Environmental issues are increasingly discussed through social media applications. Consequently, researchers are beginning to question whether social media could represent a green virtual sphere: a virtual public space to discuss environmental issues not governed by a single authority in which anyone can access; however, limited empirical research has been conducted to date. In response, this study combines text analysis, social network analysis, and semi-structured interviews to determine whether discussions regarding the Alberta oil sands and the Northern Gateway Pipeline on Twitter – a micro-blogging site – reflect the characteristics of a green virtual sphere. It was found that Twitter is used to disseminate information, access news, and engage in debate, but there are limitations: not everyone has access to Twitter, the government may monitor online activity, and discussions appear to be dominated by environmentalists and environmental organizations. Twitter use on these issues only partially reflects the characteristics of a green virtual sphere.