Bill Joy, founder of Sun Microsystems and partner at the venerable venture capital firm Kleiner Perkins Caulfield and Byers, is talking up a handful of companies he’s invested in that make use of abundant materials—in some cases materials that get thrown away or burned up—to make valuable commodities and reduce carbon emissions and replace petroleum. He described the new companies today at the Emtech Conference in Cambridge, Massachusetts.

Solidia: The company, based on technology developed at Rutgers, is using carbon dioxide to make building materials that have the strength of concrete, but that rather than emitting one ton of carbon dioxide per ton of concrete, Joy says, it actually uses carbon dioxide as a building material.

Siluria: Natural gas is extremely abundant, but it’s not useful for much other than burning it to generate electricity. Unlike oil, it isn’t a good building block for drugs and plastics. And unlike oil, it’s difficult to ship. To this day, some oil fields burn off the natural gas that comes up the well because there’s no economic way to get it to market. Siluria is using directed evolution techniques developed at MIT to quickly sort through large numbers of potential catalysts for breaking down methane and forming building blocks that can be used to make ethylene, an important feedstock material, and eventually a range of chemicals and liquid fuels. The company says it’s catalysts work well enough now to make liquid fuels at about $50 a barrel.

Renmatix: Cellulosic materials like wood chips are abundant, but turning them into sugar, which can be used to make ethanol and diesel—is expensive. Renmatix uses water at high temperatures and pressures to break cellulose down. The company says it will be cheaper because it doesn’t require the enzymes or expensive catalysts used in current methods.

Aquion: The company is building cheap batteries to store power from wind turbines and solar panels, which could be key to making up for the variability of these electricity sources. The battery uses abundant materials—manganese, salt, water, and carbon—rather than potentially expensive metals like nickel.