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Photo credit: Eli Brownell, King County Parks

Trees love Loop® biosolids just as much as we love trees.

Here in the Pacific Northwest, Loop is used to build forest soils and to provide nutrients for trees on commercial tree farms in east King County, so they grow faster and more resilient. Healthy forests don’t just help nature, they also help us fight climate change, give us a place to hike and play, and support our local economy.

tree branch

Photo credit: Eli Brownell, King County Parks

Protects our natural environment

Forest sites are managed carefully so that Loop helps the natural ecosystem. Loop is full of carbon-rich organic matter and essential nutrients, which is what makes the soil and trees healthy. Like farmlands where Loop is applied, we want Loop to stay where it can help the forest, which is in the soil, not the water. To keep our wetlands, rivers, and streams pristine, sites are selected based on the type of soil, how steep or flat they are, and how close they are to rivers and streams. Loop is only applied to the most suitable sites, and buffer areas are set up to protect wetlands, rivers, and streams.

Grounded in rigorous science

Studies by the University of Washington and other universities have found that forests enriched with Loop have healthier soil and forest ecosystems, good wood quality, and higher yields. We test water quality in the streams to make sure our waters stay clean—before, during, and after Loop is used. Two decades of monitoring forest streams near biosolids sites have shown no changes to surface water quality from using biosolids.

Applying biosolids in a forest

The amount of Loop used is exactly how much the trees need, called an agronomic rate, which is calculated by the University of Washington. Foresters deliver Loop to the forest using a custom spreader, similar to a manure spreader used on farms.

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For more information about Loop biosolids, please contact us at: