My reply will not address the storage of dry matter, but the secondary treatment of waste from both UDD and other waterless toilets.
I'm not giving myself out as an expert, and we learn by trial and error as we are the only company in South Africa currently subscribing to the composting process of human waste.
We have been composting the waste from our "sawdust- based" waterless toilets for the past 24 months with great results. We maintain temperatures of between 45 - 55 C during the first 8 days of the composting process which effectively kills pathogens and latent ova. The temperatures can be maintained for longer - depending on the other materials you use in the process (C/N) and the volume of liquid (urine, grey water) you use in the process.
Because we do these processes on a decentralised basis, and specifically in informal settlements we have now engaged with a SA University to assist with a study where we can combine the composting with a biogas process. Biogas digesters optimal performance takes place at approx 32-34C, and the temperature isn't high enough to neutralise pathogens.
I'm not going to elaborate on the topic, but we are interested in knowing if other companies and/or universities are use composting and/or biogas as a field of study (we are familiar with the SOIL study in Haiti - Berkeley Univ), and other research material on pathogens and their behaviour under different temperatures.
A collaborative study may provide different outcomes, and possible solutions to northern and southern hemisphere challenges.