utorak, 3. svibnja 2011.





From the earliest days of internal-combustion engines, technological visionaries dreamed that engines would run on fuel made from plants. Experiments conducted in the 19th century showed that it was possible, and both Henry Ford and Rudolf Diesel supported the notion. Interest has waxed and waned for decades. These days, it is running high once again, and the fuels have acquired a modern moniker: biofuels.

While the geopolitical and environmental risks of oil dependency may be obvious today, it was not always so. In the early days of motorized transport, fuels derived from plants lost out to fuels refined from crude oil, which could be obtained cheaply in many parts of the world just by poking holes in the ground. Not only were gasoline and diesel the cheapest fuels for many decades, but they are about as energy-dense as liquids can be, which makes them superb choices for carrying vehicles long distances. Replacing them will not be easy, and the struggle to do so has produced some of the most intense controversies of modern society.

In the search for replacements, biofuels have attained the greatest political momentum, in part because they promise lucrative new markets for farm products. In the United States, Congress had adopted extensive mandates and subsidies to get a biofuels industry off the ground, and other countries have also adopted renewable-fuel policies.

But first-generation biofuels -- chiefly, ethanol made from corn or sugar cane, or biodiesel made from vegetable oil -- have provoked intense backlash. In principle, biofuels offer a huge advantage over fossil fuels. The source plants absorb carbon dioxide from the air as they are growing, and consequently, the carbon dioxide that is released when biofuels are burned does not represent a net addition of that greenhouse gas to the atmosphere. In practice, some fossil fuels, especially natural gas, are consumed in refining today's biofuels, one source of controversy about them.

In addition, an ever larger portion of the world’s crops is being diverted for biofuels, as developed countries pass laws mandating greater use of nonfossil fuels and as emerging powerhouses like China seek new sources of energy. But with food prices rising sharply in early 2011, many experts began to call on countries to scale back their headlong rush into green fuel development, arguing that the combination of ambitious biofuel targets and mediocre harvests of some crucial crops is contributing to high prices, hunger and political instability.

Many scientists believe second-generation biofuels made from plant wastes, or from crops specially grown for the purpose on land not suitable for food production, offer greater promise than the biofuels being produced today. But the technology to make these newer fuels is in its infancy and the claims of its advocates have yet to be proved.


There has been heated debate about whether carbon emissions from ethanol production and use are lower than those from oil and whether the 33 percent of the U.S. corn crop diverted to ethanol drives up the price of food. Local effects of ethanol production, however, including water pollution and consumption, have received less scrutiny.

Encouraged by legislative measures, including notably the 2007 Energy Security and Independence Act, which mandated the use of 36 billion gallons, or 136 billion liters, of biofuels annually by 2022, the U.S. ethanol industry has boomed in the last few years. There are now at least 200 ethanol plants in at least 27 states, almost all using corn as a feedstock.

Nearly all the gasoline sold in the United States today is mixed with 10 percent ethanol, known as E10. Because ethanol provides about two-thirds the energy content of oil per unit, that 10 percent volumetric replacement equals about a 6 to 7 percent gasoline displacement, minus fossil fuel inputs for growing and processing.

The industry is on track to produce 12.5 billion gallons this year and is therefore nearing market saturation to supply E10, as the United States consumes about 138 billion gallons of oil annually. In March 2009, Growth Energy petitioned the U.S. Environmental Protection Agency to grant a waiver to allow gasoline to be blended with 15 percent ethanol. Because the fuel can corrode conventional car engines at higher percentages, the agency is running tests. A final ruling has been pushed to the fall of 2010.

Corn farming is the biggest source of pollution associated with ethanol production. Corn requires vastly more fertilizer and pesticides than soybeans or other potential biofuel feedstocks, such as perennial grasses, according to a 2007 report from the National Academy of Sciences.

Fertilizer and pesticide runoffs from the U.S. Corn Belt are key contributors to “dead zones” in the Gulf of Mexico and along the Atlantic Coast. A 2008 study by independent researchers, published in the academy’s Proceedings journal, calculated that increasing corn production to meet the 2007 renewable fuels target would add to nitrogen pollution in the Gulf of Mexico by 10 to 34 percent.

Water use for ethanol also concerns scientists, particularly in light of a 2003 U.S. Government Accountability Office report that found that water managers in at least 36 states expect shortages by 2013.

Modern plants use about three gallons of water to produce one gallon of ethanol. The National Academy of Sciences report estimated that a plant producing 100 million gallons a year uses as much water as a town of 5,000 people.

Reflecting environmental concerns over the expansion of biofuel crops, the 2007 energy bill called for 20 billion gallons of biofuel to be made from “advanced” feedstocks, such as cellulosic ethanol or algae, which are believed to have a lighter environmental footprint.

But there are no commercial-scale cellulosic ethanol or algae plants operating in the United States, mainly because they are not yet competitive on costs. U.S.D.A. projections show corn as the primary feedstock for U.S. ethanol production through 2020.


Biomass power — a $1 billion industry in the United States, according to the Biomass Power Association, a trade group based in Maine — has long been considered both renewable and carbon-neutral on its most basic level.

Dozens of biomass power plants, which typically burn plant or tree matter to generate electricity, are already in operation in a variety of states, like California, Michigan and Maine. In most cases, those plants have qualified for some form of renewable energy tax incentives or other benefits, as states used them to diversify their power portfolios.

But a long-simmering debate in Massachusetts questioning the environmental benefits of biomass has culminated in new rules that will limit what sorts of projects will qualify for renewable energy incentives there. If other states — or even Congress, which is writing energy legislation of its own — follow suit, it could have wide implications for biomass developers, as well as for states trying to meet renewable energy production targets.

Ian A. Bowles, the Massachusetts secretary for energy and environmental affairs, has called for new regulations that would impose stricter standards for biomass projects seeking to qualify for state incentives. The state also plans to develop careful carbon accounting rules for biomass power, and to throw its greatest support behind plants that produce both heat and power, which are considered more efficient than ones that generate only power.

The proposed changes in Massachusetts come after a study commissioned by the state suggested that careful regulation was needed to prevent biomass development from having a negative effect on New England forests, and on the climate generally.

Industry representatives warned that the new rules could hinder efforts to meet renewable energy goals, and to reduce greenhouse gas emissions over all. But environmentalists welcomed the move, saying it would protect forests and foster responsible development of electricity generated with biomass materials. Many environmental groups say that the benefits of biomass power — and all forms of energy derived from organic sources, including biofuels — are realized only in carefully controlled circumstances. The cycle of carbon emission and absorption also unfolds over long periods of time that need to be carefully monitored.

By providing incentives without strict rules governing which materials are burned and how they are harvested, governments risk creating a rapacious industry that could gobble up whole forests, critics warn. That could ultimately increase the amount of carbon dioxide being released into the atmosphere — one of the problems that renewable energies are supposed to address.More info at http://solarserdar.blogspot.com.


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