Food-Grade vs. Industrial-Grade CO₂ in Bioethanol Refineries

Carbon dioxide is a natural co-product of ethanol fermentation. Instead of releasing this CO₂, modern bioethanol refineries can capture, purify and supply it to different industries.

However, not all recovered CO₂ is intended for the same applications. Food-grade and industrial-grade CO₂ have different quality requirements, impurity limits and end-use considerations.

For ethanol producers, understanding these differences is important when designing CO₂ recovery systems and identifying potential markets. For buyers, knowing the required grade helps ensure that the CO₂ is suitable for the intended application.

This article explains the key differences between food-grade and industrial-grade CO₂ and what ethanol refineries and buyers should consider.

What is CO₂ from Ethanol Production?

During fermentation, yeast converts sugars from feedstocks such as maize or other grains into ethanol and CO₂.

The resulting CO₂ stream can be captured from the fermentation process rather than being released into the atmosphere. However, raw fermentation CO₂ is not ready for every application.

It can contain:

• Water vapour
• Ethanol and other volatile compounds
• Oxygen and other gases
• Trace fermentation-related impurities

The gas therefore needs to be treated, purified and tested according to its intended use.

The required level of purification depends on whether the CO₂ is intended for food and beverage applications or industrial processes.

What is Food-Grade CO₂?

Food-grade CO₂ is carbon dioxide that meets the quality and safety requirements necessary for applications involving food or beverages.

It is commonly used for:

• Beverage carbonation
• Sparkling water
• Food processing
• Modified-atmosphere packaging
• Food preservation
• Certain freezing and cooling applications

The important consideration is that food-grade CO₂ is not defined only by its overall CO₂ purity. Individual impurities also matter.

Depending on the application and applicable standards, parameters such as moisture, oxygen, hydrocarbons, sulphur compounds and other trace contaminants may need to be tightly controlled.

For beverage manufacturers in particular, unwanted impurities can affect the taste, odour, appearance or safety of the final product.

This is why food-grade CO₂ requires appropriate purification, testing and handling throughout the supply chain.

What is Industrial-Grade CO₂?

Industrial-grade CO₂ is intended for applications where food-contact requirements do not apply.

Unlike food-grade CO₂, its specification is generally determined by the requirements of the specific industrial process.

The required quality can therefore vary considerably between applications.

Industrial CO₂ may be used in areas such as:

• Welding
• Dry ice production
• Industrial cooling
• Inerting and purging
• Greenhouse applications
• Chemical and manufacturing processes

An industrial application may not require the same level of impurity control as a beverage application. However, the gas still needs to meet the technical requirements of the process. Industrial-grade does not mean low-quality. It means the CO₂ is produced and specified for an industrial application rather than a food-contact application.

Food-Grade vs. Industrial-Grade CO₂

The primary difference is the required specification and intended use.

Factor	Food-Grade CO₂	Industrial-Grade CO₂
Main purpose	Food and beverage applications	Industrial processes
Purity requirements	Generally more stringent	Application-dependent
Trace impurities	Closely controlled	Controlled according to process requirements
Odour/taste	Highly important	Usually less critical
Food contact	Suitable when applicable requirements are met	Not automatically suitable
Testing	Detailed quality and impurity testing	Based on application and customer specification
Handling	Greater emphasis on food-safety controls	Focus on technical and operational requirements

The key point is that CO₂ should be matched to the application, not simply selected based on its overall purity percentage.

How is CO₂ from Ethanol Refineries Purified?

Capturing CO₂ from fermentation is only the first step. A typical recovery process may include several stages.

1. CO₂ Collection

CO₂ generated during fermentation is collected from the fermentation system.

2. Cleaning and Scrubbing

The gas is treated to remove unwanted components carried over from the fermentation process.

3. Cooling and Drying

Cooling and separation processes help remove moisture and condensable substances.

4. Purification

Additional treatment can be used to reduce remaining impurities and achieve the required product specification.

Depending on the system, this can involve filtration, activated carbon treatment, drying and other purification technologies.

5. Compression and Liquefaction

Purified CO₂ can be compressed and liquefied for storage and transportation.

6. Quality Testing

The final product is tested against the specification required for its intended application. This final step is particularly important for food and beverage applications, where individual impurity limits can be critical.

Does Fermentation-Derived CO₂ Automatically Become Food-Grade?

No. The origin of CO₂ does not automatically determine its grade.

Although ethanol fermentation provides a useful source of recoverable CO₂, the gas must undergo suitable purification and quality control before it can be supplied for food or beverage applications.

A refinery targeting food-grade markets needs to consider:

• Feed-gas composition
• Purification technology
• Impurity removal
• Quality testing
• Storage conditions
• Equipment cleanliness
• Transportation and handling
• Applicable standards and customer requirements

Therefore, the statement “CO₂ comes from ethanol production” is not enough to establish that it is food-grade.

The final specification and quality-control process are what matter.

Why CO₂ Grade Matters for Ethanol Refineries

CO₂ recovery can create an additional value stream for a bioethanol refinery.

Instead of treating fermentation CO₂ simply as a by-product, producers can recover and purify it for customers with different requirements.

The potential benefits include:

• Better Resource Utilisation: A naturally generated fermentation stream can be converted into a commercially useful product.
• Additional Revenue: Recovered CO₂ can provide an additional source of revenue alongside ethanol and other refinery co-products.
• Multiple Market Opportunities: Depending on the purification system and verified specification, producers can serve industrial or food and beverage markets.
• More Efficient Biorefinery Operations: Recovering useful co-products supports a more integrated approach to bioethanol production.

However, producing a higher specification CO₂ product also requires appropriate investment in purification, testing, storage and quality management.

How Should Buyers Choose the Right CO₂ Grade?

The right approach is to start with the application, rather than the product label. Before purchasing CO₂, businesses should consider:

1. Intended Application

Determine exactly how the CO₂ will be used and whether it will come into direct contact with food or beverages.

2. Required Specification

Review the required CO₂ purity and individual impurity limits for the application.

3. Certificate of Analysis

Ask suppliers for relevant quality data and batch testing information.

4. Moisture and Other Impurities

Parameters such as moisture, oxygen and other trace contaminants may be important depending on the process.

5. Storage and Transportation

Liquid CO₂ requires suitable storage vessels and transportation systems designed for the product.

6. Supply Reliability

Consistent quality and dependable supply are just as important  as the initial specification.

7. Applicable Standards

For food and beverage applications, ensure that the product meets the relevant regulatory and industry requirements.

CO₂ Recovery at Edhas Biofuel

Edhas Biofuel recovers CO₂ as a co-product of its grain-based ethanol production process. The company offers liquid CO₂ and dry CO₂/dry ice for different applications, with its CO₂ product information specifying food-grade and industrial-grade options.

For customers, the important consideration is not simply the source of the CO₂. The focus should be on the verified product specification, quality testing and suitability for the intended application.

Which CO₂ Grade Do You Need?

Food-grade and industrial-grade CO₂ are both valuable products, but they serve different requirements.

• Food-grade CO₂ is intended for applications where strict impurity control and food-safety considerations are essential.
• Industrial-grade CO₂ is specified according to the technical requirements of industrial processes.

For ethanol refineries, the opportunity is to capture fermentation CO₂ and process it into a product with a clearly defined specification.

For buyers, the best choice depends on the application, required purity, impurity limits, applicable standards and supply requirements.

Ultimately, the process should follow a simple principle:

• Application → Required Specification → Purification → Testing → Storage → Delivery

By matching CO₂ quality to its intended use, ethanol producers can create greater value from fermentation while customers can obtain a product that meets their specific operational requirements.