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โครงการหนังสืออิเล็กทรอนิกส์ด้านการเกษตร เฉลิมพระเกียรติพระบาทสมเด็จพระเจ้าอยู่หัว

life cycle of bioethanol production to avoid the pressure on water competition. Several measures
are recommended as follows:

8.5.1 Crop evapotranspiration (ET) reduction

Crop evapotranspiration (ET) during the bioethanol feedstock cultivation stage contributes
more than 99% of the total WF of bioethanol or around 95-98% of the total blue water footprint of

bioethanol. Therefore, in the water supply perspective, the ideal fuel crops to minimize the water
footprint of biofuels should be drought-tolerant, high-yield crops grown on little irrigation water

(Domiguez-Faus et al., 2009). There are many factors that able to influence the evapotranspiration
of crops e.g. temperature, crop yields, crop cycle and agricultural practices. For example, ET

generally increases with the temperature. To reduce the crop evapotranspiration, shortening of the
crop cycle or else improving crop yields are the possible methods. However, those two methods

generally must be traded off with each other as shortening the crop cycle may result in lower
biomass accumulation which in turn will decrease the final yield. Therefore, the development of

more efficient crop varieties is important to the sustainability of large scale bioethanol production in
the future.

For Thailand, the country average yields of cassava and sugarcane in 2011 were 19.3 and
76.2 tons/ha, respectively (OAE, 2012). The lowest yields are found in the Northeastern region of
Thailand which has the large cultivation areas associated with the Mun and Chi watersheds i.e.

around 19.2 tons cassava/ha and 74.4 tons sugarcane/ha (OAE, 2012). However, there is a

continual development of high yield varieties; the varieties of cassava such as Rayong 5, Rayong
9, Rayong 72 and Kasetsart 50 and the sugarcane varieties such as K 84-200, K 90-54 and U
thong 3 are being recommended to Thai farmers which potentially yield about 31-50 ton/ha for

cassava and 94-112 ton/ha for sugarcane. Nevertheless, to achieve the high genetic potential

yields, those high yields must be supported with good agricultural practices in farming e.g.
improving soil quality by using organic fertilizers and good practices in land preparation, plantation,
harvesting and regular weed control. In addition, more efficient irrigation systems are also required

in the high potential water stress regions. The study revealed that the Mun and Chi are the two

watersheds that the government agencies should attach significance.

8.5.2 Promotion of sugarcane ethanol into the Thai bioethanol system

As the results show that ethanol derived from sugarcane juice has the lowest total WF and

also the blue water footprint required as compared to cassava and molasses ethanol, the
substitution of cassava ethanol and molasses ethanol by sugarcane juice ethanol can help reduce

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