Innovations in water quality
Using wood chips from trees decimated by the emerald ash borer, two Iowa companies have partnered to install edge-of-field conservation bioreactors, designed to filter nutrients and benefit Iowa’s water quality.
When the emerald ash borer was discovered on a Mississippi River island in Allamakee County, alarm bells sounded. The pest had spread across the eastern plains, and there was every indication it would continue.
Emerald ash borer became part of the common vernacular, and Iowa homeowners began to count the ash trees in their backyards.
There were many. Prior to the outbreak, there were about 3.1 million urban ash trees and an estimated 52 million ash trees in forests in the state of Iowa, as the tree filled its role as a popular fast-growing shade tree.
Now, millions of ash trees across the Midwest have been killed by the emerald ash borer since 2002. Along with Iowa, it has been found in 24 other states.
Ash trees can be treated, but the more practical solution, especially for cities, is to remove them. The City of Des Moines contracted with Des Moines-based Wright Outdoor Solutions to do the job.
Wright Outdoor Solutions makes several varieties of wood mulch including utility, single processed, double processed, playground and colored mulch.
They were making so much mulch from the ash trees, they found their market saturated.
“We found ourselves removing 900 to 1,100 trees a year,” says Jennifer Anderson, Wright Outdoor Solutions general manager. “That’s a lot of wood. We struggled to find ways to recycle it and keep it out of the landfills that are already full.”
So they partnered with sister company Sustainable Environmental Consultants in Des Moines. Sustainable Environmental Consultants has been active in the Midwest since 2008, serving primarily the agriculture community.
Sustainable Environmental Consultants builds bioreactors, an edge-of-field conservation practice designed to reduce the amount of nitrogen leaving a farm field from surface drainage tile lines.
“The bioreactor is an underground trench filled with woodchips that acts as a food source for denitrifying bacteria,” explains Jennifer Jensen, Sustainable Environmental Consultants manager of sustainable practices and environmental analytics. “That bacteria converts nitrates to nitrogen gas as part of their respiration process in anaerobic conditions.” Studies have shown as much as a 90% removal rate.
Sustainable Environmental Consultants needed wood chips. Wright Outdoor Services had them, and it looked as if they would have a steady supply for some time to come. Anderson estimates they have three to five years of ash tree removal left.
“There are currently 60 active bioreactors in Iowa,” says Jensen. “According to the Iowa Agriculture Water Alliance and Iowa Department of Agriculture and Land Stewardship, around 120,000 bioreactors or saturated buffers are needed to meet the goal of reducing nitrogen runoff by 45%.”
Bioreactors also give a second life to trees like the discarded ash.
“Woodchips in a bioreactor must meet specifications set by the United States Department of Agriculture to ensure they are of quality to perform in functionality and longevity,” says Jensen.
“Chips must be no more than 120 days old to be used in a bioreactor, so a steady supply is needed,” says Anderson. “Once in place, they will last for up to 20 years before needing to be replaced. Chipping and processing drastically reduces the risk of the borer pests surviving in the chip and makes the survival risk very small.”
When old chips are removed, they are spread across the field, adding carbon to the soil.
“Taking something like the ash trees and recycling them are at the heart of our company’s culture and what we do,” says Anderson. “We want to be involved in a sustainable practice. Keeping the tree waste out of landfills and maintaining water quality is always a focus for us.”
“This is such a great opportunity for an Iowa-based company to partner with another Iowa-based company,” adds Jensen. “We get to help reduce landfill use and help farmers with conservation efforts. It’s exciting to see this take off.”
Queck-Matzie is a freelance writer from Greenfield.
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