Difficult to recycle products made of polystyrene and plastic were banned for both dine-in and takeaway customers under a bill passed in October, with offenders facing fines of up to 100,000 Hong Kong dollars ($12,750).

Plastics are the finance hub's second-largest source of solid waste, averaging 2,331 tonnes per day in 2021 -- equivalent to nearly 70 adult humpback whales.

"Within the (six-month) adaptation period, officers of the Environmental Protection Department will not enforce the law against non-complying businesses," Tse Chin-wan, Hong Kong's environment secretary, said in a blog post on Sunday.

Lunchtime on Monday was business as usual in the commercial district of Wan Chai, where stalls made sold meals in polystyrene containers.

Wilson Tam, an office clerk, said he supported the policy but stopped short of agreeing to bring his own lunchbox.

"It's quite a trouble to wash the box at work," he told AFP.

Home appliance exhibitor Michael Lin said he did not mind paying the price for eco-friendly utensils of good quality.

"Sometimes paper tablewares are too thin -- that's more of a problem," Lin said.

But the cost of replacing plastic cutlery with eco-friendly materials such as wood, bamboo or paper could jump by 30 percent for businesses, while they struggle to secure a consistent supply of alternative products, industry experts said.

The six-month breathing period "is not sufficient for us", said Hailey Chan, who manages a restaurant focused on eco-friendly products.

"We ordered (tens of thousands of) cups with customised printing... it's a bit difficult to use up all of them in half a year," she said.

Monday's ban will also hit hotels, which are no longer allowed to provide single-use plastic toothbrushes, combs or bottled water.

Jack Cheung, director of CTS HK Metropark Hotels Management, told AFP the group's five restaurants had switched to paper cutlery starting Monday.

Bathroom items in about 2,000 rooms across their seven hotels would need time to change, he said, adding it would raise costs by 10 to 20 percent.

"But we believe it's worthwhile for the environment and our future generations."