The boom in natural gas production in the US is leading to a surge in interest in running vehicles on the stuff. In theory, compressed natural gas is significantly cheaper than petrol and emits less greenhouse gases than conventionally powered cars. The California Air Resources Board (CARB) estimates that CNG-powered vehicles produce 20% lower greenhouse gas emissions than gasoline-powered cars. There are other benefits, too, compared with gasoline and diesel powered cars. In an accident, CNG dissipates into the atmosphere, rather than collecting in dangerous pools. Noxious emissions are much lower.
CNG infrastructure and availability is an issue, but there’s an interesting scheme in the US for home refuelling. As far as cars with CNG running capability in the US are concerned, conversions are possible though that is mainly aimed at fleets. For the individual, Honda appears to be leading the way with a factory produced model that runs on CNG and is available to private consumers – the ‘Civic Natural Gas’. It has been joined in the market by CNG versions of the Chevrolet Silverado 2500, Dodge Ram 2500 CNG and 2014 Ford F-150, as well as Chevy Savana vans and Ford Transit and Transit Connect vans.
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More CNG models are in prospect, vehicle manufacturers seeing a growing market opportunity for a fuel seen as plentiful, low-cost, economically advantageous to the US economy and relatively clean.
And on this side of the pond we heard last week about a CNG-powered A3 that has just gone on to the market: the A3 g-tron. It’s only available in Germany to start with, but there is an interesting innovation that allows the driver to be even greener than if simply using regular CNG; they can use a fuel called ‘e-gas’, a specially produced ultra-green synthetic gas. And you don’t even have to use the e-gas to achieve its ultra-green footprint. There’s a clever compensation scheme. If availability of e-gas is an issue when you come to fill up, then simply fill her up with regular CNG and Audi will pump the equivalent ultra-green gas into Germany’s national grid, your ultra-green footprint maintained.
How is this e-gas produced? In the first step, electrolysis takes place using renewably generated electricity to split water into hydrogen and oxygen. The hydrogen could one day power fuel-cell vehicles, Audi points out, but the infrastructure for this is not yet in place. The hydrogen is then reacted with CO2 to produce synthetic methane, the Audi e-gas. It is virtually identical to fossil-based natural gas and can be distributed via the German natural gas network to CNG filling stations for sale.
GERMANY: Audi launches CNG/’e-gas’ powered Audi A3 g-tron
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By GlobalDataI wonder how much the Audi scheme actually costs per unit of gas compared to regular CNG but, it seems to me, you have to applaud the approach. It’s good to see a vehicle manufacturer considering the full environmental impact of the energy provided to the vehicle (a great paradox is at the heart of the electric so-called ‘zero-emission vehicle’, of course, if the electricity is generated at the power station by burning fossil fuels). It will be interesting to see how take-up looks in Germany over the next year.
The Audi e-gas neatly deals with the environmental aspects associated with the fuel in its production, before you use actually use it to power your car. And in this respect, there could be a problem with the way CNG is produced and the volume of methane (a major greenhouse gas that also seeps into the atmosphere via animal flatulence) leaking into the atmosphere as a result. Even small amounts of methane leakage are highly significant, some scientists maintain, because methane is a more potent greenhouse gas than CO2 – as much as 30 times more potent.
A new study published last week suggests that US emissions of methane are considerably higher than previously thought and that leaks from the nation’s natural gas system are an important part of the problem. The study involving scientists at MIT, Stanford and Harvard. They synthesised diverse findings from more than 200 studies ranging in scope from local gas processing plants to total emissions from the United States and Canada.
“People who go out and actually measure methane pretty consistently find more emissions than we expect,” says the lead author of the new analysis, Adam Brandt, an assistant professor of energy resources engineering at Stanford University.
Perhaps surprisingly though, the analysis found that powering trucks and buses with natural gas instead of diesel fuel probably makes the globe warmer, because diesel engines are relatively clean. For natural gas to beat diesel, the gas industry would have to be less leaky than the US federal EPA’s current estimate, which the new analysis also finds quite improbable.
“Fueling trucks and buses with natural gas may help local air quality and reduce oil imports, but it is not likely to reduce greenhouse gas emissions. Even running passenger cars on natural gas instead of gasoline is probably on the borderline in terms of climate,” Brandt maintains.
The natural gas industry, the analysis concludes, must clean up its leaks to deliver on its promise of less harm. Fortunately for gas companies, the study says, “a few leaks in the gas system probably account for much of the problem and could be repaired”. One earlier study examined about 75,000 components at processing plants. It found some 1,600 unintentional leaks, but just fifty faulty components were behind 60% of the leaked gas.
“Reducing easily avoidable methane leaks from the natural gas system is important for domestic energy security,” said Robert Harriss, a methane researcher at the Environmental Defence Fund and a co-author of the analysis. “As Americans, none of us should be content to stand idly by and let this important resource be wasted through fugitive emissions and unnecessary venting.”
So there you have it. Scientists may argue over the findings, but CNG – like all fuels – appears to come with some negatives in its production that require, at the least, further investigation. CNG is, however, undoubtedly a promising fuel source for automotive applications. Audi’s e-gas plant shows that other solutions are possible for enhanced sustainability in the long-run. Right now, it boils down to this: how much does methane gas cost to produce – naturally and synthetically – and what are the true environmental costs involved in extracting gas from the earth? Last week’s study is sure to spark even more debate.
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