Mining the manure of the Netherlands' livestock
The Netherlands had to get rid of 11% of its dairy cows due to its phosphate surplus, which can be traced back to their large imports of feed.
Nearly 600 out of 16,000 dairy farms in the Netherlands closed down.
But one of the other ways they dealt with the phosphate problem, in order to comply with EU laws, has been to recycle livestock manure.
This is taken to the extreme at the Groene Mineralen Centrale, in the southeast of the country, developed by Groot Zevert Vergisting BV; the Wageningen University & Research (WUR); and Nijhuis Industries, with government support.
The installation takes in about 100,000 tonnes of manure and 35,000 tonnes of organic waste from local farms and food-processing.
The first mineral plant in the Netherlands, it was recently declared open by Her Majesty Queen Máxima.
Over 30-40 days, bacteria convert the manure into biogas and digestate, in eight large fermentation units.
Around three-quarters of this biogas will supply some of the electricity needed at the nearby factory in Borculo of dairy processor FrieslandCampina, one of the world’s largest dairy companies.
The remaining biogas is transformed into electricity for the Groene Mineralen Centrale, making the plant energy-neutral.
What is left will be supplied to the Dutch electricity grid.
Digestate will, after fermentation, be further processed into an organic soil improver, with low content of phosphate and nitrogen, and a fixed, singular phosphate manure that can serve as raw material for the fertiliser sector.
Another (wet) fraction is treated during various processes and filtrations, and will eventually result in a liquid fertiliser and clean water.
The nitrogen in that manure can replace chemical nitrogen as a fertiliser which is directly applied close to the roots of the crop by specially designed turf-care equipment and can therefore be used for precision agricultural techniques which more accurately control the growing of crops, to avoid waste.
Trials in 2018 showed that this fertiliser can replace chemical fertilisers.
The eventually remaining organic matter can be sold locally as a soil improver, or as a replacement for peat used by the potting soil industry.
While the nitrogen and potassium extracted from the manure is labelled as Green Meadow Fertiliser, and sold locally, the concentrated phosphate product recovered can be delivered to areas with a deficit of this plant nutrient, of which there are still many in Europe.
It’s a valuable raw material for making fertiliser, which doesn’t have to be imported from around the world, which is usually the case with phosphate.
It can also reduce dependency on the world’s finite phosphate rock resources, which are becoming more scarce and expensive, and concentrated in only a few countries, with Morocco controlling three-quarters of the world’s remaining high-quality reserves.
Because the phosphate product from Groene Mineralen Centrale is concentrated, it costs much less to transport.
Researchers of Wageningen Environmental Research contributed to the development of the Re-O-Eat technology for the digestion process.
It helps the Dutch livestock sector get over its problem is producing more minerals in the form of manure than can possibly be used on the country’s arable ground.
The Groene Mineralen Centrale is a leading example of improved utilisation of nutrients from agricultural waste flows.
This progress is required for the EU’s transition to a more circular, sustainable economy.
