Liquid coal for cars 'dirtier' than petrol

Some alternative vehicle fuels such as liquid coal can cause more harmful greenhouse gas emissions than petrol or diesel, scientists warn.

"Liquid coal, for example, can produce 80% more global warming pollution than [petrol]," says the US non-profit environmental group, the Union of Concerned Scientists.

Some people have billed liquid coal, the name for petrol or diesel derived from coal, as a potential replacement to the oil on which countries rely heavily to fuel vehicles.

Likewise another alternative fuel, petrol from tar sands, is estimated to have 14% more global warming potential compared with standard petrol, says the union in its latest report Biofuels: an important part of a low-carbon diet.

"Corn ethanol, conversely, could be either more polluting or less than [petrol], depending on how the corn is grown and the ethanol is produced," the report says.

The analysis is based on replacing a fifth of all petrol used in the US with alternative fuels by 2030.

If most of these alternatives consist of liquid coal, the change could pump pollution into the atmosphere equivalent to 34 million more cars on the road, the report says.

But favouring cleaner "advanced biofuels" could cut harmful gases by a similar amount.

The cleanest alternative, the report says, is cellulosic ethanol, made from grass or wood chips. It could cut greenhouse emissions compared with petrol by more than 85%.

"We need to wean ourselves off oil, but we should replace it with the cleanest alternatives possible," says study author Patricia Monahan.

"Let's not trade one bad habit for another."
For more info- http://www.abc.net.au/science/news/stories/2007/2090413.htm?enviro

Environmental Factors Limit Species Diversity

It's long been accepted by biologists that environmental factors cause the diversity -- or number -- of species to increase before eventually leveling off. Some recent work, however, has suggested that species diversity continues instead of entering into a state of equilibrium. But new research on lizards in the Caribbean not only supports the original theory that finite space, limited food supplies, and competition for resources all work together to achieve equilibrium; it builds on the theory by extending it over a much longer timespan.

The research was done by Daniel Rabosky of the University of California, Berkeley and Richard Glor of the University of Rochester who studied patterns of species accumulation of lizards over millions of years on the four Caribbean islands of Puerto Rico, Jamaica, Hispaniola, and Cuba. Their paper is being published December 21 in the journal, Proceedings of the National Academy of Sciences.

Glor and Rabosky focused on species diversity -- the number of distinct species of lizards -- not the number of individual lizards.

"Geographic size correlates to diversity," said Glor. "In general, the larger the area, the greater the number of species that can be supported. For example, there are 60 species of Anolis lizards on Cuba, but far fewer species on the much smaller islands of Jamaica and Puerto Rico." There are only 6 species on Jamaica and 10 on Puerto Rico.

Ecologists Robert MacArthur of Princeton University and E.O. Wilson of Harvard University established the theory of island biogeography in the 1960s to explain the diversity and richness of species in restricted habitats, as well as the limits on the growth in number of species. Glor said the MacArthur-Wilson theory was developed for ecological time-scales, which encompass thousands of years, while his work with Rabosky extends the concepts over a million years. "MacArthur and Wilson recognized the macroevolutionary implications of their work," explained Glor, "but focused on ecological time-scales for simplicity."

Historically, biologists needed fossil records to study patterns of species diversification of lizards on the Caribbean islands. But advances in molecular methodology allowed Glor and Rabosky to use DNA sequences to reconstruct evolutionary trees that show the relationships between species.

The two scientists found that species diversification of lizards on the four islands reached a plateau millions of years ago and has essentially come to an end.

Glor said the extent and quality of the data used in the research allowed him and Rabosky to show that species diversification of lizards on the islands was not continuing and had indeed entered a state of equilibrium.

"When we look at other islands and continents that vary in species richness," said Glor, "we can't just consider rates of accumulation; we need to look at the plateau points."

Glor emphasizes that a state of equilibrium does not mean that the evolution of a species comes to an end. Lizards will continue to adapt to changes in their environment, but they are not expected to develop in a way that increases the number of species within a habitat.

Glor believes his work with Rabosky represents the "final word" on the importance of limits on species diversity over the rate of speciation when explaining the species-area relationship in anole lizards.
For more info- http://www.sciencedaily.com/releases/2010/12/101220163248.htm

Ocean Tidal Power as Renewable Energy

One of the Earth\'s great renewable energy sources is actually the energy that can be found in all the waves of the ocean. Let\'s look at this further.

If you have ever been to the ocean, you were probably fascinated by the phenomena of the waves crashing against the shorelines as the tides came in. The ocean\'s tides are the product of gravitational pull of the sun and the moon, as well as, the Earth\'s rotation. It causes the ocean waters to be raised and lowered from time to time. The tides have cycles of twelve and one half hours, twice per day, and are easily predictable.

The use of tidal power is seen as early as the twelfth century where tidal mills used the force of the tides to grind grain and corn. The eighteenth century brought competition from windmills and waterwheels. Tidal mills pretty much became extinct with the invention of cheap steam engines. In 1967, France became the first to be able to put tidal wave power to work on a large scale to produce electricity.

The generation of electricity from tidal waves is similar to that of hydroelectric power generation. Bigger dams, known as barrages, are built on the bottom of a tidal basin. Gates on the barrage allow the tidal basin to fill during incoming high tides. Likewise, the basin will empty through a turbine during the outgoing tide. This would turn an electric generator for the production of electricity. There are also systems that generate electricity from incoming and outgoing tides. This system can have a negative effect on plants and animals in the area.

Tidal fences are also used to generate electricity. Vertical axis turbines are mounted on fences. Passing water is forced through the turbines. Ideal locations for these are channels between two landmasses. Tidal fences are cheaper than tidal barrages and cause less of an environmental impact on large marine life.

Tidal turbines are a new technology used for tidal energy. They are similar to wind turbines and are arranged underwater in rows. They work best in areas with strong tides. Although they are heavier and costlier to build, they also are capable of capturing more energy. They are also the least environmentally damaging of all the tidal power technologies, since they do not interfere with migration paths.

In order for tidal power to work successfully it requires a tide difference of at least sixteen feet. Unfortunately there are only a few places where this occurs. This means tidal power plants cannot just be constructed anywhere. There are only a handful of sites on Earth with this type of tidal range. At present, France is the only country that has been successful in using tidal power. It is hoped developments in technology, through research, will be made to allow better use of this, what is now, wasted energy. The future of tidal energy seems hopeful. Tidal power has great potential and hopefully we can make better use of it in the future in our quest to find a replacement for fossil fuels.

This article is taken from- http://www.ezine-articles.org/ezinearticles/environment/ocean-tidal-power-as-renewable-energy.html

Advantages and Disadvantages of Renewable Energy

There are many energy sources today that are extremely limited in supply. Some of these sources include oil, natural gas, and coal. It is a matter of time before they will be exhausted.

Estimates are that they can only meet our energy demands for another fifty to seventy years. So in an effort to find alternative forms of energy, the world has turned to renewable energy sources as the solution. There are many advantages and disadvantages to this.

Renewable energy sources consist of solar, hydro, wind, geothermal, ocean and biomass. The most common advantage of each is that they are renewable and cannot be depleted. They are a clean energy, as they don\'t pollute the air, and they don\'t contribute to global warming or greenhouse effects. Since their sources are natural the cost of operations is reduced and they also require less maintenance on their plants. A common disadvantage to all is that it is difficult to produce the large quantities of electricity their counterpart the fossil fuels are able to. Since they are also new technologies, the cost of initiating them is high.

Solar energy makes use of the sun\'s energy. It is advantageous because the systems can fit into existing buildings and it does not affect land use. But since the area of the collectors is large, more materials are required. Solar radiation is also controlled by geography. And it is limited to daytime hours and non-cloudy days.

Wind energy uses the power of the wind to produce electricity. Although it is the largest job producer, it is reliant on strong winds. Wind turbines are large and, although you can use the area under them for farming, many consider them unattractive looking. They are also very noisy to operate. In addition, they threaten the wild bird population.

Hydroelectric energy uses water to produce power. This is the most reliable of all the renewable energy sources. On the down side, it affects ecology and causes downstream problems. The decay of vegetation along the riverbed can cause the buildup of methane. Methane is a contributing gas to greenhouse effect. Dams can also alter the natural river flow and affect wildlife. Colder, oxygen poor water can be released into the river, killing fish. And the release of water from the dam can cause flooding.

Geothermal energy uses steam from the Earth\'s ground to generate power. It uses smaller land areas than other power plants. They can run 24 hours per day, every day of the year. Disadvantages are that it is very site specific and, along with the heat from the Earth, it can also bring up toxic chemicals when obtaining the steam. Drilling geothermal reservoirs and finding them can be an expensive task.

Biomass electricity is produced through the energies from wood, agricultural and municipal waste. It helps save on landfill waste but transportation can be expensive and ecological diversity of land may be affected. In addition, its process needs to be made simpler.

Ocean energy is a clean and abundant energy form. It does, however, have high costs. Ocean thermal energy also requires close to a forty degree Fahrenheit difference in water temperature year round. In addition, construction and laying pipes can cause damage to the ecosystem.

There are many advantages to the use of renewable energy sources. There are also some disadvantages. The fact is energy demands will continue to increase. Through research and development, as well as, new technologies, the hope is many of the disadvantages of renewable sources of energy can be eliminated and we can successfully incorporate it into our power supplies.

 This article is taken from- http://ezine-articles.org/ezinearticles/environment/advantages-and-disadvantages-of-renewable-energy.html