The Fraunhofer Institute for Interfacial Engineering & Biotechnology IGB has developed the BioEcoSIM process for treatment of liquid manure. The process will be introduced to the market by SUEZ Germany as an operator of large-scale plants.

BioEcoSIM creates an opportunity for farms to dispose of surplus manure and digestate, with the resulting slurry treatment products including phosphate fertilizers, ammonium fertilizers and organic soil improvers, according to the announcement. The partners will announce their cooperation for the market launch at IFAT on May 14-18 in Munich, Germany.

Around 200 million cu. m of liquid manure from livestock farming end up in fields in Germany every year. More than 90% of the “black gold” consists of water and contains considerable amounts of the important plant nutrients nitrogen and phosphorus, the institute said.

However, if more liquid manure is applied to the fields than the soil can bind and the plants can absorb, microorganisms convert the ammonium nitrogen in the soil into nitrate that seeps into the groundwater. The problem lies in where large quantities of liquid manure are produced, there is often a lack of arable land that needs to be fertilized. For this reason, German farms use so-called slurry exchanges to order tankers to transport their slurry to areas requiring nutrients — often several-hundred kilometers away, the announcement said.

With its BioEcoSIM process, the Fraunhofer IGB has developed an environmentally friendly solution.

“We have combined various processing steps into an overall process and integrated them in a modular plant,” Fraunhofer IGB nutrient expert Dr. Iosif Mariakakis explained. This allows the valuable nutrients to be recovered as easily transportable and precisely metered phosphorus and ammonium fertilizer salts. The solid organic components are also recycled by drying and conditioning using an energy-efficient process. They are then available in the form of humus-forming soil improvers.

Farm slurry is, thus, almost completely recycled, and the recycled components are returned to the soil, the announcement said.

Large-scale implementation and operator model

With SUEZ Germany, Fraunhofer IGB has now gained a licensee for the patented technology. The globally operating waste recovery and recycling company will invest in processing plants as an operator.

“Gradually, large-scale technical facilities are to be built, on a nationwide basis, to take surplus manure from farmers, breeding and fattening farms. Especially the logistical aspects of delivery will be taken into account when selecting the plant locations,” Kai Bastuck, head of recycling and recovery business unit development at SUEZ Germany, said in describing the business model.

“By recovering the finite raw material phosphorus, Germany's dependence on phosphorus imports is reduced. This conserves finite phosphorus resources and reduces pollutant inputs into soils. In this way, we contribute to a sustainable future and turn nutrients into valuable substances,” Bastuck said.

Fraunhofer IGB will support SUEZ Germany in further development of the process.

A first processing plant with a turnout of 1 cu. m per hour is currently being built as a “Living Pilot Plant” at SUEZ’s Zorbau site in Saxony-Anhalt, Germany. The flexibly designed plant will process cattle and pig manure and also fermentation residues from biogas plants, thus serving as a blueprint for further large-scale plants, the announcement notes.

“An average industrial-scale plant then produces about 100 kg of phosphate fertilizer, 100 kg of nitrogen fertilizer and 900 kg of organic, nutrient-poor solids per hour from 10 cu. m of raw slurry,” Fraunhofer IGB department head Siegfried Egner explained.

The potential savings in synthetic fertilizers are enormous. With a capacity of 1 million cu. m of liquid manure per year, which corresponds approximately to the quantity from around 100 swine finishing farms, a plant can produce 10,000 metric tons of ammonium fertilizer and 10,000 mt of phosphate fertilizer, Fraunhofer IGB said.

BioEcoSIM process

According to the institute, various steps are necessary to completely process liquid manure. In the first step, the aqueous liquid manure is pretreated so the phosphorus is completely dissolved. It is separated into a solid and a liquid phase by two-stage filtration.

The de-watered solid phase is dried using an energy-efficient process, also developed at Fraunhofer IGB, which operates with super-heated steam in a closed system and is, therefore, particularly energy efficient. The dried organic components can optionally be further converted to organic biochar at 450°C via a pyrolysis step — as in the drying step in an atmosphere of super-heated water vapor.

The liquid manure fraction contains the dissolved inorganic nutrients. In a precipitation reactor, phosphorus is first recovered and precipitated and filtered off as calcium phosphate, magnesium phosphate or magnesium ammonium phosphate. Nitrogen is recovered in a second step. For this purpose, the aqueous fraction is separated as ammonium sulfate by means of membrane distillation, and crystallized.

What remains is water that contains only traces of phosphorus and nitrogen but is rich in potassium; this can be used for irrigation purposes, Fraunhofer IGB said.

In extensive investigations and field studies, the Fraunhofer IGB researchers have shown that the mineral fertilizers and organic soil improvers prepared from farm slurry can be used directly as readily available fertilizers and humus-forming substrates in agriculture.