Potential for a hybrid poplar industry using recycled water : an environmental application of the biocycle farm
Townsend, Patricia A.
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In northern Idaho, water quality regulations prevent the discharge of treated wastewater into the Spokane River during summer months when in-stream flow is low. This creates a water surplus challenge for municipal wastewater treatment facilities in the Spokane Valley, such as the Hayden Area Regional Sewer Board (HARSB). In response to this challenge, HARSB established the Re-Use Farm that consists of 246 acres of annual livestock forage crops, such as alfalfa and oats, and 39 acres of poplar trees. Treated wastewater is recycled on the farm and is used to irrigate the crops and poplar trees. Due to permitting issues, these poplars were not irrigated with wastewater. However, HARSB's potential use of poplar and wastewater resources prompted an economic analysis to determine if the Hayden area could support a 31.25 million-gallon-per-year acetic acid biorefinery. Acetic acid is an industrial chemical that is used to make plastic, wood glue, and synthetic fibers and fabrics. A biorefinery would use the cellulosic sugars present in the poplar wood and ferment the sugars to acetic acid or other high-value chemicals. The biorefinery would require a large, reliable supply of feedstock that could be converted to make these bio-products. Dedicated short-rotation poplar plantations, potentially irrigated with recycled wastewater, are proposed as a way to meet future biorefinery feedstock demands. This example of an environmental application of poplar provides proof of concept for the development of a poplar-based feedstock supply chain for a new biorefinery in northern Idaho. This analysis demonstrates the feasibility of a biorefinery in the Hayden area and the potential cost savings to the biorefinery if poplar feedstock was grown with recycled wastewater.