BB/N003861/1

The aim is to reduce the reliance on external inputs to the farm, by providing fertilizer for the grass on which the cows feed, to use the waste from the cows to grow duckweeds, a very fast growing floating aquatic plant with a high protein content. To use the duckweeds as a substitute supplementary feed source for the cows and to use any organic waste left over to produce biogas.

The project aim is to create a circular farm by using manure from cattle to create struvite (magnesium ammonium phosphate is a mineral compound with the formula: NH4MgPO4.6H2O) and ammonium sulphate fertilizer; duckweed biomass to provide a substitute feed source for the cattle in place of imported Soya; and to use waste material from these processes in an anaerobic digester to create biogas that will provide both heat and power to the farm and the production process.

The manure is collected and digested in an anaerobic digester unit to produce biogas and a residue. The residue is speared into solid and liquid fractions. The solid fraction can be used a s a soil conditioner directly on the farm. The liquid fraction is used to make struvite by adding magnesium chloride, and also processed to remove nitrogen to form solid ammonium sulphate. The residue form this process, which is still rich in both phosphorous and nitrogen, is heated and passed into an indoor slow flowing lagoon system designed to optimize the growth of Lemna species, or duckweeds. The effluent is processed by the duckweed and leaves the lagoon within the limits for discharge to the environment or is recycled through the lagoon system until the discharge limits have been reached. The process is designed to be continuous, but this depends on a constant supply of cow manure and duckweed. Part of the research project is to determine what conditions favor the most rapid growth of duckweeds in this system.

The project aim is to create a circular farm. The electricity and heat will be generated by the biogas engine, fertilizer will be produced in the form of struvite and ammonium sulphate and the (protein rich) cattle feed by the duck weed. In this project the focus will be on the production of protein rich feed in the form of duckweeds. The goal of this project, is to do optimize the production of duck weed. The role of CEH will be to collect Lemna species form a variety of on farm locations in the UK and the Netherlands and to use effluent form the farm scale operation to select a suitable species mix that optimize removal of dissolved nutrient in low temperature situations, and produces a high protein basis for cattle feed and also provides some input to the biogas generator system as residue from the process. The end point of the CEH research will be a method for pre-selecting duckweed species mixtures for any farm scale operation by using small scale rapid selection procedures on a manageable scale, that can be implemented without technical equipment and can be undertaken by anyone interested in duckweed nutrient removal tank systems.The quality of the farm will be assessed by comparing milk production (quality and yield), the quality of the fertilizer produced, the amount of of heat energy and electricity produced.

In the Netherlands, there is quite a surplus of manure, which will increase with the lifting of the milk quota system in 2015. By this system, the production of milk in the Netherlands, but also in the UK and to less extent in Poland, can be increased on the same amount of land. In the Netherlands, an increase of 15% in the milk production is expected in the coming years. The stables for the cows are already enlarged, the processing capacity for milk is being installed at this moment for a value of about 1 billion euro in the North of the Netherlands. So, there are only two limiting factors left, the surplus of manure and the feed for the animals. The impact of this proposal will be to solve these limiting factors.

The dissemination will take place by demonstrating the system on a research level. The only way to convince farmers is by demonstrating the system and to prove that it solves their problem of the limiting factors to enlarge their capacity.

The environmental impact is high. It will solve the phosphate problem in two ways. The first problem is the surplus in the Netherlands. This will be solved in a proper way. The second one is the minimization of the use of the phosphate by recycling it for the fertilizer industry.

The systems will generate more renewable energy as the farm needs. So, the system will contribute to the goals of renewable energy production. The systems will generate renewable fertilizer, so in the way a complete bio-refinery system will be demonstrated producing energy, fertilizer and feed for the cows.