Producing a fair comparison of an on-line versus an off-line service (typically one that has yet to be digitalised) requires equivalent scopes of assessment. Establishing comparable service boundaries plays a significant role in the outcome, with shared resources needing to be divided up between services appropriately. For example, what percentage of the footprint of a data-centre or cloud service provision applies to a particular service? If a web site or mobile application delivers more than one service, how are their carbon footprints divided? While cloud services providers are increasingly building in tools to show this information on a per service level, it depends on whether the services are deployed in ways that line up with the way these tools work. Outside the cloud providers there is much less support for per service footprint analysis, especially for on-premise deployed platforms. There is very little support at all to help make assessments for legacy systems and services.
We were unable to find any specific examples of evaluation frameworks that are specifically targeted at digital services. At least not publicly available. There are examples of attempts to calculate the carbon footprint of digital services by various organisations but these are typically incomplete or deliberately partial assessments of the total footprint of the service.
There are however frameworks for more general assessment of carbon footprint analysis that are applicable and would be excellent starting points for digital service footprint analysis. The challenge will likely be in finding the combination of skills required to bridge the gap between the sustainability analysis, and having a sufficiently deep enough understanding of the digital technology.
A good first step is to measure, then understand, then implement.