Her grandfather waters his garden with laundry water. She tested it for science
CBC News | Posted: March 20, 2025 6:00 PM | Last Updated: March 21
Also, what if all rooftops had solar panels?
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This week:
- Her grandfather waters his garden with laundry water. She tested it for science.
- The Big Picture: Voices for the wild
- What if we put solar panels on every roof in the world?
Her grandfather waters his garden with laundry water. She tested it for science.
This winter, there was a drought in India's Punjab province, where Tanvir Mundra's grandfather lives.
One of his tricks for saving water is to pour water from his laundry, known as grey water, onto his garden. It's a tip he shared with his granddaughter, who lives in Vancouver, during their regular Facetime calls.
And it inspired a science project that recently won Mundra first prize in the Earth and Environmental Sciences category of the Taiwan International Science Fair.
Mundra, now a Grade 10 student at St. John's School in Vancouver, asked her grandfather if his laundry water ever harmed the flowers, vegetables and herbs he grew. He said he never gave it much thought.
Mundra wondered if the trick to making that work was her grandfather's detergent.
"My grandparents, they're often telling me how nowadays we're always the ones using so many man-made synthetic cleaning chemicals when there are natural alternatives out there," she recalled.
For laundry detergent, her grandfather uses soap nuts — the fruit of a tree called Sapindus mukorossi, which is native to parts of southern and eastern Asia. They contain high levels of natural detergents called saponins. Eco-blogs and at least one environmental group recommend them as an eco-friendly soap, and they've even been pitched as a laundry detergent to CBC's Dragon's Den.
Mundra decided to test out her grandfather's method of growing plants with laundry water.
The first challenge was finding soap nuts, which aren't sold alongside other detergents at supermarkets.
Eventually, Mundra found some at a small specialty store in Vancouver.
Soap nuts don't work in the dispenser for liquid or powder detergents, but Mundra put a handful in a mesh bag and added them to the dirty clothes in her washing machine.
"They do work," she said, leaving behind a subtle scent that she described as being similar to "apple vinegar." (Others have said that soap nuts generally work well compared to commercial detergents. However, they don't leave your white clothes as bright and can stain fabrics that come into direct contact..)
The same bag of soap nuts can be used up to five times, she said.
Mundra collected the grey water from her soap nut laundry and from a load of laundry that used regular detergent.
Then she planted 30 spinach seeds, and watered each one with either soap nut grey water, regular laundry detergent grey water or tap water.
The regular laundry detergent water stunted the growth of the spinach plants — so, you might want to avoid using that for watering your garden.
But the plants grown with tap water and soap nut laundry water grew equally well.
"There's zero effect at all … in terms of plant height, leaf length, root length," Mundra said.
But did it affect the taste of the spinach?
Mundra said she was told she couldn't eat the spinach afterward, just in case "something goes wrong."
She's now doing more tests on more plants. She's also trying to find a way to extract the saponins from the soap nuts to develop a liquid detergent "that can fit into Western culture" and help people be more sustainable.
"If we can actually start reusing our own household water wastage, such as dirty water from the laundry, then we're actually saving and conserving a lot of water."
— Emily Chung
Check out our podcast and radio show. In our newest episode: It might not sound like a climate job, but mechanical insulators help make buildings more energy efficient. We head out to meet a young woman who trained in the trade through a program set up by the Youth Climate Corps B.C. The group, which trains young people around British Columbia for a wide variety of good, green jobs, hopes to expand across the country.
What On Earth drops new podcast episodes every Wednesday and Saturday. You can find them on your favourite podcast app or on demand at CBC Listen. The radio show airs Sundays at 11 a.m., 11:30 a.m. in Newfoundland and Labrador.
Have a compelling personal story about climate change you want to share with CBC News? Pitch a First Person column here.
Reader Feedback
Last week, Anand Ram wrote about a workshop in Toronto that helps people sort their waste into the right bins to maximize recycling. For a coffee cup, it recommended sorting the lid into "recycling," putting the sleeve in "paper," and the cup itself in the garbage. Zamani Ra, the event's host, later wrote in to say she'd been alerted that was incorrect. "The city reached out to me with an update to the blue bin that I wasn't aware of when we did our workshop," she explained. As of last July, coffee cups are accepted for recycling in the City of Toronto. Many readers also wrote in to point this out. Thank you all!
Write us at whatonearth@cbc.ca. (And feel free to send photos, too!)
The Big Picture: Voices for the Wild
Lisa Mintz is a Montreal librarian who turned to activism after becoming concerned about development that threatened trees and animals in a large urban green space called the Saint-Jacques Escarpment. In this portrait, by Quebec artist Lisa Kimberly Glickman, Mintz stands among fragrant sumac alongside a brown snake and a red fox, as chimney swifts soar overhead. Mintz is now the executive director of UrbaNature, a group that aims to provide nature-based learning in urban and suburban areas.
The portrait is part of a series called Voices for the Wild, featuring women among animals and in habitats they have fought to protect.
"I want to show that anybody can be an activist. You don't have to tie yourself to a tree or do research," said Glickman. She tries to include people from a variety of fields, such as novelist Catherine Bush, Green Party deputy leader Angela Davidson, and Dalhousie University professor Alana Westwood, as well as well-known activists Maude Barlow and Autumn Peltier.
She hopes the series will make people aware of these women's work and "hopefully, you know, spur people to action."
Glickman hopes to add several more women to the series. On her website, you can see more of the portraits and suggest women to include..
— Emily Chung
Hot and bothered: Provocative ideas from around the web
- Building the biggest plane in the world to carry huge wind turbines? Putting solar panels in space? CBC's Kyle Bakx takes a closer look at ideas being pitched by startups at an energy conference in Texas last week.
- The comic strip First Dog on the Moon explains why people who think the government is controlling cyclones are kind of partly right.
- Climate change is affecting the economics of the chocolate business in Canada. CBC's Ethan Williams looks at how hotter temperatures aren't just affecting where cocoa comes from, but where it's sold, too.
- Colombian marine biologist Fernando Trujillo has spent a lifetime working with endangered freshwater dolphins, which offer a window into the health of the rivers in which they swim
- In Finland, a survey found more than half of consumers say they're shopping less, and it's not because of tariffs. Here's why.
What if we put solar panels on every roof in the world?
What if every rooftop on Earth were covered with solar panels? A group of mostly Chinese scientists have calculated it could cool the planet up to 0.13 C by 2050. Zhixin Zhang and team published their modelling study in Nature Climate Change earlier this month. CBC's Johanna Wagstaffe takes a closer look at how they did the study and what the findings mean.
Thanks for reading. If you have questions, criticisms or story tips, please send them to whatonearth@cbc.ca.
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Editors: Emily Chung and Hannah Hoag | Logo design: Sködt McNalty