methods of biomass breakdown involve the use of bacteria, yeasts, and enzymes, which also break down carbohydrates. Fermentation, the process used to make wine, changes biomass liquids into alcohol, a combustible fuel. A similar process is used to turn corn into grain alcohol or ethanol, which is mixed with gasoline to make gasohol. Also, when bacteria break down biomass, methane and carbon dioxide are produced. This methane can be captured, in sewage treatment plants and landfills, for example, and burned for heat and power.
Biomass oils, like soybean and canola oil, can be chemically converted into a liquid fuel similar to diesel fuel, and into gasoline additives. Cooking oil from restaurants, for example, has been used as a source to make biodiesel for trucks.
See also: Biofuels, Biochemical Platform, Biomass Conversion, Thermochemical Platform.
Biomass to Liquids
The biomass-to-liquid (BTL) process concept is a process for converting various types of biomass to liquid fuels and uses a variety of processes (Table B-23).
Table B-23 Conversion of biomass to fuels.
| Starch/sugar crops | ||
|---|---|---|
| Hydrolysis | ||
| Sugar | ||
| Fermentation | ||
| Refining | ||
| Ethanol | ||
| Lignocellulose biomass | ||
| Pyrolysis/liquefaction | Gasification | Anaerobic digestion |
| Bio-oil | Synthesis Gas | Bio-oil |
| Hydrotreating | Fischer-Tropsch | Biogas |
| Hydrocarbon fuels | Hydrocarbon fuels | Gas treating |
| Methane | ||
| Oil-producing plants | ||
| Pretreatment | ||
| Vegetable oil | ||
| Esterification | ||
| Biodiesel | ||
There are two types of biomass feedstock that can be employed to produce BTL fuels – woody and herbaceous. Woody feedstock comprises wood chips, wood powder and sawdust, obtained from ordinary forestry (wood logs), short-rotation forestry, various wood residues, and wood waste. Herbaceous feedstock includes chaffed dedicated energy crops and straw.
Owing to biomass composition, woody feedstock is better suited for energy applications than herbaceous feedstock. Woody biomass also has a larger production potential for energy (including BTL) application; however, the production potential of herbaceous biomass is currently under-explored as the path to useful products is open, for example (Table B-24):
Table B-24 Routes to liquid fuels from biomass.
| Biomass | ||||||
| Pretreatment | ||||||
| Gasification | ||||||
| Synthesis gas | ||||||
| Fischer-Tropsch | ||||||
| Upgrading | ||||||
| Gasoline | ||||||
| Diesel fuel | ||||||
| Methanol synthesis | ||||||
| Methanol-to-gasoline | ||||||
| LPG | ||||||
| Gasoline |
Biomass pyrolysis is a process by which a biomass feedstock is