Or you may just drink the drink out of the glass like lots of people do anyway.

Proprietor Tristan Morthorpe says there's been no noticeable effect on trade since his ban on single-use straws. Some have objected but he thinks others are drawn to the place because of its policy.

It has had no impact on cost. The cafe saves a few dollars a week by not buying batches of plastic straws but, on the other hand, there is a cost to the steel substitutes of about $20 for a pack of eight, and they have to be cleaned with a pipe cleaner every time they're used and that's a time consuming chore.

"A few people get offended but most people are positive about it," he said. "They say, 'it's such a good idea'."

ACT Assembly member and Labor backbencher Suzanne Orr thinks it's such a good idea she wants the territory government to make public events such as festivals in the ACT plastic free and to be much more active in reducing the use of plastics that can't be reused or recycled.

She spent a "plastic free month", which meant taking her own coffee cup with her or just staying put in the cafe and drinking out of its mugs at tables.

Her point is that if you keep your own cup, you save 365 plastic cups a year.

"It's not been a hard change," she said. She either takes her own lunch or eats it where she buys it - no take-away in plastic. "I try to identify places that use cardboard instead and I bring my own food from home."

But the calculation isn't as simple as you might think, according to one of the country's experts on the economics of materials.

Dr Trevor Thornton who lectures at Deakin University in Melbourne said it was a complex issue.

Plastic stickers on apples, for example, might help supermarkets track them and so cut transport costs - and transport generates global-warming carbon dioxide.

A good answer might be a Melbourne company's idea of replacing the plastic labels with ones made of a bio-degradable material. Another company is developing ways of lasering brand markers on to oranges and avocados.

Steel for straws has a carbon footprint - it is manufactured - so exactly how beneficial it is to make the switch from plastic to steel depends on how many times the steel straw is re-used.

And plastic wrapping prevents the bruising or rotting of fruit.

You might, for example, go into the supermarket and see cucumbers wrapped in plastic and think, "why on earth have they done that?" But plastic keeps food fresh for longer and so diminishes waste. Cut back on the plastic excessively and food then rots.

The plastics and food industries, under intense pressure to cut the amount of plastic shoppers see, have been researching new materials and methods. There is now, for example, "modified atmosphere packaging", which inserts chemicals into bags to slow rotting or allow a little more air in.

As the American Chemicals Council puts it on its pro-plastics website: "special types of plastic bags enable 'modified atmosphere packaging' that does just that: regulate levels of various molecules in the packaging to keep your arugula, sliced carrots, and apple slices from going bad real quickly".

"For example, [modified atmosphere packaging] can double shelf life of mixed greens from four days or less to up to eight days."

Dr Thornton believes more pressure should be put on shops to sell smaller portions. He cites packages of corns on the cob that come in threes. "We should be saying, 'if I just want one corn-cob, why are they selling me three'?"

This tendency to bulk package encourages us to over-purchase and throw away the excess, he believes.

Why not, instead, sell more vegetables loose so people can choose the quantity.

His advice is only buy what you need. The public should be much better educated in how to store food, he said. Better storage means less waste.

Is there a danger of "virtue signalling" by the abstainers from plastic - of people doing something not because it offers so much real benefit but because it shows them in a good light?

Dr Thornton thinks there is, but he would rather criticise people who are doing nothing about a problem than those who are doing a little, albeit for mixed motives.

He sees the complexity but says that doesn't mean we shouldn't cut the wasteful use of plastic. It is a pollutant that clogs waterways (and birds' stomachs). Avoidance of waste is his mantra.

He himself carries around a steel straw and a brush to clean it out if he has, for example, a smoothie.

Plastic has its uses - but waste is always waste, is the gist of his view. He thinks a lot more could be done to get attitudes to change. It's not a short-term thing, he thinks. Getting seat-belts accepted, for example, required long-term campaigning.

Maybe there is too much plastic in fridges and rivers and parks. But the experts say it still has its uses - and its limitations. Obituaries are premature.