There is not a single renewable energy source that is a net negative over its lifetime. We have gotten very efficient over the past 40 years since that factoid may have once been true.

That is not to say that this study did not engage in a lot of hand-waving assumptions (the claim that a small fraction of total power that was hydro could cover solar/wind fluctuations for base load is delusional to be point of being outright deceptive) and is light on a practical path from here to there, but if you were to add a nuclear component that was 30-40% of the total I would not find the paper's claims to be completely unreasonable.