Science to Live By: Energy Part Three: Food Choices


© J. Dirk Nies, Ph.D.

Fall is in the air. Days are shortening and the nights oftentimes are cold. Nature is responding to this diminishing inflow of solar energy in myriad ways. Trees are tossing their leaves to the ground. Squirrels are rebuilding their leaf-lined nests and hoarding nuts. Migratory birds and Monarch butterflies are flying south to warmer climes. White-tailed deer, sheep and goats are rutting. Bears and bats are hunkering down and preparing to hibernate for the winter. Bees are clustering (when temperatures drop below 55 degrees), forming a dense ball around the queen and conserving precious energy within the hive. And as November draws to a close, many of us will gather with family and friends to share a feast around the Thanksgiving table.

Especially during this season of the year when fields are fallow, orchards bare, and the weather sometimes chilly and damp, we more deeply appreciate nourishing food and warm, dry shelter: the most fundamental necessities of life. To provide these necessities, we must expend energy.

Picking up where we left off last month, let’s look at our energy expenditures in the food and household sectors of our economy and where and how we expend energy through the choices we make (perhaps unwittingly). Three governmental reviews and surveys are helpful in this regard: Energy Use in the U.S. Food System published in 2010 by the Economic Research Service of the U.S. Department of Agriculture (USDA); and the Residential Energy Consumption Survey along with the Annual Energy Review both published and updated in 2012 by the Energy Information Administration of the Department of Energy (DOE). These resources are available free of charge and may be accessed via the internet.

There are upwards of 45,000 distinct items for sale in a typical US supermarket. Each one of these has its own history of energy expenditures. To illustrate the scope of this energy history, consider the following representative scenario for fresh-cut salad greens.

A farmer sowed seeds of lettuce and other salad greens using a planter attachment on a tractor powered by fossil fuels. Between planting and harvest, a broadcast spreader applied fertilizer, and possibly pesticides and herbicides. These farm products were manufactured using natural gas and electricity and transported to wholesalers, retailers and farms. During times of inadequate rainfall, electric-powered water pumps irrigated the fields. At harvest, field workers packed these greens in boxes and loaded them on trucks for shipment to a regional processing plant. There, electric powered machinery cleaned, cut, mixed, and packaged the salad greens. Paper mills and plastic packaging manufacturers used energy to produce the shipping boxes and plastic packaging. The packaged mix was shipped in refrigerated containers by rail and truck to the local grocery store, where it is placed under lighted displays and kept under refrigeration.

An advertisement touting a sale on fresh-cut greens caught our eye and we traveled by car to pick up a package or two with our other groceries. Once at home, we refrigerated these greens for a few days. After dinner, the dishes and utensils used to prepare and eat the salad were cleaned in a dishwasher. The leftovers were ground in a garbage disposal. The plastic packing was thrown out in the trash to be hauled to a landfill.

As stated above, energy is used in each stage of the US food supply chain. These stages can be defines as: farm production and agribusiness (agriculture); food processing and brand marketing (processing); food and ingredient packaging (packaging); freight services (transportation); wholesale and retail trade and marketing services (wholesale/retail); away-from-home food and marketing services (food and beverage service); and (7) household food services (household). According to USDA and DOE reports, we utilize the largest fraction of food-related energy in our homes (27.8%), followed by processing (18.8%), wholesale/retail (15.6%), agriculture (14.7%), food and beverage service (12.8%), packaging (6.4%), and finally transportation (3.9%).

This is astonishing! Farms account for less than 15 percent of all energy used in the food system, and commercial transportation of food accounts for less than 4 percent. I thought that energy-intensive agriculture and long-distance food transportation were supposed to be the two main culprits. Also remarkable is that both the food processing and wholesale/retail food establishment sectors of the supply chain each expend more food-related energy than farmers do.

Perhaps most sobering, retail consumers expend the most of any sector, and nearly twice as much as farms. Where does all our household food-related energy go? Domestic energy expenditures for food-related operations include: electricity for storing, preparing and cooking food, and cleaning dishes and kitchen equipment; natural gas and liquid petroleum gas for cooking food; auto fuel for food-related personal transportation; embodied energy in purchases of food storage, preparation, and serving equipment (the energy used to manufacture and transport refrigerators, ovens, microwaves, dishwashers, pots, dishes, cutlery etc.); and part of the embodied energy in purchases of automobiles, auto parts, and auto services.

Where are we heading? Energy expended on food-related activities comprised 12.2 percent of total US energy expenditures in 1997. By 2007, these expenditures had risen to 15.7 percent. This translates into about a 25 percent increase per person in just ten years! Major contributors to this trend of increased energy use were our swelling appetite for prepared, processed and frozen foods along with their attendant packaging and requirements for refrigeration. Not surprisingly, our trash also reflects our changing food choices. EPA estimates that per capita generation of municipal solid food waste increased 14.5 percent between 1990 and 2000 and an additional 10.1 percent between 2000 and 2007; or about a 25 percent increase per person in 17 years.

How can we, if we so desire, be more energy efficient regarding the foods we eat? The answers are many and they reflect our different and varying circumstances. Eating more homegrown, locally grown, unpackaged and unprocessed foods, such as fresh fruits and vegetables, is an effective way to reduce our food-related energy footprint. Energy savings also can be achieved by fermenting raw foods. Reviving the old traditions of preserving can also add zest to any meal. Brewed carbonated fruit drinks like ciders, root beers and water kefirs are delicious. Cultured dairy products that transform milk into yogurt, sour cream and aged cheeses are other examples. Fermented vegetables, such as sauerkraut, pickles and kimchi, add a sharp complement to any lunch or dinner.