Green chemicals are rapidly making headway in the detergents sector, with established companies and new startups alike innovating with plant and microbe alternatives
Detergents are a section of the chemical industry where bio-substitutes for petrochemicals are being adopted at a rapid rate. Europe is the largest market for renewable detergents and 50 percent of the estimated 3 million tons of surfactants made there are bio-based. The switch to bio is largely thanks to the EU’s Regulation No 648/2004 restricting fossil products in industry.
The move towards renewable, less toxic, and biodegradable detergents is welcome for a number of reasons. Found in almost every kitchen and bathroom across the developed world, it is easy to forget just how hazardous these ubiquitous toxins are. Even at highly diluted concentrations, synthetic detergents have been shown to disrupt the shape and function of human lung cells.
Detergents are also a major driver of environmental pollution. The most dramatic evidence of their eco-toxicity can be seen in places like India’s Ramuna river, where detergent run-off from homes and factories lather into waves of noxious foam. Made from non-biodegradable petrochemicals like ethylene and prolylene – substances that cannot be broken down by naturally occurring microbes – they linger in the water, afflicting fish with gill damage and blindness. The phosphates, sulphates, nitrates, and chlorides they contain encourage toxic algal blooms and bio-accumulate through the food chain.
The rise of synthetic detergents
As with many important chemical sectors today, the detergent industry’s love affair with fossil-based ingredients began in the early 1930s. Between 1931 and 1932, Proctor and Gamble and Germany’s Feinwaschmitte marketed the world’s first synthetic surfactant-based detergents in quick succession. Uptake for Proctor and Gamble’s new product was slow until World War II, when the US Navy needed a detergent compatible with sea water. P&G’s formulation fit the bill, with ingredients capable of bonding to water-borne minerals. Indeed, one major advantages of the new synthetic cleaners was that they worked even in hard water areas.
P&G’s military contract gave them a springboard into the post-war consumer market, which quickly embraced the chemical innovation. Over the 1950s, rising disposable incomes and the entry of women into the workforce boosted the popularity of synthetic cleaners. These mass-produced chemicals became emblems of middle-class comfort alongside the new labour-saving technologies they were used to clean, like automatic clothes washers and microwave ovens. Aggressive marketing campaigns by the detergent companies further raised the profile of these powerful new cleansers and by 1957, synthetics had captured 90 percent of the American detergent market. Petrochemical-based detergents remain among the most commercially successful creations of the chemicals industry ever.
The importance of surfactants
It is ironic that substances we depend upon so heavily for daily health and sanitation are among the most damaging to living bodies and ecosystems. However, it was not always so. Before the 20th century, people cleaned clothes and surfaces with salt blocks of fatty acids, better known as soaps. These simple concoctions were formed through a heat reaction that combined animal or plant fats (coconut, palm, whale oil, or meat industry by-products) with wood ashes or caustic soda as cleansing agents.
Green chemical companies are now returning to biological compounds to replace hydrocarbon feedstock in their detergent formulations. Increasingly, consumers and industry are finding that these alternatives can offer equally effective cleaning performance as some synthetics. This is because almost all soaps and detergents derive their cleaning power from a class of chemicals called surfactants, a substance that can be derived from natural organisms.
Surfactants are one of the most important and widely produced industrial chemicals in the world, with applications beyond detergents in everything from cosmetics to agriculture. Although a lion’s share of global surfactants is still derived from fossil fuels, the natural world is replete with it. So much so, in fact, that they occasionally become visible as floating foam on the surfaces of rivers and lakes – the products of surfactants secreted by living organisms into soil and waterways. Unlike their recalcitrant synthetic cousins, natural surfactant pollution is unperfumed and usually appears after storms when watery agitation whips up low concentrations into visible bubbles.
Surfactants harbour two key properties that make them practical stain removers. First, they lower water surface tension, allowing liquid to flow into and out of small, dirt-ridden spaces. Another is that they form peculiar molecular structures that powerfully draw out dirt and oil. Surfactant molecules consist of long water-repelling ‘tails’ attached to a water-attracting ‘heads’, a chemical dualism that is critical in removing otherwise insoluble stains. When surfactants reduce water surface tension to a critical point, these molecules coalesce into rings called micelles where the water-repellent tails point inwards and the water-attracting heads face outwards. The inner tails capture solids, syphoning them away into the centre of the molecular globule. At the same time, the water-attracting heads pull the now solid-filled structure towards the watery elements inside the detergent solution. The result is a stain-free surface.
Plant-based bio-surfactants
Plants make many different classes of biosurfactants, but saponins are the most highly prized. Sapopins come in different chemical forms and are found in more than 100 families of vascular plants like Liliaceae, Dioscoreaceae, and Agavaceae, as well as in some marine plants. These chemicals produce a soapy lather when agitated in water, are non-toxic and biodegradable. Although some researchers have found they perform better than synthetics on cleaning performance, saponin has not so far been successfully commercialised. A joint research project between Unilever and the University of Edinburgh are currently developing potential manufacturing methods.
Phospholipids are another plant surfactant class, a substance found in the mucus exuded by the roots of certain species. The plants benefit from root phospholipids because they alter the chemical properties of nearby soil particles and reduce the surface tension of soil water droplets. These mechanisms increase the nutrients available to the roots and are also what makes these substances so effective at stain removal. Unlike saponins, phospholipids are already common on the biosurfactants market, particularly in the form of lecithin. 95% of commercial lecithin is made from degummed soy, with other sources being rice, canola, cottonseed, palm, corn, and sunflower oils. Saraya Co Ltd., which produces eco-friendly cosmetics and cleaning agents, is a key supplier.
Many of the large established bio-surfactant companies use cultivated plants as feedstock for their products. However, the latest entrants are experimenting with waste feedstocks to establish a circular supply chain. In 2020, Seattle-based stirrup Sironix Renewables raised a total of $1.8 million to scale its detergent product Eosix®, which uses surfactants drawn from the sugars in agricultural waste. Its formula was discovered at the University of Minnesota while researchers were investigating potential industrial compounds within plant biomass. Sironix says it can be used to replace oil-based chemicals in shampoos, detergents, and cleaning products.
Microbial biosurfacants
Bio-surfactants need not come from plants. They can also be mass-cultivated inside microbes such as Pseudomonas, Bacillus, Rhodococcus, and Candida. Grown within bioreactors, which feed on and metabolise substrates like alkanes, oils, sugars, or bio-waste. Surfactin, a lipopeptide surfactant that can be fermented with the bacterium B. subtilis, is widely regarded as one of the most powerful biosurfactants ever reported in literature. Researchers are currently working out cost-effective ways to scale. In 2021, a publication reported fish waste as a potentially cheap and effective substrate for the organism.
Microbial fermentation will be key to maximising the sustainability of bio-surfactant production. It dramatically cuts down on land use compared to plant-based surfactants, which often depend on environmentally destructive monocultures in cash crops. This especially applies to palm oil, currently a major biomass source for the biosurfactants industry.
Widely commercialising fermented biosurfactants however remains a work in progress. The process is far more sophisticated and less optimised than plant extraction. One of the most costly aspects of making commercially viable fermented biosurfactants is the isolation and purification process, where the target chemical is removed from the microbial broth after the growth period is complete. Cost reduction will also depend on genetically engineering bacteria for increased yield productivity.
Despite these challenges, the fermented biosurfactants industry is displaying marked activity. Manchester-based startup Holiferm uses yeasts naturally found in honey to produce a natural surfactant called sophorolipids. Their product is 100 percent biodegradable and comes in high and low foaming versions for use in cosmetic creams, surface cleaners, shampoos, and conditioners. Holiferm recently entered an exclusive cooperation partnership with major German chemicals company BASF to develop fermentation-derived ingredients for personal care, home, and industrial uses. In 2020, BASF itself launched a new fermented sophorolipid -based surfactant for the Asian market under the brand name BioToLife.
Evonik, one of the world’s largest green chemical producers, launched a fermented plant-based surfactant in 2015. Also in the sophorolipid class, their product was quickly adopted by Ecover, now one of the most visible bio-based cleaning brands in supermarkets. Evonik also produces another bio-surfactant type, rhamnolipids, made through fermenting sugar using a genetically modified pseudomonas putida bacteria. Unilever’s Chilean dish soap brand Quix uses this ingredient. In January 2022, Evonik announced it will build a multi-million euro plant in Slovakia to scale their new rhamnolipid biosurfactant, a plant large enough to dramatically bring down the market prices of its sustainable substitutes.
The science of effective microbial surfactant fermentation is an active area of research, with a particular focus on strain selection for maximising yields. In 2020, the EU research consortium Marisurf ended a 5-year, €4.8 million project investigating bio-based surfactants from marine microbes. The project started with 500 candidate marine microbes, whittled these down to two productive strains. The team worked with industrial partners such as Bio Base Europe Pilot Plant VZW and EcTechSystens to scale production. The chemicals that resulted received positive feedback from end-user companies Marlow Foods, Apivita, and Nanoimmunitech, indicating clear commercial potential. The tech is now awaiting investment for industrial scaling.
Although bio-based detergents are not yet price-competitive with petrochemical synthetics, further climate targets legislation would rapidly change the market calculus. Of the 17.6 million metric tons of surfactant consumed globally, around 34.61 percent goes into household detergents, making this a segment where growing consumer concerns around the health and environmental impacts of everyday chemicals is primed to galvanise significant industry shifts towards bio-substitutes.
