Post 35. Are all carbon footprint calculations are equal?

 

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There are multiple definitions of carbon footprint, and a lack of a definitive one. Most definitions are based on our footprint as our warming potential, or impact as individuals, communities, and businesses. 

Carbon Dioxide Equivalent (CO2e or CO2eq) is the standard unit of measure to compare different greenhouse gases (GHGs). Using this metric, we can compare the emission of different gases on the basis of their warming potential and combine them together to give one number, our carbon footprint. So let’s go with… the carbon footprint is the total annual emissions relating to a person, household, product, business as expressed in usually tonnes of CO2e. 

The IPCC states that the carbon footprint of products is usually determined using lifecycle assessment (LCA), whereas the carbon footprint of people, households, or nations is modelled using input-output analysis.[1]. In fact, there are many ways of ‘calculating’ a carbon footprint. 

This definition also assumes that the carbon footprint calculation only goes one way… that we are only creating CO2e in our daily activities. That is just not the case. As individuals in our gardens, the trees in our street, our pot plants.. we are absorbing carbon dioxide too. 

One industry sector that is absorbing carbon (sequestering) 24/7 is agriculture. Carbon is absorbed in our food and in nature around us. In the UK, using DEFRA figures [2], the UK Total Agriculture GHG emissions fell from 58.9 million tonnes CO2e in 1990 to 45.6 million tonnes in 2017, but what about the sequestration? 

The data on emissions is easy to find – the data on sequestering less so. This recent study shows in grassland the carbon sequestering varies by location (rainfall, sunshine, grass species, soil quality etc.) and from 469 to 793 kg CO2 per hectare [3]. 

So what carbon footprint calculations will we use in the future? As we adopt more circular models of living – recycling, reusing, repurposing, how will that be included in our footprint? Will we need a new calculation? 

[1] https://www.ipcc.ch/site/assets/uploads/2018/02/ipcc_wg3_ar5_annex-ii.pdf 

[2] https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/835762/agriclimate-9edition-02oct19.pdf 

[3] https://www.agronomy.it/index.php/agro/article/view/1789/1265