Month: August 2021

Can Hydrogen Help Us Combat Climate Change? – Examining the Hydrogen Supply Chain

This blog post was co-authored by Dr Semra Bakkaloglu, Dr Jasmin Cooper, and Mr Luke Dubey.

Hydrogen is a low carbon fuel as it produces zero carbon dioxide when burnt and because of this, it has taken centre stage in the fight against climate change. However, a recent publication has raised questions on how effective it is in decarbonising the global energy mix. While it is positioned to replace fossil fuels in the global energy mix, there is growing uncertainty on whether it is as ‘clean’ and ‘green’ as people say it is. Several nations, such as the UK, Japan and Canada, have unveiled their decarbonisation strategy with hydrogen replacing natural gas, in addition to committing to ambitious, world-leading projects to promote it as a fuel in low carbon energy systems. For example, the UK’s recent hydrogen strategy aims for 5 GW of low carbon hydrogen production by 2030 (BEIS, 2021). Hydrogen has the potential to change the way we power our lives and could be critical in combating climate change and achieving net-zero goals.

Currently, hydrogen is mostly used in industrial (e.g. oil and gas refining, chemicals production, fertiliser production) applications and is not an important fuel source (i.e. it is not used in electricity generation and domestic heating). Most of the world’s hydrogen is made from fossil fuels (natural gas and coal) but only a small percentage is made using electrolysis (water splitting in electrolysers). The hydrogen supply chain is not simple. Hydrogen can be produced from a wide range of materials (water, fossil fuels, biomass) and there are numerous technologies available for converting these materials into hydrogen. Because of the complexity in production routes, a colour code is often used when referring to hydrogen.

What colour is hydrogen?

For hydrogen produced from fossil fuels there is:

  • Black hydrogen produced from black coal and the carbon dioxide produced during the process is released to the atmosphere.
  • Brown hydrogen made when brown coal is used to make hydrogen and the carbon dioxide produced during the process is released to the atmosphere.
  • Grey hydrogen made from natural gas and the carbon dioxide produced during the process is released to the atmosphere.
  • Blue hydrogen made from coal or natural gas but differs in that the carbon dioxide produced is captured and stored in underground storage e.g., salt caverns, depleted oil and gas fields.
  • Turquoise hydrogen is produced from natural gas, but solid carbon is produced instead of carbon dioxide.

When hydrogen is produced using electrolysis, the electricity source determines the colour code used:

  • Green hydrogen is when the electricity is from renewable sources (wind or solar).
  • Pink hydrogen is when the electricity is generated by a nuclear power plant- can also be referred to as red or purple hydrogen.
  • Yellow hydrogen is when grid electricity, or a mix of electricity sources (renewable, fossil fuels, nuclear) is used to power the electrolyser. It can also describe hydrogen produced from solar powered electrolysers.

Is hydrogen as clean as we think?

Here at the Sustainable Gas Institute (SGI) at Imperial College London, we have been investigating methane emissions and the importance of this greenhouse gas (GHG) since 2015. Methane is a potent GHG with a global warming potential (GWP)* of 29±11 (Forster et al., 2021) and therefore, reducing the amount of methane in the atmosphere is critical for limiting the impacts of global warming and climate change.

In the atmosphere, methane reacts with hydroxyl radicals (OH molecules) which breaks down methane to carbon dioxide. This is the main sink for methane i.e., the main source of removing methane from the atmosphere. However, hydrogen in the atmosphere will also reacts with these radicals and therefore reduces the amount available to remove methane. As a result, hydrogen is an indirect GHG which means it does not absorb and emit heat but will enhance the warming impacts of methane in the atmosphere.

We know from previous work at the Institute that gas supply chains emit methane and given that hydrogen will likely play an important role in displacing natural gas, hydrogen emissions are likely to occur in a similar fashion. Recent studies have estimated the GWP of hydrogen to be between 1.9 and 9.8 (Derwent et al. 2020, Derwent 2018). Thus, emissions from hydrogen supply chains may pose a risk to net-zero emission targets. This is contradictory to how hydrogen is often portrayed as a silver bullet for combating the climate change. Therefore, understanding where in the supply chain these emissions occur, as well as how much is emitted is vital to understanding its total effect on net-zero targets.

We are also currently modelling hydrogen emissions from a variety of supply chains (local use in the UK, international trade, green and blue hydrogen) to estimate the amount of hydrogen which could be emitted into the atmosphere and the climate change impacts of these emissions. If these emissions are not accounted for then we risk overshooting climate budgets. With so much investment being planned, and many governments’ energy strategies relying on its widespread use, it is imperative we learn more about its potential emissions.

If you want to find out more about our work, please visit our website or contact us at


Global Warming Potential is the a measurement of the heat absorbed by a gas in comparison to the heat absorbed by carbon dioxide. For example, methane has a GWP of 29+/-11, which means 1 kg methane will absorb the same amount of heat as 28+/-11 kg of carbon dioxide.


Derwent, R. 2018. Hydrogen for heating: atmospheric impacts – a literature review London, UK; Department for Business, Energy and Industrial Strategy (BEIS). Available:’

Derwent, R. G., Stevenson, D. S., Utembe, S. R., Jenkin, M. E., Khan, A. H. & Shallcross, D. E. 2020. Global modelling studies of hydrogen and its isotopomers using STOCHEM-CRI: Likely radiative forcing consequences of a future hydrogen economy. International Journal of Hydrogen Energy, 45, 9211-9221.

Forster, P., T. Storelvmo, K. Armour, W. Collins, J. L. Dufresne, D. Frame, D. J. Lunt, T. Mauritsen, M. D. Palmer, M. Watanabe, M. Wild, H. Zhang, 2021, The Earth’s Energy Budget, Climate Feedbacks, and Climate Sensitivity. In: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S. L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M. I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J. B. R. Matthews, T. K. Maycock, T. Waterfield, O. Yelekçi, R. Yu and B. Zhou (eds.)]. Cambridge University Press. In Press.

How should the biodegradable waste management strategy respond to net zero?

In this blog, Dr Semra Bakkaloglu, a research associate at the Sustainable Gas Institute (SGI) for the Methane and Environment Programme, examines how and why the waste sector needs to be overhauled to achieve net zero emissions.

Tractor and landfill
Landfill (Source: Pixabay)

With the COP26 less than three months away, countries are invited to come up with ambitious 2030 emission reduction targets that match the mid-century net zero. The public have also demonstrated their support for sustainability and expressed a desire for immediate action. However, net zero is not possible unless the waste sector is overhauled.

Waste is a global issue. Municipal solid waste generation has increased significantly in recent decades as a result of population growth and urbanisation. The World Bank expects global waste to increase to 70% by 2050 from that generated in 2018. The 1.6 billion tonnes of CO2-eq emissions estimated for 2016 is projected to rise to 2.6 billion tonnes by 2050 (Kaza et al., 2018). Emissions from the waste sector account for about 5% of global greenhouse gas (GHG) emissions (World Bank, 2018). Emissions are primarily caused by disposal in open dumps and landfills without landfill gas collection systems.

The World Bank, Trends in solid waste management.

Methane, which is produced by the decomposition of organic waste, is the largest contributor of GHG emission in the waste sector. It is 28-34 times more potent than CO2 over a 100-year period (Etminan et al., 2016). Endeavours to formalise the waste management can cut GHG emissions substantially. Although the waste sector had a major relative reduction in GHG emissions of 20% over the other sectors between 1990 and 2015 (UNFCC, 2015) due to a number of factors, including improved landfill standards, increase in landfill gas recovery being used for energy, changes in waste type sent to landfill and decrease in food waste amount, further mitigation of remaining emissions is getting tougher.

Waste management strategies have changed recently. With the UK government commitment to achieving “Net-Zero” emissions by 2050, all biodegradable waste will be eliminated from landfill by 2025, with food waste separated from inorganic waste collections (CCC, 2019). Additionally, EU waste legislation will require separate biodegradable collection by 2024, as well as a new target of no more than 10% waste landfilling by 2035 (EU methane strategy, 2020). These rapid changes in the composition of new waste inputs to landfills are changing the landfill gas production rate and composition (Bakkaloglu et al., 2021a). However, in a recent study we demonstrated that biogas plant could be a significant source of methane emissions. Diverting biodegradable waste to anaerobic and composting plants can help reduce landfill emissions and provide sustainable energy, but it may also contribute significantly to methane emissions from biogas plants unless necessary mitigation measures are implemented.

What actions need to take?

Further reduction of emissions from waste sector requires systematic approach, following:

• Cutting down on food waste
• More incentives for the collection and usage of organic wastes or residuals from farming
• More emission measurements on composting and biogas facilities
• Monitoring of biogas plant emissions on a daily basis
• Improvement of leaks caused by poor biogas plant design or maintenance
• Capturing of landfill emissions by effective gas recovery system and topsoil cover materials
• Minimizing the uncertainties in measured emission caused by methodological and meteorological conditions
• Revising the default landfill oxidation values for closed and active landfill sites to improve emission inventories
• Better regulations for monitoring measurements, reporting of emissions by companies and verification of emissions

In order to assess waste management strategies, more research is needed to estimate emissions from the biomethane supply chain and composting facilities, as well as monitor landfill emissions over time.

We can employ our resources, such as food waste, sludge, garbage and even wilted autumn leaves to generate sustainable energy for a decarbonised future. However, further research on waste to biomethane technologies, as well as reliable monitoring and reporting methodologies are essential to achieve net zero goal.


Bakkaloglu, S., Lowry, D., Fisher, R.E., France, J.L., and Nisbet, E.G.. 2021a, Carbon isotopic characterisation and oxidation of UK landfill methane emissions by atmospheric measurements. Waste Management.

Bakkaloglu, S., Lowry, D., Fisher, R.E., France, J.L., Brunner, D., Chen, H. and Nisbet, E.G., 2021b. Quantification of methane emissions from UK biogas plants. Waste Management, 124, pp.82-93.

Etminan, M., Myhre, G., Highwood, E. & Shine, K. Radiative forcing of carbon dioxide, methane, and nitrous oxide: A significant revision of the methane radiative forcing. 2016. Geophysical Research Letters 43, 12,614-612,623.

EU Methane Strategy, 2020. Web page, accessed on 29 July, 2021.

Kaza, Silpa; Yao, Lisa C.; Bhada-Tata, Perinaz; Van Woerden, Frank. 2018. What a Waste 2.0 : A Global Snapshot of Solid Waste Management to 2050. Urban Development;. Washington, DC: World Bank. © World Bank. License: CC BY 3.0 IGO.

Word Bank, 2018. Trends in Solid waste management. Web page : ttps:// accessed on 29, July 2021.

UNFCCC. 2017. “National Greenhouse Gas Inventory Data for the Period 1990–2015.” United Nations Framework Convention on Climate Change.


Book review: “The BOOM” by Russell Gold

‘A nuanced overview of successes, barriers and lessons learned from the American shale gas revolution.’

Our first book review has been written by Pooya Hoseinpoori, a researcher in energy system modelling and policy making at Sustainable Gas Institute, Imperial College London. In this review, she looks at a book that explores the American shale gas revolution. Pooya believes both supporters and opponents of fracking will find this book interesting in understanding the alternative viewpoint.

Over the last decade, the global gas market has experienced significant transformations that greatly impacted traditional gas relations and geopolitics worldwide. With the US shale boom, the growing LNG trade, and the emergence of new gas-producing states, natural gas has become an abundant commodity, and its supply is no longer constrained to regional markets. Among these developments, the American shale boom has had the most profound impact on the abundance of natural gas, reducing gas prices and changing the flow of international gas trades.

Due to the rise in natural gas production from unconventional resources, the United States` energy landscape has transformed significantly in the past decade. By 2010 a combination of disruptive technologies, innovative practices, and an accommodating regulatory environment facilitated the shale revolution, turning the US from a major natural gas importer into a gas exporter. Advancements in hydraulic fracturing, horizontal drilling and seismic imaging were the three main technological advancements that made it possible to extract hydrocarbons from previously inaccessible shale formations and opened vast deposits of natural gas for economic growth in the US. The result was a 50% increase in proved reserve and a 34 % increase in US gas production over the past decade. The shale revolution had a profound impact on greenhouse gas emissions in the US by facilitating the transition from coal to gas. In addition, the abundance of natural gas drove down US gas prices significantly, giving a competitive advantage to its industry. The large-scale extraction of shale deposits has also affected the global oil and gas market and energy security through the growing LNG trading.

Although the shale boom reduced the long-term energy security risks in the US, it has some major environmental risks, making it a controversial technology. Tens of thousands of wells have been drilled across the Unites States and this has led to the growing concerns about the impacts of fracking on ground/surface water resources and local air pollution. Due to the widespread nature of the shale business, it has a large community impact and people are confronted with the process of energy production in a way that they haven’t in the past. This has led to growing public opposition to it. On the other hand, although climate change is part of the shale boom story, many believe that the fugitive emissions from shale gas could offset the emission reduction gains of switching from coal to gas.

Russell Gold is an investigative journalist at the Wall Street Journal based in Texas. For over a decade, he travelled around the United States tracing fracking to drilling sites, farms, companies and interviewed drillers, market analysts, engineers, environmental activists, local residences and landowners to present a comprehensive overview of the shale revolution. In his book, “The BOOM”, he delivers a thorough and balanced analysis into the benefits and disadvantages of fracturing and the growing conflict between economic development, energy independence and environmental damages. I believe both supporters and opponents of fracking will find this book helpful in thinking about alternative viewpoints.

Gold’s book provides important insights into how energy change takes place. In his book, Gold elaborates on how the institutional structure of the United States, in particular private ownership of minerals, facilitated the emergence of fracking and how setting consistent government policies aligned with the right market forces created a fertile ground for the deployment of this disruptive technology. The science and engineering of hydraulic fracturing are well explained. The book also provides interesting information about the history and early fracking attempts, such as using nuclear weapons for fracking.

The Boom is the story of how the coordination of different stakeholders facilitated the biggest energy innovation of the last century. What I liked the most about the book was the interviews with people who were closely involved in this transition and its focus on the human side of adopting this provocative technology. Gold does a great job at capturing the great ambitions and personalities that drove the shale boom. There are the engineers of Mitchell Energy who first figured out how to use chemically slicked water to fracture shales; the investors at Devon who first committed to combine hydraulic fracturing with horizontal drilling enabling engineers to improve the well’s output and make it profitable; Chesapeake’s McClendon who figured out how to finance the revolution and sell it to wall street bankers; the landowner and local residents who had to live with the side effects of fracking and the activists who protested against fracking, trying to force stricter regulations and limit the environmental damages.

Gold concludes by saying natural gas could be a bridging fuel to a future powered by renewable energy and fracking could be the technology that enables that. Despite the consensus on the value of natural gas for reducing urban/regional pollutions, the debate about the role of fracking in addressing climate change and whether natural gas from fracking is net benefit rages on. Being a promising bridging fuel requires further efforts in reducing fugitive methane emissions from the fracking process and gas transport. The other key question is about the future of fracking. Would it deliver the future projected for it? And if shale boom is replicated by other countries and spread globally, how would it affect the energy markets?

Despite the controversial role of shale gas in a clean energy transition, I found the story of the shale boom an interesting account of a change in the energy system and the trade-offs we have to make. I think, as we look ahead to the transition to a low-carbon energy system, there are many lessons we can learn from the shale revolution, including how to create an environment that encourages innovation and enables disruptive technologies to emerge.


  • Gold, Russell. 2014. The Boom. Simon & Schuster.
  • Grigas, Agnia. 2017. The new geopolitics of natural gas. Harvard University Press.
  • Michael Greenstone, Jeff Holmstead, Susan Tierney, interview by Amy Harder. 2018. The Fracking Debate, Energy policy institute at the Univeristy of Chicago
  • Murtazashvili, Ilia. 2016. “Institutions and the shale boom.” Journal of Institutional Economics.
  • Richard S. Middleton, Rajan Gupta, Jeffrey D. Hyman, Hari S. Viswanathan. 2017. “The shale gas revolution: Barriers, sustainability, and emerging opportunities.” Applied Energy 88-95.
  • House of Commons, The Energy and Climate Change Committee, 2012. The Impact of Shale Gas on Energy Markets .
  • European Union., 2013. The Shale gas ‘revolution’ in the United States: Global implications, options for the EU ,
  • Hoxtell, A. G., 2012. The Impact of Shale Gas on European Energy Security, Global Public Policy Institute (GPPi).

Pooya works for the Sustainable Gas Institute at Imperial College which explores the role of natural gas in a low carbon world. Research is  needed to understand methane emissions from the oil and gas industry, and to explore the feasibility of alternative fuels such as hydrogen.