Post on 15-Jan-2016
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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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NorCal Vacaville In-vessel Compost Pictures
PLA lids Sugar can lids
Husky Eco-Guard plastic bag LDPE plastic bags
Kraft paper
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NorCal Vacaville In-vessel Compost Pictures
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
Oxodegradable plastic bag Oxodegradable plastic bag UV-polyethylene plastic bag
Mirel PHA plastic bagCorn starch plastic bag Ecoflex plastic bag
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NorCal Vacaville after 30 days Pictures
PLA lids Sugar can lids
Husky Eco-Guard plastic bag LDPE plastic bags
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
Oxodegradable plastic bag Oxodegradable plastic bag UV-polyethylene plastic bag
Mirel PHA plastic bagCorn starch plastic bag Ecoflex plastic bag
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Mariposa after 42 days Pictures
PLA lids Sugar can lids
Husky Eco-Guard plastic bag LDPE plastic bags
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;
LDPE control, Kraft paper control; PLA lids; Sugar cane lids; Biobag trash bags; Ecoflex bag, UV degradable soda rings.
• Some degradation: PHA bag- 60% disintegration
– 90 days: • 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- 70% disintegration
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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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Questions?