The site visit was organised in the framework of two projects:  by VCM and Wageningen University & Research, partners in the Horizon 2020 project SYSTEMIC, together with Biogas-E, partner in the IWT/VIS project ‘Transbio’.

The guided tour and information were provided by responsibles from Groot Zevert Vergisting, Wageningen University & Research and Nijhuis Industries.

If you were not able to attend, you can watch the videos below (left: in English, right: in Dutch).

Groot Zevert started operating in the 1960s as a transport company, but in the past decennia has grown into to a complete service provider, now also processing manure and producing biogas.

The biogas installation started in 2004 and was modernised in 2016. By 2018, it had processed 135.000 tons of manure (75% of the input) and bio-waste (25% of the input) and thereby produced 10 million m³ biogas, from which 80% is transported to the factory of Friesland Campina by means of a direct, five-kilometre pipeline.

The rest of the biogas is converted into green electricity on site by means of a CHP.

In time, Groot Zevert Vergisting wishes to be the first Green Mineral Centre in the Netherlands by advanced recovery of nutrients, organic matter and water from digestate and the production of tailor-made manure-derived fertiliser products for farmers.

This would also offer a sustainable solution for the manure surplus in the area.

The digestate is first separated by means of a decanter centrifuge in a solid fraction and a liquid fraction. The solid fraction is first sanitised with heat from infrared light.

Nutrient recovery from solid and liquid fractions is achieved through two separate process cascades: the GENIUS system (developed by Nijhuis Industries) and the Re-P-eat system (developed by Wageningen University & Research).

Suspended solids are further removed from the the liquid fraction through a Dissolved Air Flotation unit, by adding flocculants and fine air bubbles, catching the solids, grease and oil in a flotating layer of sludge.

In the following steps, the liquid fraction is treated with micro-filtration, a reverse osmosis and ion exchanger.

This renders two end products:

(1) water that complies with strict discharge limits and can therefore be released in the creek nearby;

(2) an NK concentrate.

The GENIUS process has been operational at Groot Zevert since March 2019.

In the framework of the pilot project ‘an Achterhoek without artificial fertiliser’ together with ForFarmers, this mineral concentrate is mixed with ammonium sulphate and/or ammonia water, to better comply with the crops’ nutrient demands. In 2018, field trials were done on grass and in 2019, on corn.

Within the 6th Dutch action plan, the pilot project  ‘an Achterhoek without artificial fertiliser’ is allowed to use the NK concentrates (“Green Meddows Fertiliser”) on the fields of a limited amount of farmers for two years as ‘mineral fertiliser’, i.e. application of more than 170 kg N/ha.year through precicion injection.

The application and results of the field trials are carefully monitored by Wageningen University & Research. The results of agronomical efficacy, N efficiency and environmental leaching will be very valuable for the SAFEMANURE study. This is a project conducted by the Joint Research Centre, commissioned by the European Commission and will study the criteria required for the safe use of recovered fertilisers from manure.

Tim Keysers, owner of the biogas plant Arbio BVBA in Antwerp (Belgium), has won the Ivan Tolpe Award 2019 with this project ‘NPirriK’.

The Flemish Coordination Centre for Manure Processing (VCM), partner of the SYSTEMIC project, organizes every two years a contest, looking for innovative technologies in manure processing.

With the Ivan Tolpe Award, VCM)wants to pay homage to the late Ivan Tolpe, pioneer in manure processing from West-Flanders (Belgium).

In this third edition VCM looked again for innovative ideas dealing with a demand-driven problem from the sector. Just like in the previous editions, also proposals from outside Flanders were welcome, if the concept was applicable in the Flemish context.

The goal of Ivan Tolpe Award is to develop and support innovative, promising techniques and this way guarantee the leading role of manure processing in Flanders in European context.

5 project proposals were received from Flanders, The Netherlands, Israel, Italy and Denmark. The jury of experts chose from these contestants 3 nominees: NPirriK (Flanders, Belgium), From manure to animal feed – Elsinga Beleidsplanning & Innovatie (The Netherlands) and TAYA-AV- Triple-T (Israel). Het members of VCM have voted NPirriK as the winner.

Npirrik applied in 2017 with success for the Flemish call for subsidies for circular economy projects “Vlaanderen Circulair”. This call aimed for demonstration and dissemination projects and it granted NPirriK with 100.000 € to realize the project. The technologies (belt press, reversed osmosis) were bought and installed at Arbio and are currently starting up. They are expected to be fully operational by the end of 2019.

On 29th of November 2018, SYSTEMIC attended the colloquium of Interregg project: Perséphone. The project started in 2017 and will run until 2020.

SYSTEMIC Outreach Location SCRL Kessler is also involved in this project as one of the participating biogas plants.
Presentations of the colloquium, can be downloaded here.
Mind that most of them are in French.

Agro Energy Hohenlohe in Kupferzell, Germany is a biogas plant owned by Thomas Karle.
In 2001 Thomas Karle started operating his first biogas plant. The biogas plant was constructed with quite simple technology and had a digester volume of 600m³ and a co-generation unit of 55 kWel. Which was below average at the time (190 kWel).

Mr Karle’s motivation to start producing biogas was to increase the value of this farm by utilizing the liquid manure from his fattening pigs, leaves of sugar beets and organic residues from his farm. Since the first installation, the biogas plant has been modified and optimized continuously. Mr Karle took the first step in 2003 when he increased the size of this biogas plant and installed a bigger CHP unit with approx. 300kW el.
Operation of the new plant started in 2004. To produce the necessary amount of gas Mr Karle increased the amount of digested energy crops and also added left over from fruit and vegetable processing.

The plant has a reception and mixing pit for slurry (100 m³) and a new feeding system to mix the solids with the liquids. This uses 120kWel and runs half an hour every 2 hours. A grinder grinds the solid feedstocks (90kW).

Each 2 hours 4 tons of solid material is mixed with 3,5ton of liquids and fed to the thermophilic digesters. The hydraulic retention time is 21 days.

The digestate is separated by means of a screw press without polymers, in a container. The air from the container is not washed but a ventilator drives it outside the container. The solid fraction from the screw press has a dry matter content of 70%.

In 2007, the biogas plant was upgraded by installing a micro gas turbine in cooperation with Greenvironment gmbh.

The rest of the heat is used to heat up the digesters and drying grain. In addition to this, a greenhouse type system was constructed for drying the solid fraction of the digestate.

Greenhouse and micro-gas turbine had the synergy effect that exhaust gas from the gas turbine served as hot air for drying.
The thermos solar system resembles a green house, which uses the exhaust gas of the gas turbine and warmth of the sun to dry the solid fraction which is spread to dry in 6 weeks.

The exhaust air from the green house is not scrubbed because emission measurements showed it to have a low ammonia levels due to the nitrogen being bound organically to the solid matter.

A part of the liquid fraction of the digestate is sprayed on top of the drying solid fraction to obtain the perfect consistency for pelletizing. While the solid fraction dries, a machine, called the electrical pig ® moves over the solid fraction to mix it and turn it until it has reached a dry matter content of 80-90%.

To maximize the heat from the CHP Mr Karle has built a district heating grid in 2009 to supply the village of Füssbach with renewable heat.

When the district heating started operation in winter 2009-2010, Füssbach was awarded to be the first “bioenergy village” in the district.

In 2012 the micro gas turbines were taken out of operation because of technical issues with the gas cleaning. Instead a second CHP unit was installed.

Since 2013 the CHPs are operated flexibly, which means that they produce electricity during when electricity is expensive and don’t run during the night, if the prices are low. Yet, the biogas plant has not reached its final configuration.

Mr Karle often cooperates with universities and research organizations. He collaborated with the Fraunhofer IGB institute in a project (BioEco SIM) that aimed to find new and feasible ways for farms to produce a diverse range of fertilizers from digestate.

Today a demonstration unit of the concept is still present on site, and it is designed and further developed by Geltz.
The concept of nutrient recovery from digestate and manure by Geltz and Frauenhofer IGB is the following:

•  -Acidification to transfer organically bound phosphorus to the liquid phase
• -Separation of solid and liquid fraction
• -Precipitation of phosphorus Salts
• -N-stripping scrubbing of the P-pour liquid

The manure or digestate is acidified to a pH of 5-5,6 which will cause the organically bound phosphorus to transfer to the liquid phase. The low pH will also limit the ammonia emission.
The acidified digestate or manure is then separated in different steps:

1. 1. by means of a screw press
2. 2. coarse separation by means of a vacuum separator. This looks like a screw that evacuates the liquid fraction. The solid fraction has a dry matter content of 15-20% and can be used as a soil conditioner since it contains almost no P or N.
3. 3. the liquid fraction undergoes a microfiltration (mesh of 2µm). This restrains the bacteria and fine organic particles, and the concentrate is recycled back to the first step. Sulphates, ammonium and dissolved phosphorus and other salts go through the filter to the permeate.

A pressure of 3 bar is used on the microfiltration membranes and the filters need to be cooled for optimal treatment. The membranes are cleaned with air each 5 hours and twice a week with water.

The organic waste line was built in 1995 and treats to the other 2 thermophilic digesters (also each 1200m³):
Leftover food, bio-waste, flotate and grease, blood and dairy waste.

All liquid wastes and slurries are unloaded in a drive-in building which can be closed off for emissions. There the liquids are pumped directly from the truck into a storage.
From this storage the feedstocks go to a heat exchanger which uses CHP heat to heat up oil and this heats up the liquid feedstocks up to 130°C and is hereby hygenized. After that, they are fed into the digesters.
Biogas from the energy crop line is burned in a CHP (Deutz) to 500kWel and the heat is recovered by a heat pipeline to the village of Gebersdorf to provide heat for households and 1 small industrial site.

The total cost of the plant was 900.000EUR for the energy crop line and 800.000EUR for the organic waste line. The plant can afford this, mainly because of the heat bonus and the reduces disposal costs for digestate.

Trials done with the ammonia sulphate showed that AS was more available for the  crops than pig slurry and proved that there was less nitrate leaching.

The air from the truck delivery zone, separation zone was transferred to the engines and burned. Other than that, there was no air treatment.

26st and 27^nd of September, a meeting was organized in the framework of the H2020 project SYSTEMIC, which aims to stimulate the implementation of sustainable and economically viable business cases for bio-waste, manure, sewage sludge treatment in Europe.

The meeting brought together representatives of 4 anaerobic digestion plants from different regions in Europe and the SYSTEMIC consortium.

The meeting took place in the meeting room “El Liceo” in Navia, Asturias, in the north of Spain, close to Biogastur, one of SYSTEMIC’s outreach locations.

To update the participating outreach locations on project results

• -To demonstrate the business development tool and start testing with it
• -Get their feedback on the tool
• -Visit the biogas plant of Biogastur

Welcome to Navia

Ignacio García Palacios, Mayor of Navia City Council (Spanish Socialist Workers Party)

Rubén Wensell, agricultural engineer and representative of Biogastur, Outreach Location

The SYSTEMIC consortium and outreach locations were warmly welcomed in the conference room of El liceo in Navia by the Mayor of Navia himself.
The mayor described the region of Navia as the region with the highest milk production in the North of Spain.

The region is also characterized by it’s agriculture, which is mainly corn, used as feed for the livestock.
In this region there are 134 dairy farms with each 200 cows, resulting in a density of 4 cows per ha and a manure surplus. Using the manure directly as fertilizer caused probles with nitrification of the groundwater. The mayor realized the importance of this issue for the region and was from the beginning very involved in the conception of the Biogastur-project.
This enormous biogas plant had the goal to treat 400.000 tonnes of cattle manure from the region with anaerobic digestion, hereby producing 30 GWel per year and the possibility to upgrade the biogas to biomethane to be used as vehicle fuel for cars and trucks. In full capacity the plants would produce 25.000 tonnes of dried solid fraction (80% DM), 350.000 tonnes of liquid fraction and 300 tonnes of struvite per year.
The mayor’s influence has undenyibly contributed to the succes of the Biogastur. The biogas plant is now running for a year, but at the moment only working on half capacity since it is still in start up phase. The mayor sees this project as 3 solutions for 1 manure problem:

• -The production biomethane as a green fuel for trucks.

• -The production of green electricity.

• -The creation of an environmentally safe fertilizer (digestate) that is low in nitrogen.

According to the farmers, who have been fertilizing their corn fields with the digestate, an increase the yield with 25% yield can be visually noticed. These numbers will be confirmed when the harvest is measured.

Visit to Biogastur Biogas Plant

Business Plan

The biogas plant is located in Navia in the province of Asturias in Spain and was started up in 2017 and is now running for a year.
The design of the plant and the business plan took nine years. Eventually the plant was built with 80 million € investments from 5 private investors and the milk cooperative (25%) and completely without any form of governmental subsidy. There is also no feed-in tariff for the produced electricity and gas.
The design of the plant and the business plan took nine years. Eventually the plant was built with 80 million € investments from 5 private investors and the milk cooperative a25%)(nd completely without any form of governmental subsidy. There is also no feed in tariff for the produced electricity and gas.

1. Intake of the manure
2. Electricity production and marketing on the grid
3. Marketing the end products: dried solid fraction of digestate and liquid fraction of digestate
   

Each income contributes to ±30% of the incomes, so each income balances the others and the plant doesn’t depend on one income route completely, which makes it more resilient for changes in the market.

The business plan of Biogastur is quite unique in Europe and therefore it will be studied in detail by the SYSTEMIC project.

Feedstock

The plant has a total capacity to treat 400.000 tons per year.
350.000 tons per year consists of cattle slurry. Since the milk cooperative is one of the shareholders of the biogas plant, the manure supply is contractually established. When farmers cannot supply the amount of manure they promised, they pay a fine to make up for the income loss Biogastur suffers.

Biogastur has its own truck fleet with which they daily or weekly collect the cow manure from cattle farms in a radius of 50km. The furthest one is 70 km away, but this one is very large and only supplies once a week.
The milk cooperative (and thus the dairy farmers) are charged 2-2,5€/ton to treat their manure, including transport.
The milk cooperative also supplies 25.000 tons of dairy waste (spoiled milk, whey, etc.) per year.

Other waste streams (25.000 tons per year) that are digested are rabbit manure, rabbit slaughterhouse waste, flower, molasse and glycerin. Biogastur pays for the energy rich feedstocks, f.e. glycerin is 5 times more expensive than molasses.

(2) in Figure 1 is the area where trucks with liquids can be washed and emptied. Residual heat from the CHP is used to heat up a water boiler (Figure 3) and warm water is used to clean the trucks.

(1) in Figure 1 has a special reception unit for solid waste. (3) shows the mixing tank for solid waste and manure, (4) are 3 tanks of each 60m³ for liquid wastes (glycerin, molasse, whey, spoiled milk). The mixing tank is 3000m³ and has 3 days buffer capacity. It can also serve as quarantine. The mixing tank mixes the solid waste with liquids to a DM content of 8%, approximately. This mixture is pumped to the digesters.

Sometimes flour is used as a feedstock. Instead of mixing this in the mixing tank, this is carefully injected directly in the digesters in very small volumes, to not influence the dry matter content to drastically, since the viscosity of the digestate in the digester determines how easy biogas is created and can escape the slurry.

Since it concerns thermophilic digestion, which is more sensitive than mesophilic digestion, the input loading rate is since the start-up increased very slowly to guarantee the adaptation of the bacteria from mesophilic to thermophilic. This is also the main reason the plant only runs on half capacity at the moment. All 4 digesters digesters are being used but the content is transferred from one to the other as needed in the preliminary tests and essays.

Biogas and heat

Yearly 17.000.000Nm³ of biogas is produced.
The biogas is scrubbed (6 in Figure 1) to remove the hydrogen sulfide (H2S) to <1000 mg /L, to guarantee the efficiency of the CHP engine and prevent corrosion damage to it. The removal of H2S efficiently facilitates the upgrade of biogas to natural gas quality.

Biogastur works with a patented system based on a biological desulfurization tower: the BIDOX® system (BIological Desulphurization by OXidation) (Figure 6). Biogas desulphurisation using the BIDOX is not associated with odour emission, because the system is completely closed. In addition there is no need for internal cleaning or biomass discharge or adding chemicals.

The BIDOX represents a fully automated and biological system in which biogas is treated in counter flow with washing water. During this treatment aerobic bacteria attached to the packing material inside the BIDOX convert H2S in the biogas almost entirely into sulphate.
To do this, the bacteria require oxygen. Therefore, 20% of the volume of the biogas is added in O2. The resulting methane concentration is around 64%.

The sulphate is discharged with the BIDOX effluent in the form of very diluted sulphuric acid. The sulphuric acid is discharged via the aerobic purification (MBR) installation (see later), where it is used as a nutrient and improves the buffer capacity.
The exploitation costs for the installation are low when compared to other biogas desulphurisation technologies. The power consumption of the BIDOX system is in the order of 0,21 kWh/kg H2S removed and the combined operational and maintenance costs mount up to around 0,10 -0,25 € / kg H2S removed. The majority of the maintenance costs are associated with the calibration of the measurement systems.

Process obstruction as a result of sulphur precipitation or foaming are not observed as a result of the low pH. For more information visit the Colsen website.

Part of the electricity is used on the site and the rest is sold to the electricity distributor at market prices (highest price in October 2018 was 75€/MW).

Biogastur is looking into upgrading the biogas to liquified biogas (LBG) to use as fuel for their truck fleet. To develop this technology, Biogastur has signed a plan with the national leader in gas distribution, ENAGAS, which will invest around 1,2 M€ in the upgrading technology and the connection to the national grid. The biomethane will be enriched from the starting point of 60-65 % up to the 95-98% of methane, required for the national grid.

Separation of the digestate

After anaerobic digestion, the digestate (350.000 tons per year) is separated by means of 2 centrifuges (Figure 8). To improve the separation efficiency several polymers are used, depending on the temperature, the pH, the solids concentration, and so on. Figure 9 shows a picture of one of the powder polymer (CV 150, CV 300) is added.

A curious fact was that there was almost no smell of ammonia in the neighborhood of the centrifuges. This suggests an air cleaning treatment step before the separation step (see further).

Drying of solid fraction

In (8) of Figure 1 the dryer is located. This is a belt dryer which dries with recovered heat of the CHP the solid fraction to 75-90% dry matter content. 10.000 tonnes of water per year is evaporated and the solid fraction is stored in a warehouse (9). Biogastur sells this to farmers as fertilizer with their own (precision) spreading equipment for a fixed price.

Now, during the start-up, the dried product is often offered for free to farmers as trial, but once the plant will be running on full scale a price will be asked for the solid fertilizer + application. The microbiological analyses on a mix of ashes with dry fraction and sawdust done have proven to contain halve the amount of E. Coli, Streptococcus, enterobacteria and other colonies ,compared to the cow bedding done with sand and calcium carbonate.

Air cleaning system

Again, no smell was noticeable at the dryer or the exhaust pipes, yet there was no air washing system nor biobed visible.
The air cleaning system appeared to be also patented and therefore no more details about the mechanism could be revealed. The system proved to be very effective, and the environmental permits were obtained by only limited description of the mechanism, and its efficacy substantiated with emission measurements.

This led to a lot of speculation amongst the visiting Outreach Locations and project partners.
Since there was no smell during separation, it was suggested that the air cleaning should be located somewhere in the digester or on the raw digestate.
Also no chemicals (acids) were noticed on site, which suggested that air scrubbing with acid was not done here. The fact that ammonium sulphate is subject to REACH regulation in Spain, reinforces this hypothesis.

Somehow the ammonia is removed from the digestate and most likely, the liquid ammonia solution is biologically treated in the MBR-NAS.
Nonetheless, we have no confirmation of these speculations and therefore the air cleaning mechanism and technology remains a secret.

Nitrification-denitrification of the liquid fraction

350.000 tons of liquid fraction per year is produced by the centrifuge. This goes to a NAS® (New Activated Sludge) system in 2 aeration basins (10) in which air is blown. The basins contain an activated sludge in which anammox bacteria constitute a part of the biomass (Figure 11).

In the first aerobic tank, a part of the ammonium nitrogen (NH4-N) is mainly oxidized to nitrite and partly to nitrate. In the next anoxic compartment, the nitrite and nitrate are denitrified. At the same time they convert COD into CO2 and biomass. Part of the remaining nitrite and NH4-N is converted directly into nitrogen gas by autotrophic organisms (Annamox, red arrows in Figure 11), under exclusion of oxygen and without conversion of COD. The remaining nitrogen is oxidized to nitrate in the 2nd aerated compartment. This nitrate is further denitrified during internal circulation.

The activated sludge, which contains the bacteria, is separated from the effluent by means of ultrafiltration membranes (MBR) (11). The effluent (13) contains 200 mg N/L and Spanish discharge limits allow this to be discharged together with the purified wastewater of the paper factory (100 x dilution) in the sea. The effluent can also be used as liquid fertilizer for corn and other local crops, including municipal parks and golf courses.

Phosphorus recovery

The plant has and ANPHOS® reactor (patented) to recover phosphorus from the NAS®effluent. During the previous treatment step, the phosphate present is largely converted into ortho-phosphate with potassium as counter-ion.

The basic principle of the ANPHOS® process is the aeration of the NAS®effluent, which induces a positive pH shift. As a result of the addition of magnesium(hydr)oxide, the ortho-phosphate reacts with ammonia and magnesium ions to form magnesium-ammonium-phosphate (MgAP) or magnesium-potassium-phosphate (MgKP) also known as ‘struvite’. After the reaction, the struvite is precipitated, dewatered and dried and can directly be applied as substitute for agricultural fertilizers.

There are some small deposits of struvite in the pipes near the centrifuges, which proves that struvite precipitation is technically possible.

Yet, because the biogas plant is currently not yet running on full capacity, there is not enough phosphorus in the effluent (average 177mg P/L) to precipitate large volumes of struvite. Which means that at the moment it is not yet profitable to recovery phosphorus from the effluent.

It is estimated that the plant could produce at maximum capacity 1 tonne of struvite per day. A few years ago, about 1100 €/tonne struvite was a realistic market price. If a lower price is offered, there is still an option to blend the struvite with the solid fraction and sell it as complete P-organic matter blend.

Conclusions and feedback

As far as biogas concerns, Spain is a market that is still has to be developed, and more specifically to agro-industrial biogas. In this sector, Biogastur we will be market leaders on the level of energy production (whether as biogas or such as electricity), the technologies implemented and the level of management of waste and GHG reduction (34,000 tonnes equivalent annual CO2).

The outreach locations and consortium members were impressed by the plant and especially the business case running without subsidies.
The patented air cleaning system impressed and frustrated everyone, because the working mechanism remained secret.

Yet, some critical remarks can be made.
The composition of the effluent after NAS® (200ppm N) is extremely high in comparison to the discharge limits in other European countries (f.e. 15 ppm in Belgium for surface water).

One does need to mention that Biogastur’s effluent is discharged in the sea and not in surface water and that the effluent is first diluted (factor 100) with treated wastewater from the paper factory.

Nonetheless, in most European countries, dilution is not regarded as a waste treatment step.
Also, the plant does not recover any nutrients (yet). All nitrogen is lost as N2 and because of the REACH obligation for ammonium sulphate, N recovery by means of stripping-scrubbing is no obvious alternative. On the other hand, other markets for ammonium sulphate, -nitrate of ammonium solution could be researched (cfr. Industrie, paper factory?) to also valorize this nutrient.

Yet, Biogastur wants to wait and see how the demand evolves for liquid fraction or NAS-effluent as a fertiliser. If this is positive, they will discharge less into the sea and give or sell more to local farmers.

Also have questions or remarks on the plant of Biogastur? Let us know in the comments section below.

Actions Biogas Bree in SYSTEMIC

• -Biogas Bree (BB) has contacts with a consultant/engineer with a lot of experience in optimizing heat exchange. He already made a tool to calculate how much heat is required to evaporate a certain amount of water.
• -Feedstocks have already been documented by DLV (consultant of BB).
• -Environmental permit submitted for 9000m³ storage and ammonia stripper-scrubber
• -Has received representatives of the Turkish associated plant Agman on their plant.
• -Has visited Waterleau New Energy, AMPower and Biogastur

Introduction to ENSY AB, Sweden.

ENSY AB is a private technology company in Sweden, active since October 2011, developing solutions for small scale farm-based nutrient recovering systems of manure. The core in ENSYs technology is the Multibox® system, a modularized system of mechanical and chemical de-watering and nutrient recovery modules.

ENSY operates a pilot plant outside Falkenberg in the south of Sweden together with a pig farmer.  For now, they focus on plants that can handle 15-30 000 tonnes manure per year.

ENSY has also an ambition to recover nutrients from digestate from biogas production and have made pilot studies with such input streams. However, for now they focus on manure, as such input material varies less over time than that from biogas plants and therefore easier to treat.

Drivers for nutrient recovery in Sweden

• Manure and digestate consist of 92-95% water for which spreading and storage has associated risks of losing a large proportion of the nutrients.
• Traditional spreading of manure, using heavy tankers etc, reduces soil fertility due to soil compacting, especially in clay soils. Soil compaction leads to decreased crop yields, which estimates for a reduced profit of 0,36-3,6 € per ton manure spread.
• Shortage of land for livestock farmers, typically hampering the transition to more effective large-scale livestock farms.
• Investment costs of manure storage and handling systems (new manure pits with sealing systems) and costs of transport and distribution of manure (long distance)Shortage of nitrogen fertilizers for organic farmer.

This last point has an impact on the market value of recovered NPK products, because in Sweden, Bio-certified, organic farmers are not allowed to use mineral nitrogen fertilizers. Therefore, the price for certified, organic nitrogen is substantially above that of standard nitrogen products

The Multibox® technology

Manure is separated in several steps. The first dewatering step uses two different types of in-house design self-cleaning filters (patent pending), tailored for the particle size and viscosity of the input stream. The purpose is to reduce all suspended solids in the liquid fraction above a certain size, typically 100-400 micron.  In a second phase of the system, mechanical and chemical treatment steps are combined to further purify the liquid.

The solid phase is further dewatered by ENSY’s in-house squeeze press technology without the use of coagulants or polymers to a dry matter content of 30-35%, comparable to the solid fraction of a decanter centrifuge (with the use of polymers). This product can be dried and pelletized further for better storability and can be used as a soil improver. ENSY plans to add concentrated nutrients from the liquid phase and dry the product further by means of composting, to produce a nutrient rich and hygienized fertilizer product. By composting the C/N ratio is reduced, which makes the nitrogen better accessible for the plants.

The fertilizer product is planned to be packed in big bags and stored and handled as standard mineral fertilizer. The product can also be Bio-certified depending on the origin of manure or digestate.

Contact person: Ulf Orrenius    ulf@ensy.eu    +46709705533

ENSY observations from the AMPower and Waterleau New Energy visits

The situation in Flanders is quite challenging when it comes to manure handling. Due to shortage of land, stringent fertilization limitations (Flanders is a Nitrate Vulnerable Zone according to the Nitrate Directive) and phosphor saturation of land, some farmers are obliged process the manure.

Most popular manure treatment is a separation in liquid and solid phase followed by biological treatment (nitrification-denitrification to reduce the nitrogen content) of the liquid phase. A drawback is loss of nitrogen to the atmosphere which both is a waste of nutrients for the plants and a climate hazard. The solid phase (containing most of the P) is typically transported abroad, often to France, after hygienization in composting tunnels. Nutrient separation/recovery from manure and digestate is only undertaken in a few cases, by pioneers, since the recovered products are still seen as manure by Flemish legislation and therefore the same fertilizing limits apply.

The business case of the biogas plants we visited rests on that the production of electricity is supported by ca 100 € per MWh.

From both plants visited there is an interest for more efficient de-watering technology to replace centrifuge-decanter technology to :

• reduce the amount of cat-ion polymers applied
• to reduce the output solid matter content (at present 2-3%).

Such technology could reduce the organic load on the later treatment steps (evaporator, Reversed Osmosis) and thereby reduce the costs of energy and chemicals. The first separation step of ENSYs Multibox® system may be useful here.