Many breweries now use nitrogen alongside carbon dioxide. In Germany, one such brewery has recognised the benefits of generating their own nitrogen over relying on liquid gas supply and exclusively using carbon dioxide in various processes. Here Horst Nowosad, project engineer at Oxysystems explains how they did it.
At the brewery Herbsthäuser, nitrogen is used in the beer tanks alongside carbon dioxide for pre-charging or for the keg system.
At the beginning of 2024, Lanz Drucklufttechnik was commissioned to replace an old existing system with a new, more efficient nitrogen system from Oxysystems.
Lanz Drucklufttechnik from Pleinfeld and Oxysystems GmbH from Herrsching are partners of many breweries.
Turnkey system solutions including installation, commissioning and maintenance are offered to breweries by Mr. Christian Lanz and his team.
An all-round “carefree package” enables continuous and smooth brewery operation and reliable nitrogen production. The new installation also ensures that no expensive carbon dioxide has to be purchased in the future.
After wort preparation in the brewhouse and the main fermentation in the fermentation cellar, the fermentation tanks and later the storage tanks are cooled down for the secondary fermentation and maturation of the beer.
The secondary fermentation/maturation takes up to six weeks.
At the end of the storage period, the finished beer is either bottled directly or first sent for filtration and then temporarily stored in the pressure tanks. The beer is then bottled or kegged from these tanks.
If the storage tanks are emptied in the course of feeding the filter or the pressure tanks for feeding the bottling plants, carbon dioxide is generally used. This not inconsiderable amount of carbon dioxide can be completely replaced by nitrogen.
In addition, keg filling can be operated with 100% nitrogen and bottle filling with a CO2 / N2 gas mixer with up to 80% nitrogen.
Carbon dioxide recovery only makes limited economic sense for larger breweries. Any additional demand in parallel with carbon dioxide recovery can also be covered by suitable in-house nitrogen production. The extent to which nitrogen is used in breweries depends primarily on the various processes in the brewery.
Examples of nitrogen applications include pre-pressurizing or emptying tanks or containers. Furthermore, N2 can also be used very well for water degassing. Examples of oxygen applications can be found in wort aeration and the aeration of yeast propagators or yeast cultivation.
Water is the basis of all beverages. Oxygen can be removed from water relatively easily and is the most cost-effective way to ensure good product quality right from the start. We speak of degassed water when we mean a reduced oxygen content.
Oxygen in the brewery
In food & beverage production, it is always necessary to keep the oxygen content in the product as low as possible.
The presence of oxygen is a prerequisite for the growth of aerobic germs, such as mould. Oxygen also has an unfavourable effect on colour and taste. Especially if prolonged heat treatment is necessary.
Oxygen reacts oxidatively with the amino acid methionine, ascorbic acid (vitamin C), flavonoids (secondary plant substances) and unsaturated fats and lipids. Oxygen also promotes photosensitized oxidation (triggered by visible light) in transparently packaged foods. The shelf life of a product therefore depends heavily on the residual oxygen content.
Physical principles of water degassing
Oxygen can be removed from water using chemical or physical processes. As chemical processes are based on the addition of a reducing agent and are therefore usually unsuitable for production, only physical degassing will be discussed below:
For example, approx. 9 parts per million (ppm) dissolves in water at 20 °C in ambient air with 21% oxygen.
A low partial pressure shifts the equilibrium so that less oxygen dissolves or the dissolved oxygen is released. These two relationships are used for degassing.
Stripping degassing
By introducing an oxygen-free stripping gas, the concentration of oxygen and thus its partial pressure is reduced.
The shift in phase equilibrium causes the oxygen to pass from the water to the gas phase. In breweries, CO2 is usually used as a stripping gas.
As it is produced during fermentation and is also used for carbonation and other processes, it is almost always available.
However, many breweries use nitrogen, which is generated from ambient air. Depending on the system design, cold water can be degassed to less than 20 ppb parts per billion (ppb).
Nitrogen is more efficient at removing oxygen and is not absorbed by degassed water like CO2, making it ideal for producing still beverages.
Conversely, CO2 is preferred for carbonated beverages. The deaerated water is buffered with CO2 to minimize recontamination with oxygen, and the CO2 used is largely incorporated into the product.
The nitrogen production process
In the case of the brewery Herbsthäuser, the in-house generator can produce over 30Nm3 of nitrogen with a quality of up to 99.9%.
The OS-25-NX nitrogen generator works according to the pressure swing adsorption (PSA) process described below.
In this process, the nitrogen component is separated from the purified compressed air and made available for further processing in a downstream process tank. Peak consumption can easily be covered by additional N2 intermediate storage tanks.
The nitrogen N2 PSA system generates the required gas from the atmosphere, nitrogen (N2) is extracted and purified, while the rest is returned to the atmosphere.
A special compressed air station purifies and filters the air under pressure before it enters the nitrogen generator, which is equipped with a Siemens S7 control system. Oxygen, CO2 and all other trace gases are absorbed by the carbon molecular sieve, allowing nitrogen to enter the dual buffer storage system.
The system works continuously and automatically ensures a constant flow of high-purity nitrogen. The gas produced is permanently monitored with a high-quality nitrogen sensor. Appropriate system settings are used to issue alarm messages as needed to ensure a controlled nitrogen supply.
The system guarantees the highest purity of nitrogen and includes an advanced gas monitoring process that allows both local monitoring and remote diagnostics, ensuring continuous proper operation. The purified nitrogen is stored in a storage tank for various brewery processes.
For carbonation, the pure nitrogen is mixed with CO2 in the desired ratio (usually 70/30) and then stored in a separate tank at the required pressure. This turnkey solution provides breweries with the most cost-effective and efficient operation.
The compressed air system, which is required for self-generation, provides a corresponding heat in addition to the compressed air.
On the one hand, the hot exhaust air can also be used to heat rooms. An additional heat exchanger can be used to heat water or other solutions at the same time.
This saves additional heating costs and further reduces your CO2 impact. The application also drastically balances the operating costs of the system.
Carbon Footprint Reduction
The reduction is drastic. To put this in perspective with conventional supply (liquid nitrogen deliveries).1 litre of liquid N2 is equal to 79 g CO2.
A recent study took the energy intensity of liquid nitrogen production as 0.549 kWh/kg, equating to 79 g CO2 per litre of liquid.
The carbon footprint of liquid nitrogen comes from its physical manufacture, through compression and fractional distillation of air, and from its transportation to an end-user site.
The advantages of using nitrogen in breweries are becoming increasingly clear and the market is growing steadily. Independence from gas suppliers and annual cost savings are now often an important reason for switching to nitrogen self-generation.
In addition to the direct financial savings, breweries can produce beer in an even more climate-neutral way.
Utilizing heat recovery, renewable energy, energy-efficient systems, and reducing transportation collectively help to significantly lower the CO2 footprint.
