Since the early 1990s, low flow shower heads have provided a more water and energy efficient way of showering. To be clear, renewable energy is part of the solution – solar boilers, biomass, heat generating windmills – but we also need to look at the demand side of washing in a post-carbon world. Furthermore, the use of renewable energy sources doesn’t lower the water use of the daily shower. All (current) wind turbines in the world could provide only 1 billion people with a “sustainable” daily shower. This is eight times the energy produced by wind turbines worldwide in 2017 (745 TWh). However, if eight billion people were to shower daily, total energy use per year would be 6,132 terawatt-hours (TWh). In principle, the energy for a shower could be generated by renewable energy sources. The emissions of a typical shower equal 3.5 – 7 km of driving 5 If we compare this to the carbon emissions of a relatively fuel efficient car (130 gCO2/km), the emissions of a typical shower equal 3.5 – 7 km of driving, and this result ignores the energy cost demanded by water treatment and distribution. Depending on the energy source (gas, electricity), the carbon intensity of the power grid (US/EU), or the efficiency of the gas boiler (new/old), the resulting CO2-emissions of an average shower amount to 0.462 – 0.921 kg. Heating 76.5 litres of water (8.9 minutes x 8.6 litres per minute) from 18 to 38 degrees Celsius requires 2.1 kilowatt-hours (kWh) of energy. Taking the Dutch as an example, let’s look at the energy use and carbon emissions of a daily hot shower. Research shows that in many industrial societies, and especially among younger people, it is now common to shower at least once per day. This is a conservative calculation: these data do not include the showers taken outside the home, for example in the gym. In many industrial societies it’s now common to shower at least once per dayĪltogether, the average Dutch person used 50.2 liter of water per day for showering in 2016, compared to “only” 39.5 litres of water per day in 1992. For example, in the Netherlands from 1992 to 2016, shower frequency increased from 0.69 to 0.72 showers per day, shower duration increased from 8.2 to 8.9 minutes, and the average water flow increased from 7.5 to 8.6 litres per minute. One of the reasons is that people are showering longer and more frequently, and using increasingly powerful shower heads. In contrast to the energy used for space heating, which has decreased during the last decades, the energy used for hot water in households has been steadily growing. Water treatment and distribution also use lots of energy. Hot water production accounts for the second most significant use of energy in many homes (after heating), and much of it is used for showering. More attention is given to the showers’ high water consumption, but energy use is just as problematic. This practice requires two scarce resources: water and energy. Each day, many of us pour roughly 70 litres of hot water over our bodies in order to be “clean”. However, like airplanes, cars, and heating systems, it has become a very wasteful and carbon-intensive way to provide for a basic need: washing the body. The shower doesn’t get much attention in the context of climate change. Designer Jonas Görgen developed a a-do-it-ourselves-guide kit to convert almost any shower into a mist shower and sent me one to try out. The mist shower, a satisfying but forgotten technology which uses very little water and energy, could be a solution. The daily shower would be hard to sustain in a world without fossil fuels.
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