Switching to sustainable surfactants

Personal care is going green at a breakneck pace. While most industries, including the chemical industry, are targeting net-zero greenhouse gas emissions by 2050, the consumer product brands that make soap, shampoo, lotion, and cosmetics are setting their sustainability goals at 2030, just 8 years away.

Those goals are also broader than just carbon dioxide emissions. When people buy personal care products, brand owners say, they are also looking for biodegradability, low environmental impact, and supply chains that are sustainable and ethical. Biobased is the keyword that consumers want to see on a product to know it meets those standards.

“What we are seeing, and have seen in the last few years, is that natural components are becoming a bigger driver of consumer behavior within the beauty and personal care category,” says Andrew McDougall, director of beauty and personal care for the market research firm Mintel. He says 98% of UK consumers bought “ecofriendly” beauty and personal care products in 2021, and natural ingredients are the top priority for 82% of Chinese beauty and personal care shoppers.

Surfactants are a prime target ingredient for making products more natural. These molecules play a central role in all types of personal care products, providing the grime-and-grease-removing power of face and body washes and holding disparate chemical phases together in lotions and makeup. Many surfactants also help moisturize and smooth skin and hair.

“It is a good time to be selling new ingredients,” says Neil Burns, a surfactant consultant and CEO of the personal care ingredient maker P2 Science. Personal care brands are “more receptive than I’ve seen them in a long time,” he says.

That atmosphere comes largely from the 2030 greenhouse gas emission targets set by many major consumer product companies, Burns says. “Big, big household names—the Procter & Gambles, Unilevers, L’Oréals—it’s all over their websites very publicly committing to some pretty ambitious goals regarding sustainability,” he says. “Given the scale of the commitments and given today’s slate of readily available raw materials and ingredients, they can’t get there from here. They need new stuff.”

But what are their options for that stuff, and which are the best for the planet? As they seek to replace synthetic surfactants with greener, low-carbon-footprint alternatives, consumer product makers have three main categories to choose from: microbial biosurfactants, inherently biobased surfactants, and biobased versions of conventional surfactants. The decisions they make will create winners and losers in the chemical industry and could have a lasting impact on our environment.

Microbial biosurfactants

Chemically speaking, surfactants are molecules that have both hydrophilic and hydrophobic sections. Soap, the old standby, has a carboxylic acid head attracted to water and a long hydrocarbon tail attracted to oil. Many other natural, synthetic, and semisynthetic molecules can do the same tricks with different combinations of polar and fatty molecular motifs.

The term biosurfactant refers to glycolipids produced by certain microorganisms. The water-soluble head in a biosurfactant is a sugar group, and the oil-soluble tail is a long, mostly saturated hydrocarbon chain. In nature,microbes use glycolipids for quorum sensing, adhesion, lubrication, and competition with other microorganisms.

The two most commercially advanced biosurfactants are rhamnolipids and sophorolipids, which feature rhamnose and sophorose, respectively, in their sugar heads. Within each of those families, structural variations can alter the surfactant’s properties.

The hydrocarbon tail of sophorolipids, for example, can either flop around loosely and terminate in a carboxylic acid or loop around and attach to the sugar head, creating a lactone ring. The lactone form is less foamy, explains Lawrence Clarke, a technical sales manager at Holiferm, a British glycolipid fermentation company.

Biosurfactants aren’t new; references in the chemical literature date back to the 1950s. But they’re newly available to the commercial market. A few home and personal cleansers, such as Booni Doon’s powdered facial cleanser, already feature biosurfactants.

The strongest indicator of the interest in biosurfactants is the pace of dealmaking. A few days before In-cosmetics Global, a trade show for personal care ingredients held in Paris during the first week of April, Holiferm signed a deal in which the chemical company Sasol will buy most of the sophorolipids produced at a plant Holiferm plans to open in 2023 in the UK.

According to Louis Snyders, Sasol’s global director of fabric, home care, and institutional and industrial cleaning, the deal brings products that complement Sasol’s existing portfolio of surfactants, and it is a step in transforming that portfolio from its petrochemical heritage to a sustainable future.

Holiferm uses a strain of yeast, which it isolated from honey, that consumes sugar and sunflower oil to make the target surfactant. Clarke says the firm’s semicontinuous process, which extracts sophorolipids throughout weeks-long fermentation runs, sets it apart from companies that use batch production methods.

BASF, a Sasol competitor, also has a deal with Holiferm and a controlling interest in the Japanese sophorolipid maker Allied Carbon Solutions. Nader Mahmoud, vice president of North American personal care business management at BASF, says the firm “intends to lead on biosurfactants.” He says the Holiferm collaboration targets process development and manufacturing, with a focus on rhamnolipids and mannosylerythritol lipids (MELs), an emerging category of glycolipid surfactants.

Earlier this year, the surfactant fermentation specialist Locus Performance Ingredients signed a similar agreement to supply Dow with sophorolipids for the home and personal care markets. Isabel Almiro do Vale, Dow’s global marketing and strategy director for personal care, says the scale-up and distribution incorporated into the deal will “democratize access to sophorolipids.”

And in January, Evonik Industries announced plans to build a rhamnolipid plant in Slovakia at a “three-digit­-million-euro” cost. Unilever is already on board as a customer, and Evonik representatives at In-cosmetics said buyers at the meeting were asking for the ingredient. Evonik had rhamnolipids on hand in a sample formulation of a facial cleanser cream.

The activity by chemical majors like Evonik and Dow has brought biosurfactants to the cusp of the personal care mainstream, according to Burns. “Those companies have sort of lent the field a little bit of commercial credibility,” he says, and they “bring some scale that I think ultimately will help bring costs down.”

Beyond being biobased, biosurfactants have a lower carbon footprint than conventional surfactants such as sodium lauryl ether sulfate (SLES), a common ingredient in personal care products, according to Dan Derr, a bioprocessing expert who helped develop the rhamnolipid technology Stepan acquired in 2020. That CO₂ advantage comes mostly from the mild conditions of fermentation, which is carried out at ambient temperature and pressure.

SLES is usually made by reacting fatty alcohols derived from palm oil with ethylene oxide and sulfur trioxide. Those steps consume a lot of energy because they take place at elevated temperatures and pressures. And though the oil component is biobased, palm oil is fraught with sustainability concerns of its own, including the deforestation required to build palm farms and greenhouse gas emissions from the leftover woody plant matter.

According to Clarke, a life-cycle analysis commissioned by Holiferm concluded that replacing 1 metric ton (t) of a typical ethoxylated surfactant with 1 t of sophorolipids would reduce greenhouse gas emissions by 1.5 t of CO₂. Biosurfactants are also more potent by some measures than SLES and most other options, making it possible to use less in a final formulation.

“Fermentation becomes a really interesting process versus synthetic chemistry just because of the energy consumption,” Almiro do Vale says. But because the feedstocks for biosurfactants today are sugars and oils, agricultural practices have a huge impact on sustainability. “You need to make sure that you’re tracking really well your supply chain for the fermentation,” she says.

Biosurfactant fermentation expert Sophie Roelants takes that concern a step further. She says a cradle-to-grave environmental analysis reveals that this first generation of biosurfactants is only marginally better than other types of surfactants. “The main reason is that you are dependent on agriculture to produce your feedstocks, and agriculture is really bad for the environment.” Her conclusion is different from Holiferm’s, Roelants says, because of how far back in the production process she starts counting carbon.

Roelants estimates that 80% of the net carbon emissions from biosurfactants happen while growing the feedstock. Seeing an opportunity, she recently cofounded the company Amphi-Star to commercialize biosurfactants made from industrial and food waste. The firm, a spin-off from Ghent University and the nonprofit Bio Base Europe Pilot Plant, is looking for partners to help it scale up and improve process efficiency.

Inherently biobased

Other biobased surfactants—made by chemically modifying and combining molecules extracted from plants—have been available for years but are now enjoying increased interest from personal care brands.

The most popular class in this category is alkyl polyglucosides, or APGs. Chemically similar to microbial glycolipids, APGs are made by combining glucose or other sugars with fatty alcohols derived from plant oils. The reaction is driven by inorganic catalysts or enzymes. Like biosurfactants, APGs are milder and generally have a lower carbon footprint than conventional surfactants.

APGs are not a slam dunk for personal care products, however, because they cost more and aren’t as foamy. According to sales representatives from Colonial Chemical who were at In-cosmetics, APGs cost two and a half to three times as much as SLES. Foaming doesn’t actually improve personal care cleansers’ effectiveness much, but people see bubbles as a sign of efficacy.

Though not as popular as SLES and related ethoxylated ingredients, APGs are already widespread in personal care. Marcelo Lu, BASF’s senior vice president for care chemicals in North America, says BASF is working with some global brands on “chassis change”—reformulating products around APGs and other inherently biobased surfactants. “We’re talking about major volumes,” he says.

“In a way, we were a bit ahead of our time,” Lu says, noting that BASF has produced APGs for decades. “But because of regulatory forces and also the focus on biobased content, you see a lot of brands now paying more attention.”

“We’ve flipped quite a few formulations already. And I think we are in the beginning stage of this,” Lu says. “We may get into a supply constraint if everybody starts switching.”

BASF has APG plants in the US, Asia, and Europe and is looking to expand capacity, according to Lu. Other suppliers, such as Solvay, Dow, and Colonial, also offer APGs at commercial scale. For delivering low-CO₂, biobased surfactants at the scale needed to support the green ambitions of global brands, “APGs are the closest,” Lu says.

Conventional, but biobased

Even with help from suppliers, reformulation to accommodate new ingredients is not trivial; it’s expensive and risky for a brand owner to change a product line that already works. Avoiding reformulation is the value proposition that some major chemical companies are bringing with biobased versions of conventional surfactants.

Especially in personal care, many workhorse surfactants, such as SLES, are already partially biobased. Roughly half the carbons in an ethoxylated, vegetable oil–based surfactant have biomass origins.

Two chemical makers, Croda International and Clariant, have made a change allowing them to get to 100% biobased: they are deriving their ethylene oxide from plants instead of fossil resources. Croda launched its Eco range of surfactants in 2018, and Clariant’s Vita-branded surfactants and polyethylene glycols came out in February of this year.

The chemistry used by both was developed primarily by the New Jersey–based engineering firm Scientific Design. The process starts by dehydrating plant-derived ethanol into ethylene. The subsequent steps of oxidizing ethylene to ethylene oxide and then creating ethoxylated surfactants are the same as in the synthetic route, though Scientific Design offers systems that integrate all three steps.

Both Croda and Clariant say the production lines for their biobased ethoxylated surfactants are fully segregated from those of their conventional counterparts, and they offer customers carbon isotope data to prove that no petroleum carbon is mixed in. Fossil carbon doesn’t contain the heavy carbon isotope ¹⁴C, whereas biobased carbon does, so the amount of ¹⁴C in a sample can indicate where its carbons came from.

Although consumers value the labels that such biobased products permit, for environmental advocates, being plant derived is not as central a goal as it once was. A lot of the talk around sustainability in the chemical industry today is about carbon emissions, and the CO₂ benefits of biobased ethylene oxide are not cut and dried.

According to a life-cycle analysis published by Clariant, making a kilogram of ethylene oxide from fossil fuels emits the equivalent of 1.5 kg of CO₂. Making that same kilogram from ethanol emits slightly less, 1.4 kg of CO₂. But the biomass that’s fermented into ethanol absorbs 2.0 kg of CO₂ from the air as it grows, Clariant says. So from corn or sugarcane to ethylene oxide, the process is carbon negative to the tune of 0.6 kg of CO₂ per kilogram of ethylene oxide.

But that number does not count the greenhouse gas emissions associated with growing the biomass. And in the case of corn and sugarcane, those emissions can be substantial. Debates on the environmental impact of producing ethanol from edible sugars have raged since Brazil began blending ethanol into gasoline in the 1970s.

David Schwalje, head of emerging market development for the fuel and chemical engineering firm Axens, says the provenance of the ethanol feedstock makes all the difference when it comes to measuring the carbon intensity of the resulting products. Ethylene oxide made from conventionally grown corn or sugarcane alcohol—often called first-generation ethanol—isn’t reliably better from an emission standpoint than ethylene oxide made from petroleum, he says.

A look at some publicly available numbers shows how widely the carbon footprint can range for the compound. The carbon emissions of growing the corn needed to produce a kilogram of biobased ethylene oxide—including from fertilizer production, truck and tractor fuel, and other emission sources—were between 0.8 and 2.8 kg of CO₂, according to C&EN calculations based on estimates from Argonne National Laboratory and the University of Minnesota (Biofuels, Bioprod. Biorefin. 2021, DOI: 10.1002/bbb.2225; Proc. Natl. Acad. Sci. U.S.A. 2017, DOI: 10.1073/pnas.1703793114). Factor in Clariant’s numbers on ethylene oxide production, and the biobased route offers anywhere from an 86% reduction to a 46% increase in CO₂ emissions relative to the petrochemical route.

However, Schwalje says, second­generation ethanol made from waste or sustainably grown cellulose where the fermentation and distillation equipment uses carbon capture can be massively carbon negative and carry that CO₂ advantage downstream to the products made from it.

Both Croda and Clariant are using first-generation ethanol, for now at least. Croda makes its Eco products from corn-based ethanol at a $170 million, purpose-built plant in Delaware that has a capacity of roughly 30,000 t per year. The plant is powered by methane captured from a nearby landfill, reducing the carbon footprint of the ingredients produced there, the firm says.

Clariant’s sugarcane- and corn-based plant is in Uttarakhand, India, part of a joint venture with India Glycols. Fabio Caravieri, head of global marketing for Clariant’s industrial and consumer specialties division, says the firm has “double-digit kilotons” of its Vita products available. “It’s not something where we are doing an investment today that in 2 to 3 years will be available to the market. It’s now,” he says.

Just using biobased ethylene oxide is not going to make a shampoo or body wash carbon negative, Caravieri acknowledges, but it does offer an improvement. Clariant says that because of the specific feedstock and equipment at the plant in India, a consumer product maker can claim a carbon footprint reduction of up to 2 kg of CO₂ for every 1 kg of surfactant.

And Clariant is in a position to do more. The firm operates one of the world’s only second-generation ethanol plants, a 50,000-t-per-year facility in Romania that started making ethanol from straw in 2021. That cellulosic ethanol could become a feedstock for Vita products in the future, Caravieri says, if such a combination looks profitable once the firm has more experience with both products.

The mass-balance way

Other major chemical firms active in surfactants are meeting the demand for renewable carbon content through an accounting approach known as mass balance. As with the ethanol-based ethoxylates, the surfactants made through this method are chemically identical to what is already on the market. But the mass-balance approach introduces the biomass further upstream. It is blended with fossil-carbon feedstocks like naphtha or natural gas as those substances are fed into the crackers that make ethylene and other building-block chemicals.

Mass-balance accounting methods vary, but the basic idea is that an operator gets credits for each biobased carbon atom fed into its cracker. It can assign those credits to a portion of the plant’s output containing the same number of carbon atoms. Customers that want to buy from the biobased portion pay the market rate for the conventional chemical plus a supplement for the biomass, or renewable, carbon.

For example, if a company makes 100 kg of a surfactant using a raw material with 10% renewable content, it can claim that 10 kg of the surfactant is 100% renewable under the mass-balance concept, even though really all 100 kg have 10% renewable content.

As of January, Sasol is offering mass-balance surfactants and other chemicals to its customers in Europe by buying ethylene made with enough renewable carbon to meet its mass-balance orders from customers. Operating that way offers nimbleness and scalability that new ingredients and segregated facilities do not, Snyders says. Sasol makes a wide range of chemicals from the same handful of building blocks, so changing which products get credited with the renewable carbon is just a matter of bookkeeping.

Sasol started with thousands of metric tons of mass-balance SLES and plans to quickly expand to tens of thousands, Snyders says, though Russia’s invasion of Ukraine has slowed the timeline. He says mass-balance offerings are a first step and one Sasol can take now. Long term, he says, the hope is to create feedstock-­segregated offerings by converting entire units to recycled and biomass-carbon sources.

The biomass supply chain needs work before that’s even feasible, however. For example, Sasol has capacity for around 400,000 t per year of ethylene oxide in Lake Charles, Louisiana. Snyders says it’s impossible right now to supply a whole facility of that size with biomass feedstocks suitable for use in petrochemical equipment.

Sasol isn’t the only fan of mass balance. At the end of March, BASF and the consumer product maker Henkel signed a deal in which 110,000 t per year of the ingredients BASF makes for Henkel in Europe will be manufactured with renewable feedstocks on a mass-balance basis. The firms say the move will lighten the carbon footprint of Henkel brands, including Persil, Pril, and Fa, by 200,000 t over the 4 years of the supply contract.

Despite the logistic advantages of mass balance, the approach doesn’t convince all end users. Mass-balance certification abbreviations such as ISCC and REDcert² don’t mean much to the lay consumer. And even if the mass-balance bookkeeping is legitimate, the carbons in the final product are a mix of plant based and fossil sourced, and that’s not what many shoppers want, Mintel’s McDougall says.

Ivo Grgic, Henkel’s global purchasing category manager for surfactants, acknowledges the concerns, but he says mass balance is the fastest next step the firm can take to make its products more sustainable. “We clearly decided we want to deliver a contribution today, now. That doesn’t mean that we are going to close the door for these new technologies in the next years. Not at all. But we need to start.”

Grgic says the 110,000 t from BASF is a big chunk of Henkel’s overall annual ingredient volume for consumer brands in Europe, and surfactants are the biggest portion of the deal. Adding mass-balance purchases in other parts of the world will be next.

“We are a company producing big, big, big volumes,” Grgic says. “From our point of view, we need to make an impact, and we decided that biomass balance is the approach where we can replace fossil carbon on a big scale in the fastest way. Other technologies, like CO₂ capture and biosurfactants­—they will follow in the next coming years.”

Consumer product brands looking to go biobased have options: new ingredients like glycolipids, expanded use of specialty ingredients like APGs, and newly biobased versions of the ingredients they’re used to. But the choices involve a complex balance of sustainability, efficacy, availability, and of course, cost. Caravieri says ecoconscious consumers are willing to tolerate a 25–40% price premium before they are turned off.

The chemistry behind biobased surfactants has been known for years. The shift toward them is happening now, Roelants says, because consumers are more conscious of what they’re using to clean their faces and shampoo their hair. In ever-increasing numbers, they want biobased, sustainable products.

Buyers like Henkel are taking an all-of-the-above approach to meeting that demand, even as they look down the road for better approaches. “Folks are looking for sustainability,” Burns says, “and want to try and access it from any and all areas they can.”