Kaitlyn and Jessica Lamb want more students to turn food scraps into fresh food through the art of composting.

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If you’re keen to reduce your climate impact, diverting food waste from landfill is one of the easiest steps you can take, according to compost queens Kaitlyn and Jessica Lamb. The twin sisters are second-year students at the University of Canterbury, where they’ve established a new offering on the campus clubs list: the UC Compost Club. The pair, originally from Rotorua, first got into composting when they realised the considerable climate impact of rotting food in landfills, which releases the greenhouse gas methane.

Now, through the Compost Club, Kaitlyn and Jessica are teaching their fellow students how to make the most of their waste – because despite having “green” organic bins across campus, food scraps make up 41% of the “red” landfill bin contents. The club is still in its infancy, but Kaitlyn says she was surprised by how many like-minded students they’ve united: “We’ve got like 30 sign ups, which is amazing.” Education is a key goal of the group – they’re offering mini-tutorials, where students can book a visit to their flat and for help setting up a compost pile in their backyard.

Kaitlyn and Jessica also run workshops, complete with live compost pile construction, with three tiers of compost commitment to suit different lifestyles: time-poor composter, good citizen composter, and compost fanatic. They cover different types: cold, hot and worm-based systems. Most backyard set-ups are cold compost, where material is added slowly, meaning the microbes eat slowly, says Kaitlyn. Then, there are the four essential compost components: browns (leaves, hay, wood chips, etc.), greens (food scraps), moisture and oxygen. “Normally we try to explain it like a cake: you have to have all the right ingredients so that it tastes good – or it tastes good for the microbes,” says Kaitlyn.

When it comes to barriers, one of the biggest is that “people think it’s smelly,” says Kaitlyn. Or it attracts flies, or doesn’t break down. These can easily be overcome if you keep a good brown-green balance and add water if the mixture is too dry. And if you’re a vermicomposter (aka worm farmer), you might’ve heard it’s a no-no to add citrus peel and onion skins into your system – “but we do it,” says Jessica. “You just have to check the pH balance – if it’s too acidic, the worms will want to escape.” But you definitely shouldn’t put meat or dairy into your backyard compost, as there won’t be enough heat in the pile to kill off nasty pathogens. That can only be achieved in very large compost piles, which can reach the hot composting threshold of around 60 degrees, says Kaitlyn.

On a Friday afternoon, Jessica and Kaitlyn can often be found at the Waiutuutu Community Garden, tucked away in a lush corner of the UC campus. Here, students gather for a working bee, with compost one of the tasks on offer. Large receptacles are set up along the garden edge. “When people get the composting job, they’re often really into it,” says Kaitlyn. “There’s usually some students who really do like worms as well.”

Last year, Kaitlyn and Jessica collected food scraps from the halls of residence to top up the community compost heaps. It takes about a year for the heaps to fully turn over into rich “black gold”, which is then applied to the garden’s raised beds of vegetables. Working bee participants get to take home fresh produce grown here. It’s a chance not only for some fresh kai, but to switch off from screens and soak in the surrounding greenery.

“Some people think living sustainably is more expensive, that you have to buy all this stuff like bamboo toothbrushes,” says Kaitlyn. “But if you break it down, it’s not really. It’s just living with what you have and just living more simply.”