A Durham venture fund company that invests in businesses in the clean tech sector has launched its third fund.

At $75 million, SJF Ventures' newest fund will be twice as big as the previous two funds combined, said company co-founder David Kirkpatrick.

The new fund, called SJF Ventures III, has raised about half the money it needs towards its $75 million target. The lead investor is Citi Community Capital, an investing group within Citi, the New York investment bank.

SJF, with six employees and satellite offices in San Francisco and New York, invests in companies that specialize in recycling, renewable energy, energy efficiency, sustainability and related technologies. SJF requires a minimum investment of $250,000 for individual investors and $2 million for institutional investors.