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Ramani Narayan, Michigan State University
Tutorial on BIODEGRADABLE PLASTICS
&MATERIALS SCIENCE
Ramani NarayanUniversity Distinguished Professor
If you use any of the slides/materials, please reference authorship and affiliation (Ramani Narayan, Michigan State University) – thank you
Copyright Ramani Narayan
Ramani Narayan, Michigan State University
Using biodegradability as an end-of-life option to remove single use short life disposable plastics/products from the environmental compartment completely and in a safe and efficacious manner via microbial assimilation (microbial food chain)
• Disposal environment (like composting, anaerobic digestor, marine
• Time to complete biodegradation – 90%+ of the carbon substrate should be completely
assimilated by the microorganisms present in the disposal within a short time period (one year or less)
• Degradable, partial biodegradable not acceptable – serious health and environmental consequences
Carbon footprint reduction strategy using bio content
Value proposition for biodegradable plastics/products
2
Ramani Narayan, Michigan State University
TERMINOLOGY
BIOMATERIALS – Biomedical applications Refers to:Any material (metal, plastic, ceramic) implanted in the body -- design and engineering considerations different; biodegradability considerations different
Biodegradability – can be partial with break down products assimilated by the body, and the remaining polymer excreted from the body
ENVIRONMENTAL BIODEGRADABILITY – END-OF-LIFE scenario Biodegradability (Environmental) is a measure of the microbial utilization of (carbon) substrates in the selected environment
• Biodegradability must be Complete – otherwise serious consequences• Biodegradability in a measure, short time period – for composting it is 180
days
Ramani Narayan, Michigan State University
Terminology (Contd)
BIODEGRADABLE (Complete)AND
PETRO/FOSSIL BASEDPLASTICS OR PRODUCTS
BIO (renewable) BASED
OR
BIOMASS BASED
PLASTICS OR PRODUCTS
NOT BIODEGRADABLE
Value proposition --Provides for a reduced
carbon footprint
BIODEGRADABLE (complete)AND
BIOBASEDPLASTICS OR PRODUCTS
BIOPLASTICS
IMPORTANT:Biodegradability MUST be defined/ constrained by:• the disposal system – composting, anaerobic
digestor, soil, marine• Time – 180 days ; max 1 year• Complete utilization of the substrate carbon by
the microorganisms as measured by the evolved CO2 (aerobic) and CO2 + CH4 (anaerobic)
Ramani Narayan, Michigan State University
Carbon footprint reduction strategy using bio contentBiodegradability
5
Using biodegradability as an end-of-life option to completely remove single use short life disposable products from the environmentalcompartment in a safe and efficacious manner via microbial assimilation (microbial food chain)
• Disposal environment (like composting, anaerobic digestor, marine
• Time to complete biodegradation – 90%+ of the carbon substrate should be completely
assimilated by the microorganisms present in the disposal within a short time period (one year or less)
• Degradable, partial biodegradable not acceptable – serious health and environmental consequences
• Specification Standards ASTM D6400, D6868, D7021• Specification Standards EN 13432 (European Norm)• Specification Standards ISO 17088 (International Standard)
Ramani Narayan, Michigan State University
What does Biodegradable Mean?Can the microorganisms in the target disposal system (composting, soil, anaerobic digestor) assimilate/utilize the carbon substrate as food source completely and in a short defined time period?
CO2 + H2O + Cell biomass
Completemicrobial assimilation
defined time frame, no residues
Hydrolytic
Polymer chains with susceptible linkages
EnzymaticOxidative
Oligomers & polymer fragments
Environment – soil, compost, waste water plant, marine
Biodegradation(Step 2): Only if all fragmented residues consumed by microorganisms as a food & energy source as measured by evolved CO2 in defined time and disposal environment
STEP 1
STEP 2
Ramani Narayan, Michigan State University
Carbon footprint reduction strategy using bio contentMeasuring biodegradability
7
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
Glucose/C-bioplastic + 6 O2 6 CO2 + 6 H2O; DG0’ = -686 kcal/molAEROBIC
ANAEROBIC
Glucose/C-bioplastic 2 lactate; ΔG0’ = -47 kcal/mol
CO2 + CH4
CO2 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/bioassimilation
Ramani Narayan, Michigan State University
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 transport3. 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
Carbon footprint reduction strategy using bio contentMeasuring biodegradability
9
0
10
20
30
40
50
60
70
80
90
100
0 20 40 60 80 100 120 140 160 180 200
Time (days)
% C
con
vers
ion
to C
O2
(% b
iode
grad
atio
n)
lagphase
biodegradation phase
plateau phase
biodegradation degree O2
Compost & Test
Materials
CO2
Ramani Narayan, Michigan State University
END OF LIFE OPTIONS
COMPOSTINGFACILITY
COMPOSTINGFACILITY RECYCLING
FACILITYRECYCLING
FACILITY
WASTE TO ENERGY FACILITY
WASTE TO ENERGY FACILITY
BiodegradablePlastics
BiodegradablePlastics
RECYCLED PRODUCTS
LAND APPLICATIONrecycling polymeric carbon
back to soilENERGY
INCINERABLE
Anaerobic digestion facility
Marine environment
Paper-biopolymer composite
Landfill
X
Unless managed for landfill gas recovery for energy
BIOBASED
PLASTICS
Ramani Narayan, Michigan State University
Problems with Degradables – Toxic Chemicals Transport
• 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 --endocrine disruptors
– From Algalita Marine Research Foundation –www.algalita.org/pelagic_plastic.html
• 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, 318-324 – Blight, L.K. & A.E. Burger. 1997. Occurrence of plastic
particles in seabirds from the Eastern North Pacific. Mar. Poll. Bull. 34:323-325
– Phil. Trans. Royal. Soc. (Biology) July 27, 2009; 364
Ramani Narayan, Michigan State University
THE NEED FOR COMPLETE BIODEGRADABILITY !
• Thompson, R.C. et al. 2004. Lost at sea: Where is all the plastic? Science 304, 838, 2004
• Plastic debris around the globe can erode (degrade) away and end up as microscopic granular or fiber-like fragments, and that these fragments have been steadily accumulating in the oceans
• fragments come from several sources, the researchers suggest. These include mechanical erosion of nondegradable plastic bottles and packaging, nondegradable parts of biodegradable plastics, and plastic pieces used as abrasives in cleaning agents.
FLOTSAM Lab experiments show that marine animals consume microscopic bits of plastic, as seen here in the digestive tract of an amphipod. © Science 2004
Ramani Narayan, Michigan State University
Aliphatic-aromatic copolyester
Copolyester
C C
O O
O CH2 O C
O
CH2 C
O
m nx y z
Terephthalic acid Diol Aliphatic diacid
Tm ~ 110 -125 0C
Completely Biodegradable (microbial assimilation) under composting conditions
BASF (ECOFLEX & ECOVIO) Novamont (Eastman Chemcial) DuPontBayer (esteramide)Showa (BIONELLE, chain extension with isocyanate
C-14 label on aromatic ring carbon for monitoring biodegradability
Ramani Narayan, Michigan State University, www.msu.edu/~narayan
R - copolyester
Ramani Narayan, Michigan State University
Cradle to Cradle Concept for Material Design(Integration of Biodegradable Materials with Disposal Infrasructures)
BiodegradableMaterials
BiodegradableMaterials
COMPOSTINGFACILITY
COMPOSTINGFACILITY
LAND APPLICATIONrecycling polymeric carbon
back to soil
TEST METHODASTM D5338; ISO14855 1 & 2 ISO16939 (disintegration)ASTM D6340 C-14 SPECIFICATIONSASTM D6400; EN 13432 ISO 17088ASTM D6868 – paper coatings
Waste water treatment
facility
Waste water treatment
facility
ASTM D5271ISO 14851/14852
Anaerobic digestionbiogas energy plant
ASTM D5511ASTM D5526ISO 15985
Soil Mulch film
Agriculture appl
Soil Mulch film
Agriculture appl
ASTM D 5988
Marine&fresh water
ASTM D 6691,6692D 7021 specification
Ramani Narayan, Michigan State University, www.msu.edu/~narayan
Narayan
Carbon footprint reduction strategy using bio content
16
Biodegradability under composting conditions
• Specification Standards ASTM D6400, D6868, D7021• Specification Standards EN 13432 (European Norm)• Specification Standards ISO 17088 (International Standard)
Biodegradability under marine conditions• Specification Standard D 7021
Biodegradability Test Methods – ASTM Standards• Soil D5988• Anaerobic digestors D 5511, ISO 15985
• 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
Sorting through facts, hypes, claims (misleading)
GREEN WASHING
Ramani Narayan, Michigan State University
MISLEADING BIODEGRADABILITY CLAIMS
Ramani Narayan, Michigan State University
MISLEADING BIODEGRADABILITY CLAIMS
Ramani Narayan, Michigan State University
Green Washing Claims -- Additive Technology• “Plastic products with our additives at 1% levels will fully
biodegrade in 9 months to 5 years wherever they are disposed like composting, or landfills under both aerobic and anaerobic conditions”
The 50% Bio-Batch film did not degrade as completely or as quickly as the cellulose. At the end of the test, 19% of the film had degraded.The results of the aerobic degradation tests indicate that, in time, plastics produced using Bio-Batch pellets will biodegrade in aerobic conditions.DATA DOES NOT SUPPORT THE CONCLUSIONS!
Ramani Narayan, Michigan State University
MISLEADING CLAIMS – UNSUPPORTED BY DATA
Oxo-biodegradable polyethylene (PE) film claims – “The technology is based on a very small amount of prodegradant additive being introduced into the manufacturing process, thereby changing the behavior of the plastic and the rate at which it degrades. The plastic does not just fragment, but is then consumed by bacteria and fungi and therefore continues to degrade to nothing more than carbon dioxide, water and biomass with no toxic or harmful residues to soil, plants or macro-organisms”“Designed to interact with the microorganisms present in landfills, composters, and almost everywhere in nature including oceans, lakes, and forests. These microorganism metabolize the molecular structure of the plastic breaking it down into soil”“Combined with an oxo-biodegradable proprietary application method to produce films for bags. This product, when discarded in soil in the presence of microorganisms, moisture, and oxygen, biodegrades, decomposing into simple materials found in nature. Completely breakdown in a landfill environment in 12-24 months leaving no residue or harmful toxins and have a shelf life of 2 years”In each of the above cases scientific substantiation showing carbon conversion to CO2 using established standard test methods NOT PROVIDED
Ramani Narayan, Michigan State University
“PERF GO GREEN Bags will completely break down in a landfill environment in 12-24 months leaving no residue or harmful toxins and have a shelf life of 2 years.”
Ramani Narayan, Michigan State University
Ramani Narayan, Michigan State University
BIODEGRADABILITY CLAIMS• Chem. Commun., 2002, (23), 2884 - 2885
– 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?
Ramani Narayan, Michigan State University, www.msu.edu/~narayan
Biodegradability Factoids
• An independent study commissioned by the State of California’s Waste Management Board with a California public university showed that the “oxo-biodegradable” bags on the market showed no biodegradation ("Performance Evaluation of Environmentally Degradable Plastic Packaging and Disposable Service Ware," California Integrated Waste Management Board (CIWMB) Publications)
• http://www.ciwmb.ca.gov/Publications/Plastics/43208001.pdf (June 2007).
• This study, and the proliferation of unsubstantiated wild claims on biodegradability forced the State of California to put in place laws:
Ramani Narayan, Michigan State University
GREEN WASHING
NAD (National Advertising Division of the Council of Better Business Bureaus) EXAMINES ADVERTISING FOR GP PLASTICS CORP.‘POLYGREEN’ PLASTIC BAGSNAD Recommends Marketer Modify, Discontinue Certain ‘Green’ Marketing Claims
US Federal procurement requires biodegradability claims to be substantiated by ASTM D6400 specification standard
State of California passed law AB 1972 that no claims of biodegradability should be made unless it meets ASTM D6400 & city of San FranciscoAB 2071 authorize a city, a county, or the state to impose civil liability, in specified amounts, for violations of the above provisions
NAD recommended the following claims be discontinued:• Enviroware is formulated to degrade in months when buried or discarded in a landfill• Enviroware cutlery, straws, hinged containers, plates, bowls and trays are 100%biodegradable and come with a certificate of biodegradability.Federal Trade Commission (FTC) recently brought action against three companies for scientifically unsubstantiated biodegradability claims that their products biodegrade within a reasonably short period of time (landfill
TAKE HOME MESSAGEBiodegradability is an end-of-life option for single use disposable, packaging and consumer plastics that harnesses microbes to completely utilize the carbon substrate and remove it from the environmental -- entering into the microbial food chain.
However, biodegradability must be defined and constrained by:• The disposal system – composting, anaerobic digestor, soil,
marine• Time required for complete microbial utilization in the selected
disposal environment – short defined time frame, and in the case of composting the time frame is defined as 180 days or less
• Complete utilization of the substrate carbon by the microorganisms as measured by the evolved CO2 (aerobic) and CO2 + CH4 (anaerobic) leaving no residues
Degradability, partial biodegradability, or will eventually biodegrade is not an option! – serious health and environmental consequences can occur as documented in literature