The Irish government and all the opposition parties are agreed that whatever cuts are made in the state’s current spending due to falling revenues and the threat of recession, infrastructural investment must go on. That’s fine in principle, but most of the projects on the drawing board were developed under business-as-usual, the-economy-will-continue-to-grow assumptions.

They are therefore completely inappropriate for the different world in which they will have to perform.

The world is about to change radically because global oil output is as high as it will ever go and natural gas supplies to Europe are about to fall off a cliff. Consequently, energy will become scarce and expensive in the future, and world economic growth will grind to a stop.

Energy is already becoming the new money. Until recently, if more money went into circulation, more energy could be produced and fuel prices stayed down. Money bought energy. Now, however, there’s no more energy to be had for love nor money. The boot is on the other foot — energy is buying money.

Oil producers are making huge profits and buying into distressed banks. As a result, energy, not money, is the source of commercial, political and financial power.

So from now on, projects should not be assessed in terms of value for money. That’s the old thinking. They need to be assessed in terms of value for energy. To decide, for example, whether the Dublin Port Tunnel was a good project, one needs to calculate how long it will take for the fuel saved by the vehicles using it to equal the amount of energy used in its construction. How much energy would the same fuel have saved or generated if it had been used in other ways?

Every road project in the country would be scrapped if assessed on this basis. Work on the new €2 billion terminal at Dublin airport would stop right away. Metro North, the 17km rail line being built to take the airport’s passengers to the city centre, would be abandoned as well.

Yet ten days ago Noel Dempsey, the transport minister, told the Dail that the Metro North project would be put out to tender and the line would be built “if it is in the budgetary limits we set”. We’ll never know if he keeps his word as the cost of the project has not been published.

Some estimates put the bill at €5 billion, which would make it by far the most expensive infrastructure project in the history of the state — at least three times more costly than the M50 (€1.6 billion) and six times more than the two Luas lines or the port tunnel.

The huge expense relative to the number of passengers it could carry means that Metro North will run at a loss. A study commissioned by Paschal Donohue, a Fine Gael senator, puts the loss at a mind-boggling €22 per passenger journey.

Irish Rail’s proposed 5.2km Dart underground line should be scrapped as well. This is intended to link the Dart line north of Connolly station to the Kildare commuter line at Heuston station, and entails a massive interchange station that will involve digging up about one-quarter of St Stephen’s Green. No costing of this project has been released but its viability is based on the assumption that the number of passenger journeys by Dart and commuter rail will rise from 25m today to a total of 100m.

For much less money — and energy — than either of these grandiose projects, Dublin could build a network of lines for light, self-powered trams.

Unlike Luas, these trams would not be powered by externally-generated alternating-current electricity. They would power themselves. This would save a lot of energy, because Luas needs overhead cables and every street through which it passes has to be dug up to re-route underground pipes and wires. This is to prevent the alternating current inducing dangerous currents in the trams.

A light-tram network could be built for one sixth of the cost of Luas. Each tram could generate its own electricity from a cylinder of compressed methane produced from Dublin’s vegetable waste. Several cities, including Stockholm and Lille, already run some of their public transport in this way.

In a low-energy world, we won’t have the resources to waste on running and maintaining over-specified transport systems. Minister Dempsey needs to think again.

Richard Douthwaite is an economist working with Feasta, The Foundation for the Economics of Sustainability.

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