91É«ÇéƬ

Is it more sustainable to flush a tissue or put it in the bin?

Pat French
Telford, Shropshire, UK

Thank you so much for asking this question. It has puzzled me too.

First of all, is your tissue totally biodegradable? If so, it could go into the compost, as long at it hasn’t been used to . If you flush a tissue, knowing its fate will take research because there are many ways that different countries, states and municipalities deal with what you flush. Likewise, if you bin it, what does your local disposal facility do with general waste? Is it sent to landfill or is it burned?

I have been wondering whether I should go back to cloth hankies, but I don’t like the idea. And what about all the energy it takes to wash them at a hot enough temperature to be hygienic?

You have asked a question that really isn’t easy to answer without answering a lot more questions.

Lisa Gulland
Bagnères de Bigorre, France

The most sustainable thing to do with used tissues is surely to compost them. We have a compost bucket (with a lid) in the kitchen. Tissues, paper kitchen towels, vegetable scraps, egg shells and so on are collected in there before being taken to the compost heap in the garden. No need to worry about germs any more than with egg shells (which we don’t rinse): it is just a bin that gets emptied.

Nigel Horan
Halifax, West Yorkshire, UK

Ideally, a flushed tissue will disintegrate in the sewer and be removed in sludge, through settlement at a sewage works. The sludge will then be anaerobically digested and the tissue will return to land in the digestate. However, in the worst cases, the tissue is deposited directly into the watercourse, polluting the riverbed. This can occur when the sewer network becomes deluged by rainwater. Most likely, however, is that the tissue will be removed by the screens at the treatment plant and then disposed of to landfill.

Putting the tissue in the correct bin offers the most sustainable solution. Local authorities have different policies on recycling and, in some cases, to be converted into new products, whereas for others, the best route is the food waste bin, where they will be sent for anaerobic digestion with energy recovery.

David Muir
Edinburgh, UK

Toilet paper comes in various types. Some is rough and not very absorbent; some is soft and smooth, made for the more discerning posterior. But they should all have one thing in common: they must break down easily in sewage systems and septic tanks.

Paper hankies for nose-blowing and the like have to be stronger than toilet tissue. This means it is harder for them to decompose in sewage systems. This potentially adds to the problem of fatbergs, the solid blockages formed in sewage systems from flushed non-biodegradable solids, such as fat and wet wipes. Don’t help build fatbergs: bin your tissues.

Garry Trethewey
Arkaroola, South Australia

Good question. It all depends.

If you live in a place that has a plentiful water supply, and if the water from your sewerage system ends up watering a veggie garden, then flushing is sustainable. But if you live in a place like I do that has limited water, then flushing a single tissue is a big waste.

On the other hand, if you put tissues in the bin, where do they go from there? Perhaps to a well- managed municipal tip that will eventually be covered with soil and planted with trees, or to a well-run incinerator that runs a boiler to produce hot water. Or is the waste dumped somewhere and half-burned in a smokey fire? Or does it pollute the local creek?

Robert Law
Hong Kong, China

It depends on what sort of sustainability you mean. In many older cities in China, although there are flushing toilets, the outlet pipes are often rather narrow. People are advised never to flush paper tissues down the toilets to avoid blockage of the outlet pipes.

To answer this question – or ask a new one – email lastword@newscientist.com.

Questions should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. We reserve the right to edit items for clarity and style. Please include a postal address, daytime telephone number and email address.

91É«ÇéƬ retains total editorial control over the published content and reserves all rights to reuse question and answer material that has been submitted by readers in any medium or in any format.

Terms and conditions apply.

Ìý