Microbial succession during composting of source-separated urban organic household waste under different initial temperature conditions

The effects of initial temperature regime on microbial community succession during controlled composting of organic household waste in a laboratory reactor was determined by analysis of phospholipid fatty acids (PLFAs). Spontaneous self-heating of the substrate led to substantial microbial biomass increase (maximum PLFA concentration of 2000 rimol g(-1) d.w.) and high CO2 production in the thermophilic phase (regulated at 55 degreesC). In contrast, when the initial period of temperature increase was shortened by external heating, there was a negligible increase in biomass and only a small increase in CO2 production. Thus, attempts to speed up the process initially by external heating are not advisable. The increase in PLFA concentration under self-heating conditions occurred mainly in iso- and anteiso-branched fatty acids (more than 100-fold increase, their maximum corresponding roughly to 10(11) bacterial cells g(-1) d.w.) from different types of thermophilic bacteria. One PLFA typical of actinomycetes (10Mc18:0) had a low initial concentration, but started to increase during the thermophilic phase. The abundance of polyunsaturated PLFAs generally decreased during composting, indicating no growth of eukaryotes.