Some householders will be cooking and heating their homes with renewable gas made from sewage, in a £2.5 million scheme which is a first for the UK.
The use of human waste to generate "biogas" and then feed the green fuel into the gas grid is part of efforts to cut the greenhouse gas emissions from heating and cooking in homes.
The project at Didcot sewage works, Oxfordshire, is a joint venture between British Gas, Thames Water and Scotia Gas Networks, and will produce enough renewable gas to supply up to 200 homes, the companies said.
It is hoped that the project will be the first of many to create renewable heat from waste such as sewage, as the UK aims for its EU goal of supplying 15% of all energy, including heat, from renewables by 2020.
It is estimated by National Grid that at least 15% of the domestic gas market could be supplied by renewable gas, known as biomethane, by 2020.
The scheme sees sewage arriving at the Didcot works for treatment, and then sludge - the solid part of the waste - is further treated in a process known as anaerobic digestion in which bacteria break down the biodegradable material and creates gas.
The gas is cleaned before it is fed into the gas grid, in a process which takes around 20 days from toilet flush to being piped back to people's homes.
Anaerobic digestion is already used to create renewable electricity from sewage - with the gas burned to produce power - but this is the first time the biogas has been pumped directly into the grid for use in homes.
Energy and Climate Change Secretary Chris Huhne said: "It's not every day that a Secretary of State can announce that, for the first time ever in the UK, people can cook and heat their homes with gas generated from sewage. This is a historic day for the companies involved, for energy from waste technologies, and for progress to increase the amount of renewable energy in the UK."
Under the proposed Renewable Heat Incentive, which was set to be introduced next April but is currently subject to the Government's spending review, subsidies would be paid for renewable gas being put into the grid.