One of the by-products of the brewing process is high-energy renewable biogas. Rather than allowing this to go to waste, some breweries are using a process called combined heat and power (CHP) to cogenerate it into electricity and heat which can then be reused in the brewing process, significantly cutting operating and electricity costs.
Andy Cooper, head of energy efficiency at Clarke Energy, said: “Cogeneration is a highly-efficient form of energy conversion and, using gas engines, it can achieve primary energy savings of 40% compared to the separate purchase of electricity from the grid and gas for use in a boiler.”
Converting waste heat into cooling via absorption chillers is a process called combined cooling heat and power (CCHP), or trigeneration, and can also be deployed to support the cooling requirements of a brewery.
The brewing process comprises three major stages: the brew house; storage and fermentation; and bottling. The processes within these stages require energy, in the form of electricity, heat or cooling.
Since the temperatures of CHP thermal discharges range from around 45 to 180°C (exhaust gas), large potential arises from low-temperature heat consumers, such as bottle washing (90°C) and filtration. Two main criteria positively affect the efficiency of CHP facilities in breweries: a larger number of low-temperature processes and a constant heat and/or cooling demand.
Although not every brewery requires enough heat to operate a CHP facility for their production, CHP can financially benefit smaller companies. As many of these offer hospitality, the heat harvested via CHP can be used here.
The Scottish brewery BrewDog recently commissioned the construction of a £12m green gas plant that will use waste from the brewing process to power the production of more than 176m pints of beer annually, and provide fuel for delivery vehicles.
At full capacity, the facility at BrewDog’s headquarters in Ellon will reduce emissions by 7,500 tonnes, as part of the company’s £50m investment plans to reduce carbon emissions per hectolitre of beer by 35% versus its baseline in 2019.
Protecting the planet
Sarah Warman, BrewDog’s director of sustainability, said: “Our number-one sustainability goal is to reduce emissions, and we want to lead the way for the entire brewing industry. We want all our teams to feel like the work they do supports our mission to protect the planet.”
The plant will use wastewater from the brewing process in which spent yeast and hops will be anaerobically digested by bacteria to make biomethane. This is claimed to enable the company to recycle most of the 200m litres of wastewater produced each year in the brewing process and generate biomethane to power its boilers. When fully operational, the digester will create 200m3 of biomethane per hour, equivalent to 23,000MWh of energy per year.
Surplus gas will be used to power delivery vehicles and sold back to the grid. BrewDog also plans to use the CO2 created by the digester to carbonate its beer. Warman added: “Our ambition is nothing short of making BrewDog beer the most planet-friendly beer on Earth, and we’ve taken giant strides towards that goal with our new bio-energy plant.”
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