Simulation of accumulated matter from human feces in the sawdust matrix of the composting toilet

A bio-kinetic model for aerobic biodegradation of human feces was applied to the practical operation of the composting toilet. The first aim of this study was to describe nitrogen transformation in the toilet as well as organic carbon. Second aim was to obtain the kinetic parameters for better prediction of accumulated matter for a long time of the practical operation. Six simple fractions of fecal carbon (slowly hydrolyzable matter, easily hydrolyzable matter, readily biodegradable matter, biologically inert type of matter etc.) were prepared in the model. Nitrogen factors were incorporated to each factor of fecal carbon. Modification of only one kinetic parameter for hydrolysis of slowly hydrolyzable carbon was required to obtain the best fitting curve of accumulation in the toilet. Model prediction for one-year operation of the toilet showed that temporal accumulation of biodegradable organic matter was significant in the first stage whereas main accumulation would be biologically inert type of organic matter at the end of the operation.