Negative carbon emissions, or the concept of the Earth’s system absorbing more carbon annually than is emitted through human-related activities, is becoming a topic of greater discussion as one of the options available for addressing climate change. John Deutch of MIT and Arun Majumdar of Stanford University published a commentary in Joule reflecting on research opportunities for carbon dioxide utilization and negative emissions at the gigatonne scale.
In a conversation with MIT Energy Initiative Director of Research Francis O’Sullivan, Deutch and Majumdar discuss potential technology and policy pathways for negative emissions, and the importance of focusing on gigatonne-scale solutions.
John Deutch, Institute Professor Emeritus at MIT and former director of the Central Intelligence Agency. Deutch is also a former Chairman of the Department of Chemistry, Dean of Science, and Provost at MIT.
Arun Majumdar, Jay Precourt Professor of Mechanical Engineering at Stanford University. Majumdar is also Co-Director of the Stanford Precourt Institute for Energy.
On the origins of the Joule commentary piece:
Arun Majumdar: This commentary is a shorter version of a much longer report that the former Secretary of Energy, [Ernest] Moniz, asked his advisory board to put together. John [Deutch] was the chair of that advisory board, I was the vice chair, and we put together a task force to address this particular issue. The question that he asked is, “What are the research opportunities that we need to focus on today, or in the next five to 10 years, that have the potential to make a gigatonne-scale impact on our carbon emissions? Especially that has a commercial impact in the form of some kind of a CO2 utilization and negative emissions?” That was basically the genesis of the whole report. That report got finalized in December. We thought that, for the sense of brevity, and for people to read it, it may be a good idea to put a commentary together, which is what this commentary is all about.
On reducing greenhouse gas emissions to levels that could avoid the worst environmental and economic impacts of global temperature rise and climate change:
John Deutch: If we can’t do it by reducing emissions, we have to turn to doing something else. Indeed, that is negative emissions, or some kind of utilization of the carbon dioxide on, eventually, a commercially acceptable manner to help join with the reduction in emissions to avoid the increases in global temperature. That’s a very important point. The study presupposes the need to do much, much better at both CO2 utilization and negative emissions. That’s very important, and I don’t think widely yet internalized by the scientific community, certainly not in the Paris Agreement. It’s unlikely that the globe will be able to manage to avoid deleterious climate change without other measures than just reducing emissions. […] If you don’t go to the level of gigatonnes, then you might as well forget about this, because it’s not going to make a difference to the amount of CO2 that’s being emitted per year.
On sectors with large carbon footprints that could achieve gigatonne-scale reductions in CO2 emissions:
AM: We do emit 40 gigatonnes of greenhouse gas emissions per year. A gigatonne is a billion tons, which is a trillion kilograms. One gigatonne is equivalent to roughly 200 million elephants. One gigatonne. And we produce 40 gigatonnes per year. So this is a big, big number. As John pointed out, this is a gigatonne scale problem, and we need gigatonne scale solutions. Now, what we recommended was not the research be done at the gigatonne scale, but at a much smaller scale, in those topics that have the chance of going to the gigatonne scale. That’s really the premise of the whole report. Let’s not waste time on things that are unlikely to scale to the gigatonne scale, but only focus on those that are relevant. In that, we focused on a few things that we brought out in this report. One was to look at agriculture. We cycle about 120 gigatonnes of carbon per year. We emit back about 118, keeping only about two gigatonnes of carbon in soil. If you could just tweak that a little bit through R&D on plants, crops, or forestation, this could be a very, very big deal. That’s just one option. There are a few other options.
When you’re doing things at the gigatonne scale, it’s very important to take a holistic view of what the consequences could be. Because it is engineering at the geo-scale. We recommended that the consequent analysis or understanding of the systems view be part of the R&D. Because it’s very difficult to know a priori what the consequences will be. Some of the effects, in fact, most of the effects, are highly non-linear. They’re not easily predictable. […] One thing is for sure, if you’re looking at gigatonne scale solutions, then you ask the question, “How many industries today are at the gigatonne scale?” The answer is, not too many. It’s oil, gas, coal, steel, concrete, and agriculture. That’s about it. If you are to solve this problem of climate, these industries ought to be part of the solution and not part of the problem. That’s a very important statement that we make in this report.
On potential topics for R&D focus:
JD: Two pathways which I think have attracted the most attention from serious scientists has been either the water splitting from the sun—splitting water into hydrogen and oxygen—the other one is artificial photosynthesis. Both of those would indeed be a pathway that avoids using energy that has carbon emissions associated. It would be renewable and clean energy. Those have been looked at for a very long time. Quite a few decades.
AM: A lot of people think hydrogen is for fuel cells or transportation. Actually, we think that may not be the biggest application of hydrogen, because if you want to do something with CO2 to make a hydrocarbon, whether it’s in a fuel or chemicals or plastic, you need hydrogen. And that hydrogen can come from water. To achieve water splitting, you need energy and it ought be carbon-free energy. This is most likely renewable energy because it is becoming the most inexpensive. For hydrogen production to be cost-effective, the cost of renewable energy is a boundary condition and we see that boundary condition to be reasonably inexpensive to produce hydrogen cost-effectively.* While the boundary condition is necessary, it’s really not sufficient. What we emphasized in our report is there are several pathways to produce hydrogen.
On how to finance trillion-dollar-scale investments in negative emissions solutions:
JD: A personal view is that the size of these projects means they’re either going be done by states that have simple governments—by that, I really mean, effectively, China or Russia, maybe a few of the Middle Eastern states—or they’re going to be done by the private sector. To believe that progress can be made on this though OECD governments financing it, and I might say, managing it, in my mind, is really not looking at what the history has told us about such efforts. Now, something like ARPA-E, which [Arun created], is important because it takes you beyond just a lab or a bench scale, to more of a technology possibility, but is far from technology demonstration of something at the gigatonne scale. I would say that if you need to go to that next step, and we will, then you need to have the involvement of the private sector and really put it in the hands of the private sector. For that you need a stable and understood policy framework, including a cost on carbon.
On the prospects of achieving a carbon solution within the next 60-70 years, incorporating a negative emissions strategy:
JD: I’m very unhappy with the progress that the United States is making, and more importantly, that the globe is making in really changing the energy future of the world and the penalties that will come for not dealing with energy in a more responsible way. I’m fairly pessimistic. I would say 20 years from now, [it will be] very similar to today. If you say, “Well, how is it different today from 20 years in the past?” I don’t believe there’s been a lot of change, if you compare it to 1998.
AM: This commentary is a call to action. To raise the profile so that this is now felt not only by the renewables industry, but, frankly, all the other industries. As I said, if you have a gigatonne scale problem and you need gigatonne scale solutions, it’s a handful of industries that can actually reach that scale, and it’s really a call to action to those industries. I would say, the oil and gas industry has realized that this is a challenge and they ought to be part of the solution. From what we’re seeing, I think they have come to that conclusion. They have also been nudged by some of the investors, some of the shareholders, and stakeholders to move in this direction. I think we are starting to see that happen. Again, is this fast enough? Not yet. Can it be done? Can it be fast enough? Absolutely. But certainly, if you align the business incentives, the policies to make the business incentives and the return on investment aligned, then I think we’ll see acceleration. It’s not quite there yet.
* Added after the interview for clarification and not part of the original audio.