Fermentation is a way to convert fish waste into an agroecological fertilizer: Sonia Ortiz

Approximately 65% of fish production corresponds to waste: heads, bones, viscera, galls, dark muscle, fins and skin. Sonia Ortiz, a regional cook and scientist with environmental and social responsibility, in her interest in giving sustainable treatment to these remains, found that it is feasible to ferment them and create an organic fertilizer with the potential to replace agrochemicals.

Ortiz is the host of the YouTube channel Cocina Al Natural and the television channel El Gourmet TV; and together with Celia Marín, she owns Aldea Avándaro, a Center for Research and Training for Field and Sustainable Cooking in Valle de Bravo. It is also part of Pesca con Futuro, where it promotes the responsible consumption and disposal of fish products.

In an interview with Causa Natura Media, Ortiz highlighted that fermenting fish waste can be a simple alternative for fishing cooperatives, fishmongers and supermarkets to responsibly process their waste.

*This interview has been edited for synthesis and better reading.

— How did the idea of fermenting fish waste come about?

Citlali Gómez-Lepe, who is president of the Mexican Council for the Promotion of Fishery and Aquaculture Products, is the owner, together with her partners, of the Nemi Natura trucharium in Zitácuaro, Michoacán.

She told me that when they sell the fish, they ask for the fillet and they are left with a lot of bones and viscera. Approximately the viscera and bones make up 20% (a figure that rises to 65% in various studies together with other wastes) of the product. Then she asked me what else could be done other than bury.

The heads are easy to use in a fish broth, but the part of the viscera remains, which are not something you can clean and eat.

That's where the ferment comes in. Fermentation is a way to take advantage of waste so that nothing is wasted.

— What is the procedure for fermenting fish waste?

The peculiarity of viscera is that they have many enzymes because inside the viscera is where food degrades. Taking advantage of those enzymes that are present in fish, I found an Asian protocol for fermentation.

The procedure is to chop the viscera and bones, and add the same amount of cane honey. Everything is placed in a well-sealed plastic drum, which is opened daily for stirring and then re-sealed. It is a fermentation in the absence of oxygen where the same viscera degrades protein into amino acids, and carbohydrates into simple sugars.

After four weeks, the ferment is stable and ready to be used, it is strained to remove possible residues and this is diluted to be applied either foliar or to the soil.

During fermentation, fish devours itself, because enzymes in the digestive tract break down bones and make them into small pieces. It is the fish itself breaking down through its enzymes.

— How does this process support sustainability?

This is a super agroecological ferment for fruit trees, it can even be used diluted to foliate vegetables. It is a very powerful fertilizer that will help us not to use agrochemicals. In four weeks you have it ready and it is a very powerful organic fertilizer that you can use without fear of poisoning the earth.

This is organic chemistry, and that produces things that don't kill soil life.

So my proposal to Citlali was to make the ferment in the trout farm and sell the fertilizer at a recovery price to avocado producers. It's a little bit comprehensive thinking.

— What results have you had with this biofertilizer?

I tried it with the fruit trees in Aldea Avándaro, we fertilize all the fruit trees and we have been doing it for two years now, and the amount of fruit that is produced is much greater, they do not fall off so easily, and they produce very beautiful fruits.

— Is it feasible to process all the fish waste we generate through this method?

It may seem complicated but it's not, it's a very easy way to use waste. You can do it in a small drum or you can do it in huge tanks.

It's not a culture that we have much here to consume fish ferments, but there is and it's perfectly scalable.

It can definitely be done anywhere. In the same places where fish are being torn apart, such as markets and fishermen, right there they could have their drum to pour out their entrails. I think it's a technique that, if we popularize it, could be of great help.

— Are there any projects that are already dedicated to this?

No, but it would be very viable, especially on the coast where there are fisheries and there is a lot of waste.

I don't do that, I'm really a chemist by profession and I like to research, and this is a protocol that I developed, but it's not a business that has to receive waste, but it's viable, it's viable and, definitely, it can be a product that has a value.

I believe that garbage doesn't exist until you create it. Sometimes we think that a shell is a waste and sending it to the compost is already a good thing, but sometimes there is still a process before it reaches the compost. We must always reduce the amount of waste that is discarded just because we don't know how to use it.