Fertilizer Ordinance Liquid manure, the underestimated raw material

Fertilizer Ordinance Liquid manure, the underestimated raw material

Fertilizer Ordinance Liquid manure, the underestimated raw material

The big protest action of the German farmers was answered promptly: Just a few days after the demonstration in Berlin, Chancellor Angela Merkel and Agriculture Minister Julia Klöckner (both CDU) invited to the big agricultural summit. The farmers in the Chancellery made many points, their frustration at being used as a scapegoat for many environmental damage, or the absurdity of the approaching ban on glyphosate without effective alternatives. Acutely, however, they were primarily concerned with one point: the new fertilizer ordinance. This should come into force in April of next year and would severely limit the spread of liquid manure on the fields.

The environmental and health policy benefits are immediately obvious: has exceeded the EU limit values ​​for nitrate at many measuring points, especially in the north of the country, for years – and has done so significantly. It is true that one can now discuss whether the restrictions that have now been chosen are too general. Hardly anyone questions that they are fundamentally necessary.

However, the regulation is extremely problematic for farmers. And for a very simple reason: you just don’t know what to do with all that slurry. In regions where animal breeding takes place on a large scale, significantly more manure is produced than the local soil can absorb. First of all, the fertilizer ordinance will therefore have the ecologically absurd effect that manure has to be exported supra-regionally and internationally, i.e. it has to be driven around the area with a lot of effort.

But that is expensive. And so many a farmer will soon wonder whether there aren’t alternatives. Is there. Because while the agricultural associations are still fighting to keep their routines, waste disposal companies and universities have been researching promising projects for the extraction of nutrients from residues such as liquid manure for years.

A first step towards further use is pretty obvious: manure consists of 90 percent water. In addition to indigestible feed residues and plant fibers, the remaining 10 percent also includes nitrogen and phosphorus, the two most important plant nutrients. Because of them alone, manure fertilization is very effective in moderation.

A project by the Fraunhofer Institute for Interfacial Engineering and Bioprocess Engineering in Stuttgart shows how these nutrients can be extracted from excess liquid manure. The manure is first divided into its liquid and its solid components. The phosphorus is then first dissolved from the liquid part by means of a so-called precipitation reactor. The liquid part is then passed through a membrane cell, whereby the nitrogen dissolves in the form of ammonia. Both can then be used as fertilizer. The solid part is dried, whereby the microorganisms are destroyed. It is then heated in the absence of air and thus converted into organic biochar. This in turn can serve as an energy source. All in all, 500 grams of phosphate fertilizer, 500 grams of nitrogen fertilizer and 900 grams of biochar can be obtained from 50 kilograms of pig manure.

At the end of the process, only one substance remains: water that only contains traces of phosphorus and nitrogen and is rich in potassium, which is why it is very suitable for irrigation.

Anyone who knows this chemical process wonders why it has not been used for a long time. The reason for this is simple: it’s too expensive. This is exactly where the Fertilizer Ordinance comes into play. Because it will increase the costs of manure disposal. This will surely become expensive for the farmers in the short term and then also have a corresponding effect on prices. What consequences it could have in the medium term, however, can be observed in a related field, namely the disposal of sewage sludge. Since it also contains nitrogen and phosphorus – to a much lesser extent than liquid manure – it was allowed to be dumped onto the fields together with the liquid manure for decades. But that will soon be banned. And so the prices for the disposal of sewage sludge have risen dramatically in the past few months alone. With an interesting consequence: incineration plants for sewage sludge are now being built nationwide, which will turn the supposedly useless broth into energy. And not only that: the first plants for the recovery of phosphorus are already in the planning stage.

Quite apart from the fact that some manure can also be processed in these plants, the development of sewage sludge shows what could also work with manure: First the costs increase due to new environmental regulations – but then a new market develops. In that, the farmers’ business models would work again. Better still, from the scapegoat that poisons the groundwater, their wastewater would turn them into what they have long been elsewhere: the suppliers of valuable raw materials.