Alternatives to Gas
In a domestic context gas is usually used for two things, central heating and cooking. If you are looking for alternatives to gas, perhaps to get out of the grip of rising prices, or to effect a more ecologically sensitive lifestyle and reduce your carbon footprint, then rather than looking at a straight replacement for gas it's necessary to look for alternative methods of doing what you're doing with it.
Direct ReplacementsHaving said that, there are some alternatives, although none are currently mature enough to be easily obtainable. For example, methane can be taken from sources such as closed mines or landfill, but the applications are really only suitable for industrial use at the moment. Generators are transported to the mine or landfill site and plumbed in to provide electricity, which can then be used on site or put into the national grid if there's a suitable installation nearby. Perhaps in the near future this can be adapted to provide a domestic solution.
CookingMany people prefer gas cooking to any other method, serious cooks in particular, because of the instant control it gives over the heat. There are essentially two alternatives for cooking, a range-type stove such as an AGA or a Rayburn, or electric. Electric hobs and ovens are easier to clean than gas ones but if you're trying to change to lower your environmental impact, then the electricity is likely to be generated by coal or gas, or nuclear power, none of which you are likely to want to use if you can help it.
Wood (or other biomass fuel) burning ranges are not as convenient as either gas or electricity to cook on but are considered carbon neutral, as the carbon burnt while cooking is offset by the carbon produced by the fuel while it was growing. Unless you keep a fire going all the time, they take a very long time to heat up to cooking temperature, which makes quick beans on toast a bit of a nightmare, and also means that the stove is on even in the summer. A shift like this is likely to involve quite major changes in lifestyle.
HeatingBiomass is the main contender for alternative heating too, as ranges or biomass burners can have boilers coming off them that can heat water for direct use and for a central heating system. Changing to electricity for central heating is an option but the environmental downsides are still there, unless you can generate sufficient electricity yourself, and electric heating is usually based on storage heaters, rather than radiators.
So a switch from gas to electricity will mean ripping out the radiators and pipes of the current system and living with the inefficiency of storage heaters, which tend to put out their heat during the day, while you're at work, and have lost a considerable amount of heat by the time you're sitting down relaxing in the evening.
A biomass system, on the other hand, can be attached to the existing radiator system so it's a less disruptive change. Depending on your house and heating layout a back boiler can be installed behind a burner in a reception room, where it will give off direct heat and can be a great focal point, or it can be part of a range cooker.