Ethanol maker Range Fuels has raised nearly $100 million in new financing, the latest in big-money deals for companies focused on commercially producing the alternative transportation fuel.

In recent weeks, Mascoma raised $50 million in a third round of venture funding, and the U.S. Department of Energy said it will invest more than $30 million in four other companies in the industry.

This funding round for Mascoma, which was first reported by VentureWire on Friday, means that at least three startups focused on cellulosic ethanol have now amassed financing greater than $100 million.

The companies are Broomfield, Colorado-based Range Fuels with at least $182 million; Mascoma, of Cambridge, Massachusetts, with at least $109 million; and Ottowa, Canada’s Iogen Corporation with at least $130 million.

These companies and others are racing to prove that cellulosic ethanol production is economically viable. Several companies in the industry have built pilot plants and have begun work on production facilities.

Proponents say that cellulosic ethanol could eventually be widely used as a replacement for conventional gasoline. U.S. President Bush has set a goal of making it cost-competitive with gasoline by 2012. But business executives and their investment backers would like it to happen sooner.

Cellulosic ethanol is widely seen as a better alternative fuel than traditional corn-based ethanol. It requires less water to make, generates less greenhouse gasses, and uses non-food feedstocks, like fast-growing grasses, agricultural residues, and forest biomass.

The rise in demand for corn to make traditional ethanol has been linked to a surge in world food prices.