Fossil energy land

The calculation of fossil energy land needed to produce and transport food has two additional components. The first takes into account how much of your food is grown locally vs. processed and transported long distance. In cell F15, you are asked to enter an estimate of the fraction of your food that is fresh and locally grown. The average fraction for a US citizen is about 25% (selection "b"). If your fraction is smaller than this, the fossil energy required to ship and package your food goes up. Conversely, if your fraction of fresh, local food is larger than 25%, then the fossil energy required to ship and package your food is modified downward. The second modifier takes into account the waste factor for food that results from the harvesting and transporting processes (pre-purchase food loss). USDA figures reveal that there is, on average, a 10% decline from farm weight to retail weight. The 1.10 in the equations represents this value.

For the following food items, fossil energy land is calculated taking these factors into consideration:

• Eggs (cell G28)—The fossil energy footprint of eggs is based on a weight of 0.05kg per egg; 0.05 refers to 1 egg = 50g = 0.05 kg.
• Sugar (cell G35)—The fossil energy footprint of sugar is calculated using 3.85 = Energy intensity of sugar in (Calories/kg) and 4.18 Kj = 1.0 Calories, where Kj = kilojoules (a unit of energy).
• Liquid vegetable oil (cell G38)—The fossil energy footprint of liquid vegetable oil and fat: 0.8 = estimated density of vegetable oil (kg/l) in order to convert liters into kilograms (recall that density = mass/volume).
• Tea and coffee (cell G39)—The fossil energy footprint of tea/coffee is calculated using 18 = Energy intensity of tea/coffee in (Calories/kg) and 4.18 = Conversion factor for Calories to Kj.
• Eating out (cell G43)—The fossil energy component of eating out is calculated assuming that 20 Mj is consumed per meal eaten out (estimate).

Arable land

The quantity of arable land required to grow food follows a similar equation to that of fossil energy land:

where the carbon sequestration ratio is the amount of land of the crop required to sequester 1 Gj energy's worth of C. Here, energy means food calories. The energy intensity ratio is the amount of energy (in Gj, which is an energy quantity analogous to calories) produced by one Kg of crop. Again a waste factor of 10% is used to estimate the true amount of land needed to grow the crop.

The arable land footprint of the garden is simply the area of the garden. The arable land footprint of dining out is calculated as (2900/365)*(.5) = m² of arable land per meal. This value represents the footprint area of average per capita food consumption not dining out (2900) per day (÷365) based on items grown in arable land only, and assuming that each meal eaten out provides one half of the day's nutritional content (*.5).

The quantity of pasture land required to grow food uses a simple equation:

where land requirement is the amount of land needed to produce one Kg of meat. This is estimated using USDA data on the number of animals per hectare and the amount of meat yield per animal.

The pasture land footprint of dining out is calculated as (11500/365)*(.5) = m² of arable land per meal. This value represents the footprint of average per capita food consumption without dining out (11500) per day (÷365) based on items grown in pasture only, and assuming that each meal eaten out provides one half of the day's nutritional content (*.5).

Sea

Calculating the quantity of ocean area required to produce fish employs the same equation as that of arable land:

OTHER SPECIFIC NOTES ABOUT FOOD:

1. Food source (cell B12): With the exception of the sub-categories 'Eating Out' and 'Garden Area,' all sub-categories in the FOOD section should include only food being brought into the household from an outside source (i.e., not homegrown food).

2. Units: Most units for food items are shown in column C. For wine and juice (cell C40), a standard bottle of wine contains 0.75 liters or 0.75/1.06 = 0.7 quarts.

3. Food quantity consumed per month (cell D12): The following table reports average US per-capita food consumption data for 1996 from: USDA, Agricultural Statistics 1998, Table 13.5, "Per-capita consumption of major food commodities." You can compare your monthly consumption rate to these values to see how you compare to the average US citizen.