1 Plastivida Brazil June 10, 2008 Joseph P. Greene, Ph.D. Professor California State University,...

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Plastivida Brazil

June 10, 2008Joseph P. Greene, Ph.D.

Professor California State University, Chico

Chico, CA 95929-0789

Biodegradable and Degradable Plastics Biodegradation Testing in Aerobic Compost and Anaerobic

Environments

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Agenda• Research Objectives• Products Tested• Results

– Compost Environment• Chico Green Yard Waste• Chico In-vessel Manure Waste • Vacaville In-vessel Food Waste• Mariposa County In-vessel Municipal Solid Waste (MSW)• Laboratory ASTM D-6400

– Marine Water Environment– Anaerobic Digestion Environment– Laboratory Quality Tests for Contamination of Recycled

Plastics• Conclusions and Recommendations• Questions

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Objectives of Research• Evaluate

– Performance, degradation rates and environmental impacts of degradable plastic products in commercially operated compost facilities and in simulated marine environments.

• Testing– Bio-degradation

• Compost environment: windrow, in-vessel, and laboratory locations

• Marine environment

• Anaerobic digestion

– Environmental Safety Assessments• Fate and persistence of the by-products and toxicity resulting

from the degradation

– Mechanical and physical properties• Recycled plastics with contamination from degradable plastics

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What does Biodegradable Mean?Can the microorganisms in the disposal system (composting, soil, anaerobic vessel) assimilate/utilize the carbon substrate as food source completely and in a short defined time period?

CO2 + H2O + Cell biomass

Complete

microbial assimilation

Specified time frame.

No residual residues.

Hydrolytic

Polymer chains with susceptible linkages

Enzymatic

OxidativeOligomers & polymer fragments

Environment – soil, compost, waste water plant, marine

Biodegradation: Only if all fragmented residues consumed by microorganisms as a food & energy source

Define time and environment (disposal system)

Reference: Dr. Ramani Narayan, Michigan State University, www.msu.edu/~narayan

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Biodegradable versus Degradable Plastics• Biodegradable Plastics

– Degraded by microorganisms in soil, compost, or marine environments.

– Made from natural materials, e.g.,corn, potato, polylactic acid, sugar cane, microbes, etc.

– Made from petroleum products, e.g. modified or polyesters.– Compostable

• Regulated by ASTM standards- will degrade in compost environment in less than 180-days.

• Does not leave any fragments in residue, does not have any heavy metals or toxins, and will support plant life.

• Degradable plastics– Degraded by sunlight, oxygen, or microbes.

• Oxodegradable, photo-degradable, starch-polyethylene plastics.– Can cause environmental problems.

• Results in small fragments that can pollute compost, landfill, marine.• Does not degrade as fast as compostable plastics, may leave small

fragments in soil, may not have toxic residuals, may not support plant life.

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Definitions• Degradable plastics

– All plastics are degradable, though the mechanism is different.– Oxidation: plastics degrade in oxygen environment. Anti-oxidants are added to

polymers.– UV light: plastics degrade in sunlight. Stabilizers are added to polymers.– Heat: polymers can degrade under high temperatures. Stabilizers are added

• Oxo-Degradable– Pro-degradents are added to increase the rate of oxidation and disintegration of

plastics though NOT biodegradable since microorganisms do not consume them.

• Biodegradable– Plastics degrade from microorganisms that consume material but time frame is

not specified.• Can be biobased or petroleum based. Both can be consumed by microorganisms.

• Compostable (Most complete definition)– Plastics that degrade from microorganisms that consume material in specified

time frame and under specified environmental conditions.• Can be biobased or petroleum based. Both can be consumed by microorganisms.

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Products Tested • Compostable (Certified by Biodegradable Polymers Institute- BPI)

– PLA Cups, forks, spoons, knives, clamshell containers, lids, and straws– Biobag trash bags– Ecoflex Polyester bags– PHA Bags– Husky Eco Guard biodegradable bags– Sugar Cane Bagasse plates, bowls, and containers.

• Oxo-Degradable (NOT certified by Biodegradable Polymers Institute- BPI)– Natural Value Oxo-degradable Ecosafe Trash Bags – Oxo Biodegradable Eco-friendly plastic bag– UV-degradable plastic bags and soda can rings

• Control– LDPE plastic trash bag– Kraft paper– Cellulose filter paper

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Commercial Compost Environment

• Sites– Chico Green Yard Waste– Chico In-vessel Manure Waste – Vacaville In-vessel Food Waste– Mariposa County In-vessel Municipal Solid Waste

• Materials (Purchased at stores or on-line)– Compostable: PLA lids, Biobag trash bags, Ecoflex Polyester bags, PHA Bags,

Husky Eco Guard biodegradable bags, Sugar Cane Bagasse lids.– Oxodegradable: Ecosafe Trash Bags, Eco-friendly plastic bag, UV-degradable

plastic bags – Controls: LDPE plastic trash bag and Kraft paper

• Tests – Monitored visual disintegration and biodegradation of products after 30, 60, 90,

and 180 day test intervals.– Monitored temperature of air and compost, moisture percentage, pH, compost

maturity, and % solids.

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Chico Green Yard Waste Compost Pictures (120 days)

OxobiodegradableCompost pile

PLA Container Biobag bag

Incoming trash

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Chico Green Yard Waste Compost • Results:

– 30 days: (Windrow)• No degradation: Oxo-biodegradable plastic trash bags

• Some degradation: Food waste and PLA cups, forks, spoons, knives, clamshell containers, lids, and straws, Sugar cane plates and lids, and Biobag trash bags.

– 120 days: (Windrow)• No degradation: Oxo-biodegradable plastic trash bags

• More degradation: Small fragments of PLA container and straw, and Biobag trash bags.

• Full degradation: no visible fragments- PLA cups, forks, spoons, knives, and lids; sugar cane lids and plates.

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In-vessel Manure and Food Waste Compost Pictures (120 days)

In-vessel Compost pile

PLA Container Biobag bag

Incoming MSW trashTurning row

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In-vessel Manure and Food Waste Compost• Results

– 30 days (In-vessel)• Some degradation: Food waste and PLA cups, forks, spoons,

knives, clamshell containers, lids, and straws, Sugar cane plates and lids, and Biobag trash bags.

– 120 days: (Windrow)• More degradation: Small fragments of PLA cups and container,

and Biobag trash bags.

• Full degradation: no visible fragments- PLA, forks, spoons, knives, and lids; sugar cane lids and plates.

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NorCal Vacaville In-vessel Compost Pictures

Compost pile after 30 daysIn-vessel composting with polyethylene cover

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NorCal In-vessel Compost Pictures

Oxodegradable plastic bag Oxodegradable plastic bag UV-polyethylene plastic bag

Mirel PHA plastic bagCorn starch plastic bag Ecoflex plastic bag

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PLA lids Sugar can lids

Husky Eco-Guard plastic bag LDPE plastic bags

Kraft paper

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Compost pile after 30 daysBurlap sacks filled with samples

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NorCal Vacaville In-vessel Food Waste Compost

• Results – 30 days (In-vessel) September to October 2006

• Some degradation: Food waste and PLA cups, forks, spoons, knives, clamshell containers, lids, and straws, Sugar cane plates and lids, and Corn starch trash bags.

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NorCal In-vessel Compost Pictures- 30 days



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NorCal Vacaville after 30 days Pictures



Kraft paper

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Vacaville In-vessel Food Waste Compost Pictures (180 days)

In-vessel Compost pile Sugar cane lidsKraft paper

Compost temperature: 140 +/- 5F Moisture: 40-45%

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Vacaville In-vessel Food Waste Compost Pictures (180 days)

Oxodegradable bag UV-degradable LDPE stretch film control

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Vacaville In-vessel Food Waste Compost• Results

– 30 days (In-vessel)

– 60 days: (Windrow)

– 180 days: (Windrow) March 2007• No degradation: Oxo-biodegradable and UV degradable plastic

trash bags; LDPE control.

• Some bio-degradation: Sugar cane lids and Kraft paper control though samples were very wet and fell apart when moved.

• Full degradation: no visible fragments- PHA bag, Ecoflex bag, PLA lids, Biobag trash bags.

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Mariposa County In-vessel MSW Compost Pictures

ECS In-vessel Compost Method Inside chamber with samples

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Mariposa In-vessel Food Waste Compost– Oven Temperature: 60C for 3 days, 50C for 21 days– % Moisture: > 50%

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Mariposa after 42 days Pictures



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Mariposa after 42 days Pictures



Kraft paper

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NorCal Vacaville Windrow Compost

In-vessel Compost pile

Compost temperature: 140 +/- 5F Moisture: 40-45%

Samples moved to windrow compost after 42 days for an additional 150 days

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Mariposa In-vessel Food Waste Compost• Results

– 42 days (In-vessel)• Some degradation: Food waste and PLA cups, forks, spoons,

knives, clamshell containers, lids, and straws, Sugar cane plates and lids, and Biobag trash bags.

– 150 days: (Windrow) Identical to Vacaville result• No degradation: Oxo-biodegradable and UV degradable plastic

trash bags; LDPE control.

• Some bio-degradation: Sugar cane lids and Kraft paper control though samples were very wet and fell apart when moved.

• Full degradation: no visible fragments- PHA bag, Ecoflex bag, PLA lids, Biobag trash bags.

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Mariposa In-vessel (42 days) plus Vacaville Windrow Compost (150 days)

Pictures Note: Same results as Vacaville Compost alone

Oxodegradable bagsKraft paper and sugar cane lids

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Laboratory Biodegradation Compost• Materials

– Kraft paper, Cellulose filter paper and low density polyethylene controls– Oxo-biodegradable: Ecosafe and Eco-friendly plastic trash bags– Compostable biodegradable products, i.e., PLA straws, Biobag trash bags, PHA

bags, Ecoflex bags– Biodegradable: Stalk Market sugarcane lids.

• Method (Per ASTM D-5338)– Redesigned of laboratory procedure with

• Improve the accuracy of CO2 measurement with LabView data acquisition system and computer control.

• CO2 scrubber, 50 psi pressure canister to supply moist air.

– 45-day test interval• Tests

– Monitored carbon dioxide and oxygen levels for 45-days.– Phytoxicity tests with tomato seeds.– Regulated metals testing for Cd, Pb, and Co.

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Testing Methods• Laboratory Environment

– ASTM 5338 Standards

Sampling process schematic.

Wet air void of CO2

Computer

CO2 or O2 Detector

Biogas

42 Jars at 50C for 45 days

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Laboratory Biodegradation Compost Pictures

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45-day Degradation Results

Material Biodegradation Conversion %

Degradation rate g/day

Results

Cellulose positive control 71.99 0.016 Pass

Kraft paper positive control 61.91 0.014

Pass

PHA bag 64.03 0.014 Pass

PLA straws 61.22 0.014 Pass

Sugar cane plate 61.12 0.014 Pass

Biobag trash bag 60.47 0.013Pass

Ecoflex bag 60.14 0.013 Pass

Blank compost control 1.69 0.000 ----

Polyethylene negative control 1.70 0.000

Fail

Oxodegradable bag 2.19 0.000 Fail

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Plant Growth Results

Material Average Germination %

Average Length, mm after 10-days

Average Germination

Index

Average pH Results

Compost control 46.67 24.33 11.35 8.50 Pass

Cellulose control 43.33 22.67 9.82 8.80 Pass

Avicell cellulose control 83.33 18.33 15.27 8.70

Pass

Kraft paper control 66.67 26.67 17.78 8.40Pass

Polyethylene negative control 70 25 17.50 8.63

Pass

PLA Container 70 20 14.00 8.50 Pass

Sugar Cane lid 70 14 9.80 8.77 Pass

Biobag trash bag 60 32.33 19.40 8.63Pass

PHA bag 63.33 16 10.13 8.83 Pass

Ecoflex bag 56.67 18.33 10.39 8.60 Pass

Oxo-degradable bag 73.33 18.33 13.44 8.80 Pass

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Regulated Metal Testing

Note: Maximum limit of Pb is 30 mg/kg, Cd is 17 mg/kg and Co is not regulated in the US.

Material Average Lead

Concentration Result Average Cd

Concentration Result

Compost 0.02 mg/kg Pass .001 mg/kg Pass

Cellulose 0.02 mg/kg Pass .001 mg/kg Pass

Kraft Paper 0.02 mg/kg Pass .001 mg/kg Pass

Polyethylene 0.02 mg/kg Pass .001 mg/kg Pass

Biobag 0.02 mg/kg Pass .001 mg/kg Pass

PLA straws 0.02 mg/kg Pass .001 mg/kg Pass

Sugar Cane 0.02 mg/kg Pass .001 mg/kg Pass

Ecoflex bag 0.02 mg/kg Pass .001 mg/kg Pass

PHA bag 0.02 mg/kg Pass .001 mg/kg Pass

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Anaerobic Digestion at UC Davis• Materials

– Kraft paper and low density polyethylene controls– Oxo-biodegradable: Ecosafe and Eco-friendly plastic trash bags– Biodegradable: Food waste and biodegradable products, i.e., PLA

lids and straws, Biobag trash bags, PHA bags, Ecoflex bags, and Stalk Market sugarcane lids.

• Methods – Per Dr. Zhang’s research from U.C. Davis– Place 1 g of sample in 1-L jar with 0.5L of water waste

and food sludge at 50°C.– Duplicate test with new samples.

• Tests– Monitor biogas production over 30 day period.

• More research is needed.

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Anaerobic Digestion at UC Davis Pictures

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Anaerobic Digestion at UC Davis• Results: Duplicate trial: 45 days

• Conclusions– Digestion occurs and biogas (CO2 and Methane) is generated for first 15 days. – PHA DOES continues to generate biogas and thus digest anaerobically for the next 30 days.– PLA, Ecoflex, oxo-degradable, UV-degradable, and Kraft paper DO NOT generate biogas after 15 days.

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0 5 10 15 20 25 30 35 40 45

Digestion time (days)

Biog

as y

ield

(L)

Bio bag Oxo bag Straws Yellow bag

Clear Eco flex Food waste Cups

PHA

PLA, Ecoflex, Corn starch

Oxo and UV degradable

Food Waste

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Laboratory Marine Testing• Materials

– Kraft paper and low density polyethylene controls– Oxo-biodegradable: Ecosafe and Eco-friendly plastic trash bags– Biodegradable: Biodegradable products, i.e., PLA straws, Biobag trash bags,

PHA bags, Ecoflex bags, and Stalk Market sugarcane lids.

• Methods (Based on ASTM D-6692 standards)– Place 30 mg of sample in jar with 100 ml of ocean water at 30°C.

• Ocean water was retrieved in July 2007 from Big Sur beach in California.• Water was held at 5°C until testing.

• Tests– At 30 days weigh samples after 24 hours of drying in air and then

replace water with fresh 100 ml and place in oven.– At 60 days weigh samples after 24 hours of drying in air and then

add fresh 40 ml and place in oven.– At 90 days weigh samples after 24 hours of drying in air.

• More research is needed.

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Laboratory Marine TestingPictures

Experimental Set-up Oxo-degradable 90 days

PHA 30 days PHA 90 days

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Laboratory Marine Testing• Results

– 30 days in water• No degradation: Oxo-biodegradable and UV degradable plastic trash bags;

LDPE control, Kraft paper control; PLA lids; Sugar cane lids; Biobag trash bags; Ecoflex bag, UV degradable soda rings.

• Some degradation: PHA bag- 36% disintegration

– 60 days in water• No degradation: Oxo-biodegradable and UV degradable plastic trash bags;



– 90 days: • No degradation: Oxo-biodegradable and UV degradable plastic trash bags;



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Laboratory Quality Tests for Contamination of Recycled Plastics

• Materials– Recycled PET, HDPE, LDPE – Oxo-biodegradable plastic trash bags– Biodegradable: PLA straws and Biobag trash bags

• Method – Combine LDPE and Biobag bags at 0%, 10% and 20%.– Combine HDPE and PLA at 0%, 5%, and10%.– Heated plastic bags under IR heater and then chopped with

grinder.– Injection molded samples with dry blend of plastic.

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Laboratory Quality Tests for Contamination of Recycled Plastics

• Processing– Injection molding tensile bars with 55 ton Arburg.– Blow molding of bottles with Rocheleau R4 machine.– Blown film with 1” Braybender extruder.

• Testing– Quality

• Melt index, density, moisture %

• Opacity, dart impact

– Mechanical properties• Tensile modulus, elongation, and strength, impact

– Samples were tested in batches of 5.

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Results Contamination of Recycled Plastics • Quality tests

– PLA plastics at concentrations of 5 and 10 wt% • Negatively affected melt index, moisture content of LDPE.• Decreased tensile strength and impact strength of LDPE.

– Corn-starch based plastic bags at concentrations of 10 and 20 wt% • Negatively affected melt index, moisture content of HDPE.• Decreased tensile strength and impact strength of HDPE.

– Oxodegradable plastics at concentrations of 10 and 20 wt% • Negatively affected melt index, moisture content of LDPE.• Decreased tensile strength and impact strength of LDPE.

– More research is needed.

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Results Contamination of Recycled Plastics • Mechanical tests

Material

Tensile strength

Ultimate Elongation

Tensile Modulus

Impact strength

% increase % increase % increase % increase

LDPE- neat -- -- -- --

LDPE 10%oxo 3 23 -10 -2

LDPE 20% oxo 3 29 -14 -2

LDPE 10% biobag -1 12 -14 -4

LDPE 20% biobag -9 -8 -5 -3

HDPE- neat -- -- -- --

HDPE 5% PLA -4 20 4 -31

HDPE 10% PLA -9 100 -17 -38

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Summary of Biodegradation Results

Environment

Compostable Plastics

Oxodegradable Plastics Polyethylene

Meet ASTM D-6400 standards

Compost (with proper moisture, oxygen, and temperature levels)

Yes- 100% biodegradable

in 180 daysNo No

Landfill (with low moisture, oxygen, and temperature levels) No

No No

Marine (with high moisture levels and low oxygen and temperature levels)

No, for most Yes, for PHA No No

Anaerobic Digester(with high moisture levels and low oxygen and temperature levels)

No, for most Yes, for PHA

No No

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Conclusions• Compostable materials degrade under commercial

compost environments. – PLA container, Sugar cane lids, PHA bag, Ecoflex bag, and

Husky Eco-Guard plastic bag completely degraded in commercial• Green yard waste, • In-vessel compost systems, and • Laboratory conditions

• Oxodegradable and UV-degradable plastics do NOT biodegrade in any compost environments.

• Oxodegradable and UV-degradable plastics may fragment into smaller pieces compost environments, but may also create more SEVERE environmental consequences.

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Conclusions• PHA degraded in marine and anaerobic

digestion environments.• Sugar cane degraded in anaerobic

digestion environment and also in marine environment.

• PLA straws, Ecoflex bag, and Biobag did not disintegrate in marine environment and biodegraded slowly in anaerobic digestion environment.

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Conclusions• Biodegradable plastics are a contaminant

to recycled plastics.– PLA and Biobag plastics at concentrations of

10 and 20 wt% can negatively impact melt index, moisture content, tensile and impact properties.

– Contamination of biodegradable plastics can be controlled like other contaminants to recycled plastics.

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Recommendations• The research work will help the expanded use

of compostable plastic materials for selected applications.

• The compostable materials should be certified as compostable by BPI and included in procurement standards.

• The compostable plastic materials should perform well in simple applications, e.g., food service ware, lawn and leaf refuse bags that have dry contents, grocery bags, department store bags, and pet bag products.

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Acknowledgements

• The author would like to thank the following people and organizations who have helped develop this research work: – California Integrated Waste Management Board– Mr. Edgar Rojas (CIWMB) and Mr. Mike Leaon (CIWMB) – Dr. Cindy Daley (CSU, Chico), Dr. Ken Derucher (CSU,

Chico), Dr. Gregory Kallio (CSU, Chico), Dr. Randy Miller (CSU, Chico), and Mr. Peter Natale (CSU, Chico)

– Dr. Fengyn Wang (NorCal Waste Systems), Chris Taylor (NorCal Waste Systems), and Mr. Greg Pryror (Jepson Prairie Organics).

– Mr. Steve Engfer (Mariposa County Waste Management).

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