In this article, we will introduce how DSS participated in the development of a new Bio-degradable Fertilizer Coating. A fertilizer is any material, whether organic or artificial, that is applied to soil or plant tissues. It supplies crops with essential nutrients and enhances productivity. While many sources of fertilizer exist, modern agricultural practices primarily focus on three main macronutrients: nitrogen (N), phosphorus (P), and potassium (K). Depending on the crop type, farmers often supplement specific nutrients, such as rock dust, to provide necessary micronutrients.

Farmers and growers utilize fertilizers in various ways to maximize efficiency. They apply fertilizers through dry, pelletized, or liquid methods, frequently using large agricultural machinery or hand tools. Notably, the industrialization and scientific breakthroughs of the 1800s transformed fertilization practices significantly. As a result, these advancements led to innovations in plant nutrition and fostered a new agricultural industry that thrives on synthetically created fertilizers. This evolution underscores the importance of fertilizers in modern agriculture, driving productivity and sustainability.

he transformation of the global food system has significantly enabled large-scale industrial agriculture and substantial crop yields. Since the 1800s, the world population has increased sevenfold, driving a continuous demand for crop innovations. Consequently, farmers and agricultural researchers face increasing pressure to develop more effective strategies to enhance food production. Despite many advancements over the years, the need for efficient product yields remains crucial. This efficiency is essential not only to satisfy the demands of a growing population but also to do so with limited resources.

Several factors, including the loss of soil fertility, the prevalence of pests, and nutrient deficiencies, have contributed to a decline in agricultural production. These challenges have heightened the urgency for innovative solutions. Between 1961 and 2021, the use of nitrogen fertilizers surged by an impressive 800%. This remarkable increase directly resulted in a 30% rise in per capita productivity within conventional farming methods.

As a result, while nitrogen fertilizers have played a pivotal role in enhancing crop yields, they also raise questions about long-term sustainability and environmental impacts. Therefore, the agricultural sector must balance the benefits of fertilizer use with the necessity for sustainable practices that protect soil health and biodiversity. Ultimately, addressing these challenges will be vital for ensuring food security in the future.

Fertilizers generally fall into two categories: inorganic and organic. These categories include various types, such as nitrogen fertilizers and phosphorus fertilizers.

Nitrogen Fertilizers
Nitrogen is a crucial component of chlorophyll, playing a vital role in photosynthesis. It is also part of amino acids in plants. Nitrogen fertilizers enhance production yield and improve crop quality.

Phosphorus Fertilizers
The efficiency of a fertilizer depends on its phosphorus content. Phosphorus is found in the protoplasm of cells and is essential for cell growth and reproduction. Phosphorus fertilizers are invaluable for developing strong plant roots.

Inorganic Fertilizers
Inorganic fertilizers are artificially produced and contain minerals or synthetic chemicals. They often include phosphorus, potassium, and other nutrients derived from mining. Inorganic fertilizers can come in single-nutrient or multi-nutrient formulations. Multi-nutrient fertilizers offer a complete and balanced nutrient profile, including nitrogen, phosphorus, potassium, and micronutrients like calcium, magnesium, boron, and manganese.

Organic Fertilizers
Organic fertilizers are derived from plant and animal sources. They enrich the soil with carbon compounds essential for plant development and increase the organic matter content of the soil. This enhancement accelerates the growth of microorganisms and modifies the physical and chemical properties of the soil.

In 2015, the European Commission introduced its Circular Economy Action Plan to promote a more resource-efficient economy in Europe. A key priority of this plan is to reduce plastic use and waste. Consequently, the EU’s Fertilizing Products Regulation, which stems from this action plan, establishes guidelines for slow-release fertilizers.

Given that current polymer encapsulation systems may not comply with future restrictions, the industry must adapt. Therefore, it is essential to develop biodegradable products before 2026. In response to this need, Delft Solids Solutions has recently applied a new biodegradable fertilizer coating, significantly contributing to the development of Kaumera coatings. This innovation underscores the commitment to sustainability in agriculture and resource management.

Kaumera is a new bio-based raw material extracted from the sludge granules formed during the Nereda® purification process. Its unique properties—ability to repel and absorb water, fire retardancy, and suitability for coatings and composite materials—make it versatile. Currently, applications in agriculture are proving to be very promising.

Kaumera is a biodegradable coating developed to replace traditional plastic coatings. Extracted from wastewater, Kaumera helps reduce the need to remove and process sludge by 20-35%. As a biodegradable, recyclable, and renewable natural product, it presents a viable solution with several environmental advantages.

Kaumera offers a positive impact on energy consumption and reduces CO2 emissions, which are currently major contributors to the greenhouse effect. By utilizing this innovative material, we can promote sustainability and mitigate environmental strain.

The recovery of Kaumera from wastewater occurs within the National Kaumera Development Programme (NKOP). This program involves collaboration among several key organizations, including the Vallei and Veluwe Water Authority, the Rhine and IJssel Water Authority, the Dutch Foundation for Applied Research in Water Management (STOWA), Royal HaskoningDHV engineering consultancy, ChainCraft, and Delft University of Technology. These parties have worked closely with Delft Solids Solutions to introduce Kaumera.

Each organization has contributed its knowledge and expertise to retrieve, process, and market this new raw material, spanning from laboratory research to full-scale recovery. This collaborative effort exemplifies how water authorities, the scientific community, and the business sector can work together to promote a sustainable, circular economy.

The coating drum features a rotary design that rotates at a controlled speed while fertilizer granules are continuously fed into it. Positioned at a specific angle, gravity aids in moving the material through the drum within a designated time frame. As the material travels through the drum, a spraying system applies the coating material onto the material bed.

This continuous movement enables the achievement of a uniform coating that is homogeneously distributed over the numerous granules. The spray systems must be meticulously designed for optimal distribution of the coating agent, considering factors such as spray locations, nozzle types, bed depth, and rotational speed.

Additionally, a high volume of elevated temperature air, around 60°C, heats the fertilizer granules during their movement in the drum. This heating facilitates relatively fast drying of the coating material, helping to prevent the dissolution of water-soluble fertilizer granules.

After the coating process, the quality of the coating can vary based on the coating material, process settings, and granule size. Delft Solids Solutions specializes in quality control of the coating by utilizing various analytical methods.

In addition to coating morphology, the dissolution rate is another critical parameter that determines coating quality. After the coating process, we screened the differently coated granules in water at a constant temperature to assess their performance. We monitored their dissolution performance, observing how the coating layer deformed and disintegrated in the water.

The results of the dissolution times are presented in Figure 5. This figure illustrates the dissolution results after 5 minutes in the solutions. Notably, the uncoated granules show no remaining particles, while the coated granules retain their shape. Furthermore, the granules with good coating maintain their shape better than those with bad coating.

To study coating thickness and uniformity, microtomy can create precise cross-sections of coated granules. These slices are then examined using light microscopy or electron microscopy, allowing us to visualize and quantify the coating thickness while assessing uniformity.

As regulations continue to increase, it becomes essential to develop the latest generation of biodegradable fertilizer coating methods. The Delft Solids Solutions laboratory provides various testing methods to evaluate and fine-tune multiple variables for optimal product coatings. Key optimization tools include rotational speed, coating feed rate, material feed rate, spray locations, and tumbling flight design.

At Delft Solids Solutions, we can test all these variables and more, gathering the necessary data to design a viable commercial-scale coating process. As a leader in the powder and granule field, our coating drum and spray systems are specifically designed to deliver optimized coating solutions tailored to meet your product’s unique needs.