I would have to advise against even trying incineration with a lens, even the lens that has a linear focal point (which I have) will prove to be much work and time wasted for little gain. You need the type of heat a furnace or oven puts off to get proper and complete incineration. The heat from a lens will be a surface heat and you will have little control over temperature.
I had a picture up of mine from when I was depopulating chips from boards and I have to say it works quite well, plus your outside so any fumes can be blown away and being outside in the sun is not a bad thing.
I had a picture up of mine from when I was depopulating chips from boards and I have to say it works quite well, plus your outside so any fumes can be blown away and being outside in the sun is not a bad thing.