Implications of Fossil Fuel Dependence for the Food System

June 11, 2006

NOTE: Images in this archived article have been removed.

Abstract: Our current industrialized food system is not sustainable due to it’s over dependence on non-renewable fossil fuel energy and it’s degradation of the natural systems on which it depends for its existence. If action to change these aspects of the food system are not taken, convening resource depletion and degradation will cause the food system to collapse. Our food system is the result of the “green revolution” which created greatly increased crop yields by using large amounts of fossil fuel energy in the form of synthetic nitrogen fertilizers, petroleum based agrochemicals, diesel powered machinery, refrigeration, irrigation and an oil dependent distribution system. This system destroys biodiversity, contributes to global climate change and degrades soil and water quality.

The availability of decades of cheap fossil fuel energy has allowed the food system to become dependent on finite resources that are rapidly being depleted. Due to the constraints of the first and second laws of thermodynamics this system can not be maintained in its current form. Essential components of the current system such as synthetic nitrogen fertilizers which require natural gas as a feedstock and oil dependent distribution exemplify the fragile nature of the food system. A wide scale conversion to low energy, ecologically sustainable agriculture must be implemented to avoid food system collapse and future food supply shortages.


The current food system is dependent on non-renewable fossil fuel resources which will soon become increasingly scarce and expensive. This dependence is a threat to food security and future food supply.

For most of the last 10,000 years, agriculture has had balanced energy and nutrient cycles, which appropriated the solar energy harnessed by photosynthesis (Chancellor and Goss 1976, Smil 1991). Taking advantage of cultural practices such as crop rotations, green manures and draft animals allowed for humanity to live within the regenerative capacity of the biosphere (Bender 2001, Wackernagel et al 2002) . To better understand the energy balance of the food system it is helpful to look at it in the light of the laws of thermodynamics. Energy can not be created and it is degraded when it is converted from one form to another (Chancellor and Goss 1976, Hendrickson 1996, Timmer 1975). The food system can now be viewed as a system that converts non-renewable fossil fuel energy into food (Pimentel and Giampletro 1994). Currently about 10 to 15 calories of fossil fuel energy are used to create 1 calorie of food and although it only uses about 17% of the U.S. annual energy budget it is the single largest consumer of petroleum products when compared to any other industry. This means that it requires about 1,500 liters of oil equivalents to feed each American per year (Hendrickson 1996). As long as the energy resources are cheap and abundant the inefficiencies are unimportant, however dependence on finite resources is quite a vulnerability when those resources become scarce (Gever et al 1991).

The U.S. food system has had three main periods of change which have brought it to it’s current condition of fossil fuel dependence (Gever et al 1991). The first was the expansionist period occurring between around 1900 and 1920. In this period, increases in food production were a factor of putting more land into production, with no real breakthroughs in technology. The second was the intensification period, also called the “green revolution” which occurred between around 1920 and 1970. In this period technological advances allowed for the exploitation of cheap abundant fossil fuel energy resulting in a seven fold increase in productivity (output per worker hour). Farm machinery, pesticides, herbicides, irrigation, new hybrid crops and synthetic fertilizers allowed for the doubling and tripling of crop production and the corresponding growth of the human population (Gever et al 1991, Ruttan 1999). We are currently in the saturation period of agriculture characterized by greater amounts of energy required to produce smaller increases in crop yield, i.e. the ratio of crop output to energy input is diminishing. An ever growing amount of energy is expended just to maintain the productivity of the current system; for example about 10% of the energy in agriculture is used just to offset the negative effects of soil erosion and increasing amounts of pesticides must be sprayed each year as pests develop resistance to them (Gever et al 1991, Pimentel and Giampletro 1994).

Although beyond the scope of this paper, it is important to acknowledge that aside from being dependent on non-renewable resources, agriculture is also rapidly diminishing the ability of vital “renewable” resources to regenerate (Pimentel and Giampletro 1994, Wackernagel et al 2002). Of these resources water and topsoil (humus) are most limiting . Water scarcity associated with agriculture is typically a regional issue. In the western U.S. the Colorado River has had so much water diverted from it that it no longer reaches the ocean and the great Ogallala aquifer is being overdrawn at 130 to 160% its recharge rate (Pimentel and Giampletro 1994). Other problems are the vast amount of pollution associated with agricultural runoff, which degrade aquatic ecosystems and create dead zones in the ocean (Matthews and Hammond 1999). Approximately 90% of U.S. agricultural lands are losing topsoil above sustainable rates (1t/ha/yr) due to erosion and the application of synthetic fertilizers actively promotes soil degradation (Gever et al. 1991, Pimentel and Giampletro 1994). Other considerations are the loss of biodiversity due to clearing land for large monocrops as well as agricultures contribution to global climate change by way of its CO2 and methane by products (Pirog et al 2001, Wackernagel et al 2002).


Fossil Fuel Dependence

The food system is currently dependent on fossil fuels for powering irrigation pumps, petroleum based pesticides and herbicides, mechanization for both crop production and food processing, fertilizer production, maintenance of animal operations, crop storage and drying and for the transportation of farm inputs and outputs. Of these fossil fuel dependences, some are more easily overcome than others (Ruttan 1999). However, due to their current necessity, dependence on synthetic nitrogen fertilizer and the long distance transport of farm inputs and outputs are two outlying limiting factors that exemplify the vulnerability of the current food system and therefore require further analysis (Smil 1991, Pirog et al 2001).

In terms of its necessity for the existence of a large portion of the global population, the most important invention of the 20th century is the Haber-Bosch process for the synthesis of nitrogen fertilizer. Nitrogen accounts for 80% of volume of atmospheric gas but it is in a non-reactive form that is not readily available to plants, making it the main limiting factor for global crop production and human growth. It is a vital component of chlorophyll, amino acids, nucleic acids, proteins and enzymes. Synthetic N is responsible for raising crop yields approximately 35 to 50% over the last half century accounting for 80% of the increase in cereal crops, without which much of the worlds population would not exist (Smil 1991).

For most of human existence N fixation (the splitting of N2 to form Ammonia) was limited to bacteria (primarily Rhizobium). With the invention of the Haber-Bosch process in 1913 humans began domination of the N cycle (Smil 1991). This process is extremely energy intensive requiring the reaction of 1 mole of nitrogen gas with 3 moles of hydrogen gas under temperatures of approximately 400°C and pressures of approximately 200 atmospheres (Marx 1974). This accounts for 30% of the energy expenditures in agriculture. The hydrogen gas for this process comes almost exclusively from natural gas which is considered as a feedstock and not factored in as part of the energy expenditure (Hendrickson 1996). It is also possible to get the required hydrogen by the electrolysis of water but this requires more energy, making it an unfavorable alternative at this time (Gilland 1983). Natural gas currently accounts for 90% of the monetary cost of N fertilizer (Wenzel 2004).

Other obstacles associated with N fertilizer are production capacity, transport, storage, application and N saturation. Crops only absorb about half of the nitrogen they are exposed to, much of the rest runs off the fields with water flow, saturating the environment and polluting aquatic ecosystems (Matthews and Hammond 1999, Smil 1991). Between 1950 and 1989 fertilizer use increased by a factor of 10 and it has since had continued growth. In developed nations much of that use produces animal feed which is converted into more animal product consumption. However, in lesser developed parts of the world such as Asia which currently accounts for 50% of fertilizer use, crop yield for direct human consumption has been increased (Matthews and Hammond 1999). In many developing countries access to fertilizer and proper application are still often a limit to crop production (Hardy and Havelka 1975).

Although synthetic nitrogen fertilizer and its dependence on natural gas is a major limiting factor of the industrialized food system, perhaps the greatest vulnerability is the dependence on the transportation system for farm inputs and outputs; for example fertilizer is of little value if it can not be effectively delivered to where it is needed (Hardy and Havelka 1975, Pirog et al 2001). The transportation of farm inputs and outputs consumes a large amount of fuel. Data from 1977 shows that 2,892 million gallons of diesel fuel and 411 million gallons of gasoline were consumed for this purpose in the U.S. Of this amount 195 million gallons were used for the shipment of fertilizer. In the U.S. long distance food transportation is often a luxury, providing us with “fresh” produce and seafood from exotic places at any time of year (Gever et al 1991).

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Figure 1. (Pirog et al 2001).

The mean distance U.S. food travels is now estimated at 1,546 miles but this distance varies greatly depending on the food item (Figure 1) (Pirog et al 2001).

Although the transport of food uses a relatively small amount of the U.S. energy budget, it is important to realize that it is a vulnerability for food security, i.e. many communities do not have the infrastructure to produce even non-luxury food items.

Currently 6 to 12% of the food dollar is spent to account for transportation costs, however U.S. tax dollars heavily subsidize highway maintenance and the oil industry so the true cost is much greater ( Hendrickson 1996). Considering the importance of long distance transportation to our food supply, the cost of food is very dependent on the cost of oil (Gever et al 1991).

Fossil Fuel Depletion

The fossil fuels which are most important to the food system are oil and natural gas. Both of these are finite resources and therefore began being depleted the moment humans started using them. When graphed over time, production (synonymous with extraction) of these resources follows a bell shaped curve (Figure 2). The high quality easily produced (cheap) resource is produced first (on the up slope), followed by a peak or plateau in production, then the progressively harder to extract lower quality (expensive) resource is produced on the down slope of the curve (Bently 2002, Campbell 2004, Gever et al 1991). When peak production occurs we know that roughly half of the resource remains, however much of it will never be produced because it becomes to energy intensive (expensive) to do so, i.e. it takes increasingly more energy to produce increasingly less energy and when that ratio (energy profit ratio) reaches 1, it is no longer an energy source, it is an energy sink. This model for resource depletion is what is known as Hubberts peak (Gever et al 1991). The production of all conventional hydrocarbons will soon begin to decline and supply shortages will be inevitable (Figure 2) (Bentley 2002, Campbell 2004).

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Figure 2.
Known and projected production of all hydrocarbons from 1930-2050 (Campbell 2004).

Global natural gas reserves are difficult to assess relative to that of oil due to lack of reliable data, however we do know that the majority of gas left to extract is in the middle east and Russia (Bentley 2002). Global gas reserves are also somewhat less of a viable supply than regional reserves because of the cost and limited capacity to transport gas by ship. To transport gas over the ocean it must first be liquefied and shipped in tankers designed especially for this purpose, then they must bring the liquid gas to regasification facilities of which there is limited capacity. All of these steps lower the energy profit ratio. All of the worlds 156 gas tankers are currently under long term contract. World ship building capacity is 20 ships/year and the U.S. has ordered 18 ships for delivery by 2008 (Duffin 2004).

Understanding the regional gas supply is important because gas is most easily transported by pipeline. U.S. gas production peaked in 1973 and production has remained relatively constant for the last two decades (Figure 3) (Paris 2004). More recently new wells have been progressively smaller and now average 56% depletion in the first year. Over the last few years drilling has increased while production has declined. The demand for gas is projected to increase 50% by 2020 and the U.S. known reserves are expected to last less than 8 years (Duffin 2004). Global natural gas production is expected to peak within the next 20 years and with a 2% decline in North American gas production, supply is expected to fall short of projected demand by around 2008 (Bentley 2002, Duffin 2004).

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Figure 3. U.S. natural gas production over time (Paris 2005).

U.S. oil production peaked in 1971, however unlike natural gas, oil is more easily transported, which makes understanding global production important (Bentley 2002). The peak of conventional global oil production is expected to occur sometime this decade and many experts believe we may have already reached a production plateau (Bentley 2002, Gever et al 1991, Pirog et al 2001). Part of how peak oil production is estimated is by knowing the peak of oil discovery, since more oil can not be produced than is discovered (Figure 4) (Ivanhoe 1997).

Global oil discoveries peaked back in 1962 and have declined steadily ever since (Bentley 2002). We now consume approximately 5 barrels of oil for ever new barrel discovered each year, using increasingly more of our reserves from past discoveries (Figure 4) (Ivanhoe 1997). The trend that is perhaps most discouraging is the dramatic drop and progressive decline in the energy profit ratio since the 1970’s (Gever et al 1991). Demand for oil continues to grow at about 2% per year (Wood et al 2004).

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Figure 4. Known and projected discoveries and production of the global oil supply (Ivanhoe 1997).

These trends indicate that if we continue on our current consumption path we will soon experience fossil fuel supply shortages.


The U.S. food system has gone through three main periods; expansion, intensification and saturation. The development of these periods has brought the current food system to a state of dependence on non-renewable fossil fuels. Natural gas is required for synthetic nitrogen fertilizer and oil is required for the transport of farm inputs and outputs. These fossil fuels are finite resources and mounting evidence supports the hypothesis that their production will soon go into terminal decline. The current food system is also degrading the natural systems it depends on for its existence.

The main conclusions of this study are; (A) The current food system is unsustainable because it is overly dependent on non-renewable fossil fuel resources which will soon become more scarce (B) This posses a threat to food security, because with the current system, fossil fuel supply shortages mean food supply shortages (C) To insure food security the current food system should be transformed into a system that efficiently uses local renewable energy, enhances the regeneration of renewable resources and is ecological sustainable. It is time that we leave behind the saturation period of agriculture and develop a new more efficient and sustainable system.

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Tags: Food, Fossil Fuels, Natural Gas, Oil