Meat Eaters Guide: Methodology - Environmental Working Group

Meat Eaters Guide: Methodology
An astounding amount of meat – on average about 20 percent – is wasted at the retail, institutional
and consumer level. The GHGs associated with producing and discarding wasted food is calculated
using a recently commissioned USDA study (Muth, et al 2011) of consumer-level food loss estimates
at the retail and household levels, and other literature sources for estimates of fat loss (included in
USDA data) and moisture loss (not included in USDA data) during cooking.
USDA states that these data are more accurate than previously published USDA data, but they are
still likely underestimating actual waste. 29 At least two other major studies have generated higher retail
and consumer waste estimates. 30 Given data limitations, our model considers only the waste from
the retail and consumer phases (including institutions and restaurants) for each food commodity. Our
calculations do not include wasted product that remains on farmers’ fields or waste generated from
processing. In the absence of solid data, our model conjectures that half of the consumer waste (excluding
fat and moisture losses) occurs prior to cooking and the other half occurs after cooking. The
overall model also accounts for fat and moisture losses during cooking, as well as waste that occurs
prior to cooking – including retail waste and non-edible share (such as egg shells or broccoli stems).
For meat products, only the edible share is included in the model based on co-product allocation at
the production stage.
Based on that waste percentage, we calculate the GHGs associated with the amount of a given product
that is needed to produce 1 kg of consumed product. In other words, if the production is P kg, and
the waste percentage is W percent, then: P = 1/(1-(W/100)).
Here is how our model works in the case of beef. Recent USDA research shows that 23.44 percent of
the weight of packaged beef is never used, is wasted during cooking or discarded after a meal. 31 This
includes a retail loss of 4.3 percent and further losses at the consumer level. Relative to the consumer
loss portion, available data suggests that 7 percent is fat loss that occurs during cooking and is
included in the USDA waste data. An additional 18 percent of weight loss (relative to product available
after other losses) occurs during cooking from moisture loss, which we assume is not included in the
USDA waste data – this requires production and waste to be scaled up appropriately to deliver 1 kg of
cooked product for consumption. We therefore calculate that it takes 1.59 kg of beef to produce 1 kg
of consumed meat, and 0.59 kg is lost during the retail and consumption phase. 32 Actual waste that
is disposed through landfilling or composting amounts to 0.27 kg, the balance being the fat and moisture
losses during cooking.
All food waste sent to landfills is modeled using the same IPCC first-order model 33 and decay rate
for the food category (for example, all meat is assumed to decay at the same rate, with no difference
between chicken and lamb). The only difference between various food commodities is the estimated
percentage of food waste. We assumed that the landfill was located in a temperate dry zone. (A
temperate wet zone has slightly higher emissions). The food waste that ends up in landfills generates
methane emissions from anaerobic decomposition as well as a small amount of nitrous oxide emissions.
Our model assumes that 23.25 percent of the landfill methane is captured on average (with
credit given for energy recovery) and 21 percent of the methane is flared (EPA2006), and some credit
is given for carbon storage in the landfill. The analysis also calculates emissions from the transport of
16
Environmental Working Group Meat Eaters Guide: Methodology 2011