Compost Uses and Markets
Compost Uses and Markets: Expanding Opportunities
In January 2015, the City of Phoenix Public Works Department established a pilot compost area at the 27thAvenue Transfer Station to divert food scraps collected at City sponsored special events beginning with Super Bowl XLIX and food scraps from sources including Sky Harbor Airport and Phoenix Convention Center. The feedstock also included landscape and parks clippings. In the Summer of 2015, the Public Works Department launched the Parks Turf Compost Study in partnership with the Parks and Recreation Department and the Resource Innovation and Solutions Network which is a program of the Walton Sustainability Solutions Initiatives at Arizona State University (ASU). The objective of the three-year study was to identify the operational, environmental and economic impact of managing multi-purpose turf at city parks using compost compared to traditional parks turf management practices using chemical fertilizer.
Nine City parks were selected based on their use, type of soil, and irrigation method. During the first year, Parks and Recreation developed a process to ensure consistency with each application. During the Fall and Spring compost applications, Public Works produced and delivered the compost from the pilot compost area and ASU conducted the soil sampling and analysis for all of the plots.
The results of this Parks Turf study indicate that compost has a positive effect on the soil,increasing the levels of many macro and micro nutrients at a rate higher than or equivalent to that of fertilizer resulting in a healthier soil profile at the city parks.
Year 1 of this study laid the groundwork to operationalize the compost application process and created a baseline to compare the study plots with the control plots. In Year 2, a model was developed to analyze the costs and benefits of managing the parks turf using compost and determined that the compost process is significantly more costly than fertilizer applications.
Year 3 further evaluated these costs and identified that if the use of compost resulted in a reduction of watering requirements by 18% or higher, the cost saving for the reduced irrigation could cover the additional cost of managing park turf using compost.
Beginning in July 2018, WSSI and the City of Phoenix will expand this study to evaluate the water savings potential of compost applications in city parks. The strategy to quantify the water savings potential of compost treatments is based on three methods:
1) Observations of the treatment effect on soil water and evapotranspiration.
2) Soil water balance modeling in the various treatments and parks.
3) Development of water conservation scenarios using the calibrated model.
This strategy will provide evidence of the capacity of compost treatments to retain soil water and minimize evaporative losses. In addition, a modeling tool will be used to test the impact of alternative compost treatments and/or irrigation scheduling methods.