Water reclamation facilities across the country periodically assess their existing biosolids management program. When the Western Virginia Water Authority (WVWA) began evaluating its program recently it, like many others, focused on diversifying its program, but it also set an important objective to create an additional revenue stream.
WVWA serves the city of Roanoke, and the counties of Roanoke, Franklin, and Botetourt, and provides sewer services to the city of Salem and the town of Vinton. It has a permitted capacity of 55 million gallons/day. It generates about 10,000 dry tons/year of biosolids, which are beneficially land applied to family farms in the surrounding counties. WVWA has provided treated biosolids to area farms for approximately 30 years.
“The idea was relatively simple – we wanted to create a value to our biosolids,” said Scott Shirley, Director of Wastewater Operations for WVWA. But there were other factors, like ensuring the biosolids program was sustainable while minimizing uncertainties, like landfilling.
“We also wanted to make a sustainable product that could be beneficially used,” he said. The combination of goals took Shirley to Virginia Tech to discuss the potential of converting WVWA’s biosolids into something that could be used by the greenhouse and nursery industry.
A conservative estimate is the nursery industry uses more than 300 million pounds of plastic for horticulture – while serving a commercial and consumer population that values sustainability. Shirley wanted to explore the possibility of creating a planter that was comparable to current products like Peat Pots, a biodegradable container made from a sustainable source.
“The first order of work was to uncover the ‘magic recipe’,” as Shirley described it. In other words, the researchers at Virginia Tech had to figure out how to use WVWA’s biosolids, which are only 5% solids, and then to configure the correct additives with the right amount of biosolids to construct a container.
“That effort alone took several months,” said Peyton Stone, a graduate student when the work on the pots began and now an engineer with Dewberry. Ultimately, the researchers, who included in addition to Stone, Gregory Boardman, Lee Daniels, Greg Evanylo, Kathryn Haering and Joe Marr, created a pot from a mold that was durable, that could handle shipping, plant production, watering and general movement – all essential for a commercial product. The result was two containers with a refined ratio of additives to biosolids. The two “best” pots were made with cellulose and starch, and cardboard.
The next phase, equally important, was testing the product in a greenhouse environment.
“In the end, if the pot that we developed was not able to sustain the growth of a variety of plants, then all the previous work our researchers at Tech did was for nothing,” Shirley said. Greenhouse research proceeded with soybeans, romaine lettuce and cosmos, which is a flowering plant most likely to be grown in a container and also chosen for its appearance.
Production was done in a controlled greenhouse environment and was done compared with commercially available Peat Pots.
“Our objective from the very beginning,” said Stone, “was to make sure there was no adverse impact on the plants.” However, what the researchers learned through testing was that the pots made with biosolids outperformed the Peat Pot product – when dry weight-biomass was measured for soybeans, lettuce, and Cosmos.
“What we learned, and what we became excited about, is that based on the work we did I think, and my fellow researchers believe this as well, is that there’s a real possibility for this to be a commercial product, and it will be exciting to see how work proceeds,” said Stone.
Shirley, who manages the broader biosolids program for WVWA, is pleased with the progressive research done to date, but it remains just that – research. “As an organization, we are firmly committed to continuing to manage our biosolids land application program, but also to look into various ways to diversify our management plan. It’s important that we keep an eye toward our rates, our services and the quality of work, and importantly continue to focus on ensuring that our activities protect the environment and natural resources so important to this area of Virginia.”
He said work will continue on the pots and hopes that someday nursery pots made with biosolids, a safe, sustainable material, will be commonplace in the greenhouse and nursery industry.