Biomass Energy R&D in the San Francisco Bay Area

Upadhye, R

Lawrence Livermore National Laboratory

关键词: 30 Direct Energy Conversion;    Biomass;    Biological Materials;    Combustion Heat;    Carbon Monoxide;   

DOI  :  10.2172/896606
RP-ID  :  UCRL-TR-217580
RP-ID  :  W-7405-ENG-48
RP-ID  :  896606

美国|英语

来源: UNT Digital Library

【 摘 要 】

Biomass is plant matter such as trees, grasses, agricultural crops or other biological material. It can be used as a solid fuel, or converted into liquid or gaseous forms, for the production of electric power, heat, chemicals, or fuels. There are a number of ways of getting energy from biomass, and a number of factors influence the efficiency of the conversion process. All biomass can be easily combusted. The heat of combustion can be used as heat, or can be used to run gas/steam turbines to produce electricity. However, most biomass combustion processes are inefficient and environmentally non-benign. The main pollutants from direct biomass combustion are tars, particulates, and VOCs. Biodiesels can be made from oils obtained from plants/crops such as soybean, peanuts and cotton. The oils from these sources are mainly triglycerides of fatty acids and not directly suitable as diesel substitutes. Transesterification processes convert the triglycerides into simple esters of the corresponding fatty acids (for example, Fatty Acid Methyl Ester or FAME), which can be directly substitutes for diesel fuels. Starches, sugars and cellulose can be fermented to produce ethanol, which can be added to gasoline, or used directly as an engine fuel. Fermentation of starches and sugars is established technology, practiced for thousands of years. Fermentation of cellulose to make ethanol is relatively harder, requiring additional intermediate steps to hydrolyze the cellulose first by adding acids or by raising temperature. Forestry wastes predominantly comprise cellulose and lignin. Lignin cannot be fermented using the current bio-organisms, and, as mentioned above, even cellulose is difficult to ferment directly. In such cases, a suite of alternative technologies can be employed to convert the biomass into liquid fuels. For example, the biomass can be gasified with the use of air/oxygen and steam, the resultant syngas (mixture of hydrogen and carbon monoxide) can be cleaned to remove tars and particulates, the gas can be shifted to obtain the proper balance between hydrogen and carbon monoxide, and the balanced gas can be converted into either methanol or other hydrocarbons with the use of Fischer-Tropsch catalysts. The liquid fuels thus produced can be transported to the point of use. In addition, they can be reformed to produce hydrogen to drive fuel cells. In addition to agriculture and forestry, a third, and significant, source for biomass is municipal waste. The biomass component of municipal wastes consists mainly of cellulose (paper products and yard wastes) and lignin (yard wastes). This waste can be combusted or gasified, as described above. All the technologies mentioned above are relatively mature, and are being practiced in some form or another. However, there are other technologies that may be promising, yet present significant challenges and may require more work. An example of this is the use of bacteria to use light to decompose water to yield hydrogen.