Can Eggshells Save One of Mexico’s Most Polluted Rivers?

To combat industrial pollution, residents harness an unusual scientific solution.

Read this story in

Publication Date

Can Eggshells Save One of Mexico’s Most Polluted Rivers?

Aline Suárez del Real, GPJ Mexico

As the city of Lerma transformed into an industrial center, wastewater from factories made the Lerma River one of the most polluted in Mexico.

Publication Date

LERMA, MEXICO — Elvia Arias has lived near the Lerma River for most of her life. Since the 1960s, she has watched the area, about 60 kilometers (37 miles) southwest of Mexico City, transform into an industrial center, with hundreds of automotive, chemical, textile, pharmaceutical and plastic factories along the river, which runs about 700 kilometers (435 miles) northwest to Lake Chapala.

The population of the city of Lerma, in the State of Mexico, has grown exponentially as well, with nearly 3 million people now living along the river’s local watershed.

But factory wastewater and local garbage have severely contaminated the Lerma River, making it one of the most polluted in Mexico. Arias and other residents have grown accustomed to water from local wells, which are fed by the river, leaving stains and yellow film on appliances, toilets, sinks and tubs. The tap water’s intense odor causes headaches and dizziness.

So Arias was surprised to discover that one of her neighbors, Verónica Martínez Miranda, wasn’t experiencing these problems. Her appliances weren’t stained, and the water from her tap didn’t have a stench.

Martínez, a researcher at the Inter-American Institute of Technology and Science of Water at the Autonomous University of Mexico State, had developed a homemade filter, which she had placed in her well.

Arias was amazed, and asked Martínez if she and her neighbors could do the same thing. “She said that we could,” Arias says.

But there was one challenge, Arias notes: “We needed to gather lots of eggshells.”

expand image
expand slideshow

Aline Suárez del Real, GPJ Mexico

Elvia Arias arranges bags of eggshells collected from local residents.

Arias and Martínez co-founded the H2O Lerma With Charm collective, a group of citizens and environmental specialists whose mission is to improve the water quality in wells fed by the Lerma River.

Their main initiative has been to put together homemade eggshell-based filters for local residents, expanding on Martínez’s prototype. It’s both a gargantuan effort and a small, concrete step that residents can take to improve the local environment and safeguard their health.

“A lot of people ask why we need eggshells,” Arias says. “They ask me, incredulously, ‘How are you going to clean up such a serious problem with eggshells?’”

Keeping the Lights on in DRC click to read

Martínez explains the science behind the filters, which combine the shells with magnesium oxide and calcium hydroxide. “Ninety percent of eggshells are made of calcium,” she says. “Adding magnesium makes it so that heavy metals adhere to their ions, and that’s how the filter is formed.”

It’s a simple but effective solution. “Studies have demonstrated their effectiveness in the removal of colorants, carbolic acid, pesticides, heavy metals, pharmaceutical products, fluoride and organic material,” Martínez says. Water analyses have shown that the filters reduce heavy metals by 80% and fecal matter by 100%.

Since launching two years ago, H2O Lerma With Charm has grown to include 68 members. The group has installed seven filters in local wells to date and is preparing to install four more in the coming months. The Lerma River passes through five states – the State of Mexico, Querétaro, Guanajuato, Michoacán and Jalisco – on its way to Lake Chapala, and residents in other states now plan to install filters as well. Once in place, the filters are estimated to work for anywhere from five to 40 years, depending on the level of contamination.

expand image
expand slideshow

Aline Suárez del Real, GPJ Mexico

Combining eggshells with magnesium oxide and calcium hydroxide makes a simple but effective filter.

The biggest challenge is obtaining the vast quantities of eggshells required for the project. Each filter requires between 1 and 2 tons of eggshells – the equivalent of between 16,000 and 32,000 eggs.

Given the demand, Arias spends almost all of her time organizing the collection of eggshells. She began locally, inviting neighbors, friends and acquaintances to collaborate. She tried partnering with restaurants and bakeries, since they use a lot of eggs, but found these businesses couldn’t wash and dry the eggshells before the shells began to attract worms. Now, she focuses on collecting eggshells from households.

Through Facebook, Arias also coordinates 50 collection centers across the State of Mexico – homes or businesses that have volunteered to be eggshell drop-off points. And in recent months, volunteers have joined the effort and established 250 additional collection centers in other parts of the country, including Michoacán, Guanajuato and Jalisco.

Gathering enough eggshells for the first filter took about five months, but as word of the project spread, the collective was able to move more quickly. Now, they can collect 7 tons of eggshells in just four months.

“It’s necessarily going to be inclusive work, meaning that all of us will have to help,” says Mercedes Parna, a member of the H2O Lerma With Charm collective. “I don’t think there’s any other way to do it. The situation is serious and requires everyone’s participation.”

expand image
expand slideshow

Aline Suárez del Real, GPJ Mexico

Mariano Alamillo, a Lerma resident, hangs a sign at Elvia Arias’ home inviting people to drop off clean, dry eggshells.

The members of the collective recognize that homemade filters alone can’t solve the problem of pollution in the Lerma River. They also encourage local residents not to dump harmful household chemicals down the drain and advocate for stricter government regulations on how factories along the river discharge their wastewater.

Still, after years of watching the river grow more polluted, Arias and other members of the collective say it’s satisfying to at least be part of the solution.

“I long for the chance to see fish in the river,” Arias says. “My grandchildren are here, and they live here too, and maybe they’re going to stay here. I wish with all my heart that they won’t have to go through what I’m seeing happen.”

Aline Suárez del Real is a Global Press Journal reporter based in Tecámac, in the state of Mexico.


Sarah DeVries, GPJ, translated this article from Spanish.

Related Stories