The demand for sustainable finance has exploded in the last few years. It is a hotbed of innovation as debt issuers look to make the most of investors’ desire to fund a better world. This week GlobalCapital considers one of the most recent innovations: sustainability-linked debt. The format is simple; a borrower pays more or less on its debt depending on whether it meets certain sustainability targets. But two deals this week highlighted some of the controversies this nascent market faces over its credibility.