However it is thermodynamically a possible process and could be explored. This is a destructive process leading to loss of the abrading parts. Now the trend being conservation of existing resources,it becomes difficult to envisage such energy source. However it is thermodynamically a possible process and could be explored. Of course it's a destructive process.
Most thermal processes require consumption of some material.
The question is whether the 'cost' of the material versus the process efficiency make tribothermal generaltion an economical process. The opportunity lies in the relatively simple reclamation of the material and also the higher enegy capacity of solids. He has a point about consumption, as it's not as easy to replace an abrading solid as it is to pipe in fresh fuel. As for a practical friction energy source, you would a pre-existing and plentiful input like flowing water. One elegant application of all this is regenerative braking, which is used in some of the prototype solar cars to reclaim some of the energy you waste slowing down.