TunaMud: a multi-purpose fertilizer from the canned tuna industry

Tuna is the world’s most commercially valuable fish. More than 60% of tuna fish caught worldwide is used by the global canned tuna industry. The latter industry had revenue exceeding $20 billion in 2024. Before being packaged by canned tuna industrial companies, tuna’s meat is cooked. The broths that derive from the tuna cooking process are fed to a wastewater treatment plant together with scraps that derive from the cutting phase of the raw tuna, the blood and the so-called sawdust composed of small fragments from the cutting are sent to the water treatment plant along with the aqueous exudate released by the tuna in the conditioning phase after cooking. Dubbed herein “TunaMud”, we show in this study that the sewage sludge residue resulting from wastewater treatment at canned tuna industry factories is a multi-purpose fertilizer. Tested on arboreal (olive and pomegranate), herbaceous (pepper and lettuce), and horticultural (onion) plants, TunaMud improved the growth parameters of all plants grown, as well as the quality of fertilized soil. A biological resource so far disposed of as biowaste at substantial economic cost is thereby turned into a valued fertilizer. Along with recent outcomes concerning tuna industrial processing waste upgrade into valuable bioproducts via the LimoFish process, these findings close the material cycle through technically and economically viable circular economy processes for all by-products of the global canned tuna industry, including the mud-like residue from the wastewater treatment plant. While the use of food waste as fertilizer is not new, the innovation of this work lies in valorizing a previously unstudied industrial residue: the wastewater-treatment sludge generated specifically by the tuna-canning process. The composition of TunaMud, arising from a unique combination of cooking broths, blood, cutting scraps, and conditioning exudates, has no equivalent in the existing literature on organic fertilizers. The study further introduces a genuinely interdisciplinary approach that integrates green chemistry, wastewater engineering, agronomy, circular-economy analysis, and public-health considerations. Besides providing farming companies with a multi-purpose organic fertilizer free of antibiotics, these findings provide the canned tuna industry with the opportunity to save substantial waste disposal costs that in Europe approach €300/t. Benefits of TunaMud employment may be significant also for public health and the environment. Manure contaminated with antibiotics and resistant bacteria quickly increases the amount of antibiotics residues and antibiotic resistance genes, reducing the microbial diversity of the soil and driving widespread antimicrobial resistance. The approach to use fish biowaste as a source of organic fertilizers produced using innovative green chemistry (AnchoisFert) and green chemical engineering (TunaMud) technologies, provides an example of the required integration of disciplines working with industry to foster human health along with that of animals, plants and wider ecosystems. The use of locally produced waste marine biomass, naturally free from antibiotics, significantly reduces dependence on fertilizer markets, while lowering and stabilizing agricultural production costs. By transforming an abundant, renewable, and underutilized resource into a valuable agricultural input, this approach strengthens local economies and supports environmental sustainability. For public health systems, reducing the spread of antibiotics and antibiotic-resistance genes into agricultural soils directly addresses one of the key global priorities.