Gas
Of the fossil fuels, natural gas is considerably better than either oil or coal. This is because natural gas, CH4, is partly hydrogen which burns to form water rather than carbon dioxide. It produces about 70% of the CO² compared with oil. However it is still a major polluter and if supply networks are not well maintained and become leaky then methane is a potent greenhouse gas.
On the positive side
- is its ability to burn very cleanly (in terms of particulates), producing little sulphur dioxide and NOx. Also very little ash.
- It can be burnt very efficiently.
- Gas is very storable compared with electricity so it is more efficient at coping with short term variations in demand.
- There is also a considerable future potential for feeding renewable methane produced from land fill sites into the gas supply network and this could supply nearly half the domestic heating needs of the UK if a report from National Grid is to be believed. See this BBC article. (There is of course also the Ambridge scenario)
- There is also potential for the direct gasification of materials such as waste timber and household waste, a technique which has been almost ignored in the UK. See the report by Juniper Consulting
- Furthermore there is the possibility that hydrogen, maybe powered from renewables such as solar or wind, could be fed into a converted national gas supply network in the future.
For the self builder who is on the gas supply network there are a few points to consider.
- Gas requires no on-site storage so this saves on building costs compared with say burning wood.
- Gas boilers are relatively cheap to purchase and easy to install
- Maintenance contracts are reasonably economical
- Combination boilers maintain water pressure through the hot side of the system. This may be useful for showers on top floors (and removes the need for header tank space).
- The Passivhaus design approach has not favoured gas heating. Rather it incorporates electric heating directly into the air supply.
- Co-generation, or CHP, is a possibility with gas and although the internal and external combustion engine approach to this has been slow in taking off, the emerging fuel cell technology for achieving CHP is currently about to hit the market.
