Sustainability involves a process component; the process by which decisions are made must itself promote sustainability because only through sustainable processes can substantively sustainable decisions ultimately be made. This process component can be found both in the concept of what sustainability is as well as the foundational documents of sustainability. A core component of sustainable processes is public participation in environmental decision making, as such participation makes the resulting decisions more sustainable because public participation makes for more knowledgeable, credible, and transparent decisions. From these general concepts, general principles of sustainable public participation emerge which recognize that decision making processes are more sustainable (and therefore foster sustainability) (1) the more they include opportunities for public participation, (2) the more the opportunities for public participation are meaningful in time and scope, and (3) the more the opportunities for public participation can affect the actual decision. This chapter discusses these general concepts of the process component of sustainability, and then applies those concepts to the public participation available in Pennsylvania’s regulatory regime for development of Marcellus Shale natural gas reserves. It finds that these public participation opportunities are constrained and much more limited than what Pennsylvania allows in other permitting/regulatory regimes. It concludes that the Marcellus Shale public participation regime is not sustainable, and offers suggestions for how to make the process more sustainable.