Katarzyna Chojnacka: Bio-based fertilizers: A practical approach towards circular economy

Katarzyna Chojnacka
Professor
Faculty of Chemistry, Department of Advanced Material Technologies
Wrocław University of Science and Technology
Poland

Introduction
Efficient nutrient management reduces eutrophication in the Baltic Sea region through buffer zones, controlled drainage, and cover crops that limit runoff. Excessive synthetic fertilizer use leads to phosphorus and nitrogen pollution, harming water ecosystems. Bio-based fertilizers (BBFs), derived from organic waste, recycle nutrients and offer a sustainable alternative to conventional fertilizers. Their use decreases reliance on imported phosphate rock, stabilizes costs, and strengthens farmers' resilience.

Replacing synthetic nitrogen fertilizers lowers agriculture’s carbon footprint by reducing dependence on the energy-intensive Haber-Bosch process. Struvite and digestate-based fertilizers provide slow-release phosphorus and organic matter, improving soil fertility while reducing nutrient leaching. Biochar enhances water retention and carbon sequestration. However, BBF adoption requires research on nutrient efficiency, regulatory clarity, and financial incentives.

Integrating BBFs with precision agriculture improves nutrient uptake and reduces waste. Variable rate application (VRA), nutrient mapping, and sensor-based monitoring optimize BBF distribution, minimizing losses and increasing yields. The EU Farm-to-Fork Strategy supports these practices to reduce synthetic fertilizer use and promote organic alternatives.

Production technologies and applications
BBF production varies in duration, composition, and environmental impact. Fermentation takes 2–4 weeks, yielding digestate rich in nitrogen and organic matter, often used in biogas plants. Microelement extraction, completed in 24–48 hours, enhances plant micronutrient uptake using algae and fish residues. Microbial enrichment, lasting days to weeks, introduces phosphorus-solubilizing bacteria (PSB) and nitrogen-fixing microbes to improve nutrient availability in phosphorus-deficient soils.

Biochar enhances soil structure, retains water, and sequesters carbon. It reduces nitrogen leaching and extends fertilizer efficiency. Composting, lasting 4–8 weeks, supports microbial diversity and organic matter retention, making it a scalable solution for farms processing agricultural residues. Struvite recovery from wastewater provides slow-release phosphorus, reducing dependence on mined phosphate rock. Biodisinfection, conducted at 30–40°C for several days to weeks, introduces volatile fatty acids and antimicrobial compounds to suppress pathogens and enrich organic matter.

Scaling BBF production requires a steady supply of organic residues, including manure, crop waste, and food processing by-products. The Baltic Sea region generates large volumes of these materials, but infrastructure differences affect availability. Strengthening cooperation between BBF producers and waste sectors can improve nutrient recycling, reduce reliance on imported fertilizers, and support local economies. Efficient supply chains and optimized feedstock use will promote BBF adoption and reinforce circular economy principles.

Implementation in the Baltic Sea Region
BBF adoption varies across the Baltic region. Finland's subsidies, covering up to 30% of production costs, have accelerated industrial-scale use. Germany and Denmark, benefiting from strict fertilizer limits and circular economy policies, lead in implementation. Poland, Lithuania, and Latvia face slower adoption due to regulatory delays, limited infrastructure, and seasonal feedstock variability. Sweden promotes biochar through tax deductions and government trials in cereal production. Estonia and Lithuania focus on digestate-based fertilizers, integrating biogas production with nutrient recycling. Germany has expanded struvite recovery, particularly in Hamburg, as part of circular economy initiatives.

Despite regulatory improvements, adoption remains slow due to inconsistent policies, complex certification, and limited farmer outreach. Expanding subsidies, technical support, and demonstration projects could accelerate adoption. Aligning national regulations with EU directives would facilitate market growth and cross-border cooperation.

Economic and policy framework
BBF economic feasibility depends on production scale, feedstock availability, and policy support. Fermentation and biodisinfection benefit from biogas revenue, offsetting costs. Composting is a low-cost, scalable option supported by subsidies. Biochar production requires high initial investment but provides long-term soil health benefits. Struvite recovery is cheaper than phosphate rock but demands advanced processing infrastructure. Regulatory inconsistencies and lengthy approval processes hinder market expansion.

Strengthening public-private partnerships, improving certification processes, and standardizing BBF quality will increase adoption. Expanding financial incentives and reducing investment risks will support farmers transitioning to BBFs, making them a viable alternative to synthetic fertilizers.

The EU Fertilizing Products Regulation (EU 2019/1009) sets certification standards, ensuring BBF safety and limiting heavy metal content. The EU Farm-to-Fork Strategy aims to cut nutrient losses and fertilizer use, aligning with HELCOM environmental objectives. However, regulatory inconsistencies, high production costs, and infrastructure limitations still slow BBF market expansion. Coordinated policies, financial support, and risk-sharing mechanisms can improve adoption.

Stakeholder recommendations
Policy and regulation

• Set clear targets to reduce synthetic fertilizer use.
• Expand financial incentives to improve BBF competitiveness.
• Harmonize HELCOM and EU regulatory frameworks.

Agricultural sector

• Implement precision agriculture (GPS guidance, nutrient mapping) to optimize BBF efficiency and minimize runoff.
• Provide training on BBF benefits and application methods.

Industry and innovation

• Standardize BBF quality protocols, specifying nutrient content and labeling.
• Enhance microbial enrichment with PSB and nitrogen-fixing microbes.
• Increase regional organic waste use in BBF production.
• Strengthen public-private partnerships to scale BBF manufacturing.

Long-term research should evaluate BBFs' effects on soil microbial balance and nutrient cycling. Continuous use influences microbial composition, organic matter turnover, and nutrient bioavailability. Understanding these dynamics is essential for soil fertility, particularly in intensive farming.

Consumer education

• Promote awareness campaigns on BBF environmental and nutritional benefits.

Enhancing BBF efficiency, adoption, and policy integration
Research priorities

• Soil and microbial dynamics - Assess BBF effects on microbial diversity, nutrient cycling, and carbon sequestration in phosphorus-deficient soils. 
• Nutrient retention - Compare BBFs and synthetic fertilizers in nutrient leaching, focusing on biochar’s role in retention and carbon sequestration. 
• Lifecycle and economics - Evaluate production emissions, energy use, cost-effectiveness, and long-term soil benefits of BBFs. 
• Regulation and market growth - Simplify certification, trade, and policy alignment under EU and HELCOM frameworks while improving financial models. 
• Agricultural integration - Examine BBF interactions with pesticides, herbicides, and irrigation for better nutrient and pest management. 
• Scaling production - Optimize feedstocks and processing to improve efficiency, reduce waste, and ensure consistent quality.