By Roger Harrabin

BBC News environment analyst

Gas from waste creates less pollution than incineration, says the report Gas from waste could heat almost half the homes in the UK, according to a new report from National Grid. It says obtaining more gas from waste will help cut carbon emissions, improve energy security and compensate for the shortage of landfill sites. Renewable gas from landfill sites and sewage works provide 1% of the UK's gas at present. Today's report says an extra £10 billion investment could increase that to between 5 and 18%. The cost would be similar to that of other forms of renewable energy. 'Over-optimistic' It says biogas could deliver up to two thirds of UK renewable energy targets by 2020. Critics believe the report is over-optimistic and seeks to capitalise on National Grid's control over the UK's gas pipelines. Today's report will contribute to the growing debate about heat, which produces 47% of the UK's CO2 emissions - much more than electricity or transport. The government will soon launch a consultation on a heat strategy. Renewable gas is currently obtained through anaerobic digestion (microbes) or by super-heating waste to drive off the gas. The report says both these processes create much less pollution than incineration. The low carbon agenda needs another silver bullet like a hole in the head

Graham Meeks

Combined Heat and Power Association Renewables subsidies mean renewable gas is currently used to generate electricity. But the report says this is much less efficient than using the existing gas grid to pipe the gas to heat homes. The report says there are no insurmountable technical or safety barriers to delivering the gas, as the technology is already used in many other countries. The key to delivery is government policy, including: A commercial incentive for producers to inject "green" gas into the grid rather than generating electricity

A strategy to ensure each waste stream goes to the most appropriate technology to maximise energy recovery and recycling

A change in the rules about the amount of oxygen allowed in gas pipes

Continued support for research and development of renewable gas. "As we look forward to 2050," the report says, " it is important to recognise that delivering 80% emissions reductions is going to require a very sizeable contribution from heat which only renewable gas is able to deliver without significant inconvenience to consumers and other residents of the UK." Lower bills National Grid says the beauty of renewable gas is that it utilises existing infrastructure. Competing technologies like combined heat and power, or CHP, require new pipes to deliver the heat. The report says instead of transporting wood chips by lorry to be burned in CHP plants it would be more efficient to gasify the wood chips and then transport the gas. Will homes be heated using gas waste from landfill sites and sewage works? Renewable gas is slightly less powerful than gas from fossil fuel but the report says consumers could be compensated through lower bills. Critics point out that reliance on renewable gas locks the UK into a high-waste economy when the government is urging people to waste less. Gas heating also allows less flexibility than electric heating which allows the heat in each room to be programmed easily. Methane leaks could also be damaging - the greenhouse gas is more than 20 times more powerful than CO2. Graham Meeks from the Combined Heat and Power Association said: "Renewable gas has an important role to play in the decarbonisation of the economy, but on its own it is no panacea. The low carbon agenda needs another silver bullet like a hole in the head. "Any suggestion that this could displace the need for technologies such as district heating is extremely unhelpful. In fact district heating and CHP are the perfect complement to renewable gas production."



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