18: Atmospheric Carbon Extraction Scope, Available Technologies, and Challenges
- Page ID
- 41714
\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)
\( \newcommand{\dsum}{\displaystyle\sum\limits} \)
\( \newcommand{\dint}{\displaystyle\int\limits} \)
\( \newcommand{\dlim}{\displaystyle\lim\limits} \)
\( \newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\)
( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\)
\( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)
\( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\)
\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)
\( \newcommand{\Span}{\mathrm{span}}\)
\( \newcommand{\id}{\mathrm{id}}\)
\( \newcommand{\Span}{\mathrm{span}}\)
\( \newcommand{\kernel}{\mathrm{null}\,}\)
\( \newcommand{\range}{\mathrm{range}\,}\)
\( \newcommand{\RealPart}{\mathrm{Re}}\)
\( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)
\( \newcommand{\Argument}{\mathrm{Arg}}\)
\( \newcommand{\norm}[1]{\| #1 \|}\)
\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)
\( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\AA}{\unicode[.8,0]{x212B}}\)
\( \newcommand{\vectorA}[1]{\vec{#1}} % arrow\)
\( \newcommand{\vectorAt}[1]{\vec{\text{#1}}} % arrow\)
\( \newcommand{\vectorB}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vectorC}[1]{\textbf{#1}} \)
\( \newcommand{\vectorD}[1]{\overrightarrow{#1}} \)
\( \newcommand{\vectorDt}[1]{\overrightarrow{\text{#1}}} \)
\( \newcommand{\vectE}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{\mathbf {#1}}}} \)
\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)
\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)ROGER AINES Lawrence Livermore National Laboratory
- Explain the concepts of negative emissions and carbon dioxide removal from the atmosphere—why do we need them?
- Describe why reducing emissions of greenhouse gases will not be enough to reach our climate goals. You will understand the amount and timing of negative emissions—removing CO2 from the atmosphere—that will be needed.
- Define what it means to remove CO2 from the atmosphere, and what we will do with it to keep it out.
- List four ways to remove carbon dioxide from the atmosphere and what steps need to be taken to make that removal permanent. You will be able to list the potential costs and volumes of those methods, as well as one potential drawback for each approach. Along with these you will be able to list the accompanying ways to store the CO2 permanently.
- Describe the idea of recycling CO2 to make carbon-based products, instead of using oil.
- Describe two products that could be made from CO2 instead of oil. One of the important sources of residual emissions—CO2 emissions that are very hard to remove from our economy—is the carbon-based products we use every day.
- Describe how engineered systems remove CO2 from the air, and identify what their limitations are.
- Describe the reasons why engineered systems might be important and how they can be used to clean up the atmosphere. Engineered systems are different from natural-based systems like forestry and soil carbon.
Overview
Even after we electrify everything, we will still need to clean up the atmosphere. This is because we have been too slow to implement clean energy technology, and some greenhouse gas emissions will be very hard to ever stop, like carbon dioxide from airplanes. In this chapter I discuss the size of this negative emissions challenge and a series of technical approaches we can use to accomplish removing CO2 from the atmosphere at a scale of billions of tons per year.
The need to remove carbon dioxide from the atmosphere in order to stay well below 2°C total temperature rise is widely accepted today. The climate models can tell us how much CO2 needs to be removed, and the economic models can tell us how fast changes can be made to existing systems, but the details of these massive new technologies are not well constrained. In this chapter I describe our current understanding of the general classes of technologies, but it will be up to you, today’s students and tomorrow’s leaders, to establish the details and implement those technologies. You will find that there is considerable uncertainty about exactly which approaches will be the most useful— will reforesting poorly used land be the most critical? Will new, as yet untested, approaches come to the fore? All we can say at this point is that there is no obvious silver bullet, and prudence indicates we should develop and test as many approaches as possible.
Negative emissions methods can be divided into natural solutions, such as increasing forested lands and improving carbon levels in soils, and engineered solutions, such as machines that directly remove carbon dioxide from the atmosphere. In between those extremes are hybrid solutions, such as making biofuels and capturing the CO2 emitted during that process or speeding up the natural weathering of rocks that removes CO2 from the air.
All of these approaches require land, and often large amounts of land, either for the technology or growing areas, or for the renewable energy systems to power the more engineered solutions. The trade-offs that will have to be considered are large. Will we turn areas of desert over to solar power to run direct air capture? Will we plant crops, purely to capture their embedded CO2? And where will we store the CO2 removed from the atmosphere? Plants and soils can take up some of it, perhaps a lot with time, but in the short run it is likely that much of the fossil-derived CO2 in the air will have to be returned to rocks deep beneath the earth. I try to balance these multiple options and give you a sense of the technology development, societal choices, and energy issues associated with cleaning up the atmosphere.
A major issue is how we will pay to achieve these goals. California’s current efforts to reduce emissions now include the first mechanisms to pay for negative emissions. I conclude the chapter with an explanation of California’s Low Carbon Fuel Standard and how it informs us about ways that we can develop and encourage negative emissions technology development.