By William McDonough and Michael Braungart, Source: Scientific American

Excerpted from The Upcycle: Beyond Sustainability—Designing for Abundance, by William McDonough and Michael Braungart. Copyright © April 16, 2013, North Point Press.

Food as a battery—that is what we would like you now to consider. But before we get to the full expression of that proposal, we need to review exactly how batteries function, so you can appreciate the beauty, and potential innovation, made possible by thinking through this metaphor.

Batteries are not storage containers for electricity, as one might assume. They don’t provide power because somehow someone pumped in the electricity and locked it in, and now it’s ready for use. Instead, they contain the potential for an electromagnetic reaction, which, if engaged, creates power. The battery consists of a negative solution (the anode) and a positive solution (the cathode) separated by the ions of the electrolyte. The extra electrons in the anode want to move to the cathode, but there is no path through the electrolyte between them.

When a wire connects the negative end to the positive end of the battery, the electrons can flow through the wire, seeking their harbor in the cathode. These free-flowing electrons, in the middle of that path, power your flashlight or start your car.

The beauty of a battery is that it is potential energy, ready for your use, when and where you need it. Should the battery run out of charge, its power is recharged by reversing the process, forcing the electrons from the cathode into the anode. Then you can start again using your battery to provide electricity.

Now think of how humans conventionally create energy. We burn fossil fuels—i.e., carbon-based organic compounds (as we have said earlier, fossil fuels are ancient organic compounds)—and inadvertently turn them into carbon dioxide, among other things.

Photosynthesis is an electromagnetic reaction that frees electrons from water to turn carbon dioxide into organic compounds.1 It is the reversal of the burning of fossil fuels. It is recharging the battery. It is recharging our power source. If people don’t allow the recharge of that battery, the world can’t recapitalize.

If one looks today at our organic battery, this biosphere, which has provided all the energy that people have used for their needs for millennia (the fossil fuels in coal and oil; the biofuels in wood), one might begin to understand the importance of recharging. Human beings have every reason to want to do so.

Get Down to Earth

Let’s look at the common worm. As a worm makes its sinuous way through the soil, it aerates, tills, plows, and fertilizes. Of course, it doesn’t intend to do these things, but it seems to have been designed, by nature, to have beneficial effects in the course of every single thing it does.

Worms are avid consumers. They eat their own weight in food each day. Yet they are enormously helpful to ecosystems (our use of “yet” indicates how much people have come to associate “consuming” with destruction and waste, which is certainly not the case in nature). Worm castings—what they leave behind—are “waste” only for a moment before they become “food”: These castings are rich in nutrients, extremely rich—they contain higher levels of nitrogen, phosphates, and potash than the soil around them. The lowly earthworm is one of the planet’s most valuable creatures (and apparently one of Darwin’s favorite organisms).

Compare this highly effective and evolved interaction with soil to humanity’s most recent interactions with soil. Humans have the capacity to be similarly effective as earthworms. One way is to add nutrients, and we could easily do so, but so far, for the most part, we aren’t.

How can we do this? The history of the development of the technical battery over time has been one of experimentation with various substances to sustain the longest charge and promote the most powerful chemical reaction needed to create the flow of electrons; to reduce the size and cost of the battery while optimizing the duration of its energy output; and to create specific batteries for specific products and needs.

To translate this to the earth battery: We might create farming techniques that sustain the longest period of productivity, augment the soil for optimal plant growth, utilize soil in the most compact way, and diversify the design of that growth for different locations.

Right now in human history, we have designed and implemented a system that puts us in danger of expending our earth battery. Carbon is not treated as a valued asset by human industry. People do not feed the soil. Since the founding of the United States, the country has by some accounts depleted 75 percent of its topsoil. Most of this loss is caused by now questionable modern agricultural techniques—monoculture (growing one kind of crop year after year, so the same nutrients are siphoned out), overtilling (which encourages topsoil to become airborne and erode), and salinization of soil caused by overwatering and overuse.

One hundred and fifty years ago, the Iowa prairie had 12 to 16 inches of topsoil, as well as the carbon stored in the deep roots of prairie plants, which were as much as 15 feet deep. Now the topsoil is down to 6 to 8 inches. Soil production takes significant time; it can require from 100 to 500 years to create one inch of topsoil. With those kinds of numbers, human beings have little to no hope of catching up.

We are frittering away our future food. Some estimates for the United States show that 6 percent of wheat and corn production is lost for every inch of topsoil that disperses into the air or water. Or to put it in other terms, the United States is said to lose $125 billion worth of topsoil a year.

The problem is occurring around the world. The United States loses topsoil 10 percent faster than it can replenish; China and India are at rates of 30 to 40 times faster.

The quantity of loss isn’t the only problem. People are also depleting the richness of the soil that remains.

Norman Borlaug, the agronomist known as “the father of the green revolution” who won the Nobel Peace Prize in 1970, came up with revolutionary ideas about hybridization to optimize grains for higher yields. The Nobel selectors credited him with saving more than a billion people from starvation. But those green revolution concepts have now inspired industrial farming to escalate hybridization and genetic modification to the point that they are selling an herbicide to kill weeds and then crop seed that can resist the herbicide. The farmer is buying at least two different products—seed and herbicide—from the same corporation. Farmers have also become more dependent on soil additives, such as phosphate, which are customarily mined, requiring the farmers to go far afield—and certainly far from the field, even to distant lands—to maintain high local yields.

The green revolution has been enormously productive, but its focus has essentially been on gleaning energy from the battery without considering the optimized design of the organic battery, for how to maintain the charge. We think that human beings can be doing more to recharge their local earth.

Soiling the Planet: Give Back

The second thing we can do for our earth battery is optimize the soil to encourage electron exchanges. We can improve plant life’s access to needed nutrients in soil.

We are extremely interested in the alternate green revolution launched when Sir Albert Howard published his seminal An Agricultural Testament in 1940. He was an agronomist sent by Britain to India to inform the farmers about Western farming techniques. To his surprise, he found the Indian farmers functioning quite well. Their agricultural systems were focused not just on optimizing specific plants but on maintaining soil health—and, more specifically, on devising systems to sustain the microbacterial matter in the soil. One example: The Indian farmers were able to return difficult-to-break-down straw to their soil by putting it on their roads, crushing it with farm wheels, and mixing it with manure. Howard’s insights introduced the idea of modern composting and led to the beginning of the organic agriculture movement.

These advances play out today. As just one small example, Gary Zimmer, of Midwestern Bio-Ag, advises more than 3,500 farmers working approximately two million acres of farm—primarily in the Midwest, but reaching as far as Idaho and Pennsylvania—to build productivity from the soil up. He looks first at what the soil on each farm needs in biological nutrients. His techniques may create yields slightly lower than those created by the big agricultural companies, but the cost in soil amendments is also lower, so the profit can be higher. For farmers around the world, the idea of lower costs with higher profits probably sounds appealing. It’s common sense.

Our point is this: Many people believe that the next green revolution will be an offshoot of the Borlaug revolution—that it will come from optimized and modified seeds and plants, and certainly those developments will continue. But we believe the next green revolution may come from the soil. In other words, it may come from people trying to execute the optimization of the battery—the way the earthworm does. And all of this will be further amplified by greenhouse techniques such as hydroponics.

Phosphate: The Next Fossil Fuel War

Phosphate is one of the key ingredients in soil, in how the earth recharges itself. Plants require phosphate to grow. Animals, including ourselves, need phosphate for bones, teeth, and membranes—and we get that mineral from our food. Plants, clearly, get their phosphate from the soil, and in nature’s system they would return the phosphates to the soil when they die and decompose (or are redeposited as animal waste).

But humans have been implementing less-than-optimized practices. Through farming, people are removing high levels of phosphate from the soil—the plants take up the phosphate and are then carted off, leaving no remnants behind to “reseed” the organic phosphate.

Human beings also put the phosphate available in soil out of reach by overwatering. This does not dilute phosphate; it causes it to bind to other elements before the plants can uptake the phosphate in a form useful to them. In fact, the phosphate binds with so many other elements—silicates, carbonates, sulfates, and the like—that it can be a tricky nutrient to add to soil. One gardener has compared it to throwing a monkey through a jungle. The monkey’s tail and arms and legs catch on so many vines and tree limbs that it can’t get through.

The current solution to reintroduce phosphate to the soil involves dumping mined phosphate onto fields. But because phosphate links to so many other elements, it easily washes out of the soil and into groundwater, where it leads to the high nutrient content in lakes and rivers that subsequently creates algae blooms, killing off fish and aquatic plant life. Mined phosphate also tends to include radioactive elements, such as uranium, radium, radioactive lead, radon, thorium, polonium, and cadmium, because these are inescapable trace elements in phosphate ore extraction.

Plus, there is a geopolitical conundrum in the use of mined phosphate. The top two exporters of phosphate in the world are the United States and China, followed by Morocco. But in 2010, China, recognizing the importance of phosphate to its own agricultural needs, slapped a temporary 110 percent tariff on exporting phosphate at the cusp of the spring planting season. That left the United States exporting its dwindling supply. At current rates, the United States’ supply is estimated to be depleted in 30 years. That means the United States will be dependent on imports from Morocco or China—which could get expensive as tariffs fluctuate—much as nations are dependent on imported oil.

To come up with a solution for this phosphate requirement might sound like a daunting challenge, but the solution is not out of our reach. In fact, we all get to the bottom of it every day.

Before we talk about the solution, though, we need to introduce a concept that will prepare you for the revelation: Sometimes in order to make a new idea acceptable we also need to upcycle the language.

Take, for example, an impressive effort that San Diego, California, began in 2007 to study “recycling” sewage water to address the city’s very real water shortages. In the absence of an official name for the operation, journalists started calling the reclamation effort Toilet to Tap.

Now, it’s hard not to see the yuck factor in that phrase. And, unsurprisingly, San Diego citizens balked at the idea of consuming their own wastewater. It didn’t matter that the recycled water, after being sent through the purification process, was in fact cleaner than the water San Diego residents were currently drinking. No one wanted to think about toilet water in his or her drinking glass. Sydney went through a similar experience during the droughts there.

Singapore, on the other hand, had its water-recycling pitch well-tuned right from the start. When conducting feasibility studies on technology for reclaiming water, they called the project NEWater. With that nice, refreshing term, citizens were inspired to take pride in the idea that they were being endlessly resourceful; NEWater now accounts for 30 percent of the country’s water needs. Upcycling allowed Singapore to stop importing water (from Malaysia, which they had been doing for years, despite constant political friction), bringing greater safety and security.

Keep that issue of language in mind while we reveal something that we think would go a long way toward assisting how humans interact with nature.

In the Western world, for more than a century, people have been misled into thinking that our “waste,” what we flush down the toilet, is somehow toxic, that it cannot be worked back into the natural system, that it cannot be used as compost for growing plants. This is not true. Your waste is manure as helpful as any other manure on the planet; it just has to be handled correctly. Your urine, over a 24-hour period, contains half the phosphate you will need to consume in a day for healthy bones and teeth and tissue.

For millennia, people understood how helpful our own “emissions” could be. When Bill was a young child in Tokyo, he would hear the farmers coming through the streets when everyone else was in bed, using their “honey wagons” drawn by buffalo to collect the night soil (human waste gathered from cesspools and privies, for use as manure). At that time, people could buy such “waste.”

Japanese required intense cropping, and where else could they get their phosphate? It doesn’t just rain phosphate.

The Japanese were sensitive to the handling of pathogens, and they knew how to compost the night soil before they used it on plants. But the way humans treat “waste” now is to call it sewage and chlorinate it, then dechlorinate it with sulfur. Some systems use ultraviolet disinfection. All these processes require tremendous energy loads, about 4 percent of the United States’ total electricity expenditure. And the “waste” still ends up going back to pollute the larger water system, along with runoff from septic systems.

We could change what is essentially grave mismanagement. Humans can upcycle sewage. Stop thinking sewage and start thinking nutrient management. Stop thinking ugly, smelly liability and start believing the old adage money doesn’t stink. In fact, that expression from the Latin, Pecunia non olet, came from the Roman emperor Vespasian, defending the unsavory nature of his tax on public urine. Roman citizens bought urine to tan their leather and clean clothes and were taxed accordingly. When Vespasian’s son expressed his repulsion, the emperor held up a coin and asked if it smelled bad. The son replied that it did not, and Vespasian pointed out that it was earned from urine. Money doesn’t stink.

As with Singapore water, the yuck factor will dissipate by not only changing a term but also realizing the immense profitability of reusing our biological nutrients. We are encouraging cities like San Francisco and countries like the Netherlands and Sweden to convert sewage into valuable products like phosphate and nitrogen.

A company in Vancouver, British Columbia, is developing ways to recover phosphate from human waste. An engineer at the sewage company had been studying the problem of waste pipes clogging due to the crystallization of minerals in the pipe—a liability. The engineer attempted to get the crystallized mineral out, but this proved very hard, literally, because the minerals were stonelike. So the engineer came up with a mechanical device and a small chemical intercession. The mechanical device created a vortex, a swirl, spinning the water so the minerals wouldn’t cling to the pipes. What happened then? The minerals came out as pearls—of phosphate.

These pellets of magnesium ammonium phosphate are known as struvite, and for farmers they’re ideal because they release their nutrients slowly, taking about eight to nine months to fully dissolve. They feed into soil at a pace that plants can digest. And the farmers don’t have to keep laboring to add phosphate since, for eight to nine months, they know the fields have their fill.

The sewage treatment plant, which had defined sewage as a problem to be contained, could now become a nutrient management system, capturing phosphate to feed soil. Yesterday’s cost became today’s coin.

Let’s look at what this kind of transformational thinking can mean: Many cities are on large bodies of water and therefore need to think about how sewage treatment plants could transform into nutrient management systems. With struvite harvested in this new way, the capital cost of deploying the system can be repaid in three to five years, and then the city begins making money by selling the phosphate. This approach to nutrient capture also applies to nitrogen.

A city could also supplement that business by making biogas from the methane emanating from the sewage, thereby reducing the release of greenhouse gas while producing energy for sale or to power other operations. The cost to the city of providing a sewer plant has been upcycled into a profit generator.

We have been presenting this idea to locales for years, and we have been delighted by the uptake. Instead of farmers buying slightly radioactive phosphate from Florida, with point-source pollution (a confined and identifiable source, in this case the sewer pipes directly dumping pollutants into a bay), the farmers are receiving a high-quality fertilizer from nearby, and it’s slow-release. Some of the phosphate crystals can take a year to dissolve—eliminating non-point-source pollution (an uncontained source, such as storm-water runoff or fertilizer washout).

All of a sudden the economic vitality of the nutrient polluted Chesapeake Bay, for example, can return with its seafood industry, with its jobs and culture. It can come clean—come back—for good. The city can start making money. Less money spent on transportation, less money spent on environmental cleanup, more money earned by selling struvite and nitrogen and methane.

Toronto is trying a different method of upcycling goods formerly discarded because of the yuck factor. Residents are encouraged to throw disposable diapers full of poop into green recycling bins dedicated to accepting all compostables. The program also takes other materials usually designated undesirable, such as kitty litter, soiled paper, and sanitary products.

At the composting center, the machines sift the materials, then blend and anaerobically digest them while the biogas is captured for energy use. Society can continue to debate the environmental cost of using disposable diapers, but if people are using these diapers already, why not use them constructively, effectively? The diaper can actually help rebuild topsoil. Within seven months, the composting process is complete and the city gives the soil back to park managers and residents for gardens. Michael has shown that, properly deployed, each baby’s diaper use could provide the moisture retention and nutrients for starting more than a hundred trees in a desert.

We are also seeing the use of flies for composting and animal production. The maggots decompose and convert organic vegetable matter or flesh from slaughterhouse scraps into the amino acids and proteins needed by fish and chickens for their diet. In this case, something considered garbage becomes an animal resource, which then can be converted into protein desired by a significant portion of the human population. There might be an attendant yuck factor involved with breeding flies for the food chain, but remember, free-range chickens love insects, and as for fish . . . ask any fly fisherman.

And it is surely less yucky than feeding chickens arsenic to plump them, as many poultry farms currently do.

How to Make Anything a Battery… an Ever-Resourceful Battery

First, let’s look at battery-design optimization in terms of how to hold charges longer. For this earth battery, the emphasis needs to be on how to design agriculture to increase sustainability and growth with optimized interventions. That’s where permaculture, the development of agricultural ecosystems intended to be long term, comes into play.

One of our favorite permaculture experiments, which started in 2002, involved a 10-acre stretch near the Dead Sea in Jordan. This particularly arid stretch of land, with its salted soil baked up to 122° Fahrenheit in August, had frustrated farmers for millennia. In modern times, either they grew their crops under plastic or they drowned the area with pumped-in (and precious) water to push the salt 20 feet down (this ultimately damages the soil for 1,000 years). To encourage what little growth they could get, farmers poured fertilizers and pesticides onto crops. (In Cradle to Cradle, we talked about how cradle-to-grave design often relies on the use of brute force to get the job done. Brute force is not necessarily an effective or efficient or elegant tool to accomplish a task.)

But Geoff Lawton of the Permaculture Research Institute in New South Wales, Australia, thought the farmers might get better results if they worked more holistically with the elements provided to them. They might create a real oasis.

Lawton’s first step was to use the rainwater to its fullest. He and his team dug curving swales—ditches—to collect the small amount of rain that falls in the region in the winter. The ditches managed to catch about 250,000 gallons of water in the winter and slowly leach the moisture back into the soil. Then Lawton created mounds on either side of these ditches and piled waste from a nearby organic farm a foot and a half high for mulch. In the mounds, the team created micro-irrigation tunnels. Then they began planting, first hardy desert trees to perform multiple tasks such as shading the understory crops, slowing evaporation of water, returning nitrogen to the soil, and providing windbreak. Then they planted a row of fruit trees: figs, pomegranates, guavas, mulberries, and citrus. The result: Within four months, they were harvesting figs from only three-foot-high trees. The crops were flourishing. They asked experts from the local university to come test the soil to determine whether they were successfully growing crops in salty soil, or if somehow the salt content had diminished. Indeed, they found that the soil was becoming less salty. Not only that, but rich topsoil had rapidly accumulated.

Eventually, funding for the experimental project expired, and the site was left to local people to perpetuate. One might assume that the desert would take back this terrain. But amazingly, from last reports, the growth continues, because the system was set up to work within its environment, not to fight it with brute force.

This may sound minor, and it is obviously not at the scale to feed millions, but the principles are very important to what we can imagine for our towns and even cities. If an outdoor stretch of the deadest desert can be made fruitful with only rainwater—and no pesticides—then certainly we can imagine and intend for richer territories to produce abundance in similar fashion. As we will see, even barren rooftops.

The Greenhouse Effect (This Time It’s Positive)

So we have a vote optimizing the earth battery for sustained charge, and for the best materials to power that charge. The other factor we can consider is optimized dimensions. Ideally, a battery occupies the smallest dimension while providing the greatest power.

When considering the earth battery, one might be surprised to learn that the Netherlands is essentially one of the most streamlined, minute organic batteries one could imagine. Surprisingly, that smaller country is second only to the United States in terms of agricultural exports (in financial terms) from its production of traditional crops, tomatoes, dairy, and flower bulbs. How in the world did such a small country do this? How could this be done by the second most densely populated country in Western Europe, about the size of Maryland or Bhutan, or slightly larger than Haiti?

The secret is that the Dutch manage nature and its forces very well in open farming. But they also use greenhouses on 0.25 percent of their land, which allows the country to be hyperproductive per square foot, eliminate wind damage to crops, increase solar flux, and reduce water evaporation; furthermore, the soil nutrients exist in closed systems, making their reuse simple. Not only do the greenhouses increase crop yields and decrease energy and water needs, they actually can generate heat for adjacent structures.

If the Netherlands can produce this much value on so little land, what if that country’s methods were applied to other places? Greenhouse growing would allow us to reduce the transportation costs for food by producing crops closer to urban centers where they are needed. And we don’t have to think only about the usual horizontal greenhouse. With a vertical greenhouse where planters are stacked, the rate of production per square foot of land can be as high as six times that of open farming in soil. Crops could be grown on, under, and in buildings to serve local markets.

Human beings naturally upcycle by migrating toward cities to live closer together in compact units. Urban density, by its nature, can deftly enable effective and efficient resource use while encouraging creative and diverse cultures of all kinds. Yet so much of the space in cities is underused. Certainly, we are good at packing as many people as possible into vertical space, but there is a territory in the city almost as large as the city itself that goes unemployed in the project of abundance: the rooftops. Cities and buildings, especially well-planned ones, can be reconceived as gardens. One can imagine a city from the air looking like a large garden divided into a multitude of plots.

Already, cities all over the world are being improved by green roofs. In 2001, Chicago mayor Richard M. Daley hired Bill’s design firm to conceive a green roof on City Hall. This ultimately saved the building $5,000 per year in energy costs. More important, it inspired other green roofs. Chicago’s building code is being altered to promote them. Walmart installed its first green roof in Chicago in 2008, and its commitment to green roofs elsewhere is growing.

A former naval yard building in Brooklyn is now the site for a large urban rooftop farm—100,000 square feet of greenhouse. It is estimated that it will be able to produce one million tons a year of lettuces, tomatoes, and herbs, all hydroponically (in water),2 and will sell the produce year-round to local supermarkets and high-end eateries. Bill’s architecture firm is now designing schools, offices, and factories, which are covered with solar collectors and greenhouses, accruing energy and producing organic food, clean water, and jobs.

Think about what could happen if we began utilizing all available space this way. During World War II, victory gardens, home plots planted with vegetables to help reduce the strain on domestic food supply and on transportation of goods, increased vegetable production in the United States an estimated nine to ten million tons, nearly equaling commercial vegetable production at the time. Those were dispersed gardens, using available green space or creating green space where none previously existed.

What if, in the same way, human beings upcycled places one might not think of to provide earth battery power wherever needed? Think of a simple strategic instruction: Where possible, go from gray to green and hard to soft. From asphalt to vegetation, from concrete to earth.

This is not just about reclaiming underused spaces in established cities. New cities are being built from the ground up in tough terrain for farming in the surrounding land. Bill’s firm has been working with various Chinese cities that have problems with flooding and populations predicted to double. He has proposed bringing the “waste equals food” concept to life: building fertilizer factories, where struvite, magnesium, phosphorus, and nitrogen are cycled, and using this to restore biodiversity to the city’s parks and gardens, while simultaneously cleaning drinking water. The most dramatic change proposes to lift the farming onto roofs, thereby working around the threat of flooding by optimizing water absorption, storage, and usefulness for park and food production. For a new city expanding into previously untouched land, the area might look the same as it used to from the air—green stretches of vegetation—except underneath a city has appeared.

Let’s take this greenhouse thinking even further.

Grown with the Wind

As we said at the start of this chapter, the first green revolution, which could be seen as the dawn of agriculture and green growing, was dramatically expanded by the Borlaug green revolution of the last decades in technique and nutrient management, applied minerals, and genetic modification. The conventional industry thinks that the next green revolution will be an extension of this last one, and we know, of course, that those efforts will certainly continue, since powerful factors in industry and economics are working that way.

But society might also be delightfully surprised. The next green revolution might not come only from that direction. It might well come from intensive local growing and locally optimized systems that benefit from shorter transportation distances, optimized water use, improved permaculture to replace chemical requirements, and multistory greenhouses.

Or even greenhouses that don’t need the sun. Today, farming with LED-lit greenhouses is much more expensive than farming using natural solar light, but we are watching closely as the price drops dramatically due to mass production. If the LED lights are run on renewable power, the system becomes even more interesting. Dutch researchers have found ways to stack farming in warehouses in shelves one and a half meters apart.

China has a real challenge feeding its expanding population. Some regions of China are considered too windy for good farming; 61 percent of the country’s desertification is caused by wind. Some data shows only 15 percent of China’s land is considered arable, and so the pressure now is on the marginal land to produce the food needed.

In China, roofs might be employed, through stacked hydroponics and the rejuvenation of soil through use of the country’s biological phosphate and biogas off-products. But a city can’t feed its whole population by itself, nor can it produce the full varieties of foods people want. The supply must come from the surrounding countryside. If you extend this idea of a concentrated and optimized agriculture system by even miles into the surrounding land, it begs the design question: Why do people go hungry?

If you look at the whole problem, these remote populations need food, but it doesn’t make economic or energy sense to ship produce from far away. What if these regions built greenhouses, some even underground? In that case, the windiness of the regions would be an asset, making the territory more arable. In this case, the light would come not from the sun but from the wind-powered LEDs. The wind would be bringing calories—energy to be used by humans—to people through the food. And what if you took that idea of underground growing even further and were not just getting the crops you needed but were actually storing energy in plants to export to areas that needed energy (in this case caloric). One difficulty with wind power is that it vacillates due to the changes in wind strength throughout the day and night; utility operators struggle with what to do with excess energy during strong gusts, how to store that energy for calmer periods. An ideal system is to create ways to fruitfully dump excess energy and have it ready for another time.

So if we think of the windy areas of China, huge gusts could come through, and unlike most power stations that don’t know what to do with 100 megawatts that show up at one or two in the morning, the system could place all that excess energy into greenhouses and growing facilities, protected from the gale but using the wind to grow plants to make the vegetables. These plants could grow on long racks in meter-high stacks, using only the spectral frequencies of the light that each vegetable needs.

A battery is just something that converts chemical energy into electrical energy. Here electrical energy is converted into chemical energy. Earth as a battery, plants as a capacitor. Instead of metal batteries that are expensive and toxic, how about food as a battery, storing energy for our beneficial present and future use?

Now that’s an idea.

1. The photosynthetic act claims six times the amount of energy in terawatts that humans currently use. Plant life is greedy with its energy needs, greedier than humans are, and yet because of the nature of the energy source for vegetation—the sun—there is no reason to complain. Not only that, the photosynthetic process usefully absorbs energy and stores it, often usefully for our potential need, either as food or as fuel.

2. In traditional soil farming, the key limiting factor is the active transportation of nutrients to the roots. Freshwater aquatic systems are ideal media for vegetation. Salt-water agriculture is also a possibility: Tomatoes are being grown on salinated farmland in Saudi Arabia, for example.