Forty years ago, we chose this day in April to express our concern for the state of the planet.   At the time, people were worried about air pollution, water pollution and the threat that the “population explosion” was going to overrun the planet’s resources.  Where energy was concerned, we worried instead about fouling the air with fossil fuel pollution, drowning precious landscapes by building Western dams, and possible oil scarcity.  

So we’ve made a lot of progress.  We’ve certainly reduced air pollution.  Our cars are about 98 percent cleaner in their overall emissions than they were 30 years ago.  The air in our cities is also much cleaner – for example, sulfur dioxide emissions have cut in half since the 1970’s.  Our rivers are no longer industrial sewers as we have improved management of storm water runoff and enhanced our water treatment capabilities.  Municipal waste is being treated, fish populations are bouncing back and we are making real progress restoring our waterways.  But we can all agree that there is more to be done.   

There’s one more thing worth remembering about the first Earth Day and that is that, at the time, the Sierra Club and other environmental organizations were supporting nuclear power.  In fact, nuclear energy was regarded as a savior to our environmental dilemmas.  It cleaned the air of pollution and didn’t take up a great deal of space.  You didn’t have to drown all of Glen Canyon to produce 1,000 megawatts of electricity.  With nuclear power, you could do it on one square mile.  But that support from the environmental community quickly disappeared and we haven’t started a new nuclear power plant in 30 years – mostly as a result of the fear perpetuated from the incidents at Three Mile Island and Chernobyl.

Today a lot of environmentalists are starting to rethink nuclear energy.  President Obama himself has endorsed it, proposing an expansion of the loan guarantee program and making the first award to the Vogtle Plant in Georgia.  Secretary of Energy Steven Chu wrote recently in The Wall Street Journal about developing a new generation of mini-reactors in this country. 

Now, I know a lot of environmentalists feel betrayed by this.  “We laid nuclear to rest twenty-five years ago with Three Mile Island and Chernobyl,” they say.  “Why is it now crawling out of its grave?”  For many people, nuclear is the exact opposite of “green.”  They say it’s big, it’s industrial, it’s bureaucratic, it’s expensive, it involves handling dangerous materials, and it’s not soft and nice and sustainable like those energy technologies we admire.

So why would anyone consider nuclear green?  The main thing is its tremendous energy density.  The Nature Conservancy took note of this last August in their paper on “Energy Sprawl.”  The authors looked at the amount of space required to produce energy from the various technologies – something no one had ever done before.   They came up with some remarkable findings. 

Nuclear turns out to be the gold standard.  You can produce a million megawatt-hours of electricity a year – that’s the standard they chose – from a nuclear reactor sitting on one square mile.  That’s enough electricity to power 90,000 homes.  A coal-powered plant absorbs four square miles when you count all the land required for mining and extraction.  A solar thermal plant, where they use big mirrors to heat a fluid, takes six square miles.  Natural gas takes seven square miles and petroleum takes 17 – once again counting the land needed for drilling and refining.  Photovoltaic cells that turn sunlight directly into electricity take 14 square miles and wind is even more diluted, taking 28 square miles to produce the same amount of electricity.

These are some pretty big numbers.  When people say “We want to get our energy from wind,” they tend to think of a nice windmill or two waving gently on the horizon.  “Maybe I’ll even put one in my back yard,” some might think.   They don’t realize those nice, friendly windmills are now up to 50 stories high and can have blades with a diameter the length of a football field.  They are loud and can make a low-decibel noise heard from miles away and can also kill a lot of birds – up to eight per windmill per year according to the American Bird Conservancy. 

It’s the same for photovoltaic solar panels.  We would need to cover fifty square miles of desert in order to equal the output of one nuclear plant.  And then there will be hundreds of miles of transmission lines to bring this electricity from remote areas where it is generated to the cities where it is needed.  At some point this stops being picturesque and begins to look like what good environmentalists and conservationists have always fought against – the destruction of natural landscapes by industrial civilization.

These are things we can’t just brush aside.  We don’t want to end up destroying the environment in the name of saving the environment.  Just as there is no such thing as a free lunch in economics, in nature there is no such thing as free energy.  Anything we do is going to affect the environment.  No matter how “green” and “sustainable” we may want some form of energy to be, it’s going to have an impact.   The real question is which form of energy has the potential to have the smallest impact?  I think the answer is “nuclear power.”