Cogenerated heat used to dry malt at German producer

High and nearly continuous heat loads tend to make good cogeneration applications and an installation of two CHP plants from MTU Onsite Energy at Gernsheim in Germany to dry malt for brewing beer is no exception. The power generated is fed into the host company’s own network.

Photo: Marcel Mayer

A malt house has an extremely high demand for energy ” both electrical and thermal. For this reason, German malt producer Durst Malz has been operating two combined heat and power (CHP) plants from MTU Onsite Energy at its location in Gernsheim since July 2011 that can do both simultaneously.

The type GC 357 N5 CHP plants deliver around 1 MW of heat, which is used to dry the malt. The 700 kW (approximately) of electrical energy, which the plants generate in addition to the thermal energy, is fed into the company’s own grid, resulting in an overall efficiency level of almost 90%. Two identical plants have also been installed at the Durst Malz location in Bruchsal-Heidelsheim.

Durst Malz, founded in 1824, has evolved over a period of almost two centuries from a family-run business into a major malt producer for the brewing industry. Since October 2011, the company has been a member of the French malt producer Groupe Soufflet, the world’s second largest malt producer. Durst Malz’s head offices are in Bruchsal-Heidelsheim and the company has two other locations in Castrop-Rauxel and Gernsheim. Durst Malz produces around 200,000 tonnes of malt annually, 86,000 tonnes of which are produced in Gernsheim am Rhein.

Malt, which is specified in the German purity law of 1516 as one of only four permissable ingredients in beer, along with hops, water and yeast, is obtained from grain, primarily barley. It is also the ingredient with the greatest influence on how a beer tastes. ‘Here in Gernsheim, we only use barley,’ said plant manager and graduate brewmaster, Berthold Klee. Customers include many major German breweries, but the company also exports to Japan, Namibia, South Africa, Guatemala and the US.


The raw material arrives by truck, rail and barge ” Gernsheim has its own barge berthing facilities ” close to the malting plant. Before it is stored in the 50-metre high round silos, the incoming barley is examined by the company’s own laboratories to measure its grain size and its water and protein content.

The key factor, however, is the seed’s germination capacity, which will ultimately determine whether the barley can be used for brewing purposes. During the germination process, enzymes are formed that enable the starch present in the barley to be transformed during the actual brewing process into maltose. By adding yeast in the fermentation process that follows, the maltose is fermented into alcohol.

Durst Malz malt producer, located in Gernsheim Photo: Marcel Mayer

The barley is now transferred by belt conveyors from the silos into one of the three germination towers, which have a diameter around four times greater than that of the round silos. The germination tower is the core element of a malt house, because this is where the barley is turned into malt.

The process begins at the top of the tower and ends on the ground floor. The germination chambers, consisting of large round areas each covered with 250 tonnes of barley, are on the upper floors. Their high humidity is apparent in the drops of water that coat the ceiling. Moisture in the air recreates the atmosphere of a steam bath. But before the barley can germinate here, it is first steeped in water in large vats. Once its water content reaches 45%, the barley is transferred to the germination chamber and allowed to germinate there for a period of six days. To ensure uniform germination, the barley is constantly moistened, aerated and turned.

‘Basically, we do nothing different from someone who places seeds in a saucer on the window sill, adds water, and lets them germinate until they are ready to be mixed into a salad to improve the taste,’ says Klee.

‘The only difference is that we end the germination process after six days and the seeds are then dried a couple of floors down,’ adds Konrad Lord, the production manager.


The atmosphere on the third and first floors is more like being in a scented sauna: aromatic malt aroma, plus a cosy temperature of 65à‚°C (149à‚°F). Four load ventilators blow 450,000 m3 of air an hour into the kilns to dry the malt, raising the temperature to 85à‚°C (185à‚°F). The humidity level subsequently drops from 45% to just 4%. Covered with drying malt, the floor of the kiln appears to be coated in caramel.

This is where the two natural gas-fired CHP plants are used. ‘We need an enormous amount of heat for the drying process,’ explains Klee.

A hot water boiler delivers up to 6 MW of thermal energy. Relief is provided by the two GC 357 N5 CHP plants, which generate around 1 MW of thermal energy. To operate at the highest possible energy efficiency, the malt house also uses ‘waste products’ to heat up the air, such as the waste heat from the CHP plants or the heat dissipated during the drying process. The latter is initially used to heat up the fresh air for the drying kilns via a heat exchanger before the CHP plants are added when the temperature has risen to 60à‚°C (140à‚°F). When the temperature hits 85à‚°C (185à‚°F), the maximum temperature reached in the drying process, the energy is supplied from the hot water boiler.

The raw material arrives by truck, rail and barge ” Gernsheim has its own barge berthing facilities ” close to the malting plant. Via a belt conveyor, a huge vacuum unloader transports 60 to 80 tonnes of barley an hour into one of the round storage silos. Photo: Marcel Mayer

The 700 kW of electrical energy produced by the plants, in addition to the thermal energy, is fed into the company’s own grid. The plants operate with an overall efficiency of almost 90%.

‘A malt house needs a lot of energy, which is why it is the ideal place for CHP plants,’ says Klee.

In addition to the 800 m3 of water required daily ” by way of comparison: a four-person family uses around 150 m3 a year ” the malt house consumes 4″5 GWh of gas and 800″900 MWh of electrical power a month. ‘And we benefit, of course, from the public funding of the CHP plants as a result of the Combined Heat and Power Generation Act,’ adds Klee.

Technicians from MTU Onsite Energy also take care of the servicing and regular maintenance of the CHP plants.


Since the plants were installed in the basement of a germination tower in July 2011, they have been running virtually non-stop for around 23 hours a day. They are only switched off when the malt is exchanged in the kiln. ‘Our aim is to generate between 180 MWh and 200 MWh a month with each unit.’

How did Durst Malz hear about MTU Onsite Energy? ‘Through the building technology company Helmut Herbert, which had already installed the hot water boiler. Herbert has already been working closely with MTU Onsite Energy for many years,’ the plant manager explains.

‘We knew that Herbert has powerful and reliable partners, which is why we decided to go to another manufacturer in Augsburg to replace the previous cogeneration plants we had ” and are completely satisfied with the result.’

MTU Onsite Energy supplied the main component, the CHP modules and the associated switchgear, explains Peter Gràƒ¼ner, head of Sales Germany Gas Power Systems at MTU Onsite Energy. ‘The modules consist of a gas engine, generator, waste heat exchanger, exhaust silencer, module control system and power control cabinet,’ he says.

‘All these components are mounted on a base frame, complete with piping and cabling. Our client Herbert then installed the plants at Durst Malz, complete with all auxiliary equipment ” this included the ventilation system, flue gas system, lubricating oil system, the connection to the natural gas supply, plus the heating and electrical installation. We then called in our specialists from Augsburg to carry out the commissioning of the CHP plant.’

Following commissioning and start-up, service technicians from MTU Onsite Energy look after the plant and are responsible for the routine maintenance of the CHP units.


The malt house has a throughput of between 8000 and 9000 tonnes of barley each month, with production running non-stop 365 days a year, summer and winter.

‘During the summer months, we deliver more, because people are more thirsty then,’ says Klee. But do the months prior to the Oktoberfest form seasonal peak? ‘No,’ he explains, with a mischievous smile. It may be a really big party in Munich, but the malt production for the Oktoberfest is only a very small part of the summer production.

By comparison: at the Munich Oktoberfest in 2011, visitors consumed some 7.5 million litres of beer. Every year at the Gernsheim location, Durst Malz produces malt for around 538 million litres ” enough malt for over 70 Munich Oktoberfest a year!

MTU Onsite Energy is the brand name under which the Tognum Group markets distributed power generation systems, which include compact cogeneration modules powered by gas engines up to 2,150 kW, or gas turbines up to 45 MW, for the generation of both heat and power.

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