In addition to renewables, natural gas is a well-known and widely available source of energy that can immediately contribute to supporting the energy transition towards decarbonization. Many believe natural gas to be the “bridging fuel” in the transition process towards a new energy paradigm. In fact, in addition to being available in abundance and being widely used and known, natural gas is the fossil energy source with the lowest environmental impact. In addition to producing significantly lower levels of polluting emissions compared to other fossil energy sources, in some cases none at all, its combustion also generates lower amounts of carbon dioxide. For example, one megawatt-hour of electricity generated by a natural gas-fired power plant produces about half the amount of carbon dioxide produced by generating one megawatt-hour from a coal-fired power plant. For this reason, natural gas would be able to achieve a consistent and immediate reduction in CO₂ emissions if it were immediately used worldwide in the electricity generation sector as a replacement for coal.
Natural gas-fired power plants also have other advantages: they have a very high conversion efficiency (around 60% of the incoming energy is transformed into electricity), they are programmable - i.e. they work when needed regardless of external conditions - and they get up to full speed quickly when operated. This makes them ideal to support and integrate the development of non-programmable and intermittent renewable sources, such as wind and solar power, guaranteeing the safety and operational quality of the electricity system. Add the fact that carbon dioxide emissions produced by natural gas power plants can be almost eliminated by capturing them with special systems and storing them underground - Carbon Capture and storage, CCs - and it becomes clear that natural gas can make an even greater contribution to reducing the emission potential of the energy mix. Furthermore, natural gas can be used to obtain hydrogen, a gaseous source of clean energy, which can be burned without causing any emissions of pollutants or greenhouse gases and which is creating great expectations. The process used to transform methane into hydrogen is called steam reforming. This process produces carbon dioxide, which can however be captured and stored, as in the case of electricity generation, using CCs, thus entirely or almost eliminating CO₂ emissions throughout the hydrogen production chain (called blue hydrogen in this case) using natural gas.
The problem of other emissions
Electricity generation and hydrogen production, coupled with CCs, can therefore enhance the role of natural gas in the energy transition, making it even more effective as a decarbonization tool. In this regard, attention should be paid to the problem of fugitive methane emissions from the natural gas supply chain. These are gaseous emissions due to physiological and non-accidental leaks from the sealing elements (i.e. flanges, safety valves, compressors, pumps and regulating valves) of natural gas transportation, distribution and storage systems. Methane, in fact, is also a greenhouse gas which, if dispersed in the atmosphere, has a much greater ability to reflect energy to the ground than carbon dioxide, despite having a significantly shorter permanence time. This argument is often used to deny the advantages of natural gas, although many criticisms refer to data associated with specific and particularly penalizing contexts. In reality, these kinds of emissions - when measured accurately, as recently done by Eni and other oil & gas companies on a sample of plants - turned out to be lower than the estimated values by applying standard coefficients. A study by Imperial College also evaluated the greenhouse gas emissions measured over the entire life cycle of the fuel used at about 300 modern gas and coal plants, comparing the two technologies: the result is that, on average, the level of greenhouse gas emissions per megawatt hour produced by gas plants is half that of coal-fired power plants.
The problem of reducing fugitive methane emissions associated with the natural gas energy chain must in any case be addressed, particularly because it can be solved by monitoring the plants and carrying out regular maintenance work. Many companies, including Eni, have already implemented specific actions for some time to reduce them, achieving excellent results. Numerous initiatives have also been taken by industry associations. Both Eni and other energy companies that have signed up to the Oil & Gas Climate Initiative (OGCI) have set themselves a specific objective of reducing the methane emissions associated with the production, processing and storage of oil and natural gas.
For more information on the objectives and results achieved by Eni in reducing methane emissions (and many others), download the “Eni for 2019 - Long-term carbon neutrality” report from the Eni website. Finally, the objectives, tools and concrete actions taken by the companies involved in the OGCI are extensively illustrated on the website dedicated to this initiative (www.oilandgasclimateinitiative.com).
The author: Giuseppe Sammarco
Natural Resources Studies & Analysis, General Manager Natural Resources.
Read more about gas
Selected content on this issue.