Green solvents: an interesting alternative for a greener chemistry

What is the role of solvents?

Solvents have the ability to dissolve, disperse, separate or transport other substances. In other words, their functions are so broad that they are found around us almost everywhere. They can be used in chemical reactions as a reaction medium, in the food industry as an extraction agent or flavoring agent, in the paint industry as a cleaner, in the transportation industry as a component of biofuel, or in cosmetics as a texturizer or dissolver.

4 ways of using solvents for a greener chemistry

With such a wide range of applications, more than 28 million tons of solvents are used each year. Given their potentially high toxicity and carbon footprint, this class of chemicals represents a major opportunity for sustainable and greener chemistry^[1] .

1st option towards greener solvents: remove them and adapt the process accordingly

In line with the principles of green chemistry, the first option would be to exclude, wherever possible, or reduce solvents. Numerous tools have been developed to help manufacturers identify the right solvent for their needs based on its properties and toxicity, for example the guide developed by CHEM21 (European public-private partnership for the promotion of sustainable pharmaceuticals).

Option 2: replace them with more environmentally friendly and cost-effective alternatives when they cannot be eliminated

In some cases, solvents are essential and cannot be excluded. In these situations, one solution would be to replace organic solvents with less hazardous and less toxic solvents, called green or solvent alternatives. An sustainable solvents should ideally be:

• Efficient: With similar or better properties than conventional solvents, and cost-effective.
• Safe: Less dangerous to produce and handle (no risk of fire or explosion), non-toxic to human health.
• Renewable: Manufactured from a biobased raw material, of renewable origin (waste, by-products or low footprint biobased materials).
• Sustainable: No negative impact on the environment, ideally fully biodegradable, or at least recyclable/reusable.

Learn more about the issues related to biobased materials >

Option 3: Select biobased raw materials and optimize processes to make solvent production more environmentally friendly

The production of conventional solvents (or organic solvents) is often petroleum-based (unlike biobased solvents) and can have a high carbon footprint. The transition from fossil sources to plant biomass, in the case of green solvents, is one of the key aspects to mitigate the carbon footprint of solvents, but also to reduce our dependence on fossil sources (not environmentally friendly and subject to high price volatility).

A wide variety of biobased materials can be used to provide better alternatives, for example by taking advantage of oilseed production (rapeseed, soybean, sunflower), grain production (corn, sugarcane, beet sugar) or wood and pine by-products. Intensive research is being conducted to expand and improve this conversion of plant biomass, including the use of by-products or waste as bio-based materials. The issue to keep in mind is to ensure that this feedstock will be available, consistent and reliable in the long term, without competition with food production.

Option 4: Reduce solvent toxicity and increase biodegradability to make solvent use more environmentally friendly

Solvents can be toxic to humans and dangerous to handle. If not used properly, chemicals can enter the body through the respiratory, skin or digestive tract and cause a variety of illnesses and health problems in work crews. As they can also pose a risk to the environment, their biodegradability and impact on biodiversity are other aspects to be improved.

What is the best green solvent?

There is no “perfect green solvent”, but the fact is that the family of solvents is very broad and versatile.

There is no one-size-fits-all answer, and each solvent must be evaluated as part of a process, with a tailored approach.

In fact, there is no such thing as an entirely “green” solvent. It is essential to take a holistic approach to the entire chemical process (considering production, recycling, by-products or waste, but also use and life cycle assessment within the process) and not the molecule itself without considering its use. There is no one-size-fits-all answer, and each solvent needs to be evaluated within a process, with a tailored approach.

Here is an example of a green solvent with water. One might think that water is one of the most environmentally friendly solutions available. However, this is not always the case, as it depends on how it is used. Due to its high boiling point, water requires a considerable amount of energy to evaporate, which ultimately leads to the production of CO2. Whereas another, less “green” solvent might require less energy and lead to less CO2 in the atmosphere. Moreover, water is a key resource on which demand and competition are high, its long-term availability must be taken into account.

Another example of interesting solvent alternatives is supercritical fluids. These are fluids that are compressed or heated to a certain point to develop specific properties that combine the characteristics of fluids and gases. These properties make them excellent solvents for the extraction of specific molecules (used in food decaffeination or sterilization, for example). They are highly adjustable, have no residues and are easily recycled and reused (good tox/ecotox profile). However, they cannot yet be adapted to all applications, as their properties (including biodegradability) vary greatly depending on the type of fluid, making their effectiveness entirely correlated to their application.

How can we effectively ensure the development of innovative green solvents?

The development of innovative green solvents requires further collaboration and partnerships between academia and business for effective developments and successful scale-ups.

“Sustainable consumption and production requires a systematic approach throughout the life cycle of chemicals and cooperation between actors and sectors along the supply chain, from producers to end consumers^[2] .”

According to, SAICM, the development and scale-up of an innovative technology or family of chemicals is most successful when academics and companies partner around a common goal. A growing number of technology transfer acceleration organizations are being created to support this type of collaboration and ensure that all industry requirements are addressed as early as possible, even at the laboratory stage.

Green solvents are an important chapter in the ongoing work for sustainable and greener chemistry. Ideally removed from the process, they can also be replaced by greener alternatives, for example from sustainable and renewable resources. However, there is no such thing as a “perfect green solvent,” and intensive work is being done by both academics and industry. The main difficulty is that the family of solvents is very large and versatile: there is no universal answer to everyone’s needs, and each solvent must be evaluated in a holistic process, with a tailored approach.

In this context, Alcimed believes that the development of innovative green solvents requires further collaboration and partnerships between academia and industry for the ideation, development and scale-up of production of efficient technologies and products. Alcimed can assist you in the process of selecting the right solvents for your needs, and identifying partners for their development and commercialization. Don’t hesitate to contact our specialized team in biobased materials!

[1] Winterton, N. (2021). The green solvent: a critical perspective. Clean Technologies and Environmental Policy, 23(9), 2499‑2522. https://doi.org/10.1007/s10098-021-02188-8

[2] Sustainable Development Goals. http://www.saicm.org/Default.aspx?tabid=7654

About the author, 

Ondine, Consultant in Alcimed’s Life Sciences team in Switzerland