Composting of Human Excreta with Howard-Higgins Composting Method

Abstract: Problems as a result of inadequate sanitation are the root to spreading of many diseases and the loss of several millions of lives every year. Therefore a Norwegian organization, Sustainable Sanitation Design, is trying out methods for having human feces sanitized in a sustainable way. In this trial, the safety and efficiency of composting human feces with a special composting method, called the Howard-Higgins method were investigated. The method claims to sanitize source separated feces in 90 days and to test that statement six compost containers were set up. To control that the composting process reached the heat necessary for sanitization the temperature was controlled frequently. Volatile solids, pH and the dry substance fraction were also controlled to measure Howard-Higgins method’s efficiency. By measuring fecal indicators Enterococcus feacalis initially and in the very end of the process, the statement of sanitization was controlled.  The results from the measuring of fecal indicators showed a very varied result. Some of the compost nearly reached the limits for pathogens set up by the WHO. The most successful compost ended up with 3.9 LOG10 reduction, which only 0.1 LOG10 below WHO’s definition of sanitization for excreta that is to be used as fertilizer. The least successful compost had only a 1.6 LOG10 reduction. None of the compost became warm enough to sanitize pathogens. The method is because of its complicity and uncertainty not recommended to be used by Sustainable Sanitation Design to sanitize human feces.