03.08.2015   Biomass Conversion

Feedstock for Biorefinery/Types of Biorefinery

Biorefineries can be classified into a number of categories depending on the feedstock used.

1. Biorefinery based on agriculture sector feedstock (dedicated crops and residue) including oilseed biorefinery

2. Forest biorefinery (forest residue mainly lignocellulosic feedstock)

Table 1.9 Classification of biorefinery based on feedstock

Type of biorefinery

Characteristic features

Resultant Products

Biorefinery based on agriculture and non-agriculture sector feedstock (dedicated crops and residue) including oilseed biorefinery

• Cereal biorefinery

Uses dedicated starch crops, sugar crops, and grains

Bioethanol

• Oilseed biorefinery

Uses oil seed crops and oil plants

Vegetable oils and biodiesel

• Green biorefinery

Uses grasses and green plants

Bioethanol

• Lignocellulosic biorefinery

Uses agriculture wastes and crop

Bioethanol

residues

(lignocellulosic)

Forest biorefinery (forest residue

Uses forest residues, barks, saw

Fuels, energy,

mainly lignocellulosic

dust, pulping liquors, and fibers

chemicals, and

feedstock)

materials

Biorefinery based on industry

Uses all types of wastes including

Methane, hydrogen,

(process residues and

forest generated waste,

biofuels, energy,

leftovers) and municipal solid

industrial waste, and municipal

chemicals, and

waste and waste water

solid waste

materials

(domestic waste)

Aquaculture-based biorefinery

Uses different types of aquatic

Third-generation

(algae — and seaweed-based

biomass capable of tapping the

bioethanol, energy,

biorefinery)

unlimited energy from sun

pharmaceutical

products

3. Biorefinery based on industry (process residues and leftovers), and municipal solid waste and waste water (domestic waste)

4. Aquaculture-based biorefinery (algae — and seaweed-based biorefinery).

The salient features of all these types of biorefineries are given in Table 1.9.

Biorefinery Based on Agriculture Sector Feedstock (Including Dedicated Crops and Residue, and Oilseed Feedstock)

These biorefineries use as their feedstock, dedicated crops (food or non-food crops), such as cereal crops, oilseed crops, grasses, and other non-food green plants, or residues generated from the agricultural crops. The first — and second- generation biofuels can be produced from this type of biorefinery. Presently, biodiesel, bioethanol, and biogas are the main types of biofuels which are pro­duced by commercially viable technologies. An overview of the conversion pro­cesses for these biorefineries is shown in Fig. 1.22.

These biofuels are presently produced from agriculture sector feedstock. The agriculture sector feedstock mainly contains sugar, starch, and cellulosic biomass which can be converted to biofuel (bioethanol) mainly by fermentation processes.

Fig. 1.22 Overview of conversion processes for agriculture sector feedstocks to biofuels (Source Ref. [38])

For this purpose, the macromolecular starch and cellulose is first hydrolyzed by enzymatic hydrolysis into smaller molecules like glucose. Fermentation of these sugars by either aerobic or anaerobic fermentation processes converts them to ethanol. The process details are already discussed in Sect. 1.2.1.2. The alcohol produced from food crops is called grain alcohol and that produced from ligno — cellulosic feedstock such as agricultural residues (wheat straw, rice straw, etc.), grasses (switch grass) is called biomass ethanol or bioethanol or lignocellulosic ethanol. The agriculture-based feedstock, which was, until recent times used as the major source for biofuel generation, is gradually being replaced by agriculture sector residue such as wheat straw.