This article gets to the heart of the issues. I differ on the subject of efficiencies and local food production. Local does not mean soils are compromised if growing in soil-less recirculating beds. Judging from the root mass and vertical growing biomass it takes the terms square foot gardening to something more like square inch growing. With urban greenhouses, commercial production crops can be produced at a low cost and with added revenue from food processing (salad bar, juice bar, canning, etc), education (teaching community about farming and food nutrition and preparation and energy (net positive with appropriately sized anaerobic digester). Water will definitely have to be streteched which makes recirculating soil-less methods critically important. I would also ad that algae for feed is better than algae for fuel but not as good as duckweed for both.
“Changes in agriculture, policy and personal behaviors can reduce the energy a nation uses to feed itself and the greenhouse gases it emits.
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.
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.”