good and bad. It means that DAC can be done anywhere, allowing us to select the most expedient locations. For example, a DAC pilot study in Iceland uses clean geothermal energy to capture carbon and inject it into porous volcanic rocks.

But it also means there’s a potential free rider problem, where countries will shirk their obligations in the hopes that others will take care of it for them. One can imagine rogue nations that refuse to pay their fair share and free ride on the public service provided by other countries. The US, whose share would be large by any measure, is a candidate for such recalcitrant behavior. Public support for DAC could overcome this.

It is possible that Republicans would support DAC. The US Congress recently passed a $50/ton tax credit for DAC removal, the most ambitious such incentive in the world. Republican support, however, probably came from the associated $35/ton tax credit for carbon captured from the air and used for enhanced oil extraction. Regardless, Republicans could see DAC as an opportunity to extend fossil fuel use into the future. And therein lies the moral hazard problem. If we’re doing DAC, one could argue that we don’t need to reduce emissions as much. And if DAC became cheap and easy, fossil fuel use (aside from the spill risks and air quality impacts) could arguably continue.

But, like with a penny saved rather than earned, carbon not emitted is carbon you don’t have to capture and sequester. There are two more reasons why reducing emissions must still happen: 1) at the moment, it’s still cheaper to reduce CO2 emissions than to capture it; and 2) we are nearing the edge of the world, when it’s too late even to capture carbon.

Positive Feedback Loops

This brings us to the gremlins in the room– positive feedback loops. These are additional sources of global warming that are caused by the current global warming. They are force multipliers, accelerators, that can make global warming much worse very fast. It’s hard to predict when they will kick in. If they do, our job will become much much harder. We will lose ground, a lot more ground (read human suffering) before we win. They put victory in doubt.

Some positive feedback loops, such as increased water vapor in the air and dark seas and mountains exposed from melting ice and glaciers, have been accounted for in climate models. More pernicious are the more unpredictable “time bombs”, such as permafrost melt and massive wildfires.

Melting permafrost is the proverbial elephant of the gremlins in the room. Research suggests that rapid methane releases from melting permafrost may have been the final driver in runaway climate change that led to past mass extinction events, including the End-Permian Extinction in which 97% of all life on earth perished. This effect is already happening. NOAA recently reported that melting permafrost now contributes as much as net 0.6 billion tons of carbon (equivalent to 2.2 billion tons of CO2) to the atmosphere each year; “the feedback to accelerating climate change may already be underway.”

Forests are normally carbon sinks, taking in CO2. However, in 2006 Westerling et al warned that “forests of the western United States may become a source of increased atmospheric carbon dioxide rather than a sink, even under a relatively modest temperature-increase scenario.” Since then, wildfires have increased dramatically.

These positive feedback loops are like an increasing current threatening to pull the ship over the falls. If we are waiting for technology to save us, we may have waited too long.

Controlling the Climate

In the long run, Homo sapiens might eventually hopefully maybe win the climate battle and be able to capture and sequester enough carbon to return the earth’s atmosphere to normal conditions. But there will be suffering in the short-term, for the next two hundred years, thru sea level rise, heat waves, droughts, powerful hurricanes, and agricultural disruption. The poor will suffer most. Turning the climate around is like turning a cruise ship. There’s a lot of lag time between cause and effect. That’s why humans have found themselves in the current crisis. Only the scientists saw it coming. Nobody felt the impacts until now, and now it’s too late to avoid them. The same is true regarding corrective measures. A lot of sea level rise, caused by ice melt in Greenland and Antarctica, is already built into the system. It is coming and coming at an increasing and exponential rate. We may have to actually cool the planet beyond the recent historic level to stop it. And that may take 150 years. In the meantime, hundreds of coastal cities will go under water. This appears inevitable, even under the most optimistic scenarios.

The graphs below present the most wildly optimistic scenario, achieving the Paris goal’s peak emission in 2020 (this year), DAC of 7 billion tons of CO2 per year by 2050, plus optimistic net removal thru reforestation and new soil management practices, all of which help to get us to net-zero emissions by 2050, another Paris goal. After that, we remove more than we emit; we are net-negative, returning the earth to under 400 ppm.

It would be great to just use natural approaches to sequester carbon (e.g. reforestation and soil management). But the numbers just don’t add up fast enough. During past global warming events (e.g. the Paleocene Eocene Thermal Maximum), it took the earth’s natural processes tens of thousands of years to restore balance. We have put so much carbon up so fast thru industrial processes that we need the same kind of speed sucking it back in. Nevertheless, looking at the graph below, reduced carbon emissions are still the biggest player, followed by DAC and the natural processes. We need it all to the maximum extent possible as soon as possible.

But this wildly optimistic scenario still has us peaking at 510 ppm in 2050, high enough to hit 2.0 Celsius warming, which is perilously close to unleashing enough carbon and methane from permafrost and other positive feedback loops to launch us toward 3 or 4 or 5 C warming and create another mass extinction event  (which we know from the past the world will recover from, re-evolving new life forms, in a few million years).

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The graph of CO2 levels below is derived from the assumptions regarding CO2 emissions and removal above. This is a best case scenario.

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But suppose humanity gets past this. Successful implementation of carbon capture and sequestration would mean that Homo sapiens can control the earth’s climate. That brings with it a host of other questions. At what level do we set atmospheric CO2? Do we return to 300 ppm or lower? Who decides? Because carbon released or captured anywhere affects everywhere, who will police it? These are questions for our children, if they are fortunate.

Modern climate change is 10x faster than historic global warming mass extinction events

There have been several mass extinction events in the history of the earth, most of them caused by global warming due to “sudden” releases of carbon into the atmosphere, and it only took an increase of 4 to 5 degrees Celsius to cause the cataclysm. The current carbon emissions rate is 10 to 100x faster than during those events. And we’re already a quarter of the way there in terms of warming.

CLICK TO ENLARGEemissions rate

The current warming trends, RCP 8.5 and RCP 4.5, refer to estimates of carbon emissions under high and moderately low projections by the International Panel on Climate Change. The straight lines on the extinction events are approximate; there may have been episodic spurts and stops as different thresholds, positive feedback loops, and other natural events occurred. But these lines connect the dots we have.

The earth is 4.5 billion years old. Land animals with backbones didn’t really evolve until 300 million years ago (mya), so we’ll start there.

The most massive mass extinction event in the history of the earth was the End-Permian extinction event (also known as the Permian-Triassic extinction event or the Great Dying) 252 mya. It was caused by a massive release of carbon. The equatorial regions, both on land and in the ocean, were too hot for most life forms, including plants. The cause of the warming event is debated, but was most likely due to a series of volcanic eruptions from the Siberian Traps that lasted two million years. The extinction occurred during an initial 60,000 year period, which is “sudden” in geologic terms. Recovery of the ecosystem, basically a whole new evolutionary period to create new animals, took 2 to 10 million years.

The End-Triassic extinction event came next, 201 mya. It was also associated with volcanic activity and the massive release of carbon, this time from the mid-Atlantic ridge. It probably triggered a positive feedback loop, with melting permafrost releasing tons of methane. The extinction period, affecting plants and animals, lasted about 10,000 years and paved the way for the rise of the dinosaurs.

The dinosaurs dominated after that, until all but the avian dinosaurs (the ones that evolved into birds) were wiped out by another mass extinction event 66 mya. This may have been caused by a comet or asteroid striking the earth, or by extreme volcanic activity creating global warming similar to the other events here (8 degrees Celsius over 40,000 years). This one is not shown on the graph.

Finally, there was the Paleocene-Eocene Thermal Maximum (PETM) and associated extinction event 56 mya. Likely caused by a combination of carbon and methane releases, this global warming event is the most recent, offers the most evidence and information, and is most analogous to climate change today. The continents were in roughly similar positions as today. The warming, 5 degrees Celsius in about 5,000 years, wiped out much benthic marine life, pushed the tropics to Wyoming and alligators to the Arctic Circle, warmed oceans to 97 degrees, and made the equatorial regions too hot for many species. The PETM is well-studied, with hundreds of papers available on-line, plus quite a bit of media coverage.

The high temperatures lasted for about 20,000 years. Eventually, the Arctic Ocean became covered with algae. These algae slowly absorbed CO2. When it died, it sank, taking the carbon with it to the bottom of the sea, lowering the carbon in the atmosphere and cooling the earth back to normal. This process took 200,000 years.

Climate change during these past events, considered rapid in geologic time, would have scarcely been noticed by animals on the ground. Animals didn’t go extinct by dropping dead; they just had a lower reproductive rate such that their populations slowly declined until none were left. Also, they evolved. In fact, there was a pulse of evolution during the PETM, producing, among other things, the first primates.

The current warming is 10 times faster than during the PETM. It is noticeable within the lifespan of an individual animal. Adaption thru evolution is not an option. Scientists mince no words:

“We conclude that, given currently available records, the present anthropogenic carbon release rate is unprecedented during the past 66 million years. We suggest that such a ‘no-analogue’ state represents a fundamental challenge in constraining future climate projections. Also, future ecosystem disruptions are likely to exceed the relatively limited extinctions observed at the PETM.”  – Zeebe (2016)

The PETM raised average earth surface temperatures 5 C. We’re at 1.1 C now, with probably up to 2 C already built into the system, meaning we’ll reach that even if we stop all carbon emissions tomorrow. Assuming business as usual, we may reach PETM levels in 140 years.

The international climate report in three diagrams: The world at a crossroads

On October 6, 2018, the Intergovernmental Panel on Climate Change (IPCC) issued its Special Report on Global Warming of 1.5 °C (known at “SR15”), looking at the benefits of keeping global warming under 1.5 °C, as compared to 2.0 °C, and the potential pathways to get there. The report was commissioned after the Paris Agreement of 2015, which subjected nearly every nation in the world to voluntary goals for reducing greenhouse gas emissions. We are already at 1.0 °C and climbing, so this is a late-in-the-game analysis.

The results, based on the latest science, are sobering. While past IPCC reports were known for being rather conservative, largely due to political pressure, this one is more direct, practically screaming for a radical reduction in fossil fuel use (which must fall to near zero by 2060 even with a technological breakthrough in carbon sequestration). When it was approved, participating scientists cried tears of joy that their report, dire as it is, was allowed to be published as it was.

The full report, a little over 1,000 pages, is available in chapters here.  It provides important details regarding the effects of climate change from region to region.

A 34-page summary for policy-makers is available here.

But even that summary is full of technical jargon that most politicians and members of the public would find cumbersome. Here I’ve taken some of the most important diagrams from the summary and modified and annotated them.  Here is the report in three diagrams:

[CLICK TO ENLARGE]

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IPCC2

 

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