Biomass can be converted into different types of products, including:

1. Electrical/heat energy

2. Transport fuel

3. Chemical feedstock

Woody and herbaceous species are the ones used most often by biomass researchers and industry. Several parameters are important in the biomass conversion process. The principal considerations in terms of the material type are moisture content, calorific value, fixed carbon and volatile pro­portion, ash/residue content, alkali metal content, and cellulose-lignin ratio. In a wet-biomass conversion process, the moisture content and cellulose-lignin ratio is of prime concern, while in a dry-biomass conver­sion process, it is the alkali metal content and cellulose-lignin ratio. The Laticiferous plant species of Apocyanaceae, Asclepiadaceae, Convolvulaceae, and Euphorbiaceae have been analyzed for use as renewable energy sources. Analysis of oil and hydrocarbon contents of 15 different plant species tested has revealed that Carissa carandas L., Ceropegia juncea Roxb., Hemidesmus indicus R. Br., and Sarcostemma brunourianum W. A. are the most suitable species [16]. In another study, five different plant species Plumeria alba, C. procera, Euphorbia nerifolia, Nerium indicum, and Mimusops elengi have been evaluated as potential renewable energy sources. Whole plants and plant parts (leaf, stem, and bark) have been ana­lyzed for oil, polyphenol, hydrocarbons, crude protein, a-cellulose, lignin, ash, and mineral content. The barks of these plants were identified to have greater hydrocarbon content than the leaves. Based on the dry-biomass yields, hydrocarbon content, and other properties, these plant species most suitable for renewable energy sources have been identified [17]. In a study conducted on 51 plant species in Tennessee, in the United States, an exam­ination of the oil, polyphenol, hydrocarbon, protein, and ash content reveals that Lapsana communis yields the maximum oil (6.1% dry, ash-free plant sample basis). Chrysopsis graminifolia, Solidago erecta, and Verbesina alternifolia have been identified as rubber-producing species with 0.4-0.7% hydrocarbon [18].

2.4 Products

Several processes similar to petroleum refining are involved in the con­version of biomass into different products. Biorefineries convert biomass into different products in different stages. The different stages involved in the conversion of biomass to products are depicted in Fig. 2.11.

There has been a tremendous increase in biobased products such as ethanol, high-fructose syrups, citric acid, monosodium glutamate, lysine, enzymes, and specialty chemicals worldwide. It is estimated that in 2000-2006 in United States alone, there will be an increase in the use of liquid fuels, organic chemicals, and biopolymers from the current level of ~2%, 10%, and 90% each to 10%, 25%, and 95%, respec­tively [19].