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WTD Updates

Where are those trucks going?

By August 31, 2017March 8th, 2018No Comments


If you drive or live along Interstate-90, you’ve probably seen this truck on the road. You have probably wondered what it is carrying, and where it might be going.

Each one of these trucks carries about 31 tons of an endlessly renewable resource that returns valuable nutrients back to the soil. Loop® is a fertilizer-like product recycled from the waste that we send down drains and toilets.

While a small amount of Loop biosolids is turned into a garden product called GroCo compost, most Loop trucks are headed to farms and forests. Farmers and foresters have used Loop for decades to grow healthy crops and trees. Every day of the year, 10-15 trucks travel to approved sites across the region. As long as people in King County use those drains and toilets, we will find beneficial uses for recycled resources.

History of Boulder Park, Inc. and biosolids

In the 1990s, three local farmers banded together to create Boulder Park, Inc. They were looking for an alternative to a common nitrogen fertilizer, anhydrous ammonia. They wanted to use biosolids to amend soils in a dryland farming area that has lost organic matter and topsoil..

These farmers contacted King County to discuss formation of a partnership to acquire biosolids. Fast forward to today: more than 30 agencies send biosolids to Boulder Park, where universities in Washington and Oregon have conducted decades of research. Results consistently show that biosolids are beneficial for crops and the environment.

For more than 40 years, Loop has been used to enrich the soil with essential nutrients that make for lush farms and forests. Rich in organic matter, Loop helps the soil hold water, improves its structure, and creates a healthy environment for good soil microorganisms.


Farmers who use this soil amendment rave about their healthy soils and productive crops.

Dave Ruud, Boulder Park’s Operations Manager, says, “We used to take the manure out of the feed lot and we’d put it out on the field.”

Ruud compares Loop to animal manure. “It’s the exact same thing. Organic material, we’re able to put that out there to build that soil. It’s just a healthier environment to grow wheat.”


Dave Ruud, Operations Manager,  at the Boulder Park Project, where Loop is used to nourish crops like wheat, sunflower, and canola.

 What are the alternatives for biosolids?

Biosolids are regulated by the Washington State Department of Ecology. Ecology mandates that biosolids go to what is called “beneficial use”, recycling this valuable commodity on land. The Washington State Biosolids Management Program is designed to “protect human health and the environment while encouraging beneficial use of biosolids.”

Across the country, three general approaches to biosolids are used: land application like we do in Washington, disposal in landfills, and incineration.

The Department of Ecology does not consider landfill disposal a beneficial use of a resource that can serve as a soil amendment. Landfill disposal is expensive, and not just in dollars. It uses precious land and limited landfill space. Landfills are increasingly turning away organic material that can be recycled, like food waste and biosolids.


Landfills are filling up, and turn away materials that can be recycled.

Some areas burn biosolids. Again, this option is expensive in several ways. Because Loop is almost 80% water, we would need to dry it before burning. The drying process requires facilities and energy.

We would also lose the benefits Loop provides to soil health. Incineration burns the nutrients and organic matter that make biosolids so useful for soils and plants, and leaves an ash that is hard to recycle. For these reasons, Ecology doesn’t consider incineration a “beneficial use”.


What is in the future?

King County’s technology assessment and innovation team closely monitors new technologies. If a new approach meets regulatory requirements and provides benefits, the team can recommend a change to provide value to our customers and ratepayers.

Other organizations also test newer technologies for biosolids processing, usually ona small scale. Pyrolysis, or gasification, is an early stage technology that is still under evaluation. This approach is not currently useful on a scale our region needs. Currently, only two full scale operating plants exist in the world, one of which is closing.

We live in a dense urban area, where a pyrolysis facility would raise environmental and public health concerns and raise questions about potential impacts to air quality and the local community.


To date, our analysis has come to the same conclusions as independent university scientists and regulatory agencies. Using Loop like a fertilizer is the most cost effective, environmentally beneficial, and socially responsible choice for something once considered “waste”.

Those trucks you see on Interstate-90 are hauling recycled material to places where it enriches the soil and restores the land.

Watch this video for more information!