If enough people used the blend - 80% ordinary diesel and 20% diesel made from New Zealand rapeseed oil and recycled cooking oil - it would reduce fuel imports and greenhouse gas emissions, and Mr Barke wanted to be part of that.
The refuelling station, the first of its kind in New Zealand, was launched in March last year.
Mr Barke was cautious about putting his vehicles at risk, but it was not long before his fears disappeared.
From trialling biodiesel in two smaller vehicles, he now fills more than 35 of his Kiwi Discovery company vehicles, ranging in size from vans to buses, with biodiesel.
Soon he hopes to be able to do the same with his largest vehicles, the triple-axled Volvo buses on the Milford Sound tourist run.
"I thought someone had to dip their toe in the water and trial biodiesel otherwise we would never get it here. Now I'm really pleased with the results. It is working well for us. We have had no difficulties in performance or engine wear."
Mr Barke is the largest user within the Queenstown Biodiesel consortium, led by the Otago Polytechnic Centre for Sustainable Practice.
The biofuel is manufactured in Christchurch by Biodiesel New Zealand, a subsidiary of state-owned enterprise Solid Energy. The price is set by the fuel supplier and is at present about 2c less a litre than regular diesel.
Like Mr Barke, other potential users of the biodiesel were cautious at first, particularly as it was not known whether biodiesel would freeze in Queenstown's severe winter temperatures, consortium manager and polytechnic staff member Sharon Schindler said.
"We had 11 companies to begin with, each trialling one or two vehicles. Now everyone is very happy with the product and we are filling 76 vehicles."
So far, 200,000 litres had been pumped, saving an estimated 77 tonnes of CO2 from entering the atmosphere, she said. About 100,000 litres had been pumped in the past eight months.
Monthly figures reflected the huge jump in support, Ms Schindler, who is based in Queenstown, said.
In July last year, 6000 litres went through the pump, that figure almost quadrupling to 22,000 litres in July this year.
So successful has the consortium been, and so great is the demand from new members, the consortium was looking at "future-proofing" - moving from the small Queenstown Lakes District Council-owned refuelling site near Queenstown Hill to a larger, more accessible site with room for additional pumps and for larger buses, including Mr Barke's. Ms Schindler said she could not say yet where the new site might be.
The "word was spreading that biodiesel was OK", something Mr Barke said he was pleased about. The success of the Queenstown scheme was giving other local commercial vehicle operators the confidence to join, and encouraging other centres to start similar consortiums, he said.
Both he and Ms Schindler said their goal was for more motorists to accept biodiesel as a viable alternative and for it to be available at all service stations.
