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This month, it is biofuel which Kaikorai Valley College hopes to use later this year to generate some of its own electricity.
It is part of a project by the school's Young Enterprise Scheme pupils, who have established a biotechnology company called Kaika Energy, which is turning food waste into biofuel and fertiliser.
The school recently installed a ''bio-digester'' which breaks down organic material, and it is now producing biofuel and high-grade liquid fertiliser.
Kaika Energy managing director Sophia Taing said the company aimed to sell the fertiliser publicly as early as next month, in recycled plastic milk bottles at the Dunedin Farmers' Market.
But for now, it was being monitored to make sure pH levels were right, and it would be tested on the school's gardens first.
Kaikorai Valley College technology department head and Young Enterprise Scheme supervisor Peter Dodds said the company was also looking at building a large greenhouse before the end of this year.
Methane from the bio-digester would be used to heat the glasshouse, and the CO2 would be used to help grow the plants.
''We are also going to purchase a generator that runs on biofuel.
''We can use the gas to produce the electricity we need to heat the hot-water cylinder which heats the heating pad for the digester - so we'll have a complete loop of sustainable energy going on.''
He hoped the greenhouse and the generator would be operational before the end of the year.
''It's all very exciting. Especially when we only started in February. The company has done so well.''
Sophia said she was delighted at the speed the project was coming together.
She hoped the goals they had set would be achieved before the end of the year, so the next generation of pupils could take over and build on them.
''It would be nice to leave a legacy for them.''
The initiative was inspired by research which showed an estimated $900 million worth of food (120,000 tonnes) was wasted annually by New Zealand households, Sophia said.
Most of it was dumped in landfills, where it produced damaging greenhouse gases which were released into the atmosphere.
The company hoped to change that statistic, she said.
Ultimately, she would like to see a collection service established in Dunedin, where people could put their food waste in separate bins around the city, which could be collected alongside the city's recycling and refuse.
''Then, hopefully, there will be enough biofuel to run the school one day,'' Sophia said.
The bio-products would have a positive environmental benefit for Dunedin, she said.