Circular bio-based fertilisers support agriculture, rural economies and the environment

Innovative processing of agricultural bio-waste leveraging insects and microbes produces materials for bio-based fertiliser blends that perform similarly to traditional fertilisers while improving soil health.

Climate Change and Environment

Food and Natural Resources

Fertilisers are essential to boosting crop productivity needed to feed a growing population. However, the widespread use of conventional chemical and mineral fertilisers has led to unintended effects on water, air and soil. Contamination of groundwater and drinking water sources, and long-term soil degradation threaten future agricultural productivity, natural ecosystems and biodiversity. Energy-intensive production processes relying on fossil fuels together with nitrous oxide emissions from applied products worsen climate change. More sustainable fertilisers like compost and manure have been around for a while but their contents are not standardised, producing variable results with often suboptimal use of available bio-waste. The EU-funded RUSTICA(opens in new window) project brought together 18 partners from seven European countries and Colombia to develop tailored bio-based fertilisers for specific crops or farming methods in a circular economy paradigm – focused on minimising waste and maximising the reuse, repair and recycling of resources.

From fruit and vegetable bio-waste to bio-based fertilisers

“RUSTICA focused on five processes to turn underused plant-based organic materials like crop leftovers or food processing waste into building blocks for bio-based fertiliser blends tailored to different crops and farming systems,” explains project coordinator Liesbet Vranken of KU Leuven(opens in new window). A specialised platform converted bio-waste into carboxylic acids used to produce fertiliser building blocks in two other processes: microbial cultivation and filtration (electrodialysis). The microbial cultivation process produced nutrient-rich microbial biomass. Filtration extracted nitrogen, phosphorus and potassium from liquid by-products, creating a concentrate similar to key components in mineral fertilisers. RUSTICA’s insect cultivation process used agricultural bio-waste to grow insects as a source of biomass and frass (nutrient-rich insect waste). Finally, pyrolysis converted lignocellulosic waste from wood and plant materials into biochar, which improves soil health. Compost was also included in some blends.

Promising agronomic and environmental outcomes

“Our bio-based fertilisers showed promising potential to perform similarly to traditional fertilisers while contributing to improved soil health,” says Erika De Keyser of KU Leuven, RUSTICA research scientist. Regarding impact on the environment, most of the project’s novel blends performed better than reference fertilisers in many regions, especially Colombia. Where application rates (quantities per hectare) were higher, environmental impact was greater, pointing to areas for further research and optimisation.

Regional integration and upscaling support cost-effectiveness

Reducing costs will be key. While the price per tonne was lower than that of reference fertilisers, some of the bio-based fertilisers required much higher application rates – up to 35 times more. Both costs and environmental impacts can be reduced by adjusting blend compositions, integrating existing technologies and upscaling production. “Our technologies can be integrated with other locally available solutions – for example, bio-hubs(opens in new window) or waste-treatment systems, or even integrating local manure – to produce a range of mixed-blend sustainable products. This broader, integrated approach can reduce costs and make agricultural systems more resilient and sustainable in the long term,” adds De Keyser. “The RUSTICA project has the potential to transform fertiliser production with more sustainable, circular alternatives to mineral fertilisers. By reusing bio-waste streams and closing nutrient loops regionally, we can benefit both the environment and rural economies,” Vranken concludes. Continued research should bear fruit with innovative bio-based fertiliser blends that improve soil health, reduce environmental impact and ensure greater resource efficiency in agriculture.