Pilot-scale anaerobic co-digestion of municipal biomass waste and waste activated sludge in China: Effect of organic loading rate
The effects of organic loading rate on the performance and stability of anaerobic co-digestion of municipal biomass waste (MBW) and waste activated sludge (WAS) were investigated on a pilot-scale reactor. The results showed that stable operation was achieved with organic loading rates (OLR) of 1.2-8.0kgvolatile solid (VS)(m(3)d)(-1), with VS reduction rates of 61.7-69.9%, and volumetric biogas production of 0.89-5.28m(3)(m(3)d)(-1). A maximum methane production rate of 2.94m(3)(m(3)d)(-1) was achieved at OLR of 8.0kgVS(m(3)d)(-1) and hydraulic retention time of 15days. With increasing OLRs, the anaerobic reactor showed a decrease in VS removal rate, average pH value and methane concentration, and a increase of volatile fatty acid concentration. By monitoring the biogas production rate (BPR), the anaerobic digestion system has a higher acidification risk under an OLR of 8.0kgVS(m(3)d)(-1). This result remarks the possibility of relating bioreactor performance with BPR in order to better understand and monitor anaerobic digestion process.
[Show abstract] [Hide abstract] ABSTRACT: Anaerobic co-digestion of cyanide-containing cassava pulp with pig manure was evaluated using laboratory scale mesophilic digester. The digester was operated in a semi-continuous mode with the mixed feedstock having C/N ratio of 35:1. Digester startup was accomplished in 60days with loading of 0.5-1kgVS/m(3)d. Subsequently, the loading to digester was increased step-wise from 2 to 9kgVS/m(3)d. Digester performance was stable at loading between 2 and 6kgVS/m(3)d with an average volatile solid removal and methane yield of 82% and 0.38m(3)/kgVSadded, respectively. However, beyond loading of 7kgVS/m(3)d, solubilization of particulate matter did not take place efficiently. Cyanide present in cassava pulp was successfully degraded indicating that anaerobic sludge in the digester was well acclimatized to cyanide. The results show that cassava pulp can be successfully digested anaerobically with pig manure as co-substrate without any inhibitory effect of cyanide present in the cassava pulp.0Comments 0Citations
- "This indicates that the methanogenesis is the rate-limiting step beyond excessive OLR. A similar observation has been reported by Liu et al. (2012). They concluded that during anaerobic co-digestion of municipal biomass waste and waste activated sludge hydrolysis was the rate limiting step at low OLR (1.2–6.0 kgVS/m 3 d). "
[Show abstract] [Hide abstract] ABSTRACT: In this paper, the microbial community in a two-phase thermophilic anaerobic co-digestion process was investigated for its role in hydrogen and methane production, treating waste activated sludge and treating the organic fraction of municipal solid waste. In the acidogenic phase, in which hydrogen is produced, Clostridium sp. clusters represented 76% of total Firmicutes. When feeding the acidogenic effluent into the methanogenic reactors, these acidic conditions negatively influenced methanogenic microorganisms: Methanosaeta sp., (Methanobacteriales, Methanomicrobiales, Methanococcales) decreased by 75%, 50%, 38% and 52%, respectively. At the same time, methanogenic digestion lowered the numbers of Clostridium sp. clusters due to both pH increasing and substrate reduction, and an increase in both Firmicutes genera (non Clostridium) and methanogenic microorganisms, especially Methanosaeta sp. (208%). This was in accordance with the observed decrease in acetic (98%) and butyric (100%) acid contents. To ensure the activity of the acetate-utilizing methanogens (AUM) and the acetogens, high ratios of H2-utilizing methanogens (HUM)/AUM (3.6) were required.0Comments 1Citation
- "The different growth rates and pH optima for hydrogen producing microorganisms (between 5.5 and 6.5) and methanogenic microorganisms (around pH 7), have led to the development of the two-stage AD process (De la Rubia et al., 2009 ). This approach has been used to the hydrogen production (HP) in the first phase reactor and methane production (MP) in the second phase reactor, with the final purpose of mixing the two gasses to achieve bio-Hythane (50–55% CH 4 , 5–10% H 2 and 35–40% CO 2 ), a biogas that offers better combustion and reduced greenhouse gas emissions compared to fossil fuels (Cavinato et al., 2011; Liu et al., 2012). Due to the advantages of the AD process, an ample research has been done on the optimization of AD for treating the organic fraction of municipal solid waste (OFMSW), including the interesting option of the co-digestion process. "
[Show abstract] [Hide abstract] ABSTRACT: Cellulosic crop residues are produced in large quantities in Pakistan and are considered resistant to biological degradation. Partial pretreatment of these crop residues and optimization of the feed rate could have a synergistic effect on the anaerobic co-digestion of organic waste. The aim of this study was to examine the possibility of enhancing biodegradation and biogas production from the anaerobic co-digestion of catering waste and cellulosic crop residues. Post-harvest crop residues (wheat straw and sugar cane bagasse) that are rich in lignocellulose were partially degraded using a combined microwave (800 J/g/min) and steam (121 oC, 40 min) pretreament. These pretreated wastes were co-digested with catering waste at different feeding rates (20–50% based on total solid, w/w) in batch conditions. High organic-matter removal efficiency was obtained from the feed composition of 20% pretreated wheat crop residues. Similarly, high levels of soluble chemical oxygen demand were observed (up to 85% conversion of insoluble chemical-oxygen demand) in the reactor containing the catering waste and pretreated crop residues. The accumulative biogas produced in both treatments was more than double the biogas observed in catering waste alone. The increased biogas production was due to the presence of more biodegradable carbon in the form of soluble chemical-oxygen demand. The results suggest that the use of a low-cost method (microwave and steam) for the partial pretreatment of lignocellulosic crop residues could increase rate of co-digestion and biogas production. This study provides a novel take on anaerobic co-digestion for the degradation of recalcitrant lignocellulosic material, and the development of an energy-efficient strategy for waste management.0Comments 0Citations
- "Catering waste may contain fruit, vegetables, meat and animal by-products that are not only rich in nutrients, but also contain a variety of vitamins and amino acids. Moreover, catering wastes associated with the transportation industry, such as airports and others, which contain lots of animal by-products are considered very dangerous for the environment, and carry the risk of spreading contagious diseases to animals and humans (Ghiani et al., 2014; Liu et al., 2012). Production in large quantities is also becoming a concern in municipal landfills because of high methane production (Izumi et al., 2010; Zhang et al., 2005). "