Software engineering as a discipline has recognised that software systems can have an impact on sustainability, and researchers have started to investigate this topic. New knowledge is being created and methods, and tools that support software engineering for sustainability are emerging. Several universities have started to train their students in software engineering for sustainability. But what about the millions of SE practitioners who are already designing and developing future software systems - how would they know about making systems sustainable? Currently, there is a lack of consolidated guidance. In this paper, we promote the idea of developing a standardised curriculum and handbook as a basis for the training and certification of practitioners in sustainable software development. This would not only increase their market value but would also have a positive impact on their companies and could help to satisfy customers who demand sustainable software systems.