Biodiesel feedstock selection: which of the following is the standard practical feedstock for biodiesel production via transesterification?

Introduction / Context:
Biodiesel is a renewable diesel-range fuel consisting of mono-alkyl esters of long-chain fatty acids, typically produced by transesterification of triglyceride oils or fats with an alcohol (usually methanol) in the presence of a catalyst. Feedstock selection drives fuel quality, cost, and sustainability metrics.

Given Data / Assumptions:

• Commercial biodiesel processes are designed around triglyceride feedstocks.
• Common sources include fresh vegetable oils, used cooking oils (UCO), tallow, and other waste fats.
• The question asks for a practical, standard feedstock among the listed options.

Concept / Approach:
Used vegetable oils (waste cooking oils) are rich in triglycerides ideal for transesterification. They are widely collected, lower-cost than virgin oils, and contribute to waste reduction. In contrast, LSHS (low sulfur heavy stock) is a petroleum fraction with negligible triglyceride content; bagasse is lignocellulosic biomass unsuitable for direct transesterification; “herbal plants” is not a specific triglyceride feed and implies raw biomass rather than extracted oils.

Step-by-Step Solution:
Identify chemistry: biodiesel requires triglycerides → choose an oil/fat source.Map options: used vegetable oils meet this chemical requirement directly.Reject non-triglyceride or non-specific biomass choices (LSHS, bagasse, generic plants).

Verification / Alternative check:
Industry practice across many countries sources significant biodiesel volumes from UCO because of cost and sustainability advantages; ASTM D6751 and EN 14214 standards accommodate such feedstocks with appropriate pretreatment (degumming, FFA reduction).

Why Other Options Are Wrong:
Herbal plants: not directly a triglyceride feed unless oil is extracted; too vague.LSHS: petroleum oil, not reactive as triglycerides for FAME production.Bagasse: fibrous sugarcane residue, not an oil.

Common Pitfalls:
Ignoring free fatty acid (FFA) levels in used oils; high FFA requires pretreatment (acid esterification) before base-catalyzed transesterification.

Final Answer:
used vegetable oils