Comparing the carbon footprints of urban and conventional agriculture

 

Earlier this month, here in the UK, I stumbled upon an episode of Tim Harford's More or Less on BBC Radio 4. Tim interviewed Jason Hawes, a researcher from the University of Michigan. Jason and his colleagues recently published this article, Comparing the carbon footprints of urban and conventional agriculture, in the academic journal Nature Cities. This publication is not to be sniffed at. Nature Cities is a new offshoot of the esteemed academic journal Nature no less. 

Now, I'm not going to mince my words. For allotmenteers out there, Jason's research findings make sober reading. Their results suggest that low-tech urban farming, the sort of vegetable production we do in our home gardens and allotment plots, emits six times more carbon into the atmosphere per serving of food than conventional industrial agriculture. Wait, what? Gah! 

Initially, that depressing finding sounds just baffling. How can it be true? This is the exact question Tim put to Jason in his interview. Tim asked how a carrot grown from seed just metres from a gardener's back door can possibly produce, on average, six times more atmospheric carbon emissions than a carrot grown hundreds, if not thousands, of miles away, shipped to processing facilities and supermarkets ever before it reaches ones back door. 

Jason's answer is simple: economies of scale. In this regard, the average allotmenteer or home gardener is at a distinct disadvantage. Just look at the photo of my allotment plot above. You can see I'm growing a healthy looking little patch of broad beans intermixed with garlic in the foreground, but just look at that shed in the background. Squint a little harder through the overwintering black currant bushes and you'll see another shed, and another, and another, a total of four in this one photo. The problem reveals itself. On an allotment site, pretty much every allotmenteer builds a shed, owns a wheelbarrow and a multitude of trowels, forks, water barrels, compost bins, the list goes on and on. This doesn't only occur across the site it also occurs through time. As one allotmenteer leaves knocking down their shed and taking their tools, another person takes over buying a new shed and new tools. Jason's research revealed that this activity occurs at such a feverish pace on allotments that plot holders can never pay back this up-front carbon investment, regardless of how long they hold their plots. That seed grown carrot suddenly becomes very carbon costly. Sigh...

To assist in mitigating these problems, Jason and his colleagues offer several suggestions including thinking twice before investing in that new greenhouse and taking full advantage of recycled resources. Interestingly, they also suggest growing produce that are grown commercially in particularly carbon-intensive ways. Tomatoes, for example, fall into this category due to the fact they are often farmed in carbon guzzling heated greenhouses. 

This research has definitely changed the way I think about my own allotment. For example, I'm now contemplating far more seriously the idea of transforming my plot into a soft-fruit bush and top-fruit tree nursery. I find the idea of raising woody perennials to give away to my fellow gardeners to sequester carbon across the city for years to come very appealing. How I convince the Council to permit such activity is a conundrum for another day.