General Articles

The Green Key To Sun Power

Even the lowliest weed can turn sunlight, air and water into fuel. Man can’t do it yet, but he’s getting closer

GEORGE H. WALTZ February 1 1948
General Articles

The Green Key To Sun Power

Even the lowliest weed can turn sunlight, air and water into fuel. Man can’t do it yet, but he’s getting closer

GEORGE H. WALTZ February 1 1948

The Green Key To Sun Power

Even the lowliest weed can turn sunlight, air and water into fuel. Man can’t do it yet, but he’s getting closer


WHATEVER you ate today, you dined on stored sunlight. The energy in your breakfast cereal once shone on fields of grain on a bright summer’s day; the animal that supplied you with the meat for your dinner got his energy from grass or corn which in turn got it from the sun.

It’s the same with fuel. The log on your fireplace throwj a pleasant heat that once was sunlight falling on a forest, stored in the wood for your use. If you burn coal, you are enjoying the comforts of sunshine that warmed the earth millions of years ago.

This amazing ability of plants to store solar energy in the form of eatable energy and burnable

energy is one of our world’s greatest: miracles and one of nature’s most well-guarded secrets. It is close to the very secret of life itself, for without the green plant there would be few living things on the face of the earth.

Scientists have a name for this energy-storing process of nature. They call it photosynthesis, which means synthesis with the aid of light. They know that a plant’s leaves are able to breathe in the carbon-dioxide gas that is part of the air and combine it with the water soaked up from the soil through the roots. From these raw materials the plant produces oxygen, which it returns to the air, and sugars and starches. These sugars and starches are the building blocks for the fruits and vegetables which we eat, either directly or indirectly, in the form of roasts and chops from animals who have thrived on the greenery.

But what is the actual process? Just what is the magic that plants use to convert carbon dioxide, water and sunlight into foods and fuels?

For more than 300 years scientists have been striving for the answer. As you read this, an army of plant experts, chemists and physicists in a dozen large research centres in Canada and the United States is spending millions of dollars and hours growing and studying miniature laboratory farms

in their quest for the “green key to life.” Once they find it—and, thanks to some byproducts of the atomic bomb called radio isotopes, they are getting closer to their goal —we may soon know the trick of producing both foods and fuels artificially, directly from the energy of the sun without the intermediate, time-consuming aid of nature’s green leaf!

Few scientists believe that man-made foods will ever replace the garden variety. Except in an emergency, they would be unnecessary and unappetizing. Besides, foods made by any process of artificial photosynthesis without the natural benefits of soil would have to be fortified with vitamins and minerals to make them suitable for human consumption.

Knowledge of just how nature does produce the things we eat, however, would help us to increase nature’s efficiency so that we could get more foods, and perhaps better foods, from every acre of farmland. Nature’s green leaf at its best is able to use only a little more than two per cent of the sunlight that falls on it. If man could add only another few per cent he could double the world’s production of food.

But the real importance of discovering the “green key” lies with

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fuels. By artificial photosynthesis it would be entirely possible to capture and store the sun’s energy just as the tree does and put it into man-made substitutes for wood and coal, and, best of all, into a substitute for the world’s dwindling oil supplies. The fuels we are using today to heat our homes and run our cars and trucks came from the sun by way of the green leaf, but the natural process took millions of years. If we could produce them directly from the sun we could manufacture our fuels as we need them.

How far off is such a discovery? It is hard to say. It might come next month, next year, or perhaps not for many years.

Man’s long search for the secret of the “green key” began early in the 17th century when an inquisitive Dutchman by the name of Van Helmont doubted the truth of Aristotle’s long-standing statement that plants and trees got {ill their needs for life and growth from the soil. Van Helmont planted a young five-pound willow twig in a box containing 200 pounds of dirt that he had thoroughly dried to eliminate the weight of any moisture. To avoid other possible errors, he carefully shielded his giant flowerpot from dust and watered it with natural rain water.

After five years of careful tending and waiting, Van Helmont weighed his tree and then his soil which he had again dried. What once had been a five-pound twig had become a 169pound willow tree—a gain of 164 pounds. The dry soil, on the other hand, had lost only two ounces.

Where had the tree’s additional 163 pounds and 14 ounces come from? It certainly hadn’t come from the soil as Aristotle had supposed. Van Helmont reasoned that it must have come from his daily doses of rain water. As later

experiments showed, water was only one of the major ingredients necessary in the growth of a plant.

Thanks to a long line of scientists including Britain’s Priestly and France’s Mariotte, today’s plant physiologists know that it takes a lot more than just soil and water. They know that it takes the energy of golden sunshine plus a chemical called chlorophyll, which is the green pigment that makes living green things green. They know that chlorophyll is a complex compound consisting of 55 parts of carbon, 72 parts of hydrogen, 5 parts of oxygen, 4 parts of nitrogen, and 1 part of magnesium. They also know that by some amazing process this green chlorophyll is able, with the help of sun power, to take the carbon dioxide gas from the air, reduce it—or deoxidize it—to plain carbon, which is no different from a piece of charcoal and then combine that carbon with the water from the soil to produce food!

But how? Once we know we will have the secret of the green key. We will be able to produce man-made foods and fuels.

The Green-Grass Boys

It was an automobile man, the inventor of the self-starter and our present-day no-knock ethyl gasoline, who helped to start the current fullscale search for nature’s green key. Early in the 1920s, Charles F. Kettering (he prefers the nickname of “Boss Ket”) began wondering about what made plants grow. Always a man to seek the answers to his own questions, he had a greenhouse built near his home on the outskirts of Dayton, O.

In 1929 he built a large, modem science building for Antioch College, in Yellow Springs, gathered about him a group of top-notch chemists, physicists, and plant experts, and formally set up The Charles F. Kettering Foundation for the Study of Chlorophyll and Photosynthesis.

The search for the answer is following three main paths at Antioch.

Dr. Eyster, the laboratory’s plant physiologist, is attacking the problem head on. By a complicated process of grinding, filtering and washing he is extracting the chlorophyll from green leaves—bushels of them to obtain a small sample of nature’s magic chemical—and attempting to trick it into acting the same in his laboratory flasks and test tubes as it does in the green leaf.

The Atomic Approach

A few months ago, Dr. Eyster made a successful step toward harnessing his chlorophyll. He dissolved some of the extracted chlorophyll in acetone (the same solvent used in popular transparent household cements) and got a vivid green liquid. When he poured this over ordinary talc powder he was able to get it to exhibit many of the basic characteristics of chlorophyll in a green leaf.

The next step—and it is a long one— is to inveigle his chlorophyll mixture into absorbing carbon dioxide and getting it to part with its oxygen and combine with hydrogen from water.

Just down the hall from Dr. Eyster’s laboratory, Dr. Paul Rothemund, a microchemist who uses doll-size flasks and tubes and microscopic specks of chemicals, is working to synthesize the complicated chlorophyll molecule, that is, to make it artificially. So far nature has a corner on the chlorophyll market. Man has never succeeded in putting the carbon, hydrogen, oxygen, nitrogen, and magnesium together in just the right way. But Dr. Rothemund has been able to reproduce a portion of it. He has succeeded in synthesizing an important unit in the complicated structure of chemical building blocks that make up the chlorophyll molecule. He calls this portion the “porphin ring.”

In a roof-top shop above these two laboratories, Dr. H. V. Knoor, the third member of the green-grass research team and director of the laboratory, plays with “tagged atoms”

u still another attack on nature’s puzzler. By feeding laboratory plants chemicals that have been “tagged” or marked by making them radioactive, he can trace the wanderings of these chemicals as they are absorbed in a plant. With a Geiger counter (of atom-bomb fame), or any of the other radioactivity indicators, he can chart the travels of any one of his “tagged” chemicals through the leaves, stem and roots. By growing his plants in an atmosphere of carbon-dioxide gas made from radioactive carbon, he hopes eventually to be able to follow the allimportant carbon through each step in nature’s complicated process.

In a small wood building that once housed the first atom-smashing cyclotron, Dr. Melvin Calvin at the University of California maintains a complete radioactive farm to help him in his search for the “green key.” The crops are tiny barley shoots and algae, the simplest form of plant life. His fields are glass dishes and test tubes. The atmosphere the plants breathe contains radioactive carbon dioxide so that the carbon can be traced. Not long ago, Dr. Calvin added another important clue to the solution of nature’s mystery when he found that the process of photosynthesis goes on for a short time after a plant is shielded from the light, indicating that the green leaf is able to store a small extra quantity of energy for use after dark.

So, piece by piece, the puzzle is being put together. Some day, and

it may not be too far off, wfe will know the full secret of the green leaf-—how, with the aid of the sun, it can w’eld carbon dioxide and water into foods and fuels.

When finally we do learn the secret, an unfailing and unlimited source of power will be at our disposal.

To get some idea of just how much pow'er is there for the tapping, just consider the fact that the normal summer sunlight shining on a farm field on a clear day is equivalent to about 653,400 watts of energy for every acre, or the heat value of three quarters of a ton of coal every hour. The total energy converted by all the plants on the earth in 12 hours is about 100 times larger than the heat of combustion of all the coal mined during a similar period!

And yet nature is little more than two per cent efficient. What w'ill man with his fetish for efficiency be able to do when he learns the process of artificial photosynthesis? It is not hard to suppose, or speculate, that a man-made photosynthesis system installed on the roof of a building could supply the entire fuel and power needs of a large factory, office building, or apartment house.

Right now, that’s just a dream, but if the “green-grass boys” can find the answers to Boss Ket’s questions, the days of bottled sunshine won’t be far away and they’ll have pulled off one of the most important research projects since atomic fission. ir