Hydrogen in the North: the H21 Leeds City Gate report launches

From L to R: Mark Lewis, Mark Crowther, Dan Sadler, Alastair Rennie, Mel Tyalor

On Monday 11th July, in a packed-out room at the Institution of Mechanical Engineers, over 200 people had gathered to hear from Dan Sadler, project manager of the H21 Leeds City Gate team, alongside a discussion panel of hydrogen experts. They were there to explain an idea that they hope will change Britain.

That idea is simple, but hugely ambitious. To reduce Britain’s carbon emissions, they want to convert the country’s natural gas network to a hydrogen network. This would use the same pipes as gas and would power cookers and boilers in just the same way, only without the carbon emissions at point of use.

This would be a world-first investment in hydrogen at this scale and the team want to do it in Leeds. Leeds was chosen as the test site for a number of reasons. With 1.25% of the UK’s population, it is a manageable size, while being on a sufficient scale to learn the lessons required for developing a hydrogen network. Leeds is also situated near the existing hydrogen infrastructure at Teesside, and geological salt caverns which are suitable for hydrogen storage.

Despite the technological leap forward the H21 project represents, its proponents stressed the continuity with earlier projects. For the first century of British gas lighting, we used ‘town gas’, a locally produced by-product from burning coal. Town gas contained 50% hydrogen. It wasn’t until the discovery of the North Sea gas fields in the 1960s that the UK committed to natural gas. Switching gas sources required the wholesale conversion of the country’s gas infrastructure:, a ten-year, £100 million project.

So this level of radical change has a precedent and, if our grandparents were able to succeed at such a phenomenal undertaking, there is no technical reason why our era cannot follow. The aim of the H21 launch then was not to prove that a conversion to hydrogen could be done, but that it should be done.

How should it be produced? How should it be stored? How should the network be converted? And how and when should it be scaled up?


The report is firm in recommending steam methane reformers (SMRs), using natural gas as the feedstock. It dismisses bio-produced hydrogen as being too small-scale and renewable-powered electrolysis as too expensive. H21 calculates that to meet Leeds’ demand with electrolysis would require the equivalent of 4-5 London array wind-farm equivalents.

Assuming a peak demand of 732 MW, the H21 team recommend four 250 MW capacity SMRs. There is already one such plant at Teesside. Four plants would be enough to meet demand in winter and some could be shut down through the summer.

This key decision for Steam Methane Reforming means that Leeds would still be reliant on North Sea gas, only transmuted to another form. It also requires an environmental trade-off. To meet climate goals, the plan relies on a CCS system capturing 90% of the direct carbon emissions from hydrogen production. The full emissions are calculated at 269 gm/kWh, which becomes 26.97 gm/kWh with CCS. Adding external emissions for the plant’s electrical requirements, the cost of hydrogen production becomes 49.53 gm/kWh. By comparison, current natural gas emissions are calculated at 184.45 gm/kWh.

By the report’s modelling then, switching to steam-methane reformed hydrogen will still reduce natural gas emissions by 73%. However, as the report admits,

“The assumption of this report has very much been that CO2 sequestration will be available ‘over the fence’ as and when required”.

If the technological timelines do not match up, it would be a major blow to H21’s hopes.


UK gas demand is heavily seasonally-dependent, with winter demand up to six times what can be expected in summer. To take advantage of this, the H21 planners would manufacture excess hydrogen in the summer months and store it for winter. The north-east English coast is built on Permian saltfields and salt caverns have been located near Hull. Salt caverns provide a perfect vessel for storing compressed hydrogen and seven caverns with a volume of 400,000 m3 each have been located in the region. Together they hold a working capacity of 854,000 MWh of hydrogen, sufficient for Leeds’ winter store.

If the UK launched a country-wide hydrogen conversion scheme, storage problems would be faced in other regions which do not have convenient salt caverns. The report does not address this issue. However, as the network grows, the ability to move hydrogen back and forth across wider geographic areas could help balance the supply and demand issues of specific regions.


Britain’s gas pipe network is already undergoing an upgrade, from iron and steel pipes that are not suitable for hydrogen, to polyethylene. However more work would need to be done. The change-over has been meticulously plotted – Leeds will be converted sector by sector, each sector containing around 2,500 households. The full process should take three years, with individual households being without gas or hydrogen for only a few days.

Household appliances will also have to be changed over to meet the standards for the new fuel. This is estimated to cost a little over a billion pounds.


If H21 goes ahead, its planners are already planning the possibility of scaling it up. Maps for the next thirty years showed a hypothetically growing hydrogen distribution network, which would eventually reach London around the year 2050. The price-tag was estimated at £50 billion, end-to-end, for all cities. This could be financed with an extra-rate charge on gas bills, which the Project team say will likely be more than made up for through efficiency gains in coming years.


It was exciting being in that hall, especially after the stressful, uncertain and wet weeks Britain has recently experienced. The leaders on the stage clearly believed that this is not just a chance for Britain, but for the English North to take its place as a manufacturing leader once more. Mel Taylor, with Leeds’ Local Enterprise Partnership, expressed the optimism that has helped drive this project:

“This project has an awful lot of potential to be transformative for the north-east.”

The next move will be up to government. The project will need Ofgem support and an initial £100 million commitment by 2021, if it is to reach the goal of beginning work in 2025. But this report has made it clear that the potential is there.

The executive summary of the H21 report is available at the Northern Gas Networks website here.