Compost Use in Post-Construction Stormwater Practices: A Systematic Review & Results from Listening Sessions Insert the year (2022)
The CREF and the University of Minnesota (U of M) embarked on research to better understand the best uses of compost in stormwater bioretention media and identify compost characteristics that are most impactful to the success of these systems. It is critical for manufacturers, specifiers, end users, and regulators to understand these best uses so users can understand what performs well, suppliers can make a high-quality compost product, and designers can specify and receive a product best suited for the application. This will improve bioretention performance and confidence from specifiers and end-users, minimize pollution potential, and ultimately increase acceptance and use of compost in critical green infrastructure stormwater best management practices.

The final report is the culmination of a joint effort between CREF and the U of M and includes a literature review and a virtual listening session. The systematic literature review (Erickson et al. 2022) reviewed and evaluated current published scientific literature on bioretention system performance with and without compost in the soil media to determine differences in effectiveness and performance. Learn more about the project HERE.

Soluble Salts in Compost and Their Effects on Soil 
The goal of this project  was to explore the known knowledge regarding the speciation of the specific salt measured by the electrical conductivity (EC)test. The chemical, physical, and biological conditions of soil and growing media can be substantively improved by the addition of compost. Compost contains many plant essential nutrients (e.g. N, P, and K) and can also be a source of organic matter. However, concerns persist over composts with a high concentration of soluble salts and their effects on soil fertility, plant growth, and yields. Soluble salts refer to soluble ions such as Ca2+, K+, Mg2+, and Na+ in compost and are measured indirectly and cumulatively through electrical conductivity (EC). Specifically, compost salinity is commonly measured using a method referred to as EC5 whereas soils are measured using an ECe. The use of a variety of non-standardized methodologies often make interpreting results between studies difficult. A compost with an EC5 >5 dS m−1 could be the result of high concentrations of Na+ or other ions, which can be detrimental to plants due to their ability to accumulate in plant tissue and interfere with root uptake of water. Thus, reducing soluble salts, specifically Na+ and Cl− in composts is of high importance. Other soluble salts present in compost (e.g. K+ and Ca2+) are mineral nutrients required for plant growth and can aid in reducing soil sodicity. In appropriate proportions, quality compost with a high EC5 mixed with soil or media can enhance plant growth and yields. Composts with a high EC5 are adept at aiding in soil remediation by facilitating soil particle flocculation, helping leach Na+ deeper into the soil profile and raising soil cation exchange capacity in support of increased soil fertility. Labeling composts and developing appropriate application methods could allay concerns associated with composts where EC5 > 5 dS m−1and promote compost use and sustainable farming practices.The paper was published in Compost Science & Utilization (Gondek et al. 2020).

Learn more about this project HERE.
The full paper is available open access, for Free, HERE.

Analysis of Compost Air Emissions Measurement Methods
This literature review evaluates current air quality testing methods to determine their effectiveness and identify possible changes or alternatives to current testing methods that are more cost-effective and will provide suitably accurate data regarding the emissions at a compost facility. This review is currently out for peer review. Learn more about this project HERE.

Before the peer-review paper is available, here is a shorter version you can read on this subject.

Compost Use Applications – A Return on Investment (ROI) 
While organic diversion has increased, market demand for compost has not kept pace; Many compost facilities have growing stockpiles. One reason for this is that it has been difficult to educate the market on the economic benefits of applying compost. The CREF has researched current literature and studies documenting ROI and created individual reports that provide instructions and explain the ROI for very specific compost applications. Learn more about this project and download the free datasheets HERE

Compostable Plastics Literature Review 
Recently, the US Composting Council worked with Nora Goldstein and Craig Coker, with BioCycle Associates, create the Compostable Products Primer exploring the evolving role of compostable products in the marketplace over the past 30 years. It looks at the relationship industrial composting facilities have with the compostable products market and the acceptance of these products at compost facilities. Through the research done for this primer, a compostable plastics literature review was conducted, which CREF is making available. Learn more about the literature review HERE.

Field Sampling of Compost Materials – Watch the sampling videos here!
The Compost Sampling Video Project developed a two-part video series designed to educate composters on how to effectively and accurately take samples from both finished compost and an active heterogeneous stockpile or windrow. A Sampling Reference Guide is being written as an additional educational tool. Sampling Video Page

Compostable Field Testing Program
The CREF and partners have created a ready-to-go field test for certified compostable food packaging. This open-source standardized field test will provide baseline data on composting conditions that impact the disintegration of compostable products and packaging. This allow the CREF to develop tools for composters wanting to understand best practices for processing these feedstocks. Field Testing Page

Learn more about past CREF research projects