How to get rid of our mounting piles of organic waste? Oxidation is the obvious reaction for the job; but burning in air generates highly unpopular smoke. Water-based oxidation would be far better. Sadly, it either needs ferocious reagents, such as fuming nitric acid, or extremely high temperatures and pressures, as in supercritical aqueous oxidation. Daedalus is looking for another way.

He notes that sonolysis, subjecting a reaction to intense high-frequency sound, can speed it up hundreds of times. The violent pressure-swings of the sound cause the liquid to cavitate, that is, to form tiny transient bubbles of vacuum. Their collapse produces vast temperatures and pressures; these create energetic free radicals which speed the reaction.

Sonolysis can certainly accelerate the oxidation of organics in solution. But Daedalus wants to destroy solids as well — old newspapers, plastic rubbish, food residues, discarded clothing, and the rest of our organic detritus. He points out that bubbles form easily on solid surfaces, especially irregular ones. Hence the ‘boiling stones’ used by chemists to aid smooth boiling, and the cavitation suffered by ships' propellers. A propeller can stir the water violently enough to cause cavitation; the bubbles form right on the metal where they can do the most damage.

In principle, therefore, a suspension of solid waste should oxidize if stirred with sufficient vigour — provided the waste itself was used as the stirrer. Now an object suspended in a conducting liquid threaded by a magnetic field experiences a force when a current is passed through the liquid: a sort of differential motor effect. So Daedalus will oxygenate his rubbish suspension, put it in a strong magnetic field, and pass high-frequency a.c. through it. The violent vibration of the solids against the surrounding water will cause cavitation at their interface. Bubbles will form and collapse on the solid surfaces, exactly where they are needed; the suspended waste will erode and oxidize rapidly.

Daedalus's waste-cavitation plant will suspend its shredded waste in air-saturated sea water, the cheapest oxidizing conducting solvent. The rubbish will simply fizz away to gas and ash, and the sterile effluent will be returned to the sea. The process should work on domestic sewage, too. Those lazy seaside towns that just pump the stuff out to sea will not even have to change their outfall pipe.