Biomass, production

G. Shelef and C. J. Soeder, Algae biomass Production and Use, Elsevier, Amsterdam, the Netherlands, 1980. 

A realistic assessment of biomass as an energy resource is made by calculating average surface areas needed to produce sufficient biomass at different aimual yields to meet certain percentages of fuel demand for a particular country (Table 2). These required areas are then compared with surface areas available. The conditions of biomass production and conversion used ia Table 2 are either within the range of 1993 technology and agricultural practice, or are beheved to be attainable ia the future. 

Several studies estimate the potential of available virgin and waste biomass as energy resources (Table 4) (10). In Table 4, the projected potential of the recoverable materials is about 25% of the theoretical maximum woody biomass is about 70% of the total recoverable potential. These estimates of biomass energy potential are based on existing, sustainable biomass production and do not iaclude new, dedicated biomass energy plantations that might be developed. 

The maximum efficiency with which photosynthesis can occur has been estimated by several methods. The upper limit has been projected to range from about 8 to 15%, depending on the assumptions made ie, the maximum amount of solar energy trapped as chemical energy in the biomass is 8 to 15% of the energy of the incident solar radiation. The rationale in support of this efficiency limitation helps to point out some aspects of biomass production as they relate to energy appHcations. 

Climate and Environmental Factors. The biomass species selected for energy appHcations and the climate must be compatible to faciUtate operation of fuel farms. The three primary climatic parameters that have the most influence on the productivity of an iadigenous or transplanted species are iasolation, rainfall, and temperature. Natural fluctuations ia these factors remove them from human control, but the information compiled over the years ia meteorological records and from agricultural practice suppHes a valuable data bank from which to develop biomass energy appHcations. Ambient carbon dioxide concentration and the availabiHty of nutrients are also important factors ia biomass production. 

Table 30. Net Energy Analysis of Short-Rotation Wood Biomass Production ...

For the total integrated biomass production—conversion system, the arithmetic product of the efficiencies of biomass production and conversion is the efficiency of the overall system. An overall conversion efficiency near 45% would thus be produced by integrating the biomass plantation illustrated in Table 30 with a conversion process that operated at an overall efficiency of 50%. Every operation in the series is thus equally important. 

Polyethers such as monensin, lasalocid, salinomycin, and narasin are sold in many countries in crystalline or highly purified forms for incorporation into feeds or sustained-release bolus devices (see Controlled-RELEASE technology). There are also mycelial or biomass products, especially in the United States. The mycelial products are generally prepared by separation of the mycelium and then drying by azeotropic evaporation, fluid-bed driers, continuous tray driers, flash driers, and other types of commercial driers (163). In countries allowing biomass products, crystalline polyethers may be added to increase the potency of the product. 

Fermentation biomass productivities usually range from 2 to 5 g/(l h). This represents an oxygen demand in the range of 1.5 to 4 g 0/(l h). In a 500-m fermenter, this means achievement of a volumetric oxygen transfer coefficient in the range of 250 to 400 h"f Such oxygen-transfer capabihties can be achieved with aeration rates of the order of 0.5 (volume of air at STPA ohime of broth) and... 

Keller, R. and Dunn, I. J., Computer simulation of the biomass production rate of cyclic fed batch continuous culture, J. Appl. Chem., BiotechnoL, 28, 508-514, 1978. 

When excess substrate interferes with growth and/or product formation. One example is the production of baker s yeast. It is known that relatively low concentrations of certain sugars repress respiration and this will make the yeast cells switch to fermentative metabolism, even under aerobic conditions. This, of course, has a negative effect on biomass yield. When maximum biomass production is aimed at, fed batch cultures are the best choice, since the concentration of limiting sugar remains low enough to avoid repression of respiration. 

In any quantitative assessment of growth and/or product formation, it is essential to link formation of microbial biomass and products with the utilisation of substrate and nutrients. In the case of microbial biomass production, the total amount of cell mass yield formed is often proportional to the mass of substrate utilised. Mathematically this is coefficient expressed as the corresponding ratio, or yield coefficient ... 

Where a single substrate serves both as carbon and energy source, which is the case for chemoheterotrophic organisms used for biomass production, we can write ... 

Which of the two dilution rates should the process be operated at (Hint compare productivities for the product). Note that biomass productivity = D.x). 

Product extraction Effluent and waste disposal Medium preparation Seed vessel Purification Cell free supernatant Cell biomass Production bioreactor Downstream processing Medium sterilisation Primary culture Upstream processing... 

Optimisation of biomass production would require a large inoculum, comprising 10% of each inoculum stage. However, this involves many transfers which increases the risk of contamination. 

Since biomass productivity is Dx, product productivity (P) can be calculated as follows ... 

Biomass production of 94,608 tonnes would require 94,608/0.5 = 189,216 tonnes methanol. 

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