So what would this mean for our zero-carbon projects?
Well, let’s take a typical very large office building. Say perhaps 30 storeys with a 50m by 50m floorplate – similar in size to the Leadenhall Building in London - producing 80,000 tonnes of CO2e during construction and 4,000 tCO2e a year during operation.
This building would need one 3MW wind turbine to offset its operational emissions, and another two to offset its construction emissions over approximately ten years.
As another example, let’s say we have a road project in South Africa with construction emissions of 50,000 tCO2e and annual operational emissions of 10,000 tCO2e (primarily from the vehicles using it).
Using solar PV this time, this project would need about ten hectares of solar panels to offset its operational emissions, and a further five hectares to offset the construction emissions over ten years.
There are a few caveats:
1. The low-carbon generation must displace fossil fuel generation
2. The low-carbon generation must be additional.
3. Any rebound effects – such as where people use more energy because you make more available – need to be factored in.
Implementing this also relies on thinking beyond the traditional ‘red-line boundary’ of a project’s site. For example, the solar panels adorning the new Blackfriars station in London only offset around half its operational energy use. To make it carbon-neutral you would have to develop additional generation elsewhere. Perhaps solar panels out in the countryside ‘owned’ by projects would emphasise the relationship between the built environment and the energy it depends upon.
There’s also the problem of what, or who, will drive this. I’m certain that the science shows there’s a need for this. And I’m sure I can demonstrate how it could work technically. The question now is who will incentivise it to happen?