Value of foodservice packaging as feedstock in compost production confirmed by new study

04 Oct 2018 --- Results of a new six-phase study confirmed that compostable foodservice packaging can be effectively used as a feedstock in commercial composting facilities. The testing, funded by the Foodservice Packaging Institute and the Biodegradable Products Institute, showed that foodservice packaging performed as well as wood and other traditional feedstocks.

“While the compostable packaging industry believed that these items had value to composting operations beyond diversion of food waste, there was little data to support this,” says Rhodes Yepsen, Executive Director of BPI. “The goal of this study was to determine the impact a large volume of compostable foodservice items would have on the composting process when compared to traditional compost inputs like yard trimmings, straw, wood shavings and grass.”

The study's six phases included foodservice selection and analysis; feedstock preparation; pre-process sampling and analysis; active composting and monitoring; post-process sampling and analysis; and reporting and peer review. The Compost Manufacturing Alliance conducted operational field tests at two commercial composting facilities. Each test included two control samples using the facilities' standard composting mix and two samples using compostable foodservice packaging in place of the facilities' customary bulking agents and carbon sources.

An independent laboratory tested and analyzed the samples throughout the active composting process using Test Method for the Examination of Composting and Compost procedures, to determine if there was any noticeable effect from the compostable foodservice items. After processing, the finished compost samples were tested for pertinent compost characteristics, including pH, nutrient content, organic matter and moisture content. The report and its findings were then reviewed by industry experts, including CMA members and representatives from the US Composting Council and BioCycle Magazine.

The results of the analyses performed before, during and after active composting provide evidence that compostable foodservice packaging provided the same benefit as traditional feedstocks, and did not affect the balance of carbon to nitrogen ratios, nutrient levels, moisture content, or porosity to feedstocks or finished compost.

“Compostable foodservice packaging did not add or take away any nutrient value from the finished product,” says Susan Thoman with the Compost Manufacturing Alliance. “Given these findings, compost manufacturers may want to consider compostable foodservice packaging as a viable feedstock, particularly in areas where composters may incur significant costs to source carbon-bearing feedstocks due to seasonally-scarce materials.”

“We are encouraged by these results and are pleased to share them with the composting community,” adds Lynn Dyer, President of FPI. “Knowing that compostable foodservice packaging not only helps supply desirable food scraps to composters but can also reduce the number of supplemental feedstocks composters must collect or source is a major benefit.”

The specifics of the six phases of the study are as follows:

• Phase 1: Foodservice Packaging Selection and Analysis. The study design team identified the desired mix of foodservice packaging for inclusion in the study, including product categories, substrates, and the ratios at which they would be mixed. Special attention was paid to ensuring that the proportions of substrates were reflective of real-world operational observations. Each foodservice item type was independently tested for carbon availability to ensure minimum feedstock preparation targets were met.
• Phase 2: Feedstock Preparation. Products were then mixed, ground, and incorporated into test piles and windrows using each site’s normal feedstock preparation protocols. Each test pile or windrow was divided into four sections: two control samples created from the sites’ seasonal recipes and two test samples using compostable foodservice packaging in place of the facilities’ customary bulking agents and carbon sources. The test samples incorporated the FSP mix at rates of 15 and 30 percent respectively. Each sample contained 130 cubic yards of the mixed material or 520 yards for all samples combined at each facility. Both project sites used pile sizes typical of normal processes. ASP bays are 600 yards (the same size as the four collective samples were processed in), and windrow piles can vary between 100 to 1000 yards.
• Phase 3: Pre-process Sampling and Analysis. Samples of all control and test samples were tested by an independent laboratory using Test Method for the Examination of Composting and Compost (TMECC) methods for target parameters including bulk density, moisture, organic carbon, nitrogen and the carbon-to-nitrogen ratio.
• Phase 4: Active Composting and Monitoring. The samples were in active composting for 45 days in ASP and 90 days in windrow per normal facility operations. Both sites extended active processing for an additional 21 days beyond their normal timeframe, with adjusted moisture and temperature profiles, to allow the compostable products to disintegrate further. Throughout the duration of the project, temperature and bulk density monitoring was performed on site. Moisture levels were monitored, with water applied when needed, and windrow turning activities were tracked.
• Phase 5: Post-process Sampling and Analysis. After processing, finished compost samples were tested by an independent soil testing laboratory using TMECC methods for pertinent compost characteristics including pH, nutrient content, organic matter, and moisture content, according to Seal of Testing Approval (STA) standards.
• Phase 6: Reporting and Review. This study report and its findings were reviewed by industry experts including members of the US Composting Council (USCC) and BioCycle Magazine (BioCycle).

The full report is available here.