Market and product

Compiled by Bao Hien

The controlled-release fertilizer industry has long relied on microplastic coatings to regulate nutrient release — but that same coating is becoming one of the more persistent sources of microplastic residue in farmland soil. A research project in Canada, which just received additional federal funding in September 2026, is testing a plant-based, fully biodegradable alternative.

The problem: "invisible" microplastics in farm soil

Most controlled-release fertilizers on the market today are wrapped in a synthetic polymer shell designed to slow dissolution, so nutrients — nitrogen in particular — are released gradually in step with actual plant uptake rather than being lost right after application. However, not all of these coatings fully break down over time, leading to microplastic fragments accumulating in the soil across successive growing seasons. Recent studies have found that these microplastics can migrate into the tissue of the very crops grown in that soil, raising questions about their path into the food chain.

This isn't a regional issue. The European Union has banned the use of microplastics in certain agricultural products — including seed and fertilizer coatings — effective since October 2023, forcing manufacturers worldwide to look for alternative materials if they want access to that market.

The solution: replacing plastic with surplus plant starch

One approach being pursued by a research team in British Columbia, Canada uses surplus plant starch — sourced from byproducts of pulse crop processing — as the core material for fertilizer coatings, replacing petroleum-based polymers. Functionally, this biological coating performs the same nutrient-release-control role as a traditional plastic coating, but it fully biodegrades in soil once it has done its job, leaving no microplastic residue behind.

Technically, slow-release technology — regardless of the material used — pursues two goals at once: reducing the amount of fertilizer needed per growing season (by limiting losses to leaching or volatilization), and cutting greenhouse gas emissions, particularly nitrous oxide (N2O) — a greenhouse gas released when nitrogen in fertilizer is converted by soil microbes and escapes into the atmosphere instead of being absorbed by plants.

Beyond coatings: a different approach to micronutrients

The same research team had previously developed a related approach for micronutrient fertilizers: rather than using sulfate salts or synthetic chelating molecules like EDTA (ethylenediaminetetraacetic acid) to help plants absorb zinc, iron, manganese and copper — substances prone to residual buildup and groundwater pollution — the new method binds these micronutrients directly to cellulose fiber, using cellulose as a carrier that releases them gradually. According to the developers, this approach cuts overall nitrogen fertilizer demand by 20-30% and is said to help retain carbon in the soil.

Funding and expansion plans

The starch-coating project for controlled-release fertilizer has just received federal funding worth up to $1,976,150, announced on September 16, 2026 through Canada's Agricultural Clean Technology program — a second round of funding after an earlier $1.33 million grant in 2022 that focused on a related product, a biodegradable seed coating. The new funding will be used to extend the biological coating technology already developed for seeds into the fertilizer sector — a substantially larger market.

The project involves several independent research and testing partners, including an agricultural analysis laboratory and an international certification body, alongside a university chemistry department in Canada. The policy goal behind the investment is to support Canada's commitment to cut greenhouse gas emissions from fertilizer use by 30% by 2030, measured against a 2020 baseline.

Open questions

Although the bio-based approach is seen as promising, the controlled-release fertilizer industry still has several technical questions to resolve before it can fully replace microplastic coatings at commercial scale: the mechanical durability of a starch coating during transport and storage, the ability to keep its breakdown rate stable across different climates and soil types, and production costs compared with traditional plastic coatings that have already been optimized for industrial-scale manufacturing over several decades. These are the factors that will determine whether this technology can move beyond the pilot stage to become a mainstream choice in the global fertilizer market.