BioMed Research International / 2014 / Article / Tab 5

Research Article

Manufacturing Economics of Plant-Made Biologics: Case Studies in Therapeutic and Industrial Enzymes

Table 5

Open field cellulase manufacturing design premises and key assumptions.


Cellulosic ethanol facility assumptions
Cellulosic ethanol facility capacity 61 million US gallons/yearHumbird et al., 2011 [49]
Cellulosic feedstock700,000 metric tonnes (dry) corn stover per year, 2,000 metric tonnes/dayHumbird et al., 2011 [49]
Land area required for corn stover feedstock2,034,000 hectares/yearHumbird et al., 2011 [49]
Annual operating hours8,410 hours/yearHumbird et al., 2011 [49]
Conversion87 gallons ethanol/metric tonne corn stover @76% conversionHumbird et al., 2011 [49]
Enzyme loading20 mg enzyme “protein mixture” per gram cellulose in feedstock (2% wt/wt) Humbird et al., 2011 [49]
Enzyme mixture required4,100,000 enzyme “protein mixture” Humbird et al., 2011 [49]
Cellulase enzyme required2,870,000 kg/yearAbout 2% higher than in Klein-Marcuschamer et al., 2012 [16]
Cellulase in enzyme mixture70.0% total soluble proteinCalculated from above

Base case tobacco agronomic and cellulase enzyme production assumptions
Base case tobacco biomass production130 metric tonne fresh weight (FW)/ha year
Mass of a full grown tobacco plant growth
at high density
1.0 kg fresh weight (FW)/plant
Number of plants per hectare130,000 plants/hectareCalculated
Tobacco seed cost$0.001/seed
Tobacco growth cycle82 days from seed to induction, harvest at 7 days after induction spray
Tobacco planting season (US Midwest/South) Late March to late October
Land reuse during growing seasonBased on a total of 127 plant batches per year, land recycling can start with batch 94, so land requirement is only 0.74 of that required if no land was reusedCalculated
Tobacco production cost
(labor and machinery for seeding, harvesting)
Number of tobacco batches per year127 batches/yearCalculated
Cellulase expression level4 g cellulase/kg FW tobacco at 7 days after induction, with 2 applications of ethanol induction solutionWerner et al., 2011 [7]
Land area required5,519 hectares/yearCalculated
Tobacco land area required as a fraction
of corn stover land area required
Ethanol inductionFoliar application of aqueous solution of 2.5% (v/v) ethanol, 2 applications using ground irrigation/sprinklers (central pivot, traveler, or side roll), at 500 L/hectare
Cost of ethanol for induction$0.73/kgHumbird et al., 2011 [49]
Percentage of ethanol drawn off
from biorefinery for induction
Capital cost of ethanol spray
irrigation system
Annual operating cost of ethanol spray
irrigation system
$988/hectare year

Base case assumptions for plant-based cellulase production facility
Construction period12 monthsKlein-Marcuschamer et al., 2012 [16]
Start-up period18 monthsKlein-Marcuschamer et al., 2012 [16]
Project lifetime25 yearsKlein-Marcuschamer et al., 2012 [16]
Income tax rate40%Klein-Marcuschamer et al., 2012 [16]
Working capital30 days of labor, raw materials, utilities, wasteKlein-Marcuschamer et al., 2012 [16]
Start-up cost5% direct fixed capital investment, not depreciableKlein-Marcuschamer et al., 2012 [16]
DepreciationStraight line over 10 years, salvage value 5% direct fixed capitalKlein-Marcuschamer et al., 2012 [16]
Unlisted equipment5% of the major purchased listed equipmentKlein-Marcuschamer et al., 2012 [16]

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