C12 Energy, a stealthy startup looking to lower the cost of routine carbon sequestration, just raised $4.5 million from Sequoia Capital and other undisclosed investors. Very little is known about the company’s technology or what it does — except that its chief scientist just registered a patent for electrochemical weathering, a process that allows the ocean to effectively absorb carbon dioxide, reports VentureWire.

While C12 has had to tighten its belt due to the downturn, pushing potential commercialization of the product even further into the future, important progress has already been man, the company says. Its executives have argued in the past that carbon sequestration won’t take off until a value is attached to carbon emissions. They have suggested tax incentives and a cap-and-trade system to this end, but neither have been widely adopted.

Not to say that carbon sequestration isn’t a ripe market. Before 2009 is over, more than $20 billion will have been spent on these projects since 2007. The real challenge will be to make the process itself cheaper, which should help convince industrialists and other potential consumers of the technology that managing emissions is worth it.