Renewable? Unless you can just pluck it out of the air, then it may be renewable. I am not sure how difficult it is to manufacture a steel knife, but looking at the simplified diagram of how to make this "hardened" wood, it looks like an energy intensive process. When people try to make a natural resource to do something that it can't do or not efficient in doing naturally, we are basically creating significant inefficiencies.
Truth to be told, there is nothing that man can do to try and self sustain. Everything that we create with the misconception of "sustainable" may sound good on paper, but is nowhere near being able to sustain us. Look at solar panels, they are very energy intensive to create and to maintain in a solar farm. Sure we can get power out of them, but its like using a whole bunch of power to produce solar panels and maintain the solar farms, so whatever power it produces is mostly to pay back the cost. Not to mention, solar panels if I am not mistaken are nowhere near 30% efficient in converting sunlight to power. The last I heard was sub 20% conversion rate.