I am using a Compact ComposTumbler with some success. However, my temperature rarely gets above 120F. Most of my biomass is grass clippings, which I usually allow to dry and then use as my brown material. My green material comes from kitchen scraps, weeds, some green lawn clippings, and horse manure. Even with the horse manure, which gets the temperature to rise quickly, my temperatures seem to max out at 120.
At first I tried following the carbon/nitrogen recipes that came with ComposTumbler. This year I have been following some instructions I found on old postings of this forum. I put my brown material in (filling the tumbler 3/4 full or more since grass tends to take up a lot of room at first and then to reduce in volume very quickly). Then I gradually add my greens over the course of a week. Once my temperature exceeds 100F, I stop adding greens and give the tumbler only one or two turns each day as I monitor the temp. The forum post recommended not turning too vigorously until temperatures neared 140F, but my temps never get that high.
Is dried grass a sufficient brown material? Is there something else that I should be adding to get my temps up?