This is a guide outlining whether metal is more sustainable than plastic, and vice versa.
We compare some of the key factors involved in the production, usage and waste management of each.
Summary – Is Metal More Sustainable Than Plastic?
- Whether metal is more sustainable than plastic depends on the type of metal that is being compared with plastic (aluminum, stainless steel, etc.).
- It also depends on the item or product in question, the company that makes it, and other factors.
- But, some general sustainability considerations might be:
- 1. Sourcing Materials – both metal and plastic are mined from non renewable resources, but, common metals tend to be fairly abundant. Additionally, metals tend to have a far higher recycling rate than plastic and can be recycled infinitely – meaning that metal (especially metal like aluminum) doesn’t always need to use virgin materials like some plastics might (although some metals like stainless steel might use new material in addition to recycled material)
- 2. Production – metals tend to have a higher production footprint than plastic, especially with energy use.
- 3. Transport & Delivery – plastic tend to be a lighter material than most materials, and might have a lower delivery/transport/freight footprint than some heavier metals.
- 4. Waste Management & Recycling – metals can be used infinitely recycled, and have a far higher recycling rate than most plastics (which some say justifies the higher production footprint and energy use). Once plastic can’t be recycled anymore, it has to be downcycled, sent to landfill, or incinerated. In relation to some metals though, particularly the ones that are made with alloys, there may be chemicals like chlorine required to break them down, and, some recycled metals like stainless steel still require some virgin material to make a new product (although other metals like aluminum, particularly aluminum cans, may truly be closed loop at can be recycled back into themselves)
- 5. Pollution, & Impact On Humans, Animals & The Environment – the potential issues plastic creates from a litter, human health, wild life, and environmental perspective, are probably greater than metal. Plastic is a heavily polluted material, contains additives and chemicals like BPA that may be a concern for humans (although metal drink bottles can contain chemicals that can leach as well), can be ingested by or entangle wild life, and creates other potential issues in the ocean, in rivers and on land. Micro plastics can also be an issue.
- Overall, plastic has some advantages in terms of production and possible transport footprint. But, metal seems more abundant, can be recycled infinitely, and doesn’t seem to create the range of pollution or other issues that plastic might. At the very least, metal seems like a more circular material that can contribute to a circular economy compared to plastic.
- But, it depends on the product in question, the life cycle stage in question, the sustainability indicator being measured, and others factors as to which is more sustainable
- Consumer behavior can also come into the equation
- Specifically with drink bottles, a metal bottle like stainless steel or aluminum that is re-used hundreds of times might be more sustainable in some ways than a single use plastic bottle
Examples Of Products With Metal & Plastic Options
- Furniture (tables, chairs, beds, etc.)
- Food & Beverage Goods (drink bottles, food containers and lunch boxes, etc.)
- Building/Construction Materials
Metal vs Plastic: Comparison
- Sourcing Of Materials – the sourcing of metal and plastic requires mining of finite materials – metal ores and fossil fuels. Common metal ores are generally abundant, whilst there is debate over the scarcity of fossil fuels (although it is agreed they are non renewable). Something to note though is that metal tends to have a far higher recycling rate. Theoretically, this may mean the rate at which we need to mine and extract metals into the future may even out or decrease, as long as demand for metal doesn’t keep increasing. For example, steel and aluminum furniture is likely already made of recycled content (inhabitat.com). It is estimated that ‘[when metals like aluminum and tin are recycled] … the amount of CO2 created in the production process is only 1/3 of what it would be if new ore were being continually extracted’ (desjardin.fr). Other estimates say ‘through the recycling process it saves 95% of the energy that it would cost to produce new aluminum’ (azahner.com).
- Production – steel and plastic both use energy and resources in the production stage. Some sources indicate in some countries, metal production uses more energy than plastic. Using recycled metal material can reduce the sourcing and production footprint of metal products somewhat. Even though plastic production has some very negative production requirements, when compared to the production of tin and aluminum containers it only uses a fraction of the energy … When the production process for each is compared it is found that 1 kg of Polyethylene plastics produce around 4 kg CO2 and 1 kg aluminum produces 10.63 kg CO2 (desjardin.fr)
- Delivery & Transport – some metals are heavier than plastic, so, it may have a higher delivery/transport footprint from increased fuel use. Plastic may also be more space efficient because of it’s properties.
- Usage – metal can be more durable than some plastics, adding to the lifecycle duration of metal products.
- Waste Management & Recycling – in most countries, metal has a far higher recycling rate than plastic. For example, ‘steel produced by predominantly scrap-fed electric-arc furnaces accounted for more than 60% of the total raw steel produced in the United States in 2013’ (theguardian.com), and, ‘More steel is recycled each year than aluminum, paper, glass and plastic combined’ (azahner.com), and, ‘By volume, copper is the third most recycled metal following steel and aluminum’ (azahner.com). Additionally, metal can be recycled infinitely, whereas plastic can only be recycled a certain amount of times before having to be downcycled. In relation to some metals though, particularly the ones that are made with alloys, there may be chemicals like chlorine required to break them down. And, some recycled metals like stainless steel might still require in the range of 40% virgin/new raw material to make a new product (assda.asn.au) (although other metals like aluminum, particularly aluminum cans, may truly be closed loop at can be recycled back into themselves – aluminum.org)
- Pollution – plastic is usually responsible for far more pollution (via littering and inadequately disposed of waste) at the end of material life cycle stage.
- Degradation – plastic usually takes far longer than metal to degrade in the environment.
- Impact On Humans – plastic can impact humans in a number of ways – leaching of BPA and other chemicals, ingestion and inhalation of micro plastics and so on. That is not to say that products like stainless steel and aluminum drink bottles don’t have their own potential leaching issues.
- Impact On Wild Life & Environment – plastic tends to have more potential for negative impact on wild life and the environment via ingestion and entanglement in plastics. Micro plastics can also play a role, as well as leaching of plastic additives into aquatic environments.
- Metal vs Plastic Furniture – metal may win out over plastic furniture in health, and lifecycle, reuse and recyclability indicators (inhabitat.com). Micro plastics in the air indoors that humans may inhale are also more closely linked to plastic furniture and textiles.
- Metal vs Plastic Bottles – single use plastic bottles heavily contribute to waste and pollution problems. Metal bottles can be more sustainable than plastic bottles, but they usually need to be re-used over a longer period in order for their production footprint to average out to match plastic bottles.
- Metal vs Plastic Packaging Items – Plastic packaging may be more sustainable across a range of environmental indicators compared to steel and aluminum … [and, using metal would result in a significant net negative environmental impact in the case of carrier bags, caps and closures, beverage containers, stretch and shrink film, other rigid packaging and other flexible packaging] (packaginginsights.com)
The Sustainability Of Plastic
Read more specifically about the sustainability of plastic in this guide.
The Sustainability Of Specific Metals
Other Factors To Consider
- Just as there is different types of plastic, there are different types of metal. Each different type of metal can have a different sustainability footprint (depending on how it’s extracted, refined, fabricated etc.)
- The waste management systems, facilities and technology in a given country or State make a difference to the sustainability not just of different materials, but different waste items and products (because of how different waste materials and items are processed among the different disposal options at different rates)
- How long a metal product or item lasts, or how many times it can be used/re-used before being thrown out, impacts it’s sustainability footprint
- Whether the metal product uses recycled material or not impacts sustainability
- Although there are general sustainability factors to consider with metal and plastic, the size, weight and other features of an item or product can impact sustainability too. One material might be less eco friendly than the other per gram for example, but if the final product it’s used in is lighter than the same product made with another material, that product can have a better sustainability footprint even if the material itself isn’t as sustainable.