Grainger Sawmills Ltd’s search for a new boiler to heat its increasing number of kilns resulted in a much more significant purchase – a biomass-fuelled combined heat and power plant (CHP).

This groundbreaking development has meant that, not only does the Enniskeane, Co Cork-based sawmill have a plentiful supply of hot water at a fixed cost, it also has a guaranteed market for its low-grade residues, protection from spiralling energy costs, a new revenue stream from ‘green’ energy which is sold to the National Grid and the satisfaction of knowing that it has reduced lorry journeys from the sawmill by no fewer than 1,500 per year. In one neat move it has accomplished the company’s two main strategies which, according to director Niall Grainger are “to add as much value as we can to the timber we process and to keep our cost base as low as possible”.

The hunt for the new boiler had led Mr Grainger to Finland where he came into contact with a leading player in the biomass sector, Wartsila Biopower. Grainger, which had always been open to investing in new technology, then struck up a partnership with another west Cork-based company, SWS Group, a market leader in the natural resource and energy sectors, in order to investigate the possibility of replacing the sawmill’s old boiler with a CHP plant fuelled by its own products.

The synergies between Grainger, which had expertise in construction and boiler technology and SWS, with its track record in renewable energy, led to the development of a joint venture company, Independent Biomass Systems (IBS). It was this company, with Wärtsilä as the turnkey developer, that saw the project through from concept to commissioning within a 12-month time frame.

The plant, which Mr Grainger describes as “very simple, just a big plumbing job”, comprises a covered fuel conveyor to transport material to the plant, a fuel storage area and a steam boiler coupled to a turbine to make heat and electricity.

However, it’s the software wizardry behind the gleaming pipework that makes the system so special – and so cost-effective.

The plant runs 24/7 and is overseen by a single operator. The system allows the operator to “dial up steam or dial up electricity” and its chief claim to fame is its variable output extraction turbine which significantly improves its efficiency and which, Mr Grainger said, “is one of the first of its kind”.

Variable output

“In the winter when we’re drying more and need more heat, we generate less electricity and in the summer, when we need less heat it will generate more electricity. In the past, all turbine systems that have been put in, both gas CHPs and biomass CHPs, have been fixed output. We are at the forefront of technology.”

Grainger Sawmills is still selling its more lucrative wood chips to the board mills, but is now burning all its low grade residues. It expects to have a shortfall of between 7,000-10,000 tonnes per year but this is part of the game plan. There is a huge surplus of low value residues in Ireland for which there is now an extra outlet – and one which has had companies travelling from a 100-mile radius to knock on Grainger’s door. And, as Niall Grainger said: “Knowing they have an outlet for their peelings or bark is an encouragement to increase their output. It’s a continuous process”.

The CHP project has been so successful that IBS is now in the market to offer its expertise to other companies in Ireland and the UK. “Having been through the entire process I’m only too familiar with the concerns that many sawmills may have,” said managing director William Grainger. “But it’s achievable and probably more so than anyone would imagine.

“By detailing our experiences with biomass CHP we feel that we can assist others in utilising this groundbreaking technology.”