What's the environmental impact of a sky lantern?

They may be beautiful as they drift off into the night, but the party could soon be over for sky lanterns

Leo Hickman
guardian.co.uk, Friday 31 July 2009 16.16 BST
I am getting married next year and when going to buy so-called 100% biodegradable "sky lanterns" I have been disgusted to find that they contain metal wires which obviously take years to degrade. Beautiful and fairly cheap they may be, but I for one will not allow even the possibility of harming animals to come from my wedding, and I strongly believe that others will feel the same – if they have the knowledge.
Saffron Light, by email
Less of a question, more of a statement, but I take your point, Saffron. I, too, have wondered about what happens to these sky lanterns once their brief blaze of glory begins to fade and they fall back to the ground. They are, indeed, a fairly splendid sight as they drift away into the night sky. But, as with the release of helium-filled balloons at a charity event, they must fall back to earth somewhere resulting in – at the very least – an eyesore for someone to clean up.
The claim made by some of the sky lantern retailers about their products being "biodegradable" is certainly worth exploring. If these paper lanterns did, indeed, rot away within a matter of days, then they might possibly claim to be environmentally benign. But, as you point out, they contain a thin metal wire support.
I rang one of the UK's leading online sky lantern retailers and asked its sales representative to put some flesh on this "biodegradable" claim. He said that the paper biodegrades within "six to eight weeks", and claimed that the "flourished wire" take nine months, on average, to break down.
How did he know this? "The manufacturers did some tests. But the wire is only eight inches long and accounts for just 1% of the lantern's mass."
Who are the manufacturers? "I don't know. They used to be in Thailand, but I think we get them from Japan now."
This answer intrigued me, because on the company's website it says that all its products are "sourced ethically" and that it "operates a fair trade agreement with our manufacturers". This led me to assume that it must have a very close relationship with its suppliers, so why the confusion about where the sky lanterns are sourced? I asked what this "fair trade" claim meant.
"Some of our competitors pay under the minimum wage in these countries. We ensure that we pay a fair wage." But such statements are next to meaningless without any form of proof or certification.
I came away from the conversation with far more concerns and questions than I entered it. For example, why should the claim that the wire takes nine months to break down be presented as a means of reassurance? Wire lying on the ground for nine months is surely a considerable hazard, depending on where it lands, for farm animals or children. And can metal wire really break down so quickly? I'm always digging up old bits of wire fencing in my garden (formerly a field) which must have been there for years, if not decades.
Back in April, a farmer who runs a wedding venue in the Staffordshire Moorlands banned the use of sky lanterns on his land due to similar concerns (thanks to the Guardian user Yamaman for a link that led me to the story). Mick Heath of Heaton House farm told the North Staffordshire and South Cheshire Sentinel: "Brides and grooms ask if they can let them off, but they do not understand that the wire in them takes ages to break down. He added:
If it gets wrapped up in hay bales it would be like swallowing razor blades for farm animals and if it falls into grassland it will kill wildlife. These lanterns are advertised very heavily in bridal magazines. Brides and grooms can see the attraction, but not the danger … One of our cows bled to death internally after eating shards of a discarded drink can. I want to do all I can to avoid any animal suffering like that again.
Margaret Heath, Mr Heath's wife, expressed an additional concern: "There is also the danger that if they come down alight they could start a fire on the moorlands, a fire in a tinder-dry cornfield or even someone's house. We really do not know where they are going to come down."
Sky lanterns have long been a tradition in east Asia. You only have to look at this footage of a sky lantern festival in Chiang Mai in Thailand to see how popular they are – and how potentially dangerous they can be when lit en mass.
But the party could be coming to an end. Last week, the Vietnamese prime minister, Nguyen Tan Dung, announced that a sky lantern ban would take effect from mid-September, says a report by VOV News:
According to the Ministry of Agriculture and Rural Development, almost 20 forest fires have been caused by burning sky lanterns since the beginning of the year. In Hanoi alone, there have been eight fires in workshops, electrical stations and houses caused by sky lanterns. Sky lanterns that fell on power stations in the capital were also blamed for causing power blackouts, during Lunar New Year's Eve earlier this year.
In Thailand, too, some local authorities are now starting to ban the sale of sky lanterns ahead of major festivals.
And closer to home, three German states have now banned the sale of the lanterns following the death of a 10-year-old boy in a house fire caused by a sky lantern in North Rhine-Westphalia. Even the UK coastguard is now starting to express concern about the site of these lanterns drifting out to see and mimicking the sight of distress flares.
I doubt it will be too long before a ban is considered here in the UK.