Posts Tagged ‘potting mix’

The Carbon Footprint of Gourmet Dirt

Sunday, August 17th, 2008

An interesting story by Joel Achenbach in today’s Washington Post is, on its face, about how the price of potting soil has soared in the past year due to the high cost of the fossil fuels used to manufacture, package, and ship the stuff. But read between the lines and the story is really about how a once humble material has been transformed into an upmarket mixture of largely unnecessary components from across the continent and around the globe — and about how gardening (or at least the kind practiced by many Americans), an activity by definition assumed to be “green,” is anything but.

Bob LaGasse, who represents soil and mulch manufacturers as executive director of the Mulch and Soil Council, explains that consumers demand these high-priced designer mixtures, which a South Carolina-based producer calls “potting soil on steroids.” (Bob LaGasse also happens to be executive director of the Garden Writers Association, representing the people who recommend potting soils and other horticultural products to consumers.) 

It’s virtually impossible these days to find a bag of potting soil that isn’t loaded with synthetic fertilizer. Nitrogen fertilizer, as David Wolfe, professor of plant and soil ecology at Cornell University, has pointed out, is the typical gardener’s biggest contribution to global warming. The manufacture of synthetic fertilizer is extremely energy intensive. And the use of nitrogen fertilizers (whether synthetic or organic) releases nitrous oxide gas, which in Wolfe’s words “has 300 times more global warming potential per molecule than carbon dioxide.” Yet American gardeners have been hoodwinked into believing that applying fertilizer to their plants, whether in containers or in the ground, is as fundamental as brushing their teeth.

In addition to organic matter, from composted clam shells to pine bark, which could just as easily come from local sources but is often shipped from far away, the typical bag of potting soil is also likely to contain perlite transported from the Greek island of Milos and coconut coir from Vietnam, if not peat moss “vacuum-harvested” from Canadian bogs. Then the concoction is packaged in plastic bags, which are piled up and shrink-wrapped on wooden pallets for shipping to nurseries and superstores. In short, the amount of embodied energy and greenhouse gases associated with a bag of potting mix is mind boggling.

All for a few petunia plants likely to end up in a dump after the first frost.