The naturally occurring mineral serpentine sequesters carbon dioxide very slowly over eons. Some Penn State researchers have found that by dissolving serpentine in sulfuric acid they can produce compounds that will very rapidly bind to carbon dioxide.
The metamorphic mineral serpentine -- or magnesium silicate hydroxide -- is composed of magnesium, silicon and oxygen and is plentiful. He researchers used material from the Cedar Hills quarry on the Pennsylvania/ Maryland border for this study, but the mineral is available in large quantities in many places. The U.S. deposits of the minerals that can be used for this process – serpentine and ovivine – can sequester all the carbon dioxide emissions produced from fossil fuels.
"Previous researchers investigating serpentine for use in sequestering carbon dioxide have crushed serpentine very finely, to sizes smaller than beach sand, but, even at these small sizes, it takes high temperatures to speed up the reaction, "says Maroto-Valer. "With our method, we do not need to crush it that fine and we do not need high temperatures. In fact, the reaction gives off heat. Our method is much less energy expensive."
They aren't done developing this method to the point of being practically useful. Also, there is no big push in the United States at this point to reduce carbon dioxide emissions. Still, this could turn out to be a useful technique if global warming is eventually proven to be a serious problem.
They crush serpentine, dissolve it in sulfuric acid, treat part of it with sodium hydroxide, and the result will react with carbon dioxide to produce magnesium carbonate or magnasite.
The researchers, who also include John M. Andresen, director of the Consortium for Premium Carbon Products from Coal (CPCPC), the Energy Institute; Yinzhi Zhang, post doctoral fellow, the Energy Institute; Matthew E. Kuchta, graduate student in geo-environmental engineering, all at Penn State; and Dan J. Fauth, U.S. Department of Energy's National Energy Laboratory in Pittsburgh, dissolved the crushed serpentine in sulfuric acid.
When serpentine dissolves in sulfuric acid, the silicon in the mineral becomes silicon dioxide, or sand, and falls to the bottom, while the magnesium becomes magnesium sulfate. Treating some of this magnesium sulfate with sodium hydroxide also creates some magnesium hydroxide. The researchers were able to convert large amounts of the serpentine's magnesium to these chemicals providing large surface areas for reactions to occur in solution at room temperature.
Carbon dioxide passed through the solution of magnesium sulfate and magnesium hydroxide converts both to magnesium carbonate or magnesite, which becomes a solid and falls to the bottom. This solid can be used to manufacture construction blocks and there is also a small market for hydrated magnesium carbonate in the cosmetics industry. The silicon dioxide can be used to remove sulfur dioxide from the flue gases, which can subsequently be converted to sulfuric acid to use in the first part of the process.
"The high surface area of the silicon dioxide makes it a natural sorbent for capturing more carbon dioxide and sulfur dioxide," says Maroto-Valer.
Suppose coal can be made to burn extremely cleanly without even generating carbon dioxide emissions. Add in future advances in battery technology that make batteries light enough and cheap enough to be used in electric cars. Then at some point we might burn coal to supply electricity to charge batteries in electric cars.
Some scientists are questioning the viability of ocean iron seeding as a means to sequester carbon from atmospheric carbon dioxide. (The Scientist requires free registration - an excellent publication that is worth the trouble to sign up)
The idea can be traced back to a Woods Hole Oceanographic Institution meeting in 1985, when John Martin, then director of the Moss Landing Marine Laboratory, boasted: "Give me half a tanker of iron and I'll give you an ice age." Martin's general hypothesis that iron seeding would create a photosynthetic bloom proved correct, although the idea has turned out to be far less economical than he expected. The breakeven point for sequestration programs is $10 per ton of carbon dioxide; models based on the iron-seeding experiments still put the cost at $100 or more. Many scientists involved in iron-seeding projects as well as those observing them from afar say that iron seeding for purposeful carbon sequestration just doesn't work. "In the beginning, the assumptions were that for every atom of iron, we could sink 500,000 atoms of carbon," says Ken Caldeira, an ocean carbon-cycle scientist at Lawrence Livermore National Laboratory in California, who helped to create computer simulations. Those estimates have since been revised downwards by hundreds of orders of magnitude, he says.
The article quotes a variety of scientists on whether the latest Southern Ocean Iron Fertilization Experiment (SOFeX) provides good or bad news for the prospect of iron fertilization as a way to increase photosynthesis by marine plant organisms as a way to cheaply remove carbon dioxide from the atmosphere. Some scientists still hold that it is the cheapest method to remove atmospheric carbon dioxide found to date. Read the full article if the debate interests you. I lack sufficient knowledge to render any sort of opinion on the subject.
Also see my previous post on the SoFEX results that links to more optimistic assessements of the experiment's results: Iron Enriching Southern Ocean Pulls Carbon Dioxide From Atmosphere.
Rattan Lau (another page of his here), director of the Ohio State University Carbon Management and Sequestration Center, argues that no-till farming could pull a substantial portion of carbon out of the atmosphere as an anti-global warming strategy.
Traditional plowing, or tilling, turns over the top layer of soil. Farmers use it for, among other reasons, to get rid of weeds, make it easier to use fertilizers and pesticides and to plant crops. Tilling also enriches the soil as it hastens the decomposition of crop residue, weeds and other organic matter.
Still, the benefits of switching to no-till farming practices outweigh those of traditional planting.
Since the mechanization of agriculture began a few hundred years ago, scientists estimate that some 78 billion metric tons – more than 171 trillion pounds – of carbon once trapped in the soil have been lost to the atmosphere in the form of CO2.
Lal and his colleagues estimate that no-till farming is practiced on only 5 percent of all the world's cultivated cropland. Farmers in the United States use no-till methods on 37 percent of the nation's cropland, which results in saving an estimated 60 million metric tons of soil CO2 annually.
"If every farmer who grows crops in the United States would use no-till and adopt management practices such as crop rotation and planting cover crops, we could sequester about 300 million tons of soil carbon each year," said Lal, who is also a professor of soil science at Ohio State.
"Each year, 6 billion tons of carbon is released into the planet's atmosphere as fossil fuels are burned, and plants can absorb 20 times that amount in that period of time," he said. "The problem is that as organisms decompose and plants breathe, CO2 returns to the atmosphere. None of it accumulates in the soil."
Out of that 6 billion tons of carbon that is released into the atmosphere the United States probably accounts for approximately a quarter since the US accounts for about a quarter of all energy use. Those are rough figures. But compare that approximately 1.5 billion tons released with the 300 million tons Lau says we could capture in the soil. About 20% of our current carbon release could be captured in the soil with changed farming practices. Of course, as population and the per capita GDP grow energy consumption will grow. The amount of carbon captured by changed farming practices would likely not increase along with the population and energy consumption increases.
Keep in mind that we may not want to reverse all the carbon dioxide increase caused by farming and the burning of fossil fuels. First of all, release of carbon dioxide caused by the human development of farming may already have prevented onset of an ice age. Also, higher carbon dioxide appears to be allowing plants to grow into the Negev Desert and other deserts. We may be able to genetically engineer crop plants to grow faster in the presence of higher atmospheric carbon dioxide and those plants may be more drought resistant.
Still, some carbon sequestration may eventually become desirable and changing of farming practices might be a cheap way to accomplish it. A friend points out that sequestration in soil even has the advantage over deep ocean sequestration in that the soil carbon is more easily accessible should we need it again in the much longer term to use as a warming gas. Given that the interglacial warming periods like the one we are living in now are the exceptions to the average colder periods that have characterized Earth's history keeping carbon accessible seems prudent.
On the other hand, for planet warming we could make a small amount of carbon go a much longer way. Methane is a more potent warming gas than carbon dioxide. If thousands of years from now it ever became necessary to release hot house warming gasses into the atmosphere we could run nuclear fusion power plants to generate power to reduce carbon with hydrogen to produce methane. Then we could release the methane gas into the atmosphere to have it serve as a warming gas.
Also see my previous post Iron Enriching Southern Ocean Pulls Carbon Dioxide From Atmosphere.
Salting the Southern Ocean with iron results in increased growth of phytoplankton that take carbon dioxide from the atmosphere and extract the carbon into a form that eventually sinks deep into the ocean.
A remarkable expedition to the waters of Antarctica reveals that iron supply to the Southern Ocean may have controlled Earth's climate during past ice ages. A multi-institutional group of scientists, led by Dr. Kenneth Coale of Moss Landing Marine Laboratories (MLML) and Dr. Ken Johnson of the Monterey Bay Aquarium Research Institute (MBARI), fertilized two key areas of the Southern Ocean with trace amounts of iron. Their goal was to observe the growth and fate of microscopic marine plants (phytoplankton) under iron-enriched conditions, which are thought to have occurred in the Southern Ocean during past ice ages. They report the results of these important field experiments (known as SOFeX, for Southern Ocean Iron Enrichment Experiments) in the April 16, 2004 issue of Science.
Previous studies have suggested that during the last four ice ages, the Southern Ocean had large phytoplankton populations and received large amounts of iron-rich dust, possibly blown out to sea from expanding desert areas. In order to simulate such ice-age conditions, the SOFeX scientists added iron to surface waters in two square patches, each 15 kilometers on a side, so that concentrations of this micronutrient reached about 50 parts per trillion. This concentration, though low by terrestrial standards, represented a 100-fold increase over ambient conditions, and triggered massive phytoplankton blooms at both locations. These blooms covered thousands of square kilometers, and were visible in satellite images of the area.
Each of these blooms consumed over 30,000 tons of carbon dioxide, an important greenhouse gas. Of particular interest to the scientists was whether this carbon dioxide would be returned to the atmosphere or would sink into deep waters as the phytoplankton died or were consumed by grazers. Observations by Dr. Ken Buesseler of Woods Hole Oceanographic Institution and Dr. Jim Bishop of Lawrence Berkeley National Laboratories (reported separately in the same issue of Science) indicate that much of the carbon sank to hundreds of meters below the surface. When extrapolated over large portions of the Southern Ocean, this finding suggests that iron fertilization could cause billions of tons of carbon to be removed from the atmosphere each year. Removal of this much carbon dioxide from the atmosphere could have helped cool the Earth during ice ages. Similarly, it has been suggested that humans might be able to slow global warming by removing carbon dioxide from the atmosphere through a massive ocean fertilization program.
This report provides support for the idea that dissolving large quantites of iron into the ocean could be used as a technique to slow or perhaps even reverse the build-up of carbon dioxide in the atmosphere. The report of the Woods Hole scientists is particularly interesting because it suggests that some of the carbon pulled from the atmosphere by ocean iron fertilization will stay out of the atmosphere for long enough to be worthwhile as an approach for preventing global warming.
The controversial idea of fertilizing the ocean with iron to remove carbon dioxide from the atmosphere gained momentum in the 1980s. Climate and ocean scientists, as well as ocean entrepreneurs and venture capitalists, saw potential for a low-cost method for reducing greenhouse gases and possibly enhancing fisheries. Plankton take up carbon in surface waters during photosynthesis, creating a bloom that other animals feed upon. Carbon from the plankton is integrated into the waste products from these animals and other particles, and settles to the seafloor as "marine snow" in a process called the "biological pump." Iron added to the ocean surface increases the plankton production, so in theory fertilizing the ocean with iron would mean more carbon would be removed from surface waters to the deep ocean. Once in the deep ocean, the carbon would be "sequestered" or isolated in deep waters for centuries. The oceans already remove about one third of the carbon dioxide released each year due to human activities, so enhancing this ocean sink could in theory help control atmospheric carbon dioxide levels and thus regulate climate.
However; estimates have been produced, suggesting only US$1-5 per tonne of carbon fixed. This compares very well with US$50-200 for other proposed sinks, so both commercial and political interest is thus high.
A controversial report by the National Academy of Sciences in 1992 looked at iron fertilization, among other geoengineering options. Although the NAS noted some caveats, it concluded that iron fertilization does have one attractive feature: a relatively cheap price tag. Running 360 ships full-time to fertilize 46 million square kilometers of ocean would cost somewhere between $10 billion and $110 billion a year.
Understanding of the impact on greenhouse gas balances through ocean fertilisation by the addition of iron or nutrients, such as nitrates and phosphates, is still limited (Annex B). With regard to iron fertilisation, there are substantial uncertainties about the overall response of the Southern Ocean ecosystem, and it is possible fertilisation could lead to increased emissions of other greenhouse gases, nitrous oxide and methane, significantly offsetting any increased uptake of carbon dioxide. Estimated costs of ocean fertilisation are highly uncertain. One source estimates are £3 to £37/tC but this may be rather optimistic due to uncertainties over the effectiveness of the process. The other option, ocean fertilisation by nutrients appears to be even less practical than that for iron. Costs are also uncertain but are likely to be higher at £30 to £120/tC.
But those estimates will become more precise as additional research work more accurately measures how much of the carbon fixed by ocean plants ends up sinking into the ocean depths.
The ferilization of oceans with iron would need to be done continuously to maintain a continued rate of extraction of carbon from the atmosphere to counteract carbon dioxide emissions from fossil fuel burning. Cessation of seeding would very quickly lead to a return to lower levels of plankton.
Projections from this experiment indicate that if the polar oceans were completely seeded in such a fashion, atmospheric CO2 would decrease by about 10%. This would substantially mitigate the greenhouse effect caused by CO2. Such plankton growth has other benefits as well. One potential benefit may be that the increase in plankton would lead to an increase in the populations of other ocean fauna, such as whales and dolphins, that feed on plankton. Another benefit, again, is that it is relatively inexpensive. A continual iron-seeding program would cost only about $10 billion a year. Yet another benefit is that plankton growth stops about a week after seeding, so if the plankton were determined to have a detrimental effect, the effort could be quickly disbanded.
But why store carbon in the oceans?
Faced with the stark reality, even the International Panel on Climate Change has admitted that we may have to consider what it calls ‘carbon management strategies’ to complement reductions in greenhouse gas emissions. One option is to store the excess carbon on land; this is already being done in deep geological formations, abandoned mines and the like.
But it is the oceans that have the greatest natural capacity to absorb and store carbon. On an annual basis, the surface of the ocean absorbs about 30% of the carbon in the atmosphere, less during El Niño years. But over very long timescales, of thousands of years, as much as 85% is absorbed by the oceans. The ocean contains an estimated 40,000 billion tons of carbon, as compared to 750 billion tons in the atmosphere and about 2200 billion tons on land. This means that, were we to take all the atmospheric CO2 and put it in the deep ocean, the concentration of CO2 in the ocean would change by less than 2%.
Iron ocean fertilization could be a bone for fish growth as the fish ate away at the much larger quantities of plankton. So part of the cost of this proposal might be paid for in larger fish catches. If a property rights system could be worked out for the fertilized ocean fisheries then a portion of the sales of harvested fish could go toward paying for the ocean fertilization. Though a carbon tax on all oil, natural gas, and coal extraction could be levied as well.
Lehigh University environmental engineer Wei-xian Zhang has developed techniques to use iron nanoparticles to destroy dangerous organic compounds in soil and to neutralize toxic heavy metals in soil.
Iron's cleansing power stems from the simple fact that it rusts, or oxidizes, explains Zhang. Ordinarily, of course, the only result is the familiar patina of brick-red iron oxide. But when metallic iron oxidizes in the presence of contaminants such as trichloroethene, carbon tetrachloride, dioxins, or PCBs, he says, these organic molecules get caught up in the reactions and broken down into simple carbon compounds that are far less toxic.
Likewise with dangerous heavy metals such as lead, nickel, mercury, or even uranium, says Zhang: The oxidizing iron will reduce these metals to an insoluble form that tends to stay locked in the soil, rather than spreading through the food chain. And, iron itself has no known toxic effect--just as well, considering the element is abundant in rocks, soil, water, and just about everything else on the planet. Indeed, says Zhang, for all those reasons, many companies now use a relatively coarse form of metallic iron powder to purify their industrial wastes before releasing them into the environment.
Unfortunately, says Zhang, these industrial reactors aren't much help with the pollutants that have already seeped into the soil and water. That's the beauty of the nanoscale iron particles. Not only are they some 10 to 1000 times more reactive than conventional iron powders, because their smaller size collectively gives them a much larger surface area, but they can be suspended in a slurry and pumped straight into the heart of a contaminated site like an industrial-scale hypodermic injection. Once there, the particles will flow along with the groundwater to work their decontamination magic in place--a vastly cheaper proposition than digging out the soil and treating it shovelful by shovelful, which is how the worst of the Superfund sites are typically handled today.
In that sense, says Zhang, nanoscale iron is similar to in situ biological treatments that use specialized bacteria to metabolize the toxins. But unlike bacteria, he says, the iron particles aren't affected by soil acidity, temperature, or nutrient levels. Moreover, because the nanoparticles are between 1 and 100 nanometers in diameter, which is about ten to a thousand times smaller than most bacteria, the tiny iron crystals can actually slip in between soil particles and avoid getting trapped.
Laboratory and field tests have confirmed that treatment with nanoscale iron particles can drastically lower contaminant levels around the injection well within a day or two, and will all but eliminate them within a few weeks--reducing them so far that the formerly polluted site will now meet federal groundwater quality standards. The tests also show that the nanoscale iron will remain active in the soil for 6 to 8 weeks, says Zhang, or until what's left of it dissolves in the groundwater. And after that, of course, it will be essentially undetectable against the much higher background of naturally occurring iron.
Finally, says Zhang, the cost of the nanoscale iron treatments is not nearly as big a barrier as it was in 1995, when he and his colleagues first developed a chemical route for making the particles. Then the nanoscale iron cost about $500 a kilogram; now, it's more like $40 to $50 per kilogram. (Decontaminating an area of about 100 square meters using a single injection well requires 11.2 kilograms.)
United States federal "Superfund" clean-up costs for polluted sites run over $1 billion per year and additional money is spent by state governments and private interests. Other countries face similar problems. Superfund costs are expected to continue for years to come. This technique holds the promise of much lower cost and even more effective clean-up of polluted sites.
What would be more exciting and potentially much more beneficial for human health is a way to clean up organic pollutants that concentrate in fish. In particular, I'd love to see a nanotech solution to the problem of PCB build-up in farmed salmon.
Seven of ten farmed salmon purchased at grocery stores in Washington DC, San Francisco, and Portland, Oregon were contaminated with polychlorinated biphenyls (PCBs) at levels that raise health concerns, according to independent laboratory tests commissioned by Environmental Working Group.
These first-ever tests of farmed salmon from U.S. grocery stores show that farmed salmon are likely the most PCB-contaminated protein source in the U.S. food supply. On average farmed salmon have 16 times the dioxin-like PCBs found in wild salmon, 4 times the levels in beef, and 3.4 times the dioxin-like PCBs found in other seafood. The levels found in these tests track previous studies of farmed salmon contamination by scientists from Canada, Ireland, and the U.K. In total, these studies support the conclusion that American consumers nationwide are exposed to elevated PCB levels by eating farmed salmon.
The problem is coming from their food. I'm guessing that iron nanoparticles would be both too expensive and too generally destructive if applied to the feedstock used for farmed salmon. Though the PCB concentration problem may even be a problem for some wild Sockeye salmon.
The farmed fish industry needs to grow because ocean fish are being depleted even as the demand for fish looks set to grow enormously as the health benefits of omega-3 fatty acids become more generally known. As fish go salmon is otherwise an attractive choice because salmon are an excellent omega-3 fatty acid source and salmon do not appear to concentrate mercury. So a cheap way to eliminate PCBs from farmed salmon feedstock would be great.
The problem is bioaccumulation - the build-up of contaminants in creatures at the top of the food chain. The North Pacific contains about 1 nanogram of PCBs per litre. By the time the average salmon has finished bulking up for its journey, its fat contains about 160 micrograms, Blais and co-workers report.
Incredibly low concentrations of a pollutant in the environment can be concentrated enormously by the food chain.
Atmospheric carbon dioxide is rising due to the large scale burning of coal, oil, natural gas, and other fossil fuels. This is creating fears of global warming. However, if a new report from Israel is correct high atmospheric CO2 will cause forests to expand into arid deserts.
Rehovot, Israel — May 8, 2003 — Missing: around 7 billion tons of carbon dioxide (CO2), the main greenhouse gas charged with global warming. Every year, industry releases about 22 billion tons of carbon dioxide into the atmosphere. And every year, when scientists measure the rise of carbon dioxide in the atmosphere, it doesn’t add up – about half goes missing. Figuring in the amount that could be soaked up by oceans, some 7 billion tons still remain unaccounted for. Now, a study conducted at the edge of Israel’s Negev Desert has come up with what might be a piece of the puzzle.
A group of scientists headed by Prof. Dan Yakir of the Weizmann Institute’s Environmental Sciences and Energy Department found that the Yatir forest, planted at the edge of the Negev Desert 35 years ago, is expanding at an unexpected rate. The findings, published in the current issue of Global Change Biology, suggest that forests in other parts of the globe could also be expanding into arid lands, absorbing carbon dioxide in the process.
The Negev research station is the most arid site in a worldwide network (FluxNet) established by scientists to investigate carbon dioxide absorption by plants.
The Weizmann team found, to its surprise, that the Yatir forest is a substantial “sink” (CO2-absorbing site): its absorbing efficiency is similar to that of many of its counterparts in more fertile lands. These results were unexpected since forests in dry regions are considered to develop very slowly, if at all, and thus are not expected to soak up much carbon dioxide (the more rapidly the forest develops the more carbon dioxide it needs, since carbon dioxide drives the production of sugars). However, the Yatir forest is growing at a relatively quick pace, and is even expanding further into the desert.
Why would a forest grow so well on arid land, countering all expectations (“It wouldn’t have even been planted there had scientists been consulted,” says Yakir)? The answer, the team suggests, might be found in the way plants address one of their eternal dilemmas. Plants need carbon dioxide for photosynthesis, which leads to the production of sugars. But to obtain it, they must open pores in their leaves and consequently lose large quantities of water to evaporation. The plant must decide which it needs more: water or carbon dioxide. Yakir suggests that the 30 percent increase of atmospheric carbon dioxide since the start of the industrial revolution eases the plant’s dilemma. Under such conditions, the plant doesn’t have to fully open the pores for carbon dioxide to seep in – a relatively small opening is sufficient. Consequently, less water escapes the plant’s pores. This efficient water preservation technique keeps moisture in the ground, allowing forests to grow in areas that previously were too dry.
The scientists hope the study will help identify new arable lands and counter desertification trends in vulnerable regions.
The findings could provide insights into the “missing carbon dioxide” riddle, uncovering an unexpected type of sink. Deciphering the atmospheric carbon dioxide riddle is critical since the rise in the concentrations of this greenhouse gas is suspected of driving global warming and its resulting climate changes. Tracking down carbon dioxide sinks could help scientists better assess how long such absorption might continue and lead to the development of efficient methods to take up carbon dioxide.
I am of the view that the fears of global warming are overblown because within a few decades technological advances in many fields will make photovoltaics and other renewable energy sources much cheaper than they are now. Once nanotechnological manufacturing methods become cheap then all houses and other structures will have photovoltaic siding and roofs and many other structures. Computers will be so many orders of magnitude faster 20, 30, and 40 years from now that they will be able to speed up the rate of scientific experimentation and engineering design by orders of magnitude by doing simulation experiments to find better designs. This will greatly speed the discovery of processes for making cheap renewable replacements for fossil fuels. Therefore projections about CO2 levels 50 or 100 years hence based on current fossil fuel demand trends are hopelessly naive.
This latest report suggests that the rising CO2 levels of the next few decades will provide some benefits to humanity. When renewable replacements for fossil fuels become cost competitive there may well be a debate at that point as to whether we should continue burning fossil fuels at a rate fast enough to maintain CO2 at a level that will support the continued spread of forests into deserts.
Also, it will become possible to genetically engineer crop plants to grow faster and with less irrigation in a high CO2 environment. It seems reasonable to expect that crop plants will be genetically engineered to be optimized for higher CO2 environments. Among the benefits of such optimization would be a reduced need for irrigation and more rapid plant growth. As a consequence of this it would not be at all surprising if 30 or 40 years from now the agricultural industry becomes a major source of political support for the continued burning of fossil fuels.