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On first consideration, Gordon Behnke looks too happy. Why would the biosolids operations supervisor for the City of Tacoma have a smile on his face and enthusiasm to spare? After all, biosolids are, well, you know, materials that come from our toilets and drains. Wouldn't a workplace dedicated to processing such unglamorous stuff smell bad? And what could you tell your friends about your work? And would they want to shake your hand after finding out?
But enough levity. Behnke is happy because he works in a sewage treatment plant that has largely eliminated objectionable odors. He's happy because he works in cutting-edge chemistry, overseeing processes that convert waste into safe -- and coveted -- garden amendments. And he's happy because part of his work involves growing prize-winning vegetables right on the plant's grounds.
What Behnke does is make and test Tagro products. Tagro is short for Tacoma Grow.
Currently, Tacoma mixes three Tagro products for home gardeners and landscapers. Tagro Mix, the product designed for incorporation into soil, is 50 percent treated biosolids, 25 percent sand and 25 percent sawdust. With a nitrogen analysis of just under 1 percent, the mix functions like a slow-release fertilizer. And while it's nourishing your plants, the stuff improves soil structure.
If you want Tagro Mulch, the city's popular mix of treated biosolids and fir and hemlock sawdust, you'll have to get in line; there currently are 180 people ahead of you. Don't be discouraged, though. A new batch is due in August. Call 253-502-2150 to be put on the list.
The third product is Tagro Potting Soil, a mix of treated biosolids, maple sawdust and aged fir bark. In tests conducted by scientists at WSU-Puyallup, this product stimulated bigger, earlier and more productive plants than a commercial peat-based potting mix and dairy manure products. The success of the potting soil has Behnke thinking about development of a seedling mix.
The biosolids used in Tagro mixes are rated Class A. That means they're pathogen-free. Moreover, the concentrations of heavy metals in the mixes are well below the Environmental Protection Agency's "clean biosolids" maximum limits. Every year Dan Thompson, the head of wastewater management operations for the Tacoma Public Works Department, signs his name to a document certifying that the city's biosolids meet all trace-element limitations and Class A pathogen requirements.
Should you want further assurance, the Environmental Protection Agency, the Washington Department of Ecology and the Tacoma-Pierce County Health Department all give Tagro products their blessings.
To produce biosolids without objectionable odors, Tagro experts have had to be innovative. Their solution is a three-stage process at different temperatures. After a two-day, 160-degree, aerobic decomposition in which pathogens are destroyed, the solids undergo anaerobic digestion at lower temperatures, first at around 130 degrees and later at 90. Different organisms work each stage of the decomposition process. The critters in the final, coolest stage virtually eliminate odors.
Tagro mixes are available at the Central Wastewater Treatment Plant, 2201 Portland Ave., Gate 5. Bring a shovel and your own containers. Delivery can be arranged for an additional charge. Summer hours (April-September) are 8 a.m.-5 p.m. weekdays and 8 a.m.-3 p.m. Saturdays. October through March, the hours are 8 a.m.-3 p.m. on weekdays only. For driving directions and information, contact the Tagro office at 253-502-2150 or go online at www.tagro.com.
You'll be pleasantly surprised at the prices for Tagro products. Tagro Mix sells for $8 a cubic yard for City of Tacoma residents and $10 a cubic yard for non-residents. The potting soil goes for $30 a cubic yard or $5 minimum purchase for 1/6 cubic yard. And the popular Tagro Mulch costs $12* a cubic yard or $5* minimum purchase for 1/2 cubic yard.
Would I use Tagro Potting Soil for plants inside our house? I already have, and it doesn't smell.
Would I use Tagro Mix in my vegetable garden? I've already incorporated it into the soil growing my fall/winter carrots, and I'm not worried about suffering mysterious ailments or turning iridescent.
Would I shake Behnke's hand? Every chance I get. What he and his colleagues are doing is the future of biosolids management in our country.