I think the answer to your question is highly dependent on the definitions you use. 

If, for example, you consider that Sustainability is the ability of a community to maintain a non-declining quality of life using the resources it manages, in perpetuity, then a corporation claiming to be improving the sustainability of the community they serve (regardless of those boundaries are drawn) would have to show that they:

• do not extract resources or produce wastes faster than the landmass managed by the community can support in perpetuity.
• do not import resources or export wastes to meet needs.
• do not increase the time required for people in the community to meet all of their needs - this would mean measuring existing and predicting for the future, the time used by people in the community they serve to meet their needs, divided by how effectively their needs are met.
• do not reduce the amount of land set aside by the community to be neither a sink for wastes nor a source for resources.

AND, it would have to show that it does at least one of:

• increase the efficiency by which people use their time to convert resources into the means to meet their needs (technological development)
• Increase the effectiveness by which people use their time to meet their needs (human development)

at the same time as ensuring the costs associated with providing development activities are not borne unequally with the benefits associated with the development, for any identifiable group within the community (social justice).

If you use a different definition of Sustainability, you will likely come to a different conclusion.  In order that your approach allows predictability without a string of caveats, you will need your definitions to be objective, repeatable, sensitive, and universal. 

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Yes, depends on what you intend as Sustainability. In general, Life Cycle Assessment is used, but is very complex and involves also a lot of categories like energy, GHG, water consumption, pollutants, etc.

It's better, in my view, to concentrate on a couple of relevant Impact categories like ENERGY and GHG.

Assessing present and future use of Energy in Organisations or Countries would be a (not trivial) first stage step.

As a second stage, assessing the production of GHG would be also a good point.

The assessment of these two Impact categories in the European Union for Transports is reported in the Well-to-Wheel study (see first link below)

Calculations are not easy and require, more than "magic tools" figures describing the processes you are characterizing.

In example, the electricity consumption implies also a certain GHG emission per kWh, an example is reported in the second link

Good work!

Alberto

http://iet.jrc.ec.europa.eu/about-jec/downloads

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