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Which compost is best for our gardens?

Taranaki primary school students have found out how to recycle their food waste on site to make the best compost for their gardens.

Stratford students

Students at Matapu School and Stratford Primary School have found that using a composting tumbler is the overall best way to turn their food scraps into nutrition for their school vegetable garden.

The main experiment the students are doing is looking at how well plants grow in test and control sections of their school vegetable garden in response to different types of composting, such as Bokashi (a type of fermenting), worm farms, tumbler, and vertical or cold composting.

They are also doing lots of small studies on different aspects of composting, such as which living things break down the food, which foods can’t be composted and how temperature and air play a role.

types of compost

“I liked doing the experiments because it was my first time trying it and I liked the experience,” says Jahvana, 11, at Matapu School.

“I liked investigating the Bokashi system because it was new and different,” adds ten-year-old Eva from Stratford Primary School.

Matapu School Principal Kerry Nancarrow explains that they introduced composting as a way to change how the students think about waste. “We used to have a pig farmer come in and take the food scraps away and the kids didn’t even see where their waste was going or what happened to it.”

Marlene Lewis, environmental co-ordinator at Stratford Primary School, adds, “This project also helps the students to be more responsible when it comes to looking after the environment and nurturing the soil.”


The students enlisted the help of experts, including scientist John Coplestone at Industrial Chemistry Services who loaned the students some microscopes so that they could get a closer look at what were breaking down the food scraps.

“The kids really love the microscopes and go berserk just looking at everything they can find! I think every school should have a microscope,” he says.

girl and microscope

Students with microscopes

So far the students at Stratford Primary School have found some types of compost are better than others, helping plants in their plots grow more vigorously than plants in the experimental control – the section without compost.

“We found that that the cold compost and then the tumbler compost types are the best,” says 11-year-old Cian.

“The food scraps have to completely decompose, which takes about two or three months,” nine-year-old Addison points out.

Bottle compost

However students at Matapu point out that they had quite different results according to their school’s test plots.

“We’ve found that the tumbler compost is best and the vertical composting way was second,” Katie, 11, tells us.

Classmates Kate, 10, and Larni, 11, explain: “Our veggie patch is on land that is open to fertiliser from the fields around our school, but Stratford’s veggie patch is on land that was under a building before, so it didn’t have any fertiliser on it at all.”

Matapu group

Overall, the tumbler method is the one that fits both schools best because it was easy for the students to use and also kept out the fruit flies and rodents.

“We get 80 litres of food scraps per week, and the tumbler composting system is the only one that can really work at that scale and produce good quality compost in a relatively short time,” Marlene says.

Matapu school students

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About the project

Stratford logoMatapu logoCAPOW (Curious about Processing Organic Waste) is supported by funding from the Taranaki Participatory Science Platform (PSP) managed by Venture Taranaki.

Scientists and locals collaborating around a table

Participatory Science Platform

The Participatory Science Platform supports collaborative projects that bring together communities and scientists or technologists on research investigating a locally-important question or problem.

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