Green Metrics, Clean Metrics

Dynamic Carbon Footprinting

The term "dynamic carbon footprinting" can be used in at least three different ways, as if we needed more confusion.

1. As opposed to static carbon footprinting, I think of dynamic carbon footprinting as a method that takes into account the time dimension. When certain emissions are generated is as important as the quantity of those emissions. The timing is critical in analyzing a whole range of carbon emission and sequestration processes: CO2 gradually absorbed over time by newly planted trees, natural systems (such as soil) and products (such as wooden furniture or building components) that sequester CO2 for limited periods, emissions generated throughout a long use-phase for a durable product (especially in comparison to the production emissions generated at the beginning), etc. [More on this in previous posts: 1 2 3]

2. Businesses operating in a carbon-constrained world may evaluate each other's carbon footprints in a continuous attempt to minimize overall carbon emissions in their value chains. For example, this could involve comparing the footprints of similar products made in different parts of the world while choosing global suppliers [1]. The competitive dynamics involved in these emission reduction efforts have led to the term "dynamic carbon footprinting". [More]

3. The least interesting and unduly complicated use of the term has to do with displaying "dynamic carbon labels" for RFID tagged goods using NFC enabled mobile phones. The idea is that each "instance" of a product has a different footprint, because of differences in transport and storage emissions. A consumer could check the carbon footprint of a product on the store shelf using a mobile phone and get a number that is good for just that store. [More]

Kumar Venkat

Do food miles matter?

Do food miles matter? The short answer: Not much, from a carbon footprint perspective -- with some exceptions such as fresh foods that are air freighted.

By way of illustration, here is a pie chart that shows the life-cycle greenhouse gas emissions of cooked potatoes broken down into key life-cycle stages. In this particular example, potatoes are grown conventionally in California. The raw potatoes are then transported 1500 miles in a refrigerated semi-trailer truck. Cooking steps include baking or frying in commercial kitchen equipment, followed by a steam table. Of the cooked potatoes, 20% are wasted and landfilled. The landfill is located in a temperate/wet zone, 50% of the landfill gas is methane, and 25% of methane is recovered and combusted as fuel. Transport contributes about 9% of the total life-cycle greenhouse gas emissions in this example.

   

These results shouldn't be surprising. A 2006 study from New Zealand (Saunders, et al) showed that it was important to look at the full life cycle of food products in order to optimize carbon footprints. That study found that several food products (milk, lamb, apples, onions) produced in New Zealand and transported to the UK produced fewer total GHG emissions than similar products produced locally in the UK.

In addition, we've seen cases where locally produced food is distributed inefficiently using small vehicles that transport the products hundreds of miles to farmers markets and other outlets. So replacing the long-distance supplier with a local supplier in the above example wouldn't significantly reduce the (already small) transport impact.

So is there any value to emphasizing locally produced food?  There may well be benefits: taste, freshness, possibly lower risk of disruption/contamination, supporting local businesses, etc. But lower carbon footprint is generally not one of the automatic benefits.

Kumar Venkat