How to save the world and make a fortune? Come up with an alternative to petroleum. Countless companies, backed by billions in investments, are trying. Here's how some of the more esoteric efforts stack up.

• Dyadic International Jupiter, FL
  Proposition: Improve efficiency of corn-based ethanol production with enzymes from the Russian Chrysosporium lucknowense mushroom, previously used to produce stonewashed jeans. Dyadic is also studying applications for cellulosic ethanol derived from switchgrass, and from agriculture wastes including spent sugar cane and citrus peels.
  Potential: Funded to the tune of $35.5 million, Dyadic already has sequenced the mushroom genome with Scripps Research Institute; that's set for product development. It expects its enzymes could help churn out 20% more ethanol from corn, making the fuel more competitive with oil. Enzyme research is hot, though, so Dyadic has plenty of competition.


• FirmGreen Energy Inc. Newport Beach, CA
  Proposition: Use trash from landfills to produce ethanol, natural gas, and methanol for biodiesel and electricity. It's been building a facility in Grove City, Ohio, this summer that would make 20 million gallons per year of methanol.
  Potential: FirmGreen, which is developing 42 landfill projects around the world, has already sealed seven contracts to sell fuel from the Grove City plant, including one with Mitsubishi Gas Chemical Co. America. The Solid Waste Authority of Central Ohio converted its first vehicle to use fuels from FirmGreen's landfill gas and plans to adapt the rest of its 26 vehicles by 2012. Capital investments will be high, but there's no shortage of trash.


• Hythane Co. Littleton, CO
  Proposition: Build the infrastructure for hydrogen-powered transportation with "hythane"--a mix of hydrogen and natural gas. The company has to persuade commercial fleets to convert their engines, create and sell equipment to mix the fuel, then build a network of hythane fueling stations.
  Potential: Hythane has converted four buses in Palm Springs, California, to run on its fuel and signed letters of intent to do the same with fleets in Fresno and six Chinese cities. Hydrogen is a vast renewable energy source that produces half the emissions of natural gas. But it's hard to store and transport, and mass use would require overhauling millions of car engines and filling stations.


• SeQuential Biofuels Portland, OR
  Proposition: Regional production of biodiesel using cooking oils from potato-chip maker Kettle Foods, restaurant chain Burgerville, and regional canola farmers. Its refinery in Salem, Oregon, can produce 1 million gallons of fuel a year, and its first retail station was set to open in August.
  Potential: With an investment from crooner Willie Nelson and partnerships with around 16 petroleum distributors, SeQuential has set up about 20 distribution points in Oregon. Biodiesel produces 78% less carbon dioxide emissions than petroleum-based fuels, and the market is huge: Trucks and cars consume about 2 million gallons of diesel a day in Oregon alone.