Earth heat versus global warming

19 October 2009

"Here might be one of the best hopes for the survival of civilisation"

Why bother with extracting combustibles from underground in order to fuel heat engines for power generation, and saddle ourselves with pollution problems? That is a question sometimes put by engineers lucky enough to get their heat more readily, from subterranean sources that are not substances wanted for burning. Among advocates of such 'geothermal sources' is Professor Nick Jenkins of Cardiff University, UK. He joined others of like mind to deplore the neglect of geothermal energy in the UK.

At a conference of Britain's Royal Academy of Engineers, in London, Professor Jenkins warned the authorities that they would miss their global-warming-prevention targets if they relied too much on wind and other such 'renewable' energy sources to displace fossil fuels.

The conference covered a wide range of technologies, from shallow underground heat-pumping to deep probing of subterranean hot rock, although the British Isles do not offer much opportunity for the latter. The total amount of heat in the earth is vast but mostly not usable. What is usable is still plentiful but crustal - and local, like so many natural resources. Much-exploited geothermal fields can show signs of depletion, as in Italy and New Zealand, but there is believed to be vast potential worldwide.

There are sages who say that overdrawing on regional supplies could cause enough cooling to bring about structural damage. Other sages might (perhaps with twinkling eyes) see terrestrial cooling as a heaven-sent opportunity for direct reduction of global warming.

H Christopher H Armstead - a power engineer of wide international experience, a UN adviser on electrification and a prominent figure in the literature of geothermal energy - wrote (perhaps presciently) in his 1978 textbook* on the subject that it might well become one of the best hopes for the survival of civilisation. He also reiterated his previously published opinion that enormous outlays on space exploration would have been better lavished on 'activities in a downward direction'.

Friend or foe on the farm

Were these two reports juxtaposed deliberately by the environmental editor of one of my favourite business newspapers recently?

The first report told of a well known food manufacturer in the UK. This firm had 'found' that its large intake of milk came from flatulent dairy cows. (The flatulence of cattle, as I cannot resist reminding readers from time to time,† is largely methane, a greenhouse gas much more potent than carbon dioxide.) Conscientiously, the food producer asked its dairy farmers to control their livestock's diet so that less of that digestive wind was passed into the atmosphere.

The second report, placed alongside in the newspaper, was also agricultural. It brought a story of British government effort to persuade farmers that they could beneficially employ anaerobic digesters to process their food-and-feed-wastes, sewage etc and thereby produce (in some cases perhaps collectively) cost-saving methane gas fuel.

The newspaper reader was left to ponder the pros and cons for himself. Some of my readers may remember my light-hearted advocacy of methane as a proper agricultural product, just one part of the output of a farm integrated and optimised for simultaneous processing of foods, feeds and biofuels. Maybe if the idea were presented po-faced in a business newspaper it would be taken up.


*’Geothermal energy. Its past, present and future contributions to the energy needs of man’ by H Christopher H Armstead, published by E and F N Spon Ltd, 11 New Fetter Lane, London EC4P 4EE, UK, and by E and F N Spon, 733 Third Avenue, New York, NY 10017, USA.

†See for example 'Entrepreneurs fight global warming', MPS, Dec 2006, p55. There the text is enlivened by our cartoonist's illustration of a methane harvester. The 'artwork' for this page of MPS is in fact a byproduct of a technical illustrator normally more responsible for something like an MPS wallchart. And, master though he is of the exploded view, his professionalism is evidenced in this instance by the delicacy with which he depicts the methane harvester's bovine efflux.

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