Going Bananas!-Using Banana Peels in the Production of Bio-Plastic As A Replacement of the Traditional Petroleum Based Plastic

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  • 1Short Project Description 
  • 2Summary 
  • 3About MeAbout Our Team 
  • 4Question / Proposal 
  • 5Research 
  • 6Method / Testing and Redesign 
  • 7Results 
  • 8Conclusion / Report 
  • 9Bibliography, References and Acknowledgements 

My project is about using banana peels in the production of bio-plastic as a replacement of the traditional petroleum based plastic. In this project, I developed a method for making plastic by using banana peels and found new areas for the use of the plastic that I manufactured: using the bio-plastic in the making of cosmetic prosthesis and in the insulation of cables.

This project was done over a time period of 2 years. During this time period, I was able to succeed in my endeavor to manufacture plastic that can actually be used in daily life.

 

 

 

 

 

 

 

 

 

In this project, my aim was to develop a method for using banana peels in the production of bio-plastic as a replacement for the traditional petroleum based plastic. The reason why I chose this particular aspect of science is that the bio-plastic is such a new concept and its range of use has been widening ever since it has been discovered (especially in the 21st century). The bio-plastic is a material which has the potential of causing a biological reform by means of reducing the amount of pollution caused by other plastic materials which contain petroleum derivatives. Apart from this, the bio-plastic industry’s newness creates room for further development of the bio-plastics manufactured so far. Over a time period of 2 years, I was able to design a method and produce non-decaying plastic using banana peels which can be molded into a making cosmetic prosthetics or used in the electrical insulation of cables. This outcome supported my hypothesis. The method I designed is so simple, it is possible to say that one could actually do it at home (some chemicals used are irritant but not extremely dangerous). This way, anyone could use this plastic. Also, our beautiful planet will be spared from the consequences of the production of plastics with petroleum derivatives in them such as pollution of the air, land and water. In the future, I would like to do more projects concerning the environment. For example, my biggest dream is to build a greenhouse made of waste materials.

I live in Istanbul, Turkey and I go to Koc High School. I love doing scientific research.

When I was in the 4th grade, I was recommended to take a WISC-R test and got accepted to a school for gifted students, funded by the government, for the sole purpose of providing these gifted students with an environment in which they can explore and further develop their already advanced skills and talents. I was accepted to the Chemistry, Biology and Mathematics program there and have been attending this school for the last 6 years. The Biology and Chemistry programs have made me passionate about science as welll as allowing me to learn and apply the steps of scientific research, conducting experiments and writing lab reports.

Marie Curie has been a major inspiration and admiration of mine, being a female scientist who devoted her life to her study of radioactivity; challenging gender norms along the way. She is the best role model for aspiring young female scientists such as myself.

In the future, I would like to study medicine in the US, at a college which offers the best education to its students. Winning this competition will bring me one large step closer to my dream of attending Med School, since the prizes will help me fund my education as well as allowing me to have an once-in-a-lifetime experience. But more importantly, winning will show me that I am in the right path to my future, and science is my calling.

Can a method for using banana peels in the production of bio-plastic as a replacement for the traditional petroleum based plastic be developed?

During this project, I was seeking the answer to this question. The problem that I was trying to solve was that the plastic we use in today’s world contains petroleum derivatives and these are causing environmental pollution. If plastic (a material with such great range of use in our daily lives) can be manufactured by the use of banana peels (a material which is thrown away every day), then this plastic would become a rival to the petroleum-based plastic we use nowadays. The rival banana-plastic would provide the consumers of plastic with an alternate option and this would actually decrease the rate of pollution of the environment caused by the use of petroleum-based plastic thus, providing the generations to come with a planet worth living in.

Hypothesis:

If I attempt to develop a method for using banana peels in the production of bio-plastic, then I will succeed and manufacture bio-plastic from banana peels because fruits rich with starch are preferred in the making of bio-plastic and the banana peel is rich with starch.

 

The banana fruit’s peel was selected for this experiment because it is a waste material rich of starch-according to Songklanakarin Journal of Science and Technology, the proximate composition of a banana peel is shown below.

Items    Content (g/100 g dry matter)

    Protein:  8.6±0.1

    Fat:       13.1±0.2

   Starch:  12.78±0.9

   Ash:      15.25±0.1

   Total dietary fiber: 50.25±0.2

The banana peel is something we throw away every day, but little do we know, it has much more efficient uses. For example, in Thailand, 200 tons of banana peels are thrown away daily and this number increases each year (Pangnakorn, 2006) and in the fruit industry, banana peels make up around 30-40g per 100g of the total revenue. All those peels may be put into much more use.

According to The Packaging Bulletin Magazine’s January issue, it is a proven fact that starch and cellulose are important raw materials used in the bioplastic industry (Packaging Bulletin, 2009). Since they are rich with starch and this starch is very easy to extract, potatoes are the most commonly used raw materials. In RSC’s “Making plastic from potato starch” experiment, a simple way of making plastic from potato starch is introduced and the chemical basis of the process is explored in depth. The propane-1,2,3-triol used in the experiment functions as a plasticizer, an additive used to develop or improve the plasticity of a material. It disconnects the polymer chains from one another; restraining them from becoming rows of chains and acquiring a crystalline structure. The formation of the crystalline structure is undesired because it is a brittle and fragile structure which makes the plastic brittle and fragile as well. Instead of the crystalline structure, the formation of film (not becoming rows of chains of polymers) is desired.

Starch consists of two different types of polymer chains, called amylose and amylopectin, made up of adjoined glucose molecules. The hydrochloric acid is used in the hydrolysis of amylopectin, which is needed in order to aid the process of film formation due to the H-bonding amongst the chains of glucose in starch, since amylopectin restricts the film formation. The sodium hydroxide used in the experiment is simply used in order to neutralize the pH of the medium.

The 9th and 10th pilot experiment I had conducted had been successful in producing plastic, but had started to decay after only 3 days. As a result of the research done to address this issue, I found out that in order to improve shelf life of post-harvest wild mango fruits, sodium metabisulphite can be used (Ibadan, 1991). This is why the sodium metabisulphite solution was used in this experiment.

Simalarly sized bananas with no injury or bruises on the skin were purchased from the bazaar in order to ensure the experimental process was fair. These bananas were at the color index of 4 (green-yellow) according to the CSIRO banana ripening guide (CSIRO, 1972).

A large variety of pilot experiments were done in order to establish the effects of placing the banana peels in 0.5% Na2S2O5 solution, using different concentrations of HCl and NaOH, using different amounts of banana paste, on the quality of the plastic produced. Based on the results of the 12 pilot experiments, the following 2 experiments were selected and were repeated four times:

  1. Dipping the banana peels in 0.5% Na2S2O5 solution prior to the boiling and pureeing processes and using 0.1 M HCl and NaOH solutions in the production of the plastic.
  2. Dipping the banana peels in 0.5% Na2S2O5 solution prior to the boiling and pureeing processes and using 0.5 M HCl and NaOH solutions in the production of the plastic.

These treatments were selected based on the quality of the plastic produced by means of thickness, strength and shelf life.

Preperation of banana skins:

  1. The peels of the bananas were removed using a stainless steel knife.
  2. An 800ml beaker was filled with distilled water and placed over a Bunsen Burner.
  3. The banana peels were placed in the beaker and were boiled for 30 minutes.
  4. After the boiling process, the beaker was removed from the Bunsen burner and the peels were decantated off the water and placed on and covered with a dry gauze pad, left to dry for 30 minutes.
  5. After the peels were dried, they were placed in a clean 800ml beaker.
  6. Using a hand blender, the peels were pureed until a fluid paste was formed.

Production of the plastic:

  1. 25ml of banana paste was placed in each 50ml beaker.
  2. 3ml of HCl was added and the mixture was mixed using a glass stirring rod.
  3. 2ml of propan-1, 2, 3-triol was added to each beaker. The mixture was stirred again.
  4. 3ml NaOH was added and the mixture was stirred once more.
  5. The mixture was poured into a petri dish and put in the oven at 130°C. It was baked for half an hour.

Materials and Safety Precautions:

All measurements were made as precisely as possible. For safety precautions, surgical gloves were worn throughout the experiment. The experiment was conducted at a labaratory in the Koc High School and the following equipment was used:

  • Glass pipette
  • Beakers
  • Bunsen Burner
  • Glass stirring rod
  • Oven
  • Petri dish
  • Gauze pad
  • Spring scale

STRENGTH TEST: The strength of the plastic was determined by applying a 4N pulling force on the plastic from the opposite sides and determining whether or not the plastic broke.

The thickness of the plastic was determined by using a ruler. The shelf life(decay) was assesed by visual inspection on a daily basis (The darkening of the plastic suggested decay). All qualitative and quantitative data was recorded.

Trial 1: Banana peels boiled and blended, the boiling water was not removed.

Qualitative Data (For the Experimental Group which contained 0,1M HCl and NaOH):

  • Plastic has formed, however it is extremely fragile.
  • The layer of plastic is very thin (the thickness cannot be measured).
  • There is less mixture than the amount that was put into the dish.
  • The plastic started to decay after 1 day.

Qualitative Data (For the Experimental Group which contained 0,5M HCl and NaOH):

  • No plastic was formed.
  • The mixture formed started to decay after 1 day.

 

Trial 2: Banana peels boiled and blended, the boiling water was removed.

Qualitative Data (For both Experimental Groups which contained 0,5M or 0,1M HCl and NaOH):

  • Plastic has formed, and it has passed the strength test. It is much thicker than trial 1. However, the plastic has started to decay after 3 days. It has acquired a darker color and a sharp scent. It has also lost its strength and has become much more fragile.

 

Trial 3: Banana peels were dipped in 0.5% Na2S2O5 solution prior to the boiling and blending process, the boiling water was removed and 20ml of the banana peel paste was used.

Qualitative Data (For both Experimental Groups which contained 0,5M or 0,1M HCl and NaOH):

  • Plastic has formed, however it is extremely fragile.
  • The layer of plastic is very thin. The 20ml of banana paste seems to have not been enough for the plastic to be thicker (the thickness cannot be measured).

 

Trial 4: Banana peels were dipped in 0.5% Na2S2O5 solution prior to the boiling and blending process, the boiling water was removed and 25ml of the banana peel paste was used.

Qualitative Data (For both Experimental Groups which contained 0,5M or 0,1M HCl and NaOH):

  • Plastic has formed, and it has passed the strength test. It is much thicker than trial 1 and 3. It has not shown any signs of decay for 30 days and counting. No change in strength has been recorded as well.

Quantitative Data (For All Trials):

 

 

 

 

 

 

 

Trends Noticed:

  • When the amount of banana peel paste used decreases, the plastic formed is too thin to measure.  25ml is the optimum amount of banana paste used.
  • When the plastic formed is very thin, its strength decreases as well.
  • When the banana peel is not dipped in 0.5% Na2S2O5, it starts to decay within 3 days.

It was also determined that the plastic formed in Trial 4...

  • Did not conduct electricity by covering a copper wire with the plastic and inserting it into a simple circuit. The electricity ran through the wire but not through the plastic.
  • Can be used in the production of cosmetic prosthetics for thumbs by baking it in a mold. (This mold was specially made by me using clay.)

In this project, I conducted 12 pilot experiments in order to establish the effects of placing the banana peels in 0.5% Na2S2O5 solution, using different concentrations of HCl and NaOH, using different amounts of banana paste, on the quality of the plastic produced. Based on the results of the 12 pilot experiments, 2 experiments were selected and were repeated four times. Several trends were recorded as a result of these pilot experiments. These trends were:

  • When the amount of banana peel paste used decreases, the plastic formed is too thin to measure.  25ml is the optimum amount of banana paste used.
  • When the plastic formed is very thin, its strength decreases as well.
  • When the banana peel is not dipped in 0.5% Na2S2O5, it starts to decay within 3 days.

These results supported my hypothesis, meaning that I succeeded and manufactured bio-plastic from banana peels. The reason why I was able to do so was because fruits rich with starch are preferred in the making of bio-plastic and the banana peel is rich with starch. The chemistry behind this is that starch consists of two types of polymer chains, called amylose and amylopectin, made up of adjoined glucose molecules. The HCl used in the procedure hydrolyzes amylopectin and prevents it from making hydrogen bonds with the amylose polymer chain and forming rows of polymer chains, acquiring a crystalline structure.

In the results section of my project report, the results from 4 of the 12 pilot experiments I conducted are shown. This is because these first 3 pilot experiments showed in the result section allowed me to notice the trends identified above and allowed me to improve the method I designed, in order to conduct the 4th pilot shown in the result section. Trial 4 shows the results of the 11th and 12th pilots I conducted – the trials which were selected and repeated four times. The repeated trials’ results are not shown in the “Results” section because they were done simply to make sure the success of the experiments was not accidental (and it was not accidential).

I also determined that the plastic formed in the 11th and 12th pilot experiments did not conduct electricity by covering a copper wire with the plastic and inserting it into a simple circuit. The electricity ran through the wire but not through the plastic.

Of course no experiment is perfect and there is always room for improvement. For example, the experiments conducted on the bananas were not all done at the same time and the bananas used were not purchased on the same day even though they were purchased from the same bazaar and at the same color index. This is a limitation which could be improved by conducting all 12 pilots at the same time, on the same batch of banana peels.

All my results inspired me to ask this question: Where can this plastic be used? The health industry, schools, construction sites... The list goes on and on.

References:

  • Phatcharaporn Wachirasiri, Siripan Julakarangka, and Sorada Wanlapa. "The effects of banana peel preparations on the properties of banana peel dietary fibre concentrate." Songklanakarin Journal of Science and Technology. 2008.
  • Commonwealth Scientific and Industrial Research Organization (CSIRO). “Banana ripening guide.”  Technical Bulletin 3. 1972
  • Kolade Joseph and O. C. Aworth. "Post-harvest treatment of wild mango (Irvingia gabonensis) for improved shelf life." Food Chemistry. 1991.
  • Erik Lokensgard. Industrial Plastics: Theory and Applications. 5th Edition. 2009. Pages 94-105.
  • Maria Paulina Forero. "Storage Life Enhancement of Avocado Fruits." 2007.
  • Miraç Yılmaz and Yavuz Beyatlı. "Bio-plastic: Poli-β-Hidroksibütirat (PHB)." Orlab Online Microbiology Magazine. 2003.
  • Aslihan Arikan. "Bio-plastics." Packaging Bulletin. 2009.
  • Kübra Tütüncü and Prof. Dr. Veli Deniz. "Which One Is More Green, Which One Is More Nature-friendly?" Recycling Magazine. 2008.

 

Acknowledgements:

I would like to thank my chemistry teacher Sibel Altay and my biology teacher Songül Genç at the end of my project report. Both my teachers gave me access to laboratories in which I was able to conduct my experiments, using the equipment in the laboratories. I would also like to thank my ceramics teacher for allowing me to use her workshop and clay to make a model for my prosthetic thumb. Lastly, I would like to thank my family for their everlasting support and patience throughout this stressful time. Other than these, the whole project was done by myself.

During the project, I did not use any specialized equipment. I was given acces to use the laboratories in Koc High School and the Istanbul Science and Art Center For Gifted Students.

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