Meta-analysis of methane yields from anaerobic digestion of dairy cattle manure.
|Title||Meta-analysis of methane yields from anaerobic digestion of dairy cattle manure.|
|Publication Type||Journal Article|
|Year of Publication||In Press|
|Authors||Miranda, ND, Granell, R, Tuomisto, HL, McCulloch, MD|
|Journal||Biomass & Bioenergy|
|Keywords||Anaerobic digestion, biogas, dairy, manure management., methane yield|
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. YCH4 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 YCH4 of 0.230m3kg−1. CSTR (N=241), results in mean of 0.190 m3kg−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 m3kg−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 YCH4 in batch and CSTR, respectively.
Maximum YCH4 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 YCH4 are obtained for Asia, Middle East and Indian Subcontinent than those in the IPCC guidelines.