Writing in Current Opinion in Colloid & Interface, researchers from Japan’s Tokyo University of Science outlined overall progress in the development of sustainable surfactants and provided a future perspective of development and demand in a review.
Sustainable surfactant demand ‘bound to increase’
Surfactants – one of the most abundantly used chemical commodities in the world – formed an important part of many hair care, oral care and cosmetic formulations; used for cleansing, foaming, thickening, emulsifying, solubilising, penetration enhancement and even antimicrobial effects. Conventional surfactants were generally derived or manufactured using petrochemical feedstock or a combination with renewables thereof and sustainable surfactants – also known as biosurfactants or green surfactants – were derived from renewable raw materials.
Writing in the review, the researchers said global demand for surfactants was growing at 3-4% per year, therefore demand for sustainable surfactants was “bound to increase in coming years”.
“…The ever-increasing demand of surfactants in several application areas necessitates development of many new structural analogs of these molecules by sustainable approach,” the researchers wrote.
Advances in renewables – plant oils, fatty acids, terpenes and sugars
And the researchers said there had been plenty of product development in the field, with numerous eco-friendly surfactant-based products launched worldwide in recent years, by large and small chemical suppliers and personal care firms.
These developments, they said, had largely been fuelled by an “increasing consumer awareness” around sustainability, along with obligations issued by the likes of the United Nations for more sustainable business development worldwide.
“…In recent years, environmental concerns coupled with increased consumer awareness have guided substantial growth of environmentally benign surfactant molecules often termed ‘green surfactants’, ‘oleochemical-based surfactants’, ‘renewable surfactants’, ‘biosurfactants’, ‘natural surfactants’, and so on,” they wrote.
And these new generation sustainable surfactants were being directly or indirectly derived from a vast array of renewable building blocks, they said.
Plant or nut oils was one strong example, the researchers said, though concerns had been raised around deforestation and price spikes associated with too much focus on this source; microbial lipids could be considered an emerging, alternative renewable to these.
Natural molecules such as glycerol, amino acids and sugars were also strong options for the development sustainable surfactants, they said, with biobased or synthesised variants increasingly in the spotlight.
Fatty acids and terpenes were also being used to produce sustainable surfactants, the researchers said, with increasing interest in unsaturated fatty acids like oleic acid and erucic acid amidst this “emerging trend”. Terpenes from lemon grass, rose and citronella, among other plants, were also being considered and used in applications.
The researchers said that sustainable surfactants made using these renewable building blocks boasted better degradation properties than conventional surfactants overall and had low toxicity, making them a “popular choice for designing new formulations for industrial and consumer use”.
Use of these renewable building blocks also helped reduce CO2 emissions because after degradation, only the quantitative amount of carbon previously consumed by the plant or natural source was released. Close consideration, however, had to be given to concerns associated with deforestation and wildlife damage when sourcing certain renewable building blocks such as palm kernel and coconut oil, they said.
Cost and performance still unmatched
However, the researchers said that despite significant advances made in the field of sustainable surfactants, and continued progress ongoing, it remained “very difficult to completely replace conventional surfactants”.
“…The former category of surfactants will continue to dominate [the] consumer market because of their low cost and proven performance in many application areas,” they concluded.
Source: Current Opinion in Colloid & Interface
Published online ahead of print, doi: 10.1016/j.cocis.2020.01.002
Title: “Current perspective of sustainable surfactants based on renewable building blocks”
Authors: A. Bhadani et al.