"biodiesel production generated a surplus of crude glycerol (John et al., 2011).Nevertheless, sincethe concentration of glycerol in the crude glycerol is unable to achieve a high level, a purificationprocess is necessary before producing PHB which contributes to the complexity of PHBindustrial production.YIELD COMPARISONTo get a better idea of the relative viability of these three processes, some simple calculationsusing data from the literature search can be carried out to give the total yield in tons per year of2 PHB from 50 km of farm land. PHB FROM SUGARCANE BAGASSETable 2: Data used in sugarcane bagasse yield calculation.Average worldwide yield for 2012 70.24 t/ha (FAO, 2012)Bagasse yield ~0.3 t/t raw sugarcane0.218 g/g bagasseGlucose yieldPHB yield [GM E. Coli] 0.78 g/g Glucose2 2 Assuming a factory area of ~2.5km , 47.5km of land can be used for raw sugarcane production:? 100h ? ? 2 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? = 70.25 × × 47.5 ? ? = 334,000 2 h ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? = 334,000 × 0.3 = 100,000 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? = 100,000 × 0.218 = 21,800 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?? ? ? ? ? = 21,800 × 0.78 = 17,000 ? ? ? ? ? ? ? ? ? ? ? ?PHB FROM PALM OILTable 2.2: Data used in palm oil yield calculationAverage annual oil yield ~4 t/ha(USDA , 2012)0.61 g/g Palm oil(Budde, et al., 2011)PHB yield [Ralstoniaeutropha]2 Assuming again, a factory area of ~2.5 km :? 100 h ? ? 2? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? = 4 × × 47.5? ? = 19,000 2 h ? ? ? ? ? ? ? ? ? ? ? ?? ? ? ? ? ? ? ? = 0.61 × 19,000 = 11,600? ? ? ? ? ? ? ? ? ? PHB FROM CASSAVA WASTEWATER (CSW)Table 2.3: Data used in CSW calculation15 t/haAverage annual cassava yieldCSW yield 3.05 t/t CassavaCOD Content 0.0204 t/tCSWPHB yield [Cupriavidus sp.] 0.31 t/t CODStarch yield 0.260 t/t CassavaThis process requires two separate factories, so this calculation is under the assumption of a2 factory area of 2*2.5 = 5 km .? 100 h ? ? ? ? ? ? ? 2? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? = 15 × × 45 ? ? = 67,500 2 h ? 1 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?? ? ? ? ? ? ? ? ? ? ? ? ? = 67,500 × 3.05 = 206,000? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? = 206,000 × 0.204 = 4,200? ? ? ? ? ? ? ?? ? ? ? ? ? ? ? ? ? ?? ? ? ? ? ? ? ? ? ? ? ? ? = 4,200 × 0.260 = 1,100 ? ? ? ? ? ? ? ? Based on the discussion and calculations above, the cassava starch waste water (CSW)has been chosen for the report due to its various advantages. Compared with the carbon sourcesdiscussed, the CSW contains the highest PHB biomass in cell dry weight which reaches at85.53%.The second, CSW has a preponderance of competitive price since the necessary nutrientsfor PHB synthesis such as carbohydrates, phosphorus, nitrogen and various acids are available inthe wastewater. Finally, the CSW can be used as not only carbon feedstock but also the rawmaterial to extract the bacteria for PHB production, which makes it possible to reduce the cost ofbacteria generation. As mentioned earlier, using CSW as a carbon source for PHB productionoffers a method to deal with the wastewater which may reduce both the contamination toenvironment and produce a useful product from waste.PROCESS DESIGN In the given area of land, two manufacturing plants will be present. The first will be thecassava starch manufacturing plant which serves a major role in PHB production. CSW will beobtained from the starch manufacturing process and will be used as the carbon source for PHBproduction.The cassava starch manufacturing process involves various stages starting from peelingand washing the fresh cassava roots till sedimentation and drying of the starch extract. Theprocess flow diagram for the production is shown in figure 2.PROCESS FLOW CHART: STARCH PRODUCTIONCROPS CASSAVA FRESH ROOTSWATERPEELING AND WASHINGPEELSMECHANICAL GRATINGSIEVINGSEDIMENTATIONWASTE WATERSTARCHRESIDUESOLIDSDRYINGSTARCHFig2: Process flow diagram for starch productionFrom the diagram, you can infer that the waste water along with the solids is rejectedfrom the process. It is then sent to pre-treatment for PHB production. PRETREATMENT The process of fermenting dissolved organic compounds into organic acids bymicroorganisms in the fermenter under anaerobic conditions is called acidogenic fermentationand it is also known as anaerobic digestion. During this process, volatile fatty acids are produced,and from previous studies it has been reported that VFAs can be used as substrates bymicroorganisms for PHB production (Yu, 2001). The treatment of wastewater efficiency can be evaluated in terms COD removal. The first step inthe pretreatment involves settling of solids in the waste water through simple gravity settling andremoval. Then, the main step includes the acidification/fermentation process which takes place ina batch reactor.(Rotor)(Temperature sensor)(Water input)(Sampling ports)(Sludge discharge) Fig3. The figure explains the batch reactor for sludge acidogenic fermentation of waste water.The anaerobic sludge from USAB waste water treatment plant of beer industry is used for theprocess. After the fermentation, saturated fatty acids such as acetic acid, butyric acid andpropionic acid are synthesized in the waste water with the help of acidogenic bacteria. Thesefatty acids play a significant role acting as potential substrates for PHB production. "