Yes, many firms sell such additives to help you with your problem.
In addition, I sell a wonderful tool called a "Poop or Soup" Waste Sensor, it senses the voltage difference between spetic waste and other waste, this way you know if someone's been adding "unauthorized" substances to your waste stream (such as excess Charmin, dead goldfish, etc.) and take measures to tell 'em to stop reducing the efficiency of your "honey hole." Uses battery power; very simple & safe. $22.50 incl'shipping. 888 851 9891. E-mail email@example.com.
Also, no home or outthouse is complete without a tankless hot water heater. Even if you don't have a sink in your one-holer, you'll appreciate the comfort and peace of mind you'll get knowing that your moon-ddor mansion is equipped with a top-of-the-line appliance. Happy New Year, Brian Woods.