Biomass, Clean Coal Technologies, On Site Renewables

On-site power for distillery

Drinks company Diageo, which produces spirits such as Johnnie Walker, Tanqueray and Smirnoff, is to develop a biomass-fired on-site energy facility at a new distillery in Roseisle, on Speyside, Scotland.

The plant is designed to utilize the distillation co-products of spent grains (draff) – malted barley residue after sugar extraction – and pot ale – distillation residues containing yeast, protein and water, to supply heat to the facility.

To be designed, built and operated by Dalkia, the bioenergy facility at Roseisle Distillery will use a moving grate biomass boiler and a biogas boiler to combust both biogas and solid wastes to produce around 5 MW.

Initially the spent grains are treated by separating solids and liquid with a belt press, before the liquid portion goes to an anaerobic digester to produce biogas. The pot ale solids are separated using a decanter centrifuge with, again, the resultant liquid being sent to the anaerobic digester.

Liquid from the digester plant is further processed to provide water to the adjacent maltings plant.

The solids from the press and decanter are combusted together with dry residues from the adjacent Maltings operation, generating steam at 11 bar. All of the steam produced is used on site in the distillery.

The £40 million (US$60 million) distillery, due for completion this spring, will produce up to 10 million litres of whisky a year from its 14 six-metre high copper stills.

The development follows the August 2008 announcement of plans by Diageo for a similar bioenergy CHP installation at Scotland’s largest distillery, Cameronbridge in Fife.

Producing around 6 MWe and some 25 MWth, the system treats the spent wash by separating solids with a belt press, before the liquid portion goes to an anaerobic digester. In this case the treated digester water is expected to provide around 30% of the distillery’s needs.

Steam from the bubbling fluidized bed boiler passes to a two stage steam turbine, with some of the steam from the first stage supplying the distillery with process steam at 16 bar. The remainder goes on to the second stage of the turbine.

Again the plant is to be designed, built and operated by Dalkia. The anaerobic digester will be supplied by Paques BV, the water treatment plant will come from Veolia Water Solutions, and the bubbling fluidized bed boiler will be supplied by Enmas. The steam turbine will be supplied by Dresser Rand.

Costing approximately £65 million ($97.5 million), the planned facility is believed to be the largest single investment in renewable technology by a non-utility company in the UK. The project, which will also use spent wash as fuel, is set to reduce annual carbon emissions at the site by approximately 56,000 tonnes and will provide around 98% of the thermal steam and 80% of electrical power used at the distillery.

Dalkia will construct this facility over the next two years, which will then by transferred to Diageo under a finance lease arrangement, while continuing to be managed by Dalkia.

Around 90,000 tonnes of co-products, which would have required transport off-site by road, will be used at the distillery.