As many people who know me (and even some who don’t) are aware, I am passionate about local food.

Why? Buying locally keeps money in our local economy; it gives us access to fresh healthy food; it intensifies our connection with place, seasonality and climate; it ensures our local and regional food security; it allows us to have a greater connection with the people who grow our food and to know with certainty that those farmers are practicing their craft in a way that’s healthy for the land, animals, and plants they grow.

Surprisingly, one of the reasons most commonly given in support of local food is not as clear-cut as it may seem: Local and regional foods are shipped short distances and so are more sustainable than food shipped thousands of miles. Right? Not always.

It turns out when looking at the carbon footprint of food, miles-to-market is just one small factor in the equation. Of equal importance is how it’s grown, how it’s stored, and most importantly for this discussion, the methods of transport used to get it from the farm to your table.

I was first tipped off to this by a 2006 study undertaken by the Stockholm Consumer’s Association. Broccoli is commonly imported to Sweden from two sources, Spain (3,200 miles away), and Ecuador (12,000 miles away). Using the food miles method, you might assume that the Spanish broccoli is more sustainable than the Ecuadorian, right?

The researchers actually concluded the opposite: the Ecuadorian broccoli produced just 40% of the carbon emissions of the Spanish grown broccoli. Why? It all came down to efficiencies of scale. The Ecuadorian broccoli was frozen and transported via barge. The Spanish broccoli was shipped by truck, with much worse fuel economy per pound of food transported.

To further illustrate this, consider the relative fuel economy of the following modes of transport moving food a hypothetical 100 miles. Assuming they are all packed to average capacity, an average household vehicle hauling 25 pounds of groceries gets the worst fuel economy, using .13 gallons of fuel per pound of food. A large freight plane uses about .002 gallons of fuel per pound of food, followed by a light duty truck at .001 gallons per pound. A semi is surprisingly efficient at .00027 gallons per pound of food. By far the most efficient means of travel is a barge at a tiny .0000081 gallons per pound of food.

So if simply looking at food miles isn’t the answer, what’s an eco-conscious eater to do? It would be nearly impossible to calculate the precise carbon footprint of all the items on your dinner plate – you’d have to know from where they originally shipped, by what method, how full the truck or barge was, and what fuel economy it got. In addition, you would need to know exactly how it was farmed, how long it was stored, at what temperature, and in what sort of facility.

Here are a few rules that can help you make good choices without getting lost in the details:

Eat Organic
Though it’s true that many organic farmers use equipment that relies on fossil fuels, organic agriculture has been shown to have a substantially smaller carbon footprint than conventional farming. The reasons are two-fold.

First, organic farming focuses on building the organic matter (carbon) in the soil by using cover crops and composted animal manure. This carbon can’t then get released into the atmosphere. Conventional farming, in contrast, usually depletes organic matter in soil.

Secondly, conventional, chemical fertilizers and pesticides are made from fossil fuels and require quite a bit of fossil fuel energy to produce. Organic fertilizers are based on natural ingredients that are much less energy intensive.

Eat Seasonally
In our Wisconsin climate, a fresh tomato in April is either shipped from a warmer climate or grown locally in a hothouse. Unless that hothouse is using solar or wind power, either of these choices are going to be bad in terms of carbon output. Why not instead wait until August to eat your tomato—after all, they taste better that way! Instead, in April focus on foods that are in season in spring: the first dainty local greens, herbs, asparagus, and morel mushrooms.

Seasonal eating has the added benefit of being incredibly tasty, and it fosters all sorts of creativity in your kitchen. You’ll find yourself becoming attuned to the seasonal and climactic rhythms of our area. Cooking will never be boring again!

Avoid Airlifted Foods and Food Transported in an Inefficient Way
There are few perishable products that are too delicate to withstand a long distance trip via land or sea, and are flown in instead. South American asparagus, blueberries, cherries, raspberries, and bell peppers from Holland are some common offenders. Fresh herbs are often airlifted from California or Mexico.

Hardier products like bananas and Argentine apples are shipped via barge, and most California and Mexican produce is shipped via semi. These represent a better choice when you just have to have something that’s not in season locally.

In addition, consider methods of transport used by local farmers. For example, one of our suppliers, Keewaydin Organics, ships products for a number of farms in their area (Viroqua, WI). By filling up their large truck every Wednesday, they are eliminating the need for several small trucks to make the weekly trip into Madison. We encourage all of our farmers to increase their efficiency in ways like this—it’s just as good for their gas bill as it is for the environment!

Eat Whole, Unprocessed Foods
According to a University of Michigan study, 23% of the energy used in our food system is in processing and packaging. By choosing whole, unprocessed foods, and by buying in bulk, you are cutting these steps out entirely.

Pay Attention to Your Link in the Food Chain
A whopping 30% of the energy used in our food system is at home, in refrigeration, cooking, and dish-washing. That’s not to mention the petroleum used driving to purchase food, or the energy wasted when uneaten food is thrown away. Doing everything you can to reduce your energy use at home can go a long way toward making your food more environmentally sustainable.

When you can, walk or ride a bike to pick up groceries. Make sure that your fridge is as energy efficient as possible, and if not, consider purchasing a new one. Look into the possibility of a solar hot water system for your house or support MG&E’s renewable energy options. Only buy and cook what you can eat, and compost any food waste rather than sending it to a landfill where it will be converted to methane (a greenhouse gas). Lastly, consider growing some of your own food, thereby reducing almost all of that food’s carbon output.

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