Been doing the composting thing lately and really enjoying the results in the garden so I started looking into ways to expand this.
There are two links from Washington State and UMN that say this is a bad idea, as the potential health risks outweigh the possible benefits. Another link says that its pretty much its like human waste: you gotta leave it alone for a year. If you aerate it properly and have a thriving compost bacteria/worm combo, you can speed that up as much as 6 months. Without testing facilities, I'd still wait an absolute minimum of 9 months.
Regardless, the biggest find here looks to be sawdust: you can actually make it very cheaply and cats apparently love it. If its not quite covering up the odors, you can just add the stuff all the commercial litter uses: baking soda.