Western Kentucky University Research Foundation Biodiesel Project

Pan, Wei-Ping ; Cao, Yan

Western Kentucky University Research Foundation Inc.

关键词: 10 Synthetic Fuels;   

DOI  :  10.2172/1086991
RP-ID  :  Final Report
RP-ID  :  EE0003156
RP-ID  :  1086991

美国|英语

来源: UNT Digital Library

【 摘 要 】

Petroleum-based liquid hydrocarbons is exclusively major energy source in the transportation sector. Thus, it is the major CO{sub 2} source which is the associated with greenhouse effect. In the United States alone, petroleum consumption in the transportation sector approaches 13.8 million barrels per day (Mbbl/d). It is corresponding to a release of 0.53 gigatons of carbon per year (GtC/yr), which accounts for approximate 7.6 % of the current global release of CO{sub 2} from all of the fossil fuel usage (7 GtC/yr). For the long term, the conventional petroleum production is predicted to peak in as little as the next 10 years to as high as the next 50 years. Negative environmental consequences, the frequently roaring petroleum prices, increasing petroleum utilization and concerns about competitive supplies of petroleum have driven dramatic interest in producing alternative transportation fuels, such as electricity-based, hydrogen-based and bio-based transportation alternative fuels. Use of either of electricity-based or hydrogen-based alternative energy in the transportation sector is currently laden with technical and economical challenges. The current energy density of commercial batteries is 175 Wh/kg of battery. At a storage pressure of 680 atm, the lower heating value (LHV) of H{sub 2} is 1.32 kWh/liter. In contrast, the corresponding energy density for gasoline can reach as high as 8.88 kWh/liter. Furthermore, the convenience of using a liquid hydrocarbon fuel through the existing infrastructures is a big deterrent to replacement by both batteries and hydrogen. Biomass-derived ethanol and bio-diesel (biofuels) can be two promising and predominant U.S. alternative transportation fuels. Both their energy densities and physical properties are comparable to their relatives of petroleum-based gasoline and diesel, however, biofuels are significantly environmental-benign. Ethanol can be made from the sugar-based or starch-based biomass materials, which is easily fermented to create ethanol. In the United States almost all starch ethanol is mainly manufactured from corn grains. The technology for manufacturing corn ethanol can be considered mature as of the late 1980s. In 2005, 14.3 % of the U.S. corn harvest was processed to produce 1.48 x10{sup 10} liters of ethanol, energetically equivalent to 1.72 % of U.S. gasoline usage. Soybean oil is extracted from 1.5 % of the U.S. soybean harvest to produce 2.56 x 10{sup 8} liters of bio-diesel, which was 0.09 % of U.S. diesel usage. However, reaching maximum rates of bio-fuel supply from corn and soybeans is unlikely because these crops are presently major contributors to human food supplies through livestock feed and direct consumption. Moreover, there currently arguments on that the conversion of many types of many natural landscapes to grow corn for feedstock is likely to create substantial carbon emissions that will exacerbate globe warming. On the other hand, there is a large underutilized resource of cellulose biomass from trees, grasses, and nonedible parts of crops that could serve as a feedstock. One of the potentially significant new bio-fuels is so called "cellulosic ethanol", which is dependent on break-down by microbes or enzymes. Because of technological limitations (the wider variety of molecular structures in cellulose and hemicellulose requires a wider variety of microorganisms to break them down) and other cost hurdles (such as lower kinetics), cellulosic ethanol can currently remain in lab scales. Considering farm yields, commodity and fuel prices, farm energy and agrichemical inputs, production plant efficiencies, byproduct production, greenhouse gas (GHG) emissions, and other environmental effects, a life-cycle evaluation of competitive indicated that corn ethanol yields 25 % more energy than the energy invested in its production, whereas soybean bio-diesel yields 93 % more. Relative to the fossil fuels they displace, greenhouse gas emissions are reduced 12 % by the production and combustion of ethanol and 41 % by bio-diesel. Bio-diesel also releases less air pollutants per net energy gain than ethanol. Bio-diesel has advantages over ethanol due to its lower agricultural inputs and more efficient conversion. Thus, to be a viable alternative, a bio-fuel firstly should be producible in large quantities without reducing food supplies. In this aspect, larger quantity supplies of cellulose biomass are likely viable alternatives. U. S. Congress has introduced an initiative and subsequently rolled into the basic energy package, which encourages the production of fuel from purely renewable resources, biomass. Secondly, a bio-fuel should also provide a net energy gain, have environmental benefits and be economically competitive. In this aspect, bio-diesel has advantages over ethanol. The commonwealth of Kentucky is fortunate to have a diverse and abundant supply of renewable energy resources. Both Kentucky Governor Beshear in the energy plan for Kentucky "Intelligent Energy Choices for Kentucky's Future", and Kentucky Renewable Energy Consortium, outlined strategies on developing energy in renewable, sustainable and efficient ways. Smart utilization of diversified renewable energy resources using advanced technologies developed by Kentucky public universities, and promotion of these technologies to the market place by collaboration between universities and private industry, are specially encouraged. Thus, the initially question answering Governor's strategic plan is if there is any economical way to make utilization of larger quantities of cellulose and hemicellulose for production of bio-fuels, especially bio-diesel. There are some possible options of commercially available technologies to convert cellulose based biomass energy to bio-fuels. Cellulose based biomass can be firstly gasified to obtain synthesis gas (a mixture of CO and H{sub 2}), which is followed up by being converted into liquid hydrocarbon fuels or oxygenate hydrocarbon fuel through Fischer-Tropsch (F-T) synthesis. Methanol production is regarded to be the most economic starting step in many-year practices of the development of F-T synthesis technology since only C{sub 1} synthesis through F-T process can potentially achieve 100% conversion efficiency. Mobil's F-T synthesis process is based on this understanding. Considering the economical advantages of bio-diesel production over ethanol and necessary supply of methanol during bio-diesel production, a new opportunity for bio-diesel production with total supplies of biomass-based raw materials through more economic reaction pathways is likely identified in this proposal. The bio-oil part of biomass can be transesterified under available methanol (or mixed alcohols), which can be synthesized in the most easy part of F-T synthesis process using synthesis gas from gasification of cellulose fractions of biomass. We propose a novel concept to make sense of bio-diesel production economically though a coupling reaction of bio-oil transesterification and methanol synthesis. It will overcome problems of current bio-diesel producing process based on separated handling of methanol and bio-oil.