Food Waste Recycled as Biofuel

Jose Garcia
November 29, 2011

Submitted as coursework for PH240, Stanford University, Fall 2011


Biofuels have gained a lot of attention as the concerns over fossil fuels rise. Biomass-based fuels provide a great alternative since they can be generated from crops, tires, computers, and pretty much anything else other than nuclear waste. [1,2] One particular avenue being explored is the use of food waste, which is readily available and can be converted into biofuel through various processes. The United States alone produces an estimated 30 million tons of food waste every year. [3] Not only does this waste contain energy that could be reused, but also has a detrimental effect on the environment.

Food Waste in the United States

It is estimated that the food industry accounts for 8% of all the energy used in the United States, and studies have found that over 27% of this food is thrown away. [4] Not only do these actions neglect a valuable source of energy, but presents an inefficient use of the energy invested in producing the food in the first place. In fact, food comprises one of the largest components of waste in the United States. [4] However, less than 3% of the food waste generated in the United States is recycled. [3] The rest of this waste is decomposed in landfills where it produces foul odors, can pollute groundwater, requires large amounts of space, and generates large amounts of methane gas, which has 20 times the global warming potential of carbon dioxide. [3,5] Recycling food waste, therefore, is one of the most environmentally friendly processes for generating biofuels. In fact, it is a much better alternative to growing crops for the purpose of generating biofuel.

Studies have shown that the carbon debt of growing crops to produce biofuels is significantly high; the net amount of carbon emissions are worse over the next couple of decades than would be caused by using fossil fuels. [1] Additionally, using common crops like sugar cane and corn to generate biofuels creates turmoil in the world wide food market as the prices of the required food products fluctuate to meet the demand for fuel. [1]

Recycling Food Waste

Food waste may be recycled in a number of different ways. Among these is the use of yellow grease and other waste greases to fuel diesel engines. Restaurants provide a steady supply of these fuels since they are a byproduct of cooking oils, either from animal fats or plant oils. Using this fuel not only avoids generating more waste, but also provides a more eco-friendly fuel which generated half as many greenhouse gases as standard diesel fuels. [6]

Another method for converting food waste into energy is through the use of an anaerobic digester. This device uses a series of processing stages where small organisms break down biomass into methane gas, which can then be used to power electric generators. [7] This process has been found to generate approximately 260kwH of electricity per wet ton of food waste applied. [7] Based on the 30 million wet tons of food waste generated each year in the United States, about 8 billion kwH could be generated each year through this process. This is enough energy to power over 1.3 million California households, about 10% of the state. [7]

Yet another option, pyrolysis, presents one of the most versatile biofuel generating process explored. Through the process of heating biomass with limited oxygen present, sewage sludge, turkey offal and many other types of waste can be converted into pyrolysis oil and other biomass liquids that may be directly used as fuel. [2] It also presents an efficient conversion method since it is estimated that the process yields 85% of the energy stored in the waste. [2]


The benefits of recycling food waste are clear, increased energy production, lower carbon emissions, and lower space requirements for landfills. Although the introductory costs are high, various food production companies are beginning to see the long term benefits of implementing recycling infrastructures in their plants.

Surely a nation cannot satisfy all of its energy needs through food waste generated biofuels. However, the benefits are significant and the alternative comes at a cost to the environment that is unnecessary.

© Jose Garcia. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] J. Fargione et al., "Land Clearing and the Biofuel Carbon Debt," Science 319, 1235 (2008).

[2] N. Davis, "Turkey Fuel? Factory to Turn Guts Into Crude Oil," National Geographic News, 25 Nov 03.

[3] A. Martin, "One Country's Table Scraps, Another Country's Meal," New York Times, 18 May 08.

[4] A. D. Cuéllar and M. E. Webber, "Wasted Food, Wasted Energy: The Embedded Energy in Food in the United States," Environ. Sci. Technol. 44, 6464 (2010).

[5] P. Forster and V. Ramaswamy, "Changes in Atmospheric Constituents and in Radiative Forcing," in Climate Change 2007: The Physical Science Basis (Cambridge, 2007). [Available online from the Intergovernmental Panel on Climate Change.]

[6] C. Saillant, "Recipe for Fuel Calls for Grease," Los Angeles Times, 31 Oct 03.

[7] "Annual Energy Review 2010," U.S Energy Information Administration, DOE/EIA-0384(2010), October 2011.