ENVIRONMENTALLY SOUND MANAGEMENT OF WASTE PET BOTTLES

ENVIRONMENTALLY SOUND MANAGEMENT OF WASTE PET BOTTLES  

ABSTRACT  

This study has been carried out to assess the waste management of PET bottles and effectively manage the PET plastic bottles by identifying practical means and introducing recycling as a cleaner production tool to achieve sustainable development goals. The science of post-consumer PET recycling is based on the fact that this polymer is non-degradable by nature. There has been a growing need for chemical recycling processes as a successful method for post-consumer PET transformation into monomers that can be used in the production of new bottles, textile materials, drug production, etc. This research focused on the depolymerization of waste PET bottles in an alkaline medium with the aim of response surface methodology.PET flakes from waste bottles were depolymerized at atmospheric pressure in an alkaline solution of potassium hydroxide in selected aliphatic alcohols and glycol to produce terephthalic acid. Response Surface Methodology (RSM) based on Central Composite Design model was used, with design variables being temperature, reaction time, and alkali concentration. The solid product was analyzed using FTIR and its acid value was determined.From the results obtained, it was found that reaction models obtained are significant (p < 0.05 for alcohols), accounting for 98% of the variations observed. For ethanol media, the optimum condition for PET decomposition was 0.35g/L, 66.82mins, and 2000C, which gave the decomposition of 79.4%. For propylene glycol, an optimum decomposition of 74.6% was obtained at a reaction temperature, time, and alkali concentration of 2200C, 60mins, and 0.5g/L respectively. For propylene glycol, the reaction time had more effect on the percentage decomposition, while the temperature was the dominant factor for the ethanol media. Comparing the IR spectra of the final product obtained from the alcohol with that of pure terephthalic acid, it can be concluded that the solid product obtained was terephthalic acid which can be used in pharmaceutical industries as a raw material in producing certain drugs.

 

CHAPTER ONE INTRODUCTION 1.1 Background of the Study            Wastes are materials of solid or semi-solid character that the possessor no longer   considers of sufficient value to retain (Gilpin, 1976). The New York State Department of     Environmental Conservation also defined solid wastes in simple words as any discarded     (abandoned  or  considered  waste-like)  materials.    There are different  types  of  waste:     municipal waste  (including  household  and  commercial  waste), industrial  waste   (including manufacturing), hazardous waste, construction and demolition waste, mining    waste,    waste    from    electrical    and    electronic    equipment,   biodegradable  municipal    waste,  packaging waste,  and agricultural waste. Solid wastes can be solid, liquid, and     semi-solid or containerized gaseous material.  Also,  there  are  various  sources  of  waste:     residential, industrial,  commercial,  institutional, construction, and  demolition  waste;     municipal services manufacturing process, agriculture.            Municipal  solid  waste  (MSW)  is  defined  to  include  refuse from  households,   nonhazardous solid  waste  from  industrial,  commercial,  and institutional  establishments   (including hospitals), market waste, yard waste, and street sweepings.    MSW is defined   by Cointreau (1982) as non-air and sewage emissions created within and disposed of by   a municipality,  including  household  garbage,  commercial  refuse,  construction  and   demolition debris,  dead animals,  and abandoned vehicles.  Municipal solid waste is     generally made up of paper, vegetable matter, plastics, metals, textiles, rubber, and glass   (USEPA, 2003).           The waste management problem in  Nigerian cities is becoming more alarming.    The volume    and    range    of    solid    wastes    generated    daily    in    Nigeria    has    been                                                                                          2    increasing within the last few years. This is mainly due to the high population growth,   urbanization, industrialization, and general economic growth (Ogwueleka, 2004).            The common waste disposal methods are Sanitary landfill which is the disposal   of waste    material    or    refuse    by    burying    it    in    natural    or    excavated    holes,      depressions, incineration;  burning the refuse to ashes.  There  is  also  the  compost    heaps  where  the refuse  is  left  to  degrade  by  aerobic  microorganism  and it's used    as    fertilizer,    then    the  resource    recovery,    a    process    of    recovering    energy    and    reusable materials from solid waste before decomposition or landfill.  The resources   also goes  further  to  be  utilized  by the  principle  of 3Rs (Reduce,  Reuse  and  Recycle)   (Taiwo, 2011).             Environmentally  sound  waste  management  is a crucial problem  not  only  for     developing countries but for the developed countries as well. However, the plastic waste   as a significant portion and component of the municipal solid waste is a quite problematic   for its non-biodegradability and therefore can stay in the environment for a considerable   length of time carrying all sorts of problems.           There are two major categories of plastics include thermoplastics and thermosets.     Thermoplastics  refer  to  plastic  materials  that  can  be  formed  into  other  products  by  re-  melting or processing into different shapes by the application of heat and pressure. These   are easily recyclable into other products. These thermoplastics include polyethylene, low   and  high  density  (LDPE,  HDPE)  polypropylene  (PP),  polyvinyl  chloride  (PVC),     polystyrene  (PS),  polyethylene terephthalate  (PET), etc.  Thermoset  plastics  contain   alkyd, epoxy, ester, melamine-formaldehyde,  polyurethane,  etc.  which  are  cross-linked   on curing and will not soften with heat to allow these to be formed into different shapes.                                                                                           3            Polyethylene terephthalate (PET) is widely used in several key products, as fiber   for textile applications and into backing materials for audio and videotapes.  Biaxially   oriented polyester film is used for packaging and as thermoformed sheets in a frozen meal   trays for microwave ovens. Pet films are used in electric devices as well.            The best-known product  made  from  aromatic  polyester  (PET); however  is  the   blow-molded water and  soda bottles for soft drinks and other household  and consumer   products. PET is a relatively new packaging resin. Soft drink bottles remain the biggest   the user of PET resin. ’Consumer' bottles are used for other products such as salad dressing,   peanut butter and jellies. Half of the polyester carpet made in the United States is made from   recycled PET bottles. The rise of the use of custom bottle and the increased consumption of   water and soft drinks  away from home have created  challenges for increasing  the PET     recycling rate. PET  use  has  reduced  the  size  of  the  waste  stream  because  PET  has   replaced heavier steel and glass containers.            The  use  of  Polyethylene  terephthalate  also  known  as  PET (a  plastic  resin   materials  used  for  making  packaging  materials  such  as  bottles  and  food  containers)  is     increasingly becoming paramount among manufacturers, as they used these PET bottles   to  package their products because it is  an excellent  barrier material  with high strength,   thermostability and transparency.  The consumer also  prefer  or  choose  PET  because  it  is     inexpensive,  lightweight,  resealable,  shatter-resistant, and  recyclable  among  other   reasons.  Every  year  not  less  than  200  billion  bottles  of  bottled  water  are  consumed   globally.  Only  about  15%  of  this  quantity  is  recycled  in  all  recycling  plants  across  the   globe while the remaining ones end up in trash bins, landfills, or open dumpsites in cities   across the globe (Abdulkarim and Abiodun, 2012).            In  Nigeria,  all  of  the  brands  of  bottled  water,  soft  drinks,  beverages, etc.,  are   always  available  in  different  types  of  packaging  materials – PET  bottles,  cans,  glass                                                                                         4    bottles, polythene sachet, and synthetic paper packages. According to Oni (2011), not less   than  200  million  PET  bottles are produced in Nigeria per day.  From  his  analysis,  the     consumption of the products creates waste which is above the ability of the producer to   manage.           One  of  the  approaches  to the solution  of  the  plastic  waste  problem  is  through     recycling for its numerous benefits justifying the aim of this study that essentially meant   to contribute to sustainable consumption and production of PET bottles in particular.     Recycling of plastics should be carried in such a manner to minimize the pollution level   during the process and as a result to enhance the efficiency of the process and conserve   the energy.  Plastics  recycling  technologies  have  been  historically  divided  into  four   general types -primary, secondary, tertiary, and quaternary.    Primary recycling  involves the processing  of waste/scrap  into  a  product  with     characteristics similar to those of the original product.   Secondary recycling involves the processing of waste/scrap plastics into materials that have     characteristics different from those of original plastics products.   Tertiary recycling  involves  the  production  of  basic  chemicals  and  fuels  from  plastics     waste/scrap as part of the municipal waste stream or as a segregated waste.     Quaternary recycling  retrieves  the  energy  content  of  waste/scrap  plastics  by     burning/incineration.   1.2 Statement of Research Problem           In  recent  years,  there  has  been  a  phenomenal  increase  in  the  volume  of    wastes generated daily in the country.  This is due to a number of reasons    including    the increasing    population    growth    rate,    increasing   urbanization,      industrialization and economic growth.  In  addition,  many  urban  areas  of  Nigeria                                                                                          5    lack effective waste management systems.    As a result, most urban households  

resort to the haphazard dumping, burning, and or burying of solid wastes.      (Agunwamba et al. 2003).            The  non – biodegradability  of PET  is  the  major  obstacle  to  disposing of its  waste   using conventional methods such as landfilling and incineration. Recycling is assumed to   be one of the best approaches to solve the accumulation of PET waste problem. Among   the various method of PET recycling, only chemical recycling conforms to the principles   of sustainable development because it has the potentials for yielding the raw materials from   which PET is originally made. However, the various chemical recycling routes reported   in  various  works  (such  as  hydrolysis,  alcoholysis, and  aminolysis)  are  fraught  with     shortcomings  such  as  the  need  for  high  pressure  and  corrosion-resistant  equipment   (Kondo and Genta, 2001), high temperature (Campanelli et al., 1993), and long reaction   time (Yoshioka et al., 2003; Sunain et al., 2012). There is therefore a need to develop a   relatively  simple,  yet  effective  means  of  depolymerizing  postconsumer  PET  using     inexpensive and readily available solvents.   1.3 Objectives of the study   Major objective           To assess the waste management and to effectively manage the waste PET bottles   by identifying practical means to introduce cleaner production tools mainly recycling in   order to achieve sustainable development goals.   Specific objectives        · To  collect  and  study  available  data  on  plastic  and  PET  plastic  bottles  in           particular.                                                                                         6        · To  effectively  manage  the  PET  plastic  bottles  waste  and  minimize  the volume             (industrial/domestic).   1.4 Scope of the Study           Solid  Waste Management all over the world is a  complex one.  There  is  a   proposed waste management hierarchy which is shown in Figure 1.1. However, the main   the focus  of  this  research  work is  on  how  to  manage  the  PET  waste  menace through   recycling.  Recycling  was  chosen  because  it has  numerous  advantages  over  the  other   modes of waste disposal and comparatively less capital intensive.            There  are three  recycling  processes  namely mechanical  recycling,     feedstock/chemical recycling and incineration/energy recovery.  This thesis  work   however, adopted chemical recycling  since  that  is  more  appropriate  for  a  developing   a country such as Nigeria. The thesis, therefore, covers the initial upgrading techniques, size   reduction  techniques,  reprocessing  techniques  through to  the  final product     manufacturing.  An  integrated  waste  management  approach as  shown  in  the  waste   hierarchy  is  however the  preferred  choice for  an  efficient  and  effective  waste     management for any country. Though  the  viability  and  feasibility  of  recycling  would   depend  on  a  large extent to the  availability  of potential markets  for  the  reprocessed   products that are not discussed within this thesis work. However, considering the income   levels of the majority of the populace, it is obvious that reprocessed products would attract   high demand.     

                          Figure 1.1:                                                                                          7  Image                          Figure 1.1: Waste Management Hierarchy   Source: Porteus, A., 2005     1.5 Justification of the Study           The  wastes  in  any  environment spoil  the  aesthetics  of that environment,   especially as an academic environment.  The  major  reason  for  this  is  poor  waste     management.  Waste  management  is  an  important  and  integral part  of  our  society  and   therefore needs to be acknowledged as one of the few things that may help to preserve   the beauty and splendor of any environment for future generations.  Waste generation   increases with population expansion and economic development.   Improperly  managed   solid waste poses a  risk to human health and the environment.    Uncontrolled dumping   and  improper waste  handling  causes a variety  of problems, including  contaminating   water,  attracting insects  and  rodents,  and increased flooding  due  to  blocked  drainage   canals or gullies. In addition, it may result in safety hazards from fires or explosions.             Improper  waste  management  also  increases  greenhouse gas (GHG)  emissions,   which contribute to climate change.    Planning  for  and  implementing a  comprehensive   program for waste collection, transport, and disposal-along with activities to prevent or   recycle waste-can eliminate or at least reduce these problems. This  study  examines the   need  for effective  municipal solid  waste  management (i.e. PET) in  an environment in   order to achieve a clean and hygienic environment.   

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