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Biofuels and oil from algae Trends Prof Yash
Pal THIS UNIVERSE |
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Biofuels and oil from algae
Though fossil fuel reserves are depleting and combustion is associated with the generation of many environmentally unfriendly end products (viz., CO2, NOx, SOx, soot and flyash) but still the combustion of fossil fuels for the time being seems to be an inevitable source of energy to meet the ever-expanding demand of energy hungry civilisation. Power plants and transport are responsible for huge quantities of greenhouse gas emissions as both still rely heavily on fossil fuels. Many energy intensive and costly technologies are well in use in dispensing these end products but there is a need to develop a cheap and energy-free process not only to control/dispense the end products of fossil fuel burning but if possible to convert them into some useful by products. The easiest way to eliminate gases particularly given off by coal-burning power plants is nature’s way, through photosynthesis. But industrial quantities of CO2 need industrial amounts of photosynthesis. Researchers are now hoping to marry the two together with an emerging technology that uses a bi-product of one to supply fuel to the other. At the heart of the technology is a cylinder full of algae, which can suck gaseous emissions from a power plant’s exhaust and convert it into biofuel thus a win-win on both sides it seems. Algae are single-cell plants that thrive in moist or wet environments, and through photosynthesis, consume NOx and CO2, and release clean air. That makes the microscopic plants very special, and potentially very useful, in reducing greenhouse gases. Algae are the fastest growing plants on earth. Algae are super rich in oil. The idea of algal photosynthesis to fight pollution is not new. U.S. Department of Energy (DOE) conducted a large-scale study several years ago which demonstrated that more than 300 species of algae were well suited to the task. However, implementation of such a process has always been hindered by logistics and cost considerations. Because photosynthesis efficiency is driven by complex cellular mechanisms that depend on having just the right exposure to light — not too much, not too little — past algal systems grew to be complex and ultimately too expensive for most industrial sites to contemplate. They either took the form of huge, shallow ponds with extensive pumping and distribution mechanisms, or conversely they developed into precisely engineered closed bioreactors with high manufacturing and maintenance costs. The algae use the available carbon dioxide and water to grow new algae, giving off pure oxygen and water vapour in the process. The process, called photomodulation, rotates the algae in and out of the sunlight, rather than bringing the sunlight to the algae. The organisms also absorb nitrogen oxide and sulfur dioxide. The algae use the CO2, along with sunlight and water, to produce sugars by photosynthesis, which are then metabolised into fatty oils and protein. As the algae grow and multiply, portions of the soup are continually withdrawn from each reactor and dried into cakes of concentrated algae. These are repeatedly washed with solvents to extract the algal oil which can then be converted into biodiesel through a routine process called transesterification, in which it is processed using ethanol and a catalyst. Enzymes are then used to convert starches from the remaining biomass into sugars, which are fermented by yeasts to produce ethanol. Algae reduce NOx day and night, regardless of weather or lighting conditions. The process is essentially an effect of the surface configuration of the algae cell walls. Even dead algae can provide significant NOx reduction, up to 70 percent. For centuries Algae has been used as manure. Algae can be used to make biodiesel and by some estimates can produce vastly superior amounts of oil, compared to terrestrial crops grown for the same purpose. It does not need fresh water or fertiliser. Algae can also be used to produce hydrogen. Algae are used in wastewater treatment facilities, reducing the need for more dangerous chemicals. Algae can be used to capture fertilisers in runoff from farms. If this algae is then harvested, it itself can be used as fertiliser. So far scientists are very much against genetic manipulation of algae for bioreactor project, because a large quantity of algae is going to be generated which can be put to some use. Current plans call for automatically hosing off and collecting the excess algae, which might be used as
biofuel. The writer is from Department of Physics, S.L.I.E.T., Longowal |
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Trends Energy storage is an unglamorous pillar of an expected revolution to clean up the world’s energy supply but will soon vie for investors’ attention with more alluring sources of energy like solar panels, manufacturers say. “It’s been in the background until now. It’s not sexy. It’s the enabler, not a source of energy,” said Tim Hennessy, chief executive of Canadian battery makers VRB Power, speaking on the sidelines of a “Clean Equity” technologies conference in Monaco. VRB will start mass production this year of a longer-lasting rival to the lead acid battery currently used to store energy for example produced by solar panel, Hennessy said. Low carbon-emitting renewable energy is in vogue, driven by fears over climate change, spiraling oil prices and fears over energy supply and security. While the supply of the wind and sun far exceeds humanity’s needs it doesn’t necessarily match the time when people need it: the sun may not be shining nor the wind blowing when we need to cook dinner or have a shower. Soaring production of solar panel and wind turbines is now spurring a race to develop the winning energy storage technologies which will drive the electric cars and appliances of the future. The race is heating up as manufacturers with entirely different solutions near the moment of commercial production.
— Reuters Solar probe freezing to death The Ulysses solar probe, after 17 years of studying the sun and solar system, is about to die by freezing to death, NASA and the European Space Agency said recently. The satellite had long outlasted the five-year mission it began in 1990, but it continued to transmit useful data on solar winds. More recently, its plutonium power source had slowly weakened and its fuel was freezing as the probe made a wide circle of the sun, traveling as far as Jupiter. In January, engineers tried a longshot maneuver to heat up the fuel. Instead, their effort backfired and hastened Ulysses’ death by several months. The $250 million probe was a joint European-NASA project. After being released from orbit by astronauts on the space shuttle Discovery in October 1990, Ulysses made nearly three full wide circles of the sun from above and below its poles. It also circled over Jupiter’s poles, logging about 6 billion miles overall. When the satellite recently started to fail, the probe had just finished examining the sun’s north pole for a third time. “This mission has rewritten textbooks,” said Arik Posner, NASA’s Ulysses program scientist. What made Ulysses unique and crucial to scientists was its orbit and perspective. It provided astronomers with a three-dimensional look at the sun and the rest of the solar system. Most of the planets line up along the same geometric plane generally around the middle of the sun and that’s where most of the space probes orbit, too. That three-dimensional data from Ulysses — not devised to take pictures — was important for scientists trying to figure out the solar wind. These winds blast away from the sun at 1 million miles per hour in all directions, said David McComas, a Ulysses scientist with the Southwest Research Institute in San Antonio. The solar wind is crucial because it protects Earth from deadly cosmic radiation, causes geomagnetic storms on Earth, and is responsible for the aurora borealis.
— AP |
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THIS UNIVERSE How do the neutrons remain uncharged even in the presence of positively charged protons in the nucleus of an atom? This is a beautiful question discovered by a class VIII student. It is true that neutrons and protons are together inside a nucleus. But your question is a little bit like wondering why the boys who are together with some girls in a class do not come out as girls? More seriously, it is true that protons and neutrons are similar in several respects. Their nuclear force is rather similar. But neutrons are not just uncharged protons. When they are free they do convert into protons. From energetic point of view this is allowed because a neutron has a slightly greater mass than the proton. But this does not happen instantaneously. Free neutrons have a lifetime of nearly 15 minutes. The process of conversion results into a proton, an electron and a neutral particle of nearly zero mass called the neutrino. This process does not occur when the neutron is bound in a stable nucleus. It is clear that you cannot just pull out an electron from a neutron and convert into a proton. This is not allowed. This statement might surprise you because we keep on pulling out electrons by applying voltage and make electric current flow. In fact you also pull out lot of electrons just by friction when you comb your hair during winter months, especially when the humidity is low. You must have noticed that your comb can pick up tiny bits of paper and you usually say that this is because of static electricity. The electrons in both these cases do not come out of neutrons in the nucleus; they are from amongst the more loosely bound cloud of electron of the atoms. Neutrons and protons are both endowed with the property of binding with a strong force, called the nuclear force. Electrons do not have this property and therefore they do not reside in the nucleus. Protons also carry a positive charge that is equal and opposite to the charge of an electron. Let us now try to build a few atomic nuclei. The first one is easy. Just a proton would do. Put an electron around it and you have the hydrogen atom. (You know that an atom has to be neutral). Let us try to proceed further. We try to put one more proton in the nucleus, hoping that the attractive nuclear force would keep the two protons together. But that does not work. Their positive charges push the two protons away from each other - repulsion of the two like charges is stronger than their nuclear attraction! Let us try to make a nucleus with one proton and one neutron. Hurrah, it works! We have created the nucleus of heavy hydrogen. This isotope of hydrogen is stable. Chemically it behaves like ordinary hydrogen. Water made with this hydrogen is called heavy water. Happy with this success we can try putting in yet another neutron in the nucleus. Now we have one proton and two neutrons together. We find that we do get another viable nucleus, but it is not stable; it decays with a half-life of about twelve years. This also is another form of hydrogen, since only one charge resides in the nucleus. This unstable form of hydrogen is called Tritium. Two protons and two neutrons together make a very stable structure. This is the nucleus of a helium atom. There is also another isotope of helium where the nucleus consists of two protons and only one neutron. This is called helium 3. One can proceed further and build the nuclei of heavier atoms. It is found that after a while stability is ensured only if the number of neutrons is greater than the number of protons. That is the only way the explosive increase of electrostatic repulsion of protons can be overcome. By the time we reach the nucleus of uranium, we have 92 protons and 146 neutrons. |
