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 shampoo. Over 90% of the carbon footprint of most milk originates from its agricultural production, owing to emissions of methane from cows and the intensive farming methods used to feed them.

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. The more manufacturing that’s required, the more emissions this part of the life cycle is responsible for. Typically, the manufacturing stage accounts for a large portion of the carbon footprint of products such as digital cameras and ink-jet printers – although the use of ink cartridges over a printer’s lifetime can also have a large carbon footprint. 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.

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 any logistics or management. Products which are either heavy, need to travel large distances or require refrigeration 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 chilled fruit juices from distant countries, such as orange juice imported to the UK from Brazil. This is partly due to 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 any waste materials the product may produce, such as waste water from a washing machine. 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 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: how recyclable the product is, its size and weight, and how it’s disposed of. Generally, the smaller the product and the higher its percentage of recyclable material, 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.

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. Whilst these 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. Even if the product is replacing an old inefficient model, it can take a number of years before emissions are actually saved.

• Carbon Trust: Products Footprints