Plant Power

One proposed use for vacant land in Detroit is farmland. But what if the land is too polluted to produce safe food? There is a natural way to clean up soil. It's called phyto-remediation, and it basically puts plants to work removing toxins as they are handling their regular business of extracting water from the earth.

Here are the stories of two Detroit groups currently working in the realm of phyto-remediation.

Phyto-remediation 101: Sunflowers and schools

Brownfields are parcels of land that were once used in a potentially polluting manner and oftentimes harbor ground pollutants. The city of Detroit is littered with them. Technically, the entity that polluted the land is responsible for its clean-up, but there are so many loopholes that the very existence of a potential brownfield can act as a barrier to its reuse.

To further complicate matters, there are types of uses that (for good reason) require higher levels of soil cleanliness — such as a school or a residence.

One expensive but sure way to remove polluted soil is to actually cart it away and replace it with clean soil. Not only is this method costly, but it begs the question: where does this toxic soil end up?

Co-lab* is a small design firm oriented towards sustainable architecture and planning projects. Co-owner Vibeke Schroeder Vendena is a native of Denmark who first worked Detroit in 1996 and became fascinated with the city. After several other trips, she returned in 2001 to attend Cranbrook and became involved in a landscape design project at Bunche Elementary on the Eastside near the Heidelburg Project.

After testing the soil, the team found some areas had high levels of heavy metals, like lead, that can be dangerous for children. They quickly realized the cost-prohibitiveness of removing and replacing all of the soil, so they began researching phyto-remediation that uses, as Vendena puts it, "plants as pumps."

They learned that there are certain plants that are better at this than others. Sunflowers, for example, have shallow roots and are good first-year crops, removing toxins down 8-10 inches. The team then plants native poplar trees and perennial plants like prairie and switch grass which have an expansive root system to go down and extract even deeper toxins.

The sunflowers have already proven to reduce lead in parts of the soil from 1000 to 800 parts per million. Vendena plans to have the soil re-evaluated in a couple of years to test the effectiveness of the other plants they have selected, but is hopeful that the phyto-remediation will be successful as it has been in similar situations in Australia and Canada.

"This is a low-cost solution," says Vendena, adding that it's a solution that could have broad applications around the city. Co-lab* also hopes that "by teaching it to kids, they will think, 'Wow, sunflowers can do this!'"

Biofuel crops grown around the block?

Growing crops for production into biofuels is a burgeoning industry in this country and has typically been done in rural areas. But there is one initiative exploring the feasibility of using land in the city, where ultimately most of the fuel will be consumed.

The bonus, according to this initiative's lead, Brad Jensen, is that the "use of land for biofuel production is preparing, cleaning [the land] for later potential redevelopment." That's right, the very same crops that work well as fuel work well as phyto-remediators.

Jensen is project manager of a program at City Connect Detroit called the Detroit Data Partnership that works to optimize the existing network of data, information and demographics that are really only useful when organized into a digestible format. They also work to make that information available to the city government and nonprofits.

In analyzing all this raw data, Jensen was struck by the sheer quantity of vacant parcels, many of them brownfields. While contemplating potential productive uses of this land, two things happened: he heard a NextEnergy presentation on phtyoremediation and happened to see the sunflowers that Ford Motor Co. planted around the Rouge Plant. He started thinking of these crops in terms of a business model: "This could not just be a good thing to do, but it could pay for itself."

Jensen points out that biofuel production is on the rise nationally (and locally: a plant is in the works for the New Center area), and he realized that where biofuel crops originated from would become more and more important. Transporting crops from rural areas to urban consumers adds a significant cost to whole equation.

He is now working with a team of modeling experts from Eastern Michigan University to study the feasibility of growing biodiesel crops — such as rapeseed, switchgrass and sunflowers — in the city. Lots of unanswered questions remain, like how much land is actually vacant (yes, no one actually knows that magic number), and whether or not there are large enough contiguous parcels that could logistically work as biofuel farms. Environmental impacts need to be looked at, and economic and transportation models need to carried out.

Jensen is on the hunt to secure long-term funding for the study. He hopes it will be completed in 2010. "Our target is biofuel production, but there are ancillary benefits," he says, noting the social impact that greenfields vs. brownfields can have on neighborhoods. What would you rather look at — a typical vacant lot or rows of sunflowers that will ultimately become fuel for your truck? Seems pretty obvious.

Kelli B. Kavanaugh is the development news editor for Model D. This is the latest installment of her ongoing series on sustainability in Detroit. Her past stories have been about community gardens and energy efficient building.

Sunflower photos Copyright Dave Krieger

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