It shouldn’t
be a surprise that there is often confusion when talking about bio-plastics, In
this post we will clarify some terms and also shed some light on the cons of bio-plastics.
Let’s
start by listing some of the different types of plastic:
- Degradable:
All plastic is degradable, even traditional plastic, however not all degrade at
the same speed.
Some
additives to traditional plastics make them degrade more quickly.
Photodegradable plastic breaks down more readily in sunlight; oxo-degradable
plastic disintegrates more quickly when exposed to heat and light.
- Biodegradable:
Biodegradable plastic can be broken down completely into water, carbon dioxide
and compost by microorganisms under the right conditions.
- Compostable:
Compostable plastic will biodegrade in a compost site. Microorganisms break it
down into carbon dioxide, water, inorganic compounds and biomass at the same
rate as other organic materials in the compost pile, leaving no toxic residue.
If we turn our focus now to
bio-plastics, we can identify two main types:
- PLA (polyactic
acid): Typically made from the sugars in corn or potato starch, or sugarcane.
It is biodegradable, carbon-neutral and edible.
PLA can
look and behave like polyethylene (used in plastic films, packing and bottles),
polystyrene (plastic cutlery) or polypropylene (packaging, textiles).
- PHA (polyhydroxyalkanoate):
Made by microorganisms that produce plastic from organic materials. The
microbes are deprived of nutrients like nitrogen or oxygen, but given high
levels of carbon.
They
produce PHA as carbon reserves, which they store in granules until they have
more of the other nutrients they need to grow and reproduce. Companies can then
harvest the microbe-made plastic.
Because
it is biodegradable and will not harm living tissue, PHA is often used for
medical applications such as sutures, slings, bone plates and skin substitutes.
Now that
we have clarified some of the different types of bio-plastic, let’s address the
controversy.
While bio-plastics are generally considered to be more eco-friendly than traditional
plastics this isn’t necessarily true when the materials’ life cycles were taken
into consideration.
Bio-plastics production results in greater amounts of pollutants, due to the fertilisers and
pesticides used in growing the crops and the chemical processing needed to turn
organic material into plastic.
While the
biodegradability of bio-plastics is an advantage, most need high temperature
industrial composting facilities to break down and very few cities have the
infrastructure needed to deal with them.; as a result, bio-plastics often end up
in landfills where, deprived of oxygen, they may release methane, a greenhouse
gas 23 times more potent than carbon dioxide.
When bio-plastics are not discarded properly, they can contaminate batches of
recycled plastic and harm recycling infrastructure. If bio-plastic contaminates
recycled plastic, the entire lot could be rejected and end up in a landfill. So
separate recycling streams are necessary to be able to properly discard bio-plastics.
Another
point is the fact that the land required for bio-plastics competes with food
production because the crops that produce bio-plastics can also be used to feed
people. In addition, the water and petroleum used to run the farm has a greater
carbon footprint.
Finally, at
the moment bio-plastics are still relatively expensive, 20 to 50 percent more
costly than fossil fuel based plastics because of the complex process used to
convert corn or sugarcane into the building blocks for the final product.
In
summary, right now, it’s hard to claim that bio-plastics are more
environmentally friendly than traditional plastics when all aspects of their
life cycle are considered: land use, pesticides and herbicides, energy
consumption, water use, greenhouse gas and methane emissions, biodegradability, "recyclability" and more, but as researchers around the world work to develop
greener varieties and more efficient production processes, bio-plastics do hold
promise to help lessen plastic pollution and reduce our carbon footprint.
