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30 Feasibility and Economics of Biobutanol from Lignocellulosic and Starchy Residues

The fermentation of biobutanol is possible in economic way, when cheap, low

grade feedstocks are processed on relatively small industrial scale. In butanol indus-

try cost of feedstock and its processing techniques plays a dominant role in cost of

production. It was estimated that feedstock amounts 65% of the total annual pro-

duction cost. Extensive study is still needed to make large-scale ABE fermentation

feasible. More efforts are required to suppress inhibitors formed during fermenta-

tion in a large scale. The different method of pretreatment may differ based on the

variety of feedstock, therefore choice of pretreatment technique which is econom-

ical, fast and efficient need to be explored for new feedstock in order to make an

attractive resource for biobutanol production. Though there are several literature on

production of biobutanol using various feedstocks, there still needs an improvement

in research regarding the upstream and downstream process to reduce the toxicity

level of end product and enhance the production yield to commercial scale [5].

The butanol production cost is calculated by considering the three factors such

as fixed cost, variable operating cost and by product formed during the process.

The fixed cost includes reactors, separation/purification equipment, maintenance,

depreciation, insurance, labor, etc. The variable operating expenses depends on the

cost of feedstock, chemicals, and utilities. These factors can be related to each other

using the formula given below.

Butanol Production cost = (Fixed cost + variable cost −byproduct credit)

Kumar et al. [40] conducted economic analysis of ABE fermentation with ligno-

cellulosic and starchy feedstock in 10 000 tons/year butanol. It was reported that the

production cost of butanol from glucose and sago were high as US$ 5.32 and US$ 3.87

per kg of butanol. The data were compared with cheaper lignocellulosic feedstock

such as corn stover, bagasse, sugarcane, barley, and wheat straw reported lowest

production cost between US$ 0.59–0.75 per kg of butanol. Therefore the availabil-

ity of feedstock, high residue yield rate and ease in cultivation also directly influ-

ence the economic production of biobutanol. The overall annual production cost of

biobutanol yield is increased by 6% due to the utilization of lignocelluloses involving

enzymatic hydrolysis of cellulose and hemicellulose when compared to any starchy

residual sources. The production cost for lignocellulose and starchy residues are cal-

culated by Kumar et al. [40] is listed in Table 30.3.

A comparative economic analysis of butanol production from corn and glycerol

is reported by Qureshi and Singh [1]. The economic comparison is represented in

Table 30.4. The cost of butanol from the Table 30.4 is high for starchy feedstock due

to high processing cost, whereas butanol produced from glycerol is cheaper than

other feedstock. The glycerol feedstock does not require any costly processing tech-

niques such as pretreatment thus reduction in overall operating cost. The cost of

lignocellulose feedstock is less compared to starchy and glycerol but process involves

pretreatment at high temperature and costly enzymatic hydrolysis.

The process cost of hydrolysis for lignocellulose can be reduced by adapting

new technology for pretreatment technique such as microwave and irradiation

techniques. The pretreatment of lignocellulose using induction and liquefied

petroleum gas (LPG) assisting heating was explored for biobutanol production. The