458

30 Feasibility and Economics of Biobutanol from Lignocellulosic and Starchy Residues

Biobutanol is an alcohol, usually produced by fermentation via the “acetone–

butanol–ethanol (ABE)” process employing several genera of bacteria, generally

Clostridia sp. [5]. Present, agricultural products such as cane sugar, molasses, corn,

and cassava are used as prospective feedstock for butanol production worldwide

[6]. However, most of the products mentioned are considered as food wherein the

supply is insufficient for the production of biobutanol thus leading to food versus

fuel crisis. From an environmental perspective, food crops for biofuel synthesis are

not economically sustainable. Therefore, lignocellulosic biomass of agricultural and

forest waste is feasible and is environmentally sustainable resource for production of

butanol. The conversion of biomass into biobutanol involves an initial pretreatment

process to expose carbohydrate present in the biomass. Pretreatment process being

one of the key sources for the conversion of lignocellulosic sources to butanol has

a great potential in improving the economy and efficiency of butanol production.

Pre-treated biomass undergoes microbial degradation to produce biobutanol. The

selection of cost effective substrate and process condition optimization increases

the butanol yield from lignocellulosic residues, thus decreasing the cost of butanol

production and making it economically more competitive.

30.2

Opportunities and Future of Zero Waste Biobutanol

Biobutanol is a colorless alcoholic biofuel comprised of a four carbon structure with

the chemical formula C4H9OH (molecular weight: 74.12) having boiling point of

117 ^∘C. Biobutanol appears to be the prospective substitute for petroleum derived

gasoline fuels owing to elevated calorific value, low volatility, less corrosiveness and

reduced moisture affinity than bioethanol [7, 8]. The first industrial scale biobu-

tanol production began in 1916 during World War I due to high demand of acetone

to produce cordite for British war industry [9]. The large portion of butanol pro-

duced worldwide is used in industry for the synthesis of methacrylate esters and

acrylate (Figure 30.1). Other main derivatives such as glycol ethers and butyl acetate

are primarily used as an industrial chemical and solvent for surface coating, paints,

Plasticizers

(6%)

Solvent

(13%)

Glycol

ethers

(15%)

Acetate

(24%)

Acrylate

(38%)

Others (4%)

Figure 30.1

World butanol utilization. Source: Guzman [1].