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wusoa GmbH: What shall we do with manure? Liquid manure for decentralized small-scale biogas plants.

Biogas has become an alternative and sustainable energy resource. In 2013, the 7,850 biogas plants in Germany – including 858 in Baden-Württemberg – produced enough biogas to cover around seven percent of Germany’s total electricity needs. Martin Falger, managing director of wusoa GmbH in Stuttgart, explained in an interview with Sanja Fessl (BIOPRO) why he believes that small-scale biogas plants have a promising future. They expand the biogas plant spectrum by enabling regions that do not have enough biomass to operate large biogas plants to benefit from this energy resource. Livestock farms in these regions also benefit from the presence of the small-scale plants.

In 2013 Austrian-born Martin Falger co-founded wusoa GmbH in Stuttgart-Weilimdorf with Charles Wiederkehr. wusoa GmbH sees itself as a partner of livestock farmers, communities and municipalities who want to use biological waste products sensibly. © private

You are currently developing a small-scale biogas plant prototype? You are a chef by training - how did you get this business idea?

I am originally from the Großes Walsertal Biosphere Reserve in the Austrian Vorarlberg area. Self-sufficient energy and heat generation has always been important for the mountain farmers. However, biogas has only played a subordinate role so far. And this was mainly because the usual concept involved biogas plants that were too big to be of interest to mountain farmers.

Five years ago, I heard about a company that was producing micro combined heat and power plants (micro-CHP) and thought about the possibility of designing plants for small- and medium-sized farms. The farmers would then be able to produce electricity and/or heat to cater for their own needs. This was the basic idea that eventually led to the establishment of wusoa GmbH in 2013.

What is wusoa GmbH’s small-scale biogas plant concept seeking to achieve?

On the one hand, we hope that the high degree of prefabrication and design standardization will help reduce planning costs. We have been able to bring on board Nübold, the architectural firm from Karlsruhe, which is a competent project partner and supports us in the physical design of the biogas plants. Different module sizes enable us to offer ideal solutions for different-sized farms, i.e. farms that have anything from 15 to 500 cows. 

On the other hand, we wanted to develop a profitable biogas plant concept, including biogas plants that operate with only manure and dung. We do not want to use food for energy production. We also believe that using organic waste and residues has huge potential that is currently only minimally exploited. We are, for example, building biogas plants that can be operated with at least 80 percent manure or dung along with other types of biological waste and residues. Our goal is to use resources that are unused, rather than resources that need to be grown.

In entrepreneurial terms, the next goal is the implementation of the first pilot project in the Tennental village community in Baden-Württemberg where we hope to complete and operate the first biogas plant in 2015. We hope to follow this up with many other exciting projects, for example, we would like to set up biogas plants for small farmers who want to produce their own heat, or biogas plants for municipalities who want to use grass and green waste in conjunction with manure from a local dairy farm. The village of Winterbach is currently planning to set up this type of biogas plant. 

What does a small-scale biogas plant look like?

wusoa GmbH constructs biogas plants that can be operated with at least 80% manure or dung in combination with other biological waste and residues. © wusoa GmbH

Our plants have one or several fermenting chambers. These chambers are equipped with our newly developed bionic agitators, small pumps to feed the fermenters, and an intermediate gas storage tank. The biogas plants also have an equipment room and a heating system as the final recipient, i.e. a gas-fired boiler, or a combined heat and power plant for producing power and/or heat. Actual biogas production is carried out with complex bacterial flora - methane bacteria amongst other things - in the fermenter chamber.

Our smallest plant requires a floor area of around 20 m² with a fermenter size of 10 m3; the largest fermenter module is 120 m3 on an area of around 100 m². The smaller modules are intended primarily as heating modules and a gas-fired boiler is connected to them. These modules generate heat from biogas, to be used, for example, to heat a house; there is an option to combine the larger modules with a combined heat and power plant to be used for producing electricity.

The size of the modules can be adapted to the size of the farm where the biogas plant is being built. However, we also have to take into account and integrate components such as manure stores into the overall concept. Experience has also shown that it is better to build smaller biogas plants than ones that are too big. This will leave the farmers with enough dung to use as humus, and it means they will not need to worry about producing enough material for the fermenter. We want the farmers to be farmers rather than energy producers.

What were the challenges you faced when you scaled down the size of biogas plants?

We have spent around two years now on the development of these smaller biogas plants. Biogas plants that were being used by ordinary farms contain far too much technology. So the biggest challenge was to simplify the systems. In addition, our fermenters are rectangular and we also wanted to use materials other than concrete.

Since the agitator is what consumes the most energy in a biogas plant, we did some comprehensive research which led to a novel agitator that used over 50 percent less energy than a standard agitator. The bionic agitator in our biogas plants requires 5.5 kW, which is the energy consumption of a normal washing machine. The farmer who tested our prototype made considerable cost savings because his old agitator used the same amount of energy that is needed to heat a normal family house.

The agitator technology has a huge effect on the gas yield and hence on the cost/benefit breakdown of biogas plants. wusoa GmbH’s bionic agitator uses a flow and displacement behaviour based on duck feet. This makes it better than other agitators. © wusoa GmbH

The conversion of the biogas into fuel still needs to be optimized. The conversion of biogas into biomethane is very costly. We are still looking for a company that can offer us an efficient and cost-effective solution.

What are the advantages of a modular small-scale biogas plant for farmers or municipalities?

The standardized modular design enables us to increase or decrease the size of biogas plants according to the needs of the farmer or municipality that will be operating them. The method has the additional advantage that each chamber works independently, thus reducing the likelihood of the entire plant being damaged. Having said that, it is impossible to prevent unwanted bacterial strains, antibiotics or other substances entering the plant. This will always have negative effects on biogas yield. Let me give you an example – there is a biogas plant in Styria where the farmer used to cut his cows’ claws before sending them through a brine bath for disinfection. The brine on the hooves then entered the cow shed and the manure. This changed the pH of the manure, which in turn had a negative effect on the biogas plant because the bacteria in the fermenter are very sensitive to such changes. The damage in a multichamber system would have been limited as only one chamber would have been affected. 

From a purely economic point of view, our systems are designed to be fully paid off in ten years or less. We have always been interested in closing the ecological cycle and have therefore joined forces with a company that has developed a method to convert manure into high-quality fertilizer. In this method, the manure is fermented under anaerobic conditions and subsequently mixed with specific microorganisms. A farmer from the Allgäu region who has been evaluating these microorganisms for around four years has not purchased any additional fertilizer for the last two years. The procedure also has the advantage that it is 80% less smelly than manure on the fields. 

Biogas is widely criticized. How would you respond to this criticism?

The major criticisms are that 1) biogas production competes with food production, and 2) biogas plants emit ozone-damaging methane into the atmosphere. Since we use waste or residue materials rather than corn, the first point is not applicable, but we do have to take such criticism seriously and provide adequate information and explanations.

We have also tried to invalidate the second, well-justified point by constructing biogas plants with no gas emissions. They are completely tight. Our biogas plants use closed lids rather than the traditional gas caps. We have to provide a lot of information, especially as far as the safety of biogas plants is concerned.

Why did you choose Baden-Württemberg to set up your company?

Baden-Württemberg is synonymous with innovation and know-how. There are companies in Baden-Württemberg that have been working on biogas plant construction for over 30 years. In addition, conditions here are excellent for start-up companies and young entrepreneurs, and the funding situation is also quite good. Take us for example: we have been given Innovation Voucher A and Innovation Voucher B High-tech by the Baden-Württemberg government; voucher B is for producing a bionic agitator prototype. Baden-Württemberg is also an excellent place for networking, which enables start-up companies to gradually get closer to their business goal. 

Mr Falger, thank you for talking with us.

The interview was conducted by Sanja Fessl from BIOPRO Baden-Württemberg GmbH. 

Key biogas plant features

The capacity of a biogas plant is given in cubic metres of biogas per hour. The capacity depends on the substrate used, the fermenter and its size in m3. The resulting biogas can then be used for producing heat via a gas-driven boiler or for producing electricity via a combined heat and power plant (given in Watt [W] of electrical or heat performance). The use of a combined heat and power plant enables both electricity and heat to be produced. For example, when a biogas plant that is operated along with a combined heat and power plant with a capacity of one kW converts biogas into electrical energy for one hour, it produces one kilowatt-hour energy (1 kWh).

Further information:

Martin Falger
wusoa GmbH
Holderäckerstr. 10
70499 Stuttgart
Tel.: +49 (0)711/91286344
E-mail: m.falger(at)wusoa.com

Website address: https://www.biooekonomie-bw.de/en/articles/news/wusoa-gmbh-what-shall-we-do-with-manure-liquid-manure-for-decentralized-small-scale-biogas-plants