Metals and synthetic materials such as Plastics, Nylon, Glass, and Resin etc. are an integral part of our life. It is very difficult to imagine daily life without them. Right from the toothpaste tube to the vehicle you drive to work or the phone in your hand, everything has some form of synthetic material or metal component in them. Consumption of materials by humans is growing exponentially. But have you ever thought how these materials are produced or what is the carbon footprint to produce them?
In this article, we will look into how various materials are produced, how much is the energy consumption to produce them, how can we reduce the carbon footprint by selecting the right material with the intent of energy consumption and sustainability.
How materials are produced?
For our analysis, we are looking at two groups of everyday materials – Metals and Synthetic Materials.
Metals are generally extracted from the metal ores. Metal production involves mining, crushing, washing and separating the ore from the accompanying material called gangue. Once the ore is separated, chemical-reduction process, also known as smelting, is used to produce the refined metal.
On the other hand, synthetic materials are derived from natural materials such as crude oil, coal, natural gas, silica, cellulose etc. Crude oil, a complex mixture of many compounds, needs to be processed first.
Production of plastics begins with distillation of crude oil in an oil refinery. This separates the heavy crude oil into groups of lighter components, called fractions. Each fraction is a mixture of hydrocarbon chains (chemical compounds made up of carbon and hydrogen), which differ in terms of the size and structure of their molecules. One of these fractions, naphtha, is the crucial compound for production of plastics.
Two main processes are used to produce plastics – polymerisation and polycondensation – and they both require specific catalysts. In a polymerisation reactor, monomers such as ethylene and propylene are linked together to form long polymer chains. Each polymer has its own properties, structure and size depending on various types of basic monomers used.
As seen above, each step of the metal or synthetic material production process uses energy which adds to the carbon footprint of material production.
What is the carbon footprint and energy consumption to produce these materials?
Carbon footprint is defined as -Total amount of CO2 and other greenhouse gases (GHGs) produced to directly or indirectly support human activities. It is measured in the equivalent tons of Carbon Dioxide (CO2).
All fossil fuels such as oil, natural gas or coal have carbon as the main component. When these fuels are burned to produce energy, GHGs are released. As human population is heavily dependent on fossil fuels, concentration of CO2, CH4 and other GHGs is continuously increasing in the atmosphere. GHGs contribute to global warming and are harmful to people and environment. We must strive to reduce our carbon footprint by all means to reduce concentration GHGs in the environment. The Intergovernmental Panel on Climate Change (IPCC) recommends reducing CO2 by 50–80% by 2050 to avoid dangerous climate changes.
Exact calculation of total carbon footprint for an activity, event or product is not straightforward due to lack of knowledge and unavailability of data from various contributing processes. For example, in case of metal production total carbon footprint must include individual carbon footprint of following components-
- Extraction of ore including carbon footprint of fuel used in the machines
- Transportation of ore to the refinery
- Crushing, washing and separating the ore from impurities
- Smelting to extract pure metal
- Transport of metal from refinery to factories
- Building of various products
- Assembly and packaging
- Transport of these products to the consumer
To calculate the total carbon footprint of a metal from cradle to site of use, energy consumed and amount of GHGs released in each individual process must be included. Total carbon footprint can also be calculated from cradle to grave (till existence of the material).
For the purpose of this comparative analysis we will look into the embodied carbon and the embodied energy of various metals and synthetic materials.
Embodied Carbon and Embodied Energy:
Embodied Carbon is the carbon footprint of a material which is calculated in Kgs. It is a measure of all the CO2 emitted in producing a material. It is calculated from CO2 emitted to extract and transport raw materials as well as CO2 emissions from manufacturing processes for the material.
Embodied energy is the total amount of energy used to produce the material from its raw form or raw materials. It is measured in MJ/Kg (Mega Joules of energy needed to make a kilogram of the material). The energy is usually measured as the lower heating value of the primary fuels used plus any other primary energy contributions.
The graphs below compares the carbon footprint and embodied carbon for different metals-
As we can see from the graphs above-
- Metals such as Aluminum, Tin, Titanium and Recycled Titanium have higher carbon footprint and embodied energy compared to other metals such as Iron, Copper, Lead, Stainless Steel etc.
- Raw materials with lower values can be used to reduce the overall carbon footprint of a product such as a building, a train or an aircraft.
- Similarly, recycled metals such as aluminum, copper, steel, zinc can be used instead of fresh lot to drastically reduce the total carbon footprint of a product, event, or building.
Although, each metal has specific properties suitable for specific usage so replacing metals may not always be as simple as it sounds. But the comparison helps us in selecting the most eco friendly metal when we have a choice.
The graphs below compare the carbon footprint and embodied energy for various man made or synthetic materials.
We can see that among the synthetic materials-
- Nylons, polycarbonates, polypropylenes and resins have higher carbon footprint and embodied energy compared to others.
- Mastic Sealant has highest embodied energy followed by Epoxide Resins, Nylon and Polycarbonates.
- Among the man made materials, glass and fiberglass have the lowest carbon footprint and embodied energy.
Sustainable Materials which Generate Smaller Carbon Footprint
Sustainability guidelines for energy and carbon emissions suggest that we need to halve our energy use from the year 2000 to 2050. At the same time, to allow developing countries to ‘catch up’ to the developed world, we would need to allow for a doubling of demand. Taken together, this would require that the energy intensity of material production in 2050 be only one-quarter of that in 2000. In other words, we are looking into the possibility of obtaining a 75 percent reduction in the average energy intensity of material production.
To achieve such ambitious goals businesses and organizations world over are developing low carbon technologies and sustainable materials. Some of such promising metals with smaller carbon footprints are Lithium, Cobalt, Nickel, Manganese, Copper and Rare Earth Elements (REEs). Lithium-ion batteries, Wind and Solar power are the clean energy technologies to reduce the carbon emissions. Lithium-ion batteries are used in everything from smart phones to electric vehicles and Lithium, Cobalt, Nickel are the ingredients for these batteries. Copper is used in wind turbines while some REEs are important components for a range of technologies from low-energy lighting and catalytic converters to the magnets used in wind turbines, electric vehicles and computer hard-drives. Copper, Nickel and Zinc are need for solar power.
Selecting the right material for the right purpose with the intent of energy consumption is the key to reduce the carbon emissions and energy use.
Reducing carbon footprint substantially is the need of the hour and everyone residing on planet Earth has to pitch in for a sustainable future. Some of the ideas to do that are listed below-
- Material Substitution – The idea is to use the materials with a lower carbon footprint in place of materials with higher carbon footprint. For example, substituting concrete, bricks or wood for steel in buildings and infrastructure, or steel for aluminum or plastics in vehicles. In some cases this kind of substitution will also save money. However, there are multiple parameters to consider such as material properties, life of the substitute material in the given operating conditions etc. while determining if the substitution is going to effectively reduce the total carbon footprint.
- Demand Reduction – Another idea is to reduce the demand for material consumption worldwide to reduce the carbon footprint. This can be done by adapting certain best practices in design, usage, and recycling. Optimizing the design of products to use less material, extending the life of products, re-using old components are some of the examples.
Reduction in demand for material also depends on personal choices and awareness is the key for people to make eco-friendly decisions. For example, according to an estimate, each individual spends approximately 225 hours per year in the car. If a country has 28 million licensed cars with, on average, four seats in each and there are 60 million people. So each car seat is, on average, in use for 2 percent of the year. It is possible to reduce the overall stock to 7 million cars with ease. This is, of course, will be at the cost of the convenience of having a car when one needs it. But such demand reduction is definitely an option.
- Increasing Material Efficiency – The essence of material efficiency is to be more efficient in how materials are used in the design of new products, to make products last longer and to optimize the operational intensity of the material goods (e.g. serve more people with a given product—to share). By themselves, these ideas are not new ideas. For example using an Ola or Uber instead of buying a vehicle is a way to optimize operational intensity thereby reducing global energy use and carbon emissions. Innovation in this area to address not only engineering challenges but also policy challenges is needed.
- Promoting Public Transport and Shared Usage of Resources – By using metro or carpooling for travel instead of driving alone, you are not only saving money but also reducing the carbon footprint and contributing towards sustainable future. Governments across the world must facilitate public transport and promote such measures on priority.
This article is our humble contribution towards educating readers about this important challenge humanity is facing.