Hello Everyone!!
There's been a lot of talk lately about energy choices and even embodied energy for the impact of energy sources on global climate change, but so far there isn't nearly enough talk about the impact of energy choices on water. In particular this is an important factor in which biofuels are likely to be viable in the long run.
While corn ethanol and nuclear power have often been touted as the most technological ready and "practical" alternatives to coal and oil, they also among the most water water intensive sources of energy. Very often the discussion surrounding nuclear power focuses on the ability to control risks associated with radiation and nuclear weapons. But guess what? It takes a lot of water to both safely run nuclear reactions (Overheating and coolant failure caused the Chernobyl disaster.), but to also use the heat to run a turbine and produce electricity. Of course all forms of electric production that depend on a hot steam turbines require water, and this includes coal, oil, natural gas, biomass, and even large scale solar thermal electric plants. The thing about nuclear reactions is that they produce so much heat that two out of three units of heat produced by a typical nuclear plant are released into the environment, much of it using cooling water. This is why nuclear plants are almost always situation near a large river! Coal plants despite their contributions to global warming, use as little as half as much water per MW-hour (this varies from plant to plant). Natural gas uses less water per MW-hour still.
Solar thermal and geothermal plants can also be water hogs because they also use steam to run a generator, although some engineers are looking at plans to reduce their water consumption by using closed loop waters systems and air cooling systems. More radical ideas involve using liquids other than water to run closed loop turbines. According to some proponents most of these alternatives have a lower evaporating point and can therefore generate power at a lower temperature. The same concepts are being looked into for coal and natural gas plants. But as of now expense and engineering "bugs" have kept them from widespread use.
For electricity, photovoltaics and wind have by far the lowest water consumption, because they don't involve steam turbines. Both have a significant aquatic footprint in their construction, neither continue to require water in order to run.
With biomass for fuel you not only have the water involved in growing the plants but also the water involved in converting them into usable fuel or electricity. Corn grain ethanol is a big offender not only because corn is a relatively thirsty crop, but also because of the large amounts of water involved in malting the corn into sugars and starches and fermenting them into alcohol. As anyone who has ever seen a whiskey still could tell you the amount of water that has to be removed for even a small amount of alcohol is significant. (This is one reason why both beer and liquor factories like nuclear power plants have historically been located near rivers.)
Fortunately not all biomass alternatives are equally "thirsty". One biotech company known as Virent Energy Systems, claims the processes they are developing to transform agricultural waste materials (which don't require the land, energy, or water involved in dedicating a whole crop for fuel) into high qualities fuels are in fact water positive, or produce more freshwater than they consume. Furthermore oils or sugars produced from algae could be produced using saline water or wastewater instead of fresh water. In the latter case side benefits could potentially include cleaning the water and producing fertilizers and/or animal feed as well as fuels.
So the bottom line is that conserving energy is not only a survival strategy in the face of climate change, but also in the face of the global water crisis. Similarly it is not only important to develop and promote energy sources that emit fewer or no greenhouse gases, but also require less water.
That's all for today.
Say Goodnight Readers!
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