Integrating blockchain with energy trading is a new paradigm for researchers working in the field of smart grid. In energy trading, auction theory plays an important role to ensure truthfulness, rationality, and to balance utility of participants. However, traditional energy auctions cannot directly be integrated in blockchain based auctions due to the decentralized nature. Therefore, researches are being carried out to propose more efficient decentralized auctions for energy trading. Despite of all these advances, a greater standpoint that is not well-highlighted or discussed in majority of proposed mechanisms is the integration of green aspect in these auctions. Since, blockchain is a novel paradigm to ensure trust but it also comes up with a curse of high computation and communication complexity which eventually causes resource scarcity. Therefore, there is a need to develop and encourage development of more green auctions to carry out decentralised energy trading. In this paper, we first provide a thorough motivation of decentralized auctions over traditional auctions. Afterwards, we provide in-depth design requirements that can be taken into consideration while developing such auctions. After that, we analyse technical works that have developed blockchain based energy auctions from green perspective. Finally, we summarize the article by providing challenges and possible future research directions of blockchain based energy auction from green viewpoint.