Wednesday, June 12, 2013
Arundo donax: An invasive species or a renewable biofuel?
Arundo donax, which is common called Giant Reed, is a plant species native to Asia and Africa. It was first introduced to California in the 1800s for the purpose of erosion control and was largely spread. It is extremely fit to the warm freshwater habitats in America, which causes fast reproduction and the invasion through out Maryland westward to northern California. However, in recent years, it was found can be used as an important renewable biofuel because of its high productivity and biomass. Therefore, should we consider it as an invasive species or a renewable biofuel?
Arundo donax is a serious invasive species in the world because its fast growth causes serious consequences. It is considered as a weedy and invasive species in many countries. There are several serious consequences caused by Arundo donax.
First of all, Arundo donax rapidly displace native plants, threatening species and native wildlife habitats. Arundo donax is fit for fresh water ecosystem and grows out of control. Finally, because it outcompetes native species, there are fewer numbers of other native plant species, and birds and other wildlife whose diets are dependent on native vegetation will disappear. According to a research paper related to riparian diversity and Arundo donax, “the total number of organisms, total biomass and taxonomic richness of aerial invertebrates associated with native vegetation is about twice associated with Arundo vegetation” (Herrera, 2003). According to the “Graph 1”, the square represents native vegetation while the triangle represents the Arundo vegetation. The aerial arthropod assemblage species numbers of organisms, biomass and richness are much less for the Arundo vegetation.
(Graph 1, Herrera, 2003)
Secondly, Arundo donax is a noxious plant, which can release DNT to the river influencing wildlife and drinking systems. The best example is the Colorado River ecosystem, which is seriously invaded by Arundo donax. (video: http://www.youtube.com/watch?v=SxSnY4Ms9DE ).According to the video, DNT will kill fish and frogs in the water and then water will flow to cities influencing people’s drinking systems and causing health threats.
Thirdly, Arundo donax chokes riverside and stream channels, making the rate of stream flow much less than before. Many river channels have been occupied with Arundo donax, which turned to “Arundo islands”. And it guzzles trillion of gallons of water per year, causing drying up of the part of Colorado River.
However, Arundo donax also has useful functions. It has been considered as an important potential biofuel because of its high yield and large biomass. Biomass is the biological material from living organisms, that always being used in renewable energy. Arundo works as the feedstock for producing cellulosic ethanol (Pilu, 2012). The high productivity of Arundo donax makes people focus on it as potential energy source. It is significantly more productive than other plant species. For instance, one study shows that growing willows for biofuel in riparian strips with high-planted density of 15,300 trees/ha, generated 16.8GJ/ha while Arundo could generate 810GJ/ha (Bell). Arundo donax can grow to heights between 20 to 30 feet and can always be harvested twice per year per field. Therefore, many organizations and companies have begun to consider Arundo donax as biofuel and started production. “Midway through 2012, construction on the largest cellulosic ethanol facility in the world is completed in Italy” (Green, 2012). Arundo donax is used as the primary feedstock, and after construction, the Arundo donax can produce 8,000 to 8,400 BTUs of energy per pound. (Green, 2012). After recognizing the large benefits brought by Arundo donax, many people suggest that we should plant Arundo donax for biofuel production. For instance, Portland General Electric (PGE) is proposing to use Arundo donax as replacement energy for their Boardman power after 2020 when coal power plants need to be shut down. (PGE organization). From a clean and sustainable energy perspective, it is a good idea to promote Arundo donax planting to produce renewable energy. However, it has downsides, as Arundo donax is one of the most serious invasive species with noxious chemical releasing.
Do the benefits overweight the downsides? Different groups of people have different ideas. Some people think it is a bad idea to use invasive plants for biofuels because we need to input more money to eradicate it. Arundo grows so fast, and it was introduced to prevent erosion. It has a high ability to survive, and even fire cannot eradicate their root segments. Accordingly, California is battling the plant at costs $5,000 to $25,000 an acre (Fried, 2012). The renewable energy benefits brought by Arundo are even less than the cost used to eradicate invasive individuals. Therefore, many scientists suggest that use this money to grow native plants, which can also be used as biofuel but do not influence native wildlife.
However, some organizations just want to try to use Arundo as a clean energy. Oregon Department of Agriculture’s (ODA) just want to walk a tightrope. ODA really wants to find a new source of homegrown and carbon-neutral energy, but they also feel afraid to introduce a new invasive species. So, they made a regulation to allow biofuel production while minimizing the risk. For instance, they allow Arundo for biofuel under permit, prohibit Arundo in floodplains and riparian areas, and make experiments to keep Arundo from being a noxious plant. (Oregon invasive species blog, 2012) In this way, Arundo can be used as a new renewable energy with less impact on local habitats. Because Oregon still is not invaded by Arundo donax, there is a possibility that it could cause some serious effects. We must avoid planting it on the riparian area or in habitats with endangered species.
After reviewing both sides of Arundo donax, it is clear that although it is a serious invasive species, it also becomes the most productive biofuel energy due to its high productivity and biomass. The best way to balance two sides is to avoid the free spread of Arundo donax. When cultivating the Arundo as a biofuel, it must be monitored to prevent its invasion into other species habitats. For future research, many scientists are focusing on genetic improvement of this species to avoid its noxious qualities and try to find ways to control it growth (Pilu, 2012).
Bell, G.P. Ecology and Management of Arundo donax, and approaches to riparian habitat restoration in southern California. The Nature Conservancy of New Mexico.
Herrera, A.M., Dudley, T.L. (2003).Reduction of riparian arthropod abundance and diversity as a consequence of giant reed (Arundo donax) invasion. Biological Invasions 5. pp 167
Pilu, R., Bucci, A., Badone, F.C., Landoni, M. (2012). Giant reed (Arundo donax L.): A weed plant or promising energy crop? African Journal of Biotechnology. Vol 11 (38) pp. 9163-9174. http://www.academicjournals.org/ajb/PDF/pdf2012/10May/Pilu%20et%20al.pdf
Arundo- your turn to comment. (2012) Oregon invasive species blog
Battle Creek Watershed conservation
Fried, R. (2012) Using invasive plants for biofuels is a very bad idea. Green Growth Investement blog
Mr. Green (2012). Arundo donax: An old plant, a new source of energy. Molecular Sieve Mavens. http://hengyeusa.com/community/arundo-donax-an-old-plant-a-new-source-of-energy