C-heavy Molasses

C-Heavy Molasses, often referred to simply as final molasses, is a thick, viscous by-product obtained during the final stage of sugar production from sugarcane or sugar beet. It is called “C-heavy” because it is derived from the third and last crystallisation of sugar in the production process, after A and B grades of sugar and molasses have already been extracted. The term signifies a low sugar content but high concentration of other organic materials, minerals, and non-sugar solids, making it valuable for industrial and agricultural applications.

Composition and Characteristics

C-Heavy Molasses is a dark brown, syrup-like liquid containing a mixture of sugars, organic compounds, and minerals. Its physical and chemical characteristics are determined by the efficiency of sugar extraction and the quality of the cane or beet used.
Typical composition of C-Heavy Molasses includes:

• Total sugars (as sucrose, glucose, and fructose): 45–55 %
• Water content: 18–25 %
• Ash (mineral content): 8–10 %
• Nitrogenous compounds and organic acids: 10–12 %
• pH: 4.5–5.5

It is highly viscous and hygroscopic, with a strong, distinct odour and a dark colour due to caramelisation and the presence of melanoidins formed during sugar processing. Because of its chemical composition, C-Heavy Molasses is unsuitable for further sugar extraction but serves as a valuable feedstock for other industries.

Production Process

In sugar manufacturing, molasses is generated during the crystallisation stages when sugar is separated from the mother liquor. The process involves three primary stages:

1. A-Molasses (First Boiling): Contains the highest sucrose content; some sugar is recovered through re-crystallisation.
2. B-Molasses (Second Boiling): Contains moderate sugar levels; reprocessed to recover additional sugar.
3. C-Molasses (Third Boiling): The residual syrup after maximum sugar extraction; contains minimal recoverable sucrose and is considered the final molasses.

C-Heavy Molasses is collected after the final centrifugation, where further crystallisation is not economically feasible. It represents about 4–5 % of the total weight of sugarcane processed and about 25–30 kg per tonne of sugar produced, depending on process efficiency and cane quality.

Industrial Uses

Despite its low sugar content, C-Heavy Molasses is an important raw material in several industries due to its high fermentable sugar content and nutrient density. Major applications include:

• Ethanol Production: The most significant use of C-Heavy Molasses is as a feedstock for fermentation to produce ethanol. The fermentable sugars are converted by yeast into alcohol, which is used in the production of biofuels, beverages, and industrial chemicals.
• Distillery Operations: It serves as the primary raw material for producing rectified spirit, extra-neutral alcohol (ENA), and fuel ethanol.
• Animal Feed: In diluted form, molasses is added to livestock feed as a source of energy and as a palatability enhancer due to its sweet taste.
• Yeast and Citric Acid Production: Used in fermentation industries for cultivating yeast and producing citric acid through microbial processes.
• Fertiliser and Composting: Due to its high organic and mineral content, molasses is used in the formulation of liquid fertilisers and composting solutions to accelerate microbial activity.
• Carbon Source in Biogas Plants: Molasses can serve as a carbon substrate to increase methane yield during anaerobic digestion.

C-Heavy vs. B-Heavy and A-Molasses

The distinction between different grades of molasses is significant, particularly for ethanol production and energy policy.

C-Heavy Molasses, being the last residual, has lower sugar content compared with B-Heavy Molasses. However, it allows the sugar industry to maximise crystalline sugar production before diverting the remaining by-product to distilleries.

Significance in the Ethanol Blending Programme

In countries like India, C-Heavy Molasses has become a strategic resource for the Ethanol Blending Programme (EBP) aimed at reducing dependence on fossil fuels. Traditionally, ethanol production in India has relied on C-Heavy Molasses. However, to meet higher blending targets, the government has encouraged the use of B-Heavy Molasses and direct sugarcane juice as alternative feedstocks due to their higher ethanol yields.
C-Heavy Molasses yields about 240–260 litres of ethanol per tonne, whereas B-Heavy Molasses yields about 360–370 litres per tonne, and direct juice yields even more. Despite its lower yield, C-Heavy Molasses remains crucial for ensuring a steady supply of raw material for ethanol plants without significantly affecting sugar availability in the market.

Environmental and Economic Aspects

C-Heavy Molasses serves as an environmentally beneficial by-product, reducing industrial waste while generating economic value. However, improper disposal of molasses effluent, particularly spent wash from distilleries, can cause severe environmental pollution due to its high biochemical oxygen demand (BOD) and chemical oxygen demand (COD).
Efforts have been made to mitigate these effects through zero-liquid-discharge technologies, biomethanation, and composting with press mud from sugar mills. The integration of sugar and distillery industries enhances circular economy principles by converting waste into bioenergy and organic fertilisers.
Economically, C-Heavy Molasses is a valuable by-product for sugar mills, providing an additional revenue stream and ensuring resource efficiency in the sugar value chain.

Global and Regional Context

Molasses is produced globally in all major sugar-producing regions, including India, Brazil, Thailand, and Australia. In India, the majority of distilleries operate on C-Heavy Molasses as a feedstock, especially in states such as Uttar Pradesh, Maharashtra, and Karnataka. With the increasing emphasis on renewable energy and bioethanol, C-Heavy Molasses continues to play a vital role in balancing sugar production, ethanol supply, and rural economic development.