Fresh water is a small percentage of the total.
About 3 or 4% of the global water is in the form of freshwater and most of it is locked up in the Arctic and Antarctic ice caps. So, the actual available fraction of fresh water compared with all available water is less than 1% and this is what we must use for human and agricultural use.
It is a very small fraction but it’s still a significant quantity overall. But what we've been doing is very much to use it in a pretty much old-fashioned approach, where we basically try to capture it where we can put dams or other storage. We use it once and then basically get rid of it where we must pay to treat it before discharge into the environment.
Moving from singular water use to a circular economy.
Water has been typically subject to a single use approach, and this applies to many of the other materials we use, we need to think about a circular use philosophy which would be use, capture, treat, use-again.
This is where the concept of the circular economy is starting to come in, and this is a term that I've been using for over 20 years. I am glad to see that we have started performing water recovery and recycling, we need much more of this approach.
We have started to look at recovering not just the water, but also other elements including the energy contained in the wastewater organics, but also the nutrients which are probably the most critical one in that context.
Nitrogen in wastewater is not yet critical to recover because with energy we can pull nitrogen out of the atmosphere using the Haber Bosch process. Something in the order of 50% of what nature generates in terms of binding Nitrogen and turning it into ammonia and fertilizer is delivered by humans using the Haber Bosch Process, however, but we can recover nitrogen from human wastewater with less energy, so this is a circular economy opportunity.
The more critical nutrient to recover from wastewater is phosphorus. Phosphorus is being mined from mineral phosphate deposits and continues to be sourced from basically removing bird poop from remote islands, however, this resource is running out.
Phosphorous use is increasing because it is used in growing food, most of it ends up in waste materials. The food we eat ends up in our wastewater and this is discharged so we lose the phosphorous.
So, if we want to move to having a circular economy, we need to really need to really penetrate the whole water cycle, water in the economy, water in the society and water in agriculture.