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Sustainability Scale

Many policies recognise the importance of sustainability and promote sustainability. The reason for its increasing importance is that our global population makes increasing demands on the Earth's finite resources, while continuously dumping man made pollutants and waste into the environment. Some of these pollutants add to the effect of global warming, and some persist in the environment for many years. This continuous process of depleting finite resources, polluting and discarding cannot continue forever - it is not sustainable. However, there is no absolutely sustainable process: no process can be sustained forever.

Therefore, a more helpful approach might be to categorise levels of sustainability. For example, using a logarithmic scale, we can categorise the duration of sustainability:

Category (C)	Duration of Sustainability (years)
0	Not sustainable.
1	1 to 10
2	10 to 100
3	100 to 1,000
4	1,000 to 10,000

A category (C) refers to something that is sustainable for up to 10^C years.

Example: Solar Power

Using the Sun as an energy source might well be a very sustainable process, as its remaining life-time is expected to be over 1 billion years. So solar power can potentially be a category 10 process (sustainable for 1 to 10 billion years)!

Note, however, that the actual process and products that harness the solar energy might be much less sustainable; depending on the mining of the raw materials for the solar panels, the refinement of those materials, the manufacturing process, transportation, and disposal of old panels.

Example: Resources and Waste

Category (C)	Duration of Sustainability (years)	Example
0	Not sustainable.	Avoid this category of product or process, if you can and if you care.
1	1 to 10	Processes that can only operate over this duration are barely sustainable and should be avoided where possible.
2	10 to 100	Assuming current rates of extraction, over this period some fossil fuel resources (e.g. gas and oil fields) will become depleted, or not economically viable. Sustainability at this level might mean using those resources more efficiently and switching to more sustainable processes. Oil might be used more for producing chemically derived products and less for combustion in transport and power generation. Biodegradable products enter the market, and more products are designed to be reusable and recyclable. Non-reusable and non-recyclable level 0 products are actively deterred.
3	100 to 1,000	Assuming current rates of extraction, over this period most fossil fuels may become depleted or not viable, along with many other raw materials. Fossil fuels would become an insignificant power source, being replaced by renewable sources (i.e. direct and indirect energy from the sun). Raw material consumption and waste disposal would tend to zero, and all activities would be dependent on efficient reuse and recycling processes.
4	1,000 to 10,000	All activities would be dependent on very efficient reuse and recycling processes, and direct (and indirect) solar power. Significant rates of raw material consumption could only be continued if new sources were used (e.g. deeper below the Earth's surface, asteroids, or other planets).

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