Energy and Changes in the Environment - Hydrogen and Fuel Cells: Advances in Transportation and Power - page 60

record of the earth, but deforestation also had a major impact on carbon
in the atmosphere. Forests serve as carbon sinks, producing oxygen while
using carbon dioxide.
The clearing of forests in the United States early in the century,
combined with a large increase in postwar tropical deforestation, where
much of the wood was burned, released carbon dioxide to the air and
changed the atmospheric components.
Carbon could be filtered from power plant emissions, compressed
into a liquid, and pumped into ocean depths of ten thousand feet. Here,
the water pressure would compress liquid carbon dioxide to a high enough
density to pool on the seafloor before dissolving. At shallower depths it
would just disperse. However, injecting vast quantities of carbon dioxide
could acidify the deep ocean and harm marine life. Protesters have forced
scientists to cancel experiments to test the scheme in Hawaii and Norway.
Researchers at the Monterey Bay Aquarium Research Institute,
believe that rising carbon dioxide in the atmosphere will acidify the
ocean's surface waters in any case and pumping some of the carbon into
the ocean depths could slow that process.
Another plan is to pump the carbon into coal seams, old oil and
gas fields and deep, porous rock formations. This high-pressure injection
would also release the remaining oil or gas out of depleted fields.
SEQUESTRATION
Sequestration involves storing CO 2 in large underground formations.
CO 2 separation and capture are part of many industrial processes, but
using existing technologies would not be cost-effective for large-scale
operations. Sequestration costs using current technology are quite high.
The practicality and environmental consequences of many
sequestration techniques have not yet proven from an engineering
or scientific aspect. Sequestration still requires much research and
development before generating large volumes of hydrogen from coal and
sequestering the CO 2 produced. CO 2 sequestration on a massive scale
would need to be permanent to be practical.
Geologic sequestration is already being done in the North Sea.
The field produces gas that is heavily contaminated with natural carbon
dioxide. Before shipping the gas, the Norwegian oil company Statoil filters
out the carbon dioxide and injects it into a sandstone formation half a mile