Organic waste can be converted to energy by making use of a process known as anaerobic digestion, which involves the breaking down of biodegradable materials by microorganisms in the absence of oxygen. They produce a rich quantity of methane which can be used for cooking, transportation and generation of electricity.
The conversion process, which could be either in mesophilic or thermophilic conditions depending on temperature, contains some certain predominant microbiomes. Therefore, it is important to understand the major phylotypes of Bacteria and Archaea in view of increasing the efficiency of the conversion process.
It is also important to note that different feeds and environmental factors should be considered as major influences of composition and physicochemical properties of the slurry, and their effects during the anaerobic digestion process shouldn’t be undermined.
A group of researchers led by Fabrizio Cappa from Università Cattolica del Sacro Cuore in Italy investigated the effects of different animal feeds at two separate regions and cheese production areas of Parmigiano Reggiano and Grana Padano on the microbiome of six-full scale biogas plants by using indexed Illumina sequencing to identify key phylotypes of Bacteria and Archaea, and a quantitative polymerase chain reaction to determine 16S rRNA gene of total bacteria, archaea, Clostridiales and methanogens populations. The work was published in the journal Bioresource Technology.
The authors observed the effects of feedstock on the production efficiency of methane during the anaerobic digestion process. In Grana Padano biogas plants, the feedstock containing cattle slurry manure, energy crops and agro-industrial by-products had the highest methane concentration with minute accumulation of volatile fatty acids and ammonium concentration.
Biogas plants of the two regions with feedstock containing only cattle slurry manure had the lowest value of specific methane production and volatile solid degradation efficiency. Coupled with the feedstock composition, they also indicated the effects of the hydraulic retention time, organic loading rate and mixing ratio of the substrate as they played a major role in degradation efficiency of volatile solid and specific methane production yield.
Results from the Illumina sequencing analysis while regarding bacterial communities showed that the geographical area, operating temperature and feedstock played a major role in determining of the plant microbiomes while time had a negligible effect. The most predominant phylotypes were discovered to be: Firmicutes, Bacteroidetes and Proteobacteria. Thermotogae phylum found only in the thermophilic biogas plant was clearly related to the hydraulic retention time.
When observing the 16S rRNA gene population of bacteria and Clostridiales, results from the real-time polymerase chain reaction indicated a slight difference between both biogas plants of the two separate regions and as a result, the effect of the geographical location area on bacterial diversity has nothing to do with the order of Clostridiales.
For that of the archaeal community, Illumina sequencing analysis indicated most predominant phylotypes to be Methanosarcina and Methanosaeta in mesophilic biogas plants while Methanoculleus was predominant in thermophilic biogas plant. The Methanosarcina was related to ammonium concentration in the biogas plant.
The mean 16S rRNA gene populations of archaea and methanogens indicated major difference in the archaeal population unlike that of the methanogens where no major difference was found.
This study provided important data on the effects of the geographical location area, feedstock and temperature on anaerobic digestion of organic waste in relation to microbiomes involved in the process.
Fontana, A.1, Patrone, V.1, Puglisi, E.1, Morelli, L.1, Bassi, D.2, Garuti, M.3, Rossi, L.3, Cappa, F.1,2 Effects of Geographic Area, Feedstock, Temperature and Operating Time on Microbial Communities Of Six Full-Scale Biogas Plants, Bioresource Technology 218 (2016) 980–990.Show Affiliations
- Istituto di Microbiologia, Università Cattolica del Sacro Cuore, Via Emilia Parmense, 84, 29122 Piacenza, Italy
- Centro Ricerche Biotecnologiche, Università Cattolica del Sacro Cuore, Via Milano, 24, 26100 Cremona, Italy
- Centro Ricerche Produzioni Animali, C.R.P.A. S.p.A., Viale Timavo, 43/2, 42121 Reggio Emilia, Italy
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