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| Fig. 1: Common Water Hyacinth. (Source: Wikimedia Commons) |
The Common Water Hyacinth, or Eichhornia crassipes as its binomial name, is a free floating aquatic plant. It has thick, wide, waxy leaves and bright purple-blue flowers arranged in spikes as shown in Fig. 1. The plant is native to South America in the Amazon River Basin and is now the most widely distributed species in the world, after being introduced as an ornamental plant to different nations. [1] As a highly aggressive and invasive species, it propagates rapidly and has suffocated several lakes, rivers, and waterways including the Tonle Sap in Cambodia, Lake Victoria in Congo, coastal areas of Queensland in Australia, and Chao Phraya River in Thailand. Infestations of the Common Water Hyacinth can double in size every 2 weeks and its seeds viable for more than 20 years, which results in dense mats being formed on the surface of water bodies as seen in Fig. 2. [2]
The plant was first introduced to Thailand in 1901 by Thai royalty, who brought it back from a visit to Indonesia due to its perceived strange beauty. It was used as a decoration and displayed in palaces and mansions before accidentally entering the canal nearby due to a flood. Since then, it has proliferated rapidly and spreaded across the whole nation. The excessive build-up of Common Water Hyacinth in waterways has caused Thai authorities to take this as a serious national issue. [3] There have been a series of attempts to get rid of these plants, including the Water Hyacinth Disposal Act in 1913 that was enacted by King Vajiravudh - unfortunately, the law proved to be impractical and was thereby revoked in 2009. There has been no successful attempt at eradicating this invasive species until today. This being said, the conversion of the common water hyacinth into a biofuel provides a potential solution to this national issue.
There has been substantial effort in many developing countries worldwide to extract ethanol from the Water Hyacinth due to its abundance and high biomass yield. For example in India, researchers have found bioconversion methods of the plant to bioethanol such as through using dilute sulfuric acid and enzymes under high temperature and pressure. [4] They found this method of using sulfuric acid to pretreat the plants highly effective and can be used for small-scale fuel ethanol production. To develop techniques more suited for larger-scale production, other researchers have found technological improvements to the process. A group of Chinese researchers found that using dilute acid combined with microbial pretreatment, the production of reducing sugars, which then undergoes the fermentation process into ethanol, is maximized. [5] Through this, they managed to obtain 430.66 milligrams of reducing sugars per gram of dried, grounded water hyacinth, which resulted in an ethanol production rate of 1.40 g/L from a solution consisting of 20 g/L of glucose, 20 g/L of enzyme, and 20 g/L of yeast. This would mean that 1 gram of dehydrated water hyacinth can release around 852kJ of energy. This improved method of enhancing bioethanol production from Water Hyacinth is a promising way for large-scale utilization of the invasive plant in developing nations.
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| Fig. 2: Dense Mat of Water Hyacinth in Nonthaburi, Thailand. (Source: Wikimedia Commons) |
Apart from acting as a means of combating the national issue of clogged up waterways from infestation of Water Hyacinth, converting this plant into bioethanol also provides Thailand with a source of renewable energy. Other developing countries have also been considering other plant species as potential biofuels. For instance to stabilize its energy needs, India is pondering on using algae, which is widespread, as a biofuel. [6] Therefore, due to its rapid propagation and ample source, the Water Hyacinth can contribute to Thailand's energy source to meet the countrys increasing energy needs from its fast economic development.
The excessive build-up of the Common Water Hyacinth in waterways has been an ongoing problem in Thailand for over a decade. Due to the economic, environmental, and health issues that this condition poses on the nation and there being no successful attempt at eradicating this invasive species, it is important to address this with urgency. The core value of the proposed solution is to turn the Common Water Hyacinth, which is abundant in Thailand's rivers, into useful products such as fuel. Although its ethanol yield per 100 gram may not be as high as that of other plants, its abundance can make this process viable. With research and development in more effective conversion methods, this can be a beneficial solution to the overpopulation of the species in Thailand's waterways.
© Pat Yontrarak. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] A. M. Villamagna and B. R. Murphy, "Ecological and Socio-Economic Impacts of Invasive Water Hyacinth (Eichhornia crassipes): A Review, " Freshwater Biol. 55, 282 (2010).
[2] A. Malik, "Environmental Challenge Vis-a-Vis Opportunity: The Case of Water Hyacinth," Environ. Int. 33, 122 (2007).
[3] N. Chomchalow and S Pongpangan, "Aquatic Weeds in Thailand: Occurrence, Problems, and Existing and Proposed Control Measures," in Aquatic Weeds in Southeast Asia, ed. by C. K. Varshney and J. Rzóska (Kluwer, 1973), p. 43.
[4] A. Das et al., "Production of Bioethanol as Useful Biofuel Through the Bioconversion of Water Hyacinth (Eichhornia crassipes)," Biotech 6, 70 (2016).
[5] Q. Zhang et al., "Enhancing Bioethanol Production From Water Hyacinth By New Combined Pretreatment Methods," Bioresource Technol. 251, 358 (2018).
[6] A. Summerville, "Algae Biofuels," Physics 240, Stanford University, Fall 2016.
