Using local stone is not only inherently ecologically sound, it also helps create the distinctive sense of place so important for attracting visitors to town centres. It is a combination that is keeping customers coming to Forest of Dean Stone Firms.

According to a report by SISTech Ltd and Heriot-Watt University for Historic Scotland, the cradle-to-gate embodied carbon of processed sandstone is 64kg of CO₂ equivalent per tonne (kgCO₂e/tonne). By comparison, the embodied carbon of general building cement is 830kgCO₂e/tonne, facing bricks 520kg and steel bar and rod 1,710kg.

And because of the distances travelled, there is four times more embodied carbon in an Indian sandstone used in the UK than a local one and six-and-a-half times more in Chinese sandstone.

The report is called Embodied Carbon in Natural Building Stone in Scotland, because it was paid for by Historic Scotland, but it also refers to firms in England.

The report goes on to say that there is potential for further reduction in the embodied carbon content of stone by using electricity generated from renewable sources. It says that of the 64kg of CO₂ in sandstone, three-quarters is accounted for by electricity used in the sawing and finishing of the stone, rather than winning it from the quarry. If that could be replaced by non carbon-producing renewable energy it would be possible to reduce the footprint of local sandstone to 15kgCO₂e/tonne.

Forest of Dean Stone Firms, who quarry and process Pennant sandstone in the Forest of Dean, are heading in that direction. They are installing two, German-made Osseberger Crossflow 7kW hydro-electric turbines to make use of a water system built in the 18^th century to power a steel works on the site that their factory now occupies.

They should generate about 70% of the electricity they use following their latest investments that include a new multi-bladed GMM Quadra, one of the first saws sold by Roccia Machinery, the new company established by former Pisani machinery manager Derrick Fretwell who now represent GMM in the UK.

The electricity generated will not go straight into the factory but will be sold to the National Grid at a feed-in rate set for the next three years at 19.9p per kW.

That should earn FoD Stone Firms about £16,000 a year. Allowing £4,000 a year for repair and maintenance costs, they anticipate a pay back period on the £100,000 the hydro-electric plant is costing of eight years four months. The generators should be up and running this autumn.

FoD Stone Firms are selling the electricity to the grid rather than sending it to the factory because their big Terzago block cutter needs 320Amps to get it started, which the two 7kW turbines would struggle to achieve. So would the national grid, of course, so FoD Stone Firms also have hefty diesel generators.

The main reason FoD Stone Firms are selling their green energy to the grid is because they are paid marginally more for it than they have to pay for electricity from the grid. If that changes, the electricity generated by FoD Stone Firms might go directly into their factory – and their investment in the system includes a £20,000 new switch room to handle the three sources of electricity supply.

The feed-in tariff is a new scheme introduced by the government to encourage micro-generation of renewable electricity by providing a guaranteed tariff for it for a number of years. The hope is that, as well as reducing CO2 emissions, this will help achieve enough environmentally friendly electricity to meet increasing demand. The feed-in tariff came into effect last month (April).

Nick Horton, the Managing Director of FoD Stone Firms had hoped to have his hydro generators up and running before then, but Environment Agency concerns meant an elver ladder (for small eels to use) had to be incorporated into the design. There are also automatic sluice-gates to protect the level of the lake feeding the generators, although it will be quite exceptional circumstances that lower the water level enough to stop the generators.

The changes required by the Environment Agency meant FoD Stone Firms had to go back to the planners to amend the permission, all adding to the cost and the time before work could begin.

Planning is never for the faint-hearted, especially when quarries are involved, but Nick has not been put off the idea of using green energy. He is now seriously considering other forms, including sinking water to water heat pumps in the ground to heat the factory.

If predictions of more winters like the last one are right, such a system could really come into its own – temperatures in the factory this year fell to -14ºC, although they had little impact on production.

On the first day of the snow, about half the 32-strong workforce managed to get in. By the third day they had organised their own rota of 4x4 collections and the whole complement was at work. They kept the machines working 24 hours a day to try to stop them freezing up and wrapped the Donatoni paving lines in a heated shelter.

Fortunately there was plenty of work to warrant the production. FoD Stone Firms have opened a second paving line and are reaching the point where they need a third. “We haven’t had a recession,” says Nick, “and I’m sitting on more forward orders than I have ever had.”

Their latest environmental move is to investigate the route of environmental impact assessment and they have been talking to Arup and Bath University about that.

Apart from the straightforward economic benefits of generating their own electricity, demonstrating a low environmental impact has become an important selling point in competing against cheaper imports.

And it is not just on paving that the environmental argument is important. Questions are increasingly being asked of building stone to satisfy BREEAM requirements.

Although natural stone loses out a little in the Green Guide due to the amount of waste involved in stone production, FoD Stone Firms have taken advantage of that on their walling stone because it is made from that waste, thus gaining environmental points.

The environmental advantages of using a local stone, not to mention the local distinction it gives an area, make it easier for clients to justify its use rather than a cheaper, imported alternative.

Nick Horton has lately been explaining these advantages to councils in South Wales, collectively known as the Heads of the Valleys.

The five authorities in these former coal mining areas collaborated with the Welsh Assembly Government to commission a Good Practice Guide by Powell Dobson Urbanists of Cardiff. The report has been presented to each of the authorities and FoD Stone Firms have been involved in those presentations.

The report says it is most important to recognise that the role of town centres has changed and with it the role or urban design.

Once, urban design was about vehicular and pedestrian traffic management, it says. Now there is a clear shift “to an approach that acknowledges the social and place-making functions of streets and incorporates these into the design”.

It goes on to say: “The use of high-quality, indigenous and long-lasting materials is critical for the creation of sustainable and inclusive open spaces.”

Among the projects that have been keeping FoD Stone Firms busy has been the Southgate development in Bath, which the council decided to use as an exemplar project. After that came Swindon, then Hereford. Once a council has decided to use the Forest Pennant, it is much easier for it to make the decision the next time it needs paving. And the more councils that use it, the easier it is for neighbouring councils to decide to use it.

Another USP (unique selling point) for Forest Pennant paving has been FoD Stone Firms’ offer of treating the stone before it is laid. The treatment is applied by QSS UK. It makes cleaning easier, especially the removal of chewing gum (see the previous issue of NSS).

FoD Stone Firms’ landscaping sales have doubled in the past 12 months, helped by the investment made possible by the purchase of a third of the company by Forest Pennant Ltd, one of their biggest customers who established the Royal Forest Pennant brand.

That has enabled Nick Horton to move ahead faster than he thought he would be able to, so that FoD Stone Firms are now three years ahead of Nick’s original business plan. In the past year they have recruited another 10 people, adding another shift to their production.

They are now preparing for a further £1million investment that includes a planning application for an extension of the quarry and the establishment of a paving line in it to reduce handling and, therefore, costs. Their plan is to promote the brand nationally and they have exhausted space available for expansion at their 2.2acre works at Bixslade.