Innovative technology
vapocircle: the fermentation residue evaporation technology
What is VapoCircle? The closed-loop system for digestate evaporation
VapoCircle is Biogastechnik Süd’s digestate evaporation technology – a closed-loop system that transforms liquid digestate into valuable products. Through thermal evaporation and condensation, digestate is reduced to up to 70 per cent of its original volume. At the same time,farmAS®(ammonium sulphate solution) andfarmLC®(liquid concentrate) are produced – high-quality farm manures with a precise nutrient composition. The system operates with low emissions, complies with the Technical Instructions on Air Quality (TA-Luft) and is fully closed-loop: no ammonia emissions, no storage issues.
The problem & the solution
Electricity or fuel from renewable sources is not always available exactly when it is needed. These fluctuations often arise when using renewable energy – wind turbines generate electricity as soon as the wind blows, and solar panels as soon as the sun shines.
These fluctuations mean that at certain times there is either too much or too little electricity in the grid. This is where the major advantage ofthe renewable storage power stationcomes into play.
Arenewable storage power stationcombines a power station with an energy storage system. It generates electricity and heat on demand – precisely when they are needed.
The electricity generated can be fed into the public grid at peak-price times, thereby generating higher revenues which lead to improved economic efficiency of the plant.
Gas processing
The producer receives revenue from various sources, including thebasic feed-in tariff underthe EEG and theflexibility premium.
Under the EEG 2021, support for flexibility measures remains available. The flexibility requirements stipulate that flexible biogas plants must utilise at least 85 per cent of their installed capacity for at least 1,000 hours per year (4,000 quarter-hours).
The producer has several individual options, or a combination of several of the following, for gas utilisation:
The producer decides whether the gas is fed intothe gas gridorsoldthroughdirect marketing, whereby the electricity is traded directly on the exchange.
A further benefit for the generator is the use of heat via a large buffer storage tank for their own farm buildings and other consumers, such as entire heating networks serving several households.
There is also the option of feeding the electricity generated into the public gridas and when required, thereby taking advantage of high prices.
Producers have the option of using biomethane asa fuel, thereby saving a significant amount of CO₂ compared to conventional fuels. The use of these low-carbon energy sources results in a reduction in greenhouse gas emissions into the atmosphere.
The CO₂ savings made by producers through the use of this fuel can be credited to oil companies’ own carbon footprints by purchasingCO₂ certificates.
The generator chooses whether to produce either electricity or fuel, or a combination of both (hybrid power station).
The fermentation line
VapoCircle technologycombines the advantages of the Returgant Direkt and the Vapogant.
The interactionbetweentheReturgantDirekt and the Vapogant digestate evaporation systemmakes it possible to achieveabove-average gas productionusing small tanks. The Returgant Direkt biomass recirculation filter ensures complete fermentation of the feedstock, thereby achieving a higher gas yield.
Gas yield is further increased when theReturgantDirektis followed by ultrasonic treatment using the WaveBox. Evaporation achieves avolume reductionof up to 70 per cent of the annual volume. The liquid phase can be concentrated to up to 20 per cent dry matter.
Heat recoveryand the reuse of heat for the Vapogant digestate evaporation process also offer energy-saving benefits.
What is Farm AS?
Farm ASis colloquiallyreferred toasASL(ammonium sulphate solution), which can be produced on the farm itself. Farm AS is a clear, colourless mixture and, depending on its concentration,has anitrogen contentof up to 8.5% (= 100% ammonium nitrogen).
When used as a fertiliser,Farm ASpromotes improved humus formation by stimulating the activity of soil organisms. In the soil,Farm ASbinds to clay minerals and humus, thereby preventing leaching.
The targeted application ofFarm ASas a slow-release fertiliser is carried out using the Cultan process. By applying it directly into the soil, nitrogen loss – which would otherwise occur through leaching and volatilisation – is reduced.
The result is a fertiliser that is maximally effective for plants, enablingmaximum yieldsto be achieved.
Mineral fertiliser production
Farmers can use VapoCircle technology in conjunction with a biogas plant to produce their ownFarm ASmineral fertiliser. This makes it possible to use nitrogen fertiliser beyond the 170 kg N limit. Farm ASis a valuable commercial fertiliser and any surplus can be sold. The Vapogant digestate evaporation process enables thedigestion ofsubstrates previously considered difficult to process, which produce higher levels of ammonia and nitrogen (including gaseous forms). Through intelligent crop rotation and the use of legumes, mineral fertiliser requirements can be met from the farm’s own forage production, and a further approx. 40% of Farm AS can be sold to farmers who, for example, grow cash crops.
But how should fertilisation be carried out, and how do the minerals ultimately reach the plant?
Inthe CULTAN method(ControlledUptakeLongTermAmmoniumNutrition), the plant is supplied with concentrated nitrogen via a fertiliser reservoir in the soil to ensurelong-term nutrition.
As the plant grows, its roots extend towards the reservoir. This results in better and denser root development, enabling the plant to store larger reserves of water.
Benefits of VapoCircle technology
Benefits for farmers/producers
- no competition between dairy farmers and biogas producers,
- organic slurry recovery
- in-house mineral fertiliser production at Farm AS
- Improvement of the fertiliser balance through the release or conversion of nutrients
- Improved flowability through fermentation and separation
- Savings in storage space
- Utilisation of surplus feed, e.g. grass silage
Environmental benefits
- Nutrient hub
- Humus formation
- Reduced ammonia pollution for the environment
- Improvement in the CO₂ balance through the use of slurry for energy production
- Sensible use of methane from slurry
- Closed-loop transport
Benefits for the public
- CO₂ storage
- low odour emissions during transport and application
- Sustainable approach
- Secure local energy supply
- Avoiding the ‘food-versus-fuel’ conflict
- Feeding the world’s population
In order to provide humanity with sufficient food, it is not enough simply to harvest crops; intensive fertilisation is also required. To date, mineral fertiliser has mostly been produced using a process developed after the First World War (the Haber-Bosch process). Producing mineral fertiliser on an industrial scale requires large quantities of natural gas, which is, above all, expensive.
Ideally, Farm AS is produced in agricultural settings with extensive grassland; any surplus Farm AS can then be used in agriculture for the cultivation of cash crops (e.g. wheat) for targeted fertilisation with Farm AS.
In a nutshell
With the help ofthe renewable storage and fuel power station, farmers can sustainably utilise their farm by-products, such as grass silage, slurry and slurry press cake.
Producers feed electricity into the grid, thereby contributing to security of supply.
Biomethane is used to produce fuel. This fuel can either be used by the customer or CO₂ credits can be sold to oil companies.
Thanks to VapoCircle technology, it is possible to produce your own FarmAS mineral fertiliser, which can even be sold if there is a surplus.
The renewable storage power station and the renewable fuel power station make it possible to generate electricity and heat on demand and to produce your own mineral fertiliser!
