Some possible URLs for reference (note that this item is not without its controversies, so we will need to be balanced): 
 *https://www.denvergov.org/content/denvergov/en/mayors-office/newsroom/2009/mayor-hickenlooper-denver-zoo-officials-sea-lion-announce-signif.html 
 *http://voices.nationalgeographic.com/2012/10/08/from-poop-to-power-the-denver-zoo-is-one-of-the-greenest-of-the-green/ 
 *http://realestate.aol.com/blog/videos/green-living/517364947/ 
 *http://glendalecherrycreek.com/2015/08/questions-linger-over-denver-zoos-plan-to-convert-trash-manure-to-energy/ (the project was not without controversy) 
 *http://www.huffingtonpost.com/2011/09/19/the-denver-zoo-wins-the-f_n_970442.html (additional citation for AZA award) 
 *http://www.latimes.com/nation/la-na-sej-elephant-dung-story.html (has it fallen through? Sept 2015) 
 *http://www.arcamax.com/currentnews/newsheadlines/s-1728694 
 *https://www.aza.org/Membership/detail.aspx?id=17624 (AZA Green Award - shows all winners) 
 *http://www.denverwater.org/WaterQuality/RecycledWater/RecycledWaterNews/DenverZoo/ (water conservation) 
 *https://zerowastedenver.wordpress.com/2015/09/01/questions-linger-over-denver-zoos-plan-to-convert-trash/