Exxon Pipeline Disruption

Carbon Offset: 120.47 Metric Tons

Vintage: 2021

Location: Surrey, United Kingdom

A new pipeline has been proposed to supply fuel to Heathrow airport, carrying fuel between Southhampton and London. Scott Breen (also known as “Digger”) dug and occupied a pit and shed next to the M25 at Chertsey in Surrey for 22 days. Other activists also damaged equipment.

$$ {\sum_{n=1}^{days}({Fuel_{tonnes\,per\,day} \times CO_{2\,tonnes\,per\,unit fuel}} \times n} ) $$


Step 1: Calculate the quantity of CO2 emissions that were delayed on each day of the action.

The Exxon pipeline is proposed to increase the supply of aviation fuel to Heathrow Airport by 40%.1 As of 2021, Heathrow Airport used about 22 million litres of fuel per day.2 We first calculate the increase in capacity and convert this volume into a mass, assuming the density of Aviation fuel is 0.8 kilograms/litre. 3

$$ \begin{aligned} kg PipeCapacity/day &= {{litreFuel/day \times IncreasePercent} \over kgDensity/litre} \\[5pt] &= {22{,}000{,}000 \times 0.4 \over 0.8} \\[5pt] &= 11{,}000{,}000 \end{aligned} $$

Aviation fuel releases 3.16 tonnes of CO2 for every tonne burned4, so we then calculate how many tonnes of CO2 will be emitted each day due to the extra fuel supplied by the new pipeline.

$$ \begin{aligned} tCO_{2}/day &= tFuel/day \times tCO_2/tFuel \\[5pt] &= {11{,}000{,}000 \over1000} \times 3.16 \\[5pt] &= 22{,}246.4 \end{aligned} $$

Step 2: Calculate the benefit of delaying (temporarily storing) these emissions for the period of the action

Scott Breen occupied a tunnel to block the pipeline construction for 19 days when a court injunction was issued, giving him 3 days to leave the site.5 Therefore we assume that the construction was disrupted for 22 days. We then calculate the amount of fuel that was delayed from reaching Heathrow during this time period.

Fuel arriving to the site on day 1, would be stored for 22 days. Fuel arriving on day 2, would be stored for 21 days. Fuel arriving on day 3, would be stored for 20 days and so on. The sequence of days between 22 and 1 must be multiplied by the CO2 emissions that are delayed for each daily quantity of fuel that is held up by the pipe blockade.

Converting these figures to years, this calculation yields the tonne-year benefit of the storage:

$$ \begin{aligned} tonne_{years}CO_2 &= {\sum_{n=1}^{days}{{tCO_2/day} \times n} \over 365} \\[5pt] &= {\sum_{n=1}^{10} {22{,}246.4 \times n}\over 365} \\[5pt] &= 15{,}420.1 \end{aligned} $$

Step 3: Calculate the offset

We then use an equivalence factor of 128 which was calculated using the Lashof method with a discount rate of 0 and a time horizon of 100 years.6 7 This equivalence factor posits that the effects of the release of 1 tonne of CO2 emissions is offset by the storage of 128 tonnes of CO2 for 100 year.

$$ \begin{aligned} Offset &= {tonne_{years}CO_2 \over equivalence} \\[5pt] &= {15{,}420.1 \over 128} \\[5pt] &= 120.470 \end{aligned} $$

By this logic, this action offset the effects 120.470 tonnes of CO2.