Even gardens have a carbon footprint. Here’s how to reduce the climate impact of urban farming

Urban gardening might seem fairly innocuous when it comes to its overall carbon footprint, but when compared to conventional agriculture, a study released earlier this year would suggest otherwise. 

The study, published in January in the science journal Nature, found the carbon footprint of food from urban agriculture is six times greater than conventional agriculture.

But there are ways that gardeners can reduce their impact. Let’s take a look at what’s at play.

A look at the study 

The study employed citizen science at 73 urban agriculture sites (think co-operative or collective gardens, not necessarily your backyard garden) across Europe and the United States. 

It compared food from large-scale conventional agricultural farms and urban agriculture sites, including professionally managed urban farms, individual gardens and collective gardens.

“The primary contributor to the carbon footprint on our sites that we studied was actually the infrastructure that was invested in growing food,” said Jason Hawes, a PhD candidate in the University of Michigan School for Environment and Sustainability and lead author on the paper. 

While some studies have previously looked at high-tech gardens such as vertical farms, researchers looked at low-tech urban farms.

Hawes said there’s an embedded carbon footprint in the materials used in your home garden — things like raised flower beds, trellises and tools.

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“It’s really important to try to find reused or reclaimed materials to invest in the garden because that becomes a really important part of the carbon footprint,” said Hawes. 

“Whatever you put in at the very beginning often has a really long-term impact.” 

But Hawes says if you already have equipment on hand, don’t throw it out.

“If it’s already there, keep using it because you’re just going to keep producing more food and more social goods with those materials.” 

A different kind of community garden 

Some collective gardens in Alberta are already taking measures to reduce their impact on the environment. 

It’s still early in the season, but those behind the Star Garden in St. Albert are getting ready for growing season.

Tucked behind the Star of the North Retreat Centre, the garden is on land loaned by the Oblates. 

The garden grows a variety of vegetables that volunteers can take home. All additional produce is donated to the St. Albert Food Bank. 

Gardeners use techniques they believe contribute to sustainability.

“We’re kind of returning to … old-school practices of gardening, so it’s a deep mulch, no-till garden,” said Clint Porritt, co-ordinator for Star Garden.

“The deep mulch part is this idea of feeding the soil in a natural way.”

But how do you start a garden on packed ground without tilling?

It starts with cardboard. 

Two men standing in a yard, cardboard lying on the ground with mulch and soil on top.
Clint Porritt and a volunteer prepare the cardboard base to the garden beds. (Submitted by Clint Porritt )

“What we did is we put cardboard down, which is no cost to this type of gardening.… We dumpster dived for cardboard,” said Porritt.

Once the cardboard is sourced, it’s just a matter of making a bed right on top of the grass. 

“We laid it down. We soaked it. We put wood chips on top.… On top of the wood chips we just put straw, leaves, grass clippings, any type of organic material we can get our hands on for free.” 

Almost everything at the garden is donated, down to the wood and toilet paper rolls they used to create seedling trays, so they aren’t adding to their carbon footprint by buying new materials.

Mulch over tilling

The Star Garden was inspired by gardening pioneer Ruth Stout, who popularized deep-mulch gardening in the 1950s, a method often referred to as “lazy gardening.”

Porritt said as a hobby gardener, Stout had to compete with conventional farmers to get her garden tilled. One year, fed up with waiting, she decided to try something new. 

“She just went to a farmer and she got hay bales that weren’t usable anymore to feed cows with,” said Porritt. 

“She brought them to her yard and she spread them out six to eight inches deep, and she planted her garden into that spoiled hay because she was sick of waiting to get her garden tilled.”

And it worked.

Wooden crate with lines of toilet paper rolls in it, packed with soil, and onion seedlings sprouting.
Local woodworking students created seedling holders for the Star Garden in St. Albert. (David Bajer/CBC)

A major benefit of this type of gardening is it’s really efficient in keeping soil moist. 

Porritt said that in the year the garden launched, it was watered about 10 times.

Last year’s record drought year meant the garden needed a bit more water, but Porritt estimates they watered the grounds only 20 times the entire year. 

“As you dig into the soil you’re actually drying it out, you’re disrupting all these microbial networks that are at work in your soil doing good things, keeping your soil healthy and diverse,” he said.

Tips for reducing garden’s carbon footprint

Hawes doesn’t want his study to discourage people from growing their own foods.

Instead, he wants to encourage people to keep an eye on how they garden. 

The study suggests that maintaining infrastructure for as long as possible and leveraging the urban waste stream, such as by managing your own compost and using rainwater, can drastically improve a garden’s carbon footprint. 

Hawes says with municipal buy-in, this is easily achievable. 

“If cities were able to make recycled inputs, so things like construction waste or reused wood, reclaimed windows, things like that more available to gardeners,… the sites we studied could be climate-friendly if we compare them to conventional agriculture,” said Hawes.

Overall, he says the social benefits of gardening outweigh the carbon footprint.  

“Whether that means giving some tomatoes to your neighbour or, you know, having people over for a garden party, all of those things are important.” 

Keeping an eye on which vegetables you grow is also important. Hawes says some vegetables — when conventionally grown — have a larger carbon footprint. 

“Tomatoes were a really good thing for urban farmers and gardeners to grow because they have a relatively high carbon footprint in their conventional supply chains,” said Hawes. 

He says asparagus is another vegetable that has a large carbon footprint, in part because of the travel needed to bring this produce to grocery stores. 

Yard with mounds of leaves, grass clippings, and other organic matter.
The Star Garden’s plant beds with a fresh layer of leaves, grass clippings, and other organic matter. Underneath is a thick layer of mulch. (David Bajer/CBC)

For Porritt, growing vegetables has been a means to reconnect with nature.

“As you grow your own stuff you interact with the environment, you have a deeper appreciation … for the natural world,” he said.

“You start seeing yourself as part of [nature], not as something over it, or better than it, but actually kind of something … [you] can work alongside it, and also be a partner in nature.”

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