Car manufacturer Honda tell us that

If you could read our minds, you’d see dreams of a greener and more environmentally sustainable world.

Judging them not by what we telepathically perceive but by their actions in the external world, we find quite a different picture.

Yesterday it was announced that Honda have begun limited commercial production of the FCX Clarity, their hydrogen powered car.

Over and over and over and over again we’re told that it is ‘zero emission’. This is true in the sense that the only emission from the car itself is water vapour. However, the car is responsible for considerable carbon dioxide emissions – as much as a petrol car.

This is because the nice clean hydrogen has to come from somewhere, and that involves a lot of fossil fuels. The cheapest and most common source is natural gas. It can also be made from water by electrolysis, using an electric current to split water’s hydrogen and oxygen components.

Here’s the maths

Honda say the FCX Clarity does 57 miles on 1kg of hydrogen. Let’s get that in metric; 57 miles is 91km.

Manufacturing hydrogen from natural gas emits 9.1 kg CO2 per kg of hydrogen.
[IPCC Special Report on Carbon Dioxide Capture and Storage, Cambridge University Press, 2005, p 131]

9,100g divided by 91km = 100g/km to make the hydrogen gas from natural gas.

Electrolysis requires 39 kilowatt-hours of electricity to produce 1 kilogram of hydrogen.
[Wind Energy and Production of Hydrogen and Electricity — Opportunities for Renewable Hydrogen, US National Renewable Energy Laboratory, March 2006, p2]

That electricity is made from a variety of sources, predominantly fossils. UK grid CO2 emissions are 480g/kWh.
[Fuel Mix Disclosure Data Table, DBERR 2006-07, table 3]

480g x 39kWh = 18,720g/CO2 per kg hydrogen.

18,720g divided by 91km = 206g/km to make the hydrogen gas from electrolysis.

But it’s not over, because at this stage all we’ve got is hydrogen gas. This has about one three-thousandth of the energy density of petrol. Assuming you’re not going to have a fuel tank a few hundred times the size of your car, you have to shrink it. It has to be either cooled to a liquid, or else it has to be compressed. Honda use hydrogen compressed to a pressure of 5,000psi.

It takes 2.6-3.6 kilowatt-hours of electricity to compress 1kg of hydrogen to 5,000psi.
[Raymond Drnevich of major American hydrogen supplier Praxair, Hydrogen Delivery: Liquefaction & Compression, May 2003, p14]

2.6-3.6kWh x 480g/kWh = 1248g-1728g CO2 emissions per kg hydrogen.

1248-1728g divided by 91km = 14-19g/km for compression.

Here’s the totals

100 + 14-19 = 114-119g/km for compressed natural gas hydrogen

206 + 14-19 = 220-225g/km for compressed electrolysis hydrogen

To compare, the current petrol powered Honda Civic emits 135g/km, a Toyota Prius emits 104g/km, a Renault Megane emits 117g/km.

As David Talbot from MIT’s Technology Review said of BMW’s Hydrogen 7 vehicle

a car like the Hydrogen 7 would probably produce far more carbon dioxide emissions than gasoline-powered cars available today. And changing this calculation would take multiple breakthroughs – which study after study has predicted will take decades, if they arrive at all. In fact, the Hydrogen 7 and its hydrogen-fuel-cell cousins are, in many ways, simply flashy distractions produced by automakers who should be taking stronger immediate action to reduce the greenhouse-gas emissions of their cars.

The sleight of hand that passes the emissions to the fuel factory and has people calling the FCX Clarity an ‘eco-car’ is unsurprising. If we want to know how corporations will treat carbon accounting, look at how they presently perform tax accounting.

The FCX Clarity is a decoy, deployed by people who surely know about the emissions they’re responsible for. The car manufacturers can see no way of reducing their emissions that won’t similarly diminish their profits.

As the petrol/diesel car is widely understood to be unsustainable, car makers have to offer the hope of an alternative; not so far off that we feel there’s a problem to worry about, but not so imminent that they’ll actually be held to account for failing to do it nor make anyone question why they’re still developing new oil-fuelled models.

Honda are only leasing the FCX Clarity. There are perhaps many reasons, but I can’t help suspecting that chief among them are that it’s too expensive to sell and they want the cars back before they break.

In December 2002, Yozo Kami, Honda’s engineer in charge of hydrogen fuel cells, said it would take at least ten years to get the price of a hydrogen car down to $100,000 (£50,000).

Fuel cells of the type used in cars (proton exchange membrane cells) have a short lifespan. The industry is aiming at around 4,000 hours of use, which might equate to ten years of driving. As it stands, a good prototype can only manage about 2,000 hours. Buying a car that costs £50,000 and is guaranteed to need major engine work within five years isn’t going to appeal to anyone.

Hydrogen as a vehicle fuel is thoroughly impractical, prohibitively expensive and, most importantly, does nothing to reduce carbon emissions. On the contrary, it would significantly increase them.

Honda might be able to kid journalists into thinking that hydrogen cars are ‘zero emission’ but unfortunately they can’t fool the climate.