The difficulty of dealing with the human waste would actually be made more difficult at this time of year. Certain human waste is a lot more toxic and difficult to deal with than others depending on the individual. Consider for example the output from a Vegan compared to someone who has consumed a Meal Refusing to Exit (MRE) combined with the consumption of industrially farmed turkey, Brussels sprouts, Guinness and Christmas pudding.

Look what happened to Mr Creosote for example.

Sub zero temperatures may make it difficult to bury waste in the back garden so I reckon the next best thing would be to implement the advice from this old 1970s Protect and Survive video.

http://www.youtube.com/watch?v=IJGEgTfecHc