Despite limited availability of freshwater for human use (availability estimated at a worldwide total of 4,200 cubic kilometres), withdrawals continue to increase globally. In a situation of secular overuse, drought turns into a much more severe crisis. By 2030, without a substantial improvement in water management, this figure could be close to 7,000 cubic kilometres – an increase driven by growth in population and prosperity. If we want to avoid a much more severe water crisis in future, we will have to find ways to reduce freshwater withdrawals by 40% compared to this status quo extrapolation. A 40% reduction within the next 15 years seems like a lot, but it is not impossible.
Rapid migration into urban areas, and population growth within the areas themselves, have strained resources like water and energy. Cities receive a finite amount of water from sources — like upstream watersheds and dams — that must be shared with agricultural and industrial sectors. There’s a growing need to make urban water supply resilient to droughts and other disruptive forces. At the same time, cities are struggling to manage the waste produced by these growing populations. In China, for example, cities collectively generate over 40 million metric tons of sewage sludge — enough to fill six Great Pyramids of Giza annually. There is, fortunately, a way to tackle water resources and waste management simultaneously. Sludge-to-energy systems separate, capture, and utilize the methane gas from sewage sludge for energy, instead of releasing it into the atmosphere. Treating and utilizing wastewater as a valuable resource — rather than discarding it as waste — can create a new stream from which water, nutrients, and renewable energy can be harnessed.
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