Lawrence Livermore scientists discover new materials to capture methane

Methane capture in zeolite SBN. Blue represents adsorption
sites, which are optimal for methane (CH4) uptake. Each site
is connected to three other sites (yellow arrow) at optimal
interaction distance. Image credit: LLNL News Release

Scientists at Lawrence Livermore National Laboratory (LLNL) and UC Berkeley and have discovered new materials to capture methane, the second highest concentration greenhouse gas emitted into the atmosphere.

Methane is a substantial driver of global climate change, contributing 30 percent of current net climate warming. Concern over methane is mounting, due to leaks associated with rapidly expanding unconventional oil and gas extraction, and the potential for large-scale release of methane from the Arctic as ice cover continues to melt and decayed material releases methane to the atmosphere. At the same time, methane is a growing source of energy, and aggressive methane mitigation is key to avoiding dangerous levels of global warming.

The research team, made up of Amitesh Maiti, Roger Aines and Josh Stolaroff of LLNL and Professor Berend Smit, researchers Jihan Kim and Li-Chiang Lin at UC Berkeley and Lawrence Berkeley National Lab, performed systematic computer simulation studies on the effectiveness of methane capture using two different materials - liquid solvents and nanoporous zeolites (porous materials commonly used as commercial adsorbents).

While the liquid solvents were not effective for methane capture, a handful of zeolites had sufficient methane sorption to be technologically promising. The research appears in the April 16 edition of the journal, Nature Communications.

Unlike carbon dioxide, the largest emitted greenhouse gas, which can be captured both physically and chemically in a variety of solvents and porous solids, methane is completely non-polar and interacts very weakly with most materials.

"Methane capture poses a challenge that can only be addressed through extensive material screening and ingenious molecular-level designs," Maiti said.

Methane is far more potent as a greenhouse gas than CO2. Researchers have found that the release of as little as 1 percent of methane from the Arctic alone could have a warming effect approaching that being produced by all of the CO2 that has been pumped into the atmosphere by human activity since the start of the Industrial Revolution.

Methane is emitted at a wide range of concentrations from a variety of sources, including natural gas systems, livestock, landfills, coal mining, manure management, wastewater treatment, rice cultivation and a few combustion processes.

The team's research focused on two different applications -- concentrating a medium-purity methane stream to a high-purity range (greater than 90 percent), as involved in purifying a low-quality natural gas; and concentrating a dilute stream (about 1 percent or lower) to the medium-purity range (greater than 5 percent), above methane's flammability limit in air.

Through an extensive study, the team found that none of the common solvents (including ionic liquids) appears to possess enough affinity toward methane to be of practical use. However, a systematic screening of around 100,000 zeolite structures uncovered a few nanoporous candidates that appear technologically promising.

Zeolites are unique structures that can be used for many different types of gas separations and storage applications because of their diverse topology from various networks of the framework atoms. In the team's simulations, one specific zeolite, dubbed SBN, captured enough medium source methane to turn it to high purity methane, which in turn could be used to generate efficient electricity.

"We used free-energy profiling and geometric analysis in these candidate zeolites to understand how the distribution and connectivity of pore structures and binding sites can lead to enhanced sorption of methane while being competitive with CO2 sorption at the same time," Maiti said.

Other zeolites, named ZON and FER, were able to concentrate dilute methane streams into moderate concentrations that could be used to treat coal-mine ventilation air.

The work at LLNL was funded by the Advanced Research Projects Agency-Energy (ARPA-E).

References

- News Release
Lawrence Livermore scientists discover new materials to capture methane
https://www.llnl.gov/news/newsreleases/2013/Apr/NR-13-04-03.html

-  New materials for methane capture from dilute and medium-concentration sources
http://www.nature.com/ncomms/journal/v4/n4/abs/ncomms2697.html

Related

- Methane sequestration in hydrates
http://arctic-news.blogspot.com/2012/06/methane-sequestration-in-hydrates.html

Another link between CO2 and mass extinctions of species

By Andrew Glikson, Australian National University

Andrew Glikson, earth and
paleo-climate scientist at
Australian National University

It’s long been known that massive increases in emission of CO2 from volcanoes, associated with the opening of the Atlantic Ocean in the end-Triassic Period, set off a shift in state of the climate which caused global mass extinction of species, eliminating about 34% of genera. The extinction created ecological niches which allowed the rise of dinosaurs during the Triassic, about 250-200 million years ago.

New research released in Science Express has refined the dating of this wave of volcanism. It shows marine and land species disappear from the fossil record within 20,000 to 30,000 years from the time evidence for the eruption of large magma flows appears, approximately 201 million years ago. These volcanic eruptions increased atmospheric CO2 and increased ocean acidity.

Mass extinctions caused by rapidly escalating levels of CO2 have occurred before. Global warming image from www.shutterstock.com

Mass extinctions due to rapidly escalating levels of CO2 are recorded since as long as 580 million years ago. As our anthropogenic global emissions of CO2 are rising, at a rate for which no precedence is known from the geological record with the exception of asteroid impacts, another wave of extinctions is unfolding.

Mass extinctions of species in the history of Earth include:

• the ~580 million years-old (Ma) Acraman impact (South Australia) and Acrytarch (ancient palynomorphs) extinction and radiation 
• Late Devonian (~374 Ma) volcanism, peak global temperatures and mass extinctions 
• the end-Devonian impact cluster associated with mass extinction, which among others destroyed the Kimberley Fitzroy reefs (~360 Ma) 
• the upper Permian (~267 Ma) extinction associated with a warming trend
• the Permian-Triassic boundary volcanic and asteroid impact events (~ 251 Ma) and peak warming 
• the End-Triassic (201 Ma) opening of the Atlantic Ocean, and massive volcanism 
• an End-Jurassic (~145 Ma) impact cluster and opening of the Indian Ocean 
• the Cretaceous-Tertiary boundary (K-T) (~65 Ma) impact cluster, Deccan volcanic activity and mass extinction 
• the pre-Eocene-Oligocene boundary (~34 Ma) impact cluster and a cooling trend, followed by opening of the Drake Passage between Antarctica and South America, formation of the Antarctic ice sheet and minor extinction at ~34 Ma. 

Throughout the Phanerozoic (from 542 million years ago), major mass extinctions of species closely coincided with abrupt rises of atmospheric carbon dioxide and ocean acidity. These increases took place at rates to which many species could not adapt. These events – triggered by asteroid impacts, massive volcanic activity, eruption of methane, ocean anoxia and extreme rates of glaciation (see Figures 1 and 2) – have direct implications for the effects of the current rise of CO2.

Figure 1 – Trends in atmospheric CO2 and related glacial and interglacial periods since the Cambrian (542 million years ago), showing peaks in CO2 levels (green diamonds) associated with asteroid impacts and/or massive volcanism. CO2 data from Royer 2004 and 2006.

Figure 2 – Relations between CO2 rise rates and mean global temperature rise rates during warming periods, including the Paleocene-Eocene Thermal Maximum, early Oligocene, mid-Miocene, late Pliocene, Eemian (glacial termination), Dansgaard-Oeschger cycles, Medieval Warming Period, 1750-2012 and 1975-2012 periods.

In February 2013, CO2 levels had risen to near 396.80ppm at Mauna Loa Atmospheric Observatory, compared to 393.54ppm in February 2012. This rise – 3.26ppm per year – is at the highest rate yet recorded. Further measurements show CO2 is at near 400ppm of the atmosphere over the Arctic. At this rate the upper stability threshold of the Antarctic ice sheet, defined at about 500–600ppm CO2 would be reached later this century (although hysteresis of the ice sheets may slow down melting).

Our global carbon reserves – including coal, oil, oil shale, tar sands, gas and coal-seam gas – contain considerably more than 10,000 billion tonnes of carbon (see Figure 5). This amount of carbon, if released into the atmosphere, is capable of raising atmospheric CO2 levels to higher than 1000ppm. Such a rise in atmospheric radiative forcing will be similar to that of the Paleocene-Eocene boundary thermal maximum (PETM), which happened about 55 million years-ago (see Figures 1, 2 and 4). But the rate of rise surpasses those of this thermal maximum by about ten times.

Figure 3 – Plot of percent mass extinction of genera versus peak atmospheric CO2 levels at several stages of Earth history.

Figure 4 – The Paleocene-Eocene Thermal Maximum (PETM) represented by sediments in the Southern Ocean, central Pacific and South Atlantic oceans. The data indicate a) deposition of an organic matter-rich layer consequent on extinction of marine organisms; b) lowering of δ18O values representing an increase in temperature and c) a sharp decline in carbonate contents of sediments representing a decrease in pH and increase in acidity (Zachos et al 2008) 

The Paleocene-Eocene boundary thermal maximum event about 55 million years ago saw the release of approximately 2000 to 3000 billion tons of carbon to the atmosphere in the form of methane (CH4). It led to the extinction of about 35-50% of benthic foraminifera (see Figure 3 and 4), representing a major decline in the state of the marine ecosystem. The temperature rise and ocean acidity during this event are shown in Figures 4 and 6.

Based on the amount of carbon already emitted and which could continue to be released to the atmosphere (see Figure 5), current climate trends could be tracking toward conditions like those of the Paleocene-Eocene event. Many species may be unable to adapt to the extreme rate of current rise in greenhouse gases and temperatures. The rapid opening of the Arctic Sea ice, melting of Greenland and west Antarctic ice sheets, and rising spate of floods, heat waves, fires and other extreme weather events may signify a shift in state of the climate, crossing tipping points.

Figure 5 – CO2 emissions from fossil fuels (2.12 GtC ~ 1 ppm CO2). Estimated reserves and potentially recoverable resources.By analogy to medical science analysing blood count as diagnosis for cancer, climate science uses the greenhouse gas levels of the atmosphere, pH levels of the ocean, variations in solar insolation, aerosol concentrations, clouding states at different levels of the atmosphere, state of the continental ice sheets and sea ice, position of high pressure ridges and climate zones and many other parameters to determine trends in the climate. The results of these tests, conducted by thousands of peer-reviewed scientists world-wide, have to date been ignored, at the greatest peril to humanity and nature.

Continuing emissions contravene international laws regarding crimes against humanity and related International and Australian covenants. In the absence of an effective global mitigation effort, governments world-wide are now presiding over the demise of future generations and of nature, tracking toward one of the greatest mass extinction events nature has seen. It is time we learned from the history of planet Earth.

Figure 6: The Paleocene-Eocene boundary thermal maximum. http://www.uta.edu/faculty/awinguth/petm_research/petm_home.html

This article was earlier published at The Conversation (on March 22, 2013).

Earth is on the edge of runaway warming

The old picture, with Earth well within
our solar system's habitable zone

How well is Earth's orbit around the sun positioned within the boundaries of the habitable zone? The illustration by the Wikipedia image on the right would give that impression that Earth was comfortably positioned in the middle of this zone.

What is the habitable zone? To be habitable, a planet the size of Earth should be within certain distances from its Sun, in order for liquid water to exist on its surface, for which temperatures must be between freezing point (0° C) and boiling point (100° C) of water.

In the Wikipedia image, the dark green zone indicates that a planet the size of Earth could possess liquid water, which is essential since carbon compounds dissolved in water form the basis of all earthly life, so watery planets are good candidates to support similar carbon-based biochemistries.

If a planet is too far away from the star that heats it, water will freeze. The habitable zone can be extended (light green color) for larger terrestrial planets that could hold on to thicker atmospheres which could theoretically provide sufficient warming and pressure to maintain water at a greater distance from the parent star.

A planet closer to its star than the inner edge of the habitable zone will be too hot. Any water present will boil away or be lost into space entirely. Rising temperatures caused by greenhouse gases could lead to a moist greenhouse with similar results.

The distance between Earth and the Sun is one astronomical unit (1 AU). Mars is often said to have an average distance from the Sun of 1.52 AU. A recent study led by Ravi Kopparapu at Penn State mentions that early Mars was warm enough for liquid water to flow on its surface. However, the present-day solar flux at Mars distance is 0.43 times that of Earth. Therefore, the solar flux received by Mars at 3.8 Gyr was 0.75 × 0.43 = 0.32 times that of Earth. The corresponding outer habitable zone limit today, then, would be about 1.77 AU, i.e. just a bit too far away from the Sun to sustain water in liquid form. Venus, on the other hand, is too close to the Sun (see box below).

Kopparapu calculates that the Solar System’s habitable zone lies between 0.99 AU (92 million mi, 148 million km) and 1.70 AU (158 million mi, 254 million km) from the Sun. In other words, Earth is on the edge of runaway warming.

Image by Kopparapu et al. New calculations show that Earth is positioned on the edge of the habitable zone
(green-shaded region), boundaries of which are determined by the moist-greenhouse
(inner edge, higher flux values) and maximum greenhouse (outer edge, lower flux values)

Kopparapu says that if current IPCC temperature projections of a 4 degrees K (or Celsius) increase by the end of this century are correct, our descendants could start seeing the signatures of a moist greenhouse by 2100.

Kopparapu argues that once the atmosphere makes the transition to a moist greenhouse, the only option would be global geoengineering to reverse the process. In such a moist-greenhouse scenario, not only are the ozone layer and ice caps destroyed, but the oceans would begin evaporating into the atmosphere's upper stratosphere.

Venus' runaway greenhouse effect a warning for Earth by Sam Carana - first posted November 28, 2007, at: http://global-warming.gather.com/viewArticle.action?articleId=281474977189423 Venus was transformed from a haven for water to a fiery hell by an runaway greenhouse effect, concludes the European Space Agency (ESA), after studying data from the Venus Express, which has been orbiting Venus since April 2006. Venus today is a hellish place with surface temperatures of over 400°C (752°Fahrenheit), winds blowing at speeds of over 100 m/s (224 mph) and pressure a hundred times that on Earth, a pressure equivalent, on Earth, to being one km (0.62 miles) under the sea. Hakan Svedhem, ESA scientist and lead author of one of eight studies published on Wednesday in the British journal Nature, says that Earth and Venus have nearly the same mass, size and density, and have about the same amount of carbon dioxide. In the past, Venus was much more Earth-like and was partially covered with water, like oceans, the ESA scientists believe. How could a world so similar to Earth have turned into such a noxious and inhospitable place? The answer is planetary warming. At some point, atmospheric carbon triggered a runaway warming on Venus that boiled away the oceans. As water vapour is a greenhouse gas, this further trapped solar heat, causing the planet to heat up even more. So, more surface water evaporated, and eventually dissipated into space. It was a “positive feedback” -- a vicious circle of self-reinforcing warming which slowly dessicated the planet. “Eventually the oceans began to boil”, said David Grinspoon, a Venus Express interdisciplinary scientist from the Denver Museum of Nature and Science, Colorado, USA. “You wound up with what we call a runaway greenhouse effect”, Hakan Svedhem says. Venus Express found hydrogen and oxygen ions escaping in a two to one ratio, meaning that water vapor in the atmosphere the little that is left of what they believe were once oceans is still disappearing. While most of Earth's carbon store remained locked up in the soil, rocks and oceans, on Venus it went into the atmosphere, resulting in Venus' atmosphere now consisting of about 95% carbon dioxide. “Earth is moving along the curve that connects it to Venus”, warns Dmitry Titov, science coordinator of the Venus Express mission. References - Venus Express - European Space Agency (ESA) http://www.esa.int/SPECIALS/Venus_Express/SEMGK373R8F_0.html - Venus inferno due to 'runaway greenhouse effect', say scientists http://www.physorg.com/news115477239.html - Probe likens young Venus to Earth http://physicsworld.com/cws/article/news/32018 - European mission reports from Venus http://www.nature.com/nature/journal/v437/n7062/full/4371071a.html

References

- Habitable zones around main-sequence stars: new estimates

Ravi Kumar Kopparapu et al. 2013

http://iopscience.iop.org/0004-637X/765/2/131

- Habitable Zone - Wikipedia

http://en.wikipedia.org/wiki/Habitable_zone

- Earth is closer to the edge of Sun's habitable zone

http://physicsworld.com/cws/article/news/2013/mar/25/earth-is-closer-to-the-edge-of-suns-habitable-zone

- Updated model for identifying habitable zones around stars puts Earth on the edge

http://www.gizmag.com/habitable-zone/26051/

How much will temperatures rise?

Runaway Global Warming

If we take the NASA Annual Mean Land-Ocean Temperatures and draw a projection into the future, temperatures will quickly be 3 degrees Celsius higher than the base period (1951-1980), i.e. well before 2050, as illustrated on image 1. below. 

Image 1. Temperatures will be 3 degrees Celsius higher well before 2050

Above projection appears to be steeper than even the worst-case scenario pictured by the IPCC for years, such as on the image below.

Image 2. from IPCC 2001. Projections of globally averaged surface temperature 2000-2100 are shown for six SRES scenarios and IS92a using a model with average climate sensitivity. The grey region marked "several models all SRES envelope" shows the range of results from the full range of 35 SRES scenarios in addition to those from a range of models with different climate sensitivities. The temperature scale is departure from the 1990 value.

Could temperatures rise faster in future than what the IPCC anticipated in 2001? The answer must be yes! In 2007, the IPCC described that, even if greenhouse gas concentrations in the atmosphere were stabilized for 100 years at year 2000 values (B1), then we would still be committed to a further warming of 0.5°Celsius. This committed warming should not be confused with ‘unavoidable climate change’ over the next half century, which would be greater because forcing cannot be instantly stabilized. And of course, as it turned out, emissions have not been stabilized at 2000 values, but have in fact increased substantially.

As it turned out, the models used by the IPCC made all kinds of assumptions that didn't eventuate. But before deciding to instead settle for a relatively simple extrapolation of observed data, there are some issues that require a further look.  

As discussed in the earlier post Accelerated Arctic Warming, temperatures in the Arctic have been rising at a much faster pace than global temperatures, and if this accelerated rise continues, we can expect a 10 degrees Celsius rise in the Arctic before 2040, as illustrated by image 3. below.  

Image 3. Three kinds of warming - 2: Accelerated warming in the Arctic 

Such a temperature rise in the Arctic will undoubtedly lead to additional greenhouse gas emissions in the Arctic, of carbon dioxide, nitrous oxide and particularly methane, threatening to trigger runaway global warming. 

The image below, from the methane-hydrates blog, combines these three kinds of warming, showing global temperatures that soon catch up with accelerated Arctic warming, as heatwaves at high latitudes will cause wildfires, in particular in Siberia, where firestorms in peat-lands, tundras and forests could release huge amounts of emissions, including soot, much of which could settle on the Himalayan plateau, darkening the ice and snow and resulting in more local heat absorption. Rapid melt of glaciers will then cause flooding at first, followed by dramatic decreases in the flow of river water that up to a billion people now depend on for water supply and irrigation.

In other words, the situation looks much more dire than what most models make us believe; the more reason to adopt the climate plan that is also described at the post at the methane-hydrates blog.

Image 4. Three kinds of warming - 1, 2 and 3 

References

- IPCC (TAR) - Climate Change 2001: Synthesis Report

http://www.grida.no/publications/other/ipcc_tar/?src=/climate/ipcc_tar/vol4/english/figspm-10b.htm

- IPCC (AR4) - Climate Change 2007: Working Group I: The Physical Science Basis

http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch10s10-es-16-radiative-forcing.html#10-es-17-climate-change

- Accelerated Arctic Warming

http://arctic-news.blogspot.com/2013/01/accelerated-arctic-warming.html

- Methane hydrates

http://methane-hydrates.blogspot.com/2013/04/methane-hydrates.html