With different regulations and initiatives arising, reporting of sustainability measures becomes a growing issue to organisations of various sizes. While currently the greenhouse gas emissions of office electricity and business travel or those of suppliers are being taken into consideration, not much effort is devoted to calculating the carbon footprint of digital content yet. Abide the storage and transfer of content being the core business for organisations like digital agencies.
This series of blog posts thus aims to provide such businesses with an approach to calculate their content carbon footprint. We start off with calculation basics and company websites.
Why there’s no one set way of calculating the content carbon footprint
As sustainability reporting is just arising, there are no set standards for calculating the impact of digital content yet. Neither exists one single truth regarding how much energy the transfer of data via the internet consumes. According to Wholegrain Digital, figures vary between 0.004 kWh per GB of data transferred and 136 kWh. A meta-study considering 14 existing studies on this topic found an accurate estimate for the amount of electricity needed to transmit one GB to be 0.06 kWh in 2015.
Wholegrain digital argues though that this number only takes into account a very narrow view of the ways data is being transmitted. They claim that in order to choose a proper estimate for the energy use of data transfer, we need to consider the following three factors:
- System boundaries: Which parts of the system of data transmission is taken into consideration for this calculation of electricity needed per GB? The meta-study for example only considered the narrowest system boundaries, representing the network equipment used for data transmission and access at a national level. Comparably with the reporting scopes 1, 2 and 3, one has to set clear system boundaries for their calculation.
- Date of the measurement: When has the study estimating the energy consumption per GB been conducted? More recent studies tend to suggest lower energy rates, as technology is becoming more efficient.
- Author of the study: What conflicts of interest do the authors of the study have? Wholegrain Digital noticed that studies funded by tech companies might want to play down the level of energy consumption, while studies reporting very high emissions might rather be funded by industries negatively affected by digitalisation.
These factors are by far not the only ones the calculation of data carbon emissions relies on, but some aspects are even harder to consider, e.g., if the energy for onsite network equipment should be measured in kWh per hour and not per GB, or how far the data center and the end users are apart. To consider all this would be very complex and mostly not practical, Wholegrain digital argues. But all this demonstrates why there is no one calculation basis for all data transfer emissions.
How much CO2 does a website emit?
Now that we’re aware of the potential backgrounds of content carbon emission numbers, let’s get some real numbers out there. As stated before, these are all estimates providing us with some starting point for calculating the content emissions. In order to estimate the carbon footprint of your website, there are different tools that do the math for you. As their approaches vary a lot, I present two tools of which the estimation formulas seem quite science-based.
Website Carbon Calculator
You might have come across carbon footprint tools like the website carbon calculator before, a site that estimates the carbon footprint of single web pages and compares your page’s performance to others tested. The home page of this blog for example doesn’t do too well in terms of its carbon footprint: 0.79 g of CO2 is being emitted on every page visit:
For this calculation, Wholegrain digital, the developers of the website carbon calculator, assume an energy factor of 1.8 kWh/GB for 2017 (based on this study). In evaluating different carbon footprint calculators, the developers of one of the tools, GreenFrame, though argue that the 1.8 kWh/GB factor is overestimated (according to these more recent estimates). Also, they claim, as the website carbon calculator only looks at network traffic, this tool may underestimate the even higher impact of the device use. As they developed their own tool GreenFrame, keep in mind that their critique of the website carbon calculator may be biased.
GreenFrame is said to be setting the broadest system boundaries in estimating CO2 emissions of websites, as it’s considering the screen, the client device, network and data center if possible. The carbon footprint estimates the GreenFrame tool provides are thus a lot more detailed than the ones by the website carbon calculator. GreenFrame though is not for free (after a test-month) and comes as desktop client.
On their website, they provide various benchmark analysis, so here, you can take a glance at how the Wikipedia page performs in terms of carbon emissions:
Other than the makers of the website carbon calculator, GreenFrame doesn’t fully publish their formula, but they claim their estimates to rely on these steps (as stated here):
- Gathering metrics at system level (including client device), as system metrics correlate to energy consumption according to research (although GreenFrame doesn’t particularly name the studies),
- Converting system metrics to energy consumption in watt hours, based on several studies (e.g., one about the energy consumption of mobile data transfer, or one about the memory power consumption in database systems),
- Adding up the energy consumption of all these components, including Power Usage Efficiency of datacenters,
- Calculating CO2 emissions based on carbon footprint of electricity. Therefore, they by default use the world average of 442 g/kWh, which can be configured taking into account the user base and data center localisation.
Summary: The carbon footprint of a website
As you can see from the first part of this blog post, estimating the carbon footprint of your website can be quite difficult, especially, as you have to consider various factors. The two tools presented in this post follow totally different approaches, of which one is a lot more detailed than the other one.
No matter what approach or tool you choose, most important is that you do start creating awareness about how much CO2 equivalents your digital content emits and start lowering your carbon footprint. Therefore, both the website carbon calculator and GreenFrame provide a starting point of recommendations on what to optimise. So choose your approach and go measure the impact of your website now!