Substrate costs

The process illustrated in Figure 4.6 was developed to production scale with a capacity of 200,000 tonnes per year. This process, developed by British Petroleum, was one of several in Europe and Japan that, although fully developed, was never operated substrate commercially. This was due to sharply increased substrate costs in 1973 and political costs and social pressures against the use of petroleum-based substrates (possibly contaminated with carcinogenic or toxic compounds). Such systems do operate in the former USSR, producing Candida guilliermondii as feed. 

Detailed economics of individual industrial processes, including SCP processes, are usually regarded as confidential, out of fear that publication may lend advantage to competitors. In addition, economy of scale rule generally applies (that is as the production capacity increases, the cost of the product decreases), so that direct comparisons can only be made between systems of similar capacity. Some economic data on SCP processes have been published and are presented in the Resource Material at the end of this chapter. You should appreciate that the data are outdated by more than a decade, during which time substrate costs will have varied relative to each other, and technology will have improved. This means that the comparative costs presented in Table 4.13, for example, may not be now as presented there. Nevertheless the data presented do provide an outline of the economics of SCP production. The processes referred to in the Resource Material are not necessarily those mentioned in the text and so you may find some differences in detail. 

Assume that the cost price of L-phenylalanine produced by direct fermentation is 285 kg 1 (100 tonnes per annum capacity). What percentage reduction in substrate costs are required for 1) precursor feeding and 2) biotransformation to be competitive on a cost price basis with direct fermentation ... 

In fed-batch mode residual substrate concentration may be maintained at very low levels. Ibis would reduce substrate costs, may remove catabolic repressive effects and may avoid possible toxic effects of the substrate. The fed-batch mode of operation may also avoid oxygen depletion of the culture during rapid growth. 

It follows that for precursor feeding to be competitive, substrate costs would have to be reduced by 35.05 - 2830 = 635 kg 1. So, the percentage reduction in substrate... 

A similar approach for bioconversion, based on the date given in Table 8.8, shows that die peirentage reduction in substrate costs required is 11%. 

Several factors affect the overall economics of PHA production. These include PHA productivity, PHA content, yield of PHA on carbon source, carbon substrate cost, and recovery method employed. Figure 1 shows the production costs of P(3HB) by various P(3HB) contents and P(3HB) productivities [29]. The effect of P(3HB) productivity on the production cost is only related to the cost of the fermentation equipment [18]. However, the P(3HB) content has multiple effects on the volume of the fermentation equipment and the recovery process [17,18]. The increase of P(3HB) yield on carbon source and the use of less expensive carbon substrates reduce the cost of carbon substrate [17, 29]. Development of an efficient recovery method, which will be different for each bacterium employed, is also important to overall economics of PHA production. When the actual fermentation processes employing many different re-... 

However, such comparison is a meaningless exercise. A comparison of silicon, sapphire, GaAs, or other established materials, rather than other SiC growth techniques, should occur instead. The blue and white LEDs can, for instance, be made on either sapphire or SiC substrates. From a performance point of view, there appear to be advantages with the SiC substrate but the substrate cost is lower on sapphire, therefore making it the most-used substrate. Granted, once larger substrates of SiC are made available, it is doubtful that the LED cost will be lower on sapphire. 

Growth of Renewable Resources. There are already large industries, associated with corn processing and food manufacture that utilize enzymes and microbial fermentation on an extremely large scale, In these cases, production and substrate costs can be 70% of the total product costs, and cost efficient engineering becomes paramount. The development of the industry that produces fuel grade ethanol, used as a nonleaded octane... 

Figure 12. Relation of glucose selling price to delivered cellulose substrate costs for enzymatic hydrolysis process. Data for 250,000 t/yr plant 90% overall process efficiency, 50% enzyme recovery (reuse).

Figure 15. Relation of ethanol selling price to glucose substrate costs...

The carbon source should be inexpensive because it is the major contributor to the total substrate cost (up to 50% of the total operating cost) (13). The ratios of the C and N contents of the hydrolyzed malt and soy wastes were 9 1 and 7.5 1, respectively, as determined by total organic carbon (4) and total Kjeldahl nitrogen (TKN) (4). 

Amorphous Si has several limitations. The first is that it can be used only in a drum configuration. The limitations of the drum configuration have been discussed in the preceding section. The second is cost. Due to the high substrate costs and low deposition rates, the cost is significantly higher than for... 

Thus, far flie production of either organism you have, apart from die cost of die carbohydrate substrate costs of 0 05 per kg biomass. Assume both organisms give the same output... 

Cost price of L-phenylalanine by precursor feeding is 35.05 kg" and substrate costs are 18.05 kg . 

The chromogenic assay may be used as a screen for inhibitors in the endpoint format described here, although relatively high substrate costs may limit... 

A few economic factors concerning the dilute acid process are discussed here in comparison to the enzymatic process. It must start with the yield that has been the focus of the reactor analysis and development. Production of fuels and chemicals from biomass is substrate cost intensive with feedstock costs representing roughly one half of total production costs 142, 55]. It is of paramount importance in most bioconversion processes to maximize the yield of the product from the biomass substrates. The most advanced dilute acid process has brought the saccharification yield to above 80% as verified by NREL bench-scale experiments [10]. The actual yield of the enzyme saccharification is dependent on the effectiveness of the pretreatment. However, it rarely surpasses 90% even with a highly efficient pretreatment. The enzymatic process also requires additional substrate because it has to be produced from cellulosic biomass. The amount of biomass feedstock needed for enzyme production is estimated to be about 9% of the total. With these in consideration, the yield of the acid saccharification is about even with that of the enzymatic process. What can... 

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