Microencapsulation of biostimulants and biopesticides at low temperatures

The pest biocontrol market is growing at 13% CAGR, and it is expected to grow from the $5.5 billion in 2022 to $15 billion in 2029. This growth has several complex reasons. The first one is the improvement of the ROI (Return on Investment) of the new biopesticides that encouraged the farmers to change their mind. Several years ago, the only farmers that used biopesticides were organic farmers, but nowadays the whole sector (organic and conventional farmers) is aware of the benefits of the use of biopesticides. Indeed, more than 70% of biopesticides are used by conventional growers. Most of the farmers combine conventional tools with new biopesticides, increasing the sustainability of the exploitation. This change of mind prompted the use of biopesticides, which are normally more preventive than curative. Namely, instead of waiting for the pest or disease to appear in the crop to use chemicals, they combine different biopesticides and ″light″ chemicals. This reduces the costs of the applications and the risk of resistance. Moreover, biopesticides usually have more than one Mode of Action, which also reduce the risk of resistance. Labour flexibility is another positive point of this kind of products, due to their shorter re-entry intervals, farmers can increase labour flexibility. Other reasons that are promoting the growth of this market are that they are exempt from residues, biodegradable, and they have lower carbon footprint. At last but not least, increased scientific knowledge on biopesticide formulation is increasing the availability of better biopesticides on the market. Indeed, a recent meta-study by Hernandez Tenorio et al. (2022) showed that the number of publications related to biopesticides formulation significantly increased by 71.24% in the last decade (2011 – 2021).

But it's not all good news; there are also serious problems in the sector that could jeopardize this promised growth. The two main threats to the sector are regulation and formulation difficulties. The regulations in Europe are some of the most restrictive in the world. In theory, the first target of the European strategy ″Farm to Fork″ is a 50% reduction in the use and risk of chemical pesticides. This is very important, but we must provide the farmers with tools to fight against the pests and diseases. If the EU wants to reach this target, it is essential to facilitate the registration of biopesticides, which it is not being done. In fact, the registration of biopesticides in the EU takes an average of 8 years (compared with 2 years in countries like USA, Brazil, or Colombia) and costs more than €1-2 million. 

Another big problem that companies face when they want to reach the market is formulation. Usually, they have a very good active substance (AS), but the formulation is not optimized, so the price, stability, effectivity, physical properties (dust, dispersibility, wettability), and shelf-life do not fill the need in the market. So, there are a lot of SMEs that invested 8 years and more than €1 million in registration in the EU and then failed because the formulation did not fill the farmers’ needs. Before starting the registration process for a new biopesticide, it is essential to develop the best formulation.

One of the most important strategies to improve the formulation of biopesticides is the encapsulation of the active substance. Thanks to encapsulation, the active substance can be preserved from the storage conditions, increasing the shelf-life of the microbe or the compound, and increasing its effectivity.

One of the newest ways of encapsulating is via a fluid bed. Fluid bed technology is the optimal technology for the individual design of granules from solid and liquid raw materials encapsulating different active substances at low temperatures.

Encapsulation of sensitive active substances by spray micro-encapsulation in fluid bed at low temperature.

Example of Elemental Sulphur biopesticide granulated by fluid bed at low temperature (AZUMO MG).

It involves suspending solid particles in a fluidized state by passing a gas or liquid through the particle bed, creating a fluidized bed. The main steps are: seed preparation, fluidization, granulation, in production tests, and discharge.

Why could fluid bed technology be the best solution to encapsulate an active substance or microbe? There are three main ways that fluid bed technology can help with developments where other technologies have problems. Firstly, the temperature of encapsulation and granulation is the lowest of the market. We can granulate at 40 – 50°C, which is very useful for thermolabile compounds that could have problems with temperatures above 60°C. Secondly, the final product is a dust-free granule, with safe application and beneficial consequences. Finally, the versatility of this technology is one of its most important advantages. Below, we will explain the different possibilities that we have to develop granules of very diverse origins (microbes, chemical products, plant extracts, algae, etc.). It is possible to encapsulate with a nucleus and different layers of compounds, with a single layer, agglomeration, etc.

Why do we choose encapsulation by granulation instead of other technologies? The water-soluble granules (WG) have several benefits compared to the powders: they do not generate dust, have good free-flowing properties, are easier to dose and transport, and have fewer handling hazards. Also, WG have some advantages compared to liquids or concentrated suspensions (SC). The granules have less weight and volume, no precipitation or settlement, a longer expiration date, and are easier and cheaper to ship.

We could classify encapsulation by fluid bed technology into four main types: spray agglomeration, spray granulation, spray microencapsulation, and spray coating.

The first technique is agglomeration where the powder is sprayed by binder droplets and liquid bridges. The particles are linked while drying to conform to the final granule with a ″raspberry structure″. This technique has several benefits, as the porosity of these granules makes them very dispersible with very good properties as WG, but with low protection of the active substance.

The second technique is spray granulation, where there is a homogeneous grain with an onion structure. This is very useful for solutions, emulsions, and suspensions in order to have a more protected active substance. In this technique the compound is sprayed and solidified in several rounds until the granule has the specified size.

The third technique is encapsulation by layered granules and it has several advantages. It is a dust-free granule with spherical pellet and excellent free flowing properties, dosing properties, dispersibility, and solubility. Also, the hygroscopicity of several compounds can be reduced. The narrow grain size distribution could be another benefit for several applications.

The fourth technique that is more complex is microencapsulation, where the active substance is sprayed in a matrix with the encapsulation material. During this encapsulation, the active substance is encapsulated with the protection material, forming a final granule that is specially protected.

The last technique is encapsulation by coating. In this two-step technique, the active substance is sprayed into a particle where it forms a nucleus. After this step, the granules are coated with a protective layer that provides exceptional protection.

Nowadays, there are several successful examples on the market of granulation and encapsulation by fluid bed technology that we developed. One important example is the AZUMO MG, 80% elemental sulphur, registered in Europe and approved for organic farming by ECOCERT. Also, we have formulations of encapsulation with very different active substances, such as microorganisms, amino acids, botanical extracts, or seaweed.

The AFEPASA R&D department specializes in the encapsulation of biopesticides, biostimulants, and fertilizers. We are one of the few companies in the world with laboratory equipment, a pilot plant, and an industrial plant. The industrial fluid bed drying plant has a production capacity of 8,000 tons per year. So, we are used to helping any kind of companies carry out projects from pure active substances to scale-up, and toll manufacturing. We are used to collaborating with multinational companies, SMEs, research centres, and universities.

AFEPASA was founded 130 years ago as a family company that specializes in agrochemicals. Our products are present in over 80 countries, of which 80% are used as fungicides, but also as fertilizers and biostimulants. Over time, the company has been transformed and modernized through a strategic plan based on research and development for new agricultural solutions as well as a global expansion plan for exporting our products to more than 80 countries in Europe, Africa, and Asia. Therefore, the company has doubled the number of talented employees and multiplied the investments in a state-of-the art infrastructure in just 10 years. AFEPASA has achieved in this way a steady growth, and, thanks to our investment in quality processes and workflows, we are now certified under ISO 14001, 90001, 45001, and EMAS, in addition to being awarded the Silver Medal of Sustainability by ECOVADIS in 2022.

This new facility was built under the concept of sustainable development. This production facility with more than three hectares of surface and 17,000 m² was designed with the best industrial equipment, the most sophisticated process control, and the most advanced technology available for micronization, sublimation, granulation, and mixing, becoming experts in phytosanitary formulation. Its capacity is more than 50,000 tons per year, complying with the most rigorous quality controls and environmental requirements.

Flow chart of the development and scale up of the encapsulation of a biopesticide in the AFEPASA facilities.

Facilities of AFEPASA in Tarragona (Spain).

It is important to highlight that in any complex production system such as ours, quality control is essential. In AFEPASA, we have a QC laboratory where 100% of the samples produced in the factory are analysed by more than ten parameters in order to ensure the perfect quality of the products.

To conclude, it is important to highlight the most important ideas in this article:

● Encapsulation is not just drying; it goes beyond, adding huge value to formulations.

● Encapsulation by fluid bed technology could be the best solution for commercializing an active compound.

● It is the most suitable technique for thermolabile compounds.

● It is a very good solution to avoid dust and save on transportation costs.

● AFEPASA is your ideal partner to research, develop, and toll manufacturing your new biopesticides. 

This article was originally published in the magazine 2023 Biologicals Special.