Recycling with High Temp and Pressure

Many years ago,I read an article about scientist trying to emulate the conditions of th eEatrth's core.Hih pressure and temp.The injected variuos substances into the man made core,and what happened surprised them:Plastic quickly split up moleculars into natural gas,as did cellulose materials like sawdust. Why not try recycling materials in this way.The output could be feed stock to sustain the process.Of course,up-scaling would be a problem,but what about using volcanic vents? Just thinkin'.