A lot has been written recently about the role of natural gas in the decarbonisation of UK energy supplies. Gas is a convenient and ‘clean’ energy source; far better for the environment than dirty fossil fuels like coal and oil. But it still contains carbon and recent research shows that, if we are to limit global warming to well below 2˚C in line with the 2015 Paris agreement, use of gas will need to be all but stopped. This presents us with a dilemma: gas is abundant, there is good gas infrastructure in the UK and we have a lot of gas boilers heating our homes and places of work. It is a cheap, solution that we have already invested a lot of money in.
One can imagine a fully decarbonised electricity grid, but the gas network represents a bigger challenge, and it can perhaps only ever be ‘low-carbonised.’ So does the gas network have a long term future? My view is that we would be wrong to make up our minds on that now because our gas network still has much to offer; it would be a mistake to treat it as part of the problem.
There is a school of thought that natural gas should be prioritised for use in Combined Cycle Gas Turbine (CCGT) power stations to produce electricity instead of Combined Heat and Power (CHP.) This is because a poorly utilised CHP plant (and many of them are) struggles to match the carbon efficiency of the electricity grid. The comparison gets worse as more renewables are added to the electricity grid. Using gas in CCGT also helps to balance the intermittent generation from renewables. Without Carbon Capture and Storage (CCS), however, we cannot use gas in power generation and still keep to our carbon reduction targets.
There are other advantages to phasing out the use of gas in buildings. For example, the requirements for ventilation systems and annual safety checks are reduced. That represents a big potential saving, particularly in social housing. Modern induction hobs provide an excellent alternative to gas cookers, so new flats are often built without any gas supplies at all. That in turn means less gas infrastructure, pipework, trenches and the like. Gas is cheaper than electricity though, so the capital cost of converting existing buildings from gas to electricity is hard to justify.
There are different alternatives to natural gas, depending on the context:
- We can decarbonise Natural Gas, whilst keeping the gas network; using biogas from anaerobic digestion. This is difficult though; the cleaning and pressurisation equipment is very big and expensive. Add to that the changing landscape for waste, which is reducing the potential for viable AD gas yields. Alternatively, CCS could be the solution for decarbonising large gas boilers and heat networks, but the UK has stepped back from investing in the research and project leadership necessary to bring this technology forward at large scale and low cost.
- We could get rid of the gas network; replacing it with modern, low carbon heat networks which have come a long way in recent years. Use of waste or biomass as a fuel has a role in dense urban areas, but here are still problems to overcome with fuel quality and emissions. Heat networks currently account for less than 2% of all heating in the UK, and new projects come on stream very slowly. There is also some potential for heat recovery from industrial processes, but applications are limited to dense urban areas. So can we apply these alternatives across the UK, virtually replacing gas?
- We could rely on centrally generated low carbon electricity for everything. Air source heat pumps can be used to head homes and offices, but they require electricity and they use refrigerant. Widespread use of heat pumps will increase peak electricity demands at busy periods, which are hard to meet with renewable power. Energy storage can overcome the peak demand problem, but we don’t yet have enough large scale options in that area.
So overall there is a range of partial solutions at different scales and levels of maturity, but even when they are combined, they do not have the flexibility of natural gas. Each option needs a substantial investment, yet leaves behind a ‘hard to reach’ energy demand.
We know that technical change will happen and that new solutions will come along, but we don’t know what those solutions are yet. In the meantime there is no sense in basing our energy policy on the assumption that we can do away with natural gas. Rather, I believe that we need to stick with gas, in heat networks, distributed generation and all of the other applications for which we don’t yet have repeatable, low cost alternatives.