So, we talk a lot about renewable energy. And sometimes we also use the word ‘sustainable’ when talking about energy sources.
Renewable and sustainable are not the same thing. But they are related.
Renewable refers to whether something can be replaced or regenerated in its same form.
Sustainable refers to the volume and rate of use, and whether we use it at a rate lower than its renewability. So we tend to substitute the word ‘renewable’ when we mean ‘sustainable within our current use case’. For example, coal is technically renewable, but not on timescales that match our usage of it.
I have often had a challenge with the way we talk about ‘renewable energy’. Because sunlight (for example) is actually not really renewable - it’s infinite. It doesn’t have to be replaced because we don’t use it up. Same with wind. But biomass energy IS (or can be) a renewable resource: we literally destroy a piece of biomass (e.g. corn, or peat) to use it for energy (e.g. ethanol or directly burning it). It then requires time to replenish. Ethanol takes a season, peat can take hundreds of years or longer.
I am going to explore a bunch of other factors in subsequent posts (e.g. the non-renewable materials used in capturing ‘renewable’ energy - such as what goes into a solar panel - the other stuff we mess up when we extract materials or burn renewable fuels, the equity issues in extraction and so on), but for this post, I just want to share a little sketch of renewability timescales.
I haven’t been able to find anything like this that I could reference, so I drew this myself. Obviously, it’s not complete, and has not been reviewed, so please take this for what it is - an illustrative sketch.
It’s notable to me when you put a little graphic together like this (which I just did! Look at that!), you can immediately see how far apart solar energy is from fossil fuels. One is widespread and infinite, and the other is only in certain spots around the planet and renewable only on timescales way outside our human comprehension.
It seems obvious that this should give us some small hints for which way to look for future resources and energy. Not that we can’t use fossil fuels at all (based on only this graphic), but we should be aware of how much we use, and how fast, and for how long. Obviously, cascading consequences of burning fossil fuels, such as the greenhouse gas emissions that lead to climate change, is a whole other layer of information! But even if we just look at the renewability of fossil fuels, it should give us reason to consider using them more sparingly.
It’s also notable that water sits in the middle of this graphic. Technically, surface water is super renewable - where it rains, it runs all over the place - but it doesn’t rain heavily everywhere. There are some parts of the world where surface water is in very short supply, and yet we still choose to live in many of these places.
And for groundwater, which might take thousands of years to percolate into spots we drain for irrigation (for example), it is essentially unsustainable based on our current use case (though small wells for shallow groundwater are usually completely sustainable).
Anyway, it can be a complicated picture overall, and this sketch definitely glosses over many of those complexities, but these building blocks of information paint at least a basic picture.
There will always be tradeoffs in the resources we exploit (and replace), but they can be made deliberately and transparently (in theory). And even this small amount of information should help us create and support better policy, be transparent about the lifecycle of our resources, and understand how we might amend our behavior to keep using resources that make our life better over the long term, not just the short-term.
Right?