Flaws in the Food Miles Concept

There are several flaws in the arguments that imports should be decreased on the grounds of food miles.

First, increased energy use in the local production and storage of goods may more than offset the energy saved in transport if, for example, greenhouses are used to grow warm weather crops in cool climates. A lifecycle analysis is required to compare these costs. Such an analysis should also address the impact of other pollutants ignored by the food miles concept, that need to be factored into decision-making. These include those generated in the production of agricultural inputs such as chemical fertilizers, and in the production process itself, such as methane.

Second, the mode and scale of transport are important determinants of the quantity of energy used. Sea transport has a relatively low environmental impact, followed by rail, road, and air transport. Scale problems in measuring distance traveled relate to the size of the vehicle. For example, 10t of grain traveling 1,000km in a 10t truck uses less energy than 10t of grain traveling the same distance in 20 half-ton trucks. This example illustrates that a better measure would be energy use per ton of product, rather than distance traveled per item.

Third, food miles emphasizes the use of one input (distance in its simplest form, and energy use or carbon emissions in the more sophisticated version), but ignores others, such as labor and capital. It also ignores negative externalities related to those inputs, such as the chemicals used in the production process.

Total lifecycle analysis: transport and other pollutants

Using distance traveled as the sole indicator of resource consumption (reflected in the price of goods) disregards use of resources (and costs) of production outside the transport sector. An obvious example of this is the use of (subsidized) gas in some northern European countries to heat greenhouses for producing tomatoes that could be grown in natural sunshine in Spain or Morocco. A UK study undertaken for DEFRA (2005) compares the energy use and emissions in growing tomatoes in the UK versus importing them from Spain. The trade-off in this case is between the additional gas used in the UK for heating, and the fuel used in road transport.⁶ The conclusion was that food miles alone is not an adequate indicator of energy use or carbon emissions, or even of more general environmental impact.

The global warming potential of methane (CH₄) and nitrous oxide (N₂O), are over 20 and 300 times higher, respectively, than that of carbon dioxide (CO₂). These environmentally damaging substances are generated during the production of certain agricultural inputs (N2O in fertilizer production) and the farm production process (CH₄ in cattle-raising). Pollution levels may vary in different countries due to natural variations such as soil type or climate. A lifecycle analysis can quantify these variations and take the various environmentally damaging substances into account.

Mode and scale of transport

The food miles concept, at least in its simplest form of calculating distance, does not address the financial and environmental costs of different transport modes. Carbon emissions for sea transport are 15% of those for transport by road. Grams of carbon emitted per ton per kilometer (g/t/km) are 15 for sea and 98 for road transport, respectively. Air transport, however, emits 570g/t/km according to DEFRA estimates, which is a figure undoubtedly subject to some uncertainty depending on the size of the vehicle, container, or ship (DEFRA 2005). Road transport also has associated costs, including congestion, infrastructure, accidents, and noise. These are real, if difficult to calculate, costs that should be taken into account. Nonetheless, the argument here is that it is primarily the mode of transport, not the distance, that matters.

No account of non-transport costs

The idea that a single variable can be used as a basis for decision-making is obviously flawed. It is reminiscent of Ricardo’s labor theory of value, in which the price of a commodity reflects the hours of labor gone into its production. According to this theory, if it takes one hour to catch a rabbit and two hours to catch a deer, the deer should be valued at twice the price of a rabbit in the market. The problem here is that no consideration is given to: (i) other inputs such as the capital needed to catch the animals; and (ii) demand for the product, that is, the value of a deer or rabbit to consumers. For an appreciation of the total resource use from production to consumption, calculating carbon emissions (in terms of fuel cost and environmental damage) is not enough; other factors, such as the cost of capital, land, and labor, also need to be taken into consideration (Gillespie 2008). The labor theory of value went out of fashion in the 19^th century, when it was recognized that prices are determined by demand-side as well as supply-side considerations. The carbon theory of value suffers similar limitations.

The share of transport costs in the total of resources used in the production, processing, and transport process is important in determining whether to purchase locally produced goods. Although transport is relatively energy intensive, the contribution of energy costs to total costs is low if the share of transport to total costs is low. Other costs related to non-carbon inputs (such as those associated with the use of pesticides in agricultural production) should also be considered.

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