14 DAY TRIAL // Transportation fuel needs could be satisfied with cheap biofuel supplied from wood till 2030, according to scientists.
Recently, they attained the first complete analysis of the DNA sequence of a tree, the black cottonwood (Populus trichocarpa) (photo).
The research may lead to the development of trees as an ideal "feedstock" for a new generation of biofuels such as cellulosic ethanol. The study took 4 years to be finished, at the U.S. Department of Energy's Joint Genome Institute (DOE JGI) and Oak Ridge National Laboratory (ORNL), uniting the efforts of 34 institutions from around the world, including the University of British Columbia, and Genome Canada; Ume? University, Sweden; and Ghent University, Belgium.
"Biofuels could provide a major answer to our energy needs by giving the United States a homegrown, environmentally friendlier alternative to imported oil," said DOE's Under Secretary for Science Dr. Raymond L. Orbach.
"Fine-tuning plants for biofuels production is one of the keys to making biofuels economically viable and cost-effective. This research, employing the latest genomic technologies, is an important step on the road to developing practical, biologically-based substitutes for gasoline and other fossil fuels."
"Biofuels emit fewer pollutants than fossil fuels such as gasoline. In addition, poplar and related plants are vital managers of atmospheric carbon. Trees store captured carbon dioxide in their leaves, branches, stems, and roots. This natural process provides opportunities to improve carbon removal from the air by producing trees that effectively shuttle and store more carbon below ground in their roots and the soil. Moreover, bioenergy crops re-absorb carbon dioxide emitted when biofuels are consumed, creating a cycle that is essentially carbon neutral", said Dr. Gerald A. Tuskan, ORNL and DOE JGI researcher.
Poplars have been chosen for this study, because of their extraordinarily rapid growth, relatively compact genome size of 480 million nucleotide units (40 times smaller than that of pine) in 19 chromosomes, and the fact that they can be targeted for biofuels production.
"Under optimal conditions, poplars can add a dozen feet of growth each year and reach maturity in as few as four years, permitting selective breeding for large-scale sustainable plantation forestry", said Dr. Sam Foster of the U.S. Forest Service.
"This rapid growth coupled with conversion of the lignocellulosic portion of the plant to ethanol has the potential to provide a renewable energy resource along with a reduction of greenhouse gases."
There were identified over 45,000 protein-coding genes, more than any other organism sequenced to date, approximately twice as many as present in the human genome (which has a genome six times larger than the poplar's). The team identified 93 genes associated with the production of cellulose, hemicellulose and lignin.
The biopolymers cellulose and hemicellulose constitute the most abundant organic materials on earth, which can be broken down into glucose that, in turn, can be fermented into alcohol and distilled to fuel-quality ethanol and other fuels.
Poplar is the third plant to date to have its genome completely sequenced. The first, back in 2000, was a weed, Arabidopsis thaliana (which has 4 times less DNA than poplar). Rice was the second, in 2004.
Populus trichocarpa is one of the tallest broadleaf hardwood trees in the western U.S., native to the Pacific coast from San Diego to Alaska. The sequenced DNA was isolated from a specimen collected along the banks of the Nisqually River in Washington State. This species is already used in timber and paper industries. "Fifteen years from now, fully domesticated varieties of the tree, optimally tuned to grow faster and longer, better resist insects and disease and require less water and nutrients, could be growing like any other crop on tree farms spread across large regions of the United States", researchers said.
Scientists have to identify - amongst poplars' 45,500 genes - those responsible to its growth, to manage a selective breeding and genes manipulation to achieve desirable traits. The main goal is to create a variety to be used as a source of ethanol, which can be used as fuel. Currently, ethanol is more expensive and difficult to produce from wood than it is from crops like corn.
Researchers also want to produce a tree variety which absorbs more greenhouse effect producing carbon dioxide. The research focuses also on microbes, in order to discover more efficient new biotechnology-based methods of producing fuels from biomass.
Over fifty leading scientists in the field of biofuels research predict in a near future that cost-effective methods to produce fuels will be achieved. DOE scientists envision a future with vast poplar farms in regions with suitable climate, which could provide a steady supply of tree biomass rich in cellulose that can be transformed by specialized biorefineries into fuels. Other regions of the country might specialize in different "energy crops" suited to their particular climate and soil conditions. In addition, a large quantity of biofuels might be produced from agricultural and forestry waste.
This study also shed light on other more theoretical fields of plant evolution. About 10% of the poplar genes have no homologue in Arabidopsis. This is a first step toward determining the genetic difference between a tree and a herb.
Scientists discovered the lines of descent of the poplar, and Arabidopsis began to split some 100 to 120 million years ago. Doubling of a large part of the poplar's genes has occurred twice in history. One occurred at about the time the Arabidopsis line of descent split its separate way; the second duplication was much more recent.
Comparison of the genomes of the poplar and Arabidopsis showed clearly that the DNA of Arabidopsis has evolved further than that of the poplar.
Thus, evolution takes place at different rates in different plants.