new aspects of cellulose acetate biodegradation€¦ · • biodegradation is mostly too slow to...
TRANSCRIPT
New Aspects of Cellulose Acetate
Biodegradation Dirk HÖLTER, Philippe LAPERSONNE
ST 13
09.10.2017
2017
_ST
13_H
ölte
r.pd
fS
SP
T20
17 -
Doc
umen
t not
pee
r-re
view
ed b
y C
OR
ES
TA
Cellulose acetate is biodegradable – or not?
CORESTA SSPT 2017 – ST 13 2
… cellulose acetate, a non-biodegradable plastic …
… non-biodegradable cellulose acetate filters …
Contrary to popular belief, cigarette butts are NOT biodegradable!
C. Curtis et al., Tobacco Control (2016) 0, 1–5
WHO 2017, Tobacco and its environmental impact: an overview
http://www.no-smoke.org
Depending upon the degree of substitution cellulose acetate
can be biodegradable http://opensourceecology.org/wiki/Cellulose_acetate
2017
_ST
13_H
ölte
r.pd
fS
SP
T20
17 -
Doc
umen
t not
pee
r-re
view
ed b
y C
OR
ES
TA
What means “Biodegradable”?
• UN definition (1997)
“matter capable of decomposing rapidly under natural conditions”
• Wikipedia (09/2017)
“is the disintegration of materials by bacteria, fungi, or other biological means”
• IUPAC recommendation (2012)
“Qualifier for a substance or device that undergoes biodegradation (= degradation
caused by enzymatic process resulting from the action of cells)”
CORESTA SSPT 2017 – ST 13 3
There is no universal definition of “biodegradable”
2017
_ST
13_H
ölte
r.pd
fS
SP
T20
17 -
Doc
umen
t not
pee
r-re
view
ed b
y C
OR
ES
TA
Almost common sense:
biodegradation has to result in CO2 (CH4), H2O and biomass (+ N2 and salts)
but what’s about:
• environmental conditions
• indicator for biodegradation
• the form of the tested samples
• passing criteria for biodegradability
CORESTA SSPT 2017 – ST 13 4
No evaluation of biodegradability without defined frame conditions
→ standardized test conditions
defined in standards or
certification schemes
2017
_ST
13_H
ölte
r.pd
fS
SP
T20
17 -
Doc
umen
t not
pee
r-re
view
ed b
y C
OR
ES
TA
CORESTA SSPT 2017 – ST 13 5
General Process (simplified):
1. microbes (bacterias and fungi) colonize the surface of the
material → biofilm formation1
2. enzymes from the microbes attack the material
3. material is transformed into CO2 (anaerob also CH4), water and
biomass (+ N2 and salts)
→ the process can be supported by abiotic degradation2, e.g.
photo degradation or hydrolysis
How does biodegradation of a polymer material work?
1H.-C. Flemming, Polym. Degrad. Stab. (1998) 59, 309-315 2N. Lucas, Chemosphere (2008) 19, 429-442
2017
_ST
13_H
ölte
r.pd
fS
SP
T20
17 -
Doc
umen
t not
pee
r-re
view
ed b
y C
OR
ES
TA
CORESTA SSPT 2017 – ST 13 6
Biofilm formation, „deacetylating“ microbes are rate determing
Synergistic degradation including deactylation and cellulose breakdown
Cellulose acetate with degree of substitution (DS) ~ 2.5
Cellulose
Cellulose
Acetate
The special thing about cellulose acetate
2017
_ST
13_H
ölte
r.pd
fS
SP
T20
17 -
Doc
umen
t not
pee
r-re
view
ed b
y C
OR
ES
TA
CORESTA SSPT 2017 – ST 13 7
External Parameters influencing biodegradation performance:
• general kind of environment (soil, water, compost …)
• present microbes and their numbers
• local conditions like humidity, temperature, pH, nutrients …
What are enviromental conditions?
2017
_ST
13_H
ölte
r.pd
fS
SP
T20
17 -
Doc
umen
t not
pee
r-re
view
ed b
y C
OR
ES
TA
CORESTA SSPT 2017 – ST 13 8
Degradation tests on the following slides
• were performed with Cellulose Acetate having a DS of ~2.5 like it is used
for filter tow production
• the tests were made on our behalf by the internationally acknowledged lab
OWS (Organic Waste Systems, Belgium)
Biodegradation tests
2017
_ST
13_H
ölte
r.pd
fS
SP
T20
17 -
Doc
umen
t not
pee
r-re
view
ed b
y C
OR
ES
TA
CORESTA SSPT 2017 – ST 13 9
Cellulose acetate filter rods degrade very well under anaerobic conditions, even within the average retention time of an anaerobic digester of a biogasification plant
according to ISO 15985/ ASTM D.5511-12
at mesophilic conditions (37 +/- 2 °C)
(indicator: biogas release – CO2/CH4)
biogas plant landfill
Biodegradation in anaerobic conditions
Cellulose (powder)
Smoked
cigarette butts
Cellulose Acetate filter rods
2017
_ST
13_H
ölte
r.pd
fS
SP
T20
17 -
Doc
umen
t not
pee
r-re
view
ed b
y C
OR
ES
TA
CORESTA SSPT 2017 – ST 13 10
Biodegradation in Water
Cellulose (powder)
Cellulose Acetate
(milled fibers) Cellulose Acetate
(milled fibers)
Cellulose acetate degrades in water, but shows a high variability even under very same conditions.
according to ISO 14851
(indicator: oxygen consumption)
2017
_ST
13_H
ölte
r.pd
fS
SP
T20
17 -
Doc
umen
t not
pee
r-re
view
ed b
y C
OR
ES
TA
CORESTA SSPT 2017 – ST 13 11
Shorter lag phase and less variation between replicates with pre-exposed water, demonstrates the influence of the microbial composition at beginning of the test (probably more deacetylating microbes present)
Biodegradation with Pre-exposed Water
Cellulose (powder)
Cellulose Acetate
(milled fibres)
according to ISO 14851
(indicator: oxygen consumption)
→ Addition of 4% of water from former degradation test with cellulose acetate
2017
_ST
13_H
ölte
r.pd
fS
SP
T20
17 -
Doc
umen
t not
pee
r-re
view
ed b
y C
OR
ES
TA
CORESTA SSPT 2017 – ST 13 12
Biodegradation in Marine Water
Cellulose (powder)
Cellulose Acetate
(milled fibres)
according to ASTM D.6691
(indicator: oxygen consumption)
Cellulose acetate is degradable in marine water, we found reduced variation between replicates compared to tests in water
2017
_ST
13_H
ölte
r.pd
fS
SP
T20
17 -
Doc
umen
t not
pee
r-re
view
ed b
y C
OR
ES
TA
CORESTA SSPT 2017 – ST 13 13
Biodegradation in Soil
Cellulose (powder)
Cellulose acetate is also biodegradable in soil, can require several years depending on conditions
Cellulose Acetate
(milled fibres)
according to ISO 17556
(indicator: oxygen consumption)
2017
_ST
13_H
ölte
r.pd
fS
SP
T20
17 -
Doc
umen
t not
pee
r-re
view
ed b
y C
OR
ES
TA
• the general compostability under industrial conditions (> 50 °C) was
reported in literature3 and also found in own tests in the past
• usually the cycle time of an industrial composting plant is too short for
full disintegration and degradation of filter tow or filters made thereof
• probably hydrolysis plays a more important role in composting,
compared to other environments
CORESTA SSPT 2017 – ST 13 14
Biodegradation in Industrial Compost
3J. Puls, Steven A. Wilson, Dirk Hölter „Degradation of Cellulose Acetate-Based Materials: A Review“, J. Polym. Environ,
(2001) 19, 152-165
2017
_ST
13_H
ölte
r.pd
fS
SP
T20
17 -
Doc
umen
t not
pee
r-re
view
ed b
y C
OR
ES
TA
• Paper/Viscose
→ consist predominantly of cellulose, readily biodegradable in most environments
• PLA (polylactic acid)
→ at temperatures < 50 °C standard types biodegrade by far slower than cellulose acetate4, degrades better in industrial composting
• Polypropylene
→ extremely slow degradation, can last centuries, seen as non-biodegradable
CORESTA SSPT 2017 – ST 13 15
How does cellulose acetate compared to other materials?
• the biodegradability of cellulose acetate is closer to cellulose than to most other polymer materials including PLA
• but somewhat too slow to receive acknowledged certificates on biodegradability (e.g. from Vinçotte)
4J. J. Kolstad et al., Polym. Degrad. Stab. (2012) 97, 1131-1141
2017
_ST
13_H
ölte
r.pd
fS
SP
T20
17 -
Doc
umen
t not
pee
r-re
view
ed b
y C
OR
ES
TA
16
Different strategies for acceleration have been discussed like
• increase of material surface
• decreasing degree of acetylation
• adding hydrolyzing agents
• adding enzymes or microbes
• adding nutrients microbes
• adding biodegradable softeners
CORESTA SSPT 2017 – ST 13
Can biodegradability be improved?
2017
_ST
13_H
ölte
r.pd
fS
SP
T20
17 -
Doc
umen
t not
pee
r-re
view
ed b
y C
OR
ES
TA
17 CORESTA SSPT 2017 – ST 13
Successful route to accelerated biodegradation?
Test in water Test in marine water
Cellulose Cellulose
Cellulose
acetate
Cellulose
acetate
Cellulose acetate
with additive
Cellulose acetate
with additive
• in own tests significant improvement could be achieved improvement by
incorporation of slightly alkaline metal oxides into the cellulose acetate matrix
• requirements for external certifications could be met
2017
_ST
13_H
ölte
r.pd
fS
SP
T20
17 -
Doc
umen
t not
pee
r-re
view
ed b
y C
OR
ES
TA
Conclusion
• cellulose acetate as it is used in cigarette filters proved to be biodegradable in all microbially active model environments including marine water
• cellulose acetate shows higher variations of test results compared to other materials, probably caused by necessity of biofilm formation of at least two different kind of microbes
• biodegradation is mostly too slow to fulfill requirements of standards or certificates
• biodegradation can be significantly accelerated by incorporation of additives like slightly alkaline metal oxides into the cellulose acetate matrix in order to meet certification/standard requirements
CORESTA SSPT 2017 – ST 13 18
2017
_ST
13_H
ölte
r.pd
fS
SP
T20
17 -
Doc
umen
t not
pee
r-re
view
ed b
y C
OR
ES
TA
www.rhodia-acetow.com
2017
_ST
13_H
ölte
r.pd
fS
SP
T20
17 -
Doc
umen
t not
pee
r-re
view
ed b
y C
OR
ES
TA