Universidad Mayor in Santiago, Chile is experimenting with the use of plantation-grown prickly pear cactus for use as biofuel. They intend to establish plantations in the Atacama desert, a place that averages 0.004 inches of rain a year, mainly as fog from the Pacific Ocean.

Reporter Anatoly Kurmanaev of the Santiago Times sets the scene:

The driest place on earth, the Atacama Desert in northern Chile, wouldn’t seem an auspicious place for biofuel production.

Biotechnology experts, however, may have found a way to turn one of the desert’s only available plants, the cactus, into energy.

A US$500,000 pilot project in the Río Jorquera Valley in the Copiapó province aims to reduce Nopal cactus stems to high-energy dry briquettes that can be burned in coal-fired thermoelectric plants.

The five-acre experimental plantation will produce sufficient scientific data on cactus biomass production in arid conditions by the end of 2013, and will then begin supplying fuel to a small-scale onsite power station.

The project’s leader, Prof. Alexis Vega of Universidad Mayor’s Biotechnology Institute in Santiago, believes a pilot-scale plantation of 420 acres will be able to sustain 1.5 megawatts per hour (MW/h) of electricity generation.

At an estimated cost of US$112 per MW/h, cactus biofuel is competitive with fossil fuels at current global prices and is much cheaper than other sources of alternative energy in the region such as wind or solar.

“This is an opportunity to diversify the local economy by utilizing marginal soil—land which has little water and few agricultural alternatives,” said Vega.

The researchers hope to develop the plantation to a level where they can begin supplying large electrical utilities in northern Chile.

One of the advantages of the cactus plantations is their proximity to energy-hungry mining operations. Utilizing locally available sources of energy would reduce the need for costly energy shipments from the south, Vega explained.

“Four years ago, when we approached the big power distributors they told us no. Now the moment has arrived—they are keen to participate.”

A law passed in 2010 binds Chile to generate 10 percent of its electricity from renewable, non-conventional sources by 2024.

At present the figure stands at around five percent, and Vega believes the government’s support for alternative energy puts the nation well on course to meeting the target.

Apart from the environmental benefits, researchers believe the scheme also holds substantial economic potential.

Southern Atacama’s traditional crop has been the table grape, the profitability of which has fallen steadily in recent years due to growing competition from Peru and Argentina.

As cactuses require at most a third of the water used by a grape plantation of the same area, there are large potential savings for farmers, as well as stable year-round jobs.

“For the small declining indigenous communities of northern Chile this is a real development opportunity,” said Vega. “These people can stay on the land, produce fuel for their own use, and sell the surplus, instead of migrating to the cities where they will remain poor.”

According to a report from Universidad Mayor, the cactus can be used in two ways: 1) anaerobic bio-digestion can produce methane for use as a feedstock for electrical generation, much as we harvest methane from landfills here in Tucson; or 2) the prickly pear pads can be dehydrated using solar energy, then pelleted and used as a co-combustion fuel in coal-fired plants. The cactus plantations will have to be irrigated and fertilized to allow a harvest every six months. An added benefit, if the project proves feasible, is that this biofuel is produced from a non-food crop and will provide year-round jobs rather than seasonal employment common to most crops. The goal of the project is to produce at least the equivalent of 40 tons dry matter per hectare per year which they deem competitive with other biofuels.

Some people must think that humans are not part of nature according to two comments to my post: Carbon Dioxide and the Greenhouse Effect . The comments alleged: “Human carbon emissions are not a part of the natural carbon cycle.” and “We are now releasing huge amounts of fossil carbon too rapidly for natural processes to adjust.” Both claim that human carbon dioxide emissions upset “the balance of nature.” This belief reflects a misunderstanding of what “balance” really is. Nature is never really “in balance” or static, it is always seeking equilibrium between forces that upset the status quo.

This misunderstanding is reflected in one of the comments: “The natural carbon cycle involves the production/consumption of carbon. Humans do exhale – but energy production involves humans using historic carbon from earlier carbon cycles that are not contemporary. It isn’t part of a ‘natural’ carbon cycle.”

Tell me, how can nature distinguish between a carbon dioxide molecule produced by someone burning wood in a fireplace versus carbon dioxide resulting from burning wood in a forest fire? How can nature distinguish between a molecule of carbon dioxide produced by burning coal to generate electricity versus coal burning in a seam due to natural spontaneous combustion? Yes, that does happen. So much for “historic carbon.”

There are actually two carbon cycles. The geologic carbon cycle stores carbon in limestone, dolomite, petroleum, and coal deposits. Carbon dioxide from the atmosphere is used up during the weathering of silicate rocks, a process that speeds up with increasing temperature or increasing carbon dioxide, thereby forming a negative feedback or thermostat. It takes millions of years, usually, for this carbon to cycle back into the biosphere. Volcanoes recycle carbonate rocks and emit 200 million metric tons of carbon dioxide per year according to the U.S. Geological Survey. There are also carbon dioxide gas seeps. Carbon dioxide is also produced from metamorphism of carbonate rocks.

The biologic carbon cycle is exchange of carbon dioxide between the atmosphere, biosphere, and ocean as shown in the graphic below. The biologic process involves photosynthesis, respiration, ocean absorption, and biological use of carbonates to form shells and other structures. Human emissions are part of these natural cycles.

The relative amount of carbon in each “sink” is shown in the table below.

Notice that the amount of carbon stored as fossil fuel deposits is just one-tenth of that stored in the oceans, and the ocean store in continually in flux. The ocean is also the connection between the geologic carbon cycle and the biologic carbon cycle. As the amount of carbon dioxide in the atmosphere increases, ocean uptake also increases. The carbon dioxide is stored not only as dissolved gas, but also as carbonate ions which are sequestered by marine life and the production of limestone and dolomite deposits.

There is another complication. Some carbon is missing. When calculating the carbon flux, i.e., the emissions from known sources versus carbon sequestration by known sinks, there should be more carbon dioxide in the atmosphere than there is. So, either there is an unknown process taking up carbon dioxide or a known process is working faster than we thought (seeking equilibrium).

There is some observational evidence for that last process. We see that terrestrial plant life has increased its net primary productivity by growing more robustly and by making better use of nitrogen in the soil. (See here ) There are also new studies showing that small marine creatures, such as Thaliacea, are depositing more carbon into the geologic sink than previously realized.

Perhaps we still don’t know as much about the carbon cycle as we thought.

To put things in perspective, according to data from the Energy Information Administration, based on data derived from the IPCC, human carbon dioxide emissions represent about 3% of the total carbon dioxide flux, and 98.5% of that is reabsorbed in the biologic carbon cycle. (Source )

Slightly off subject but important: A new paper in Geophysical Research Abstracts (Vol. 13, EGU2011-4505-1, 2011) based on detailed spectrographic analysis of the atmosphere found that because the absorbance of water vapor overlaps the frequencies of long wave radiation that are absorbed by carbon dioxide and methane, the effective sensitivity of carbon dioxide and methane as greenhouse gases is only one-seven that claimed by the IPCC and used in climate models.

That makes our emissions from burning fossil fuels of even less concern.

The “greenhouse effect,” very simplified, is this: solar radiation penetrates the atmosphere and warms the surface of the earth. The earth’s surface radiates thermal energy (infrared radiation) back into space. Some of this radiation is absorbed and re-radiated back to the surface and into space by clouds, water vapor, methane, carbon dioxide, and other gases. Water vapor is the principle greenhouse gas; the others are minor players. Without the greenhouse effect the planet would be an iceball, about 34 C colder than it is. The term “greenhouse effect” with respect to the atmosphere is an unfortunate usage because it is misleading. The interior of a real greenhouse (or your automobile parked with windows closed and left in the sun) heats up because there is a physical barrier to convective heat loss. There is no such physical barrier in the atmosphere.

Carbon dioxide is a “greenhouse” gas, so let’s examine its theoretical and actual effect on temperature.

Even the IPCC agrees that the hypothetical capacity of carbon dioxide to change temperature is given by the formula: T_c = áln(C₂/C₁), where T_c is the change in temperature in degrees Centigrade and the term ln(C₂/C₁) is the natural logarithm of the CO₂ concentration at time two divided by the concentration at time one. The constant á (alpha) is sometimes called the sensitivity and its value is subject to debate. This relationship was proposed by Svante August Arrhenius, a physicist and chemist, around 1896. This logarithmic formula produces a graph in the form shown at the left. This shows that as the concentration of carbon dioxide increases, its effects have less and less influence. This graph is the pure theoretical capacity of carbon dioxide to warm the atmosphere in absence of any confounding feedbacks. The different curves represent different values of alpha.

  The reason it works this way is because carbon dioxide can absorb only a few specific wavelengths of thermal radiation. The current concentration of carbon dioxide has absorbed almost all available radiation in those wavelengths so there is little left for additional carbon dioxide to absorb. Notice too, that water vapor absorbs many of the same wavelengths of thermal radiation. Also notice that in a certain part of the spectrum there is an open window of no absorption.

We see, therefore, that increasing levels of carbon dioxide in the atmosphere will have a decreasing hypothetical effect on temperature. That is also why our proposed attempts to decrease atmospheric carbon dioxide will have almost no effect on temperature.

The IPCC says that warming will produce more water vapor which will enhance greenhouse warming, a positive feedback. All their climate models are based on this assumption. Sounds reasonable except in the real world, it doesn’t happen. Increased water vapor produces more clouds which block the sun thereby inducing cooling, a negative feedback.

Dr. Roy Spencer explains here why doubling the carbon dioxide concentration in the atmosphere will add only 3% to Earth’s greenhouse effect. Spencer has further discussion here in which he says, “that about 50% of the surface warming influence of greenhouse gases has been short-circuited by the cooling effects of weather.”

The atmosphere is not static; we have weather which tends to dissipate heat into space. According to real world measurements, the negative feedbacks overwhelm the theoretical positive feedback posed by the IPCC.

An example of negative feedbacks:

In 2001, a paper by M.I.T. researchers proposed that warming dissipated high-altitude cirrus clouds which had the effect of dumping heat into space, thereby helping to regulate earth’s temperature. This paper was controversial because it went against the orthodoxy of global warming and there were many detractors. However, in 2007 researchers from the University of Alabama, using NASA satellite data found evidence to support the theory. In 2009, the original M.I.T. researchers, using National Centers for Environmental Prediction’s 16-year (1985-1999) monthly record of sea surface temperature, together with corresponding radiation data from the Earth Radiation Budget Experiment, found more real world evidence in support of the theory (see PDF). It might be noted that 11 major climate models used by the IPCC assume positive feedback, but real world data shows a temperature-moderating negative feedback. However, the role of clouds is still poorly-understood and more real-world data is needed.

What happens on other planets:

Venus:

Venus has a surface temperature of about 900 F and an atmosphere composed of 96% carbon dioxide. The temperature is the same from equator to poles, from day to night (Venus rotates on its axis in 2,802 hours rather than 24 hours). Venus is often touted as the extreme example of run-away greenhouse warming. But, there is almost no greenhouse warming on Venus because little, if any, direct sunlight gets to the surface. The atmosphere is too thick. In 1975, the Russian Venus lander Venera 9 measured clouds that were 30–40 km thick with bases at 30–35 km altitude. The surface air pressure on Venus is about 92 times greater than that on Earth. The high pressure alone can explain most of the high surface temperature. Although Venus gets almost twice the solar irradiation of Earth, Venus’ high albedo reflects back 65% of the sunlight.

 Venus has almost no water vapor in the atmosphere (about 0.002%), and therefore lacks the major greenhouse gas that Earth has.

Mars:

Mars has an atmosphere composed of 95% carbon dioxide and only a trace of water. Its atmosphere is very thin. Its surface pressure is about 2% that of Earth. The temperatures on the two Viking landers, measured at 1.5 meters above the surface, range from + 1° F, ( -17.2° C) to -178° F (-107° C). However, the temperature of the surface at the winter polar caps drop to -225° F, (-143° C) while the warmest soil occasionally reaches +81° F (27° C) as estimated from Viking Orbiter Infrared Thermal Mapper (NASA data). Again, no water vapor, no greenhouse effect.

***

The greenhouse model is a simplified story that helps explain how our atmosphere works. However, the real world is very complicated and still not fully understood. Even global warming alarmist James Hansen of NASA’s Goddard Institute for Space Studies, had this to say: “The forcings that drive long-term climate change are not known with an accuracy sufficient to define future climate change.” — James Hansen, “Climate forcings in the Industrial era”, PNAS, Vol. 95, Issue 22, 12753-12758, October 27, 1998.

And even the IPCC once admitted, “In climate research and modeling, we should recognize that we are dealing with a coupled non-linear chaotic system, and therefore that the prediction of a specific future climate state is not possible.” — Final chapter, Draft TAR 2000 (Third Assessment Report), IPCC.

Human carbon dioxide emissions are 3% to 5% of total carbon dioxide emissions into the atmosphere, and about 98% of all carbon dioxide emissions are reabsorbed through the carbon cycle. (Source )

Although Earth’s atmosphere does have a “greenhouse effect” and carbon dioxide does have a limited hypothetical capacity to warm the atmosphere, there is no physical evidence showing that human carbon dioxide emissions actually produce any significant warming. If you disagree with that statement, then produce some physical evidence to refute it.

UPDATE March 3, 2011: A new paper in Geophysical Research Abstracts (Vol. 13, EGU2011-4505-1, 2011) reports that detailed spectrographic analysis found that because of the overlap absorbance of the much more abundant water vapor for long wave radiation, the effective sensitivity of carbon dioxide and methane as greenhouse gases is only one-seven that claimed by the IPCC and used in climate models.