If you have strong convictions on avoiding "chemicals", you could always get a few packs of bakers yeast, boil them in a cup or two of water, and add it in. The dead yeast cells will be the Soylent Green for the living yeast. This is what most of the yeast energizers you buy consist of, plus some nitrogen.
However, unless you add someting to help the yeast out, I'm afraid you may have a tough time getting it to ferment. That sounds like a OG of 1.100 +.