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What's the Dirt on Bioremediation?


a reflection by Rachel RolsethBioremediation

This summer I have had the wonderful opportunity to be a part of Ripple Ecology – a community skillshare group where we are learning how to be good stewards of the earth around us. Our first class was focused on soil pollutants and bioremediation, which is a fancy way of saying how to clean toxic soil with plants, compost, and mushrooms.

Many places in Minneapolis have contaminated soil, whether it is from herbicides, pesticides, oil, heavy metals, or even poisons like arsenic, which are a leftover from former landfills. So what are we to do with all this contaminated soil? Recently the answer has been to do it off site – a truck comes and takes all of the contaminated soil out of your site and cleans it in an industrial process, while another truck brings in safe, clean soil.

A different option is to do it where we’re at with the tools that we have. Christina Elias from the Mashkiikii Gitigan garden taught us about a process to clean soil onsite. The first step is phytoremdiation, healing the soil with plants. 

During phytoremediation, plants pull up heavy metals and other pollutants through their roots. These contaminants travel up into the aboveground parts of the plant. Rather than let the contaminants return to the soil, we pull plants out for the next step, which is composting.

Composting works by a complex food web of bacteria, nematodes, bugs and other microorganisms eating plant matter and breaking it down into healthy, clean soil. While compost is effective at healing contaminated soil, it is important to keep your bioremediation compost pile separate from your regular kitchen and garden compost pile, as there may still be contaminants left after composting. When the compost is finished and looks like rich dirt, it is time to clean the remaining contaminants with mycoremediaiton.

Mycoremediation, or healing soil with mushrooms, uses mushrooms to clean certain pesticides, chlorinated products, petroleum and some heavy metals out of the soil. To do mycoremediation, set up a raised bed garden box and fill it with the compost from the last step. Some people also add fish bones to the compost, which have been said to remediate lead. Wood chips and/or straw are then added to the top of the soil/compost, depending on which mushrooms you are using. Common mushrooms for mycoremediation are oyster mushrooms and winecap mushrooms, spores of which can be bought online from Field & Forest, or you can get some inoculated straw or woodchips from a friend.

Cleaning toxic soil where we’re at with the tools that we have is going to become increasingly important as we face dwindling energy resources and a changing climate. Visionaries and innovators like Nance Klehm in Chicago have been testing different plants and methods for bioremediation. Her amazing booklet The Ground Rules is an excellent resource for anyone looking to learn more.

Ripple ecology is about cultivating a connection with the soil and each other, and how those relationships change us as we go into the world as changed people, who touch people who become changed people themselves. By learning, sharing, and caring deeply for the earth around us, we become humble agents of profound change. How can you start where you’re at with the tools that you have?