for production of food for human beings and animals, conversion of energy into useful ways, and production of various chemicals. This book chapter discusses in brief about types of biomass and their conversion technologies for obtaining valuable chemicals due to photocatalytic valorization.
1.2.1 Biomass Types and Their Composition
Biomass can be obtained from nature directly in the form of waste. According to many varieties, biomass can be divided into several categories which are given below [3]:
1 (a) Biomass from wood (Stems, branches, sawdust, etc.)
2 (b) Herbaceous biomass (Flowers, grasses, straws, corncob, rice husk, etc.)
3 (c) Aquatic biomass (Marine and freshwater algae, microalgae, etc.)
4 (d) Animal and human waste biomass (Bones, various other manures, etc.)
5 (e) Contaminated biomass and industrial biomass wastes (semi-biomass: Municipal solid wastes, fiberboard, plywood, etc.)
6 (f) Biomass mixture.
Feedstocks of biomass are divided into several analyses such as proximate, ultimate, and structural. The compositional values of various biomass types are given in Table 1.1 according to chemical/elemental analysis.
Table 1.1 Elemental and chemical composition of biomass types [4].
| Biomass groups/elemental composition | Wood biomass | Herbaceous biomass | Aquatic biomass | Animal and human waste biomass | Contaminated biomass and industrial biomass wastes | Biomass mixture |
|---|---|---|---|---|---|---|
| C (%) | 49–57 | 42–58 | 27–43 | 57–61 | 43–45 | 45–71 |
| O (%) | 32–45 | 34–49 | 34–46 | 21–25 | 36–41 | 16–46 |
| H (%) | 5–10 | 3–9 | 4–6 | 7–8 | 5–6 | 6–11 |
| S (%) | <1–1 | <1–1 | 1–3 | 1–2 | 0.25–0.4 | <1–2 |
| N (%) | <1–1 | <1–3 | 1–3 | 6–12 | 1.5–1.75 | 1–6 |
| VM (%) | 30–80 | 41–77 | 42–53 | 43–62 | 76–77.5 | 41–79 |
| FC (%) | 6–25 | 9–35 | 22–33 | 12–13 | 11–16 | 1–15 |
| M (%) | 5–63 | 4–48 | 8–14 | 3–9 | – | 3–38 |
| A (%) | 1–8 | 1–19 | 11–38 | 23–34 | 11–17 | 3–43 |
*Carbon (C), Oxygen (O), Hydrogen (H), Sulfur (S), Nitrogen (N), Volatile matter (VM), Fixed carbon (FC), moisture (M), and ash (A) content.
Biomass is recognized as renewable energy carriers in terms of electrical or heat energy and transportation of fuels to replace the need of fossil fuels so that the harmful effects of environment can be limited but it all depends on quality and quantity of biomass feedstocks. Moreover, several characteristics should be kept in mind to evaluate the performance of any biomass feed which are listed below:
1 (i) Moisture content,
2 (ii) Calorific value,
3 (iii) Ash content,
4 (iv) Proportion of fixed carbon and volatile substances,
5 (v) Alkali metal content,
6 (vi) Cellulose/lignin ratio,
7 (vii) pH, etc.
1.2.2 Biomass Valorization Techniques
Biomass is converted into useful energy after applying various technologies into some valuable products like sugars, lignin, glycerol, etc. Generally, biomass is just decomposed/burned directly to generate energy in industries but in this process, fewer benefits can be achieved. Therefore, some important techniques which valorize the biomass utilization are employed such as pyrolysis, gasification, liquefaction, and biochemical processes [5]. These non-photocatalytic biomass valorization techniques can upgrade the quality and provide variety of products with maximum utilization of biomass feedstocks, if the participation of catalysts is possible.
Table 1.2 Biomass valorization techniques with important aspects [5].
| Biomass valorization techniques | Feedstocks | Temperature | Products |
|---|---|---|---|
| Pyrolysis | Cellulose, hemicelluloses, and lignin | 500 °C | Charcoal, bio-oil and gaseous fuels |
