Connections: Soil Makers

Sally Brown

Sally Brown
BioCycle December 2013, Vol. 54, No. 12, p. 36

Last week was a busy week. Two things stand out. One was a lunch with Will Allen, founder of Growing Power ( that was sponsored by Seattle Tilth (, a nonprofit that promotes urban agriculture. The second was a conference call sponsored by U.S. EPA on use of amendments to reduce the hazards associated with elevated soil lead. Listening to both, I found myself thinking that they could work as a perfect team. In reality, I am afraid that I was the only link between the two groups. Let me elaborate.

Growing Power started as an urban agriculture movement in Milwaukee, Wisconsin. Will Allen, the founder, is a former professional basketball player who has embraced urban agriculture as a social and economic movement. He has won a McArthur Genius award for his work. In the absence of a food scraps composting program in his native Milwaukee, Mr. Allen started his own. In fact a central tenet of his approach is that you have to build the soil in order to build the agriculture. Growing Power has composting operations at each of its sites, accepting a range of residuals and producing quality compost using vermicomposting.

In a vacuum of municipal programs, Growing Power has in effect become its own municipality. I asked Mr. Allen at the luncheon about the failure of municipalities to officially integrate efforts like his own, to make those ties permanent and efficient for the benefit of both the urban farmers and the city officials. In answering, he described how he is developing food processing and distribution networks both in Milwaukee and in other cities, often at the invitation of local government officials. No mention was made of letting the city do the composting for him or even using city vehicles or bins to gather his feedstocks.

Lead[En] Soils

Mr. Allen also spoke very briefly about how contaminated urban soils are. His level of knowledge on this seemed pretty black and white. Urban soil is bad so Growing Power makes its own. Not quite the nuanced approach that characterized the EPA call and has resulted in governmental paralysis. The call was focused on lead in urban soils where levels are elevated because we used leaded gasoline and paints for many decades. Soils next to busy streets or near the drip lines of older homes are highly likely to have lead well above background levels. There is unanimous agreement within the scientific community that lead is bad and that elevated lead is the number one concern with soils in cities.

There is also unanimous agreement that not all lead is created equal. The level of danger is a function of what form the lead is in. It is sort of like money. You have a much greater chance of spending your money if it is in liquid form also known as cash, and a much smaller chance if it is socked away in investments like your home. For lead this translates into different types of lead minerals, with some being more available like cash (and thus potentially more harmful to humans exposed to them), and others locked up like your investments.

The EPA call was focused on deciding how much of a hazard lead in soil is and how to measure that hazard. A decent amount of research on this topic has shown that soil amendments, including phosphorus and/or compost addition, can decrease the availability of soil lead. However, the work is far from exhaustive. Here’s how the conversation went:

Speaker One: Questions how much of a hazard lead in soil really is. In studies where soil has been replaced, blood lead (the standard indicator of lead exposure) didn’t go down.

Speaker Two: Believes the big solution is adding phosphorus to soil to change the form of the lead. But we don’t really know how well various types of phosphorus work and how much time is needed to wait for it to work. He was in favor of more greenhouse studies.

Speaker Three: Questions the pH of the lab test that is the current standard to measure how hazardous the lead in soil is, or whether using glycine in the test is really good because he thinks the soils are less hazardous than the tests say and a lot more work must be done on this.

Speaker Four: Added an additional note of concern about using compost and how it seems to work but she isn’t sure if organic matter in the compost confuses the test and so maybe we really need more animal feeding studies on this to make sure that the test is OK.

Speaker Five: Thought everyone on the call had already agreed on the test.

Group: Oh no, we are clearly not all agreed on the test.

To be fair, the person from EPA who organized the call has herself written a terrific guide for urban agriculture when there are concerns about soil contamination. You can find the guidance at this link:

While all of us well-intentioned scientists are debating the validity of the test and the need for additional animal feeding studies, the regulatory infrastructure that is waiting for the science to inform their decisions is left in the lurch. In the absence of clear guidance, some cities are trying to excavate urban soils to a depth of 5-feet to make them safe and others are not taking action. And people like Will Allen who are tired of waiting are making their own compost and using that compost on these urban soils to make them fertile again.

Urban agriculture is sprouting in cities across the country and very few of these cities have made the link between these growing programs and the potential to integrate them into the fabric of the municipality. Whether this is a result of concerns about cost, safety, potential for failure or lack of understanding for the demand is not clear. The one example that I know of that has made the connection is the City of Tacoma, Washington. The city’s community garden program is partially subsidized by the solid waste and the wastewater agencies ( communitygardens.html). The garden program includes a gleaning operation that delivered 64,000 pounds of food that would otherwise have been left to rot and landfilled. Instead, while still fresh, it filled people’s bellies.

It also includes automatic free availability of the biosolids-based soil mix for all community gardens. This free giveaway of the soil mix was costly for the city, but as a result, sales of the soil mix broke all records in 2013. And when a new community garden is established, the lab at the wastewater treatment plant tests the soil to see if it is high in lead. If it is, then the gardeners typically plant in raised beds that are filled with the low lead soil mix.

The big takeaway from my busy week is this message to all municipal managers and regulators: this new infrastructure is coming into existence whether or not you act. By becoming a part of it, you have everything to gain and nothing to lose. Think of what a team you could make partnering with these urban growers. Even the Seattle Mariners would tremble in their shoes at the prospect.


Sally Brown — Research Associate Professor at the University of Washington in Seattle — authors this regular column. Email Dr. Brown at

Related Posts Plugin for WordPress, Blogger...

Comments are closed.