Dissertations / Theses on the topic 'Biodegradable plastics'

Since their inception and invention, plastic materials have taken on an essential role in numerous applications within the lives of human beings for years now. Each year, the global figure for production of plastic is estimated to be more than 100 million tons. The major reason for the existence of such an enormous amount is due to plastics’ supremacy over other materials with their exceptionally useful properties. According to Hong Kong’s Environmental Protection Department, 13,458 tons of waste was disposed in Hong Kong’s landfills per day during 2011. Such an amount is very large in quantity, and it is predicted that the three strategic landfills of Hong Kong will be fully saturated in 2015-16 if the waste generation rate remains similar as present time and business as usual. Plastics made up approximately 19% of the overall composition of Hong Kong’s disposed municipal solid waste in 2011. Plastic material does not degrade efficiently, and since it has only been in production during the most current century, plastic specialists have not been able to conclude the final life span of the material before it completely degrades. Estimates for different plastic polymers range from 20 years to 400 years and above. To solve these increasingly serious environmental issues, the society has raised its demands and directed many researches into biodegradable polymers (i.e., plastics). They have now become more seriously considered as alternative solutions for conventional, non-biodegradable plastics. However, the creation of such biodegradable materials, the efficiency and cost of that creation and the true biodegradability of those materials is under much scrutiny and debate. The purpose of this study was multi-faceted. It primarily focused on (1) the status and production of biodegradable products in Hong Kong and (2) assessment of the general public’s receptiveness towards using such products. This study aimed to evaluate the above two aspects via literature review and interviews of representatives from biodegradable plastics companies in Hong Kong as well as students and general working-class citizens. This element inquired whether the general public would be willing to pay extra money to use biodegradable plastic products, and whether they thought that these products had beneficial effects towards environmental conservation and protection. Also, the general public would be asked their opinion on a duty for biodegradable products and whether they would be adverse to a policy implementation involving such a duty. A large portion of this project’s critically significant data was generated from random, systematic sampling of different people, asking them about the aforementioned monetary scenarios. Results were insightful and informative giving evident trends that represented the public’s attitude towards biodegradable plastics. Overall, the public was positively supportive of biodegradable technology, which is relatively new. Concurrently, extensive literature review was conducted to assess foreign practices and policies regarding biodegradable plastics, as well as the life-cycle of a primary biopolymer called polylactic acid. A concluding recommendation was constructed to envision the future waste management infrastructure in Hong Kong. That infrastructure could build off of the special region’s budding development of incinerators, composting facilities, waste-to-energy facilities, and sorting technologies. Then, to supplement biodegradable polymer production and post-use handling facilities, the Hong Kong SAR Government could implement strong waste management policies to motivate its society to aim for a more sustainable way of life.
published_or_final_version
Environmental Management
Master
Master of Science in Environmental Management

Packaging waste forms a big a part of municipal solid waste and has caused increasing environmental considerations, leading to a strengthening of varied rules aimed toward reducing the amounts generated. Among different materials, a good vary of oil-based polymers is presently employed in packaging applications. These are nearly all non-biodegradable, and a few are troubled to recycle or apply because of being advanced composites having variable levels of contamination. Recently, important progress has been created within the development of biodegradable plastics, for the most part from renewable natural resources, to provide biodegradable materials with similar practicality thereto of oil-based polymers. The enlargement within these bio-based materials has many potential advantages for greenhouse gas balances and different environmental impacts over whole life cycles and in the use of renewable, instead of finite resources. it's supposed that use of biodegradable materials can contribute to sustainability and reduction within the environmental impact related to disposal of oil-based polymers. The diversity of biodegradable materials and their variable properties makes it trouble to create straightforward, generic assessments like biodegradable product are all ‘good’ or petrochemical-based product are all ‘bad’. during this analysis I'm aiming to discuss the benefits of bioplastics and their substitution potential with respect to petroleum-based materials, the production of bioplastics using scratch and environmental impacts of its composting.

Sequencing batch reactor (SBR) systems were used for the development of a system and operating procedures for the high production of polyhydroxyalkanoates (PHAs) by wastewater treatment (activated sludge) bacterial cultures. It was found that unbalanced growth conditions stimulated massive PHA production in activated sludge biomass. Operating conditions had a significant effect on PHA production and the composition of the accumulated copolymer when either laboratory prepared mixtures of organics or a high acetic acid industrial wastewater were used as the organic substrate mixture. Fully aerobic (AE) conditions with nitrogen (N) and phosphorus (P) limitations were the optimum conditions for PHA production when the laboratory prepared mixtures of orgnics were used, while fully AE with the combinations of N, P, and potassium (K) limitations were better for PHA production using a high acetic acid industrial wastewater as the substrate. One nutrient limitation or partial limitation of either N or P as used for commercial production using pure cultures did not promote massive PHA production in activated sludge biomass compared to the combination of nutrient limitations. A maximum cellular PHA accumulation of 70%TSS was obtained under fully AE conditions with multiple alternating periods of growth and N&P limitations. Microaerophilic/aerobic (MAA/AE) or anaerobic/aerobic (AN/AE) cycling promoted less PHA production compared to fully AE conditions. The relative amounts of the PHA copolymers formed, i.e., polyhydroxybutyrate (PHB) and polyhydroxyvalerate (PHV) were different under different operating conditions, even though the types and amounts of volatile fatty acids (VFAs) in the feed were the same. It was determined that high total phosphorus (TP) content inside the bacterial cells had a significant detrimental impact on PHA production by activated sludge biomass. A two-stage bioprocess was a better approach for obtaining activated sludge PHA accumulation because a growth phase was necessary to grow the bacterial population that contains minimal TP before starting the subsequent PHA accumulation phase. Seeding sludge obtained from a conventional fully aerobic wastewater treatment system was more suitable than seed obtained from a biological phosphorus removal (BPR) system because bacterial populations from BPR systems tended to convert organic substrates to intracellular carbohydrate content rather than PHA under nutrient limitation conditions. The molecular weights and melting point temperatures of PHAs produced by the mixed culture of activated sludge biomass were comparable to those obtained from pure cultures and have the potential to be used for commercial applications. The results of this study indicate that activated sludge biomass has considerable potential for PHA production for commercial purposes, and likely could do so utilizing wastewater sources of organics. In particular organic rich, nutrient limited wastewaters have potential for efficient PHA production.
Ph. D.

Els encoixinats plàstics agrícoles són una peça fonamental del sistema agrícola, contribuint a fer front a la demanda d'alimentació de la creixent població mundial. El seu ús incrementa la producció, precocitat i qualitat de les collites, redueix el consum d'aigua i l'aplicació de pesticides i prevé el desenvolupament de males herbes. Els encoixinats són majoritàriament de polietilè (PE), no biodegradables, i encara que s'han de retirar després de la collita, molts fragments romanen en el camp i es van acumulant, disminuint la qualitat del sòl i de les collites. Els encoixinats de plàstic biodegradable (BDM) s'han presentat com una alternativa sostenible que evita aquesta acumulació; després de la collita seran biodegradats pels microorganismes del sòl en el qual s'integren. Tanmateix, això implica l'aportació al sòl dels diversos compostos (polímers i additius) presents en els fragments, dels que a penes s'han estudiat els seus efectes en les plantes conreades i en els organismes del sòl. L'objectiu d'aquesta tesi és avaluar l'efecte que tenen vuit BDM de diferent formulació i els seus components en el microbioma del sòl agrícola i en plantes conreades. Per a això es van triar dues espècies comunament conreades amb encoixinats que estan entre els principals productes hortícoles a nivell mundial, l’enciam (Lactuca sativa L.) i el tomàquet (Lycopersicon esculetum Mill.). Com a control es va incloure un encoixinat de PE. En primer lloc, es va avaluar si els BDM poden alliberar compostos per contacte amb un mitjà aquós abans d'iniciar la seva biodegradació, i si els compostos alliberats poden afectar el desenvolupament de les plantes. Es va trobar que tots els BDM assajats van alliberar una diversitat de compostos, que en diversos casos (Bioplast SP4 i SP6, Mirel i Biofilm) van afectar negativament la germinació, la morfologia de les arrels o el desenvolupament i fisiologia de totes dues espècies, mentre que els altres BDM van causar efectes menors (Ecovio, Mater-Bi) o no significatius (Bioflex). A continuació, es van identificar els compostos alliberats, que van resultar ser diversos, tant components de la seva estructura polimèrica (1,4-butanediol, àcid làctic, àcid tereftàlic, etc.) com a additius (àcids grassos, glicerol, etc.). D'entre els identificats es va quantificar principalment els que anteriorment havien mostrat afectar el desenvolupament de plantes de tomàquet i d'enciam (1,4-butanediol, àcid làctic i àcid adípic). Les concentracions en què es van trobar van resultar ser substancialment menors que les responsables de causar efectes en les plantes, la qual cosa no permet establir una relació directa entre el seu alliberament dels BDM i els efectes que puguin tenir en les plantes. En tercer lloc, es va estudiar l'efecte de l’acumulació de fragments de BDM en el sòl sobre la germinació i desenvolupament de plantes de tomàquet i d'enciam. La presència de fragments de la majoria dels BDM no va afectar la germinació però si va reduir el creixement i el nivell de clorofil•la en tomàquet i especialment en enciam. En general, els efectes identificats van ser consistents amb els dels compostos alliberats dels BDM trobats anteriorment, i els fragments de PE no van causar efectes. En conjunt, els resultats suggereixen que la composició química del BDM té un paper rellevant en la seva interacció amb el sistema radical de les plantes, i que les conseqüències de la presència de fragments de BDM en el sòl es relaciona amb aquesta composició, probablement pel fet que alliberen components, més que a la seva presència física. Finalment, es va estudiar l'impacte de l'acumuació en el sòl de fragments de BDM en l'estructura i funcions de les comunitats microbianes del sòl agrícola. Després de tres mesos d'incubació, aquesta acumulació va tenir un baix impacte en la diversitat i estructura de les comunitats microbianes del sòl. No obstant això, alguns materials van provocar canvis significatius en l'abundància i diversitat de determinats grups bacterians (Mater-Bi), fúngics (paper MIMGreen) i protistes (Ecovio). Encara que l'activitat microbiana total no es va veure alterada, l'activitat quitinasa, implicada en el cicle del nitrogen, va disminuir significativament per la presència tant de BDM com de PE. Els resultats obtinguts en aquesta tesi doctoral aporten nous coneixements sobre els BDM i els seus potencials efectes. Principalment evidencien que els BDM (1) poden alliberar amb facilitat diversos compostos molt abans que s'iniciï la seva biodegradació, (2) que la solució que conté els compostos alliberats, en funció de la seva composició, pot tenir efectes sobre les plantes i (3) que l’acumulació de fragments de BDM en el sòl presenta capacitat d'afectar el desenvolupament de les plantes i de modificar l'abundància i diversitat del microbioma del sòl en funció de la composició del BDM. Tot això, resulta rellevant per al disseny i desenvolupament d'encoixinats plàstics biodegradables que tinguin sota impacte sobre plantes conreades i sobre el medi ambient.
Los acolchados plásticos agrícolas son una pieza fundamental del sistema agrícola, contribuyendo a hacer frente a la demanda de alimentación de la creciente población mundial. Su uso incrementa la producción, precocidad y calidad de las cosechas, reduce el consumo de agua y la aplicación de pesticidas y previene el desarrollo de malas hierbas. Los acolchados son mayoritariamente de polietileno (PE), no biodegradables, y aunque se deben retirar tras la cosecha, muchos fragmentos permanecen en el campo y se van acumulando, disminuyendo la calidad del suelo y de las cosechas. Los acolchados de plástico biodegradable (BDM) se han presentado como una alternativa sostenible que evita este acúmulo; tras la cosecha serán biodegradados por los microorganismos del suelo en el que se integran. Sin embargo, ello implica el aporte al suelo de los diversos compuestos (polímeros y aditivos) presentes en los fragmentos, pero apenas se han estudiado sus efectos en las plantas cultivadas y en los organismos del suelo. El objetivo de esta tesis es evaluar el efecto que tienen ocho BDM de diferente formulación y sus componentes en el microbioma del suelo agrícola y en plantas cultivadas. Para ello se eligieron dos especies comúnmente cultivadas con acolchados que están entre los principales productos hortícolas a nivel mundial, lechuga (Lactuca sativa L.) y tomate (Lycopersicon esculetum Mill.). Como control se incluyó un acolchado de PE. En primer lugar, se evaluó si los BDM pueden liberar compuestos por contacto con un medio acuoso antes de iniciar su biodegradación, y si los compuestos liberados pueden afectar al desarrollo de las plantas. Se encontró que todos los BDM ensayados liberaron una diversidad de compuestos, que en varios casos (Bioplast SP4 y SP6, Mirel y Biofilm) afectaron negativamente a la germinación, la morfología de las raíces o el desarrollo y fisiología de ambas especies, mientras que los de otros BDM causaron efectos menores (Ecovio, Mater-Bi) o no significativos (Bioflex). A continuación, se identificaron los compuestos liberados, que resultaron ser diversos, tanto componentes de su estructura polimérica (1,4-butanediol, ácido láctico, ácido tereftálico, etc.) como aditivos (ácidos grasos, glicerol, etc.). De entre los identificados se cuantificó principalmente los que anteriormente habían mostrado afectar al desarrollo de plantas de tomate y de lechuga (1,4-butanediol, ácido láctico y ácido adípico). Las concentraciones en que se encontraron resultaron ser sustancialmente menores que las responsables de causar efectos en las plantas, lo que no permite establecer una relación directa entre su liberación de los BDM y los efectos que puedan tener en las plantas. En tercer lugar, se estudió el efecto del acúmulo de fragmentos de BDM en el suelo sobre la germinación y desarrollo de plantas de tomate y de lechuga. La presencia de fragmentos de la mayoría de los BDM no afectó a la germinación pero si redujo el crecimiento y el nivel de clorofila en tomate y especialmente en lechuga. En general, los efectos identificados fueron consistentes con los de los compuestos liberados de los BDM encontrados anteriormente, y los fragmentos de PE no causaron efectos. En conjunto, los resultados sugieren que la composición química del BDM tiene un papel relevante en su interacción con el sistema radical de las plantas, y que las consecuencias de la presencia de fragmentos de BDM en el suelo se relaciona con esta composición, probablemente debido a que liberan componentes, más que a su presencia física. Finalmente, se estudió el impacto del acumulo en el suelo de fragmentos de BDM en la estructura y funciones de las comunidades microbianas del suelo agrícola. Tras tres meses de incubación, este acúmulo tuvo un bajo impacto en la diversidad y estructura de las comunidades microbianas del suelo. Sin embargo, algunos materiales provocaron cambios significativos en la abundancia y diversidad de determinados grupos bacterianos (Mater-Bi), fúngicos (papel MIMGreen) y protistas (Ecovio). Aunque la actividad microbiana total no se vio alterada, la actividad quitinasa, implicada en el ciclo del nitrógeno, disminuyó significativamente por la presencia tanto de BDM como de PE. Los resultados obtenidos en esta tesis doctoral aportan nuevo conocimiento sobre los potenciales efectos de los BDM en las plantas cultivadas y los microorganismos del suelo. Principalmente evidencian que los BDM (1) liberan con facilidad diversos compuestos mucho antes de que se inicie su biodegradación, tras el contacto con el agua, (2) la solución que contiene los compuestos liberados, en función de su composición, puede tener efectos sobre las plantas, (3) que el acúmulo de fragmentos de BDM en el suelo presenta capacidad de afectar al desarrollo de las plantas y de modificar la abundancia y diversidad de los microorganismos del suelo en función de la composición del BDM. Todo ello resulta relevante para el diseño y desarrollo de acolchados plásticos biodegradables que tengan un bajo impacto sobre las plantas cultivadas y sobre el medio ambiente.
Agricultural plastic mulches are an essential part of the agricultural system, contributing to face the food demand for the growing world population. Its use increases crop production, earliness and quality, reduces water consumption and pesticide delivery and prevents weed development. Mulches are mostly made of polyethylene (PE), non-biodegradable. Although they must be removed after harvesting, many fragments remain and accumulate in the field, reducing soil and crop quality. Biodegradable plastic mulches (BDM) have been fostered as a sustainable alternative preventing this accumulation. After harvest they will be biodegraded by the soil microorganisms in which they are integrated. However, this entails the various compounds (polymers and additives) present in the fragments are supplied to the soil, but their effects on cultivated plants and on soil organisms have hardly been studied. The objective of this PhD thesis is to evaluate the effect of eight BDM of different formulation, and their components, on the agricultural soil microbiome and on plants. For this purpose two plant species commonly cultivated with mulches which are among the main horticultural products were targeted, lettuce (Lactuca sativa L.) and tomato (Lycopersicon esculetum Mill.). One PE mulch was included as control mulch. Firstly, it was evaluated whether BDM can release compounds by contact with an aqueous environment before the onset of their biodegradation, and whether the released compounds can affect plant development. It was found that all the BDM tested released a diversity of compounds, which in several cases (Bioplast SP4 and SP6, Mirel and Biofilm) inhibited germination, root morphology or the development and physiology of both plant species, while those from other BDM caused minor (Ecovio, Mater-Bi) or non-significant (Bioflex) effects. Next, the released compounds were identified, which were eventually diverse, both components of its polymeric structure (1,4-butanediol, lactic acid, terephthalic acid, etc.) and additives (fatty acids, glycerol, etc.). Among those identified, the ones having previously shown to affect tomato and lettuce plant development (1,4-butanediol, lactic acid and adipic acid) were quantified. They were found to be in substantially lower concentrations than the ones responsible for causing effects on plants, which does not allow establishing a direct relationship between their release from BDM and the effects they may have on plants. Thirdly, the effect of the accumulation of BDM fragments in the soil on tomato and lettuce germination and plant development was studied. For most BDM, the presence of their fragments did not affect germination but it reduced plant growth and chlorophyll content in tomato and especially in lettuce. In general, the identified effects were consistent with those of compounds released from BDM previously found, and PE fragments caused no effects. Altogether, results suggest that the BDM chemical composition plays a relevant role in its interaction with the plant root system, and that the consequences of the presence of BDM fragments in the soil is related to this composition, likely due to the release of components, rather than to their physical presence. Finally, the impact of the BDM fragments’ accumulation in the soil on the structure and functions of the agricultural soil microbial communities was studied. After incubation for three months, this accumulation had a low impact on the soil microbial communities’ diversity and structure. However, some materials caused significant changes in the abundance and diversity of selected bacterial (Mater-Bi), fungi (MIMGreen paper) and protists (Ecovio) groups. Although the total microbial activity was not altered, the chitinase activity, involved in the nitrogen cycle, was significantly decreased by both BDM and PE presence. The results obtained in this doctoral thesis provide new knowledge on the potential effects of BDMs on cultivated plants and soil microorganisms. They mainly show that BDM (1) easily release several compounds soon before their biodegradation starts, after contact with water, (2) the solution containing the released compounds, depending on its composition, may have effects on plants and (3) the accumulation of BDM fragments in the soil has the capacity to affect plant development and to modify the abundance and diversity of soil microorganisms depending on the composition of the BDM. The results will contribute to the design and development of biodegradable plastic mulches that have a low impact on cultivated plants and the environment.

HDAC inhibitors are known to have anti-inflammatory properties. HDAC inhibitors are used in combination with Oct4 to generate induced pluripotent stem cells. I hypothesized that polyesters based on simple aliphatic HDAC inhibitors like valproic acid (VPA) and phenylbutyric acid (PBA) can serve as alternatives to existing polyester biomaterials with improved anti-inflammatory properties and as scaffolds for generation of iPSCs when used in combination with layer-by-layer thin films delivering reprogramming transcription factors. Vinyl ester of phenylbutyric acid (VEPA) and vinyl ester of valproic acid (VEVA) were synthesized from their carboxylic acid precursors using an iridium complex catalyst at yields as high as 97% and 73%, respectively. Amorphous poly(VEPA) and poly(VEVA) polymers were prepared by free radical solution polymerization and characterized for molecular weight and glass transition temperature. Poly(VEPA) and poly(VEVA) microparticles of 20-40 um diameter were prepared by an emulsion-solvent evaporation method and examined under scanning electron microscopy (SEM). Their hydrolytic degradation was studied by dry weight loss and HDAC inhibitor release via high performance liquid chromatography (HPLC) in the presence of varied pH and lipase-containing buffers. No significant degradation occurred within 5 days, and an MTT assay conducted on HeLa cells in the presence of these microparticles confirmed an absence of cytotoxicity. Poly(VEPA) and poly(VEVA) microparticles were not found to be a suitable biomaterial for hypothesized applications in light of their poor degradation characteristics in vitro.

Thesis (Ph.D.)--Biomedical Engineering, Georgia Institute of Technology, 2008.
Committee Chair: Dr. Niren Murthy; Committee Member: Dr. Carson Meredith; Committee Member: Dr. Julia Babensee; Committee Member: Dr. Mark Prausnitz; Committee Member: Dr. Ravi Bellamkonda.

Thesis: Ph. D. in Biological Chemistry, Massachusetts Institute of Technology, Department of Chemistry, 2014.
Cataloged from PDF version of thesis. Vita.
Includes bibliographical references.
Ralstonia eutropha, a Gram-negative proteobacterium, is capable of utilizing a plethora of simple and complex carbon sources derived from common waste streams. When experiencing nutrient stress in the presence of high carbons, R. eutropha can store carbon and energy in the form of polyhydroxyalkanoates (PHAs), a biodegradable and biocompatible plastic. In this thesis, the native carbon storage system was genetically disabled and the carbons redirected to produce biofuels. Key enzymes involved in R. eutropha CO₂, oil, and branched-chain amino acid metabolism were evaluated for the production of biofuels and bioplastics. R. eutropha valine biosynthesis pathway was modified, so its intermediate 2- ketoisovalerate can be converted to isobutanol, a drop-in biofuel that can directly substitute for fossil-based fuels and be employed within the current transportation infrastructure. Challenges facing large production of isobutanol include the tightly regulated biosynthetic pathway and product toxicity to the cells. Modification of both the pathway enzyme for reduced-feedback inhibition, in addition to genotypic adaptation to exogenous isobutanol stress produced insights that will allow for further improvements on isobutanol production. Furthermore, strains of R. eutropha were also engineered to produce isopropanol, another biofuel. Growth on carbon dioxide requires carefully balanced intercellular pH and ion transport. Four R. eutropha carbonic anhydrases were identified to play individual and non-complementary roles in CO₂ metabolism. An extracellular lipase and its chaperone were identified and characterized in R. eutropha. This lipase is crucial for growth on plant oil and when overexpressed, not only reduced the growth lag phase, but also eliminated the use of supplemental surfactants. Production of PHAs was achieved by using palm oil, one of the world's most abundant plant oils, as well as vinasse, a byproduct of ethanol fermentation. Metabolic versatility and genetic tractability combined with its ability to store a variety of carbons make R. eutropha an excellent platform organism for the production of value-added compounds. Demonstrated in this thesis are the production of biofuels and bioplastics from fructose, CO₂, oils, and mixed-organic acids.
by Jingnan Lu.
Ph. D. in Biological Chemistry

The food packaging industry is a £300bn global industry growing at a rate of 12% per year and increasingly favouring polymer or polymer-based materials. This generates 58m tonnes of "plastic" packaging waste annually in the EU and poses significant challenges for management given existing legislative constraints and increasing concerns surrounding the environmental impacts. The government, consumers, food retailers and pressure groups are all driving the demand for biodegradable packaging from renewable resources that can be disposed of with reduced impacts to the environment. Green Peace has devised a pyramid classification system of "Poisonous Plastics", which ranks plastics in terms of their harmfulness to the environment. They are campaigning against the use of oil-based materials and advocating the take up of biodegradable materials. The market for biodegradable food packaging is expanding rapidly but is still in its early stages of development and has not reached a critical mass to achieve significant market penetration. This is predominantly due to a lack of suitable materials that meet all environmental, functional and economical requirements. Whilst the long-term solution requires continued efforts in materials research and development, in the shorter term, changing working practices can abate the environmental impact of the industry. This research project tackled the challenge of environmental packaging from several directions: A novel starch-based material was developed that would fill the current gap in the food packaging market and facilitate recovery of the used materials by home composting. Using the sponsoring organisation as a case study, it was proved that by changing working practices by increasing rework and re-processing waste material for use in lower grade applications, both manufacturing costs and environmental impact can be reduced, thus benefiting both industry and the environment. A Life Cycle Assessment of selected biopolymers and oil-based polymers confirmed Green Peace's damning view of PVC and highlighted the need to develop biopolymers further. A domestic composting study of a range of commercially available "biodegradable" polymer materials revealed that a number of biodegradable packaging materials may typically biodegrade well in industrial high-temperature composting systems but fail to biodegrade under a low-temperature home composting environment and thus alerted the potential pitfall in waste management of some biodegradable polymers.

The purpose of this PhD thesis was to evaluate the biodegradability potential and ecotoxicological effects of several biodegradable plastics for agricultural use under controlled laboratory conditions in soil. In this study, commercial and still in experimental stage biodegradable plastic films were chosen: Mater-Bi® (corn starch), Bio-Flex® (polylactic acid), Biofilm® (cereal flour), Bioplast® (potato starch), MirelTM (polyhydroxyalcanoates) Ecovio® and Bionelle®. In addition, a sheet commercially known as MimGreen® paper was evaluated. Initially, a gravimetric and FTIR analyses were carried out to determine changes in both weight loss and molecular changes in the plastics respectively. A second experiment consisted in assessing the biodegradability of the materials by designing and building a respirometric system. This system allowed me to measure, with a higher sensitive, the biodegradation process of the materials under laboratory conditions in soil. In addition, I compared the biodegradability of these materials with the remains of a typical crop used for mulch application, tomato (Lycopersicum esculentum). Finally, the ecotoxicological effects of biodegradable films on Zea mays plants, earthworms Eisenia fetida and microbial soil activity were evaluated using the standardised regulations or existing methods. Thus, I was able to prove ecological advantages of these materials.
El propòsit d'aquesta tesi doctoral ha estat valorar el potencial de biodegradabilitat i efectes ecotòxics de diferents plàstics biodegradables per a ús agrícola sota condicions controlades al laboratori. En l'estudi es van triar set films plàstics biodegradables de diferent composició química, tant comercial com encara en fase experimental: Mater-Bi® (midó de blat de moro), Bio-Flex® (àcid polilàctic), Biofilm® (farina de cereals), Bioplast® (midó de patates), MirelTM (polihidroxialcanoatos), Ecovio® i Bionelle®, a més d'una làmina de paper (Mimgreen®). Es van realitzar dos experiments. El primer concistía en realitzar un estudi gravimètric per mesurar el grau de degradació dels plàstics mitjançant la pèrdua de pes, a més es va dur a terme un anàlisi espectroscòpic FTIR, que va permetre discernir els canvis en els entorns moleculars que faciliten o dificulten el procés de biodegradació dels materials. El segon experiment va consistir a valorar la biodegradabilitat dels materials mitjançant el disseny i construcció d'un sistema respiromètric, que va permetre mesurar amb major sensibilitat el grau de biodegradació dels materials seleccionats sota condicions de laboratori en sòl. Addicionalment es va comparar la biodegradabilitat dels materials provats amb restes d'un cultiu típic d'ús de encoixinat com és el cas del tomàquet (Lycopersicum esculentum). Finalment, es van investigar els efectes ecotòxics dels films biodegradables sobre plantes de Zea mays, cucs Eisenia fetida i l'activitat microbial del sòl, els assaigs van ser realitzats a partir de les normatives o mètodes estandarditzats vigents el que va permetre comprovar els avantatges ecològics d'aquests materials.
El propósito de la presente Tesis Doctoral ha sido valorar el potencial de biodegradabilidad y efectos ecotóxicos de diferentes plásticos biodegradables para uso agrícola bajo condiciones controladas de laboratorio en suelo. En el estudio se eligieron siete films plásticos biodegradables de diferente composición química tanto comercial como aún en fase experimental: Mater-Bi® (almidón de maíz), Bio-Flex®(ácido poliláctico), Biofilm® (harina de cereales), Bioplast® (almidón de patatas), MirelTM(polihidroxialcanoatos), Ecovio® y Bionelle®; además de una lámina para acolchado con el nombre de papel Mimgreen®. Como primer paso diferentes ensayos fueron realizados entre ellos uno gravimétrico para medir la pérdida de peso de los materiales y otro mediante análisis espectroscópico FTIR, lo que permitió discernir los cambios en los entornos moleculares que facilitan o dificultan el proceso de biodegradación de los materiales. El segundo experimento consistió en valorar la biodegradabilidad de los materiales mediante el diseño y construcción de un sistema respirométrico que permitió medir con mayor sensibilidad el grado de biodegradación de los materiales seleccionados bajo condiciones de laboratorio en suelo. Adicionalmente se comparó la biodegradabilidad de los materiales probados con restos de un cultivo típico de uso de acolchado como es el caso del tomate (Lycopersicum esculentum). Finalmente, se investigaron los efectos ecotóxicos de los films biodegradables sobre plantas de Zea mays, lombrices Eisenia fetida y la actividad microbial del suelo; los ensayos fueron realizados a partir de las normativas o métodos estandarizados vigentes lo que permitió comprobar las ventajas ecológicas de estos materiales.

Mestrado em Engenharia do Ambiente - Instituto Superior de Agronomia
The use of plastic mulch in agriculture had its beginning in the middle of last century and since then its use has been intensified and the costs of send this residue to appropriate final destination lead it often to be left or burned in open field, causing huge environmental concerns. The biodegradable mulch films, which can be incorporated in the soil at the end of the crop appear as a possible solution for this problem. The goal of this work was to test the biodegradability of 5 plastic mulches, made from biodegradable polymers, comparing to conventional Polyethylene (PE). The biodegradability was tested in laboratory by means of a respirometric test that followed the standard EN ISO 17 556, and in field conditions, by observation and calculation of the percentage of area lost, along the time, in net frames containing the various biodegradable plastics. The field trials to assess fruit productivity and quality were performed during two years. One of the biodegradable mulches stands out for its good performance and seems as a very promising mulch that may be a viable replacement for conventional polyethylene.

Extensive quantities of apple pomace are generated annually but disposal of this waste is still much disputed. In EU alone, 500 000 tons are produced every year. Without further treatment, the acidic character of apples with their high sugar and low protein content makes the pomace unsuitable for landfilling and animal feedstock. However, further treatment is usually not economically feasible. This study addresses this issue by introducing a new approach for the apple pomace to produce sustainable materials.  The high content of sugars in apple pomace which can be reshaped and reformed at higher temperatures makes the waste material suitable for plastic production. Other components found in apple pomace are 5 % proteins and 1.5 % fats. Fibers are abundant, dietary fibers amounts for more than half (55 %) the original apple pomace weight. Phenols, sorbitol and acids can be found in minor mount, 2 % or less. The apple pomace itself is a mixture of mostly pulp and peel which corresponds to 9/10 of the total mass. Whereas seeds, seed core and stalk are the remaining 1/10. The possibilities of utilizing apple pomace to produce biofilms and 3D shapes have been investigated. The effects of introducing orange pomace, another waste material produced in extensive quantities, to apple pomace samples has also been studied.  Two methods were used to produce bioplastic materials; solution casting and compression molding. Glycerol was used as a plasticizer. Apple pomace, either washed or not washed, was oven-dried and milled into a fine powder. Using compression molding, plates or cups of the two powders with different amounts of glycerol were prepared. Mixtures of apple pomace and orange pomace, with or without glycerol, were prepared in the same way. The apple pomace was also used in a film casting method to produce plastic films. Applying laser cutting to the plates and plastic films, dog-bone specimens were created whose mechanical properties were analysed using a universal testing machine.  Highest values in terms of tensile strength and elongation at max was reached with bioplastics produced from solution casting where the values varied in the range 3.3 – 16 MPa and 11 – 55 % respectively. The compression molding approach resulted in tensile strength values in the range 0.94 – 5.9 MPa whereas the elongation at max was in the range 0.30 – 1.9 %. A possible application for this material could be disposable tableware which does not require high mechanical strength.  It was shown that it is possible to produce 3D structures and plastic films from apple pomace. Washed apple pomace with glycerol has similar properties as not washed apple pomace without the plasticizer. Adding orange pomace to apple pomace samples increases the tensile strength at the expense of the elongation at max. The pressing conditions and powder size greatly effects the mechanical properties, where a larger powder size lower the values for the mechanical properties. This new approach paves the way for a new utilization of apple pomace to replace some petroleum-based materials and at the same time solve the disposal problem of apple pomace.

The aim of this study was to develop a benign process for removal of metal residue and other impurities from biodegradable poly(propylene carbonate) (PPC) to broaden its applications. It was demonstrated that the properties of PPC are favourable for fabrication of medical devices and food packaging products. For Instance, mechanical properties of PPC were either comparable or superior to commercial polymers such as low density polyethylene and polybutyrate adipate terephthalate (Eco-Flex). Besides, permeability of PPC to oxygen and moisture was remarkably lower than these polymers. Furthermore, PPC was chemically stable in food simulated media. The high level of zinc glutarate, a metal-based catalyst, in PPC was remarkably reduced by using a novel technique in which CO2 laden water was used as a solvent. The extraction efficiency of this method at 45 ˚C and 70 bar was nearly 90% that was two-fold higher than using acidic solvents. Additionally, at these conditions other impurities such as cyclic propylene carbonate were removed from PPC that further promoted its properties. For example, the thermal decomposition temperature of PPC was shifted from 124˚C to 214˚C and its mechanical strength was enhanced by 40%. Plasma modification was used as an efficient method for chemical immobilization of thymol, an active, natural antimicrobial agent on PPC surface. The results of bacterial counting and bacteria inhibition zone showed that the thymol immobilization was efficient when using plasma at low energy for a period of 15 minutes. This study led to design of two benign processes for purification of PPC and fabrication of its antimicrobial films. This antimicrobial, biodegradable polymer that eradicates the use of preservatives and metal nano-particles is attractive for biomedical devices and food packaging products. Commercialization of theses methods will be of great value for reducing the disposal of non-degradable polymer in landfills that is a huge environmental issue.

Os Polihidroxialcanoatos (PHAs) são poliésteres naturais, acumulados por diversos microorganismos como reserva de carbono e energia, sendo hoje considerados a melhor alternativa para o plástico tradicional, devido às suas propriedades biodegradáveis e biocompatíveis. Escherichia coli é considerada um hospedeiro ideal para a produção de PHAs, devido a várias vantagens sobre outros microrganismos. Linhagens de Escherichia coli foram avaliadas com o intuito de escolher aquela que apresentasse as melhores características como hospedeira dos genes envolvidos na produção dos PHAs. A linhagem E. coli LS5218 apresentou os melhores resultados de consumo das diferentes fontes de carbono avaliadas, assim como as melhores velocidades de crescimento. Esta linhagem tem a capacidade de produzir, além do P3HB, o copolímero P3HB-co-3HV. Os resultados obtidos a partir dos cultivos em frascos agitados demonstraram que a linhagem E. coli LS5218 consegue produzir P3HB, correspondendo a cerca de 40% da massa seca celular. A limitação do crescimento nos cultivos em biorreator, mediante o controle da velocidade de alimentação da fonte de carbono e nitrogênio, favoreceu a síntese e acúmulo do polímero. A análise de fluxos metabólicos indicou que existe uma considerável perda de carbono na forma de CO2, devido ao suprimento de NADPH pela isocitrato desidrogenase. A análise de modos elementares aponta que, para se atingir desempenhos melhores, o fluxo na via das pentoses deveria ser aumentado significativamente, de forma a que todo o NADPH para biossíntese de P3HB fosse suprido por essa via, e, que o fluxo no ciclo de Krebs deveria ser o menor possível, suprindo apenas a demanda de precursores para a biossíntese de biomassa residual. Finalmente, foi possivel obter, embora em pequenas quantidades, acúmulos do copolimero a partir de E. coli LS5218 expressando os genes de C. necator. A partir destes resultados, fica evidente que a utilização da linhagem LS5218 é interessante sob o ponto de vista industrial, devido ao fato de ela utilizar eficientemente fontes de carbono, e ter a capacidade de acumular o P3HB e seu copolímero P3HB-co-3HB.
The Polyhydroxyalkanoates (PHAs) are natural polyesters accumulated by several microorganisms as a source of carbon and energy, now considered as the best alternative to the traditional plastic due to their biocompatible and biodegradable properties. Escherichia coli is considered an ideal host for the production of PHAs, due to several advantages over other microorganisms. Escherichia coli strains were evaluated in order to choose the one that presented the best characteristics as a host of genes involved in the production of PHAs. The strain E. coli LS5218 showed the best results in terms of consumption of different carbon sources being tested and the best growth rates. This strain has the ability to produce the P3HB and additionally, the copolymer P3HB-co-3HV. The results from the cultivation in shaked flasks showed that the strain E. coli LS5218 can produce P3HB, corresponding to 40% approximatelly of the dry cell mass using glucose as carbon source. Limiting the growth of cultures in a bioreactor by controlling the feeding speed of the carbon and nitrogen source, favored the synthesis and accumulation of the polymer. Analysis of the metabolic flux indicated that a considerable loss of carbon in the form of CO2 due to NADPH supply by the isocitrate dehydrogenase. Elemental analysis shows that to achieve better performance, the flow of the pentose pathway should be substantially increased, in order to all the NADPH for the biosynthesis of P3HB can be supplied by this pathway and that the flow in the Krebs cycle should be as small as possible, only to supply the demand of precursors for the biosynthesis of residual biomass. Finally, it was possible to obtain, although in small quantities, accumulation of the copolymer using E. coli LS5218 expressing the genes of C. necator. From these results it is evident that the use of LS5218 strain is interesting from the industrial point of view due to the fact of efficiently utilize carbon sources and have the capacity of accumulate the P3HB and its copolymer P3HB-co-3HB.

Mestrado em Engenharia do Ambiente - Tecnologias Ambientais - Instituto Superior de Agronomia
The composting has proven a good alternative in the management, treatment and valorization of municipal solid waste. Depending on the raw materials used for its production, the product may be considered organic fertilizer/corrective to be used in agriculture activities. The present work was developed aiming the evaluation of the MSW composting evolution, by the determination of physical, physical-chemical and biological parameters, in biomass collected along the process, as well as the assessment of stability/maturation degree of the final compost. For each collected sample it was also introduced two different types of biodegradable/compostable plastics, each sample corresponding to a particular phase of stability/curing of composting process in order to evaluate the influence of these plastics in the samples that was obtained and the possible occurrence of biodegradation of plastics in the several phases analyzed. The results showed that the parameters fulfilled the existing literature, allowing the compound the designation of matured/stabilized. The biological characterization of the final compost showed that it presents phytotoxicity, which fact is related to the presence of ammoniacal nitrogen and high electrical conductivity. The introduction of biodegradable plastics in the process didn’t affect any parameter analyzed, showing increasing degree of biodegradability over the course of analysis.

This thesis covers the design of an automated multiunit composting system (AMUCS) that was constructed to meet the experimental apparatus requirements of the ASTM D5338 standard. The design of the AMUCS is discussed in full detail and validated with two experiments. The first experiment was used to validate the operation of the AMUCS with a 15 day experiment. During this experiment visual observations were made to visually observe degradation. Thermal properties and stability tests were performed to quantify the effects of degradation on the polymer samples, and the carbon metabolized from the degradation of samples was measured. The second experiment used the AMUCS to determine the effect of synthetic clay nanofiller on the aerobic biodegradability behavior of poly (3-hydroxybutyrate-co-3-hydroxyvalerate).

Environmental concerns arising from the use of non-degradable plastics have resulted in search for suitable substitutes. The thesis deals with new nanostructured composites based on reinforcement of nanocellulose whiskers in "green" polymers such as xylan. Since the reinforcement filler and the matrix are both biobased and are thereby environmental friendly. Xylan incorporated with cellulose whiskers films provided with improved water and oxygen barrier properties. It appears that the high degree of crystallinity of cellulose whiskers, dense composite structure formed by the whiskers and rigidly hydrogen-bonded cellulose whiskers can cause cellulose whiskers to form integrated matrix which contribute to substantial benefit in the overall reduction of transmission rate. The spectral data obtained for the NCW/xylan nanocomposite films showed that the amount of xylan adsorbed to cellulose increases with the addition of NCW in the matrix. In addition, NMR T2 relaxation experiments studies were conducted to investigate the change in the nature of carbohydrate-water interactions as a result of NCW incorporation. These results facilitated an improved understanding of the mechanisms involved in the superior barrier and mechanical properties of xylan-whisker nanocomposite films. XRD studies show that when a xylan-whisker nanocomposite films is formed the mixing occurs on the atomic scale and NCW loading increases the matrix crystallinity.

Polihidroxialcanoatos (PHA) produzidos por Pseudomonas sp. LFM046 a partir de carboidratos e ácido propiônico contem monômeros com número ímpar e par de carbonos, representando um bom modelo para o estudo do metabolismo de propionato. Genes relacionados ao ciclo do 2-metilcitrato foram encontrados em todas as espécies de Pseudomonas compondo um operon prpRBCAcnMprpFD. Genes da via do metilmalonil-CoA não foram encontrados em Pseudomonas. Genes da a-oxidação de propionato foram encontrados apenas em P. aeruginosa. A análise de um mutante prp obtido por inserção de transposon revelou que estava mutado no gene prpB, relacionado ao ciclo do 2-metilcitrato. A análise de mutantes obtidos por radiação ultravioleta revelou que dois devem estar afetados em via menos relevante para o metabolismo de propionato e outros dois na ativação desse ácido orgânico. Experimentos com propionato marcado (1C13) demonstraram que as vias do oxobutirato, do metimalonil-CoA e do 2-hidroxiglutarato não devem contribuir para o metabolismo de propionato em Pseudomonas sp. LFM046.
Polyhydroxyalkanoates (PHA) produced by Pseudomonas sp. LFM046 from carbohydrates and propionic acid contains monomers with odd and even number of carbons, representing a good model to study the propionate metabolism. Genes related to 2-methycytrate cycle were found in all Pseudomonas species organized in an operon prpRCAAcnMprpFD. Genes related to the methylmalonyl-CoA pathway were not found in Pseudomonas. Genes related to the propionic a-oxidation were found only in P. aeruginosa. Analysis of a prp mutant obtained by transposon insertion revealead that it was mutated in prpB gene, related to the 2-methylcytrate cycle. The analysis of mutants obtained using ultraviolet radiation showed that two should be affected in less relevant propionate metabolism pathways and other two in the activation of this organic acid. Experiments with labeled propionate (113C) demonstrated that the oxobutyrate, methylmalonil-CoA and 2-hydroxyglutarate pathways should not contribute to the propionate metabolism in Pseudomonas sp. LFM046.