WASHINGTON — The Senate energy committee formally approved the nomination of Ernest J. Moniz to be energy secretary, the committee announced on Thursday.

The 21-to-1 vote is an indication that Mr. Moniz, who served as an undersecretary in the Energy Department in the Clinton administration, will have no trouble being confirmed by the full Senate. Some opponents had complained that an energy initiative he leads at the Massachusetts Institute of Technology is financed heavily by the oil industry and other conventional energy industries. Mr. Moniz is a physicist and strong advocate of natural gas and nuclear power as cleaner alternatives to coal.

The dissenter was Senator Tim Scott, Republican of South Carolina, who had tried during Mr. Moniz’s confirmation hearing to pin him down on a major project at a nuclear facility near Aiken, S.C., to convert plutonium from retired nuclear weapons into fuel for power reactors. The project has turned out to be far more difficult than first envisioned, and may be canceled. Mr. Scott has been urging its completion.

Mr. Moniz would not say whether the project would be finished. About $6 billion has been spent on the plant. Mr. Moniz was involved in negotiating the treaty with Russia on destruction of plutonium, and the project in South Carolina is supposed to uphold the American end of that deal.