Carbon footprints: Product life cycles
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Carbon emissions are generated at each stage of a product’s life cycle, from production of the raw materials, to manufacturing, delivery, use of the product at home and finally disposal or recycling. A product’s carbon footprint can vary widely across these different stages and companies can use this information to help them identify the most effective ways to cut emissions.
A product’s life cycle begins with the removal of raw materials and energy sources from the Earth. The greenhouse gas emissions associated with cutting down trees, growing crops or mining non-renewable materials (among other things) is considered in this part of a product’s life-cycle analysis. Transportation of these materials from the point of acquisition to the point of processing is also included in this stage. Examples of products in which the raw materials account for the majority of greenhouse gas emissions include crisps and cheese. Over 70% of the carbon footprint of most milk originates from its agricultural production, owing to emissions of methane from cows, manure and the cultivation of animal feed.
During the manufacturing stage, the raw materials are turned into the final product or package. Manufacturing can consist of a number of steps depending on what the final product is. Typically, the more steps that are required, the more emissions this part of the life cycle is responsible for. The manufacturing stage accounts for a large portion of the carbon footprint of products containing metal and concrete materials. Steel, aluminium and cement manufacturing is very energy intensive. Electronic goods often have large carbon footprints in the manufacturing stage because numerous raw materials are combined to create the final products, using large amounts of energy in the process. However, electricity consumption during use can also make a large contribution to the carbon footprint of such products.
The delivery stage of the product’s life cycle refers to the greenhouse gas emissions associated with transporting the product to where it will be sold or used. This includes the emissions embedded within any packaging used in delivery and the emissions associated with distribution and management. Products that are heavy, need to travel large distances, require refrigeration or air transport can result in high greenhouse gas emissions in this part of their life cycle. One example of a product with a large carbon footprint in the delivery stage is asparagus transported from Peru by aeroplane. This is partly due to the high emissions for air freight, but also partly because of the leakage of refrigerant chemicals which are potent greenhouse gases.
The ‘home use’ stage of a product’s life cycle involves the actual use, reuse and maintenance of the product. All activities associated with the use of the product are part of this stage, including energy used to power the product or make it work. The home use stage also includes refrigeration and cooking of food products. Many products generate their highest emissions during the home use stage, particularly light bulbs, kettles and cookers because they use a lot of energy over their lifetime. Maintenance and laundry also affect a product’s carbon emissions – the temperature of a washing machine and the amount of detergent used can make a big difference to the carbon footprint of a T-shirt. The home use stage can also influence downstream waste management emissions, through generation of food waste and waste water from a washing machine, for example.
The final stage of a product’s life cycle includes any emissions associated with its disposal or recycling. The main factors governing the amount of emissions in this part of the life cycle are: the material composition of the product, how easy it is to separate materials out of recyclable the product is, its size and weight, and how it’s disposed of. Generally, the smaller the product, the higher its percentage of recyclable material and the easier it is to separate the constituent materials, the smaller its footprint during disposal – although this relies on the use of energy-efficient disposal methods. Disposal is typically responsible for a fairly small amount of emissions compared with the rest of a product’s life cycle. However, UK newspapers produce most of their carbon footprint during disposal because of methane emissions when they biodegrade in landfills. Food waste creates greenhouse gas emissions, mainly as methane.
Life-cycle analysis can help businesses to identify where most of their greenhouse gases are being produced and take steps to reduce them. This can lead to more efficient products which are responsible for fewer emissions. Such products are often referred to as ‘green’ or ‘eco’. However, the question of whether these products actually result in fewer emissions is more complicated. Only a minority of consumers actively select ‘eco’ products, and while such products are responsible for fewer emissions than other similar products, in almost all situations choosing to buy nothing is a much better way of cutting emissions.