A bamboo school and turning fried chicken oil into fuel — this is what school life has been for two young sisters making biofuel for school buses and a unique motorcycle in Indonesia.

For the past five years Britt Koens, 15, and her sister Marein, 17, have been attending The Green School, a renowned international school in Bali which has gained attention for its unique school curriculum.

The sisters moved to the region from the Caribbean island of Curaçao in 2014 when their father started a new job in neighbouring Timor Leste.

The sisters have lived in Bali and attended The Green School since 2014. ( ABC Kimberley: Tom Forrest )

Speaking to the ABC during a family holiday in Western Australia's Kimberley region, where their father is now working, they said their new school got them into a unique project: helping to build, maintain and fuel a fleet of biodiesel vehicles.

"It's great for kids like us to learn about these things," Britt said.

"There are so many options, for some people, project based learning is harder, so we have the options" Marein added.

Britt and Marein holidaying in Broome, where their father now works. ( Supplied: Britt Koens )

The idea behind the 'Bio Bus' was to start a sustainable way of transport to get the Green School's staff and students to and from school each day.

In the five years since it started, the group now looks after six school buses, all running entirely off used cooking oil.

"There is a group of us called 'The Grease Police', and we'll go out collecting oil from the restaurants," Britt said.

"We are bringing in about 300 litres per week."

After the oil is the collected and filtered, the chemical compound lye is added, which separates the cooking by product into glycerine and usable fuel.

The glycerine is then made into a liquid and bar soap, which is exchanged for used cooking oil from restaurants.

"It's a zero-waste program, that's the whole idea behind it," Britt said.

The Green School has seen the project acquire six buses in since 2014. ( Supplied )

Biodiesel motorbike

In addition to the fuel production, Marein helped build a biodiesel motorbike, which is believed to be one of Indonesia's first.

Working with a local mechanic, her classmate and a teacher from the school who founded the project, Kyle King.

Starting off with nothing but the engine, the team — Marein, a fellow classmate, Green School teacher and project founder Kyle King — worked on the bike for nearly two years, with support from local mechanics.

"We spent four hours a week working on the bike," Marein said.

"It was crazy, we had to change and adjust things to the motorbike, so when it finally started, and somebody drove it, we were so happy."

Project founder Kyle King and Marein Koens worked on the bike every week. ( Supplied )

The sisters have already started working on other alternative fuel sources.

"Another process we also started is with fermented fruit, bioethanol, which can go into the motorcycle engine," Marein said.

"Bio diesel can run in any diesel engine, you don't have to change anything."

After nearly two years the bike was completed and is fuelled entirely by biodiesel. ( Supplied )

Black market oil

Collecting oil in Bali isn't as easy as walking into a restaurant and asking for it, because used oil is sold in the black market.

After the bigger restaurants and hotels can no longer use the oil, it is re-packaged, and sold for half the price to smaller cafes and restaurants.

By the time the oil is disposed of, it could have been used up to 40-plus times, which poses health risks to the body; posing significant concerns to Indonesian authorities.

Used oil is re-packaged and sold on the black market to smaller restaurants and cafes. ( ABC: Eliza Wood )

"After three uses, cooking oil becomes unfit for consumption. It should, therefore, be processed into biodiesel fuel," Muhammad Suhud from a civil society group coalition told The Jakarta Post in 2015.

"The administration should prioritize the health impacts of an eventual regulation above all other considerations."

The students not only set out to ask restaurants for oil, but to also educate people on the matter.

"They never really want to give you the oil," Marein said.

"Because they make money off it."

Sustainable future

While Marein has now graduated, the sisters hope to eventually expand the project by getting other schools involved.

"Recently I've been in contact with a big hotel in Bali, now we've got them on board as well," Britt said.

"It's put the numbers [of litres] way up."

The school buses that run on biodiesel produce 80 per cent less carbon dioxide then a normal diesel engine.

The sisters said they want to continue to look for more sustainable transport methods, and encourage others to do the same.

"If you're passionate about it, you can do it, and it will help you so much, and teach you," Britt said.

"It's a project that is continually growing."