Assessing the sustainability and performance of green surfactants

As sustainability targets have become integral to corporate strategies and consumers take a greater interest in the impact of formulations on themselves and the environment, we're often asked about the market for green surfactants. The answer is usually "it depends," based on your understanding of the term "green." The concept of green chemistry encapsulates various elements of natural, bio-based, renewable, bio-degradable, and sustainable concepts, both interms of raw materials and production processes.

Surfactants are an important class of chemicals with applications in household detergents and cleaners, personal care and cosmetics, industrial and institutional cleaning, and an array of industrial processes. The 2019 global market for surfactants, worth an estimated $39 billion, is expected to grow at 2.6% per annum over the next five years to reach $46 billion by 2024. The industry produces over 17 million metric tons of surfactants annually, some of which comes into personal contact with consumers and much of which is ultimately discharged as effluent. Considering this volume, addressing green issues is an important topic for an industry facing increasing legislation and consumer concern.

A vast array of surfactants is available, produced from natural and petroleum-based feedstocks and combinations of both. In this highly competitive market, price and efficacy remain key drivers. Therefore, renewable feedstocks and process economics must compete with petroleum feedstocks that often serve multiple markets beyond surfactant production. Fatty alcohols and acids derived from natural fats and oils - such as soya, palm and palm kernel, rapeseed, sunflower, tallow, and coconut oils - are a major source of feedstocks for the manufacture of surfactants. They also form the cornerstone of the green contribution to the industry.

How Green is Green Enough?

There is much concern regarding the sourcing of natural oils, especially tropical oils. While producers have joined organizations such as the Roundtable on Sustainable Palm Oil (RSPO), there remains considerable debate on the true cradle-to-gate impact of land use for renewable chemical feedstocks. Interestingly, Clariant launched its GlucoPure Sense surfactant in 2017 that uses European sunflower oil rather than tropical-sourced oils. BASF has also commercialized amphoteric betaine surfactants that use microalgae oils derived from fermentation of sugar instead of coconut oil-derived cocamidopropyl betaines for use in hair care formulations.

In 2019, detergent alcohols using bio-based renewable feedstock accounted for 80% of the 3 million metric tons produced. Synthetic alcohols, produced predominantly from ethylene but also from n-paraffins and coal-based Fischer Tropsch processes, still provide cost-effective alternatives to natural feedstocks, especially in regions where ethylene feedstocks are economical, such as the United States. Companies are still investing in synthetic alcohol capacity. For example, Sasol will start up a 160 kilo tons per annum (kta) total capacity facility for Ziegler, alumina, and Guerbet alcohols by early 2021. Recent expansions of linear alpha olefin capacity in the United States and planned expansions in the United States (ExxonMobil) and Saudi Arabia (INEOS) will seek value from the full range of C4-C20+ olefins produced, including the C12-C18 mid-cuts used for detergent alcohol production.

So, does this mean all renewable-based surfactants are green? Most applications require further processing of biobased feedstocks to include moieties that provide the functional properties of the surfactant, resulting in a range of anionic, cationic, nonionic and amphoteric products. Most of these processes involve the incorporation of petroleum-based feedstocks or moieties that would not necessarily be considered green. To help assess individual green qualities, the European Commission of Standardization has devised classifications for biosurfactants, including >95% wholly biobased; 50-94% majority biobased; 5-49% minority biobased; and <5% nonbiobased.

Consumer Demand Drives Change

Anionic and non-ionic surfactants together account for 88% of total global surfactant consumption. Nonionic surfactants are dominated by alcohol ethoxylates (AE), which are used across the spectrum of household, personal care, institutional, and industrial applications. Sorbitan esters, such as sorbitan monostearate, are produced from fatty acids and sorbitol. They represent an important class of non-ionic surfactants derived from renewable feedstocks that are typically used in food and cosmetic applications for their emulsifying properties. Anionic surfactants are dominated by petroleum-based linear alkyl enzene sulfonates, but they also include major products such as alcohol sulfates (AS) and alcohol ether sulfates (AES). AS and AES are produced by sulfation of the corresponding alcohol or its ethoxylate with sulfur trioxide or chlorosulfonic acid followed by neutralization. A fatty alcohol sulfate consequently may have a renewable carbon index of 100% but may not be considered by consumers to be particularly natural or green. Alcohol ether sulfates are predominantly used in personal care and household dishwashing liquids, where the ethoxylation is milder than the alcohol sulfates that are known to irritate skin. Despite this, consumers are increasingly looking to formulations that are completely sulfate-free.

Cationic surfactants such as fatty amines and quaternary compounds are largely used in fabric softeners, while mild amphoteric surfactants such as cocoamidopropyl betaines are mainly used in personal care products. Together they only contribute 12% of the total surfactant consumption by volume.

AE and AES are produced by reacting alcohols, most commonly in the C12-C16 range, with ethylene oxide (EO). They provide products with a wide range of molar ratios of EO to detergent alcohol. Obtaining a 100% renewable carbon index for AE and AES requires the EO moiety to be derived from bio-ethylene oxide, which in turn is derived from bioethanol that is usually produced from sugar cane, via bioethylene.

Numerous bio EO plants exist, although they represent less than 2% of the total EO global production. The largest plants have traditionally focused primarily on the manufacture of bio ethylene glycol. In 2017, Croda International commissioned the first bioethylene oxide unit in North America at Atlas Point and began offering its so-called "ECO range" of ethoxylated surfactants. However, the company has not operated the bio-EO unit consistently since its commissioning. There are several bioethylene oxide plants in China of similar design and scale (30-75 kta EO) as the Croda unit. These plants were mostly built to eliminate long and expensive supply chains for EO, but they also can tout the benefit of offering bio-based products. It is important to note that bioethylene oxide has higher cash cost of production than petrochemical-based processes, due to smaller unit scale and generally higher-cost raw material, bio-ethanol.

High Demand, Low Availability

Personal care applications represent 14% of the total volume consumption of surfactants but will experience higher than average global growth rates of 3.1% over the next five years. They also can offer greater opportunities for green surfactant solutions. Consumers are increasingly discerning regarding products that contact skin, such as shampoos, shower gels, soaps, cosmetics, hand dishwashing products, and household cleaners. Personal care applications also offer greater opportunities for producers to meet consumer demands for more natural ingredients.

The use of glucose moieties in combination with fatty alcohols offers a range of surfactants that have found commercial success, particularly in the personal care and hand-dishwashing markets. Alkyl polyglucosides (APGs) produced by companies such as BASF, Nouryon, and SEPPIC and alkyl glucamides produced by companies such as Clariant have shown tremendous growth over the last five years. Their natural appeal, low toxicity, and effective surfactant properties boosted growth rates above those seen for traditional surfactants. In November 2019, BASF announced expansion of its production capacity for APG at Jinshan, China. Further expansions are planned to meet growing domestic demand and relieve pressure on its facility in Germany. Total global consumption of APGs is now estimated at around 140kmt (100% active).

Sugar feedstocks also provide the basis for a range of amino acid-based surfactants, such as disodium cocoyl glutamate. These anionic surfactants are used in cosmetic and personal care products where mild, natural, sulfate-free ingredients are increasingly valued by consumers. Ajinomoto, a major producer of amino acid-based surfactants, this year announced expansion of its Amisoft® glutamates capacity at a new plant in Brazil, to be commissioned in 2020.

Green surfactants offer an important, growing contribution to the industry - although the size of the contribution can vary depending on perceptions what is natural, bio-based, and sustainable. Furthermore, while many personal care and consumer goods companies have expressed interest in 100% bio-based surfactants, the market has not so far tested consumers' willingness to pay premium prices for otherwise commodity products. This is due to lack of widespread availability of green commodity surfactants to date as much as any other consideration. It is clear that global demand for both petroleum- and bio-based surfactants will continue to grow with increasing hybridization of formulations to meet consumer, legislative, and sustainability demands - all while challenging manufacturers to balance cost-effective formulations with the ability to perform effectively.

Adam Bland | Executive Director - Solvents & Surfactants, IHS Markit