Smart cities must adopt innovative technologies and strategies to boost existing sustainability solutions in order to fight climate change and reduce greenhouse gas emissions. We provide an overview of the existing work on the application of blockchain technologies in conjunction with other digital technologies such as IoT for incentivizing individuals and organizations to engage in more sustainable behaviors. We focus on three main areas in which these digital technologies can encourage actions aimed at reducing environmental impact: low-carbon transportation, energy efficiency, and waste diversion. Some notable examples are The Plastic Bank, ECO-Coin and SolarCoin. By analyzing case studies in which monetary and non-monetary incentives have successfully demonstrated behavior change, we seek to understand the key elements for implementing blockchain-based solutions. We also identify key directions for future research in this area.