The carbon footprint of a process or manufactured item is rather like the joke about statistics being worse than lies. The statistical figures are accurate, but may leave the reader with a very misleading impression.
Carbon footprints refer to the amount of greenhouse gas (CO2) produced by any manufacturing process. For calculation purposes this process is extended to include all transport involved, both for raw materials and delivery of the final products. Ideally the carbon footprint figure reflects the total amount of greenhouse gasses emitted by the time the product reaches the consumer.
Of course this can be misleading. It is quite possible for two products to have used the same amount of CO2 and other gasses during manufacture, only for one of those products produce more gas through regular use. The carbon footprint is an accurate number, but it only looks at the problems created by item production, not by item use. This need to be considered when looking at environmental impact.
An example of this would be different cars. A large amount of CO2 is created when manufacturing the cars, but a car that is cheaper to run, uses less fuel, and emits less pollution, would be far preferable in environmental terms.
Another consideration is Carbon footprint compared to a product’s lifespan. A product that lasts longer is usually preferable to a similar product that has to be replaced; there will be more CO2 produce in manufacturing the replacement. Of course, this is complicated by products becoming obsolete over time, and the fact that they may produce pollution in regular use. A chair that last for 20 years is better than a chair that only lasts 5. But a computer that lasts 20 years is of little advantage as it will be considered obsolete and in need of replacement long before the 20 years is up. It will also produce CO2 through the electricity it uses.
People often consider recycling to be a good thing, but this issue can be complicated. The recycling process can often produce more CO2; even the transportation of the recycled products is a factor.
The GHG footprint (Greenhouse Gas footprint) includes gasses other than CO2, giving a better estimate of the impact a manufacturing process has. Another method is the LCA (Life Cycle Assessment) which tries to include all the environmental impact a product will have from before it is manufactured to after it is disposed of.