NCAT Program Specialist
Horticulturist Eric Brennan records data on weed seedling growth between rows of a young cover crop at USDA's 17-acre certified organic research plot in Salinas, California.
Photo by: Scott Bauer, courtesy USDA ARS.
Both conventional and organic agriculture depend on fossil fuel and solar energy. The amount of energy used on farms varies depending on the size and geographic location of the farm, as well as the types of products and processes used on the farm. It has been estimated that since 1992, direct energy expenses from fuel and electricity averaged around 7 percent of the average U.S. farm's total operating costs. Incorporating indirect expenses from such things as fertilizers and pesticides increases this average to 15 percent of total operating costs (1).
Energy consumption can vary significantly between conventional and organic production systems when accounting for direct energy inputs as well as indirect energy involved in manufacturing, shipping and applying pesticides and nitrogen-based fertilizers. Because organic agriculture reduces the amount of indirect energy inputs, it is often assumed that organic agriculture is less energy intensive than conventional agriculture. However, this is not always the case.
Practices such as irrigation, heavy machinery use and heated greenhouses consume large amounts of energy. These practices are utilized by both organic and conventional operations. Energy use associated with processing, packaging, storage and distribution must also be taken into account. Several studies have attempted to compare the yield differences, energy inputs and environmental effects associated with conventional and organic cropping systems. What follows is a summary of some of the results of these studies.
Several factors must be considered when comparing the energy intensiveness of conventional and organic systems. One significant challenge is representing a typical conventional or organic system. Farming practices vary widely depending on the location and size of the farm, the type of crop produced and individual farmer decisions. Conventional farming practices range from high-input intensive systems to near-organic systems. Similarly, organic systems, although adhering to a set of standards, differ in implementation. Some organic farms are highly sustainable ecological systems, but some are large-scale monocropping or mass livestock operations that operate like conventional farms, with the exception of not using synthetic pesticides, fertilizers and veterinary drugs (2).
Other factors that affect a reliable comparison of conventional and organic agricultural systems include:
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The widely referenced 27-year Rodale Institute Farming Systems Trial (FST) is the longest-running side-by-side comparison of organic and conventional corn and soybean production systems in the United States. The study compares a conventional farm that uses recommended fertilizer and pesticide applications with an organic animal-based farm where manure is applied and an organic legume-based farm that uses a three-year rotation of hairy vetch/corn and rye/soybeans and wheat. The two organic systems receive no chemical fertilizers or pesticides.
David Pimentel, a Cornell University professor of ecology and agriculture, was the lead author of this study and concluded that "fossil energy inputs in organic corn production were 31 percent lower than conventional corn production, and the energy inputs for organic soybean production were 17 percent lower than conventional soybean production." (3)
A team of researchers, farmers and farm advisors established the Sustainable Agriculture Farming Systems project (SAFS) at the University of California, Davis, in 1988 to study the transition from conventional farming systems to low-input organic systems. The project has compared four systems: organic, low-input, conventional four-year rotations and a conventional two-year rotation. Cash crops in the four-year rotations include processing tomatoes, safflower, dry beans, wheat and corn. The two-year rotation includes tomatoes and wheat.
The team found that the low-input system was most energy efficient and that crop yields were comparable among the different systems. Tomato and corn yields in the organic system were a little lower than in the low-input and conventional systems, mainly from nitrogen limitations. Differences in yields were much greater between years than between systems.
The SAFS team concluded that "the organic system is less efficient than the low-input system because of the great distance that many organic fertilizers (such as dried seaweed) are shipped before arriving at the field, and because of energy requirements for mechanical weed control." (4)
The Glenlea Study began in 1992 with the objective of creating a long-term comparison of the biological, environmental and economic impacts associated with conventional, low-input and organic cropping systems.
Researchers analyzed energy use between 1992 and 2003. The experiment included two four-year crop rotations of either wheat-pea-wheat-flax (WPWF) or wheat-alfalfa-alfalfa- flax (WAAF); and two crop input combinations of either a fertilizer- and herbicide-added (F+H+) conventional system or a no-inputs organic system (F-H-). See Table 1 for more information.
This study found that eliminating fertilizer and pesticide inputs in the organic system resulted in energy-use reductions. Also notable is the potential of perennial forage legume crops, in this case alfalfa, in reducing energy use.
For a full discussion of results, along with cropping system yield information, weed dynamics, soil nutrient status and economic analysis, see the Glenlea Study Web site.
|Table 1. Total rotational energy consumption (MJ/ha)* in the Glenlea long-term cropping systems study, 1992-2003|
|Seed energy||Fuel and
|WPWF = wheat-pea-wheat-flax; WAAF = wheat-alfalfa-alfalfa-flax
In this study, researchers at Washington State University investigated the sustainability of organic, conventional and integrated apple production systems in Washington State from 1994 to 1999. In terms of environmental and economic sustainability, this study rated the organic system first, the integrated system second and the conventional system last.
Researchers measured several indicators of sustainability, including energy efficiency. Energy accounting was divided into inputs such as labor, fuel, fertilizers and so on; output, or yield; and output-to-input ratios, or a measure of energy efficiency. Cumulative energy inputs and outputs for the six-year study period were lower for the organic system than for the conventional and integrated systems. The output-to-input ratio for the organic system during the six-year study period, however, was 7 percent greater than that for the conventional system and 5 percent greater than that for the integrated system, making the organic system the most energy efficient (5).
Learn more about the study at the nature Web site.
The DOK (bio-Dynamic, bio-Organic, and Konventional) long-term field experiment was developed in 1978 in Therwil, Switzerland. The experiment investigated differences in crop yield, soil biology, environmental health and product quality among organic, biodynamic and conventional agriculture methods.
Between 1978 and 1998, this Swiss experiment evaluated energy use for potatoes, winter wheat, beetroots, barley and grass-clover under four different cropping systems:
This study found that the organic farming systems used from 20 to 56 percent less energy to produce a crop unit, measured in metric tons. Per land area this difference was from 36 to 53 percent. See Table 2 for additional information (6).
|Table 2. Energy input per unit land area (GJ ha–1) in the second crop rotation (n = 3)|
|Winter wheat 1||12.52||11.56||18.88||19.74|
|Winter wheat 2||10.31||9.79||20.49||21.81|
|Grass-clover sowing year||6.43||7.63||6.78||6.75|
|Grass-clover 1st year||3.91||4.27||5.22||11.75|
|Grass-clover 2nd year||4.86||6.48||9.98||20.47|
|Mean (energy input per year, sum/7)||12.79||13.27||20.86||24.08|
|Mean% (CONFYM = 100%)||61||64||100||115|
|biodynamic||bioorganic||with manure||without manure|
This study used data recorded between 1990 and 1992 from 14 organic and 17 conventional farms affiliated with the Norwegian Institute of Agriculture Science. All of the farms studied had dairy production combined with grain production, except two of the organic farms that had beef cattle as the main endeavor.
Energy use was analyzed for small grains, grass clover and fodder beets in three soil types. Energy price was determined by the total number of energy inputs in megajoules divided by the total yield output in kilograms.
This study found that "conventional crop yields were higher but they also used more indirect energy with input factors, especially fertilizers. The conventional yields were not sufficiently higher to compensate for the extra use of energy compared with the organic crops." (7)
Learn more about this study at Organic Eprints.
The United Kingdom Department for Environment, Food and Rural Affairs (DEFRA) has conducted a number of studies related to the sustainability of organic agriculture systems. The objective of this March 2000 report was to develop a model of energy inputs in organic farming systems. The model was used to compare energy use in organic and conventional systems of similar capacities. The model incorporated average yield data from previous studies including vegetables, dairy, beef and sheep. This report also took into account energy use associated with transportation.
Among the results found in this study, the following points were established:
For more information on this study, visit the DEFRA Web site.
|Figure 1. Energy input by category on an area basis (MJ/ha)|
|Figure 2. Energy input by category on a unit output basis (MJ/t yield)|
|Figure 3. Direct and indirect energy inputs into livestock enterprises|
This 200-page report was released by DEFRA in December 2006 with the objective of informing government policy about reducing the environmental impacts of food consumed in the United Kingdom. Included in this study was an analysis of the environmental impacts of organic versus conventional food systems in the United Kingdom. The report states producing many foods organically affects the environment less than producing the foods conventionally. However, that is not true for all foods and is rarely true for all classes of environmental effects. The report said that not enough evidence is available to state that organic agriculture will have fewer harmful effects on the environment than conventional systems.
More specifically, the DEFRA report proposed the following:
The DEFRA report concludes that more research needs to be done in order to more accurately determine the environmental impacts of organic and conventional foods (9).
This article received much press with titles such as "Why going organic could cost the earth," "UK research casts doubt on environmental claims" and "How green is organic?"
In response, the Soil Association released a statement to assure consumers of the benefits of organic food.
The Soil Association argued that organic farming is about 30 percent more energy efficient for producing the same quantity of food as conventional agriculture. In their argument, the association included the following list of food products and how much energy an organic system required to produce the food in comparison to a conventional system. See Table 3 for more information.
The Soil Association also promoted the other environmental benefits of organic agriculture, including improved soil quality, supporting local food markets, increased biodiversity and reduced pesticide pollution, water usage and packaging waste. For more information, view the press release at the Soil Association's Web site.
|Table 3. Energy used to produce food products in organic agriculture systems compared to conventional systems|
|Leeks 58% less||Onions 16% less|
|Milk 38% less||Pig meat 13% less|
|Beef 35% less||Potatoes 2% more|
|Wheat 29% less||Eggs 14% more|
|Carrots 25% less||Tomatoes (long season)
|Lamb 20% less||Chicken 32% more|
In this study, 15 suckler-beef units in southern Ireland were assessed in terms of greenhouse gas emissions. The units included five conventional, five organic and five Rural Environmental Protection Scheme (REPS) systems. REPS was implemented in Ireland as a system for rewarding farmers that adhere to strict guidelines regarding nutrient management and habitat conservation.
Emissions factors considered included diesel fuel used, fertilizer applied, manure management and electricity, among others. Results of this study indicated that applying REPS systems would result in less greenhouse gas emissions in comparison to conventional suckler-beef production. Emissions could be reduced even more by applying organic systems, but would result in a substantial drop in production (10). The technical report is available online.
This report, released in August of 2007 by the Food and Agriculture Organization of the United Nations, used existing research to examine the potential of organic and nonorganic agricultural systems to reduce energy consumption and mitigate climate change. The study revealed the following points:
The report indicated that further research is needed to determine whether reductions in energy consumption on the production side of organic systems are maintained through post-production processing, packaging and transport.
According to the Food and Agriculture Organization, "Organic agriculture holds a great potential for pioneering energy-reducing practices through the framework of organic standards. Organic principles, which emphasize environmental stewardship, farm-level self-sufficiency and incorporation of externalities, can be leveraged to develop strategies for limiting use of fossil fuel-based energy in organic agriculture. Especially in the areas of post-production handling, innovations in the organic supply chain to decrease energy consumption can influence parallel conventional sectors." (2)
Visit the Food and Agriculture Organization's Web site for additional information on this research.
As is apparent in a review of existing studies, there are many complexities involved in comparing energy consumption in conventional and organic cropping systems. Some research indicates that organic agriculture is more energy efficient than conventional agriculture, but not in all cases. In some cases, organic agriculture may be more energy intensive depending on the specific farming operation, the crop produced and the post-production handling. It is important to assess the energy intensiveness of food systems in a holistic manner that incorporates energy consumption for the entire life cycle of the food product.
1) Shoemaker, Robin, et al. 2006. Agriculture and Rural Communities Are Resilient to High Energy Costs. Amber Waves. April 2006.
2) Ziesemer, Jodi. August 2007. Energy Use in Organic Food Systems. Natural Resources Management and Environment Department, Food and Agriculture Organization of the United Nations. [PDF/151KB]
3) Pimentel, David. August 2006. Impacts of Organic Farming on the Efficiency of Energy Use in Agriculture. An Organic Center State of Science Review. [PDF/3.03MB]
4) The Transition from Conventional to Low-Input or Organic Farming Systems: Soil Biology, Soil Chemistry, Soil Physics, Energy Utilization, Economics, and Risk. November 2000. University of California Sustainable Agriculture Research and Education Program.
5) Reganold, John, et al. April 2001. Sustainability of three apple production systems. Nature. Washington State University.
6) Mader, Paul, et al. May 2002. Soil Fertility and Biodiversity in Organic Farming. Science. Switzerland Research Institute of Organic Farming.
7) Refsgaard, Karen, et al. November 1997. Energy Utilization in Crop and Dairy Production in Organic and Conventional Livestock Production Systems. Agricultural Systems. Agricultural University of Norway. [PDF/2.25MB]
8) Department for Environment, Food and Rural Affairs. March 2000. Energy Use in Organic Farming Systems.
9) Department for Environment, Food and Rural Affairs. December 2006. Environmental Impacts of Food Production and Consumption. [PDF/1.88MB]
10) Casey, J.W. et al. April 2005. Greenhouse Gas Emissions from Conventional, Agri-Environmental Scheme, and Organic Irish Suckler-Beef Units. University College Dublin.
Granatstein, David. Does Organic Farming Use Less Energy? Compared to what? Washington State University. Presentation at the ACEEE Conference, Food and Energy from the Ground Up: Efficiency's Role in Sustainable Agriculture, Des Moines, Iowa, February 20–22, 2008.
Comparing Energy Use in Conventional and
Organic Cropping Systems
By Holly Hill
NCAT Program Specialist
Holly Michels, Editor
Sherry Vogel, HTML Production
This page was last updated on: August 28, 2014