Turning off the gas: decarbonising heat in the UK

Following Extinction Rebellion protests in London this April, the UK Parliament has now passed a motion calling on the government to declare a climate emergency. The Environment Secretary has accepted that “the situation we face is an emergency”, and while the government hasn’t formally made the same declaration, it has acceded to Parliament and the protester’s main demand: a commitment to reaching net zero carbon emissions, although the target date is 2050, when the protesters were calling for 2025.

Westminster and public opinion seem to be aligned. According to a Greenpeace poll, two-thirds of UK residents say they recognise there is a global climate emergency. The political climate is therefore one that might actually allow for otherwise controversial policy changes that are desperately needed. However, there is a major barrier to decarbonisation, one that is rarely mentioned in the popular discourse, and where the public appear reluctant to embrace change: the UK’s reliance on natural gas for heating.

BEIS estimates that, in 2016, 37% of UK carbon emissions were attributable to heating – compared with, for example, 27% from transport, the next largest contributor. Energy efficiency improvements to reduce heat loss from UK homes have a massive contribution to make, and could reduce the scale of the challenge faced. But we will still need heat, and that needs to be decarbonised. Achieving this will entail a level of societal and technical change not yet seen in our efforts to avoid a climate catastrophe. So, how might it be done?

Having a gas

The UK’s efforts to decarbonise have, so far, been aimed at the low hanging fruit: predominantly, decarbonising electricity generation when aged coal fired power stations were in any case reaching the end of their lives. For most people, this change involves minimal disruption, especially as the costs of renewables have tumbled. However, heating in the UK currently relies heavily on natural gas, which (being a hydrocarbon) is always going to result in carbon emissions when burnt for fuel.

Prior to the 1960s, the majority of housing in Britain was heated by open coal fires, and typically only a few rooms in each home were heated. The conversion from town gas (manufactured from coal or oil) to methane during the 1960s and 70s was a huge technical and social change – and corresponded with householders increasingly expecting to have effortless, whole-house heating.

Gas central heating became the norm, fuelled by the discovery of natural gas in the North Sea. As a consequence of this transformation, the UK is currently second only to the Netherlands out of OECD countries in terms of natural gas fuel share for residential and commercial heating (both are over 80%).

The Government has already announced that from 2025, new homes won’t be able to have gas boilers. The far bigger and more disruptive decarbonisation challenge is to adapt all of the 20 million or so homes currently on the gas grid – as well as those using oil central heating. Just how much disruption this involves will depend upon the technology or fuel source we choose to replace natural gas, and at present there are two main contenders.

Unnatural selection

The first is the electrification of heating, whereby gas boilers are replaced by heat pumps – primarily air source heat pumps (ASHPs). Similar to an air conditioning unit, a heat pump is fitted to the outside of a property and extracts heat from the air, using similar technology to refrigerators – but in reverse. Rather than burning fuel to create heat, they simply transfer heat from one place to another: from the outdoor air into the heating system, and then from the system to the home.

While ASHPs are electrically efficient and very sustainable, their major disadvantage is that they don’t generate intense heat. They therefore work best when connected to underfloor heating in well-insulated homes – a previous Isonomia article examined some of the challenges of retrofitting them to older homes. There are also a number of questions around how the transition might be achieved, in terms of cost and practicality. These will need answering before any major infrastructure project can go ahead.

The second option for decarbonising heat is to replace natural gas with an alternative such as hydrogen. This is not as simple as it sounds: it may require renewing large sections of the gas grid with new plastic piping (exposure to high-pressure hydrogen can make iron and steel pipes, used in older and high-pressure sections of the grid, brittle) and people would certainly need new types of boilers. Still, the disruption involved would be much less than that associated with installing ASHPs. However, it brings a substantial hurdle of its own, which is the question of where the hydrogen gas would come from.

One possible solution is to rely on hydrogen gas being obtained as a by-product of the deployment of carbon capture and storage (CCS) in manufacturing industries. The capture process would strip hydrogen out of captured emissions at the same time as carbon dioxide. The result would be that, for the first time, energy would be dependent upon manufacture, rather than manufacturing depending on energy. However, setting aside concerns about whether effective, affordable CCS is achievable, there are serious questions around the consequences of this change in power dynamic, and the ability of such a system to deliver an agile economy.

Another problem with this approach would be the need for an extraordinary amount of co-ordination. The gas grid can only carry one gas at a time, so if it were to be repurposed for hydrogen, everyone (at least within a particular area of the distribution network) would need to switch to hydrogen at the same time – presumably during the summer, when heat demand would be low. So, while a hydrogen-based heating system might entail less disruption to a person’s home life than switching to heat pumps, its implementation certainly wouldn’t be without difficulty – both domestically, and perhaps for the wider economy.

So, both of these key options would, in their own ways, be hugely disruptive – and potentially hugely unpopular. Whichever heating technology comes to dominate, the UK’s varied housing stock means that a blend of technologies is likely to be needed.

Hot topic of conversation

Whatever the technological solution, climate science tells us that in order to achieve net zero carbon by 2050 we need to have stopped using natural gas by the 2040s. To do this, we’ll have to start the transition in good time within the 2030s, which means that policy makers must start planning for the change in the 2020s. Therefore, within the next 10 years a UK government is going to have to make some very hard decisions.

There is an urgent need to start a frank discussion about the feasibility of the options for decarbonising heat in line with emissions reduction targets, while at the same time ensuring that the improvements in domestic heating hard won in the twentieth century are not lost. For vulnerable groups in particular, an effortlessly warm home is an essential requirement for health.

That conversation needs to start from an understanding of how best to communicate the issues to the public. A citizen’s assembly on climate change action has already been announced, in which a random selection of citizens is presented with the facts and asked for preferred solutions. This might provide a politically palatable way of gaining support for tough, necessary decisions to get politically controversial policies over the line.

Right now, with rising recognition of the climate emergency we face, both from politicians and the public, looks like the ideal time to start the debate about decarbonising heat – the nation’s climate ambitions depend on it. Delaying this crucial element of the debate could cost Government its best chance to secure acceptance of the change that has to come.

Featured image: Nolf (public domain), via Wikimedia Commons