Microbial Community Growth and Utilization of Carbon Constituents During Thermophilic Composting at Different Oxygen Levels

Abstract

Composting is characterized by dramatic changes in microbial community structure, to a high extent driven by changes in temperature and in the composition of the organic substrate. This study focuses on the interrelationships between decomposition of major classes in the organic material and dynamics in microbial populations during thermophilic composting of source-separated organic household waste. Experiments were performed in a 200-L laboratory reactor at 16, 2.5, and 1% O(2) in the compost atmosphere. Major classes of carbon constituents were analyzed by chemical methods, and the microbial biomass and community structure determined by fatty acid analyses with phospholipid fatty acids (PLFA) and total ester-linked fatty acids (EL) methods. At all three O(2) levels, the process was characterized by a rapid increase in microbial activity and biomass in the early thermophilic phase, although this period was delayed at the lower O(2) concentrations. Starch and fat were the main substrates utilized at all three O(2) levels during this period. The depletion of the starch fraction coincided with the beginning of a microbial biomass decrease, suggesting that starch is an important carbon substrate for the growth of thermophilic microorganisms during composting. Growth yields in the microbial community based on consumption of major carbon constituent classes in the high-activity period fell between 22 and 28%. Multivariate statistical analysis of changes in fatty acid composition revealed small, but statistically significant differences in the microbial community succession. At 16% O(2), 10 Me fatty acids from Actinomycetes and cyclopropyl fatty acids (from Gram-negative bacteria) became more important with time, whereas 18:1 omega 7t was characteristic at 2.5 and 1% O(2), indicating a more stressed bacterial community at the lower O(2) concentrations. Although adequate composting was achieved at O(2) levels as low as 2.5 and 1%, it is not recommended to compost at such low levels in large-scale systems, because the heterogeneous gas transport through the material in these systems might lead to anaerobic conditions and inefficient composting.

Closing the Global Energy and Nutrient Cycles through Application of Biogas Residue to Agricultural Land – Potential Benefits and Drawback

“…A lower level of carbon remaining in the residue is available for microbial degradation, compared to that in untreated waste and/or manure and/or slurry, and digested residues contain less total C as a result of conversion to CH 4 during the degradation process [1,47,50,53,69]. Moreover, the amount of lignin is higher in anaerobically digested residues than conventional slurry [72], similar to that in residues produced during thermophilic composting [73].…”

PLFA profiles of drinking water biofilters with different acetate and glucose loadings

“…Many PLFAs can provide taxonomic information or even information regarding physiological status of microbial species. Because different microbes have different phospholipid fatty acid (PLFA) composition and sometimes unique fatty acid markers, PLFA profiles have been applied to determine microbial community structure from various environments including soil, sediment, and compost, and indicate changes due to environmental disturbance such as temperature fluctuations, starvation or other stress conditions (Frostegård et al 1993;Guckert et al 1986;Hazeleger et al 1995;Kao-Kniffina and Balser 2007;Moll et al 1999;Steger et al 2005Steger et al , 2007Vestal and White 1989).…”

Microbial community succession and lignocellulose degradation during agricultural waste composting

“…Methods used to research the microbial community succession include traditional plate-count method (Hassen et al 2001;Boulter et al 2002), community level physiological profiles (CLPPs) (Laine et al 1997;Mondini and Insam 2003), phospholipid fatty acid (PLFA) analysis (Herrmann and Shann 1997;Klamer and Bå å th 1998;Steger et al 2005), molecular technologies (Dees and Ghiorse 2001;Green et al 2004;Franke-Whittle et al 2005) and quinone profile method (Tang et al 2004). It is well known that less than 10% of bacteria existing in ecosystems could be culturable when using plating culture techniques.…”