Energy Life Cycle Analysis of Second-generation Biofuels from Rice Straw Biomass Waste
| Autor: | Chen, ci-syuan, 陳綺萱 |
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| Rok vydání: | 2009 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 97 To be a viable alternative, a biofuel should provide a net energy gain and be producible in large quantities without reducing food supplies. Taiwan locates in the subtropics and has excellent farming technology, thus producing abundant biomasses. However, this also results in a significant amount of agriculture wastes to be treated, with the rice straw contributing the most. From this reason, rice straw is chosen as the target material in this study. We use three energy indicators (overall thermal efficiency (ηE), energy return on investment (EROI) and net energy production ratios (NER)) to evaluate, through life-cycle accounting, energy produced from four kinds of thermo treatment technologies (radio-frequency plasma system (RFPS), microwave-induced system (MWS), downdraft gasifier system (DGS) and plasma torch system (PTS)). The energy life-cycle analysis (ELCA) includes energy inputs for rice straw collection, transportation, torrefaction, crushing, briquetting, energy production, condensation, air pollution control and distribution of biofuels to its point of end use. Energy types of products include syngas (CO+H2), methane, carbon dioxide and carbon black residue. Energy for every process and sub-step of the four processes are evaluated and proposed. The labor working hours of the 2nd generation energy plant is 8,000 hrs per year and capacities are simulated between 50,000 to 200,000 tonne. The distances of collection and transportation are calculated by a circle area of 50 to 100 kilometers diameter and 20 tonne truck is used. Also the on-site pretreatment of rice straw is evaluated. The results indicate that the transportation of rice straw takes major energy consumption and all above 90% of the average of the total input energy for every capacities and transportation distance for off-site pretreatment. As the capacity is increased, the energy consumption of transportation is expanded and the values of three energy indicators decrease. For on-site pretreatment, the three energy indicators increase drastically because the energy consumption of transportation decreases largely. Therefore, the energy input in the transportation of rice straw is a key point in the life-cycle process (LCP) and briquetting on-site for refused-derived fuel (RDF) to reduce the transportation energy is an alternative choice after the nature drying process using solar energy in the energy recovery of rice straw. The order of the three energy indicators is PTS＞DGS＞RFPS＞MWS. The optimum scenario case is using PTS with 50 kilometers diameter transportation, 80,000 tonne capacity and on-site pretreatment. For this optimum scenario case, the average of total input energy for the four assessed energy production systems in the life-cycle process (LCPEPS) is about 15.5% of the average output energy and the value of net energy balance (NEB) is 0.845. Every process of ELCA has positive energy benefit. The PTS of this optimum scenario case have the highest values of NER and EROI with the value of 8.86 and 7.86, respectively. And I-Lan County is a suitable location for building the biomass energy plant. In summary, to provide appropriate use of bio-energy sources, such as biomass wastes of rice straw, approaching the appeal to meet full recycling of biomass wastes and reducing greenhouse gas (GHG) emissions, also an ideal material in the 2nd generation biofuel plant. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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