The following article, originally published in Scientific American, is republished here with the permission of the author, Dr. Michael E. Webber. The food-energy nexus is at the heart of Sustainable America’s mission. Dr. Webber addresses the precarious relationship between U.S. food and energy supplies, and explains how policy, innovation and personal action can serve as potential solutions. His argument is convincing, and ultimately uplifting.
For more than 50 years fossil fuels and fertilizers have been the key ingredients in much greater global food production and distribution. The food-energy relationship has been a good one, but it is now entering a new era. Food production is rising sharply, requiring more carbon-based fuels and nitrogen-based fertilizers, both of which exacerbate global warming, river and ocean pollution, and a host of other ills. At the same time, many nations are grappling with how to reduce energy demand, especially demand for fossil fuels.
Although transportation, power plants and buildings receive a lot of policy attention as targets for reducing energy consumption, our food supply is often overlooked. In the U.S., about 10 percent of the energy budget goes to producing, distributing, processing, preparing and preserving the plant and animal matter we consume. That is a considerable wedge of the energy pie.
Examining our food supply through the lens of energy use reveals opportunities for smart policies, innovative technologies and new dietary choices that can potentially solve food and energy problems together. The same steps would also make our bodies, and our ecosystems, healthier.
Farm to Fork Is Highly Inefficient
Simple math shows that food production is an inefficient process. Plant growth is not energy-efficient: photosynthesis typically converts less than 2 percent of incoming solar energy into stored energy. That low rate is worsened when animals convert plant matter into beef (5 to 10 percent efficiency) or chicken (10 to 15 percent). We then ingest that food and convert it into human energy stored as glycogen in muscles and as fats—notably around our midsection.
Given the abundance of photons striking the earth every day, low efficiencies hardly seem to matter. But when faced with limits on land, freshwater, fertilizer runoff, and fossil-fuel affordability and emissions, the inefficiencies can be daunting. The energy used to make food is vastly greater than the amount of energy we get out of it. The U.S. expends roughly 10 units of fossil energy to produce one unit of food energy.
The magnitude of consumption is remarkable when one considers the entire population. A healthy, active adult male’s nominal instantaneous power consumption is approximately 125 watts. That equates to roughly 2,500 nutritional calories per day, or about 10,000 British thermal units (Btu). Thus, the 312 million people in the U.S. need about one quadrillion Btu (one quad) of food energy every year. Because we use 10 units of fossil energy to produce one unit of food energy, feeding the population requires 10 quads—which is 10 percent of the total annual U.S. energy consumption of 100 quads. If we as a society wish to reduce our food-energy consumption, we need to find ways to reduce the 10:1 ratio of energy input to food output.
The food energy needed to feed the world’s seven billion people is about 25 quads a year, which is only about 5 percent of the world’s 500 quads of annual consumption. It is not that the rest of the world is more efficient than the U.S. Rather one billion people are hungry, another billion are at risk of hunger and many more simply do not consume much.
Extensive energy use has dramatically increased food production through innovations such as diesel-powered tractors, electric irrigation pumps, and fertilizers and pesticides made from natural gas and petroleum. Since the mid-20th century crop yields from this green revolution have gone through the roof, and we have transformed deserts such as the Central Valley of California into the world’s fruit baskets. At the same time, the percentage of workers needed for agriculture has plummeted.
Cheap energy, primarily petroleum, has also created transportation networks that have improved food distribution significantly, bringing us unexpected fare such as salads and fresh oranges in the middle of winter from far-flung corners of the globe. We expend more energy still to preserve and prepare our food.
When fossil-fuel prices were low and we did not care much about pollution or emissions, we did not worry about the energy waste. Now that prices are higher and we care more about environmental impacts, we have to improve that 10:1 ratio. The inefficiency could get even worse in the U.S. as more people, powered by cheap air conditioning, move into areas where local food production can support a mere fraction of the growing population (think Phoenix). In these cases, even more energy is used either to bring inferior lands into production through energy-intensive fertilizers and irrigation or to move food from remote markets.
Global trends will aggravate the challenge. World population is projected to grow to more than nine billion by 2050. Per capita energy and food consumption will rise, too: notably, as people get richer, they consume more meat, which is much more energy-intensive than other foods. And climate change implies that food production will be hurt by crop losses from droughts and floods, saltwater intrusion into aquifers, higher temperatures (which will decrease the effectiveness of photosynthesis in many places) and competition from biofuels for farmland. As a consequence, experts predict that food production will have to double by 2050.
Local Farming Might Not Help
Unfortunately, thinking about some popular food production “solutions” through the lens of energy shows that they do not always help. For example, many people have latched onto the local-food movement, billing themselves “locavores,” as an antidote to the energy used to transport food long distances and the energy intensity of large-scale industrialized agriculture. “Eat local” campaigns encourage residents to shop for local food from farmer’s markets or nearby community-supported farms.
Spending our money in the local community rather than sending it far away can be economically valuable, and having a vibrant local-food system creates resiliency in the event of unexpected occurrences such as war or drought. Local farms, however, sometimes use marginal lands to produce nonnative crops that require more chemicals and more energy for irrigation, and they still get low yields. Strangely enough, shipping food thousands of miles can sometimes require less energy, emit less carbon dioxide and do less environmental damage.
For example, it is typically less energy-intensive to grow lamb in New Zealand, where the animals graze on rain-fed grass that grows mostly without fertilizer or irrigation, and ship it to the U.K. than it is to grow lamb in the U.K. using energy-intensive inputs. Further, large industrialized farms, outfitted with laser-leveled fields (to minimize water losses and fertilizer runoff) and GPS-equipped tractors (to optimize fuel use and crop density) and planted with genetically modified crops designed to use minimal water can be surprisingly resource-efficient when compared with a bunch of distributed farms that inefficiently use energy and water but are closer to home. A Stanford University study concluded that Big Agriculture has spared a lot of carbon emissions because of its yield improvements and economies of scale.
Vertical, urban farms or algae production for feed, now in prototype stages, also has the potential for even greater biomass production per square foot of land than local farms.
Some popular solutions for renewable energy actually complicate the food-energy system. Food-based feedstocks—corn, soy, sugar and palm—dominate the world markets for biofuels and create unhealthy competition for farmland and freshwater. In 2010 in the U.S., about 30 million acres—more than one fourth of overall corn production—were used to produce 12.7 billion gallons of ethanol. That share will rise significantly as the U.S. tries to meet the federal mandate that 20 percent of all liquid transportation fuel come from biofuels by 2022.
Exploit the Waste
Despite all the concerns of the food-energy nexus, there is some cause for optimism. With different innovations, policies, markets and cultural choices that focus on reducing waste and inefficiencies, we can reduce the 10:1 ratio of energy used to energy eaten, as well as mitigate environmental damage.
A first step is to stop using corn kernels for starch-based ethanol, which is the current U.S. practice. Let us use the kernels to feed people and livestock and use only the cellulosic stover (the stalk and leaves of the plant) to make ethanol or synthetic fuels. U.S. energy policy already includes a push for this solution. The Energy Independence and Security Act of 2007 has a renewable fuels standard that mandates that we consume 36 billion gallons of biofuels per year by 2022 and that 16 billion of those gallons come from cellulosic sources. The latter requirement is a rare acknowledgment by politicians in Washington, D.C., that corn might not solve all our energy problems; experts predict we can produce only up to 15 billion gallons a year from corn-based feedstocks grown on available farmland without undercutting our ability to feed ourselves.
The aggressive biofuels rollout, however, pushes the food-based forms online the quickest, with cellulosic forms many years behind because they are more difficult to produce. Nature has designed cellulosic materials over many millennia to not break down. Breaking them down for ethanol means we have to reverse nature, which requires enzymes—code for money; producing enzymes at industrial scales is expensive. Nevertheless, we can overcome the technical hurdles and move more strongly in that direction. Using cellulosic sources instead of food-based sources can help the U.S. energy supply and also free up tens of millions of acres for other food production.
Another step to improve the food-energy equation is to convert agricultural waste products into power. Livestock manure is one rich resource. In the old days, small farms had a mix of animals and a variety of crops in one location; farmers spread manure instead of chemical fertilizer on fields of crops. Today, with large farms that grow just a handful of mega crops and with concentrated animal-feeding operations, that closed-loop practice has been lost. The massive amounts of manure created by large animal operations far exceed any local demand, and it is too expensive to ship cross-country to big farms. The system also creates environmental hotspots such as manure lagoons, which are significant emitters of greenhouse gases and sources of toxic waste. The lagoons are remarkably energy dense, however, and there are many of them; U.S. farms generate more than one billion tons of manure annually.
Anaerobic digesters and micro turbines could convert that manure into enough renewable, low-carbon biogas-fired electricity to displace 2.5 percent of the nation’s power generation while reducing greenhouse gas emissions. This approach would also yield another revenue stream for farmers. Researchers at leading agricultural institutions such as Texas A&M University and Cornell University College of Agricultural and Life Sciences are looking at new ways to incorporate anaerobic digestion of manure into farm operations. Juehnde, a small German village working with Frank Mitloehner of the University of California, Davis, is generating so much biogas for heating and cooking that the town has become independent from the national gas grid. Policy makers could encourage the installation of more digesters and turbines by giving farmers access to low-cost capital, creating incentives such as property-tax breaks for the equipment, offering information and training sessions so that potential users know how to operate the systems, and establishing net metering—a system allowing any electricity generated on-site to reduce farmers’ utility bills.
Another waste stream that can save food energy is carbon dioxide from smokestacks at coal plants. It can be used to grow algae for human food, animal feed and fuel, thereby avoiding some traditional energy inputs for agricultural production. Some people already eat algae directly for nutritional reasons, and some national restaurant chains use them as a stiffening ingredient. Algal lipids can also be converted into biodiesel, providing a low-carbon, domestic, renewable fuel that is made from something other than food-based feedstock. The remainder of the algal biomass is typically made up of proteins and carbohydrates, which might displace corn-based feed for animals, making more corn available for food and thereby contributing positively to the food-energy nexus. Some algae grow well in brackish water or saltwater, too, eliminating demand for freshwater. Private industry (through a variety of start-ups such as Solazyme), national labs such as the National Renewable Energy Laboratory, and universities such as the University of Texas at Austin and the University of California, San Diego, all have active testing and pilot programs. Although algal solutions seem to be decades away from large-scale implementation, their promise warrants additional research, so policy makers should continue funding development.
More Crop per Drop
Simply implementing innovative agricultural techniques that have already been perfected in pilot programs on a much wider scale could significantly reduce the 10:1 energy-food ratio. For example, drip irrigation provides more crop per drop, sparing freshwater and the energy needed to pump it. The conventional approach—the center-pivot sprinklers that create alienlike green crop circles in the middle of brown deserts (easily visible when flying overhead)—is extremely wasteful, spraying water into the air where a major fraction evaporates. Droplets that do land on crops are likely to hit the leaves and stalks instead of the roots, causing more evaporation loss. In a typical drip-irrigation setup, long sections of narrow tubing laid at the bottom of plants sown in a row deliver water directly to the roots. Researchers at Iowa State University estimate that corn farmers in that state would use 40 percent less water and lower their energy bills by 15 percent with drip irrigation. Half a dozen large farm suppliers now offer the systems, which, if used widely, could save thousands of megawatt-hours of electricity nationwide every year. Incentives to switch to drip irrigation, combined with penalties for wasted water, might hasten adoption.
No-till agriculture is another promising approach. It reduces the disturbance of soils by using special planting equipment that places seeds into untilled soil through narrow surface slots rather than the blunt approach of turning the soil. Disturbing the soil less reduces labor, irrigation, energy, erosion and carbon emissions. Argentina is the world leader; more than half the farms there deploy this advanced technique. Training for farmers about the advantages of no-till can be implemented through agricultural extension services nationwide.
Laser-leveled fields can minimize erosion, irrigation and fertilizer runoff. Most fields have a gradual slope, which causes unequal water distribution and uneven collection of runoff. Rather than risking one portion getting less water than it needs, farmers often overfill the entire field, with the excess spilling over into local waterways. By making fields level, farmers waste less energy pumping water, and less fertilizer is needed because less runs off.
The advent of GPS-enabled tractors, combines and other machinery—today a standard feature offered by manufacturers such as John Deere—has introduced the concept of “precision farming,” which drives up productivity and drives down energy use. GPS guidance allows farmers to tend fields and plant crops literally to the inch, reducing wasted space, time and fuel, without even needing to steer machines with their hands. Although the upgrades for a moderately sized farm might cost $10,000, researchers at Purdue University have shown that the benefits outweigh the cost. For one thing, fuel use decreases. Incorporating GPS with field diagnostics allows farmers to map out soil conditions and fine-tune the application of chemicals, which can vary from one end of a field to the other, ultimately requiring less. Fields can also be worked at night and during fog and rain, when human visibility is limited, pushing productivity up.
Reducing wasted food can also lower the 10:1 ratio of energy used to food eaten. An egregious 25 percent or more of the food grown is wasted annually. That massive amount represents 2.5 percent of annual U.S. energy consumption—more energy than all the ethanol produced in 2011 in the U.S. and more than the energy that will be produced in 2030 from lifting drilling restrictions today on the outer continental shelf. Simply decreasing the amount of food we throw away might reduce energy consumption and greenhouse gas emissions more over the next decade or two than many of the expensive or controversial energy supply policies that have been proposed.
Many methods of reducing food waste can begin tomorrow. We can invest in diagnostics that monitor food spoilage instead of using the crude date-based labeling system that has been in place for several decades. One example is temperature- and time-sensitive inks on food packaging that cause labels to change color if the food has been exposed to the wrong temperature for too long. Start-up companies produce these labels, which could spare a lot of food that is unnecessarily thrown away by stores that are worried about making their customers sick. The labels could indeed also prevent a lot of illnesses induced by spoiled food. Requiring companies to keep track of the temperatures that food has been exposed to—in addition to how long the food has been packaged—might give retailers and consumers better information about the risks of spoilage.
Different attitudes and dietary choices can help, too. Restaurants can stop serving mammoth portions, and consumers can stop bragging about their conquests at all-you-can-eat buffets. More extra food can be kept and eaten as leftovers. We can shift our diets to replace at least some of our energy-intensive meats with less energy-intensive fruits, nuts, vegetables, beans and grains. These behaviors do not require invention; they just require new thinking. Many of them end up saving consumers money as well. Having meatless Fridays or veggie Mondays might start to get us there.
As the original green revolution showed, large-scale changes can be implemented relatively quickly over just a few decades. The changes can be dramatic, achieving outcomes far better than anticipated. Yet surprises can arise, too: years of abundant food production have increased the incidence of obesity and aggravated climate change. Technology alone is not enough; even with the original green revolution, hunger has not been solved. A global approach to reducing the energy waste in food that incorporates new behaviors, attitudes and policies will be critical to widespread success. There is no reason to think this new green revolution will be any different.