How to get rid of domestic and urban rubbish? Recycling is troublesome, incineration unpopular, and composting impeded by the presence of plastic and metal. Landfill merely entombs the trash archivally for future archaeologists. One answer might be to feed the stuff to pet goats; they eat anything, and would generate useful metabolic heat from its digestion. Unlike a passive compost heap or landfill, an animal gut is ceaselessly churning. Some animals swallow stones or grit to aid their digestion; these must help the process mechanically or chemically. In this connection, Daedalus recalls that halocarbons can be decomposed by ball-milling them with lime. Mechanical impact and abrasion actually break up the molecules and encourage their reaction.

So Daedalus is designing a mechanically agitated composter for all our rubbish. Its steady churning and pounding, shearing the molecules at the point of impact whenever two chunks of rubbish come together, will degrade its contents at an unprecedented rate. Even plastics will be rapidly oxidized to products edible by the resident bacteria. Chemical, mechanical, thermal and biological decomposition will all proceed in parallel. Too violent an agitation might squash the bacteria faster than they could multiply, but slower rates should be entirely effective. Adding domestic sewage to the mix would solve another disposal problem at the same time.

A large-scale rubbish composter would be a long inclined cylinder rotating on its axis. Rubbish added continuously at the elevated end would work its way slowly down; the cans and bottles in it would act as grinders for the organics. Its inlet zone would be kept anaerobic, to generate useful methane. Downstream, injected air would switch it to aerobic decomposition. Toxins and pollutants would be totally mineralized by this steady mechano-chemical battering. Only rust, glass and ceramic grit would emerge at the far end.

But Daedalus wants to abolish rubbish collection as well. So he plans a simpler domestic composting dustbin, to degrade the rubbish and sewage of one household. It will grind away outside the house, but will be plumbed into the heating system to contribute useful warmth to the domestic interior.

 The Further Inventions of Daedalus (Oxford University Press), 148 past Daedalus columns expanded and illustrated, is now on sale. Special Nature offer:m.curtis@nature.com