Calculating Carbon Footprints

Dr Cooke's Yearly Carbon Emissions

Using Dr Cooke's self assessment of her lifetime's yearly contributions towards carbon emissions in the form of average, below average, above average, well below average, and well above average, these figures have been generated to reflect her yearly emissons, with the total metric tonnes shown at the bottom.

The Method – Carbon Dioxide Emissions

An excel spreadsheet is available below. This provides data, generated initially from The World Bank website, of the average yearly carbon dioxide output of someone living in the UK from the year 1960 until 2018.

Every ten years since 1960, the UK carbon dioxide emissions per capita has increased initially by 0.581 tonnes, then decreased by 1.445, 0.563, 0.723, 1.325 and 2.277 (8 years between 2010-2018 due to available data) until currently at 5.399 metric tonnes. If the decrease in carbon dioxide emissions continue until the UK-pledged goal of carbon neutral 0 tonnes by 2050, it has been estimated that the year 2030 will be approximately 4.0 and the year 2040 approximately 2.0, with the 10 years in between to average these estimates. This is the basis upon which the estimates of carbon dioxide emissions per capita after 2018 have been calculated.

Further columns have been created to provide 4 alternative options than the average amount of carbon produced, in metric tonnes. These are 'well below average' which is a half value, 'well above average' which is one plus half value, 'below average' which is three quarters value and 'above average' which is one and a quarter value.

Dr Cooke then estimated the years of her life and how she believed her yearly carbon dioxide emissions would compare to the national average over her complete lifetime. The result being 700 tonnes. Anyone wanting to calculate their lifetime's emissions should do the same. From here you can use the PDF in the appendix to add together all your years, along with estimates of your future yearly carbon output. Some guideline examples for these estimates from Dr Cooke’s life include: 1. For between the years 1963-1981 well below average has been chosen for part of a small household from a working-class background with few holidays abroad 2. The years 1981-1984 as average as a typical student 3. The years 1985-2004 as well above average for a working adult travelling lots for work.

The Method - Trees and Carbon Offsetting

Once you know how many tonnes of carbon you would like to offset through tree planting, you need to calculate the number of trees that would be needed. However, there are no exact figures for how much CO2 a tree will sequester in its lifetime and there are many factors that affect CO2 absorption, such as soil quality, tree species, weather etc. So, it is more important to work in terms of land, and number of trees will vary slightly but depend on this. Upon talking to a Woodland Trust representative, we are to understand that '25m2 of native planting will sequester 1 tonne of carbon over the first 100 years of its life (400 tonnes per hectare), assuming all the trees are the same age when planted, are a mix of native species and are managed to industry standards'.

From this information we can calculate that if 25m2 = 1 tonne over first 100 years, then an acre would sequester 162 tonnes over the first 100 years. As we need to offset 695.8 tonnes for Dr Cooke's lifetime, and rounding up to 700, then 700/162 is 4.3 acres. Which is equivalent to 1.7 hectares. This is the approximate amount of land that CO20 needed to acquire as the location for planting enough trees to offset Dr Alison Cooke's lifetime CO2 emissions and approximates equates to the 1.55 hectares finally calculated and allocated by Wessex Woodland.

Spacing between trees will also affect the number of trees planted at a site, but anywhere between 1100 and 1600 units per hectare is usual, any less can hinder the yield. The amount of carbon sequestered by a woodland of trees is calculated in WCU (woodland carbon units) after the fact, but before this has been achieved it is calculated in terms of PIU (pending issuance unit). The latter is a verified estimate for the amount of carbon that those trees will sequester after a period of time, and this lapse in time needs to be taken into account when thinking about one’s carbon emission goals. A carbon unit corresponds to one metric tonne of carbon dioxide.

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