Green and Clean - Given the prominence of concerns relating to the greenhouse effect and increasing resource scarcity, the importance of renewable raw materials is constantly growing. The following article presents some of the most interesting trends for the laundry and home care product (LHCP) industry and shows where bio-based chemicals played an important role in the overall sustainability strategy .

Sources for Renewable Raw Materials

The primary sources of renewable raw materials are plants and micro-organisms. In order to convert them to high performance bio-based ingredients, plant-based raw materials generally have to undergo a series of chemical purification and processing stages. These operations modify the initial molecule, frequently through the use of petrochemical components. The second major source of renewable raw materials is that produced by micro-organisms (white biotechnology). Micro-organisms capable of producing the desired target molecule are obtained through natural selection or genetic engineering processes. Although further chemical modification is possible, it is not usually necessary.

Bio-based Chemicals for Laundry and Home Care Products

Globally, laundry and home care products are manufactured in extremely high volumes. In Germany, the quantities produced in 2008 amounted to some 630,000 t (metric tons). Because of these high tonnages and the wide range of materials employed, LHCPs represent a particularly attractive market for bio-based chemicals. The chemical ingredients employed in LHCPs fall into two similarly sized groups if split at an arbitrary dividing line of 10,000 t. The high volume group is essentially dominated by inorganic base materials such as zeolite, soda and sodium sulfate. In this group surfactants, alcohols, citrates, and polycarboxylates are the most important materials in term of quantities that are suited for substitution by bio-based chemicals.

Surfactants

Surfactants play the most prominent role in LHCP, not only because of their function but also in view of the input volume they represent, which is about 200,000 t. Soaps based on fatty acids were among the first surface-active materials to be used, hence, renewable raw materials always played a key role. Surfactants are characterized by a hydrophilic and a hydrophobic molecular component.

Structures of this kind are relatively rare in nature. Typically, the hydrophobic part is provided by palm kernel or coconut oil, the alkyl chains of which are of an optimum length in terms of their suitability for the application technology. These vegetable oils are subjected to chemical modification in order to produce surfactants of sufficient performance. Various surfactant classes are produced by the addition of a hydrophilic molecular component that improves solubility in water. The inclusion, for example, of a sulfate group produces a fatty alcohol sulfate which, due to its negative charge, may also be referred to as an anionic surfactant. Another possibility is to introduce hydrophilic ethoxylate units leading to so called non-ionic surfactants.

Typically, mineral oil is used in the production of ethoxylates although ethoxylate units based on bio-ethanol produced from sugar cane recently entered the market. Through the addition of a sulfate group, fatty alcohol ethoxylates are converted into fatty alcohol ether sulfates, an important group of surfactants used primarily in household cleaners and dishwashing products. The use of sugar molecules as the building blocks for the hydrophilic molecular component produces the alkyl polyglucoside [APG] class of surfactants based entirely on renewable raw materials.

APGs are mainly used in specialty applications and are therefore of subordinate importance in volume terms. Renewable raw materials are used not only for anionic and non-ionic surfactants but also in the manufacture of the cationic class. In fabric softeners, readily and fully biodegradable so-called esterquats have now completely superseded poorly bio-degradable petro-based surfactants. In addition, bio-surfactants manufactured with micro-organisms using white biotechnology, are also playing an increasingly important role in LHCPs. However, it still remains to be seen if they can compete with high volume surfactants with respect to performance and price.

Alcohols

In all, 27,000 t of alcohols were used in LHCPs in Germany in 2008. The most important alcohols are short-chain, aliphatic alcohols (e.g. ethanol), which are used as solubilizers in household cleaners and dishwashing detergents. Ethanol can be derived from petro-chemical sources but there is an increasing supply of bio-ethanol based on sugar cane, corn, or agricultural waste material (e.g. straw) mainly for the bio-fuel market. However, polyols such as ethylene glycol and glycerin are also employed. Given the diversity of the alcohols involved, it is difficult to generalize on their origin and raw material base. Glycerin - which occurs as a by-product of the saponification of fats and oils - constitutes a renewable raw material in the classic sense. Due to the increase in bio-diesel production there is currently an abundant supply of glyercin.

Citric Acid and Its Salts

Citric acid and its salts (citrates) are predominantly used as pH regulators and builders in liquid laundry detergents and household cleaners. Citrates are primarily manufactured through the fermentation of molasses by using different Aspergillus species. The total amount used in Germany in 2008 was 16,200 t, but this is clearly exceeded by the volumes being employed in the food industry. .

Polycarboxylates

In Germany, a total of 14,900 t of polycarboxylates was consumed in 2008 predominantly as co-builders in detergents where they played a key role in the development of phosphate-free detergents. Polycarboxylates are polymers based on acrylic acid or maleic acid, with both homopolymers and copolymers being required by the LHCP industry. Currently there are no known bio-based chemicals with a similar performance spectrum.

Specialties

Aside from these high-volume materials, there is a wide range of organic ingredients used in LHCPs, of which the quantities consumed in 2008 remained below the 10,000 t delineation limit. Due to their tailored properties and special functionalities, their replacement by bio-based chemicals is only possible to a limited degree. Within this group enzymes, carboxymethyl cellulose, and perfume oils are the categories where renewable raw materials play a prominent role.

Enzymes

Enzymes play a particularly important functional role in LHCPs because they enable the selective, gentle removal of critical, natural stains (e.g. blood, protein and starch). The total volume of enzymes used in 2008 amounted to 4,200 t, the majority being proteases and amylases. Enzymes are exclusively manufactured through fermentation by using various sources of renewable raw materials as a feedstock.

Carboxymethyl Cellulose

Carboxymethyl cellulose [CMC] is used in laundry detergents as a soil carrier to counter the problem of graying in fabrics. The quantities used in Germany in 2008 equated to around 3,600 t. CMC is a chemically modified cellulose in which, depending on the application, approx. 0.5 - 1.5 % of all monomers are converted with a carboxymethyl group.

Perfume Oils

In 2008, the German LHCP-manufacturing industry consumed around 8,400 t of perfume oils. Perfume oils are complex blends of natural, semi-synthetic and synthetic ingredients. The proportion of renewable raw materials (typically essential oils) employed in perfume oils are currently estimated at 10% of the total tonnage in this class.