Today’s post is from Clea Kolster, PhD student affiliated with the Centre for Environmental Policy, the Centre for Process Systems Engineering and the Grantham Institute – Climate Change and the Environment. Here discusses COP23, the transition from coal to gas as part of a low-carbon economy and presents three advantages and two setbacks to using low-carbon hydrogen coupled with Carbon Capture and Storage (CCS) to decarbonise the natural gas grid.
On November 17, 2017, the UN Framework Convention on Climate Change’s 23rd COP (Conference of the Parties) came to a close. For the first time in 23 years, its presidency was held by a small developing island nation, Fiji. However, for practical, logistical and mostly environmentally responsible reasons, the two-week meeting took place in Bonn, Germany, instead of in the middle of the Pacific Ocean.
One of the key concerns before COP this year was the effect that the USA’s withdrawal from the Paris Climate Agreement would have on other parties’ engagement. Negotiations went relatively well given the circumstances: China has shown more initiative, and representatives from US states who do not support Trump’s actions such as California, Colorado, Oregon and Washington played an important role in the event. Pushing forward the phase-out of coal was a central point of discussion among attendees of the COP conference – in spite of President Trump’s coal revival viewpoint – with the creation of the “Powering Past Coal Alliance”. The initiative was led by the UK and Canada and now has 20 actors signed up including US states Washington and Oregon (Carbon Brief).
Switching energy consumption from coal to natural gas is a big step to greenhouse gas (GHG) emissions reduction as natural gas when burnt produces approximately quarter the emissions that coal does. A number of countries, including the US and the UK, have already seen a shift away from coal in the past couple decades. In 2000, the US energy consumption by source was about the same for natural gas and coal but in 2017 natural gas provided 29% of energy consumption while coal only provided 15% (US EIA Monthly Energy Review). Worldwide the supply of coal as primary energy still exceeds what is provided by natural gas as it does for electricity generation, but this is also shifting.
Natural gas has a number of end-uses including electricity generation, heat production for domestic and commercial use in buildings and industry. While natural gas is better than coal in terms of carbon intensity it still needs to be decarbonised and in 2015 accounted for 20% of carbon dioxide (CO2) emissions from fuel combustion (IEA Key World Energy Statistics 2017). In light of today’s ambitions to avoid dangerous climate change and limit global temperature rise to “well below 2°C ”, bringing emissions down to net zero before the end of the century, decarbonising the gas grid is vital.
Earlier this year, the Sustainable Gas Institute at Imperial College London released a white paper titled “A Greener gas grid: what are the options?” The report presents options for reducing the carbon intensity of our gas networks and the relevant feasibility of each of these options.
One of the key options discussed in this report is to switch from using methane (CH4) which is the main component of natural gas to using hydrogen (H2) as a primary energy source in the same way we do natural gas. The most common method used to produce hydrogen is by reacting methane with steam (H2O) through a process called steam methane reforming (SMR). A by-product of this reaction is carbon monoxide (CO) and this reacts with water through a process called water-gas-shift producing more hydrogen, but also carbon dioxide (CO2). In order to ensure that this process is actually “decarbonised” the CO2 is sequestered using CCS. CCS captures and stores CO2 in well characterised, deep geological reservoirs kilometres below the surface where it is highly unlikely to ever escape.
Combining the production of hydrogen with CCS to decarbonise the gas grid provides a promising pathway solution to a decarbonised economy and like all other potential pathways, it will have its pros and cons.
Advantage #1: Lower Sunk Costs
There has already been huge investment worldwide in natural gas infrastructure. Replacing natural gas with hydrogen would mean we could take advantage of the millions of kilometres of low-pressure gas networks (i.e. distribution networks) in place today. We would only need to make minor adjustments to distribute hydrogen at a small cost relative to the total system costs. Since 1938, over 3000 km of hydrogen pipelines have already been constructed in Europe and North America. Retrofitting using hydrogen makes sense particularly for the US, UK, Japan and the Netherlands who have the most developed gas networks (just below 3,000,000 kilometres in total with 2,100,000 in the US alone). For other countries with less than 50% of gas demand connected to a pipeline network, this could be the right time to develop their infrastructure so as to be able to transport hydrogen as well.
Advantage #2: Valuable Storage
Gas networks are inherently flexible and respond well to daily and seasonal variations in demand, providing long-duration energy storage. Replacing natural gas with hydrogen could maintain that flexibility at a much lower cost than electricity storage and combining its production with CCS would make it cleaner. Plastic pipework and lined steel is typically required for transporting hydrogen and best at low pressure, which has the added benefit of making the gas network’s storage capabilities safer.
Advantage #3: Carbon capture and storage (CCS) is a well understood and developed technology.
CCS is well suited to decarbonise the production of hydrogen from natural gas. Seventeen commercial CCS plants are operating today, two of which are power plant retrofits (Boundary Dam in Canada, Petra Nova in USA) and one CCS plant is already used for hydrogen production (Quest in Canada) (Global CCS Institute). Several more are in construction or at demonstration phases. CCS is recognised as being part of a least cost climate change mitigation solution and remains the only means to fully decarbonise the industrial sector. Considering the need for CCS with hydrogen could further accelerate the deployment of large-scale CCS. Progress is already under way: Statoil, Vatenfall and Gasunie signed a Memorandum of Understanding to evaluate the conversion of the Magnum gas plant in the Netherlands to a hydrogen plant with CCS. This has the potential to reduce CO2 emissions by 4 million tonnes per year equivalent to the emissions from 2 million internal combustion engine cars.
Setback #1: A Tricky Conversion
Hydrogen has been transported via low pressure pipelines for almost a century [PDF], but this has for the most part been at concentrations at or below 20%. Limited experience exists with transporting 100% hydrogen over long distances, so appropriate precautions need to be taken when converting natural gas pipelines to handle such high levels of hydrogen. Pipeline conditions (particularly pressure levels) need to be kept under control in order to avoid hydrogen embrittlement which takes place at high pressures. This can lead to fractures in the material, cracks in the pipeline and leakage. Leakage of high concentrations of hydrogen can become flammable and is a safety hazard (Dodds et al. 2013).
Setback #2: Money, Money, Money
In addition to the infrastructure and conversion costs required for the transport and distribution of hydrogen, CCS today remains very capital intensive and draws the attention of a variety of sceptics. However, developers of large-scale CCS plants such as Boundary Dam, built in 2015, are learning fast and already know how to a build a cheaper and more efficient second plant. Technological learning, but also monetary incentives such as high carbon tax and revenue from streams of CO2 utilisation, will drive the cost of CCS down to a more sustainable level.
Other solutions to greening the gas grid do exist and are explored in more detail in the Sustainable Gas Institute’s third white paper. For example, replacing natural gas with bio-methane via the gasification of biomass to produce hydrogen coupled with CCS is an option and can generate much needed negative emissions. Producing hydrogen through electrolysis from renewable energy not requiring CCS, though less developed, is also an option.
All solutions will have their advantage and setbacks and certain solutions may work better in certain regions rather than others. It is vital to evaluate these options soon in order to make headway on reducing the impact of our energy consumption on the planet. Scientists also need to continue to work with policy makers to communicate with the wider public and adopt the most techno-economically sound solutions.