Plastic bags are under the spotlight at the moment... they are endangering our oceans and the wildlife that live in them, littering our planet, they take hundreds of years to break down, and when they do, it is into small micro-plastics. Micro-plastics are contaminating our environment, finding their way into the fish and animals that we eat, and therefore, finding it's way into our own stomachs and bodies. The ongoing effects of this plastic exposure, and the chemicals they introduce into our bodies, is yet to be determined, but it is unlikely to be good news...
Every piece of plastic that you have ever used, opened or thrown away still remains somewhere in the world today.
Why do we use plastics?
Due to their low cost, ease of manufacture, versatility, and imperviousness to water, plastics are used in a multitude of different products from paper clips to spacecraft (3). Since their discovery in the 1800's, and increasing use in the 1900's (2) they have been replacing the use of traditionally used natural materials such as wood, stone, leather, metal, glass, ceramics, horn and bone (3).
What about recycling?
Plastics are carbon-based polymers (long-chain molecules that repeat their structures over and over), and most plastics are made from petroleum (oil). Plastics can take over 400 years to biodegrade. It varies on the type of plastic - plastic bottles taking about 450 years, fishing line about 600 years, and plastic bags about 20 years (1).
While some plastics are recycled, this is just a small percentage of the plastic that is produced, the rest ending up in landfill, burned (releasing toxic chemicals into the environment), or loose in the environment. While recycling can help reduce the amount of new plastics produced, plastics can only be recycled a finite number of times, and there is still a mass of unwanted material that takes decades to degrade at the end of the process(1), and don't forget the energy used in collecting and recycling the plastic, as well as any chemicals used, and other waste produced from the process...so recycling, while it helps, is definitely not the full solution.
The "ideal" scenario is to stop using plastic altogether, after all, humans managed quite well without it prior to its widespread introduction in the 1900's, but that is an unlikely and unrealistic hope. However, many environmentally-minded people are starting to swap-out plastic in many situations - such as taking their own reusable and natural-fibre bags to the shops, choosing glass or stainless steel containers over plastic, and using stainless steel lunch boxes.
Types of "Environmentally friendly" plastics:
There are three broad categories(4):
Bioplastics
Bioplastic (also called bio-based plastic) simply refers to plastic made from renewable biomass sources, including vegetable fats and oils, corn starch, straw, woodchips, and food waste (5). Bioplastic can be made from agricultural by-products, and also from used plastic containers and bottles using microorganisms.
Bioplastic can be made either by extracting sugar from plants like corn and sugarcane, which is then converted into polylactic acids (PLAs), or it can be made from polyhydroxyalkanoates (PHAs) which are engineered from microorganisms.
PLA plastic is commonly used in food packaging, wheras PHA is often used in medical devices like sutures and cardiovascular patches.
PLA is the cheapest and most common source of bioplastic, and is often used in plastic bottles, utensils and textiles.
It is estimated that about eight percent of the world’s oil is used to make plastic. It is argued that is we use bioplastics instead of oil-based plastics, thereby reducing that amount of oil used in making plastic, the end result is more environmentally friendly.
The argument goes that when a discarded plastic item degrades, and in the process releases carbon into the environment, if that carbon had come from a plant source (and therefore recently removed from the environment during the growing of the plant) instead of from oil (which had previously been trapped underground), then overall less carbon is released into the environment, that is, no net increase in carbon dioxide gas is produced (4).
While another plus for bioplastics is that some of them are compostable and will decay into natural materials that blend harmlessly with soil, the time taken to break down varies greatly. For some bioplastics it will be weeks - such as bioplastics containing cornstarch molecules which slowly absorb water and swell, causing them to break apart into smaller fragments that can be digested by bacteria. Unfortunately not all bioplastics will compost easily or completely, and will leave toxic residues or small plastic fragments behind (4). Others will break down only if subjected to high temperatures (requiring industrial scale composters or digesters), or in biologically active landfills (also known as bioreactor landfills)(4). Therefore a lot of the bioplastics ending up in landfill, put into a home composting heap, or that otherwise escape into the environment will, like oil-based plastics, not rapidly break down.
Other arguments for using bioplastics include:
It's renewable nature
It can be grown all over the world (unlike oil which is concentrated into certain regions)
It can support the rural economy
Other downfalls of bioplastics include:
Pollution from fertilisers, pesticides and herbicides used in growing the plants used to make them
Land being diverted away from food production
Discarded bioplastics will either be:
Sent to a landfill facility
Recycled (as many oil-based plastics are)
Sent to an "industrial composting" or biologically active landfill site
Burned
Let loose into the environment, all too often ending up in our oceans.
Bioplastics that end up in our ocean, just like oil-based plastics, endanger our marine life, will break down into micro-plastics, and will last for decades.
Industrial Composting: The bioplastic is heated to a temperature high enough to allow microbes to break it down. These bioplastics won't degrade fast enough unless this intense heat is first applied. The availability of Industrial Composting can also be an issue.
Biodegradable Plastics
Biodegradable plastics, often in the form of plastic bags, typically sport environmentally-friendly sounding labels such as "photodegradable", "oxydegradable", or "biodegradable".
These plastics are made of normal (oil based) plastics, but contain additives that cause them to decay more rapidly in the presence of light and oxygen (4). When they break down, they may leave behind a toxic residue that can make them unsuitable for composting. When in landfill or in the ocean, they may not break down due to the conditions (lack of light, temperature), and if they do break down, it may be into tiny plastic fragments.
Recycled Plastics
The recycling of old plastic materials into new ones is another approach to the plastics problem.
There are two approaches here: products made entirely from recycled plastic, and products that incorporate recycled plastics as a part of their structure.
Plastics can only be recycled a finite number of times. Recycled plastic is generally used to make lower-grade items than the original. For example, plastic bottles are not recycled to make new plastic bottle, but items like plastic benches and fence posts. Furthermore, recycled plastics can not be assumed to be better for the environment unless you know that there has been a net saving in energy and water use, a net reduction in greenhouse gas emissions, or some other overall benefit (4). It can take a lot of energy to collect and recycle plastic, and there will be chemicals used and waste materials produced in the process.
Every piece of plastic that you have ever used, opened or thrown away still remains somewhere in the world today.
Why do we use plastics?
Due to their low cost, ease of manufacture, versatility, and imperviousness to water, plastics are used in a multitude of different products from paper clips to spacecraft (3). Since their discovery in the 1800's, and increasing use in the 1900's (2) they have been replacing the use of traditionally used natural materials such as wood, stone, leather, metal, glass, ceramics, horn and bone (3).
What about recycling?
Plastics are carbon-based polymers (long-chain molecules that repeat their structures over and over), and most plastics are made from petroleum (oil). Plastics can take over 400 years to biodegrade. It varies on the type of plastic - plastic bottles taking about 450 years, fishing line about 600 years, and plastic bags about 20 years (1).
While some plastics are recycled, this is just a small percentage of the plastic that is produced, the rest ending up in landfill, burned (releasing toxic chemicals into the environment), or loose in the environment. While recycling can help reduce the amount of new plastics produced, plastics can only be recycled a finite number of times, and there is still a mass of unwanted material that takes decades to degrade at the end of the process(1), and don't forget the energy used in collecting and recycling the plastic, as well as any chemicals used, and other waste produced from the process...so recycling, while it helps, is definitely not the full solution.
The "ideal" scenario is to stop using plastic altogether, after all, humans managed quite well without it prior to its widespread introduction in the 1900's, but that is an unlikely and unrealistic hope. However, many environmentally-minded people are starting to swap-out plastic in many situations - such as taking their own reusable and natural-fibre bags to the shops, choosing glass or stainless steel containers over plastic, and using stainless steel lunch boxes.
Types of "Environmentally friendly" plastics:
There are three broad categories(4):
- Bioplastics - plastics which are made from natural, renewable materials
- Biodegradable plastics - made from traditional petrochemicals, but which are engineered to break down more quickly
- Eco/recycled plastics - plastics made using recycled plastic materials, rather than raw petrochemicals (oil)
Bioplastics
Bioplastic (also called bio-based plastic) simply refers to plastic made from renewable biomass sources, including vegetable fats and oils, corn starch, straw, woodchips, and food waste (5). Bioplastic can be made from agricultural by-products, and also from used plastic containers and bottles using microorganisms.
Bioplastic can be made either by extracting sugar from plants like corn and sugarcane, which is then converted into polylactic acids (PLAs), or it can be made from polyhydroxyalkanoates (PHAs) which are engineered from microorganisms.
PLA plastic is commonly used in food packaging, wheras PHA is often used in medical devices like sutures and cardiovascular patches.
PLA is the cheapest and most common source of bioplastic, and is often used in plastic bottles, utensils and textiles.
It is estimated that about eight percent of the world’s oil is used to make plastic. It is argued that is we use bioplastics instead of oil-based plastics, thereby reducing that amount of oil used in making plastic, the end result is more environmentally friendly.
The argument goes that when a discarded plastic item degrades, and in the process releases carbon into the environment, if that carbon had come from a plant source (and therefore recently removed from the environment during the growing of the plant) instead of from oil (which had previously been trapped underground), then overall less carbon is released into the environment, that is, no net increase in carbon dioxide gas is produced (4).
While another plus for bioplastics is that some of them are compostable and will decay into natural materials that blend harmlessly with soil, the time taken to break down varies greatly. For some bioplastics it will be weeks - such as bioplastics containing cornstarch molecules which slowly absorb water and swell, causing them to break apart into smaller fragments that can be digested by bacteria. Unfortunately not all bioplastics will compost easily or completely, and will leave toxic residues or small plastic fragments behind (4). Others will break down only if subjected to high temperatures (requiring industrial scale composters or digesters), or in biologically active landfills (also known as bioreactor landfills)(4). Therefore a lot of the bioplastics ending up in landfill, put into a home composting heap, or that otherwise escape into the environment will, like oil-based plastics, not rapidly break down.
Other arguments for using bioplastics include:
It's renewable nature
It can be grown all over the world (unlike oil which is concentrated into certain regions)
It can support the rural economy
Other downfalls of bioplastics include:
Pollution from fertilisers, pesticides and herbicides used in growing the plants used to make them
Land being diverted away from food production
Discarded bioplastics will either be:
Sent to a landfill facility
Recycled (as many oil-based plastics are)
Sent to an "industrial composting" or biologically active landfill site
Burned
Let loose into the environment, all too often ending up in our oceans.
Bioplastics that end up in our ocean, just like oil-based plastics, endanger our marine life, will break down into micro-plastics, and will last for decades.
Industrial Composting: The bioplastic is heated to a temperature high enough to allow microbes to break it down. These bioplastics won't degrade fast enough unless this intense heat is first applied. The availability of Industrial Composting can also be an issue.
Biodegradable Plastics
Biodegradable plastics, often in the form of plastic bags, typically sport environmentally-friendly sounding labels such as "photodegradable", "oxydegradable", or "biodegradable".
These plastics are made of normal (oil based) plastics, but contain additives that cause them to decay more rapidly in the presence of light and oxygen (4). When they break down, they may leave behind a toxic residue that can make them unsuitable for composting. When in landfill or in the ocean, they may not break down due to the conditions (lack of light, temperature), and if they do break down, it may be into tiny plastic fragments.
Recycled Plastics
The recycling of old plastic materials into new ones is another approach to the plastics problem.
There are two approaches here: products made entirely from recycled plastic, and products that incorporate recycled plastics as a part of their structure.
Plastics can only be recycled a finite number of times. Recycled plastic is generally used to make lower-grade items than the original. For example, plastic bottles are not recycled to make new plastic bottle, but items like plastic benches and fence posts. Furthermore, recycled plastics can not be assumed to be better for the environment unless you know that there has been a net saving in energy and water use, a net reduction in greenhouse gas emissions, or some other overall benefit (4). It can take a lot of energy to collect and recycle plastic, and there will be chemicals used and waste materials produced in the process.
(1) The Telegraph - The stark truth about how long your plastic foot[print will last on the planet
(2) Wikipedia - Timeline of Plastic Development
(3) Wikipedia - Plastic
(4) Explain that stuff - Bioplastics and Biodegradable Plastics
(5) Wikipedia - Bioplastic
(6) National Geographic - plant based plastics