Despite the move to renewables gaining pace around the world, fossil fuel-fired power plants will be pumping greenhouse gases into the atmosphere for a long time to come. Now researchers at Oak Ridge National Laboratory (ORNL) have developed a new substance that could effectively soak up carbon from coal-fired power plant emissions, using much less energy than existing methods.
The key to the new technology is a class of organic compounds known as bis-iminoguanidines (BIGs), which bind to specific anions – negatively charged ions – over others. The ORNL researchers realized that included bicarbonate anions, meaning they could be put to work grabbing carbon dioxide.
The team developed a watery BIG solution, then piped flue gas through it. The CO2 molecules bind to the BIG sorbent, which then crystallize into a solid bicarbonate salt. After enough has been collected, these solids can then be filtered out of the mixture, and the CO2 can be extracted by heating them to 120° C (248° F). After that, the solid BIG sorbent can be dissolved back into water and used again indefinitely. Meanwhile the CO2 can be sent off for storage and use, whether that's underground, as concrete or even to add the bubbles to fizzy drinks.
The researchers say their system uses about 24 percent less energy than existing methods, which often use liquid sorbents that require higher temperatures to heat. The team also found that after 10 consecutive cycles, they lost almost none of the solid sorbent – liquid ones tend to evaporate away over time.
"The main advantage of our 'organic soda lime' is that it can be regenerated at much lower temperatures and with significantly less energy consumption compared to inorganic scrubbers," says Radu Custelcean, senior author of the study. "The lower energy required for regeneration is expected to significantly reduce the cost of carbon capture, which is critical considering that billions of tons of CO2 need to be captured every year to make a measurable impact on the climate."
As well as it works in tests, the team says there are still kinks to iron out before the technology can be scaled up. The BIG sorbents take a while to absorb the CO2, and can't hold too much of it at once, which the researchers blame on the fact that BIG doesn't dissolve all that well in water.
"We are currently addressing these issues by combining the BIG sorbent with traditional sorbents, such as amino acids, to enhance the capacity and absorption rate," says Custelcean. "We are also adjusting the process so it can be applied to CO2 separation directly from the atmosphere in an energy-efficient and cost-effective way."
The research was published in the journal Chem.
Source: Cell Press via Science Daily
"Abstract Global environmental change is rapidly altering the dynamics of terrestrial vegetation, with consequences for the functioning of the Earth system and provision of ecosystem services1,2. Yet how global vegetation is responding to the changing environment is not well established. Here we use three long-term satellite leaf area index (LAI) records and ten global ecosystem models to investigate four key drivers of LAI trends during 1982–2009. We show a persistent and widespread increase of growing season integrated LAI (greening) over 25% to 50% of the global vegetated area, whereas less than 4% of the globe shows decreasing LAI (browning). Factorial simulations with multiple global ecosystem models suggest that CO2 fertilization effects explain 70% of the observed greening trend, followed by nitrogen deposition (9%), climate change (8%) and land cover change (LCC) (4%). CO2 fertilization effects explain most of the greening trends in the tropics, whereas climate change resulted in greening of the high latitudes and the Tibetan Plateau. LCC contributed most to the regional greening observed in southeast China and the eastern United States. The regional effects of unexplained factors suggest that the next generation of ecosystem models will need to explore the impacts of forest demography, differences in regional management intensities for cropland and pastures, and other emerging productivity constraints such as phosphorus availability. https://www.nature.com/articles/nclimate3004
As to the AGW hypothesis, here is an interesting graph of the historical estimates of CO2 sensitivity (the increase in temperature associated with a doubling of atmospheric CO2 level): https://postimg.cc/47w6x3Cg Consider the effect of extrapolating the ECS and TCR trend lines out to 2025 or 2020...