Secondary data is vital for faster and more accurate carbon calculations

The most reliable calculations were obtained from direct measurement of emissions, said Tesco sustainability manager Katherine Symonds. However, secondary data "from a trusted source and which provides a standardised number", was "likely to become very important in helping people calculate consistent footprints in a cost effective way", she said.

More work was needed to "understand the difference between undertaking the same activity in a different country", said Symonds. But she added that "early agreement on a standard template for data collection, which is available to all, will help ensure consistency and sharing of data".

In many cases, however, companies would only be capable of providing estimates, rather than exact figures, she accepted: "For example, where products are manufactured on site there can be difficulties in allocating impacts to a specific product, as sub-metering - or the collection of emissions data on specific production lines - is uncommon."

Symonds, who has worked with suppliers to calculate the carbon footprints of 20 products from detergent to orange juice, said 12 weeks was "a feasible timeline for collecting data and calculating and certifying a footprint".

However, the process would become faster and cheaper in future, she predicted.

Printer friendly version

Email this article to a friend