Locally Grown Produce

by Brian Dunning
July 14, 2009

Today we're going to be politically incorrect again and point our skeptical eye at another sacred cow: Locally grown produce. Particularly in the United States, but in many other countries as well, one of the newest and fastest growing market segments is locally grown produce. The claims are that locally grown produce is less wasteful of fuel because it doesn't need to be delivered over long distances; it's fresher for the same reason; and it supports a small local organic farmer instead of an immoral megacorporation that sources food from cheap overseas producers.

I discussed one of these claims, about local delivery burning less fuel, in a May 2009 entry on SkepticBlog.org. It must have been pretty inflammatory, because it generated a huge number of comments. Most of them followed this pattern: The commenter begrudgingly agreed with the mathematics of the delivery question, but then claimed that I missed the point completely because the real reason to like locally grown produce has nothing to do with a low carbon footprint of minimal delivery miles. I'm not sure I buy that — virtually everyone I've ever asked says that's what locally grown is all about — but hey, I'm fair, we'll give them all a voice here.

First, let's give a brief overview of the mathematics of local delivery. Think of the traveling salesman problem. This is where you speckle a map with all sorts of random locations. The traveling salesman's problem is to find the shortest possible driving route, called a tour, that visits each of the locations. It's among the most computationally difficult problems in mathematics. But there's a cool piece of free software by Michael LaLena that finds one efficient solution using a genetic algorithm. Try to stump it with a pattern of hundreds of dots that you think will be hard to connect, and the software blows your mind with a surprisingly simple tour that visits all the locations.

Many years ago I did some consulting for a company that was then called Henry's Marketplace, a produce retailer built on the founding principles of locally grown food. Henry's had evolved from a single family fruit stand into a chain of stores throughout southern California and Arizona that sold produce from small, local farmers. Part of what I helped them with was the management of product at distribution centers. This sparked a question: I had assumed that their "locally grown produce" model meant that they used no distribution centers. What followed was a fascinating lesson where I learned part of the economics of locally grown produce.

In their early days, they did indeed follow a true farmers' market model. Farmers would either deliver their product directly to the store, or they would send a truck out to each farmer. As they added store locations, they continued practicing direct delivery between farmer and store. Adding a store in a new town meant finding a new local farmer for each type of produce in that town. Usually this was impossible: Customers don't live in farming areas. Farms are usually located between towns. So Henry's ended up sending a number of trucks from different stores to the same farm. Soon, Henry's found that the model of minimal driving distance between each farm and each store resulted in a rat's nest of redundant driving routes crisscrossing everywhere. What was intended to be efficient, local, and friendly, turned out to be not just inefficient, but grossly inefficient. Henry's was burning huge amounts of diesel that they didn't need to burn. So, they began combining routes. This meant fewer, larger trucks, and less diesel burned. They experimented with a distribution center to serve some of their closely clustered stores. The distribution center added a certain amount of time and labor to the process, but it still accomplished same-day morning delivery from farm to store, and cut down on mileage tremendously. Henry's added larger distribution centers, and realized even better efficiency. Today their model of distributing locally grown produce, on the same day it comes from the farm, is hardly distinguishable from the model of any large retailer.

Compare the traveling salesman's simplified tour to a tangle of crisscrossing bicycle spokes, and the inefficiency of direct delivery between farm and store becomes acutely clear. If we want to minimize the carbon footprint of the entire food cycle, eliminating direct delivery is the easiest place to make the biggest gains. So, right off the bat, the main reason most people prefer locally grown produce is shot down, and shot down in big flames. But let's turn to the SkepticBlog commenters and see what people had to say.

As did a number of readers, Ian pointed out that you have to consider the total price. Not just the cost of distribution, but also the cost of the retailer's wholesale purchase. Total them all up, and in some cases it might be cheaper to buy from ridiculously far away:

...Wal-Mart [buys] fruit from South Africa, coffee from Kenya, etc. Flying this produce around the world is clearly using more fuel than even an inefficient model for distributing food locally. The efficiency comes not from reducing fuel usage, but from paying significantly less for the produce.

This was underscored by another poster, "Old White Guy":

As someone who spent a good chunk of his life controlling distribution for several large companies, I can say the only thing that matters is getting the product to the point of sale as inexpensively as possible. If that [means] the cheapest wine in the store comes from another continent, so be it.

This suggests that it some cases, huge container-sized purchases might still be cheaper for the large retailer, even though their delivery produces a lot of wasteful emissions, and their production might be with some god-awful third-world high-pollution child-labor dogs-and-cats-living-together environmental disaster. That might be true in some cases, but those would be the exception, not the rule. Most of the time, produce is cheaper from those countries because the native growing conditions are much better for that particular crop. Tomatoes flourish in Spain but require heated greenhouses in the United Kingdom, and so the overall energy efficiency of growing them in Spain and transporting them overseas to the UK is actually better.

A number of people who disagreed with my article repeatedly referenced Michael Pollan's book The Omnivore's Dilemma. Pollan devotes one of the book's four sections to the practices of holistic cattle farmer Joel Salatin. One of Salatin's rules is that, in the interest of a minimum carbon footprint, he won't ship his beef at all; customers have to drive to him to pick it up. While I applaud Salatin for having the right idea and the right motivations, I don't believe he thought through this particular point very critically. Salatin should instead design practices that more directly address his desire: He should allow only shipments that use a minimum amount of fuel per pound of beef delivered. Instead, he adopts a rule that might put hundreds of cars and vans on the road, each delivering only a few pounds of beef. Salatin's solution is emotionally satisfying and makes for a fine sound bite, but its underlying science is flawed and counterproductive to his stated goals.

The elephant in the room on Joel Salatin's farm is that his near-total self-sufficiency methods require an outrageous 550 acres to support only 100 head of cattle and a herd of pigs, plus some turkeys and chickens. Most of the acres are used to grow the feed and raw materials the animals require. I didn't find any valid defense of this, and Pollan's book simply avoids the issue. Typically, pasture-fed cows require half an acre each, so Salatin is using about ten times as much land as he should [Correction: This is true only in places with the best conditions. 550 acres could support anywhere between zero and 1,000 head of cattle, depending on where it is. —BD]. Such wasteful land usage might work well in the case of a high-end boutique retailer like Joel Salatin, but it's clearly well beyond the limits of practicality for the world's real food needs.

The overall picture is often a lot more complicated than simply "locally grown". Let's say you want sheep or dairy products, and you live in New York. Where are those products going to come from? Certainly not from anywhere local. If you get them from a state or two away, which is about as local as possible, what went into their production? A lot of feed, for one thing. But spin the globe and look at New Zealand. New Zealand has the world's most efficient sheep and dairy industries, and one big reason is their climate and conditions that allow year-round grazing. According to the New York Times:

Lamb raised on New Zealand's clover-choked pastures and shipped 11,000 miles by boat to Britain produced 1,520 pounds of carbon dioxide emissions per ton while British lamb produced 6,280 pounds of carbon dioxide per ton, in part because poorer British pastures force farmers to use feed. In other words, it is four times more energy-efficient for Londoners to buy lamb imported from the other side of the world than to buy it from a producer in their backyard.

And yet many of the same people who are so vocal about a minimum carbon footprint consider this massive net energy savings to be immoral because it includes overseas transport. Why? Is it a geopolitical preference? Is it a matter of supporting farms from your own country instead of sending money overseas? OK, fine, that's an absolutely valid point of view. But if your true motivations are political, don't greenwash them and claim that you're really interested in environmental science.

If it's support for small business, if you'd rather support someone like Joel Salatin than a megacorporation like Wal-Mart, that's also an absolutely valid point of view. Just call it what it is instead of greenwashing it and claiming environmental awareness. To get the premium boutique experience, Salatin's customers burn way more gas per pound of beef delivered than do Wal-Mart's container ships from New Zealand. If you have other reasons to object to Wal-Mart's New Zealand beef, fantastic; just be aware of what your objections really are. It's more intellectually honest, it's more insightful, you'll learn more, and you're not being disingenuous.

Don't get me wrong, I love farmers' markets. We go to our local one sometimes and it's a fun family event for us. We love the giant, wonderful tomatoes and strawberries that you can't get at the supermarket. But I understand that farmers' markets are more of a community experience than an efficient (or "green") way to buy food. The real reasons to enjoy your farmers' market have nothing to do with it being somehow magically environmentally friendly. Too often, environmentalists are satisfied with the mere appearance and accoutrements of environmentalism, without regard for the underlying facts. Apply some mathematics and some economics, and you'll find that, more often than not, a smaller environmental footprint is the natural result of improved efficiency.

By Brian Dunning
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