Return to the trees: growing electricity

Every form of generation has its supporters and detractors, it seems. Tom Bawden looks at Britain's biomass generators and what the future holds

The secluded village of Ironbridge in Shropshire has found itself at the forefront of a second industrial revolution – this time in renewable energy. Nestling in the Severn Gorge, Ironbridge's first claim to industrial fame came in 1709 when Abraham Darby, a local ironmaker, invented a way of smelting iron ore with coke rather than using the traditional charcoal method. Replacing relatively scarce wood with abundant coke paved the way for the iron-made building blocks of the Industrial Revolution to be produced on a mass scale.

Now, 300 years later, Ironbridge is doing a U-turn, switching from coal to wood in the next chapter of the renewable energy revolution.

On Saturday, Germany's E.ON will become the latest power producer to convert fully from coal to biomass-fuelled electricity at its plant half a mile upstream from Ironbridge, as utilities across the UK prepare for increasingly stringent emissions targets and new carbon taxes which will close most, if not all, of Britain's coal-fired power plants by 2023.

E.ON follows its German rival RWE's biomass conversion of its Tilbury B power station on the Thames in Essex and a similar move by the UK producer SSE (formerly Scottish & Southern) in Slough.

Meanwhile, the pace of conversions is set to accelerate, with Europe's biggest power station, Drax, near Selby in North Yorkshire, planning to convert half of its generating power to wood chips in a £700m revamp, while the nearby Eggborough station prepares to switch completely to trees.

Together, these plants generate about 11 per cent of the UK's electricity supply, which would make them by far the biggest biomass producers after their conversion. They were encouraged to make the switch to biomass last year after the Government confirmed subsidies for converted coal plants under the so-called Renewables Obligation scheme.

Technically speaking biomass generation relates to a wide range of biological matter derived from renewable sources including wood, other purpose-grown crops and some types of agricultural waste. However the vast majority of biomass generators, especially the bigger ones, will rely on trees. Drax and Eggborough will use woodchips imported from North America.

Like most forms of energy, biomass divides opinion.

"Biomass has the potential to help answer the UK's energy challenges. With many of its power stations being forced to shut down, the question is whether the UK would be missing an opportunity if it did not give biomass more consideration," a bullish Dean Cook, Deloitte's UK sector leader for renewable energy, said in a recent report.

In the opponents' camp, Friends of the Earth's head of campaigns, Andrew Pendleton, said: "Biomass is the last refuge of the scoundrel." He was referring to plans by large-scale biomass plants to import wood from thousands of miles away. This, he contends, in many cases would do more harm than good to the environment. Mr Pendleton is in favour of smaller power plants using trees from sustainably managed local sources where the emissions relating to transport and premature felling of trees can be significantly reduced.

The environmental benefits of biomass vary tremendously according to how the energy is generated. What is clear, however, is that we're going to be seeing a lot more of it. The amount of biomass-generated electricity produced in the UK is set to rise nearly fourfold, from 785 megawatts last year to 2.8 gigawatts in 2016, according to the regulator Ofgem. As a percentage of Britain's total electricity consumption, the change represents an increase from just under 1 per cent to 3.5 per cent over the period. At the same time, coal-generated power use was set to fall by 28 per cent to 17.8GW, Ofgem said. In the past two weeks alone, Scottish Power has shut down its 1.2GW Cockenzie coal-fired station in Scotland and RWE npower its 2GW Didcot A plant near Oxford.

Beyond 2016, biomass has the potential to continue that phenomenal growth rate, analysts say, to the point where it becomes a key component of Britain's energy generation.

"Biomass is a marriage of convenience between the Government and utilities. It works pretty well for both sides," said Harry Boyle, a lead biofuel analyst at Bloomberg New Energy Finance, of the energy source which sits halfway between the old polluting fossil fuels such as coal and gas and clean renewable energy sources such as wind and solar.

For a coal-powered plant, under threat of extinction anyway, a move to tree-based biomass is far more viable than another technology since both work on a similar boiler system – it's just that one burns coal and the other wood.

"It is less controversial than offshore wind, the power station is already connected to the grid and anybody living nearby is already used to the situation," Mr Boyle explained.

Biomass has another key advantage over intermittent wind, sun and hydro power: because it is not beholden to nature, it provides a constant source of energy. But it also has a key disadvantage: it needs fuel. This is expensive, accounting for 80 to 90 per cent of a biomass plant's ongoing costs, according to the engineering company Arup. The fuel also needs to be transported, which costs money and produces carbon emissions. And when it burns, it produces more CO2, albeit in far smaller quantities than either coal or gas.

Drax will import more than 90 per cent of the 7.3 million tonnes of biomass it will need every year because there is not enough in the UK.

At the moment, the majority of biomass generators in the UK are small and able to source almost three-quarters of their feedstock domestically, according to Deloitte. However, most of the new plants will be much larger and will need to import most of their wood, primarily from North America, but also from South America, Finland and Russia.

If all the plants in the planning stage were to actually be built, the amount of imported biomass would increase 30-fold, from 1.3 million tonnes in 2010 to 39.1 million tonnes by 2020, at which point imports would account for about 80 per cent of feedstock.

Sourcing such large quantities represents a huge challenge, as does transporting them. The highly fragmented biomass market makes it hard to secure large quantities of wood on a regular basis, with Deloitte concluding that "larger quantities of fuel need to come to market either under more standardised contracts or shorter-term agreements". Meanwhile, investment in biomass handling, logistics, ports and rail facilities would be critical, Deloitte said.

It is unlikely that biomass will ever be a dominant contributor to Britain's energy needs, but it could none the less prove crucial in helping the country meet its ambitious renewable energy generation targets, and in keeping the lights on in a system set to be stretched to the limit – and possibly beyond – over the next decade. Not as significant as blast furnaces and the Industrial Revolution, perhaps, but Ironbridge could still make another footnote in history as a biomass pioneer.

One big advantage of biomass over wind or solar is that it can use existing coal-fired stations