LONDON (Reuters) – Euroclear, one of the world’s biggest settlement systems for stock and bond trades, has bought a big stake in fintech Greenomy to tap into growing demand for services that help firms meet new rules on reporting their environmental impact. The European Union is rolling out mandatory environment, social and governance (ESG) reporting for companies and asset managers to give investors more comparable information about the impact of climate change and other factors on their businesses. Brussels based Euroclear, which settles trades executed on pan-European stock exchange Euronex…