By Sally Brown, University of Washington
Abstracts of these resources are available in the searchable Information Portal offered to Northwest Biosolids members.
Urban green space, public health, and environmental justice: The challenge of making cities ‘just green enough’
Biochar and biosolids increase tree growth and improve soil quality for urban landscapes
Biosolids-based amendments improve tall fescue establishment and urban soils
Marigold and pepper growth in container substrates made from biosolids composted with carbon-rich organic wastes
Biosolids improve urban soil properties and vegetable production in urban agriculture
It is really important to take a step back from PFAS, superbugs and shampoo by-products and remember why we all work to use biosolids in the first place. Biosolids make plants grow like nobody’s business. This month’s library is devoted to growing plants with biosolids - not the typical wheat and corn, but plants that you find in the city. And what better time for this than August-Hot time, summer in the city.
Even in Seattle, the temperatures are soaring into the low 80s. Go to the garden and sit under the shade of a tree on the green grass. Take in the flowers. Eat some tomatoes, fresh from the vine. All of a sudden that heat isn’t so oppressive. Summer becomes less a time of sticky sweat and more a time of warm, soft air and sunshine. Access to greenspace is a critical component of getting through summer and every other season for city dwellers. Recent studies (article #1) are recognizing the link between exposure to those green areas and public health. Access to parks and other types of green space is considered an environmental justice issue. And it is a double-edged sword- you make the space greener and the real estate values go up, forcing out the people who need the greenspace the most. Some cities have turned to greening non-traditional areas as a way around this paradox. This includes alleys, abandoned lots, and brownfields. Soils in regular urban areas often need help - in these ‘special’ areas likely more so. As we all know, biosolids and composts can provide that help. The rest of the papers in the library go into detail on different plant responses to these amendments. These papers are not in the highest impact factor journals and do not make headlines in the news or get regulators all excited. What they do is provide a simple, straightforward way that you can use your materials to make where you live a nicer place for you and all of your neighbors. Take that to your municipalities - along with a pot of pansies.
The 2nd article in the library presents data from a study where trees were grown in three types of soil; a sand, a silt loam, and a compacted clay. Amendments added to the soil included biosolids, biochar, compost, compost tea (did not specify caffeinated or herbal), wood mulch and NK fertilizer. Apparently, it was the biosolids that had the caffeine. Trees grew bigger in this treatment than any of the others with those in the biochar coming in second. If you want trees in the city to grow tall and give you shade, grow them with biosolids.
If you are thinking about a picnic on the lawn, look at the third article. Here scientists grew turf grass on biosolids and biosolids blends with fertilizer as the control. The turfgrass had higher yield and quality with the biosolids amendments. The soil liked it too with higher organic matter, lower bulk density and higher nutrient concentrations. Your average homeowner and potentially Parks employee may not calibrate the application rate like a farmer using Class B material is supposed to, but if they did - apply based on nitrogen, not phosphorus if you want the luscious lawn.
Want to look at flowers while you picnic? Maybe add some peppers to your salad? Turn to article #4. This one is from Craig Cogger and group at WSU. They tested different biosolids based compost and potting soil mixtures as a substitute for traditional horticultural potting mixes. This was done by the book - meaning composts properly made and the study was done as it would be professionally for growing the plants. Again - some of the biosolids mixtures tested were equal to or surpassed the industry standard.
Finally, we turn to article #5 - here is your chance to try your turn at starting your own CSA (Community Supported Agriculture) or urban farm. Researchers out of Virginia Tech mimicked an urban soil by compacting subsoil. Then they amended it with biosolids based products or fertilizer and grew a range of vegetables. As someone whose onion and carrot crops are surrendering from the onslaught of moles and voles, I can assure you that this is not easy work. Anyway- they found that the biosolids based materials, at high loading rates as would be used in a backyard plot, worked well for growing the greens and improved the soil in the process.
So if your biosolids/ compost is looking for a home- look no further than your back yard or back alley. Cities are better for everyone if they have trees, flowers, and grass. The people living in them will be happier and healthier - and likely a little bit cooler. Throw in some vegetables and they’ll be eating better too. You make the tools to make this happen- talk to those environmental justice folks and the parks department and show them your stuff!