FISH POOP To The Rescue

A team of mainly women scientists in Mexico is working to turn tilapia waste into a solution to save water, ease pollution, and even make a dent in world hunger

January 31, 2020

3:56 pm

“I’m obsessed with waste,” says Marissa Cuevas Flores, a scientist from Mexico City. “We buy stuff, we use stuff, we throw it away. But there’s really no ‘away’.”

The 31-year old engineer sees waste everywhere. “Look around, wherever you are. Everything you see is going to become waste sooner or later. So what is going to become of all this stuff? Figuring that out — that’s my passion.”

That passion manifests in a circular-economy mindset that turns waste into solutions. Previously, for example, she launched a startup called Kitcel, which transformed styrofoam into wood varnish.

Now, Cuevas’ focus is on fish poop.

Her new venture, microTERRA, is a women-led team of scientists in Mexico, looking to use fish poop as a solution to help make a dent in world hunger, save water, and ease pollution.

The women-led microTERRA team (from left): Paola Constantino (CSO), Mariana Elias (Project Manager), Marla Lago (Chief of staff), and Marissa Cuevas (CEO).

The proof-of-concept lab work is being done far from the sea — in Guanajuato, smack in the middle of north-central Mexico, equidistant from the Pacific and the Gulf of Mexico. The fish at the center of this effort in question, though, is not an ocean-dwelling creature, but rather the fresh-water tilapia.

Fish farming, also known as aquaculture, has grown significantly in Mexico, producing almost 400,000 tons of seafood annually, responsible for almost half a percent of the country’s GDP. But there are many aquaculture challenges — including environmental hazards.

“Aquaculture farmers have two main problems,” notes Cuevas. “High fish-feed costs — over 60% of their costs go solely into feeding the fish. And large amounts of waste water — every day, 30% of the water in the fish tanks needs to be replaced, which is also a drain on fresh water sources.

“We address these two main pain points,” she notes. “We can save up to 75% of the fresh water that a fish farmer uses, and we can cover 40% of their fish-feed demands.”

Even more importantly, she notes, is stopping downstream pollution of waste water.

“Fish farmers release their waste water into the downstream ecosystem,” notes Cuevas, “and the impact of that is enormous. It contaminates the clean water and then no one can use it downstream. And it eventually reaches the ocean, but on the way down it pollutes the rivers, the lakes, and impacts way more people — it contaminates water all along the way. That is huge. We know that 70% of the world's freshwater goes to agriculture, and the biggest water pollutant is the excess of nutrients, that comes mainly from animal manure and fertilizer runoff: both flow into the rivers, lakes, and eventually the ocean, creating huge environmental challenges. And we know that aquaculture is expected to double by 2050. So for me, the super big question is: What will our rivers look like if we continue business as usual?”

So what does microTERRA actually do? It develops on-site water-treatment systems that use micro-algae to transform wastewater into a sustainable protein source for the tilapia while cleaning the water. In essence, it turns fish poop into fish food, which requires less changing of water, and thus produces less waste water.

microTERRA's on-site water-treatment system.

There are other residual benefits to this system, as well. “All of the SDGs are related,” notes Cuevas, referring to the UN’s Sustainable Development Goals. “When we are treating water with micro-algae, the micro-algae is also storing carbon, so it’s a carbon-drawdown solution. And water is a super-important resource, which we are going to have to take care of with the crisis of climate change. So the main source of water we are saving is ground water. When we store more ground water, and stop using as much, the opportunities of adapting to climate change multiply.”


Cuevas’ passion for science was stoked growing up the daughter of two chemists, whose idea of family fun was conducting experiments in which Cuevas and her siblings could participate.

“My dad would bring home different polymers,” she recalls, “that we would boil and try to form into new shapes. On vacations, we would do experiments, like evaporating sea salt from salt water, and then playing with the crystals to see what you could do with them, depending on the temperature. On a sunny day and a cloudy day, the formation of the crystals would be different.”

After a summer class at Singularity University, her interests veered toward biotechnology. “we could rediscover everything. Artificial Intelligence, 3D printing — this is the future for environmentalism. If we can learn these things to protect the planet, there is no limit.”

The goal down the line for Cuevas and microTERRA — which won’t be market ready until 2021 or 2022 — is to address similar pain points not just for aquaculture farmers, but for all livestock farmers. She believes the same solutions can be derived for pig and cattle farmers.

“We talk a lot about manure,” she says with a laugh.

But her mission is very serious. “The kind of pollution we are fighting is less visible to the eye, because it’s microscopic. But if you turn the biggest pollutant into resources, then you no longer have any problems. Instead of seeing something as a problem, we see it as an opportunity.

Subscribe to get notified of our weekly blog posts.