Got a link on that info? Graphite is pure, elemental carbon-I can't see how you can create it use a pile driver and wood. Wood is composed of cellulose and other organic compounds, which in turn are composed of a combination of carbon, hydrogen, nitrogen, oxygen, and various other elements in trace quantities. Compressing it and heating it under high pressures and very high temperatures enough to break all the bonds in the organic compounds, boil off the other elements, and melt down the remaining mass of carbon atoms. Carbon itself has a melting point of 3527 degrees Celsius, or 6381 degrees Fahrenheit. That's alot of heat. Wood would ignite first-meaning you would loose much of the carbon as carbon dioxide-and to avoid that, you would need to heat it in the complete ABSENCE of oxygen. Then you still need a way to avoid the leftover nitrogen, oxygen etc from reacting with the resulting mass of molten carbon as it cools, since the whole mass doesn't melt, but would actually decomposes as you heat it enough to break the bonds, THEN melt.
Edit: Being able to take magma and SLOWLY cool it (with water in iron pipes, or the like) might be able to net you more than obsidian. Also, I'm going to do some more research on volcanic rocks later, specifically the particularly porous rocks you can get like pumice.