Measuring the Biodegradation of Ingeo Compostable Food

Performance of Compostable Food Servicware in a High Solids Digester Followed by Composting

Tim Goodman October 16, 2018

23rd Annual RAM/SWANA Conference & Show

1 Comparison of Composting and Anaerobic Digestion

Anaerobic Digestion Composting Occurs in the absence of oxygen. Occurs in the presence of oxygen. Odors easier to control due to process Odors more difficult to control due to being enclosed. process being outside. Produces methane which can be No emissions which can be harvested harvested as an energy source. as an energy source. Higher capital cost. Lower capital cost. Works well for high nitrogen materials. Requires a balance between nitrogen Cellulosic and carbon based materials and carbon sources. can be difficult to process. Requires 3 – 4 weeks of digestion Takes 12 - 14 weeks of composting and followed by up to 8 weeks of composting curing time to get a mature product. of digestate to produce a mature product. And the bugs are different!

Actinomycetes Fungi Bacteria

Macro & Micro Fauna

Hydrolytic Fermentative Acidogenic Methanogenic Bacteria Bacteria Bacteria Bacteria

© 2014 NatureWorks 4 Assumptions about Compostable Food Serviceware in Anaerobic Digesters • The general assumptions based largely on a variety of lab-scale testing. • Assumptions:  Under mesophilic operating temperatures, no change will be observed in the products.  Under thermophilic operating temperatures, some change in the products will be noticed (deformation, color-change, brittleness).  If the solid digestate is further processed using aerated composting methods, products will complete the biodegradation and disintegration process.  Wet digesters not as effective in processing compostable products. o Most pre-screen feedstock before grinding, pumping & mixing. o Typically send whatever gets screened out to landfill as opposed to a composting step.

Project Participants • NatureWorks • BIOFerm™ Energy Systems • University of Wisconsin – Oshkosh

Project Objectives • Determine the behavior of Ingeo PLA compostable food serviceware in a commercial scale, dry anaerobic digester operated under mesophilic temperatures (25 – 450 C or 77 – 1130 F).

• Determine the behavior of the digested items in a simulated commercial composting environment.

• Year of Construction: 2011 (first commercial-scale, dry fermentation AD facility in North America) • Owner: UW – Oshkosh Foundation • Developer: BIOFerm™ Energy Systems • Feedstocks: 10,000 TPY of food waste, yard waste, animal bedding and curbside organics • Energy Production: 370 kW of continuous electrical power

Overhead nozzles spray Electricity a microorganism-rich Gas Generator solution to optimize the Heat process.

Fermentation Chamber In-floor heating system running at a mesophilic temp of1040 F. (400 C). Percolate Organics Tank Heat Solid Digestate to Percolate Recirculation Aerobic Composting Organics are loaded into fermentation Solid digestate to chambers and processed for 28 days. composting site for further processing.

• Based on the typical makeup of the incoming feedstock a recipe was developed for the test samples. o Fresh material – 45% (yard waste, food waste, structural material) o Recycled digestate – 45% o Compostable Food Serviceware (CFS) – 10% (compostable cups, utensils/dinnerware, coffee/tea bags, compostable liner bags) • This mix of materials was put in nine (9) nylon mesh bags durable enough for the digestion process while still allowing liquids (percolate) to flow through freely.

• Approximately 50 lbs. of this mix was put in each bag.

• The bags were placed into one of the fermentation chambers along with that day’s load of organic materials and was then covered with a layer of biomass to encourage heat and mass transfer. • The chamber was then closed and left to cook for 28 days. • Percolate is added on a regular schedule and temperatures in both the chamber and the nylon mesh bags were monitored.

• After 28 days, the chamber was opened and all material was unloaded. • The nylon mesh bags were intact and the digested material was removed from each bag. • Samples of the compostable plastics were collected for laboratory analysis to determine the amount of biodegradation.

• Two trial compost bunkers – designed to simulate standard commercial windrow systems and operate under thermophilic compost conditions o Windrow A – Digestate, yard waste (50/50) and digested CFS o Windrow B – Digestate, yard waste (50/50) and fresh CFS (weighed, separated and crushed)

• Of the approximately 45 lbs. of CFS placed in each windrow, 40 lbs. were placed in loose and 5 lbs. placed in a nylon mesh bag and buried in the piles.

• Piles turned semi-weekly; temperatures checked and recorded before each turning. • Samples of CFS were taken from each pile for laboratory analysis over the 8 week duration of the compost trial.

South Pile North Pile AD Pre-Treated Non-AD Treated

• The first stage of PLA degradation is usually the reduction of molecular weight (Mw) by hydrolysis.

• Fragments of lactic acid are products of the hydrolysis process with microorganisms to produce carbon dioxide, water and solid biomass.

• Though moderately stable under mesophilic temperatures, PLA hydrolysis can be accelerated under thermophilic temperatures (above 500C).

• The Mw for a variety of products (clear cups, hot cups, hot cup lids, cutlery, etc.) were used as a baseline with samples drawn after 28 days in the digester and again over an 8 week period from the simulated composting piles.

• Mw testing was used to compare: o Pre-processing samples o Post-AD samples o Post-AD + composting samples o Post composting samples

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Molecular Molecular Weight Anaerobic Aerobic 30000 Digestion Composting

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Clear Cup in Compost Only Clear Cup in AD then Compost

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Lid in AD then Compost Lid in Compost Only

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Anaerobic Aerated Digestion Composting 35,000

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Cutlery in AD Followed by Composting Cutlery in Composting Only

• General characteristics of the AD digestate coming out of the fermentation chamber included: o Whole, recognizable food waste was not found o Tea bags and coffee bags were not found o Compostable plastics were found to be brittle and deformed o Ingeo PLA-coated paper was broken down o Compostable plastic bags were mostly intact but showed signs of disintegration

• Observations of the compostable products in the composting piles showed: o In as little as 3 weeks, most of the CFS in the AD pre-treated pile had disintegrated beyond detection. Start of Trial o After 6 weeks, very little (< 5%) CFS remained visible in either pile.

o The most commonly found compostable items found in the piles at the end of the trial were hot cup lids and parts of clear cold cups.

End of Trial

• Dry Anaerobic Digestion (Mesophilic Temperatures) o Noticeable change in the visual characteristics of the compostable products. o Total breakdown of PLA-coated paper and tea/coffee bags. o Compostable plastic cold cups and cutlery were recognizable and generally intact but deformed into a “melted” appearance. o Mw testing of the compostable products after 28 days in the digester confirms a partial breakdown of molecular structure (biodegradation).

• Aerobic Composting (Thermophilic Temperatures) o Most significant disintegration of compostable plastic material observed. o After 4 weeks – Less than 5% of all the AD pre-treated compostable products were detected in Windrow A. o After 6 weeks – Less than 5% of all the fresh compostable products were detected in Windrow B. o Dry fermentation shortens the subsequent aerobic composting by no less than two weeks.