Food Waste and Greenhouse Gases

It is estimated that about 40% of the food produced in the United States is either lost or goes to waste, releasing about 3.3 Gigatonnes of CO2 equivalent of GHG emissions into the atmosphere. The following table enlists the net GHG emissions calculated by the EPA’s Waste Reduction Model (WARM v. 13) for different food material types for five materials management strategies – source reduction, recycling, composting, combustion, and landfilling.

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As per the WARM model, food waste prevention generates net negative GHG emissions because it avoids emissions from the Raw Materials Acquisition and Manufacturing (RMAM) as well as the emissions from the end-of-life management of the food waste. On the other hand, landfilling of food waste generates net positive GHG emissions.

Certain assumptions were made to facilitate the calculations of GHG emissions. For example, the calculations considered only the conventional production practices and did not calculate the emissions for organic production processes. Also, the numbers are used as a general guide that is based on life-cycle analysis conducted using the available data, and don't account for specific climate, supply chain and food type differences.  

It should also be remembered that the total GHG emission reduction would depend on the type of material, their percentage share in the food waste modeled in WARM in the waste stream, and the type of material management strategy. For instance, fruits and vegetables constitute 49.1 % of the of the food waste modeled in WARM in the waste stream in 2010 while beef constitute 9.3 %. The GHG emission reduction from the source reduction of beef (9.3 % X -30.05 MTCO2 Eq/ Short Ton) is nearly 13 times more than the GHG reduction compared to that of fruits and vegetables (49.1% X -0.44 MTCO2 Eq/ Short Ton). However, if we choose composting as the material management strategy, then the GHG emission reduction from composting beef (9.3 % X -0.15 MTCO2 Eq/ Short Ton ) would be about 5 times less than that of the fruits and vegetables (49.1% X -0.15 MTCO2 Eq/ Short Ton). On a per ton basis, the ideal scenario to avoid food waste-related GHG emissions is preventing food waste at source.

In conclusion, the latest version of EPA’s WARM model is a major improvement over the previous version because it facilitates quantification of GHG emissions via organics management modeling, including new source reduction emissions factor for food waste. The utility of the WARM model can be best realized keeping in mind the assumptions and the differential impacts of material types and materials management strategies. 

 J. Buzby, and J. Hyman. (2012) “Total and per capita value of food loss in the US”, Food Policy, 37:561-570.

 Documentation for Greenhouse Gas Emission and Energy Factors Used in the Waste Reduction Model (WARM), (2015), USEPA, available at , 416 p.

Omkar Aphale