Bioenergy in beer production
Beer takes a lot of energy to produce. From boiling thousands litres of water to affixing labels on bottles all along the line, breweries have usually industrial-sized energy needs . Energy is needed for the production of beer, but also clean resources like water, soil, barley and wheat are the crucial prerequisites for high quality beer products . Therefore, climate protection and resource conservation are one of the most important aspects to be considered when developing efficient production methods in beer manufacturing. The reduction of environmental impact of breweries can be achieved by utilisation of renewable energy sources to cover the energy demand of the production process. Especially biomass-fired cogeneration plants are suitable as energy sources for breweries, because they can cover the heat demand of the beer production process and supply breweries with power.
Figure 1: Environmentally-friendly beer production in Murau 
The utilisation of biomass as energy source for the brewing process is not only beneficial in terms of climate protection, it is also good for the economy and supports regional development . The energy demand of the brewing process can be covered by using production residues as fuel in boilers. The use of by-products from the brewing process as a fuel allows to save hundreds litres of heating oil per day to fire the boiler . Another possibility to achieve CO2-neutral balance of the production process is the utilisation of residues as substrate in biogas plants.
Beer production – biomass as energy source
The production of beer can be optimised with respect to the utilisation of biomass as an energy source. In order to apply biomass as energy source in beer production, the process could be carried out at lower temperatures.
The brewing process is carried out in several steps with different temperature levels :
- Mashing – combining of milled grain and water and heating this mixture. During mashing enzymes in the malt break down the starch in the grain into sugars to create a malty liquid called wort. Temperature level: 50 – 75°C
- Lautering – separation of the wort from the grains. This is done in a lauter tun, mash tun or in a lauter filter. Temperature level: 75°C
- Boiling – the beer is boiled with hops after mashing in a large tank known as “cooper” or brew kettle or in mash vessels, which are still used in some small breweries. Temperature level: 100°C
- Cooling – after boiling the beer has to be cooled down to 10°C. Temperature level: 90 – 10°C
- Fermentation and lagering – fermentation takes place in fermentation vessels. After cooling and aeration yeast is added to the wort and it begins to ferment. During lagering the beer is storred at near freezing temperatures for 1-6 months. Temperature level: 0 – 12°C
- Filtering and packaging – filtering is applied in order to stabilise flavour and gives the beer the brilliance. During packaging beer is put into bottles, aluminium cans and kegs. Temperature level: ambient temperature
Biomass can be utilised in order to cover the heat demand of the beer production process. Three bioenergy technologies can be suggested as energy source for the brewing industry because of their maturity and efficiency: biomass combustion, decentralised ORC plants and biogas plants. Biomass combustion appliances are a promising alternative to cover the heat demand of the brewing process. Usually hot steam at a temperature level of up to 160°C is used as heat transport agent for the beer production process. Such high temperature levels cause condensing loses and make the beer production less efficient and energy-intensive. However, a significant reduction of the process temperature can be achieved after process optimisation. The brewery Murau applied an innovative low-temperature process in which three temperatures are used: 115 degrees for boiling, 105 degrees for bottle washer and 95 degrees for the rest. The heating energy at such temperature levels can be delivered directly from municipal and communal bioenergy plants. These plants are fired with biomass from the surrounding region. In this way the financial resources invested in the covering of the heating demand supports the strengthening of the regional economy . Modern biomass combustion appliances achieve efficiencies of above 90% and can deal with varying fuel quality.
Figure 2: Wood chips as energy source for the brewing process. Municipal cogeneration plant covers the electricity and heat demand of the brewery Murau 
The experience gained during energy optimisation of a brewery with a yearly beer production of 300 000 hectolitres have shown that the utilisation of renewable energy sources for covering of the energy demand the brewery saves about 165 000 litres of fuel oil each year . The stepwise optimisation of the beer production process and the utilisation of biomass as energy source have led to savings of four millions of Euros of production costs during the last 15 years. This shows that the optimisation of the production process and utilisation of renewable energy sources has not only ecological advantages but results also in significant reduction in operating expenses . Even more advantagenous is the utilisation of small- and medium-sized ORC cogeneration plants to cover the energy demand of breweries. ORC plants have a similar working principle as the classical steam plants, with the main difference, that an organic medium is used instead of water as the working fluid. The cogeneration systems can be applied to cover the heat demand of brewing facilities as the can provide heating water with up to 90°C. Another advantage of the system configuration is the possibility to use the electricity generated in the biomass-fired cogeneration system in order to cover the electricity demand of the beer production facility. Decentralised cogeneration plants can generate electricity with an efficiency of 17%. The disadvantage of ORC plants are the relatively high investment cost.
Figure 3: Investment cost of ORC plants
Another possibility for reduction of environmental impact of beer production is the generation of biogas from production residues and wastes from the brewing process. The production residues are mainly organic matter with high water content. The drying and combustion of production residues are not ecologically advantageous due to the relatively high fine particle emissions from the combustion process. The utilisation of product wastes from the brewing process as substrates in biogas plants is a promising alternative to cover the energy demand of breweries. One important advantage of such solution is the possibility to achieve CO2-neutral brewery operation with significantly reduced environmental impact. Brewers grains are a very valuable substrate for biogas plants because they enable to achieve high yields of energy produced, about 118 m3 of biogas can be generated per tonne of substrate. Additionally brewers’ grains are biodegradable and leave almost no residues after anaerobic digestion. The utilisation of brewers grains to produce biogas is relatively simple.
Figure 4: Biogas production to cover the energy demand of beer-making process. Biogas fuels a cogeneration plant, which covers the electricity demand of the beer-making process and delivers hot water for the anaerobic digester 
The utilisation of biogas as energy source for cogeneration modules enables to cover about 72% of the electricity demand and 80% of the heat demand of a beer production facility. The remaining part of the energy demand can be covered easily by utilisation of another renewable energy sources. The brewing process offers also the possibility to capture CO2 from the fermentation process. In this case even a CO2 negative process balance can be achieved . Figure 5 shows the investment cost of biogas plants.
Figure 5: Investment cost of biogas plants
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