BIODEGRADATION OF BIO-BASED PLASTICS AND ANAEROBIC DIGESTION OF CAVITATED ...

212 Pages·2013·4.88 MB·English

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BIODEGRADATION OF BIO-BASED PLASTICS AND ANAEROBIC
DIGESTION OF CAVITATED MUNICIPAL SEWAGE SLUDGE

DISSERTATION

Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy
in the Graduate School of The Ohio State University

By
Eddie Francisco Gómez Barrantes, M.Sc.
Graduate Program in Food, Agricultural and Biological Engineering

The Ohio State University
2013

Dissertation Committee:
Dr. Frederick C. Michel Jr., Co-Advisor
Dr. Yebo Li
Dr. Jay Franklin Martin, Co-Advisor
Copyrighted by
Eddie Francisco Gómez Barrantes
2013
Abstract
Two areas that represent major challenges and opportunities for petroleum-based
substitutes include production of plastics and energy sources. Recently, significant
progress has been made in developing plastics made from renewable biomass feedstocks.
However, studies on the potential products of naturally occurring degradation processes
and their interaction with the environment have not been performed. In terms of
production of renewable energy sources from biomass, anaerobic digestion (AD) is an
important component in modern wastewater treatment plants because it can transform
part of the organic material into biogas. However, biogas production maximization and
conversion of recalcitrant and depleted sludge remain major limitations. Two studies on
the biodegradability of bio-based plastics under different conditions and one of anaerobic
digestion of cavitated sewage sludge were conducted to address these gaps of knowledge.
In the first study, the relative biodegradability of a wide range of commercially available
plastic alternative materials were determined during composting, AD and soil incubation.
In the second study, the relative biodegradability and structural changes of polyurethane
foams (PUs) made from petroleum and bio-based polyols were compared under the three
conditions aforementioned. In the third study, the ability of hydrodynamic cavitation to
reduce the particle size of sewage sludge obtained from three different full-scale
wastewater treatment facilities in Ohio, US were evaluated. Biomethanation studies were
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also conducted to evaluate process stability and performance in mesophilic anaerobic
digesters treating cavitated sludge. The first study demonstrated that although certain bio-
based plastics and natural fibers were biodegraded to an appreciable extent in the three
environments, only a polyhydroxyalkanoate-based resin biodegraded to significant
extents during the time scale of composting and anaerobic digestion processes used for
solid waste management. Moreover, no significant degradation was observed for
polyethylene or polypropylene plastics or the same plastics amended with additives that
are claimed to facilitate biodegradability. The second study showed that overall, PUs
degraded very slowly or not at all in composting, AD and soil environments. However,
PUs made from bio-based polyols did show evidence of limited biodegradation during
soil incubation. Thermogravimetric Analysis (TGA), Evolved Gas Analysis Mass
Spectrometry (EGA-MS) and Fourier Transform Infrared Spectroscopy (FT-IR) analysis
conducted on the PUs before and after composting revealed that important structural
changes occurred in the PUs containing at least 50% of bio-based derived polyols.
Further analysis revealed that both urethane and ester-related segments were susceptible
to microbial attack in samples containing at least 50% of bio-based polyols. Moreover,
ester groups in the polyol side of the polymer were the preferred site of attack in PUs
made from 100% bio-based polyols. The third study revealed that hydrodynamic
cavitation produced substantial reductions in the particle size of all the feedstocks studied
that had total solids contents ranging from 0.38% and 3.55%. In contrast, reductions in
particle size were marginal when a feedstock containing 5.21% total solids was processed
at mild cavitation process conditions. Laboratory-scale batch AD conducted with
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feedstocks containing mostly secondary sludge showed that cavitation pretreatment
increased total biogas production and volatile solids reduction by 66.8 and 34.2%,
respectively. However, AD of samples consisting of mostly primary sludge did not result
in significant improvements in biogas production.
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Dedication
To my loving wife Giovana D. Mercali, my parents Eddie Antonio and Marielos, family
and friends.

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Acknowledgments
I would like to thank my academic advisor, Dr. Frederick C. Michel Jr., for his
direction, support and friendship. I am grateful to my doctorate’s Examination
Committee Dr. Jay F. Martin and Dr. Yebo Li. I would like to thank the Ohio State
University Department of Food, Agricultural and Biological Engineering for making
possible this experience.
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Vita
2006................................................................B.Sc. in Agricultural Sciences and Natural
Resources Management, EARTH
University, Costa Rica
2010................................................................M.Sc in Food, Agricultural and Biological
Engineering, The Ohio State University,
U.S.
2010 to present ..............................................Graduate Research Associate, Department
of Food, Agricultural and Biological
Engineering, The Ohio State University,
U.S.

Publications
Gómez, E., Michel, F. C., & Martin, J. (2011). Effects of organic loading rate on reactor
performance and archaeal community structure in mesophilic anaerobic digesters treating
municipal sewage sludge. Waste Management and Research, 29, 11, 1117-1123.
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In press: Gómez, E.F., Michel Jr, F.C. Biodegradability of conventional and bio-based
plastics and natural fiber composites during composting, anaerobic digestion and long-
term soil incubation. Polymer Degradation and Stability (2013),
http://dx.doi.org/10.1016/j.polymdegradstab.2013.09.018

Fields of Study
Major Field: Food, Agricultural, and Biological Engineering

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Table of Contents
Abstract ............................................................................................................................... ii
Dedication ........................................................................................................................... v
Acknowledgments.............................................................................................................. vi
Vita .................................................................................................................................... vii
Publications ....................................................................................................................... vii
Fields of Study ................................................................................................................. viii
Table of Contents ............................................................................................................... ix
List of Tables ................................................................................................................... xiii
List of Figures ................................................................................................................... xv
Chapter 1 - Introduction ...................................................................................................... 1
Chapter 2 - Biodegradability of Conventional and Bio-based Plastics and Natural Fiber
Composites during Composting, Anaerobic Digestion and Long-term Soil Incubation .... 3
Abstract ............................................................................................................................... 3
Introduction ......................................................................................................................... 4
Materials and methods ...................................................................................................... 10
Materials ............................................................................................................ 11
Biodegradation in Soil Incubation ..................................................................... 13
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