December 18, 2014 - From the December, 2014 issue

CalTech’s Lewis: Rate of CO2 Emissions in Next 30 Years Is Off Charts for Earth’s Planetary History

Nate Lewis is a leading solar energy researcher and chemistry professor at the California Institute of Technology. In 2010, he was named director of a US Department of Energy Innovation Hub, the Joint Center for Artificial Photosynthesis, to prototype new methods for fuel generation using sunlight. TPR presents an edited transcript of his remarks at the November 17 Decarbonizing California conference presented by Climate Resolve, focusing on artificial photosynthesis.


“Energy policy and energy politics are two different things. We have way too much of one and way too little of the other.” —Nate Lewis

Nate Lewis: Energy policy and energy politics are two different things. We have way too much of one and way too little of the other.

Let me tell you about the scale of the problem in terms that people can understand. People can’t relate to barrels of oil and tons of natural gas. They can, however, relate to watts. Everybody knows what a watt is: a PDA or smart cell phone is about half a watt. 1,000 watts is a toaster or a hair dryer (even though my wife thinks it’s my big screen television that causes the problem). 1,000 toasters is a megawatt—that’s a small jet engine. 1,000 jets engines is a gigawatt—that’s a nuclear power plant. And 1,000 of those is a trillion watts, and that’s the worlds electricity demand on average, every second. 

You can’t turn on lights if you don’t have any electricity, like over 2 billion people that live under $2 a day. You can’t cure poverty, disease, or famine if you can’t provide energy to those people to refrigerate their medicines. You can’t cure the fact that humans have always fought wars over natural resources, and there is no indication the future will be any different than the past. 

Actually, energy demand is bigger than electricity demand, and that’s more than a trillion watts. If you add up all of the oil, gas, coal, nuclear, hydro, and everything, and convert it to an energy load, it’s 15 trillion watts. That’s what the world’s energy meter reads right now. That’s almost too big to fathom, but, like it or not, almost all studies show that by 2050 it’s going to double to 30 trillion watts. We need 15-20 trillion watts—somewhere, somehow—to run civilization. And that doesn’t assume that we bring the billions of people that live under $2 a day out of poverty. This is a problem.

We get 85 percent of that from fossil energy. With already proven reserves of oil, gas, and coal, as well as $4 shale gas, we’ve got enough energy to support the expansion of civilization for the next several hundred years. We will not run out of fossil energy, and don’t be fooled—the Stone Age didn’t end because we ran out of stones. But we have run out of air in which to put it all.

If you look at the amount of CO2 that will be emitted into our atmosphere, this is what we did in the last 50 years, based on the historical record for the past 450,000 years.  

On the course that we now are on, we’re going to bring that value off of the chart, up to 550 or more parts per million, if we double our energy demand. It’s also true that year-by-year, from ice core data for 670,000 straight years, temperatures have been highly correlated with CO2 concentration changes, but are not necessarily proven to be the cause. There is only one way to make sure that we will know—to do the biggest experiment that humans will have done with our planet.

We are going off the graph in the next 30 years with a rate of CO2 emission at a magnitude that the planet will have never seen in human history. There are at least six major climate models, and they differ from each other. Therefore at least five of them must be wrong. On top of that, the earth is not on an average path, and climate models are averages of the earth. Because we don’t know the cloud cover 100 years ago day-by-day, and we don’t even know it yesterday day-by-day over the whole planet, you think we can’t predict the weather—well, we certainly can’t predict the climate! 

These climate models are average paths, and the earth is not on an average path. When I hear people say it won’t be bad, or they say it will be awful, my response is that an Ouiji board is not a scientific instrument. We do know that ice is melting more rapidly than the most rapid predictions of it melting, because here are the real data made after all of the predictions. We do understand from bubble release in the permafrost that the so-called runaway train effects, the positive feedbacks, can kick in when you melt that ice. It turns from reflective of sunlight to absorptive; it turns from bright white to dark; it absorbs more sunlight that releases more methane and more trapped gas, and that accelerates the rate of melting to release yet more. 

We know that there is enough methane and other carbon in the permafrost that CO2 concentrations, if it were all released, wouldn’t go up by a factor of 2, they would go up by a factor of 10.  We know that that did happen 230 million years ago in the Permian Era, and we know from the fossil record that between 70-80 percent of all species on Earth went extinct because they couldn’t adapt. We don’t know if this will happen again, but we know we are the only ones doing the experiment to find out. 

Anybody who’s ever opened a bottle of soda noticed that if you add carbon dioxide to water, you make it acidic. The pH of the oceans is lower now than in 4 million years, and probably in 20 million years. We know just from adding CO2 to water what the pH will do. And we all know the pH ranges historically over which coral reefs can survive. It’s a relatively narrow range because as the waters get too acidic, the minerals of corals dissolve. 

We also know from volcanic eruptions that have acidified the oceans previously how long it takes to re-neutralize that, and unlike the air—where if you add CO2 to the air it only takes 3,000 years to equilibrate—comparable to modern human history, we know the oceans reverse acidification in 2 million years. If you feel really good about acidifying the oceans of our planet for the next 2 million years, then be my guest and drive your SUV. 

You have to look at the physics of the planet on which we live. If we need 10, 15, 20 trillion watts globally, then we can do it by nuclear power. That’s the only proven technology that we have to meet that demand. 

But as I already told you, nuclear power plants that are built safely are against the law, essentially, in our state. Regardless, at the safe limits, we build them at about 1 billion watts—a gigawatt—that’s about what each of the two San Onofre domes were producing at steady state. Well, a billion watts sounds like a miraculously large amount of energy, but if you need 13 trillion watts, then quick math shows you need to build a nuclear power plant somewhere in the world every single day between now and 2050, in order to meet demand by then. And since they only last for 40 years, then you have to keep building one a day forever somewhere in the world. 

If you think you don’t want to do that, then you have to look at what nature gives us to survive. No matter how you twist the numbers—and wind is the most economical, fastest growing renewable energy resource, and should be used where we can exploit it—in the end, there is only one big source. That’s the sun. 

The sun gives us 120,000 terrawatts; every other number is tiny compared to that. That doesn’t mean you can’t locally do fine with a local solution, here and there. But globally, the laws of physics say that more energy from the sun hits the earth in one hour than all of the energy consumed on our planet in one year. Nothing else comes close. 

But we have a little problem. The sun has this one little nasty habit—it goes out every single night. He that cannot store shall not have power after four! Gerald Ford said as president, when asked why we did not do more solar in the United States during the oil crisis of the 1970’s, “Well, you know solar energy just isn’t something that will come in overnight!” 

You can’t build an energy system around an intermittent resource that goes out every night, and the wind doesn’t blow every night, and there is not enough reliability to fill solar with wind or vice versa. You need to store. Nature figured that out a long time ago—that’s what plants do. They store the energy from the sun in chemical fuel—the densest form of energy known to man other than the nucleus. 

The real problem with electric vehicles is the batteries and the energy density in the batteries. In the best batteries, the energy density is 200 watt-hours in a kilogram. The energy density of gasoline is 12,000-watt hours in a kilogram; you don’t need to know anything more to know why you’ll be range challenged in an electric car. Averaged over the years, less than one percent of the sunlight that hits the fastest-growing plants in photosynthesis/biofuels is stored at all as energy. 

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But this is an inevitable technology because someone’s going to figure out how to take the biggest source we have—the sun—and store it in a dense form, which is chemical fuel. 

So why don’t we do that? Our job is to do what nature did, but without using its chlorophyll. 

We’re going to build our own pieces and make our own fuels, and make it 10 times more efficiently than the fastest growing plant could ever do, and make a fuel we can use into our normal drop-in infrastructure so you won’t know the difference. 

This solves the two biggest problems down the road, which are always cited in a zero-carbon, clean energy economy. 

One is massive grid storage to compensate for the intermittency of renewables. The other is the fact that 40 percent of transportation globally cannot be electrified. There is no such thing as a plug-in hybrid airplane, and so we have to figure out a way to make carbon-neutral transportation fuels that doesn’t stress biofuels for food systems. Artificial photosynthesis would solve both of those problems at once.

Artificial photosynthesis actually works! You can take minerals—like this one, strontium titanate—and shine sunlight on it, and you actually split water into hydrogen and oxygen, directly. No wires, no bugs, no algae, no plants—this already works more efficiently at converting all the wavelengths of sunlight and all its energy into the chemical bond stored in the hydrogen than the fastest growing plant. So we know its possible to get this plane off the ground! 

But after 40 years of working in various labs and small efforts around the world, we found there are three things you want: you want it to be cheap, you want it to last a long time, and you want it to be efficient, so you don’t have to cover lots of land. Right now we can give you any two but not the third at the same time. 

What we’re doing is building a high performance rain jacket fabric. You’ll be able to roll that fabric out, and instead of collecting rainwater it will take rainwater, or water from the air, and sunlight, just like a plant does, and make fuel for your cars. It actually works. It works right now in Pasadena today. It didn’t work four years ago when we started our project. 

We decided that we would borrow a page from nature, but improve on it. Instead of making a continuous material like a solar panel that would be black and absorb sunlight, we wanted two colors—one would appear red to our eyes, and it would let through the other colors, and then the one that looked blue so that it would absorb the red. That way, we would get more energy from the total rainbow of the sun than making it all reduce to one energy, which is what a solar cell does.To make fuel we need 1.23 volts in order to drive our electrolysis, or fix CO2. We can’t make half a volt like a silicon solar panel makes and have any reaction at all. We need to string them together. 

The second thing we needed was a very long structure. We had a lot of land to absorb sunlight, but we didn’t want the electricity to go all the way back to the top the way it came, because then the material has to be very pure—if along the way it finds a defect, it only makes heat. This is why solar panels cost so much money—you have to make them the purest thing any human will every touch. That solar panel that you put on the roof is pure to the part-per-trillion; if you don’t make it that pure, if doesn’t work well or maybe at all.  

We don’t like that, and the perfect solution is to make a long axis to absorb the light and let the excited electrons go through a skinny short axis sideways. Nature figured this out a long time ago—this is exactly what a forest of Aspen trees does. They are very tall to absorb the light, but the forest has narrow trees to move the slower, heavy nutrients sideways over a short distance so they can get nourishment to the tree. 

We built a forest using micro technology of these microfibers of our little solar absorbers. We use material that is much cheaper than you could ever use in a solar panel, and we use it to our benefit in this architecture. 

If we string these two things together, then the top makes oxygen, which is vented to the air—after all, photosynthesis is the source of all of the oxygen in our atmosphere. Then we want to make a reduced fuel on the bottom side of a separator. 

We built our first prototype. We built that real membrane. This is a real microfilament, in this case of silicon, that we grow in our laboratories that absorbs sunlight over the long axis and moves those carriers sideways. We develop catalysts that replace the expensive platinum that would be used to make hydrogen with really cheap metals like iron and cobalt. We developed other catalysts to make oxygen, and we are now putting the pieces together. 

Finally, I’ll just say we have about 150 really smart people working all the time on this problem, and we’re going to actually get a lot of progress in demonstrating we can get this plane off the ground. 

That doesn’t mean that tomorrow you’re going to buy the first product manufactured, and it doesn’t mean that there aren’t a whole lot of things that we could and should be doing to avoid that scenario that I showed you in the first part of the talk. 

It does mean that this is a bridge to build to the future that, if we want to be able to cross, we should be laying the groundwork to do so right now.

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© 2020 The Planning Report | David Abel, Publisher, ABL, Inc.