The gas network can be at the centre of a future integrated, low-carbon energy system.

I’m not sure where the idiom “killing two birds with one stone” comes from, but I do know that for years gas has played that role – providing flexible power generation and also affordable, secure heat to our homes. And for the future, gas can also do two more things at the same time. Before I explain, let me set the context.

For those who travel to London frequently and have picked up an Evening Standard for the train journey home, you cannot have missed its campaign over poor air quality. Tenacious reporting by the likes of Nic Cecil means the issue has fresh legs each day. And so it should. In the UK around 40,000 deaths a year are attributed to poor air quality. London MPs are worried about the impact in their constituencies. The government is losing court cases because of its failure to act. The new London Mayor pledges action and the BBC broadcasts a series all about the air we breathe.

The problem of poor air quality is immediate. It can’t wait until 2050 for action. It is also a localised problem, not a global one, and it is primarily associated with dirty diesel engines pumping out emissions in built-up areas. It isn’t just a London issue.

While there is an interesting debate over the future fuel for cars – electric or hydrogen fuel cells – batteries cannot power large vehicles such as heavy goods vehicles (HGVs) and buses with any degree of effectiveness. So do we carry on using diesel, polluting our streets as well as the planet, or can gas “kill two birds”?

HGVs contribute 17 per cent of the UK greenhouse gas (GHG) emissions from road transport; about 21 per cent of road transport emissions of NOx while travelling around 5 per cent of vehicle miles and accounting for less than 2 per cent of actual vehicles. Their disproportionate environmental impact suggests it is an area ripe for action.

So how can gas kill both birds – carbon emissions and poor air quality?

Recent government-backed trials comparing new diesel Euro 6 engines with dedicated gas equivalents found that a gas-powered Euro 6 emitted an average of 41 per cent less NOx than the best diesel and 74 per cent less NO2. While the carbon savings were only marginal, on a tail-pipe basis, when compared to well-to-wheel emissions they were significant. And this is comparing the best diesel on offer to gas. If we look at the existing vehicles stock, we can see why air quality is an issue. A Euro 6 diesel (post-2014) has a NOx emission target of 0.4g/kWh but older vehicles have 2g/kWh (Euro 5 – 2009) and 3.5g/kWh (Euro 4 – 2006). So if gas easily beats the best Euro 6 diesel, it is simply miles cleaner than Euro 5 and 4.

But gas can be even better. Using biomethane dramatically improves the carbon emission performance of gas-powered HGVs. Looking at the early results of dedicated biomethane HGVs, using compressed natural gas (CNG) filling stations, carbon savings in excess of 60 per cent are being achieved. Given that transport GHG emissions have barely changed since 1990 (down just 2 per cent), the government needs to pay more attention to the role of gas. It’s great that the fuel duty differential is fixed for a number of years, incentivising gas over diesel. But a little support around filling station infrastructure would go a long way to nudging fleet managers in the right direction.

Finally, we need to get the gas around the country. If only there was some form of piped system, roughly matching areas of population or travel patterns, that could be relied on and was cost-effective, that could transport all that gas. Did I ever mention that the gas network can be at the centre of a future integrated, low-carbon energy system?

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