Biodegradation of mulching films

Sedki BEN ALI

Supervisors: Richard Gattin, Nathalie LEBLANC

Research Unity:Agri’terr-Esitpa

International Conference and Exhibition on Biopolymers and Bioplastics August 10-12,2015 San Francisco, USA 

The French Environment and Energy Management Agency (ADEME)

Public agency under the joint authority of the Ministry of Ecology, Sustainable Development and Energy, and the Ministry for Higher Education and Research

Provides expertise and advisory services to businesses, local authorities and communities, government bodies and the public at large, to enable them to establish and consolidate their environmental action.

Helps finance projects, from research to implementation, in the areas of waste management, soil conservation, energy efficiency and renewable energy, air quality and noise abatement.

Agricultural engineering college

500 students1 research unit, AGRI’TERR, made up• 17 researchers • 7 PhD students in 2015 • 4 post-graduate

• 2 topics:

– Interaction plant/soil/micro-organisms (focus on bacteria and fungi: abundance, biodiversity, functions)

– Non-food valorization of agro-resources and by-products to elaborate agro-materials (relation structure, functions, properties of agro-materials) for different applications:

– Packaging, – Building – Car industry– Agriculture (mulching films)

PLAN

Introduction

I-characterization and composition of materials before the biodegradation test II-Biodegradation test of mulching films-Evolution of materials during the test TGA, SEM, IR, NMR…

-Biological Follow up of the biodegradation test Microbial Carbon, DNA extraction

Conclusion

Environmental pressure

Mulching films?introduction

Waste Management

Application of the 2002 Waste Act

Prohibition to bury, burn or to landfill these bulky and dirty films

Legislative pressure

Landfill 59%Waste to Energy 27%Recycling 7%Incineration 7%²

introduction

Biodegradable mulching films, solution?

Ecological cycle

BIONOV®, Biotec…

introduction

Td = 295°C Starch Td = 395°C PBAT

295°C

395°C

Films characterization before the test

TGAIRNMR

18,63%

75%

BIONOV®

Films characterization before the test

TGAIRNMR

14,95%

74,98%

Td = 295°C Starch Td = 395°C PBAT

Biotec

ester function

Aromatic group hydroxyl function

Alkyl group

3400 cm-1

730 cm-1

1580 cm-1

3200 cm-1

1720cm-1

1296 cm-1

Films characterization before the test

TGAIRNMR

Based on the structure of PBAT several functional groups, such as hydroxyl (OH) and carbonyl (CO) groups can be used as tools to study degradation

C6H4

Films characterization before the test

TGAIRNMR

OCOCH2

NMR spectrum of PBAT with aromatic peak at 8.06 ppm, and OCOCH2 (adipate fraction) at 2.29 ppm

Biodegradation test

NaOH solution

Activated inert solid mediumPouzzolan

Mulching film

Biodegradation of mulching films under simulated soil conditions/ ISO17566

Films characterization during the test

SEMTGAIRMineralization

Biotec

BIONOV®

0 day

0 day

77 days 180 days

180 days77 days

Films characterization during the test

BIONOV®

The samples presented less stages of thermal degradation as long as the test progress. The thermal degradation stage related to starch disappear along the test.

T0T1

T2T3

T11

SEMTGAIRMineralization

BIONOV®

18.63%

15%

9.88%

8.12%

7.9%

5.67%

5.35%

5.24%

5.23%

4.37%

4.13%

Films characterization during the test

SEMTGAIRMineralization

Films characterization during the test

Less stages of thermal degradation as long as the test progress.

The thermal degradation stage related to starch disappear along the test

SEMTGAIRMineralization

T0…T11

Biotec

12.77%

14.95%

2.21%

3.5%

3.72%

3.94%

4.70%

4.72%

4.73%

4.88%

4.94%

7.95%

Films characterization during the test

SEMTGAIRMineralization

Biotec

0 month

6 months

Reduction of the carbonyl absorbance

Increase of the hydroxyl absorbance

Films characterization during the test

Terminal alcohol and carboxylic acid groups are produced due to main chain scission from hydrolysis of ester linkages

SEMTGAIRMineralization

BIONOV®

Soil total microbial biomass was determined using the chloroform fumigation extraction method

Biological Follow up of the biodegradation test

Microbial Carbon

DNA extraction

Similar evolutionIncrease untill 63 days

Progressive decrease until the end of the test

Similar DNA evolution for both films Slower biodegradation for Biotec film is

expected.

Biological Follow up of the biodegradation test

Microbial Carbon DNA extraction

*DNA was extracted from 500mg of pouzzolan using FastDNA SPIN Kit for soil and was quantified by fluorimetric measurement of the Hoescht fluorochome

TGASEM Mineralization

Films characterization during the test

Higher mineralization for Bionov comparing to Biotec More starch in the composition of Bionov than in Biotec

Conclusion

The biodegradation of the films is pimarily due to a selective consumption of starch (facilitate the penetration of water inside of the matrix) hydrolysis of ester goups

Terminal alcohol and carboxylic acid groups are produced due to main chain scission from hydrolysis of ester linkages.

The ester groups of amorphous regions of PBAT is more susceptible to hydrolysis than ester roups in crystalline regions.

Mineralization very active at the begining of the test.

In this study we also showed:

No toxic effect was observed of monomers (PBAT) on plants and earthworms.

Identification of responsible microorganisms (fungi) of biodegradation is in progress.

Tkhanks for your attention…