- About 10 percent of U.S. energy consumption is for raising, distributing, processing, preparing and preserving the plant and animal matter Americans eat.
- Energy use can be cut by converting agricultural waste such as manure into power; implementing new, pilot-level farming techniques such as drip irrigation, no-till planting, laser-leveling of fields and GPS-driven machinery; reducing spoiled and wasted food, which amounts to 25 to 30 percent of all food produced; and eating less meat, which is energy-intensive to create.
- The same steps would make our bodies, and our ecosystems, healthier.
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.