Carbon sequestration
From dKosopedia
In an effort to stem the increase in atmospheric levels of greenhouse gases such as carbon dioxide, and slow the onset of global warming, without making the necessary sacrifices with regards to consumption of fossil fuels, efforts are underway to possibly sequester carbon dioxide underground or in the oceans. Without carbon sequestration, a hydrogen infrastructure and economy would not make any greater environmental impact than increased use of nuclear or renewable energy would on their own.