The bin? The food waste? The compost heap? Other recycling?

Landfill, up until recently, would have been the correct answer because teabags have traditionally been sealed with a very small amount of plastic - made from oil.

That is now changing, with many companies looking to find a more eco-friendly alternative.

But have some gone too far with their claims?

Clipper, the UK's sixth biggest tea brand, declares its bags "plastic free". But when you look at the small print it says the company uses a bio-plastic to seal the bags - made from plant material rather than oil.

When the BBC pointed out that some experts consider bio-plastic to still be a type of plastic, Clipper said it would update its website to make the information clearer.

It now says the material it uses, known as PLA (polylactic acid), is "not a plastic in the way we believe people most commonly think of plastics". Clipper boxes are still labelled "plastic-free".

Prof Mark Miodownik, a materials specialist at University College London, says most plastics are made from petrochemicals, but some - known as bio-plastics - are created using plant-based materials, such as corn or potato.

According to him, PLA - the sealant used by Clipper - is a plastic and "in this case it is still a single-use plastic".

Clipper says the material is "entirely natural, biodegradable and much more environmentally friendly".

A spokeswoman added: "Although a bio-polymer could technically be described as a bio-plastic, it is very different to the oil-based plastics which people are rightly concerned about."

What do other tea companies say?

Out of the UK's six biggest tea brands, the only other company that says its standard teabag is plastic free is Pukka - which says it uses a stitch of cotton instead of heat-sealing its bags.

Yorkshire Tea announced last month that it was hoping to release new renewable and biodegradable teabags by the end of November.

Its first attempt last year was "a bit of a disaster" - its own words, and the view of social media - with bags falling apart in people's cups.

It was keen to stress that the new bags, designed in conjunction with Sheffield University, would be "industrially compostable" - but not plastic free.

That means the bags can be put in the food or garden waste bin collected by your local council, but not home compost heaps, which don't get hot enough to break down the bags.

Like Clipper, Yorkshire Tea will also use PLA - changing from its current oil-based sealant to a PLA made from renewable corn starch.

In what appears to be a small jibe at other companies, it says plastic-free is "a term you have probably read elsewhere", but Yorkshire Tea "wouldn't feel quite right using it" as the bags contain a bio-plastic and "that's technically still a kind of plastic".

A spokesman from Twinings agreed that there had been "some debate" within the industry as to how best to describe the plant fibre PLA.

Teapigs, which says on its website that its "tea temples have NEVER contained plastic", confirmed to the BBC they contained PLA from corn starch.

Abel & Cole removed a page from its website about its "plastic-free tea bags" after being contacted by the BBC. A spokeswoman said the information was not accurate and it was an old blog post.

Helen Bird, from sustainability campaign group Wrap, said "false claims" were often made about "so-called plastic-free packaging, when in fact it was still plastic, albeit designed to be compostable".

A rundown of the biggest brands:

Twinings

Are standard teabags plastic free? No. The Twinings traditional teabag range contains a small amount of oil-based plastic. From January 2020, the range will become plant-based and will biodegrade in industrial composting. It says some of its "tag" teabags are plastic free - they are made from a plant-based paper material that is folded and stitched with cotton
How do you dispose of the teabag? The bin

PG Tips

Are standard tea bags plastic free? No. PG Tips announced in February 2018 that it was planning to switch to fully biodegradable, plant-based teabags. Its website currently states that it is moving towards "fully biodegradable teabags" and has already produced one billion
How do you dispose of the teabag? The bin

Yorkshire Tea

Are standard tea bags plastic free? No. Yorkshire Tea says it explored many options before deciding the best way to remove oil-based plastic quickly was to use the bio-plastic PLA to seal its bags, so that it can continue to make high volumes of tea with its existing set-up in Harrogate. It says in the future it "hopes to go completely plastic free"
How do you dispose of the tea bag? Currently the bin. The new bag will go in the household food bin collected by the council

Tetley

Are standard teabags plastic free? No. Tetley says its teabags contain a small amount of plastic material (0.04g per bag) so that they can be heat-sealed. It anticipates beginning to introduce fully biodegradable teabags for its core ranges in 2020. It says its goal is to "eliminate" plastic completely
How do you dispose of the tea bag? The bin

Pukka

Are standard tea bags plastic free? Yes. Its owner, Pukka Herbs, says it doesn't heat-seal the edges of teabags, instead it uses a simple stitch of organic cotton and what it calls "a unique folding process". It says this is "a more costly and complex process". It individually wraps each teabag and it expects all its blends to be in its new recyclable envelope by the end of 2019 (it started rolling it out in May 2018)
How do you dispose of the teabag? On a home compost - or if you don't have one, the household food bin collected by the council

Clipper

Are standard teabags plastic free? Clipper describes the teabag as plastic free, but the bags contain a "renewable, plant-based bio-polymer" - also known as a bio-plastic. It says it is exploring a number of green packaging initiatives, including improving recyclability and reducing packaging weight
How do you dispose of the teabag? The household food bin collected by the council

So is bio-plastic more eco-friendly than conventional plastic?

The term "bio-plastic" causes confusion, according to Wrap, but it simply means the plastic does not come from a fossil-based source.

The sustainability campaign group says it needs to be separated from the word "compostable", because bio-plastics and oil-based plastics can both be compostable - the key difference is bio-plastic comes from a renewable resource.

Under the UK Plastics Pact, which is being led by Wrap, the focus has been on urging companies to switch to compostable materials for teabags.

The pact says teabags containing plastic are problematic because they can contaminate compost when they are recycled with food waste - often consumers don't realise they have plastic in them.

Sian Sutherland, co-founder of environmental campaign group A Plastic Planet, said compostable bio-plastics were "the antithesis of plastic".

"They compost down in a matter of weeks after use and come from sustainable natural sources that are a million miles away from the petrochemical plants that have done such damage to our natural world," she said.

However, like oil-based plastics, if bio-plastics end up in the ocean they can present a danger to marine life because they "won't biodegrade in the ocean", said Prof Jenna Jambeck, an environmental engineer at the University of Georgia.

In a National Geographic study of bio-plastics, she said PLA "can be composted in an industrial facility, but if the town doesn't have one, then it's not any different" to conventional oil-based plastic.

Other environmental issues to consider, according to a 2015 United Nations report, surround where the bio-plastic is grown - including the amount of land it uses, and whether it diverts land away from food production or biodiversity.

If you are feeling a little confused about whether bio-plastic is a better option than oil-based ones, then you are not alone.

Prof Jambeck said bio-based plastics "have benefits" but it was "a big question based on many 'ifs'".