| 2. |
- Eiland, F, et al.
(author)
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Influence of initial C/N ratio on chemical and microbial composition during long term composting of straw
- 2001
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In: Microbial Ecology. - : Springer Science and Business Media LLC. - 1432-184X .- 0095-3628. ; 41:3, s. 272-280
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Journal article (peer-reviewed)abstract
- Shredded straw of Miscanthus was composted in 800-L boxes with different amounts of pig slurry added as nitrogen source. The impact of the different initial CIN ratios (11, 35, 47, 50, and 54) on the composting process and the end product was evaluated by examining chemical and microbiological parameters during 12 months of composting. Low initial C/N ratios caused a fast degradation of fibers during the first three months of composting (hemicellulose: 50-80%, cellulose: 40-60%), while high initial C/N ratios resulted in 10-20% degradation of both hemicellulose and cellulose. These differences were reflected in the microbial biomass and respiration, which initially were higher in low C/N treatments than in high C/N treatments. After 12 months of composting, this situation was reversed. Composts with high initial CIN ratios had high microbial biomass (15-20 mug ATP g(-1) OM) and respiration rates (200 mug CO, h(-1) g(-1) OM) compared to treatments with low initial C/N ratios (less than 10 mug ATP g(-1) OM and 25 mug CO2 h(-1) g(-1) OM). This could be explained by the microorganisms being nitrogen limited in the high C/N ratio treatments. In the low C/N ratio treatments, without nitrogen limitation, the high activity in the beginning decreased with time because of exhaustion of easily available carbon. Different nitrogen availability was also seen in the nitrification patterns, since nitrate was only measured in significant amounts in the treatments with initial C/N ratios of 11 and 35. The microbial community structure (measured as phospholipid fatty acid, PLFA, profile) was also affected by the initial C/N ratios, with lower fungal/bacterial ratios in the low compared to the high C/N treatments after 12 months of composting. However, in the low C/N treatments higher levels of PLFAs indicative of thermophilic gram-positive bacteria were found compared to the high C/N treatments. This was caused by the initial heating phase being longer in the low than in the high C/N treatments. The different fungal/bacterial ratios could also be explained by the initial heating phase, since a significant correlation between this ratio and heat generated during the initial composting phase was found.
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| 3. |
- Klamer, M, et al.
(author)
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Changes in chemical composition and microbial biomass during composting of straw and pig slurry
- 2000
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In: PROCEEDINGS OF THE INTERNATIONAL COMPOSTING SYMPOSIUM (ICS'99). ; 1-2, s. 322-334
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Conference paper (other academic/artistic)abstract
- Composting was performed in an 800-L box and a 500-L, reactor system. The material used was shredded straw of Miscanthus with pig slurry added as a nitrogen source. Chemical and microbial parameters were measured at five degree temperature intervals until the end of the heating phase and then with increasing intervals during the remaining experiment. In both systems, major losses of carbon occurred during and after the thermophilic phase as a result of degradation of hemicellulose, followed by degradation of cellulose. Total amounts of phospholipid fatty acid (totPLFA) and adenosine triphosphate (ATP) were used as indirect estimates of microbial biomass. These methods correlated well over time, when the limitations of the method for the determination of ATP were taken into account. Microbial biomass in the two systems showed similar values when measured by totPLFA. In contrast, microbial biomass measured by ATP content was higher in the box system than in the reactor system. In spite of the differences in chemical and physical properties in the two systems, the distribution of taxonomic groups of microorganisms, indicated by marker PLFAs, showed similar patterns in the two systems, emphasising that in composting systems temperature is the major parameter controlling the composition of the microbial community.
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