Blockchain and distributed ledger technologies (BC/DLT) have attracted social and scientific attention at least since the success of Bitcoin and Ethereum as so-called cryptocurrencies. This attention leads to multidisciplinary dynamics whose euphoria often leads to a neglect of scientific thoroughness. As one facet, immutability is a core characteristic and often postulated property of the system. However, it is hardly possible to identify an analysis of the counter side, namely the sustainability of this technology. This article deals with different aspects of the sustainability of BC/DLT and relates them to the requirements of BC/DLT.