A Glimpse Into Our Future
Tony Mirabella, Technical Editor, District Energy
Over the past several months, the U.S. Department of Energy has committed more
than $60 million for studies and education programs to further knowledge on how
to store carbon captured from fossil fuel-burning power plants. The research grants
include characterization studies of geologic formations for carbon dioxide storage
and funds for universities to develop research programs and geophysical models.
Most of today’s research is directed towards carbon capture and storage (CSS).
There are three main scenarios under consideration:
Pre-combustion capture – This concept removes the carbon from the fuel before
combustion takes place. The resultant fuel is basically hydrogen gas. The carbon,
most likely in the form of CO2, is then piped (like natural gas) cross-country to
underground geologic storage locations. Reforming natural gas to hydrogen and
CO2 is common in the fueling of fuel cells, notably the United Technologies PC- 25
fuel cell.
Post-combustion capture – As the name states, this concept removes the CO2
from the flue gas stream, compresses the CO2, and then transports it to storage.
Oxyfuel combustion capture – In this technique, which is primarily aimed at
coal-burning power plants, combustion air is replaced with essentially pure oxygen. The
flue gas resulting from combustion is basically pure CO2, absent water
vapor and nitrogen, and requires no post-combustion separation. The CO2 is then
compressed and piped to storage.
All of the above scenarios are in the early stages of development, and all can be
expensive to implement. Capital costs as well as operating costs could drive up the
costs of producing electricity while at the same time increasing the demand for electricity to operate the additional CO2 separation equipment.
As described in the accompanying article, the alternative to CCS is carbon recycling. This technique differs from CCS in that it uses the waste gas stream from fossil
fuel combustion as raw material to produce a commodity of value. This approach
may not offer any upfront cost savings but may generate revenues to help provide a
return on the investment in additional plant equipment.
Although it’s too soon to tell how – or whether – carbon recycling and CCS will
find application in the district energy industry, system owners and operators should
take note that these technologies are in development. At the very least, they provide
us a glimpse of what our kids and grandkids may be working on implementing in
the future.
Figure 1. Electro-reduction of CO2 (ERC) schematic: an electrochemical process.
Courtesy Mantra Venture Group.
that captures and sequesters CO2 from
a coal-fired power plant as of yet exists.
The IEA is hopeful that 10 full-scale
demonstration plants will be up and
running globally by 2015, meaning it
may be 10 to 20 years before CCS technology is readily available.
So why expensively transport and
store the CO2 underground when it could
be profitably recycled post-capture?
Researchers and startup companies are
now investigating a wide range of CO2
conversion methods.
“The market is open for innovation,”
states Larry Kristof, CEO of Mantra
Energy, a company gaining international
recognition in the field of carbon recycling. “It is likely that governments will
soon legally mandate carbon capture
from industrial plants and there needs to
be a cost-effective way to implement it.”
Mantra’s technology, named the
electro-reduction of CO2 (ERC), aims to
take CO2 directly from industrial waste
gases and convert it to formate salts
and/or formic acid, both valuable chemicals used in a variety of industrial
applications. (See fig. 1.) Formic acid
also has the potential to play a leading
role in fuel cell development, both as a
direct fuel and as a fuel storage material
for on-demand release of hydrogen. The
ERC technology could provide a net revenue of up to $700 per tonne of CO2
recycled, with a return on investment
previously forecast at 20 percent per
year, depending on local costs.
Compared with CCS, the ERC provides a positive ROI, not an unrecoverable cost. Plus a demonstration ERC unit
could be installed at a client’s premises
within a year and a commercial plant
within two years, much faster than for CCS.
In a speech to the U.S. Senate, Margie
Tatro, director of fuel and water systems at Sandia National Laboratories, a
U.S. Department of Energy-run research
center formed to develop science-based
technologies that support national security, advocated that carbon recycling is
the way of the future.
“We must act now to stimulate this
area of research and development. Other
countries are exploring reuse and recycling of CO2, and it would be unfortunate
if the U.S. became dependent on imported
technology in this critical area,” said Tatro.
