Most (almost all, actually) conventional plastics are made from petroleum – here’s a nice video on oil to plastics.
With petroleum being a perishable resource, a question that arises is: Can we make plastics from plants?
Yes, of course.
We have a dedicated industry sector for this, with a dedicated name – Bioplastics, which simply means plastics made from bio-sources (mainly plants).
The prominent plant sources for making bioplastics could include:
- Plant material rich in starch – Common examples include corn, potatoes, rice etc.
- Plant material rich in oil – Oil seeds, especially palm, soy, rapeseed, castor oil etc.
- Plant material rich in cellulose – These typically comprise agricultural waste and forest waste, and includes a vast range – from sunflower stalks in the field to saw dust from the processing of forest wood.
On reading the above list, you might be tempted to think that pretty much any biomass could be used to make bioplastics.
In theory, this is true. While, through a variety of processes, most tyoes biomass can be processed to make one or the other type of plastic, it is more economical to make certain types of bioplastics with specific types of biomass:
- Starch-based biodegradable products – Thin, flexible films, cups and cutlery items are usually made from starch based biomass feedstock. These usually are biodegradable.
- Starch-based non-biodegradable products – Starch based biomass such as sugarcane are also used to make chemicals that replace some chemicals derived from petroleum. A prominent example here is the monoethylene glycol (MEG) made from sugarcane – this can replace the petro-derived MEG sued to make PET bottles for brands such as Coca Cola. Because the other component of the PET bottle (TPA or terephthalic acid) is derived from petroleum and is not biodegradable), this combination is not biodegradable, but have the benefit of being made from renewable sources.
- Engineering plastics from plant/vegetable oils – Engineering plastics such as Polyamide (nylon) and Polyurethane that are used in a variety of durable applications. These are usually made with vegetable oils such as castor oil as their starting points. These are not biodegradable, but they present the benefit of reduced carbon footprint as the feedstock is from renewable sources and not from petroleum.
- Cellulose-based bioplastics – Cellulose is not a very common starting point for making bioplastics, though the cellophane that we have been using for a long time has been made from cellulose ever since the beginning. Cellulose-based bioplastics for other applications is in the beginning stages.
- Durable bioplastics – And then there are companies that are making durable bioplastic items using starch-based, lipid-based and/or cellulose based biomass feedstock. Similar to the above example, these are not usually not biodegradable, but usually have the business case of lowering the overall carbon footprint of the end-product.
In recent months, I have been involved in doing some market research of the bioplastics sector worldwide. What I find is not super-encouraging – as of 2016, bioplastics is a very small segment, contributing less than 1% to the world’s use of plastic, but there are some signals that this sector could grow much faster starting 2020, once some of the technical challenges have been ironed out and costs brought down to more affordable levels for large scale use.
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Are bioplastics a real substitute for conventional plastics – Link