Energy conversion, biological efficiency

Moore compared the technological branch of solar energy conversion, essentially photovoltaics, with the biological branch. He explained how a standard fuel cell that operates on oxygen and hydrogen produces water and electromotive force. A typical human-engineered fuel cell operates at 50-60 percent power conversion efficiency and uses platinum or other noble metals as catalysts. 

The ability to perform even the simplest of muscle movement requires complex coordination of the physical and chemical activities of the tissue. In recent years, nutritionists and exercise physiologists have described how the primary energy sources in food carbohydrates, fats, and proteins are transformed into the universal "currency" of biological energy, ATP. Oxidative metabolism processes the substrates through a cascade of enzymatic events to Insure maximal efficiency in energy conversion. At every level of this conversion, one or more metal ions serve as a cofactor to facilitate these biochemical reactions. The requirement of metals in the production of... 

Finally, the energy conversion processes of organisms can be studied and perhaps eventually applied to industrial methods. Biological processes convert energy from one form to another and at the same time create highly ordered—that is, low-entropy—systems. These natural processes are far more efficient than most industrial processes. 

Hall continues to put the case for large-scale biological solar energy conversion, but isolated systems have also received considerable attention in the laboratory. Bhardwaj et al have described a chloroplast photoelectrochemical cell in which chloroplasts were placed between an electron acceptor, such as anthraquinone-2-sulphonate and an electron donor, dichlorophenol or indo-phenol. The authors claim a 1% monochromatic power conversion efficiency for their most successful cells. Adams et by contrast, have used isolated... 

A large variety of totally artificial membranes accessible by synkinesis have structures unknown to biological systems. One may, for example, prepare membranes as thin as 2 nm containing photoactive groups in various positions, and they may show a totally unsymmetrical distribution of two different head-groups on both surfaces of a curved membrane (see Sec. 2.5.3). Natural membranes, on the other hand, are incredibly functional. They perform the complex energy conversion and reproduction processes of life with unsurpassed efficiency and reliability. 

Chemical composition, as discussed in the next section, is closely related to the caloric values of biomass, and also affects the efficiency of conversion, particularly when using a biological approach. For example, the presence of phenolics, particularly lignin, presents a major roadblock for enzymatic conversion of polysaccharides to alcohol. The conversion of juvenile biomass has been shown to have a higher moisture content and lower specific gravity than mature wood (47), and may respond more favorably to such a treatment process. The energy conversion of juvenile biomass materials by a thermal or biological methods needs to be explored. 

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