Meta-analysis of methane yields from anaerobic digestion of dairy cattle manure

Abstract

This work presents a novel meta-analysis for methane yields from anaerobically digesting dairy cattle manure. A database is compiled from 115 articles (2,181 cases) by systematically assessing the academic literature. Y CH4 and secondary variables collected in the database describe performance, operation conditions of digester and manure composition. Inputs to the database are normalised to enable inter-study uni-and multi-variate analysis, according to different types of digesters. Most cases (N=1,299) are reported for batch digesters and meta-analysis results in a mean Y CH4 of 0.230±0.016 m 3 kg −1. CSTR (N=241), results in mean of 0.190±0.016 m 3 kg −1 (random-effect model). Other continuous digesters, such as fixed-film, plug-flow and UASB require further cases for the application of meta-analysis. For non-specified semi-continuous digesters (N=347), the mean calculated by the random-effect model is 0.204±0.032 m 3 kg −1 (N=27). With respect to multi-variate analysis of operation conditions, batch digesters form four clusters, while two clusters are identified for CSTR and three for semi-continuous digesters. For variables describing manure composition, batch digesters present eight clusters, while CSTR and semi-continuous digesters have insufficient cases. The strongest correlations found for these secondary variables (Spearman's rho:-0.685 and-0.696) result for pH and Y CH4 in batch and CSTR, respectively. Maximum Y CH4 estimated by meta-analysis are proposed to replace the default IPCC values because they are based on a larger sample size and integrate updated literature. In particular, markedly higher Y CH4 are obtained for Asia, Middle East and Indian Subcontinent than those in the IPCC guidelines.

Upgrading biogas produced at dairy farms into renewable natural gas by methanation

“…The production of RNG from the addition of hydrogen to anaerobic digested biogas is an area of increasing importance . There are currently 244 anaerobic digesters operating in farms in the United States of America, with animal manure as the only feedstock .…”

Study of the performance of biogas production by mixed fermentation of cow dung, deer manure, and mushroom fungus

“…34 As shown in Figure 3, the total biogas production of the U3 experimental groups was about 6000 mL at 35°C, while that of the total biogas production was close to 7000 mL at 50°C, and the biogas production increased by about 10%. 34 As shown in Figure 3, the total biogas production of the U3 experimental groups was about 6000 mL at 35°C, while that of the total biogas production was close to 7000 mL at 50°C, and the biogas production increased by about 10%.…”

“…It was found that the biogas production regularity of U3 experimental group was basically the same as that of AD of cow dung alone at 55°C. 34 As shown in Figure 3, the total biogas production of the U3 experimental groups was about 6000 mL at 35°C, while that of the total biogas production was close to 7000 mL at 50°C, and the biogas production increased by about 10%. After calculation, the highest daily biogas production of U3 experimental group at 55°C is 521.4 mL·d −1 , and the unit TS biogas production rate can reach 0.23 L·g −1 .…”

The Future Agricultural Biogas Plant in Germany: A Vision

“…Biogas production from liquid and solid manure does not only contribute to energy supply, but is also an essential measure of integrated manure management strategies to reduce environmental impacts [76,77]. Methane yields depend mainly on animal species [78,79] and further on their type of use, sex, age and diets [80][81][82]. The potential for influencing feedstock characteristics seems small.…”