Quantifying the environmental and economic impact of municipal biosolids use in dryland wheat in Washington state

Abstract The use of recycled nutrients is critical to reduce the environmental impact of fertilization. It is an integral component of a circular nutrient economy. Here, we look at the impact of municipal biosolids in lieu of conventional fertilization for dryland wheat production in Washington state, evaluating data from a long‐term replicated field trial as well as a full‐scale biosolids use program, using treated solids from over 40% of the state's population. In addition to environmental benefits associated with reduced synthetic fertilizer use, biosolids use has increased yield (14%) and reduced fertilization costs (3.75 × to 10x), improving economic outcomes for participating farmers. Satellite imagery on commercial fields was used to verify the increased yield observed in the replicated plots. Biosolids application has also resulted in significant carbon benefits, sequestering over 1 Mg CO 2 e for each dry Mg biosolids applied. The cost for participating municipalities is comparable to or less than other reuse or disposal options. These results suggest that the use of biosolids for agronomic crops can have economic and carbon benefits in addition to reducing fertilizer use.