While emergy analysis (i.e. emergy synthesis, environmental accounting) was developed in the early 1980s by H.T. Odum, building upon his seminal work outlining the energy basis for man and nature, the method is still developing. Some very important aspects of the method, such as the global baseline for renewable emergy and how the emergy yield ratio (EYR), a critical index for implicating the contribution of a process to society, is to be calculated are still under debate in the scientific community. This makes it all the more critical that when an emergy analysis is done all methodology is laid bare and justified. Unfortunately, Zhang et al. (2012. Energy Policy 42, pp 232-238) is deficient in doing so. In the response below I lay out the problems I observed in the paper and propose a revision to their analysis. I should note that no issues were found with the embodied energy portion of the analysis and the inconsistencies with accepted methodology were likely due to an unfamiliarity with the emergy method. (C) 2013 Elsevier Ltd. All rights reserved.