Written by Randolph S. Jeremiah, Environmental Protection Society, Malaysia.
The plastic bag was only introduced in the 1970’s but its use has expanded due to its high versatility. The plastic bag is an efficient way to carry goods. It is hygienic, light in weight yet considerably strong. Plastic bags can be easily produced and made into different forms, shapes, sizes and colours. Plastic bags are made from both natural gas and petroleum. In total, the production of plastics accounts for only 4% of world oil consumption2. An even less amount of this is used for the production of plastic bags. In terms of its energy, it takes 0.48 megajoules (MJ) to produce one high-density polyethene (HDPE) plastic bag3.
Taking into account its energy consumption, about 1 square meter of natural land is required to absorb the greenhouse gases generated from the production of about 14 HDPE bags. Each year, over 500 billion to 1 trillion plastic bags are consumed worldwide. We would need to set aside a natural area almost the size of the state of Sabah just to absorb the greenhouse gases generated from the production of all these plastic bags. Although plastics can be recycled and reused over again, the facilities that are required to sort and process the various types of plastics separately are neither available nor economical.
As such, the recycling of plastic bags is still very low and not yet a practical option in Malaysia. Even the use of paper bags is not a better environmental solution. In fact, the production of paper bags uses 60% more resources and energy that plastic bags and produces 80% more solid waste5. The impact of plastic bags, however, goes beyond the resources and energy consumed during its production. Plastic bags that are disposed of in garbage end up in dumps and landfills. It can take up to 1000 years for plastic bags to degrade and breakdown completely. Plastic bags that are improperly disposed of can clog waterways and contribute towards floods.
Bags that make it to the ocean are harmful to marine life. Turtles often choke on plastic bags after mistaking the floating debris for food. In addition, plastic bag litter incurs an often less visible but high clean-up and disposal cost which inflates its overall Footprint. It may be difficult to completely remove plastic bags usage from our life and reduce its Footprint. However, we can manage this very useful product by following a common rule of reducing, reusing and if possible, recycling. Reduce the usage of plastic bags by making a habit of carrying a more durable bag when shopping. This bag could be made out of stronger plastic material or can be a simple cotton bag. Using a reusable bag over a year consumes 10 times less energy than using disposable plastic bags.
Today, we hear a lot of new innovative inventions, people trying all kind of possible materials to ensure a plastic bag is biodegradable or reusable.
Generally, a simple information on how to know if one is Biodegradable. Biodegradable/degradable plastics can be made from many different sources and materials as listed below:
- Starch-based polymers:- Thermoplastic starch based polymers made with at least 90% starch from renewable resources such as corn, potato, tapioca or wheat.
- Polyesters (Bacteria based polymers):– Polyesters manufactured from hydrocarbons (oil or gas). All polyesters degrade eventually, with degradation rates ranging from weeks for aliphatic polyesters(e.g. polyhydroxyalkanoates). Bacteria are an additional treatment used to create a different type of biodegradable polymer.
- Starch or Polyester blends:– Mixed with thermoplastic starch with polyesters made from hydrocarbons.
- Oxo-biodegradable polymers:– These polymers undergo controlled degradation through the incorporation of ‘prodegradant’ additive ( an additive that can trigger and accelerate the degradation process). This polymer undergo accelerated oxidative define degradation initiated by natural daylight, heat and/or mechanical stress, and embrittle in the environment and erode under the influence of weathering.
- Photodegradable polymers:- These polymers are those that break down through the action of ultraviolet(UV) light, which degrades the chemical bond or link in the polymer or chemical structure of the plastic. This process can be assisted by the presence of UV-sensitive additives in the polymer.
- Water-soluble polymers:– These polymers are those that dissolve in water within a designated temperature range and then biodegrade in contact with microorganisms.