Shemekite, Fekadu (2015) Pilot Scale Windrow Composting of Coffee Husks and Flower Residues: Biochemical and Microbiological Determination of the Composts. PhD thesis, Addis Ababa University.
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Abstract
Two hundred forty thousand (240,000) tons of coffee waste and about 4000 tons of flower residue wastes are generated annually from the age-old coffee processing industries and the booming cut flower industries in Ethiopia, respectively. Most of these wastes are released to the environment without treatment, and their direct release pollutes the environment, mainly inhibiting plant growth. This necessitates the transformation of these wastes into beneficial products with a dual purpose of production of bio fertilizer and protection of the environment. To this end, a study was made to evaluate the process of composting of coffee husks and flower residues separately in order to determine their compost quality. Each material was arranged in to three different piles in a trapezoidal Windrow composting for 90 days and more, and monitored for their physico-chemical, microbiological and phyto-toxicological properties during the whole process. Coffee husk (CH) amended with cow dung plus house hold compost (CHCD: Pile 1) and with fruit/vegetable wastes plus house hold compost (CHFVW: Pile 2) were arranged and compared against the control (CH: Pile 3) without any amendment. As a result, the two amended treatments showed similar pattern of temperature profile with the first mesophilic stage (18-42oC) in the first 2 days followed by the thermophilic stage (45- 70oC) up to 45 days, and declined to the second mesophilic stage afterwards and remained so until the end of the experiment. In all cases, there was a steady decline of moisture content (MC %), reduction in total organic carbon (TOC%) and a rise in total Nitrogen (TN%) because of the loss of carbon in the form of CO2 thereby decreasing the C:N ratio of Pile 1, Pile 2, and Pile 3 to 11, 13, and 18, respectively. The highest bacterial count of 9.78logMPN g-1dw (Pile1) and 9.45logMPN g-1 dw (Pile 2) was seen at the start of the process; while the highest actinobacterial counts of 9.78logMPNdw (Pile 1 and Pile 2) and fungal counts of 9.78log MPN g-1 dw (Pile 1) and 9.45 MPN g-1 dw (Pile 3) were recorded at the end of the composting process, respectively. This change in number indicated a clear microbial succession along the process. The effect of the different microbial activities was reflected in the better maturation of Pile 1 with a Germination Index value >80% and C/N ratio of 11 at the end of composting compared to the control that required much more days for the material to become free from phytotoxicity. This transformation could be associated with higher volatile solid reduction (75% in Pile 1 and 65% in Pile 2), substantiating the importance of chemical parameters in coffee husk compost. The same feed stock was also composted with cow dung (Pile 1), with fruit/vegetable wastes (Pile 2) and coffee husk alone (Pile 3) again to study their microbial diversity and enzyme activities; and samples were collected on days 0, 32 and 90. Similar changes in TOC (%) and in TN(%) were found resulting in lower C/N ratios of 11 and 13 for Pile 1 and Pile 2, respectively due to changes in temperature profile, pH and water content of the mixture. This change which directed the succession of different microbial groups was accompanied by the release of compost relevant enzymes: hydrolases, phosphatases, peptidases and proteases in Pile 1 and Pile 2 at the start; and esterase at the end of the process. Furthermore, denaturing gradient gel electrophoresis (DGGE) analysis of coffee husk composting indicated distinctive community shifts during the composting process. The DGGE revealed that bacterial and fungal communities of samples from day 0 were clustered separately from communities of samples from day 32 and 90, indicating a change in the bacterial and fungal community composition. This result attributed that microbial communities at the start were responsible in the degradation of labile organic substrates while those communities at the end involved in the stabilization of the process. Young compost of Pile 1 and 2 were clustered separately from Pile 3 as the two cosubstrates introduced different and diverse microbial communities into the composting process. On the contrary, microbial community in the matured compost was grouped together showing the end compost were homogenous with well-defined microbial communities. Principal Component Analysis (PCA) of compost communities from day 0 and day 90 composts analyzed by COMPOCHIP microarray explained 62.5% of the variations. As a result, probes KO443 and 444 (Stenotrophomonas maltophilia), KO609, KO610 and KO614 (Brevundimonas/Caulobacter), KO500 (Derxia gummosa) KO612, 615, 616 and 617 (Flavobacterium/Flexibacter), KO541 (Pseudomonas putida), KO252 (Acinetobacter) and KO342 (Actinomyces sp.) were found to be more influential in discriminating the samples into different composting phases. Besides, Brevundimonas, Caulobacter, Chryseobacterium Sphingobacterium were dominant during the first mesophilic phase in Piles 1 and 2. These species have broader degradation activity of complex biopolymers. On the other hand, Flavobacteria/Flexibacter was detected significantly in all samples, suggesting their importance in the composting process. In general, microbial diversity and numbers were lower in the mature composts as indicated by DELTA 495a, Alpha proteobacteria and Low G+C, Xylella/Xanthomonas/Stenotrophomonas (KO241), Azotobacter beijerinckii (KO277) and the Actinomyces (KO342). Especially, the presence of Actinomycetes was an indicator of mature compost. In flower residue, the major feed stock (flower residue) was blended with cow dung (Pile 1), with activated EM (Effective Microorganisms) and molasses (Pile 2) and compared against the control (Pile 3) without any amendment for the same period of composting and the same composting system. Changes in NH4-N, NO3-N, NH4:NO3 ratio, available P and K and concentration of micronutrients (Cu, Zn, Fe, Mn) were included in the chemical analysis in addition to TOC%, TN% and C/N ratio to better understand the efficiency of chemical parameters in maturity indices. Consequently, the reduction in TOC (%) and the steady increase in TN(%) resulted in 10%, 16% and 24% of C/N ratios at the end of the process for Pile 1, Pile 2 and Pile 3, respectively. The use of inorganic N forms (NH4-N, NO3-N and NH4-N to NO3-N ratios) as indicators of maturity showed significant differences among the three piles. While NH4-N reduced below 400 mg/kg in all piles which was the maximum threshold level for matured compost, NO3-N showed an increasing trend, resulting in lower NH4-N to NO3- N ratio (0.12) of Pile 1, compared to Pile 2 and Pile 3 which could not reduce below 0.38 and 0.58, respectively. The analysis of available P and K also showed an increasing trend in all piles, but the concentration of available P (0.7-1%) at the end of the process was sufficient for soil nutrient supplementation. On the contrary, available K and all micronutrients were below the sufficiency level for plant production. In general, the effect of the different microbial activities was reflected in the better maturation of Pile 1, showing a low C/N ratio (10-11) and high GI% (80-85%) at the end of the composting; and significantly correlated with temperature, water content, pH over the 90 days of composting of both coffee husk and flower residue composts. Comparatively, Pile 2 and control of both the composting processes required more days for maturity in this respect. In conclusion, a polyphasic approach using physico-chemical and biological parameters including temperature, C/N ratio, GI%, NH4:NO3 ratio, enzyme assay together with molecular tools are very essential to evaluate maturity and stability of coffee husk and flower residue composts. Bulking agents that have much amendment potential like cow dung must be encouraged in large scale composting industries to tackle the current environmental challenges; and further studies on composting of various sources of solid organic wastes with a different composting system can offer greater insight on the quality, safety and age of composting. The nutritional and economic feasibility of these compost products must be addressed in order to fully realize their benefits and to understand the implication of the end products on plant production.
| Item Type: | Thesis (PhD) |
|---|---|
| Uncontrolled Keywords: | Coffee husk compost; COMPOCHIP microarray; Enzyme activity; Organic matter degradation; PCR-DGGE; Germination index |
| Subjects: | Q Science > QH Natural history > QH301 Biology Q Science > QK Botany Q Science > QR Microbiology |
| Divisions: | Africana |
| Depositing User: | Selom Ghislain |
| Date Deposited: | 12 Oct 2018 12:42 |
| Last Modified: | 12 Oct 2018 12:42 |
| URI: | http://thesisbank.jhia.ac.ke/id/eprint/6819 |
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