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Will Water Vapor from Hydrogen Cars Add to Greenhouse Gases?

A reader of this blog, Burt B. has sent in some concerns that water vapor from hydrogen cars may contribute to greenhouse gases.

Burt B: “I saw the BMW Hydrogen 7 advertised on CNN this morning. It looks like the technology is maturing. I have questions about the water emissions. The water that is made by hydrogen fuel combustion, and I guess fuel cells, probably shares characteristics of distilled water. I understand that distilled water is more corrosive than natural water. Might it become a waste disposal problem?

How will the water be handled? There are three methods that I can think of: misting it into the air, allowing condensed water to drip onto the road and storing it in onboard tanks for draining at a convenient time and place, probably when fueling … can you please explain what happens to the water created by using hydrogen fuel?”

Hydro Kevin: “Thanks for your questions about hydrogen. I’ve talked about water vapor from hydrogen fuel cells and greenhouse gases before. But, I also want to add some new information as well.

For instance, many people make the assumption that hydrogen internal combustion engine and fuel cell cars give off water vapor from the tailpipe but gasoline-powered cars don’t and this is not accurate.

Here is a quote from the MadSci network about the chemical makeup of gasoline, ‘Although gasoline contains many different chemical compounds, it is made up mostly of hydrocarbons, and all hydrocarbons form the same products when they are burned (just in different amounts). When a hydrocarbon is burned (that is, reacted with oxygen), it forms carbon dioxide (CO2) and water (H2O). For our average gasoline of C8H18, the reaction is 2 molecules of octane reacting with 25 molecules of oxygen (O2) to form 18 molecules of water and 16 molecules of carbon dioxide.’

So, the point is that gasoline-powered vehicles are already putting out tailpipe emissions that contain a noticeable amount of water vapor into the air. It’s the carbon dioxide, carbon monoxide and nitrous oxide emissions that we need to stay focused on cleaning up above and beyond the water vapor, which is the natural ingredient in clouds.

As to distilled water being more corrosive that natural water, here is a quote about distilled water from the Wise Geek website, ‘Natural water usually contains a number of microscopic contaminants, along with dissolved minerals such as calcium and iron. One way to remove these elements from water is to boil it until it changes to steam, a process known as distillation. When this steam is allowed to cool down and condense into liquid form again, the result is a purified form called distilled water. Distilled water should ideally be nothing but hydrogen and oxygen molecules, with a PH level of 7 and no additional gases, minerals or contaminants.’

Storing the water onboard a hydrogen vehicle rather than letting it drip from the tailpipe is another solution some manufacturers are working on. Of course, this water will need to be kept warm for cold weather climates. This water may also be recycled via electrolysis and run through the fuel cell again. These are just some solutions to the question of what happens to the water in hydrogen cars.”

About Hydro Kevin Kantola

Hydro Kevin Kantola
I'm a hydrogen car blogger, editor and publisher interested in documenting the history and the progression of hydrogen cars, vehicles and infrastructure worldwide.

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  1. Kevin,

    Nice post! This seems to be one of the biggest myths about hydrogen. Thanks for setting the record straight.

    Here are two more sources that echo what you said…

    The U.S. Department of Energy says that:

    “Hydrogen fuel cell vehicles emit approximately the same amount of water per mile as vehicles using gasoline-powered internal combustion engines.”

    Furthermore, this issue was addressed in the Winter 06-07 issue of Earthwise, which is the quarterly newsletter of the Union of Concerned Scientists. Here is the excerpt:

    “Since hydrogen fuel cells emit water vapor (a heat-trapping gas), what impact would a hydrogen-based transportation system have on global warming?

    To compare the potential climate impact of a future transportation system dominated by hydrogen fuel cells rather than fossil fuels, we must consider all of the heat-trapping emissions produced by these two power sources. If gasoline, for example, fully combusts in a vehicle engine, the tailpipe exhaust will contain both carbon dioxide and water vapor. Tailpipe exhaust from fully combusted fuel cell hydrogen gas (H2), on the other hand, will contain primarily water vapor.

    The impact these emissions have on our climate depends in large part on their atmospheric lifetimes. Water vapor remains in the atmosphere only a few days or weeks, and hydrogen gas about two years, but carbon dioxide lingers more than a century. Transitioning to a transportation system based on hydrogen would therefore have essentially no long-term impact on climate due to short-lived water vapor exhaust or minor hydrogen gas leaks, but would dramatically reduce our emissions of long-lasting carbon dioxide-the key factor driving global warming.

    We must be sure, however, that the technology we use to produce hydrogen does not contribute to global warming. Fossil fuel-based production methods would release carbon dioxide (and heat-trapping methane) into the atmosphere, whereas production fueled by renewable energy would not.”

    Greg Blencoe
    Hydrogen Discoveries, Inc.

  2. admin


    Thanks for adding to the discussion and for the links, which are right on target.

  3. About the end of the previous post:
    We must be sure, however, that the technology we use to produce hydrogen does not contribute to global warming. Fossil fuel-based production methods would release carbon dioxide (and heat-trapping methane) into the atmosphere, whereas production fueled by renewable energy would not.

    I have been always concerned that the of clean energy/zero carbon footprint would lead people into thinking that hydrogen cars will run on drinkable water and the tailpipe will produce distilled water. It would be great if you could publish some info about what really an hydrogen fuelcell powered car works as the average person is not aware hydrogen is produced by extracting it from natural gas.
    I am confused myself about some of the aspects of today’s technology to produce or store hydrogen. Some information I found on websites (industrial production of energy through massive on-site fuel cells) show emission of CO2 as well as a byproduct of the production of electricity )

  4. admin

    Thanks for the link to additional information about fuel cells. In regard to production of hydrogen, I place most of this info in the Hydrogen Production category of this blog and you can do a search for “hydrogen natural gas” for more into as well.

  5. Distilled water is in fact more corrosive than naturally occurring water for the exact reason that you attempted to use to disprove the point. Distilled water does not contain contaminates and therefore is more willing to acquire them.

    how bout some better research next time?

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