Compost toilet in buckets ?

I think I read about a composting toilet system that was all contained in 2O litre buckets with lids with no open compost heap, am I right or have I remembered it wrong.

I've just been offered a pile of free used cooking oil buckets .

If you don't occasionally empty the 20 Liter buckets into a larger vessel you'll need a lot of buckets. In our household it take four or five days to fill a bucket. Temperature is a variable but typically you want to let the waste rest for at least a year to allow for pathogens to be killed off. I also don't think a 20 liter bucket has enough material to generate enough heat to kill off the pathogens.    

You need to read the Humanure Handbook by Joseph Jenkins. There is a free pdf version available. It uses a bucket system as you suggest, and having used it I can say confidently that it is a pleasure to use PROVIDED you follow the instructions. Don't try to modify the plans until you have spent at least a couple of months using it as directed. You will be amazed at how clean and pleasant it is to use, how hot the compost gets, and the incredibly quality of the end compost.

People go wrong when they try to adapt it to eg divert urine away. It's just not designed to work that way. Urine feeds the hot compost and makes sure it all gets hot and sterile really quickly.

Aaron Yarbrough wrote:If you don't occasionally empty the 20 Liter buckets into a larger vessel you'll need a lot of buckets. In our household it take four or five days to fill a bucket.

This, of course, depends largely on the number of contributors in your household. Solo, I properly fill (adding browns, greens & liquids) a 5gal 'container' in approx. 3-4 weeks - sometimes extending the fill to 5 weeks.
 

Aaron Yarbrough wrote:Temperature is a variable but typically you want to let the waste rest for at least a year to allow for pathogens to be killed off.

Temperature is what kills pathogens. Knowing this, I built a small, insulated compost shack, specifically for humanure composting.  The entire south facing wall is a thermo-glass (double pane) window. I regularly see compost temps well into the 90's during the 25f degree winters, and occasionally exceed 120f during summers. Still, I leave the containers throughout the year. I carefully and continuously monitor temperatures throughout the year.    

Aaron Yarbrough wrote: I also don't think a 20 liter bucket has enough material to generate enough heat to kill off the pathogens.

Joseph Jenkins (4th ed. Humanure Handbook) made mention of not being completely successful employing 'smaller' containers, but he also, admittedly, just assumed it because of smaller samples. My personal reasoning and experience clearly tells me that it is not the volume of ingredients that matters... success is dependent on proper ingredients, proper mixtures, moisture, ventilation and temperature.  Works for me.  

Richard Churchill wrote:I think I read about a composting toilet system that was all contained in 2O litre buckets with lids with no open compost heap, am I right or have I remembered it wrong.

Richard, I can think of 2 systems that are at least close to what you describe, and illustrate a second proven method for killing pathogens besides heat.  The first is called "vernmenting" and is completed in a 5 gallon bucket.  See a description here.  The second is a design by Anna Edey, documented in her book "Green Light at the End of the Tunnel."  In essence she flips the bucket upside down in a closed vermicomposting bin.