2017_ST13_Hölter.pdf
New Aspects of Cellulose Acetate Biodegradation Dirk HÖLTER, Philippe LAPERSONNE ST 13
09.10.2017 SSPT2017 - Document not peer-reviewed by CORESTA Cellulose acetate is biodegradable – or not?
… cellulose acetate, a non-biodegradable plastic … 2017_ST13_Hölter.pdf C. Curtis et al., Tobacco Control (2016) 0, 1–5 … non-biodegradable cellulose acetate filters … WHO 2017, Tobacco and its environmental impact: an overview
Contrary to popular belief, cigarette butts are NOT biodegradable! http://www.no-smoke.org
Depending upon the degree of substitution cellulose acetate can be biodegradable http://opensourceecology.org/wiki/Cellulose_acetate 2 CORESTA SSPT 2017 – ST 13 SSPT2017 - Document not peer-reviewed by CORESTA What means “Biodegradable”? 2017_ST13_Hölter.pdf There is no universal definition of “biodegradable”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)”
3 CORESTA SSPT 2017 – ST 13 SSPT2017 - Document not peer-reviewed by CORESTA No evaluation of biodegradability without defined frame conditions 2017_ST13_Hölter.pdf Almost common sense: biodegradation has to result in CO2 (CH4), H2O and biomass (+ N2 and salts) but what’s about:
• environmental conditions → standardized test conditions • indicator for biodegradation defined in standards or • the form of the tested samples certification schemes • passing criteria for biodegradability
4 CORESTA SSPT 2017 – ST 13 SSPT2017 - Document not peer-reviewed by CORESTA How does biodegradation of a polymer material work? 2017_ST13_Hölter.pdf General Process (simplified):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
1H.-C. Flemming, Polym. Degrad. Stab. (1998) 59, 309-315 2N. Lucas, Chemosphere (2008) 19, 429-442 5 CORESTA SSPT 2017 – ST 13 SSPT2017 - Document not peer-reviewed by CORESTA The special thing about cellulose acetate 2017_ST13_Hölter.pdf
Cellulose
Cellulose Acetate Cellulose acetate with degree of substitution (DS) ~ 2.5
Biofilm formation, Synergistic degradation „deacetylating“ microbes including deactylation and are rate determing cellulose breakdown
6 CORESTA SSPT 2017 – ST 13 SSPT2017 - Document not peer-reviewed by CORESTA What are enviromental conditions? 2017_ST13_Hölter.pdf External Parameters influencing biodegradation performance:
• general kind of environment (soil, water, compost …)
• present microbes and their numbers
• local conditions like humidity, temperature, pH, nutrients …
7 CORESTA SSPT 2017 – ST 13 SSPT2017 - Document not peer-reviewed by CORESTA Biodegradation tests 2017_ST13_Hölter.pdf 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)
8 CORESTA SSPT 2017 – ST 13 SSPT2017 - Document not peer-reviewed by CORESTA Biodegradation in anaerobic conditions
Cellulose (powder) 2017_ST13_Hölter.pdf landfill Cellulose Acetate filter rods biogas plant
Smoked cigarette butts
according to ISO 15985/ ASTM D.5511-12 at mesophilic conditions (37 +/- 2 °C)
(indicator: biogas release – CO2/CH4)
Cellulose acetate filter rods degrade very well under anaerobic conditions, even within the average retention time of an anaerobic digester of a biogasification plant 9 CORESTA SSPT 2017 – ST 13 SSPT2017 - Document not peer-reviewed by CORESTA Biodegradation in Water 2017_ST13_Hölter.pdf Cellulose (powder)
Cellulose Acetate (milled fibers) Cellulose Acetate (milled fibers)
according to ISO 14851 (indicator: oxygen consumption)
Cellulose acetate degrades in water, but shows a high variability even under very same conditions. 10 CORESTA SSPT 2017 – ST 13 SSPT2017 - Document not peer-reviewed by CORESTA Biodegradation with Pre-exposed Water 2017_ST13_Hölter.pdf → Addition of 4% of water from Cellulose (powder) former degradation test with cellulose acetate
Cellulose Acetate (milled fibres)
according to ISO 14851 (indicator: oxygen consumption)
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) 11 CORESTA SSPT 2017 – ST 13 SSPT2017 - Document not peer-reviewed by CORESTA Biodegradation in Marine Water
Cellulose (powder) 2017_ST13_Hölter.pdf
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
12 CORESTA SSPT 2017 – ST 13 SSPT2017 - Document not peer-reviewed by CORESTA Biodegradation in Soil 2017_ST13_Hölter.pdf Cellulose (powder)
Cellulose Acetate (milled fibres)
according to ISO 17556 (indicator: oxygen consumption)
Cellulose acetate is also biodegradable in soil, can require several years depending on conditions
13 CORESTA SSPT 2017 – ST 13 SSPT2017 - Document not peer-reviewed by CORESTA Biodegradation in Industrial Compost 2017_ST13_Hölter.pdf
• 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
3J. Puls, Steven A. Wilson, Dirk Hölter „Degradation of Cellulose Acetate-Based Materials: A Review“, J. Polym. Environ, (2001) 19, 152-165
14 CORESTA SSPT 2017 – ST 13 SSPT2017 - Document not peer-reviewed by CORESTA How does cellulose acetate compared to other materials?
• Paper/Viscose 2017_ST13_Hölter.pdf → 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
• 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 15 CORESTA SSPT 2017 – ST 13 SSPT2017 - Document not peer-reviewed by CORESTA Can biodegradability be improved? 2017_ST13_Hölter.pdf
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
16 CORESTA SSPT 2017 – ST 13 SSPT2017 - Document not peer-reviewed by CORESTA Successful route to accelerated biodegradation? 2017_ST13_Hölter.pdf • 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
Test in water Test in marine water Cellulose Cellulose Cellulose acetate with additive Cellulose acetate with additive Cellulose acetate Cellulose acetate
17 CORESTA SSPT 2017 – ST 13 SSPT2017 - Document not peer-reviewed by CORESTA Conclusion 2017_ST13_Hölter.pdf
• 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
18 CORESTA SSPT 2017 – ST 13 SSPT2017 - Document not peer-reviewed by CORESTA 2017_ST13_Hölter.pdf
www.rhodia-acetow.com SSPT2017 - Document not peer-reviewed by CORESTA