A giant chemistry set on the Firth of Forth

On the banks of the Firth of Forth, the Longannet power station dominates the wintry horizon, a massive box in the shadow of its skyscraper chimney stack.

Conceived more than 40 years ago and completed at the beginning of the 1970s, long before climate change became a central tenet of the energy debate, Longannet was designed with stunning industrial simplicity and symmetry.

Britain's second-largest coal-fired power station was a product of a time when electricity generation was based on a technology now dismissed by modern engineers, not entirely without affection, as "burn and boil". You burned the fossil fuel, and used the heat to boil water, which drove the turbines to generate electricity.

Today, Longannet is at the centre of its owner ScottishPower's plans to demonstrate there is more to coal than burn and boil; that despite opposition from environmentalists, it has a future in providing Britain and other countries with a key component in the pursuit of energy security, affordability and sustainability, and is not, as some critics argue, a 19th-century nightmare haunting the 21st century.

In trying to make Longannet a centre for technological excellence, ScottishPower is turning it into a giant chemistry set. More than 1,000 contractors are putting the finishing touches to flue gas desulphurisation (FGD) equipment in three of the plant's four turbines.

Fitting FGD brings Longannet into line with the European Union's large combustion plant directive on reducing sulphur dioxide emissions. Without FGD, it would run for only limited hours, and would have to close in 2015.

Life extension does not come cheap. According to John Campbell, director of energy wholesale at ScottishPower, the company is investing about £170m in FGD, while associated investments to extend the plant's life have lifted the bill to £250m.

The scheme does have local benefits. Last year ScottishPower signed a five-year deal, worth up to £700m, with Scottish Coal to provide coal for Longannet and its smaller coal plant at Cockenzie.

At the time the deal was signed, Ignacio Galán, the chairman and chief executive of ScottishPower's Spanish parent, Iberdrola, made clear his ambitions for coal and Longannet: "Coal generation has a significant contribution to the security of electricity supply in the UK today."

The next stage is to fit Longannet with equipment to reduce emissions of nitrous oxides (NOX) to conform with impending legislation. The process uses ammonia and a vanadium pentoxide catalyst to turn the NOX into water and nitrogen. Fitting the equipment will cost "several hundred million pounds" and require greater political clarity, according to ScottishPower executives. Work is also under way on a 25-mega­watt biomass plant, using wood chip, peanut husks and dried waste.

The big issue, however, is carbon capture and storage (CCS). For fossil fuel burners, this is a kind of holy grail, though one not yet available on a commercial scale. The theory is simply: carbon dioxide is collected, transported and buried in holes in the ground.

The government is keen, and is running a competition to encourage the development of CCS. It could help the UK cut emission levels and be sold to power generators around the world.

But as Ed Miliband, the energy and climate change secretary, said in a speech last month, CCS is vital to reconciling the continuing use of coal with Britain's emission targets.

He told a conference at Imperial College London: "Clean fossil fuels are a less sure prospect because of uncertainties around carbon capture and storage, the great prize of clean coal and gas.

"What is clear is that we cannot say that in 20 years' time we will be building unabated coal-fired power stations and that we will meet our carbon budgets. It's not credible," he said.

It is a view that ScottishPower and Iberdrola appear to accept. As Galán said last year: "Iberdrola is committed to developing the best technologies that will deliver low-carbon generation in this country.

"Through our existing co-firing capability of biomass with potential advances in carbon capture and storage technologies, we are ready to provide the flexible generation needed to support the UK's growth goals in renewable energy and at the same time ensure security of supply."

If he gets his way, and if CCS does prove commercially viable, Longannet will brood over the Firth of Forth for some years to come. Some might say that is a big if; it will certainly be an expensive one.