Agricultural transition calls for circular minerals

From a sustainability perspective, this is not optimal. The production of artificial fertilisers involves extracting raw materials and-consuming a lot of energy. And it’s not circular either: you already have the minerals in-house, but you need to dispose of them before reintroducing them in the form of fertiliser. Circular use of minerals could be a solution. Invest-NL conducted a market exploration among all parties in the supply chain to determine what is needed to turn circular minerals into a sustainable alternative.  

Some farmers are already experimenting with making their manure streams circular. Take De Hoeve Landbouw, the Brabant family business of Jacco Wink and Josien Boll in Wijk en Aalburg, which combines dairy farming with arable farming. They work according to a circular concept. This means, for example, that the dairy cows are fed with by-products from beans, soy pulp, and rejected potatoes. But also that they prefer to reuse the valuable fertilisers. 

To make this easier, De Hoeve works with separated manure streams: the manure and urine from the cows are removed from the barn separately. “When these two come together, you get ammonia,” explains Jacco Wink. “By using our urine separation system, we prevent that as much as possible, because ammonia plays a major role in the nitrogen crisis.” 

Mineral Separator 

A replacement for that supplementary fertiliser would be very desirable from a circularity and sustainability perspective. Technology for circular minerals does not always need to be developed on the farm of the farmer, because not every farm is as innovative as De Hoeve. Solutions can also be conceived elsewhere in the chain, for example by a party like MEZT.  

MEZT is a scale-up that has been working with TU Delft since 2020 to find technological solutions to reduce nitrogen emissions in agriculture. To this end, they have now developed a mineral separator. ‘We were inspired by devices that already existed in water treatment for extracting nitrogen from water,’ says Adriaan Lieftinck, CEO of MEZT. ‘They told us: “if you succeed in applying this to manure, you have found the holy grail.” Well, that breakthrough has happened.’ 

The MEZT mineral separator uses so-called membrane-electrodialysis technology to extract nitrogen, potassium, and phosphorus from manure for reuse. The concentrate is liquid; one method of applying it to the soil is via irrigation systems, known as fertigation.  

Lieftinck: ‘With this mineral concentrate, precision agriculture becomes possible: you can deliver exactly the right amounts of the various minerals tailored to the crop, the soil, and the season. The result is that we can use minerals circularily, with less nitrogen emission and phosphate leaching.’  

The prototype of the mineral separator is located in Delft, and by the end of 2024, a fully autonomous demonstration model in a portable container should be developed. ‘So that farmers and other manure processors can experiment with this new technology,’ says Lieftinck.  

Regulations are an obstacle 

MEZT approached Invest-NL to get the devices to market as quickly as possible. ‘The mission of Invest-NL is to make financeable what seems unfinanceable,’ says Rik Pantjes, team lead of Agrifood Business Development at Invest-NL. ‘In this way, we help accelerate social transitions, such as towards sustainable agriculture.’ Invest-NL initiated a survey to map the demand side of the circular minerals market. Pantjes: ‘What do farmers need, and how could circular minerals work on their farms?’ 

Conclusion? There are several barriers that mean farmers cannot yet fully adopt circular minerals as a replacement for fertilisers, and producers like MEZT cannot yet scale up their innovations.

‘One of these issues relates to infrastructure. Farmers currently work with fertilisers that have a fixed shape—they are granules. But mineral concentrate is liquid, which requires adjustments in how it is transported, stored, and applied. These adjustments necessitate investments. Additionally, it appears that knowledge about these new possibilities is not yet widely disseminated in practice.’ 

But the most significant obstacle relates to legislation. ‘Under current environmental regulations, mineral concentrate is classified as animal manure, and therefore can only be applied to land in limited quantities,’ says Pantjes. ‘The same minerals in the form of fertiliser are permitted. That is a strange discrepancy that hinders the flow of circular minerals. It is based on the idea that animal manure is waste, and therefore the minerals within it are as well.’ 

Lieftinck: ‘We are dealing with outdated regulations for new innovations. That never works, so changes are needed.’ 

Fertiliser is too cheap 

Solutions are already in development. ‘The European Commission aims to introduce regulations allowing mineral concentrates as “bio-based” fertiliser, the so-called Renure legislation,’ says Pantjes.

‘Renure stands for Recovered Nitrogen from Manure. That is a crucial step, but we do not yet know when this legislative process will be completed and which technologies will fall under the regulations.’ 

Market exploration shows that the business case for circular minerals can be strengthened if farmers collaborate in cooperatives. ‘About twenty companies collectively bring their fresh manure to the mineral separator, enabling scale advantages.’

Another promising option for a successful business case is to first digest the manure before separating it. This produces biogas or green gas, a valuable by-product that farmers can profit from. ‘However, land use plans often do not permit biogas production, so farmers find it difficult to obtain a permit for this.’ 

According to Pantjes, it is up to the government to quickly implement clear changes in the regulations. ‘Furthermore, you can consider incentive measures such as subsidies. Farmers wanting to work with circular minerals currently face competition from fertiliser that is effectively too cheap because the environmental impacts of its production are not priced in.’ 

Jacco Wink emphasises that for farmers, the crucial factor is what the price will be for that alternative to fertiliser. ‘We would like to work with MEZT’s mineral separator at De Hoeve, because the concentrate is even better than what we can achieve ourselves with our separated streams of manure and urine. But everything depends on the price. Farmers cannot simply pass higher costs onto their end prices, and profit margins are already tight.’ 

Precision Agriculture 

At De Hoeve, they are convinced that innovative technologies are necessary to enable circular and precision agriculture. They are already pioneering these efforts themselves. ‘Data is needed for precision agriculture,’ says Wink. ‘That's why we make soil scans to map the composition and conductivity of the soil. Based on that, we create a fertilisation plan. We also perform plant sap analyses to determine what nutrients the crop needs, so you don't give too much or too little.’ 

More data comes from the milk robot. When a cow comes by to be milked, the robot records the levels of protein, fat, and lactose in the milk. ‘Everything you do, you should want to measure,’ says Josien Boll. ‘But it’s not all about technology. I also want to look each cow in the eyes. To get an impression of whether its coat is in order, or if it is moving well.’ 

Wink adds: ‘Every morning, I make sure I have seen all my cows before 8 o'clock. First, I do that round, and only then do I sit behind the computer and review the data. It always confirms what I already thought. Ultimately, it’s about the combination of the farmer’s experience and the innovative technology.’