I wish Supercritical Water Oxidation had worked out.

But it requires ceramics that are resistant to heat, pressure, and chemical erosion, which turns out to be the usual 'pick two' situation.

I had heard someone was working on composite ceramics to deal with this (heat and pressure resistant bulk, enameled with heat and chemical resistant coatings) but have heard nothing since.

So far they only seem to be price competitive in hazardous waste situations.