Supercritical CO2 extraction is a method of separating valuable compounds from plant matrices with high efficiency and selectivity. Supercritical fluids are highly compressed gases which at a certain specific temperature and pressure behave halfway between a gas and a liquid. Once reached the supercritical state, the extraction solvent density increases with the increase of the pressure, in turn enhancing the solubility of the extracted materials.

The process of supercritical CO2 extraction can be divided into two steps:

1. The plant material is solubilized with the solvent at the supercritical state.
2. The extracted compounds are then recovered from the solvent to produce the end product.

It is crucial to prepare the plant matrix thoroughly to achieve optimal results during extraction. The matrix should be prepared before being placed in the baskets. Even more important is to remove as much water as possible from the matrix for two main reasons. If you’re interested in learning why it is essential to remove water from the matrix, keep reading!

As mentioned above, it is crucial to prepare the plant matrix to achieve the best results. This means removing water. Here are the reasons why, in the supercritical CO2 extraction process, it is necessary to eliminate water to prepare the matrix effectively.

1. Water (which is polar) is incompatible with supercritical CO2 (which is non-polar). Water therefore has the opposite polarity compared to SC-CO2 and is completely insoluble in it, but can be expelled from the matrix by simple mechanical action, uselessly absorbing kinetic energy and lengthening the process times. Make sure you have dried the matrix very well, leaving a quantity of water less than 10% by weight, optimally around 7%, otherwise you will waste energy and money extracting the water (it costs much less to use a dryer!).
2. Grinding the matrix is very important because it increases the exchange surface and facilitates extraction. However, we must not exaggerate. Grain size values greater than 2 mm or less than 0.5 mm do not very often give satisfactory results. When the particle size of the matrix is too large, the difficulty coefficient of the extraction may be too large and the process efficiency too low. When the grain size of the matrix is too small we are dealing with dust. Powders easily suffer from the channeling effect. Wormholes form in the matrix and most of the CO2 will pass into these channels without extracting anything. Furthermore, dust tends to clog the filters, which will require frequent cleaning. Dusts < 0.4 mm must be absolutely avoided as they can pass through the filters and clog the high pressure circuit, block the valves, break the basket filters. Typically, the milled matrix should contain less than 10% particle sizes smaller than 0.4 mm.

Supercritical fluid extraction applies to solid matrices, the acronym of which is SFE (Supercritical Fluid Extraction). In the case of liquid matrices, we are not talking about extraction but about fractionation, the acronym of which is SFF (Supercritical Fluid Fractionation), but we will deal with this methodology in another article.

First, let’s analyze the general aspects that describe the extraction principles. Extraction from solid matrices with liquid/supercritical solvents, called solid-liquid extraction, allows the desired compounds to be separated from the solid raw material, generally of botanical origin.

Generally, it is necessary to identify the most suitable solvent for the target compounds of the extraction. In our case it will be supercritical CO2. The solvent will occupy all possible spaces and then spread throughout the matrix. The extraction process then begins, generally by diffusion, in which the desired elements pass into the solvent, becoming concentrated.

The conditions or parameters of the process depend on the compounds of interest that are intended to be extracted from the chosen matrix. The supercritical CO2 extraction machine must be equipped with automation software that allows you to enter all these process parameters. A good machine must be able to load these parameters into the process recipes. Each matrix will have one or more process recipes based on the compounds that need to be extracted.

To make a good extraction you need to know:

1) The optimal pair of pressure/temperature to solubilize the target compound.

2) The flow rate of the CO2 pump and, if requested, the flow rate of the cosolvent pump.

3) The characteristics of the raw material

Before starting the extraction of any raw material, it is necessary to know its degree of humidity and grain size. It is necessary to reduce the amount of water contained in the raw material as much as possible, since water slows down extraction. A water content close to 7% is considered optimal. The size of the grind is also very important. A fine grain size of the ground material increases the exchange surface and consequently facilitates extraction. A good value is between 0.6 and 0.9 mm. A size of the ground material that is too small, less than 0.4 mm, can trigger the channeling effect (a channel that forms in the matrix where the supercritical CO2 passes thorough), compromising extraction.

Choosing the right pressure/temperature pair is the first step. Usually the operator refers to scientific publications that will help get closer to the correct values. However, some tests with values close to those published will be necessary to verify the solubility of your own raw material. When possible, low pressures and temperatures will be chosen, which increase the selectivity of the supercritical CO2, avoiding dragging unwanted compounds into the extract. Low temperatures ensure higher densities and so higher solubility power.

Subsequently the operator will have to choose the right flow rate of the CO2 pump. Unfortunately, this value cannot be found in publications. Due to the tiny size of the lab scale apparatus used for testing, volumes of just a few milliliters, this value, once published, is very often too large and therefore unusable in a production machine. This value will have to be found by the operator. It is advisable not to overdo the flow rate. Lower flow rates give better yields as the residence time of the solvent increases. A normal extraction kinetic has a value of 20 or 30 kg of supercritical CO2 per kg of matrix. In rare cases much higher values are justified.

The supercritical CO2 extraction process is a sustainable choice that protects both human health and the environment. Furthermore, it provides high-quality products and ensures significant applications in any sector due to its versatility.

If you are ready to consider the possibility of introducing a supercritical CO2 extraction process, do not hesitate to contact us. We will be happy to explain all the features of our machinery and support you in identifying the equipment that best suits your needs

Supercritical CO2, which is a solvent that is both environmentally friendly and versatile, finds application in a multitude of areas, including the extraction of solvents from polymer and inorganic matrices. The process capitalizes on the unique properties of CO₂ above its critical temperature and critical pressure, allowing it to function as a gas and a liquid simultaneously. This characteristic makes supercritical CO₂ an attractive option for the removal of apolar or medium-polar and even some polar solvents from various plastic, vegetable, or mineral matrices.

There are several advantages associated with the use of supercritical CO2. Firstly, it is a safe option, ensuring minimal risk to individuals and the environment. Furthermore, it possesses low toxicity, making it a desirable choice. Additionally, supercritical CO2 can be recovered and recycled, thereby reducing its environmental impact. This feature adds to its appeal as a solvent. Moreover, it can be utilized for the extraction of specific compounds or solvents that require explosion control (Atex-Ex). It is worth noting that CO2 is inert and non-flammable, creating an ideal environment that prevents the ignition of vapours or liquids during the extraction process. During the extraction the absence of oxygen pull the UEL and LEL down to significance. And moreover, for many use the applied temperatures are very low in comparison to traditional solvent recovery technologies.

The supercritical CO2 extraction process involves the careful regulation of pressure and temperature to attain the desired supercritical conditions. Subsequently, the supercritical CO2 is directed to flow through the material that requires the removal of spent solvents or reagents resulting from chemical reactions. In this process, supercritical CO2 acts as a solvent, effectively extracting unwanted solvents from the matrix. Following this, it is separated from the extracted solvents to facilitate recovery and recycling. Due to its effectiveness and efficiency, this method is extensively employed in industries such as plastics, pharmaceuticals, and chemicals.

It is indeed possible to implement this particular methodology in numerous application fields:

• In the context of chemical synthesis, this methodology can be employed to effectively eliminate solvents or extraction reagents, thereby enabling the seamless continuation of the synthetic route.
• Moreover, this methodology finds great utility in the production of films or fabrics that are derived from baths. In such cases, it becomes imperative to thoroughly dry the fabric before subjecting it to any subsequent treatments.
• This approach can also be employed in the extraction of aromas after their extraction through distillation or other analogous techniques.
• The pigment industry can greatly benefit from the implementation of this methodology, particularly in terms of reducing the quantity of diluents that are present in the colouring solution.
• Lastly, the explosives industry can also leverage this methodology to ensure a safe and controlled working environment. Specifically, by adopting this methodology, it becomes possible to work in an anoxic and less reactive environment, thus mitigating potential risks.

Supercritical CO2 presents itself as an environmentally friendly and safe alternative to conventional solvents, such as ethanol or chloroform, which can pose risks to human health and the environment. It should be noted, however, that the successful implementation of this process requires specialized equipment and technical expertise.

As you can see, there are numerous uses and applications of supercritical CO2. If you’re ready to implement supercritical CO2 in your company for solvent extraction from polymers or other materials, don’t hesitate to contact us. We will provide you with all the information and our specialized assistance to identify the machinery that best suits your needs.

The first question that must be answered is: what is a supercritical fluid. A supercritical fluid is any substance at a temperature and pressure above its critical point. CO2 is the most used fluid. It can diffuse through solids like a gas, and dissolve materials like a liquid. In addition, close to the critical point, small changes in pressure or temperature result in large changes in density, allowing many properties of a supercritical fluid to be “fine-tuned”. Supercritical fluids are suitable as a substitute for organic solvents in a range of industrial and laboratory processes. Carbon dioxide and water are the most commonly used supercritical fluids, being used for decaffeination and power generation, respectively.

The supercritical fluid technology is the best extraction technique available today. It is the best not only for the quality of its extracts, but also for the absence of contamination. For this reason, the exhausted matrix (flour, etc. ..) can be used without any fear, which is impossible for solvent extraction. It is the best for its rapid process (hours instead of days) and the presence of a reducing environment in which the oxidation can not occur. Is the best because it is the only true green technology: it does not pollute, there are no solvents or even exhausted to dispose of. It is the best because it is the only one that can transform waste products (which represent only a cost) in high value-added active ingredients that would otherwise be acquired by large pharmaceutical companies at a high price.

For a long time, the poorest technologies (processes with chemical solvents) were more spread. But today we all realize the damage caused by chemical solvents to human health and very soon (in Europe since 2012) they will be banned worldwide. It is clear that today, from an economic standpoint, investment in traditional technologies that use chemical solvents has no future.

The economic, technical and political reasons underlying the choice of the technological proposal are the following:

1) The characteristics of SFE technology are versatility combined with eco-sustainability, acting in the transformation processes on two different levels:

a) in the initial processing phase of vegetable raw materials and in the entire food supply chain. Supercritical CO2 extraction (SFE) works directly on raw materials. Furthermore, waste materials are used as primary products (those parts that are currently disposed of) because with this technology they can be reused as a source of antioxidants.

b) only in final processes for specialized applications (e.g. pesticide: pyrethrum and neem). This is the case of powder coating of the drug, oil and liquids fractionation, concentration of active ingredients or the recovery of waste materials from previous processes.

2) Flexibility offered by SFE technology which can act on a wide range of process conditions and perform different processing phases (even in multi step extraction). This quality can be used both in the extraction and fractionation process, obtaining new productions and products. Examples are: de-oiled flour, numerous extracts in co-extraction, extractions carried out in multiple steps, where extraction conditions are different for each step.

The technical factors that determine the advantages of the SCF system are:

1. full use of raw materials because supercritical systems produce multiple products at the same time
2. reduced process times and high productivity and quality achieved in extraction
3. low cost of CO2
4. savings in disposal costs necessary with traditional technologies
5. low numbers of workers

3) High production quality recognized by the whole market.

Characteristics of SFE technology and its position on the market:

1. it is recognized by the market as a high quality production technology and in some cases without competition (e.g. decaffeination of coffee, lycopene, olive oil with a high content of polyphenols, extracted pesticides)
2. inclusion in food platforms and higher-end market, conditioning entire supply chains and in processes to reach niche or unique products available only thanks to this technology (e.g. extraction of antibacterials for the proven high efficiency, removal of pesticides, extraction of compounds particularly active in anti-tumor therapies such as lycopene and CBD)

As you can see, supercritical CO2 extraction technology offers significant advantages in the industry and will surely be one of the technologies to focus on for the future, as it provides many benefits that old traditional technologies are no longer able to offer. Product quality, process safety, and sustainability are probably the most important advantages, but they are not the only ones.

If you are a business owner and wish to harness all the potential of CO2 extraction technology, for example, in the cosmetics or pharmaceutical industry, feel free to contact us for consultation. Fill out the form below, and we will be happy to assist you in your process of upgrading extraction processes

The extraction of compounds from natural matrices is the most studied application of supercritical CO2, with several hundred scientific papers published. In fact, supercritical CO2 extraction (SFE) has many advantages over traditional extraction techniques with organic solvents:

• È un sistema flexible process that allows continuous modulation of the solvent power and therefore the selectivity of the supercritical fluid.
• It allows the complete replacement of polluting organic solvents, which are complex to manage.
• It allows the simplification of the expensive secondary phase, both in terms of time and cost, necessary to purify extracts from unwanted substances like vegetable waxes.

Process engineers know that there are two of the most complex (and expensive) problems they face every day:

• The elimination of the solvent used for extraction.
• The elimination of unwanted substances.

In the first case, the elimination of the solvent occurs (almost like magic) simply by decreasing the pressure to bring the solvent from the supercritical state to the gaseous state, avoiding the huge gasification costs necessary in thermal processes when liquid solvents are used. In the second case, the great selectivity of the supercritical process and the presence of separators for the extract from the solvent (returned to the gaseous state) allow for very pure extracts, in some cases immediately marketable.

 The advantages of supercritical CO2 compared to a liquid solvent can be summarized as follows:

• Greater transport speed of extracts in plant extraction processes, close to that of gases.
• Viscosity many orders of magnitude lower than liquid solvents.
• Diffusion coefficient in the material to be processed is many orders of magnitude greater than that of liquid solvents.
• Very fast permeability of the solvent (CO2 in the supercritical state) in the matrix with a drastic reduction of the process time.
• Low solvent costs: CO2 in this case is recycled by suppliers by “capturing” it in transformation processes, such as the production of fertilizers and manures, or is recycled by capturing it in wells where it is of geothermal origin.
• CO2 is non-toxic, non-flammable.
• Extraction and separation of compounds in a single process with a reduction of costs and times of both the main process (extraction of compounds) and the secondary process (solvent recovery and continuous reuse and in the same process of CO2 “cleaned” from the extracts).

Selectivity in the extraction of compounds through the modulation and modification of the solvent power by varying the operating conditions of pressure, temperature, and flow rate.

The absence of organic solvents used in the extraction guarantees the safety of the extracts, making them available in their pure state and in concentrated form. For this reason, the FDA has awarded the supercritical CO2 extraction process the GRAS attribute (Generally Recognized As Safe). Unfortunately, in the all-too-recent past, the presence of organic solvent residues in extracts has caused significant health problems for consumers. Fortunately, current legislation prohibits the use of organic solvents, such as hexane, which have carcinogenic and mutagenic characteristics.

The absence of residues in the extract and the purity of the extract makes supercritical CO2 the best choice for producing high-quality and safe extracts for the consumer.

In this article, we have seen, therefore, that the supercritical CO2 extraction process offers many advantages in terms of product quality and safety.

If you are in the leadership of a cosmetic or nutraceutical industry, or if your organization is in the food sector and you want purer and higher-quality extracts, contact us for a consultation by filling out the form below. We will be happy to help you identify and implement the right machinery for supercritical CO2 extraction.

The extraction of compounds from natural matter is the most well-known application of supercritical CO2 technology. First used in an industrial application in 1970 by German scientist Kurt Zosel (credited with the first US patent), it was employed to extract caffeine from coffee beans. The use of supercritical CO2 has revolutionized extraction processes by eliminating the need for organic solvents, replacing them with a sustainable and environmentally friendly technology.

Over the last 50 years, the supercritical CO2 extraction process (SFE) has undergone significant transformations. This is due to the use of high-efficiency separators capable of isolating extracted compounds during the extraction process into various collection vessels. The key distinction lies in the simultaneous occurrence of the secondary process, where the extracted compounds are separated, with the primary extraction process, eliminating additional costs and working time compared to traditional extraction technologies using organic solvents like ethanol.

With supercritical CO2 extraction technology, not only can compounds of interest be extracted from the matrix, but CO2 can also be removed, causing the pure extract to precipitate into the separator. Over time, multiple separation systems (2, 3, or 4 vessels) with different engineering solutions (gravimetric and cyclonic) have been developed. These systems introduce new process solutions that enhance the separation of extracted compounds while maintaining a supercritical state in the initial separation vessels—a state similar to that of the extraction but under different process conditions, selectively choosing different compounds in each separator.

The introduction of automation has significantly contributed to the widespread adoption of this technology. It’s essential to note that the supercritical state of CO2 is inherently unstable and requires continuous involvement from the automatic process control system. Specialized software-controlled processes have eliminated the need for specialists, making supercritical CO2 extraction accessible to a broader audience. Experts identify process conditions and input data into program recipes executed by automation software.

When it comes to safety, numerous aspects need consideration. Safety comes first, and the design of a supercritical CO2 system relies on a profound understanding of engineering and organic chemistry. However, this is not sufficient; extensive process experience is crucial to guide the design effectively.

Calculation codes assist engineers in correctly sizing every part of the machine, ensuring each component’s safety and ability to withstand CO2 pressure. Every part is certified by the manufacturer’s certifying body according to current regulations, even if these regulations vary worldwide. For instance, in Europe, the Pressure Equipment Directive (PED) directives apply, while in North America, the American Society of Mechanical Engineers (ASME) directives apply. Therefore, machines built and certified for North America cannot be used in Europe and vice versa.

Once all parts are assembled, the entire assembly undergoes certification by an independent certification company. This guarantees not only that all parts are designed and certified for required pressures but also that the machinery as a whole complies with international engineering directives. The certification company inspector doesn’t merely witness the verification test but follows the manufacturer from the initial draft of the Pipe and Instrument Diagram (P&ID), the project scheme describing how all individual parts connect. All these checks ensure the safety of the built machinery, protecting the operators who will use it.