Why Are Compostable Plastic Bags More Expensive To Manufacture Than Traditional Plastic Bags?

Although many people are looking to reduce their environmental footprint and choose plastic alternatives, the additional cost of such options can provide a barrier to purchasing these plastics. It’s important to understand why compostable plastic bags are more expensive and how this will help you to leave a smaller environmental impact long-term.

Compostable plastic bags are more expensive than traditional plastic due to the cost of raw materials being more expensive, less readily available and manufacturing processes costing more with smaller batches. Raw materials such as corn, potato and soy have costs associated with growing and farming as well as converting them into starches to be manufactured into compostable plastic. These additional costs are then combined with manufacturing processes that attempt to have reduced carbon, emissions, water and electricity costs. The current smaller batches that are manufactured cost more than mass quantities. The demand for compostable plastic always plays a role, as more widespread manufacturing will drop the cost down.

How Is Traditional Plastic Made?

Different types of plastics are used in everyday products from medication packaging and food packaging to toys, engineering and building products.

There are seven main types of plastics, with PET being the most common.

• Polyethylene terephthalate (PET) commonly used for soft drink and water bottles.
• high-density polyethylene (HDPE) commonly used for harder wearing applications like shampoo bottles.
• low-density polyethylene (LDPE) commonly used for softer applications like grocery bags and cling wrap.
• polyvinyl chloride (PVC) commonly used building construction applications like pipes. 
• polypropylene (PP) commonly used for bottles, toys and car parts.
• polystyrene (PS) used for packing, 
• and other resins.

You can learn more about the different types of plastics in this article.

Some of these are recyclable – either easily or with sophisticated processes. None are completely safe for the environment as they cannot be broken down in a composter or in landfill and they must be recycled to be reused again.

The Manufacturing Process Of Plastic

There are three main steps in the manufacturing of plastic:

1.       Raw materials such as crude oil, natural gas or plants are refined into ethane and propane. 
2.       These two resulting materials are treated with heat and ‘cracked’ which results in ethylene and propylene.
3.       These two materials are combined together to create different types of plastics.

The manufacturing process may slightly differ based on type of plastic and usage, with plastic often going through molding processes or having dyes inserted for its final product. A variety of manufacturing processes have been developed to cover a wide range of applications, types of plastics and part geometries.

The heating and cooling process can also produce plastics known as ‘thermoplastics’ which are able to repeat the heating and cooling process without degrading – heating softens them and they can be molded into any shape. This means they are able to be melted and recast/molded almost immediately more than once. 

Why Are Thermoplastics So Common?

The most common type of plastic is a thermoplastic, which goes through numerous melt and solidification cycles without a large amount of degradation. They are usually supplied in small pellets or sheets which can be heated and formed into the desired shape.

Common types of thermoplastics include:

• Acrylic
• Polyamide
• Polycarbonate
• Polyethylene
• Polypropylene
• Polyvinyl chloride (PVC)
• Acrylonitrile butadiene styrene
• Polyether ether ketone
• Polylactic acid.

These plastics are often found in toys such as LEGO® and sports equipment (acrylonitrile butadiene styrene), CDs and DVDs (polycarbonate), shampoo bottles (polyethylene).

How Is Compostable Plastic Made?

Compostable plastic is made from raw materials and manufactured to break back down into the natural environment through a home composter, industrial composting facility or worm farm. 

Compostable plastic is made through a simple process:

1. Gather the materials such as corn starch, cellulose, soy, potato and other similar materials containing starch. This could be through farming in the case of vegetables.
2. Extract the polylactic acid, sugar, starch.
3. Heat process.
4. Molding.
5. Curing or dye added.
6. Set the plastic.

This process and the raw materials makes the compostable plastic bags more expensive.

An Example Of A Compostable Plastic Process

Compostable plastic such as polylactic acid (PLA) is made typically from fermented food starch often from corn, sugarcane, sugar beet pulp or cassava and combined with lactic acid and cyclic di-ester lactide.

This means that a mixture is created to then be fermented and the starch extracted, which is the base material for compostable plastic.

The materials fermented and used for the production of PLA are chosen as they are carbohydrate sources that are then manufactured in a controlled environment and have the starch extracted. This is then mixed with enzymes or acid and heated to break down the starch into dextrose or corn sugar.

The following fermentation process produces L-Lactic acid which is the building block of PLA. 

The Benefits Of Compostable Plastic Manufacturing

The manufacturing process of such plastic is almost carbon neutral, doesn’t release toxic fumes, uses less energy than conventional plastic, generates fewer greenhouse gases and provides more jobs in rural areas.

What Are The Most Common Compostable Plastics?

The most commonly used compostable plastics are PLA and CPLA: polylactic acid and crystallized polylactic acid. These are often made from cornstarch with other vegetables which make them sustainable, compostable and renewable. CPLA is heat resistant and useful for food service items such as cutlery, takeaway food containers, coffee cup lids and soup containers.

CPLA is often not transparent but seen as white unless charcoal is added to create a black color. PLA is used for cold food service items such as cups, salad containers, deli posts, lids, bags (such as trash bags) and clear windows in sandwich boxes or bags and is transparent. 

PLA and CPLA are also recognized as non-toxic which allows them to be utilized in medical environments such as medical implants, orthopedic devices and drug delivery systems. You can find out more about PLA and CPLA compostable plastics in this article.

Is Compostable Plastic Really Worth The Cost?

Compostable plastic bags are more expensive to purchase, however, the long-term cost to the environment is lower than traditional plastic. For those who are looking to decrease their environmental impact and their contribution to landfill, compostable plastics are worth the additional monetary cost.

However, you need to make a decision before purchasing about how you will dispose of the product i.e. landfill or composter; whether the product is marked as landfill friendly; whether you can reuse the product and what other options are available to you. 

Compostable plastic is a great option as it contains no toxic compounds. Compostable plastics will break down (when in the right environment) and not emit or leave behind any toxic material. However, if you’re not disposing of your compostable plastic in the right environment then you should choose landfill-biodegradable so that the plastic has a chance of decomposing faster than traditional plastic. This, however, can leave behind some toxic compounds after decomposition.

Essentially, your choice of how you dispose of the plastic really plays the key factor in which plastic is best for the environment for you and your family..

What Can Be Done To Drop The Cost Of Manufacturing Eco-Friendly Plastic?

The simplest way to decrease the cost of manufacturing compostable plastic and other eco-friendly plastics is basically to increase interest and demand in the product. Like everything, demand often plays a role in the cost of manufacturing. Manufacturing larger quantities generally equals lower manufacturing costs.

To encourage the use of these plastics, it’s important for more people to become aware of the other options available, how to dispose of these and be aware of the environmental impact traditional plastic has on landfill and for wildlife.

It’s also important that resources are widely available which often relies on farming in rural areas (think corn, soy and potato as materials). The renewable aspects of these products do contribute to lowering manufacturing costs in terms of electricity and water usage.

Will Compostable Plastic Become More Popular?

Compostable plastics are becoming more popular as awareness of landfill contribution, wildlife risk and soil risks of traditional plastics increases across the globe. Whole businesses are shifting the way they develop plastics and the products they manufacture.

Each year, more and more compostable packaging options are introduced into markets across the globe, showing the increased interest in such alternatives. The current issues with the uptake or correct usage of compostable plastics are:

1. Understanding how to dispose of the product
2. Cost
3. Availability of a good number of products that are compostable to switch a whole lifestyle to bioplastics.

Conclusion

Compostable plastics are definitely increasing in demand and availability, providing a great alternative to traditional plastic which will positively impact your environmental footprint. These plastics are made from renewable and natural materials, making them ideal for breaking down into their natural compounds when disposed of correctly.

There are seven types of common plastics, with thermoplastics being found in many common products from toys and sports equipment to water bottles and packaging. Unfortunately, many traditional plastics can’t be recycled and contribute to not only landfill, but are toxic for wildlife and soil.

Compostable plastics provide a great alternative to these plastics, however, are not able to replace all current plastic uses. As interest increases in these products, it’s hoped that the cost will decrease due to higher demand, more available resources and increased availability.