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[GreenYes] Re: plastic? or wax? coated milk cartons

Thanks for jumping in Glenn,


I want to share a short paper Eco-Cycle wrote a couple years ago and that was debated at a conference Roundtable at the US Composting Council in New Mexico.   The focus is “plastic coated paper composting” and whether or not we should be doing it or not.  Intuitively it seems like “duh” of course not… but, the research does not make it clear what is happening.  Just because you can’t see it in the finished product seems to be good enough for some very large composters in Southern California and elsewhere … but … wait … maybe the pieces of petroplastic are so small that they are actually there and hurting the life in the ground, especially worms?


The bottom line is that more research needs to be done … but who will fund it?




Eric Lombardi


Executive Director

Eco-Cycle Inc


Topic Paper:  “Should We Be Composting Plastic Coated Papers?”

By:  Dan Matsch and Cyndra Dietz, Eco-Cycle Inc. (Boulder, CO.)


Problem Statement:

Eco-Cycle staff has raised concerns about the environmental impact of plastic remnants in compost that could result from the incorporation of plastic-coated paper products (such as cups, plates, milk cartons) into compost systems.  Since disposable products like these are increasingly coated with plastic (usually LDPE or HDPE), (which is not known to biodegrade) instead of wax (which does biodegrade), their inclusion in compost program feedstock could result in the accumulation of small and sometimes microscopic plastic remnants in the soil. This could be particularly problematic after the repeated application of finished compost. Considering the known persistence of plastics in the environment, and the documented mortality rate of a variety of species (due to ingestion and/or entanglement) in terrestrial, marine and freshwater ecosystems, we wanted to know how plastic remnants would affect the smaller organisms that are essential to soil health. We also wanted to know how it would affect adjacent aquatic ecosystems that would receive plastic from soil runoff.


We contacted a variety of experts around the US to help us better understand the physical and biological impacts of plastic remnants in compost when applied to the soil. 


Physical Impacts

·       Most papers used for foodservice items are coated with a non-biodegradable polymer in order to improve moisture or grease resistance. Most of these are HDPE and LDPE coated.  According to Steve Mojo of the Degradable Products Institute, these polymers inhibit the microbes’ ability to break down material and retard the breakdown of the paper itself.


·       Steve Mojo also concludes that these plastic coatings remain in the compost and will not degrade for long periods of time. On a similar note, William Brinton, Ph. D., of Wood End Laboratory, noted that in his research the HD and LD polyethylenes will only break down into smaller pieces and not biodegrade. Research by Natasha Page at the University of Alberta has shown similar results and has demonstrated erosion-movement of plastic fines into surface waters, where they may wreak havoc on aquatic life. 


The authors of the study “Decomposition of coated papers from a quick-service restaurant” (Tappi Journal, Vol. 78, No. 5, by Ian N. Davie, Julien P. Winter, and R. Paul Varoney), found that, “Polyethylene films do not biodegrade under normal outdoor conditions.” They studied “the biodegradation rate of waxed paper, polyethylene-coated paper, and uncoated paper and evaluated under composting conditions and in soil at room temperature.”  They found that  “Petroleum wax degrades readily and serves as a metabolic energy source.” During the study “analysis for residual polyethylene in the polyethylene-coated paper soil degradation samples indicated no degradation of the polyethylene.” The authors also noted that “ the residual plastic film appears to be too thin and fragile to be conventionally screened from the finished compost.” 


·       John Springman, of Ramsey County (MN) Environmental Health, points out that depending on how much plastic is in the finished product and how many times it is applied over many years, enough of the plastics present could build up to cause drainage and other physical characteristics of the soil to change. 


·       According to Steve Mojo, plastic fragments will migrate with water runoff or can be blown with the wind. Jim McNelly, of Renewable Carbon Management LLC, has done composting research that found “pond scum” of micro LDPE pieces. 


Biological Impacts

·       Daniel Dindal, Ph. D., Professor Emeritus of Soil Ecology, the State University of New York (SUNY) College of Environmental Science and Forestry, has done specific research on plastics incorporated into soil and compost.


Dr. Dindal did two studies in 1983 and 1990. Rigid polyethylene and polystyrene solids were ground up to sand size. These were mixed separately with soil and cow manure to the following percentages of plastic by volume: 5%, 30%, 60%, and 90%. Earthworms were added to some of the samples. Normal populations of native soil microbes and other soil invertebrates were present in the soil and manure prior to testing.


At all the percentage levels for plastic, microbial respiration was reduced during the study, which indicates a marked decrease in microbial population levels. This may be due to the decrease in soil moisture. When earthworms were added, the worms ingested the polyethylene particles, many of which then penetrated their gut tissue causing death. The earthworms did not ingest the polystyrene, they fed around it.


 Generalizations from this study (as stated by Dr. Dan Dindal, 2/05):

1.   There is no evidence that microbes are able to decompose polyethylene or polystyrene.

  1. Our two studies show that particulate HDPE and PS cause detrimental effects on soil microbes and soil invertebrates. These soil creatures are responsible for composting and soil organic matter formation and incorporation.
  2. Earthworm populations were depressed or killed in all PE concentrations.
  3. Soil moisture content is negatively correlated to the concentration of plastics in soil   creating a potential stress effect on the soil biota, which could lead to a decrease in microbial populations.
  4. Plastic build-up via repeated applications is a serious possibility that can lead to the marginalization of soil structural characteristics and fertility as we know it. Once the recalcitrant plastic polymers are distributed in soils, we may never be able to reverse the condition affecting the value of farm land.


Additional Studies using fragment and thin sheet polyethylene instead of granulated would be of interest.


Additional opinions: The following offered their professional opinions. However, these experts stressed that they have not done specific research on this subject. Dr. Dindal’s work is the only actual research that we found.


Mike Weintraub, Ph. D., a microbial biologist and research assistant at the University of Colorado-Boulder, thought that there is a potential for plants to absorb hydrocarbons that have leached from plastics present in compost. 


Jeanette Norton, Ph. D., an associate professor of soil microbiology at Utah State University, pointed out that risks for soil toxicity include plasticizers and pigments that are present in plastics and that could migrate into soils.


Patrick Bohlen, Ph. D., Director of Research at MacArthur Agro-Ecology Research Center, Florida, noted that earthworms are highly susceptible to toxins in the soil and are used as indicator species. They would be affected by any compounds leaching from plastics. He also mentioned concern about the build-up of plastics in the soil over time from repeated applications of compost.





-----Original Message-----
GreenYes@no.address [mailto:GreenYes@no.address] On Behalf Of Johnston, Glenn
Sent: Thursday, November 29, 2007 11:44 AM
Christine.McCoy@no.address; Dan De Grassi
Cc: Spence, Bill - MRF;
crra_members@no.address; Jeffrey Smedberg; GreenYes@no.address; Julie Muir; Jewell, Rebecca
Subject: [GreenYes] Re: plastic? or wax? coated milk cartons


Dear All,


Remember that just because a material disintegrates under appropriate conditions such as ISO 16929 and is not visible, it does not mean that the material is biodegradable.  The only true way to determine biodegradation is to run (ASTM D5338 or ISO 14855) Aerobic Degradation of Plastic Materials under composting conditions which measures the CO2 evolution and shows thu carbon balance that the material is actual biodegrade via in situ composting organisms and does not leave small particles behind.


Best Regards,
Glenn Johnston
Director Regulatory Affairs
NatureWorks LLC
15305 Minnetonka Blvd
Minnetonka, MN 55345
Visit for the latest news and product information.
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From: GreenYes@no.address [mailto:GreenYes@no.address] On Behalf Of Christine.McCoy@no.address
Sent: Thursday, November 29, 2007 12:13 PM
To: Dan De Grassi
Cc: Spence, Bill - MRF; crra_members@no.address; Jeffrey Smedberg; GreenYes@no.address; Julie Muir; Jewell, Rebecca
Subject: [GreenYes] plastic? or wax? coated milk cartons

Sorry folks, it was a while ago that AF&PA did the study on compostability of these. You may want to check in directly with them as my source thought they might have more up-to-date information.

Christine McCoy</FONT

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