Biodegradable Plastics from Cassava Starch
EWB-UK Workshop Guide Make your own Bio-Plastic Description A workshop focusing on the problems of plastics made by fossil fuels and a look into making your own bio-plastic. At a glance Total time: 1 hour Learning Styles: Visual, auditory, practical, participatory, teamwork Objectives: To learn about the challenges facing fossil fuel plastics and how to make your own bio-plastic Audience: Anyone Max/Min no. of participants: N/A (Dependant on amount of materials) Timetable Time| Activity| Equipment| 5 minutes| Welcome | | 15 minutes| Introduction| | 30 minutes| Practical| See material and tools list| minutes| Closing| Sign-ups for email| Materials Per batch of bio plastic (Ideally per person): * 100g of potato * 300cm3 of distilled water * 25ml of water * 3cm3 of hydrochloric acid or vinegar * 2ml pure glycerol * 3cm3 sodium hydroxide * Food colouring Tools * Grater * Pestle & Mortar * Strainer * Beaker/Jars * Measuring cylinder/jug * Weighing scales * Indicator Paper * Portable hob Preparation * Prepare equipment, tools and materials * Prepare sign-up sheets for new members Room requirements * An area suitable for doing hands on work and mixing liquids * Kitchen for source of heat.
Use portable hobs if this isn’t possible Welcome (5 minutes) Introduce yourself: * Your Name * Position/Job/Organisation * Your role in the workshop * Relevant experience to the workshop (University, projects, work etc. ) Explain the learning objectives of the workshop to the audience: The purpose of the workshop is for participants to learn about the problems surrounding plastics made by fossil fuels. This is done in the introduction presentation. Afterwards, participants get to make their own bio-plastic in a hands-on practical. Participants will be able to take the plastic home with them at the end of the workshop.
Introduction (15 Minutes) A presentation on the challenges facing fossil fuel plastics. Plastic is the common term used for a variety of synthetic or semi synthetic materials used in manufacturing. Plastics are traditionally made from polymers and normally created from petroleum products. Plastics have become so popular to do their advantageous features. They are malleable, versatile and very cheap compared to other materials. The problem with plastics is their dependency on petroleum, i. e. oil. Currently about 8% of the world’s oil is used to make plastics.
This is compared to 4% for raw materials and 4% for energy. The other major problem is waste; currently about 35% of litter is a plastic based product. Bio plastic currently offers one solution to the problem. Bio plastic is formed from renewable biomass sources such as vegetable oil or corn starch. Like conventional plastics; all bio plastics are biodegradable given enough time. However also like conventional plastics; some bio plastics take so long to degrade they are considered non-biodegradable. A significant number of bio plastics will only biodegrade given very specific conditions.
Most people assume the term bio plastic means it will biodegrade; it actually refers to its biomass source. This leads to the advantages and disadvantages of bio plastics: Advantages: They are made from plant based sources so don’t use any fossil fuels. Disadvantages: The majority of bio plastic manufacturing plants use oil or fossil fuels to power them. Currently there is still a need for fossil fuels for a large scale plant. When growing resources for bio plastic it can create large scale mono-cropping problems. This can lead to the destruction of areas like the rain forest.
The solution is to produce bio plastic on a small scale with biodiversity in mind. The crop should be sustainable and the process should renewably powered. One method for doing this is to produce bio plastic from locally grown potatoes. The chemistry bit: Potato starch is made from two carbohydrate polymers, amylose and amylopectin. To make bio plastic the amylopectin needs to be broken down. This way the starch can be plasticised. For a more technical audience you may choose to extend this section and continue further with the science behind the process. Further reading will be required however.
Practical (30 minutes) The step by step instructions for making the bio-plastic For making bio-plastic highly accurate measurements are not required 1. Grate about 100g of potato into a pestle & mortar 2. Add 100cm3 distilled water to the potato and grind in a pestle and mortar 3. Strain the liquid off, and repeat adding distilled water, grinding and straining twice more. 4. Leave to settle for 5 minutes 5. Strain the water off, leaving the starch behind. 6. Put 25ml water into a beaker and add 5g starch (10g wet) and 3cm3 hydrochloric acid (Use vinegar if you can’t get hold of it) and 2ml pure glycerol. 7.
Bring to the boil for 15 minutes, ensuring it doesn’t boil dry 8. Using indicator paper and sodium hydroxide to neutralise the solution (probably about 3cm3). 9. Add a few drops of colouring to the mixture and mix in. 10. Pour the mixture out, and mould into your preferred shape. 11. Leave to dry out and set. Once the mixture sets the plastic is complete. The amount of glycerol used affects the stiffness of the mixture. The less glycerol used the stiffer the plastic will be. Closing (5 minutes) Final few words: * Announce next event or meeting * Distribute sign up lists (If applicable) * Open the floor to questions