Step 1: Understanding the Concept:
The question asks to identify a process that converts biomass into a high-quality solid fuel characterized by low ash content. This involves understanding different biomass densification and conversion technologies.
Step 2: Detailed Explanation:
Let's analyze the processes listed:
(A) Gasification: This is a thermochemical process that converts biomass into a {gaseous} fuel (producer gas), not a solid fuel. The ash from the original biomass remains as a solid residue.
(B) Briquetting: This is a densification process where loose biomass (like sawdust, rice husk, agricultural waste) is compressed under high pressure and temperature. The natural lignin in the biomass plasticizes and acts as a binder, forming solid, dense blocks called briquettes.
Fuel Quality: Briquettes are a high-quality solid fuel. They are dense, have low moisture content, and burn uniformly.
Ash Content: The ash content of the briquette depends on the ash content of the raw material. By selecting raw materials with low inherent ash (like clean wood waste), the resulting briquettes can have a very low ash content, often in the 2-5% range or even lower. The process itself does not add ash. This fits the description well.
(C) Extrusion: This is a process of forcing material through a die of a desired cross-section. It can be a part of the briquetting process (screw extrusion), but "briquetting" is the more specific term for creating the fuel product.
(D) Pelleting: This is similar to briquetting but produces smaller, cylindrical pellets instead of larger briquettes. It is also a densification process. Both briquetting and pelleting produce high-quality solid fuels. Briquetting is a correct answer fitting the description.
Between the options, Briquetting is a primary process explicitly aimed at creating a high-quality, low-ash solid fuel from biomass residues.
Step 3: Final Answer:
Briquetting is a process that produces a high-quality solid fuel (briquettes) which, depending on the feedstock, can have a very low ash content. Therefore, option (B) is the correct answer.