A popular cafe has created a storm in a coffee cup by refusing to provide takeaway cups to customers staying on the premises.

Buoy Cafe at Westhaven Marina, Auckland, updated its hot drink policy three months ago after throwing away more than 100 coffee cups each week used by customers who had dined in.

In an effort to reduce throwaway waste the cafe started using compostable plant-based packaging for all takeaways and stopped stocking straws.

It also decided to stop giving takeaway cups to people not taking away.

But the decision has not been welcomed by everyone.

The takeaway cup policy led to a heated confrontation last Saturday when a woman objected to being told she couldn't have a takeaway coffee cup if she stayed onsite.

The woman, who declined to be named, rang the Herald on Sunday from her car, after eventually leaving the cafe after a threat of trespass.

She said the policy was outrageous, sanctimonious and flawed, given the cafe gave away takeaway cups to those going offsite.

While she didn't feel she owed the cafe staff an explanation as to why she wanted a takeaway cup, it was because it didn't smudge her lipstick as much.

She had never been refused a takeaway cup at any other cafe, she said, and had even offered to pay more for one at Buoy.

A manager at the cafe said they believed the woman had been abusive towards a young staff member, and a threat of trespass was made only after she continued that behaviour after being asked to leave.

There were families and young children in the cafe at the time.

Owner Ginette Auld stood by her decision to cut down on waste and said everyone needed to do their bit to help the planet.

"We are doing all we can to have as little impact as possible and that includes composting all of our napkins and food waste and reducing the number of takeaway cups used."

Customers could still dine in and enjoy the sea view with a china cup in hand, or if they were genuinely leaving they could have a takeaway cup, or buy a keep cup.

"We don't make any money on the keep cups and it comes filled with coffee - we are really dedicated to doing what we can for the planet," Auld said.

Buoy used compostable coffee cups and plant-based lids from New Zealand company Innocent Packaging which cost the business between 20c and 30c a cup.

The company had also switched to compostable takeaway packaging, paper carrier bags and had streamlined its rubbish disposal so composting and recycling was easier.

"All our compost is collected from a company called We Compost and they take all of our waste, heat it for 72 hours and then sell to farmers."

Auld said the confrontation had been the only incident regarding the new policy.

"Everyone else has been understanding once we have explained what it is about."

Buoy is just one cafe among the groundswell toward more sustainable living.

Nicola Waldren, Restaurant Association general manager, said they had heard of a few other establishments taking the same approach in recent times.

She also said more and more members were using sustainable packaging - driven by customer demand.

"As a nation, we've become much more aware of the end life of our packaging and hospitality businesses understand that they need to do their part to reduce waste.

"Reusable is always going to be the best solution and we fully support those businesses that are making a real effort to educate and inform their customers to reduce their waste."