Known as "Fidelito" or "little Fidel" in his home country, the nuclear scientist visited the University of Strathclyde in his role overseeing a joint venture between Cuba's sugar ministry and Havana Energy to build biomass plants to power the Caribbean country's sugar refineries. Strathclyde and Sheffield universities have been helping the Cubans develop the technology.
Havana Energy, a subsidiary of Guernsey-based Esencia Group, which has various UK-Cuban business interests, is chaired by former Labour energy minister, Brian Wilson.
During his two-day visit, Dr Castro also met Lord Provost of Glasgow Sadie Docherty and vistied the Auchentoshan whisky distillery in Clydebank, with a view to applying the plant's energy-efficiency techniques to Cuba's rum distilleries.
Castro, who did not meet anyone from the Scottish Government, said he saw nanotechnology – a leading Cuban industry – and energy as areas for close co-operation.