In the quest for sustainable solutions, scientists are turning nature's own chemistry into powerful tools for unlocking precious oils.
Imagine a world where the process of extracting valuable oils from plants doesn't harm the environment or leave toxic residues. This vision is becoming reality through green solvents—innovative, eco-friendly alternatives that are transforming how we obtain essential oils, nutritional oils, and bioactive compounds.
Traditional methods often rely on petroleum-based solvents like n-hexane, which pose significant health and environmental risks. Today, researchers are looking to nature's own chemistry to develop sustainable extraction techniques that work in harmony with our planet while maintaining high efficiency and yield.
Derived from renewable resources with minimal environmental impact.
Superior extraction capabilities compared to conventional solvents.
Reduced health risks for workers and consumers.
For decades, the go-to solvent for oil extraction has been n-hexane, a petroleum-based chemical prized for its simple recovery, non-polar nature, and high selectivity 1 . However, this conventional approach comes with significant drawbacks:
During extraction and recovery processes, hexane is released into the environment where it reacts with pollutants to form ozone and photochemical smog 1 .
Studies have shown that hexane affects the neural system when inhaled by humans due to its solubility in neural lipids. Toxicity has even been observed in piglets fed with defatted meal containing residual hexane 1 .
Hexane is highly flammable and volatile, creating workplace hazards 6 .
Green solvents are characterized by their low toxicity, biodegradability, and reduced environmental impact. They're derived from renewable resources rather than petroleum, marking a significant shift toward sustainable extraction practices 8 .
Terpenes are organic compounds derived chiefly from agricultural sources, representing a promising category of bio-based solvents 1 .
Ionic liquids are non-aqueous salt solutions that remain liquid at moderate temperatures (0–140°C) 1 . These innovative fluids are considered "designer solvents" because they can be tailored for specific applications.
Recent research has highlighted 2-methyloxolane (2-MeOx) as a particularly promising bio-based solvent.
In a 2025 study on camellia seed oil extraction, 2-MeOx outperformed both n-hexane and subcritical n-butane 5 .
Water, the "universal solvent," is gaining new traction in extraction technologies, particularly when used in subcritical or supercritical states 8 .
Supercritical COâ‚‚ extraction uses carbon dioxide at critical temperature and pressure conditions, making it an ideal solvent for sensitive compounds without leaving harmful residues .
Innovative technologies are being developed to work synergistically with green solvents, enhancing efficiency while reducing environmental impact.
This innovative approach uses water as a medium combined with specific enzymes to break down plant cell walls and release oil bodies 1 . The process is particularly elegant because it mimics nature's own decomposition methods.
This innovative approach applies compression-decompression cycles to modify plant structure and enhance heat and mass transfer 4 .
ASE uses organic solvents at high temperatures and pressures to quickly and efficiently extract analytes from solid matrices 3 .
This technique enhances extraction efficiency by using microwave energy to increase solvent penetration into plant matrices through dipolar rotation .
Maximum Oil Yield
Reduced Extraction Time
Lower Solvent Consumption
A groundbreaking 2025 study directly compared the effectiveness of green solvents versus conventional methods for extracting oil from camellia seed cake 5 .
Researchers prepared camellia seed cake powders and subjected them to extraction using five different solvents:
Extractions were performed at room temperature with a solid-to-liquid ratio of 1:10 (w/v) for 1.5 hours 5 .
The study revealed compelling advantages for green solvents, particularly 2-MeOx:
| Solvent | Extraction Ratio (%) | Total Phenolic Content (mg GAE/kg dw) | COâ‚‚ Emissions (kg) |
|---|---|---|---|
| n-Hexane | 89.50 ± 0.00 | Not reported | Not reported |
| Subcritical n-butane | 83.75 ± 0.43 | Not reported | Not reported |
| 2-Methyloxolane (2-MeOx) | 94.79 ± 0.00 | 351.6 ± 0.02 | 0.38 ± 0.07 |
The kinetic studies demonstrated that 2-MeOx had the highest diffusion rate at both temperatures tested, explaining its superior extraction performance 5 .
| Solvent | Diffusion Rate at 25°C | Diffusion Rate at 55°C |
|---|---|---|
| n-Hexane | Baseline | Baseline |
| 2-MeOx | Highest | Highest |
| CPME | Intermediate | Intermediate |
| Ethyl acetate | Lower | Lower |
| Reagent Category | Specific Examples | Function in Extraction | Derivation Source |
|---|---|---|---|
| Terpenes | d-Limonene, α-Pinene, p-Cymene | Lipid dissolution, replacement for hydrocarbon solvents | Citrus peels, pine forests, tree oils 1 |
| Ionic Liquids | Various cation-anion combinations | "Designer solvents" with tunable properties for specific extraction needs | Synthetic production 1 8 |
| Bio-based Ethers | 2-Methyloxolane (2-MeOx), Cyclopentyl methyl ether (CPME) | Lipid extraction with high efficiency and low environmental impact | Renewable biomass 5 |
| Enzymes | Protease, Cellulase, Pectinase | Breakdown of cell wall components to release oil bodies | Microbial fermentation 1 |
| Supercritical Fluids | COâ‚‚, Water | Solvents with tunable polarity and zero residue | Natural abundance 8 |
| 3-Benzoyl-5-hydroxyflavone | Bench Chemicals | Bench Chemicals | |
| Lutetium--palladium (3/4) | Bench Chemicals | Bench Chemicals | |
| Hexamethylpropanediamide | Bench Chemicals | Bench Chemicals | |
| 5,9-Dioxodecanoic acid | Bench Chemicals | Bench Chemicals | |
| 2,2,3-Trimethyl-3-oxetanol | Bench Chemicals | Bench Chemicals |
The transition to green solvents represents more than just an technical improvement—it's a fundamental shift toward sustainable manufacturing practices that align with the principles of circular economy and environmental stewardship.
Selection of varieties and use of renewable plant resources
Use of alternative solvents, principally water or agro-solvents
Energy recovery and using innovative technologies
Instead of waste to include the bio-and agro-refining industry
Favour safe, robust and controlled processes
Aim for biodegradable extract without contaminants 6
As research continues, we can expect to see further optimization of existing technologies and discovery of novel green solvents with even better profiles for efficiency, safety, and sustainability.
The integration of digital tools for solvent selection and process optimization will further accelerate this transition 7 .
The green revolution in extraction technology demonstrates that we don't have to choose between efficiency and environmental responsibility. By harnessing nature's own chemistry, we can develop processes that are both effective and ecological—ensuring that the products we derive from plants don't come at the cost of a polluted planet.