Environmental Engineering Reference
In-Depth Information
Air freight has shipping containers and pallets that are suited for different types of aircrafts.
They have standardized dimensions and weights that are regulated by the International Air
Transportation Association (IATA).
INDICATORS OF TRANSPORTATION DISTANCE
Food miles
Food miles is an indicator of the distance food has traveled from where it was produced to the
consumption point. The term has been embraced by many environmentalists with the idea that
transportation has the largest impact in the whole cycle of food production and distribution;
however, food miles have some limitations, such as:
1.
Not indicating the transportation method (e.g., plane, large truck, small truck, vessel, or
train).
2.
As a corollary of the previous, it does not reveal the real fuel consumed during transporta-
tion (from the most energy consumed to the least per ton of product: plane > large truck >
small truck > train > vessel).
3.
When used out of context, it diminishes the effects of other impacts.
The real impact of distance when transporting foods depends on the caloric content of the
food and the transportation method. Perishable produce transported by plane, such as lettuce,
has a high impact in terms of energy spent in relation to energy content of the food product.
An iceberg lettuce flown from California to the United Kingdom by plane needs 127 calories
of fuel for every calorie provided by the lettuce (Jobson, 2007).
Ton-miles per gallon
This is a transportation indicator more specific to the method of transportation. It basically
indicates how many miles 1 ton or goods can be transported with 1 gallon of fuel. Variations
of this indicator are “tonne-km per liter” and “liters per 100 km per tonne.” Caution should
be exercised with the term
ton
, which depending on where is used may indicate different
amounts of mass. In countries using the International System, a ton is equivalent to 1000
kilograms (2205 lb), which sometimes is referred to as metric ton or as tonne. Under the
imperial system, ton has two variations: the US short ton or net ton, which is equivalent to
2000 lb and the British long ton or gross ton, which is equivalent to 2240 lb. In the United
States, the long ton is used in restricted industrial fields (National Institute of Standards
and Technology [NIST], 2006). A similar confusion can occur with gallons. In the United
States, 1 gallon is equivalent to 3.785 liters, whereas in the U.K. it is equivalent to 4.546
liters.
Ton-miles per gallon is a relatively straightforward indicator for the purpose of comparing
fuel efficiencies among different transportation methods; however, it has some limitations and
simplifications that need to be considered:
It does not include the speed of the vehicle. Vehicles have a range of speeds and the con-
sumption of fuel depends on the speed.
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It does not specify if the tare (unloaded mass of the vehicle) is included in the calculation,
which in general it is not.
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