Plant-Based Products for Sustainability (Edexcel International A Level Biology): Revision Note

Substituting Oil-Based Products

• Sustainability refers to the use of resources in such a way that the requirements of the current generation are met without depleting these resources for future generations

• This requires the use of renewable resources - which can be used without the resource running out

  • An example would be solar energy - it will not run out in our lifetime as the sun will continue to shine every day for several billion more years

• Fossil fuels are an example of a non-renewable resource, as they could potentially run out if we use them too fast (since it takes millions of years for fossil fuels to form)

• Sustainable practices are those that minimise the damage done to the environment and its resources, to ensure that there will be something left for the next generation

  • An example would be replanting trees after logging

• Unsustainable practices are limited by a finite supply of resources

  • An example is the use of fossil fuels to make oil-based plastics

Plant fibres and sustainability

• Using plant fibres to make products such as ropes and fabric is more sustainable than using oil-based plastics

• Less fossil fuels are used and plants can be replanted for the next generation

• Plant fibres are biodegradable, unlike most oil-based plastics, which means the products made from these fibres can be broken down by microbes to minimise environmental pollution

• Extracting and processing oil is an expensive and difficult procedure compared to growing and processing plants, making plant-based products easier and cheaper to produce in developing countries

• However, the ropes made from plant fibres are typically not as strong as plastic ones

Starch and sustainability

• Plants store excess sugars as starch in their cells

• Starch can be used to make bioplastics which is more sustainable than making oil-based plastics

• It does not require as much fossil fuels to be burned to produce them and the crop plants can be replanted (renewable resource)

• Starch can also be used to make bioethanol, which can be used as a fuel for vehicles

• Using starch to produce biofuels is more sustainable than producing them from oil

Bioplastics

• Bioplastics are made from biological polymers e.g. starch and cellulose

• There are multiple benefits to using bioplastics as a suitable replacement of traditional plastics

  • Sustainability: starch and cellulose are plant based materials which can be replaced at a sustainable rate; unlike oil based plastics which are made from non-renewable fossil fuels

  • Biodegradable: since bioplastics are made from biological material, it can be broken down by microorganisms; unlike oil based plastics which is generally not biodegradable

    • This could potentially decrease the amount of plastic pollution that is currently having a detrimental effect on the environment

• Currently, there are several different types of bioplastics in use

  • Cellulose-based plastics are made from wood pulp and are mainly used as food wrappers (e.g. cellophane)

  • Thermoplastic starch which is a mixture of starch and other compounds, such as gelatine, to create a smooth and shiny plastic

    • This has been used with great success in the pharmaceutical industry to create easy to swallow capsules that contain drugs

  • Polylactic acid (PLA) produced from maize or sugar cane and have properties similar to polyethene

  • Poly-3-hydroxybutyrate (PHB) which is made from products of the sugar industry and used in ropes, bank notes and car parts

• Bioplastics can be burned once they are no longer used to avoid the production of methane during decomposition

  • Methane is a much more potent greenhouse gas than the carbon dioxide released during combustion

  • An added advantage to burning is that the energy released can be utilised to generate electricity and produce more bioplastics

• There are several challenges concerning the use of bioplastic

  • They do not always have the same useful properties as oil based plastics

  • Bioplastics are more expensive than oil based plastics

  • Using limited food crops to produce plastics (which do not feed the hungry) is a controversial subject in some parts of the world