While public attention is often focused on the emissions reductions that can be achieved in the electricity generation sector, the decarbonisation of heat also plays an important part in meeting the UK’s 2050 energy target of an 80% reduction in greenhouse gases. Nearly half of the final energy consumed in the UK is used to provide heat, with around three-quarters of this heat being used by residential, commercial, and public buildings. The remainder is used by the manufacturing sector.
It was originally planned that the decarbonisation of heat would be achieved via a move to increased levels of heat being provided by electricity while at the same time reducing the Co2 from generation. However, given the high level of heat demand in the UK combined with its seasonality, it is evident that not enough electricity could be generated to meet heat requirements.
As a result, the energy industry has turned its attention to supplying green gas to the grid. There is no actual definition for the term green gas, but it is generally accepted this is gas with a lower level of carbon than natural gas. Defra’s carbon factors show that for each kWh of energy used, natural gas produces 184 grams of CO2e (this compares to an average of 462 grams for electricity).
National Grid is facilitating the injection of biomethane, a renewable gas produced from biodegradable matter such as food waste, sewage, or energy crops, into the gas grid. It sees biomethane as making a significant contribution to heat by 2050, with two commercial projects already operational in Doncaster and Widnes, and others under way. This includes a demonstration plant in Swindon for BioSNG (Syngas) that converts waste to a pipeline quality bio-substitute natural gas. It is widely thought that even if the UK is good at recycling, population growth means there will still be a waste source to utilise for this purpose.
Another method to decarbonise heat is through the use of hydrogen gas, which is carbonfree and is an alternative to natural gas. The Northern Gas Network has received funding from Ofgem to develop the idea of converting the city of Leeds to run on hydrogen for all domestic gas boilers and cookers by 2025-30. Plans are to take methane from natural gas in the grid and convert it to hydrogen by removing the carbon. The existing pipework is already being converted to plastic, which would be required in order to transport hydrogen.
For buildings that are not connected to the gas grid, the use of biopropane as an alternative to LPG is being promoted. The Energy and Utilities Alliance (EUA) has said this would cut annual emissions from the residential LPG sector by 83% by 2025.The Renewable Heat Incentive (RHI), the Government scheme in place to encourage the uptake of renewable heat technologies, has had limited success and is currently under review. While it has encouraged some biomethane injection into the grid, it has not proven to be very successful for the domestic market. As part of the review, it is planned that support for solar thermal will be removed. Its uptake has suffered due to the focus of policy on PV subsidies in recent years. Indications are that support will be designed to promote waste-based biomethane plants, rather than crop-based feedstocks. The consultation closes on 27th April.
Sources: DECC and the Energy and Utilities Alliance