Understanding the Science behind Compostable Plastics & the supporting ASTM standards

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1 Jan 19, Understanding the Science behind Compostable Plastics & the supporting ASTM standards Presentation at the U.S. Composting Council 20 th Annual Conference & Trade Show; Austin TX Ramani Narayan University Distinguished Professor Ramani Narayan, Michigan State University

2 BEGINNING OF PRODUCT LIFE VS END OF PRODUCT LIFE BIOBASED VS BIODEGRADABLE-COMPOSTABLE Organic (carbon based) materials that contain in whole or part biogenic (biological) carbon -- replacing petro/fossil carbon with bio/ renewable carbon beginning of life Offers the value proposition for a reduced carbon footprint ASTM standard D6866 provides a test method to determine the biobased (carbon) content of the product H 2 C PE CH 2 n H 2 C PP CH CH 3 n CH C CH 3 O PLA O n Ramani Narayan, Michigan State University

3 Carbon footprint reduction strategy using bio content END OF PRODUCT LIFE BIODEGRADABILITY-COMPOSTABILITY What happens to product after use when it enters the waste stream Recycling (Collection, buy back/mail back programs) Energy recovery Design for biodegradability (in what disposal environment?) Composting COMPOSTABLE PLASTICS! anaerobic digestion Narayan Landfill gas (CO 2 + CH 4 ) for energy but digestate residue needs to treated by composting Marine soil Misleading and Deceptive biodegradability/compostability claims BEWARE! 3

4 So what is biodegradability? Biodegradability is an end-of-life option that allows one to harness the power of microorganisms present in the selected disposal environment to completely remove biodegradable plastic products from the environmental compartment in a timely, safe, and efficacious manner To claim/use the termbiodegradable, one must define: Disposal environment (composting, anaerobic digestor, soil Time for complete microbial assimilation (biodegradation) Narayan

5 Carbon footprint reduction strategy using bio content Biodegradability A misused and abused term QUESTION Can microorganisms present in the disposal (composting) environment utilize/assimilate the plastic carbon substrate the biotic process What extent and in what time frame? Need complete microbial assimilation and removal from the environmental compartment in a short time period otherwise may have environmental and health consequences Degradable, partial biodegradable not acceptable serious health and environmental consequences Phil. Trans. Royal. Soc. (Biology) July 27, 2009; 364 Narayan 5

6 Carbon footprint reduction strategy using bio content Problems with incomplete and partial biodegradation Thompson, R.C. et al Lost at sea: Where is all the plastic? Science 304, 838, 2004 plastic pieces can attract and hold hydrophobic elements like PCB and DDT up to one million times background levels. As a result, floating plastic is like a poison pill From Algalita Marine Research Foundation PCBs, DDE, and nonylphenols (NP) were detected in high concentrations in degraded polypropylene (PP) resin pellets collected from four Japanese coasts. Plastic residues function as a transport medium for toxic chemicals in the marine environment. Takada et al Environ. Sci. Technol. 2001, 35, Blight, L.K. & A.E. Burger Occurrence of plastic particles in seabirds from the Eastern North Pacific. Mar. Poll. Bull. 34: Phil. Trans. Royal. Soc. (Biology) July 27, 2009; 364 Ramani Narayan, Michigan State University 6

COMPOSTING PROCESS Microorganisms Oxygen/Air

.. ORGANIC/PLANT MATERIAL (carbon source)

Biodegradation* HEAT - 686 kcal/mol energy Breakdown

Polymerization Ramani Narayan, Michigan State

7 COMPOSTING PROCESS Microorganisms Oxygen/Air Moisture Nutrients N,P,K,... ORGANIC/PLANT MATERIAL (carbon source) Compostable Plastics /Materials Chemical degradation Biodegradation* HEAT kcal/mol energy Breakdown Products death microbial biomass CO 2 + H O 2 Polymerization Ramani Narayan, Michigan State University HUMUS/ COMPOST * C-substrates utilized by microorganisms for energy to drive its life processes

8 Degradations Lignin OH Microorganisms OH Cellulose microbial metabolism CO 2 Compostable Materials D6400; D amino acids, proteins, polypeptides Polymer Polymer Nucleophilic addition Quinoidal chemistry OH OH OH O OH O R 1 N H oxidative coupling OH O R 1 N H Polymer Polymer Ramani Narayan, Michigan State University, Formation of Humic Substances During Composting

9 Pilot Scale Composting of paper-yard waste C/N Time (days) DH% Ramani Narayan, Michigan State University,

10 Ramani Narayan, Michigan State University,

Changes in temperature (solid line) and populations of mesophilic fungi (broken line) and thermophilic fungi (dotted line) in a wheat straw compost. Based on data in Chang & Hudson, 1967.

11 Changes in temperature (solid line) and populations of mesophilic fungi (broken line) and thermophilic fungi (dotted line) in a wheat straw compost. Based on data in Chang & Hudson, The left axis shows fungal populations (logarithm of colony forming units per gram of compost plated onto agar); the right axis shows temperature in the centre of the compost. Ramani Narayan, Michigan State University,

12 WHAT IS COMPOSTING? Composting is an aerobic, microbial, exothermic decomposition process The production and subsequent insulation of excess metabolic heat in the composting mass rapidly leads to sustained temperatures above 50 0 C, with core temperatures in insulated zones between 60C and 80C. A typical composting process goes through a series of stages, including rapid temperature increase, sustained high temperatures and gradual cooling of the composting mass. Each successive stage in composting is expected to be accompanied by specific populations of microorganisms bacteria, fungi, and actinomycetes Ramani Narayan, Michigan State University,

13 Carbon footprint reduction strategy using bio content Biodegradability/microbial utilization fundamentals Microorganisms extract chemical energy for use in their life processes by the aerobic oxidation of glucose and other utilizable substrates BIODEGRADBLE PLASTICS, food waste, paper, forest residues biological matter AEROBIC Glucose/C-bioplastic + 6 O 2 6 CO2 + 6 H2O; DG 0 = -686 kcal/mol CO 2 is the quantitative measure of the ability of the microrganisms present in the disposal environment to utilize/assimilate the test C-bioplastic, which is the sole C-source available for the microorganisms biodegradation or bioassimilation Ramani Narayan, Michigan State University 13

14 More Biodegradation/Bioassimilation Facts The aerobic oxidation process (a highly specialized cellular phenomenon) requires the participation of three metabolically interrelated processes: 1. Tricarboxylic acid cycle (TCA cycle) 2. Electron transport 3. Oxidative phosphorylation All of the processes take place inside the cell For these processes to occur: The substrates needs to be transported inside the cell Thus, molecular weight, hydrophobic/hydrophilic balance, other molecular and structural features govern transport across cell membrane into the cell for utilization of the C-substrate. Ramani Narayan, Michigan State University

15 Carbon footprint reduction strategy using content Measuring biodegradability % C conversion to CO2 (% biodegradation) lag phase biodegradation degree O 2 biodegradation phase plateau phase CO 2 Compost & Test Materials Time (days) Ramani Narayan, Michigan State University ASTM D5338; ISO 14855; EN

16 Understanding ASTM Standards ASTM develops several types of Standards for the purpose of our discussion we will focus on the main ones: Standard Specification -- these standards specify the requirements to be met and provide a pass/fail criteria Standard Test method this teaches how a test is to be precisely conducted, and how to report the results of the test A test method does not have a pass/fail criteria and the results from a ASTM test method could be positive or negative for example one could have zero percent biodegradation or 20% or 50% or 90% + Stating that a product passes an ASTM test method is misleading and false a test method provides the numerical result of the test which could be zero or 100% Standard Guide -- a compendium of information or series of options that does not recommend a specific course of action Ramani Narayan, Michigan State University

17 Carbon footprint reduction strategy using bio content Biodegradability under composting conditions Specification Standards ASTM D6400, D6868 (coatings) Specification Standards EN (European Norm) Specification Standards ISO (International Standard) Biodegradability under marine conditions Specification Standard D 7021 Biodegradability Test Methods ASTM Standards Soil D5988 Anaerobic digestors D 5511, ISO Biogas energy plant Accelerated landfill D 5526 Guide to testing plastics that degrade in the environment by a combination of oxidation and biodegradation ASTM D 6954 Must provide results from the test methods could be zero or 50 or 100 percent --- generally not provided but claim of complete biodegradability made Ramani Narayan, Michigan State University 17

18 COMPOSTABLE PLASTICS Plastics that will completely biodegrade under composting environment (laboratory scale test method) Completely assimilated/utilized by the microorganisms present in the composting disposal environment Functions as food for the microorganisms present in the compost environment In addition: Disintegrate in real world/large scale compost systems 90% + of material must pass through a 2mm sieve pass ASTM standards for phyto and eco toxicity Pass ASTM standards for regulated metal content ASTM D6400, D6868; ISO 17055, EN Narayan

19 Specification Standard for Compostable Plastic -- ASTM D6400 Microbial Utilization (D5338 test method): Demonstrate microbial utilization as measured by evolved carbon dioxide, 90% + carbon conversion to CO 2 Same rate as natural materials Leaves, paper, grass & food scraps Time days or less; if radiolabeled polymer is used 365 days or less Narayan

20 Specification Standard for Compostable Plastic ASTM D6400 (contd) Disintegration ISO or ISO or under full scale regular industrial composting conditions for disintegration 90% of material should have gone through a 2mm sieve ISO 16929, Plastics Determination of the degree of disintegration of plastic materials under defined composting conditions in a pilot-scale test ISO 20200, Plastics Determination of the degree of disintegration of plastic materials under simulated composting conditions in a laboratoryscale test ASTM STANDARDS UNDER DEVELOPMENT TO SIMULATE REAL WORLD NORTH AMERICA COMPOST PRACTISES Narayan

21 Specification Standard for Compostable Plastic --ASTM D6400 (contd) Safety No phytotoxicity (impacts on plants) using OECD Guide 208 No ecotoxicity Regulated (heavy) metals less than 50% of EPA (USA, Canada) prescribed threshold Narayan

22 Specification Standard ASTM D 6868 Standard Specification for Labeling of End Items that Incorporate Plastics and Polymers as Coatings or Additives with Paper and Other Substrates Designed to be Aerobically Composted in Municipal or Industrial Facilities, This specification covers end items that include plastics or polymers where plastic film/ sheet or polymers are incorporated (either through lamination, extrusion or mixing) to substrates and the entire end item is designed to be composted under aerobic conditions in municipal and industrial composting facilities, where thermophilic temperatures are achieved. Narayan

23 Pilot-Scale Composting of PE-Coated Packaging C packaging materials C inoculum (1752 g) (147 g) INPUT 5% Plastic COMPOST BIOREACTOR C co 2 (1205 g) OUTPUT 34% Plastic C plastic C cellulosic C biomass (234 g) (323 g) (124 g) Ramani Narayan, Michigan State University,

24 MSU COMPOST PILE Sample boxes with biodegradable material Ramani Narayan, Ramani Narayan, Michigan Michigan State University State University

Compost pile Dimensions 6 x 24 x 3 meters (16.4 x 78.7 x 9.8 ft) Temperature 65 C ± 5 C (149 F ± 9 F) Relative Humidity 63 ± 5% ph 8.5 ± 0.5 Height of pile, m 3.0 2.5 2.0 1.5 1.

25 Compost pile Dimensions 6 x 24 x 3 meters (16.4 x 78.7 x 9.8 ft) Temperature 65 C ± 5 C (149 F ± 9 F) Relative Humidity 63 ± 5% ph 8.5 ± 0.5 Height of pile, m Width of pile, m Ramani Narayan, Michigan Michigan State University State University

26 Visual inspection PLA bottles (ambient conditions) Day 0 Day 1 Day 2 Day 4 Day 6 Day 9 Day 15 Day 30 Ramani Narayan, Michigan Michigan State University State University

27 Visual inspection PLA bottles (compost) Day 0 Day 1 Day 2 Day 4 Day 6 Day 9 Day 15 Day 30 Ramani Narayan, Michigan Michigan State University State University

28 COMPOSTABLE PLASTICS MEETING NOSB DEFINITIONS AND REQUIREMENTS Biodegradable plastic products that meet ASTM D6400 (Standard Specification for Compostable Plastics), and ASTM D6868 (Standard Specification for biodegradable plastics used as coatings on paper and other compostable substrates) are required to be: completely consumed (assimilated) by the microbes present in compost. They function as food for the microorganisms providing it with energy to drive their life processes, and thereby promoting the regular composting process. At the end of the compost period there is no biodegradable plastic/product remaining, they are all consumed by the microorganisms in the composting process. Compostable plastics (completely biodegradable plastics under composting conditions) meeting ASTM D6400, D6868 specifications satisfy the feedstock requirements defined by the NOSB, and the compost task force they become part of the microorganisms because they are transported into the microbial cells where they are oxidized to CO2, releasing energy for the microbial life processes. The ASTM Specification Standards require that all of the substrate carbon is consumed by the microorganisms. Ramani Narayan, Michigan State University

29 COMPOSTABLE PLASTICS MEETING NOSB DEFINITIONS AND REQUIREMENTS The biodegradable plastic/product does not exist anymore after the composting process it is all used up as biological fuel by the microorganisms for its life processes. The compost that is generated comes from the plant and other organic matter used in the composting process and will meet the basic fundamental definition and requirements set by the NOSB. ASTM Standards require testing for eco and phyto toxicity, and regulated metals, thereby ensuing meeting the NOSB requirement that compost produced do not contribute to contamination of crops, soil, or water by plant nutrients, pathogenic organisms, heavy metals, or residues of prohibited substances Ramani Narayan, Michigan State University

30 Aliphatic-aromatic copolyester O C O C O O O CH 2 O C CH 2 C m n x y z Terephthalic acid Diol Aliphatic diacid T m ~ C Copolyester Completely Biodegradable (microbial assimilation) under composting conditions C-14 label on aromatic ring carbon for monitoring biodegradability Ramani Narayan, Michigan State University Cooperation with Eastman Chemical

Ramani Narayan, Michigan State University, www.

31 Ramani Narayan, Michigan State University, Aliphatic-aromatic copolyester

32 Sorting through facts, hypes, claims (misleading) GREEN WASHING Narayan

33 Narayan MISLEADING BIODEGRADABILITY CLAIMS

34 Peer Journal Publications 2009 paper by Odeja et al titled Abiotic and Biotic degradation of oxobiodegradable polyethylenes The oxo-biodegradable PE samples that were abiotically degraded in natural and saturated humidity for one year were biodegraded in a mixture of soil:compost:perlite (1:1:2) at 58 0C for three months. The percent biodegradability as measured by evolved CO 2 was 3.61% (abiotic natural humidity) and 5.70% (abiotic saturated humidity). The percent biodegradability for samples weathered for one year in PP envelopes in compost at 58 0 C was 12.4%, and at 25 0 C was 5.4% after three months. CLAIM Oxo-biodegradable PE will completely (100%) in soil, compost, landfill in 9 months to 5 years Similarly PP (polypropylene), PVC (polyvinyl chloride), PET (polyethylene terephthalate) will 100% biodegrade in 9 months to 5 years Narayan

35 BIODEGRADABILITY CLAIMS Chem. Commun., 2002, (23), A hypothesis was developed, and successfully tested, to greatly increase the rates of biodegradation of polyolefins, by anchoring minute quantities of glucose, sucrose or lactose, onto functionalized polystyrene (polystyrene-co-maleic anhydride copolymer) and measuring their rates of biodegradation, which were found to be significantly improved PRESS Sugar turns plastics biodegradable. Bacteria make a meal of sweetened polythene and polystyrene. weight loss of only 2-12%, Only sugar is being assimilated, PE chain intact Is this a genuine example of biodegradable plastic? Narayan

Science behind compostable plastics ASTM standards

January 26, 2011 Science behind compostable plastics ASTM standards Presentation at USCC 19 th Annual conference Ramani Narayan University Distinguished Professor narayan@msu.edu Ramani Narayan, Michigan