End-of-batch handling in ethanol production: After fermentation is complete, separated yeast biomass can be used for which purposes?
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ARecycling as inoculum for the next fermentation
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BAs single-cell protein (SCP) for animal feed
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CAs organic manure or soil amendment
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DAll of the above
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ENone of the above
Answer
Correct Answer: All of the above
Explanation
Introduction / Context:Downstream processing in ethanol plants includes separating yeast solids. This biomass has value beyond disposal, supporting circular and sustainable operations.
Given Data / Assumptions:
- Yeast is non-pathogenic industrial Saccharomyces.
- Biomass is separated via centrifugation or filtration.
- Quality and regulations permit appropriate reuse.
Concept / Approach:Separated yeast can be reused as pitching yeast (recycle), processed and sold as SCP for animal feed due to high protein content and vitamins, or composted as nutrient-rich organic matter for agriculture.
Step-by-Step Solution:
List common fates of spent yeast.Check technical and regulatory feasibility of each route.Select the inclusive option “All of the above.”Verification / Alternative check:Brewing and bioethanol industries routinely implement these routes depending on economics and regulations.
Why Other Options Are Wrong:
Single uses alone omit other valid and common applications.“None” contradicts widespread practice.Common Pitfalls:Skipping quality checks (for example, contamination, heavy metals) before using as feed.
Final Answer:All of the above.