Articles & Case Studies

Costing £65M, Diageo’s new bioenergy facility at Cameron Bridge in Scotland is believed to be the largest single investment in renewable technology by a non-utility company in the UK

Posted: Friday 7th October 2011

However, one pioneering whisky producer is looking to prove that waste-to-energy via anaerobic digestion (AD) is also perfectly feasible for small distilleries.

In a first for the whisky industry, Bruichladdich have introduced a simple but highly effective three-stage process that is already generating biogas, as well as achieving over 95% Chemical Oxygen Demand (COD) removal and 98% copper removal.

Islay-based Bruichladdich have brought in BioWayste’s High-Rate Waste-to-Energy system, which is the about the fastest and smallest commercially available AD process on the market. With pot-ale containing energy that is usually wasted (COD typically 50g/l) an average Bruichladdich seven-tonne mash can produce enough pot-ale to generate over 1000kWh of electricity. It means that potentially, £200 worth of electricity is recoverable from every mash:

· £75 from electricity saved (7p/kWh)

· £125 from Feed-in Tariff (11.5pk/Wh)*

· *The Government has just increased this to 14p/kWh

Bruichladdich currently produce around 150m3 pot-ale per week, which via the two 60m3 BioWayste reactors is capable of producing enough biogas to continuously power an 80Kw generator. Annual electricity savings and income from the Feed-in Tariff could amount to £70,000.

“We are still in the early stages, but the payback time isn’t daunting,” said Bruichladdich’s Managing Director Mark Reynier. “In addition to the biogas that we are looking to produce, we may also benefit from recovering some of the heat from the process. Also, the cost of having to have waste tankered away is always increasing, so there’s a clear saving to be made when this is no longer required”.

Eliminating the need for tankering-out pot-ale and spent lees is just one of the challenges faced at Bruichladdich, who are also looking to address the long-term sustainability of the existing disposal route and the reliability of the island’s electricity supply. As a small distillery there are only so many personnel on hand – and the priority quite rightly is to make fine whisky and not spend any disproportionate time on becoming waste treatment experts. Lack of space was also a big issue, as BioWayste’s UK Technical Sales Manager David Orme explains:

“Fortunately we are able to provide a very compact plant to match site constraints”, he said. “We have also designed our system to be fully automated, requiring only minimal operational attention and no specialist process knowledge. It is SCADA-controlled, easily accessible on a single computer screen, so very easy to monitor and update, with numerous alarms and trends built in to keep everything running smoothly”.

Orme emphasised that unlike today’s typical industrial-scale anaerobic digestion (AD) plants, which take around 30 days to break down a single tanker of waste, the modular, small footprint BioWayste process takes just 12-24 hours.

“Because we have such a high rate system our process is more like a piece of machinery than a traditional biological plant,” he added, “and it has the benefit over the larger AD plants in that it doesn’t have to be continuously fed. It is very flexible and can be switched on and off to run say, five days per week rather than seven. Our British designed and manufactured system really loves pot-ale and is ideally suited for smaller distilleries, ½M Litres alcohol p/a upwards”.

Although breweries don’t of course generate as strong an effluent as whisky distilleries, BioWayste’s system also provides an equally efficient wastewater treatment for beer producers, creating enough biogas to run some or most of a brewery, and possibly some excess. BioWayste already has a successful treatment plant at fresh orange juice producers, Orchard House Foods.

Bruichladdich’s Mark Reynier concluded: BioWayste have provided us with a beautifully simple yet highly effective and environmentally sound solution. The reactors are extremely resilient to the stop-start nature of our process. When the feed comes back on after a break, gas levels are recovered very quickly indeed. In just a few weeks the BioWayste process has proved that it is absolutely ideal for pot-ale and spent lees – almost completely destroying the COD – as well as achieving 98% copper removal”.

*

The BIOWAYSTE PROCESS

1.The Services Skid

Pot-ale and spent lees are mixed together and transferred to a tank to settle out gross solids. The liquid goes though the services skid, where there is pH control, nutrient addition and heat adjustment, before it enters the AD reactors. The biogas powers the CHP. Some heat is recovered and electricity is gained.

The services skid performs all the thermal, chemical and hydraulic conditioning needed to ensure that the substrate profile correctly matches the capacity of the reactors. It also centralises all the main serviceable items in one, easy-to-access location.

2.The reactors

Modular, hybrid, 60m3, capable of handling 1 tonne of COD per day. There are no moving parts.

3. CHP

This is a standard combined heat and power engine.

NB

The entire system was delivered to Bruichladdich on the back of two trucks – and required no special cranes during installation.




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