Effects of Temperature and Carbon-Nitrogen (C/N) Ratio on the Performance of Anaerobic Co-Digestion of Dairy Manure, Chicken Manure and Rice Straw: Focusing on Ammonia Inhibition

Abstract

Anaerobic digestion is a promising alternative to disposal organic waste and co-digestion of mixed organic wastes has recently attracted more interest. This study investigated the effects of temperature and carbon-nitrogen (C/N) ratio on the performance of anaerobic co-digestion of dairy manure (DM), chicken manure (CM) and rice straw (RS). We found that increased temperature improved the methane potential, but the rate was reduced from mesophilic (30∼40°C) to thermophilic conditions (50∼60°C), due to the accumulation of ammonium nitrogen and free ammonia and the occurrence of ammonia inhibition. Significant ammonia inhibition was observed with a C/N ratio of 15 at 35°C and at a C/N ratio of 20 at 55°C. The increase of C/N ratios reduced the negative effects of ammonia and maximum methane potentials were achieved with C/N ratios of 25 and 30 at 35°C and 55°C, respectively. When temperature increased, an increase was required in the feed C/N ratio, in order to reduce the risk of ammonia inhibition. Our results revealed an interactive effect between temperature and C/N on digestion performance.

Alkali pretreatment at ambient temperature: A promising method to enhance biomethanation of rice straw

“…Biogas production was lower at 42 ºC and the lowest at 30 ºC among the temperatures tested.However, difference in the biogas yield was less than 20% on either side of the optimum temperature, which suggested stability of biogas digester over the temperature range tested. The highest methane potential (272 L/kg VS) at 35 ºC was reported byWang et al (2014). Comparatively higher methane yield (282 L/kg VS) was reported in the present study at 37 ºC.…”

Thermophilic Anaerobic Digestion: Enhanced and Sustainable Methane Production from Co-Digestion of Food and Lignocellulosic Wastes

“…The use of co-substrates for AD has shown to produce higher biogas yields due to positive synergisms established in the digestion medium and the supply of missing nutrients by the co-substrates [15,16]. Mixing organic substrates often results in the formation of a codigestion mixture with a C/N ratio included in the optimal range of 20-30% as reported in the literature [16][17][18]. The additional benefits of the codigestion process are (1) the dilution of the potential toxic compounds present in any of the co-substrates involved; (2) the adjustment of the moisture content and pH; (3) supply of the necessary buffer capacity to the mixture; (4) the increase of the biodegradable material content; and (5) the widening the range of bacterial strains taking part in the process [17].…”

“…The highest methane yield of 305.45 L·kg −1 VS and a VS reduction of 68.5% were obtained with FW:CS:PCG (T5) mixture, while the lowest yield of 219.9 L·kg −1 VS and a VS reduction of 49.8% was observed with FW + UBP + CS (T7) mixture. The higher methane production for some codigestion mixtures over others can be attributed to the C/N ratio for these mixtures which were in the recommended range of 20:1 and 30:1 [18,58].…”

Valorization of Waste Streams from Deinked Pulp Mills through Anaerobic Digestion of Deinking Sludge

“…However, after inoculation with the digested sewage sludge (C/N = 6.2), the inoculated mixtures had more suitable C/N ratios in the range of 6.2 and 9.3 (data not shown), which are required by microorganisms for AD (Wang et al 2014).…”