The Estimation of Environmental Benefits of Microalgal Biodiesel

• Main Author: 林妏怡
• Other Authors: Fu-Sung Chiang
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/86095915398885095822

碩士 === 國立臺灣海洋大學 === 應用經濟研究所 === 99 === In response to global climate change and for the energy security to achieve sustainable development, biofuel is thought to be one of the important alternative substitutes for petroleum. In addition to energy crisis and global warming, serious land subsidence is another problem in southwest coast of Taiwan. Total water demand by industry, commerce, agriculture and aquaculture has been increasing dramatically with economic development for a long time. The supply of surface water is insufficient due to the terrain and climate, while the cost of groundwater is lower and the quantity is stable. As a result, industries have been digging wells and extracting groundwater heavily. Inability to balance industrial development, land use, and water supply led to land subsidence as the recharge is slower than the extraction of groundwater. As fish farming is the major use of land, aquaculture has been considered one of the major reasons of land subsidence in southwest coast. Besides the land subsidence, aquaculture faces other problems including over 10 thousand hectares of fish ponds which are either idle or in waste land state. It is difficult to apply the same farm policy such as fallow or crop rotations to aquaculture. As fish ponds can storage water and conserve groundwater, this study intends to assess the benefit of algae biofuels generated by fish ponds which are left fallow or causing land subsidence. Algae (macro and microalgae) are the raw material of the third generation biofuels. Algae are known for their rapid growth, and they do not compete with people for food, and agriculture for arable land and fresh water in food production. Further, algae utilize atmospheric CO2 in the cultivation of algal biomass to achieve the target of CO2 mitigation. Considering environmental and economic sustainability, algae may be the most attractive raw materials for biofuels. Therefore, utilizing fish ponds which are left fallow causing serious land subsidence to culture algal biomass as a raw material of biofuels can make a change for aquaculture. Fish ponds left idle or causing land subsidence are not all in the area reached by tides. Thus, this study investigates the benefit of microalgae chosen as the raw materials of biofuels, instead of macroalgae such as Asparagus used to produce alcohol. According to the photosynthesis efficiency, the depth of open ponds for microalgae cultivation can not be over 30cm, and the depth usually between 15~30cm. Therefore, the water demand for microalgae cultivation is less than what fish and shrimp cultivation require. In addition, the biofuels produced from algal biomass can replace fossil fuels in transportation, reducing air pollutant emission. Therefore, the purpose of this study is to assess the benefits of bio-fuels from microalgae, focusing on the environmental benefits of microalgal biomass as a raw material for biodiesel. The environment effects considered in this study include CO2 fixation and air pollutant reduction. Three scenarios are investigated. The first one looks at culturing microalgae as a raw material for biodiesel from fallow fish ponds, the second one, culture from fish ponds left fallow and causing severe subsidence combined, and the third, culture from fallow fish ponds as well as fish ponds under two different levels of subsidence. In scenario one, the environmental benefits of CO2 fixation are estimated as 0.49 billion NT dollars, with 125,518.68 kiloliter biodiesel production, and the benefits of air pollutant reduction are calculated as 0.27 billion NT dollars. In scenario two, the environmental benefits of CO2 fixation are calculated as 1.86 billion NT dollars, with biodiesel production of 487,586.79 kiloliters, and the benefits of air pollutant reduction are 0.47 billion NT dollars. In scenario three, the environmental benefits of CO2 fixation are calculated as 2.35 billion NT dollars, with biodiesel production of 615,729.40 kiloliters, and the benefits of air pollutant reduction are 0.55 billion NT dollars. To summarize, the environmental benefits of scenario one are 0.76 billion NT dollars, while the benefits of scenario two are 2.33 billion NT dollars and the benefits of scenario three are 2.9 billions.