ReLEAF partners FiBL and ISQ have published a new study examining whether bio-based fertilisers produced from fishery side-streams can provide an environmentally preferable alternative to mineral fertilisers.
The study assessed three fertilisers made from different fishery residues: pellets produced from fish sludge, a solid fertiliser made from fish frames and heads, and a liquid fertiliser derived from fish viscera. Their environmental impacts were compared with those of mineral fertilisers using Life Cycle Assessment. The analysis considered both fertiliser production and their use in a field trial growing broccoli.
The results showed that environmental performance differed considerably between the three products. The pellet and solid fertilisers reduced global warming impacts and mineral resource use compared with mineral fertilisation. When assessed per kilogram of broccoli produced, these reductions ranged from 7% to 13%. The liquid fertiliser, however, had higher impacts in most areas, largely because its production required an energy-intensive concentration process.
The findings show that using recovered nutrients does not automatically guarantee a lower environmental impact. The production process, energy source, transport distances, nutrient release, crop yield, and application method all influence the final results. Field emissions were particularly important for acidification and nutrient losses to water.
The study identified several ways to improve future bio-based fertiliser systems. Production facilities should be located close to the source of the fishery residues, while drying and concentration processes should use more efficient technologies and renewable energy where possible. Application rates and methods also need to match crop requirements to improve nutrient use and avoid applying excessive phosphorus.
The publication provides useful evidence for ReLEAF’s work on the environmental assessment of bio-based fertilisers. It also highlights the need for further field trials, improved emission models, and more consistent Life Cycle Assessment methods so that different fertiliser products can be compared more reliably.
You can access the publication here.