Biodegradable plant-based plastics

What are biodegradable plant-based plastics?

Biodegradable plant-based plastics are made from plant feedstock such as corn starch and vegetable fats and oils. The theory underpinning the use of plant-based materials is that if plastics are made from kinder materials in the first instance they will break down more easily. They are often referred to as bioplastics however there are two types of bioplastics:

  • Bioplastics (often mixed with conventional fossil fuel polymer to add strength), which will not biodegrade in the open environment. These bioplastics have no environmental advantage over conventional plastics made from fossil fuels. 
  • Bioplastics that do biodegrade in the open environment and may be compostable under certain conditions.


 

Advantages of bioplastics

Although not all plant-based plastics biodegrade, many do and some are compostable under certain conditions. They are also 'renewable', in that the plants from which the feedstock is derived can be grown quite quickly.  

Issues relating to bioplastics

As they are made from foods such as corn they take agricultural land away from food production. To achieve the 'renewable’ turnaround they are intensively farmed. Farm machinery consumes fossil fuels as they sow and harvest the crop. Fertilisers and pesticides, both of which consume fossil fuels in their manufacture, are often applied in industrial quantities. Sometimes genetically modified crops are used, thought by some although not others, to be environmentally damaging.  

Composting often takes place in industrial composting facilities which require them to turn into CO2 in 180 days. They do not make compost or indeed anything useful for the soil, only CO2 which is a potent greenhouse gas.  Some biodegradable plant-based plastics produce methane if biodegraded in landfill.

Bioplastics and recycling

Bioplastics can be recycled with other bioplastics however the process by which they are made, makes them incompatible with fossil fuel plastics. As a result they cannot be recycled together.  

Bioplastics compared with fossil fuel plastics

Bioplastics are more expensive to produce and therefore to buy than ‘traditional’ plastics derived from fossil fuels. They are also heavier and therefore more fuel hungry to transport and they are unsuitable for some applications. Bio-based polymers do not have the same properties as conventional  plastics in some key areas relating to oxygen and water barrier properties, important for food preservation.

It is, therefore, questionable if it makes sense to use food crops to produce bioplastics while aeroplanes and motorcars still use fuel, as plastics are made from a by-product of fuel extraction that used to be wasted. The same amount of oil would still be extracted even if plastics did not exist.

Oxo-biodegradable plastics >