The Milken foundation acted like a venture capital firm, funding high-risk projects unlikely to win government grants and wooing young researchers into the field.

FORBES: Disease and Redemption

The inherent uncertainty in investing in novel technologies, coupled with the high capital costs and long time horizons, prohibits most venture capital funds from investing in large-scale clean energy projects.

FORBES: Solyndra's Failure Is No Reason To Abandon Federal Energy Innovation Policy

Meanwhile, a breakthrough in cellulosic ethanol will come "sooner than you think, " asserts Martin Lagod, a venture capitalist with Firelake Capital Management, which has invested in a range of alternative energy projects.

FORBES: Ethanol Gusher!