Thursday, May 14, 2009
Is local food the greenest choice? New study says no
"Local" is the mantra in sustainable food these days. But should it be? Is eating locally-produced food the most powerful thing we can do to reduce our ecological "foodprint?"
A new study from Worldwatch Institute says no indeed. I love Worldwatch. They crank out study after study with lots of hard data, evaluating the environmental impact of various consumer choices. So useful! So fun to quote!
Don't get me wrong - I'm all in favor of local food. We definitely should support small-scale farmers in our own communities who are growing food organically and sustainably. For years now, I've been writing and speaking in support of them, on this blog and in our books and at various conferences.
There's no question that, all other things being equal, buying food grown nearby is better than buying food that's been trucked for long distances. Less transported food means fewer emissions and a smaller carbon footprint. But as Sarah DeWeerdt points out in this new Worldwatch article, we need to look at the whole production picture - not just how far food was transported from producer to market.
As it turns out, when we look at life-cycle analysis, a "cradle-to-grave perspective" on food products, food miles are "a relatively small slice of the greenhouse-gas pie," says DeWeerdt. In fact, according to a comprehensive analysis last year by Christopher Weber and H. Scott Matthews of Carnegie Mellon University, final delivery from the producer or processor to the retailer accounts for only 4% of the U.S. food system's greenhouse-gas emissions! Materials required for cultivation and processing must be transported too; this transport is considered part of the "upstream" miles and emissions. Such materials include fertilizer, pesticides, animal feed, etc. But the transport of these items, together with transport to market, still accounts for only 11% of the food system's emissions.
What's the source of all the other greenhouse gases associated with agriculture? Production. Primarily, production of livestock. Weber and Matthews from Carnegie Mellon found that a whopping 83% of food-related emissions occur before the food leaves the farm. Tara Garnett, in a recent analysis of a U.K. food system reached similar conclusions.
What you eat may matter more than where it came from
Numerous studies reviewed by DeWeerdt have found that livestock production generates a much higher volume of greenhouse gases than does plant production. Beef and dairy cattle are the worst culprits; DeWeerdt calls them "agriculture's overwhelming 'hotspots' " in terms of greenhouse-gas emissions. A group of Swedish researchers has calculated that meat and dairy account for 58% of that country's total food emissions. In Garnett's study, meat and dairy accounted for half of the U.K. food system's greenhouse gases. Garnett writes, "Broadly speaking, eating fewer meat and dairy products and consuming more plant foods in their place is probably the single most helpful behavioral shift one can make" to reduce food-related greenhouse gases. Weber and Matthews reached a similar conclusion: "No matter how it is measured, on average red meat is more GHG-intensive than all other forms of food. " The dairy industry, in their study, was the second-biggest contributor to greenhouse-gas emissions.
A large proportion of emissions associated with beef cattle and dairy cows are the greenhouse gases methane and nitrous oxide. Methane is 23 times more potent at trapping solar heat than is carbon dioxide; nitrous oxide is 296 times more potent (molecule per molecule). Methane comes from the rear-ends of ruminants such as cows. Both methane and nitrous oxide come from manure, especially the vast, open "waste lagoons" associated with factory farms.
Well then, just how much does food contribute to the planet's overall carbon footprint? I reported on that in a previous post. In 2006, the United Nations Food and Agriculture Organization published a live-wire of a paper entitled "Livestock's Long Shadow." According to that research document, livestock account for 18 percent of all greenhouse gas emissions. And here's the kicker - that's more than all forms of transportation combined! You can easily google that document for yourself. Just read the 3-page Executive Summary in Part I, which summarizes the the whole 400 page report.
After concluding that red meat and dairy are emissions hot-spots, DeWeerdt does go on to review the merits of buying local food. One clear advantage, which Sadie and I talk about in our presentations, is that local food is in general grown by small-scale farmers who are openly accountable for their treatment of the environment and their livestock. The farmers I know who sell food to their own communities welcome visitors to inspect their methods. This is a far cry from industrial producers who keep their exploitive and often abusive operations shielded from public view.
So buy local. But, if you want to contribute to a liveable planet for your grandchildren, eat low on the food chain too. And join me in a tip of the hat to Worldwatch for another fine study.
by Sally Kneidel, PhD
Sarah DeWeerdt. Is Local Food Better? Worldwatch Institute. Accessed May 15, 2009.
Livestock's Long Shadow. United Nations Food and Agriculture Organization. Rome, 2006.
To see my primary post about Livestock's Long Shadow and about Weber & Matthews' research, click here
To see all my, Ken's, and Sadie's posts that mention Livestock's Long Shadow, click here
To see my favorite Worldwatch Institute document, Happier Meals: Rethinking the Global Meat Industry by Danielle Nierenberg, click here
Key words:: Worldwatch Livestock's Long Shadow meat industry local food red meat cattle dairy livestock greenhouse gases carbon emissions food carbon footprint foodprint Sarah DeWeerdt Weber and Matthews Matthews and Weber Carnegie Mellon