In 1989, Procter & Gamble was the first of the major detergent producers to introduce compact powders with Ariel Ultra (ENDS Report 175, p 5). Lever soon followed with its Persil Micro range. The compacts offered environmental benefits by using fewer chemicals and less packaging, and a move from phosphate to zeolite builders.
The environmental benefits of compact powders and liquids have been recognised in the draft EC eco-labelling criteria for detergents (ENDS Report 226, pp 26-27 ). These basically rule out conventional detergents but allow concentrates and "green" formulations.
Ariel Ultra and Persil Micro would qualify for the eco-label. But producers are continuing to seek improvements. Lever's efforts appear to have paid off and it is launching its new product, Persil Power, in May. The company claims that it delivers a "dramatic improvement in detergent performance with less environmental impact."
Lever hopes to make a significant impact on customers who are still buying conventional powders. And if buying habits were based on environmental considerations alone, purchasers of concentrated liquids should also switch to the new product.
The new powder uses 17% less chemicals by weight per wash than Micro and takes up 30% less volume - reducing the amount of packaging needed. It is also claimed to have a lower toxicity and higher aerobic degradation potential than Micro, as judged by using the critical dilution volume (CDV) method laid down in the proposed EC eco-labelling criteria. CDV is given the highest weighting in the criteria.
The draft criteria also have parameters for total chemicals and non-anaerobically degradable organic compounds. The new compact powder outperforms the old on these as well, according to Lever.
The improvements were made possible by a novel energy-efficient mixing process. Conventionally, dry ingredients are mixed with water and the slurry is sprayed from the top of a tower and dried with hot air. The new process, the "non-tower route" (NTR), mixes dry ingredients, reducing water consumption by 200 litres per tonne of product and overall manufacturing energy use by 80%. It also reduces emissions to atmosphere.
But the main benefit, says Lever, comes in the ability to use chemicals that would break down in the heated "tower" atmosphere. This allows LAS surfactants - linear alkylbenzenesulphonates - to be replaced by primary alcohol sulphates (PAS).
PAS surfactants biodegrade under aerobic conditions more swiftly than LAS. They also biodegrade under anaerobic conditions, unlike LAS.
However, there is a drawback. The concentration of non-ionic surfactants, in this case alcohol ethoxylates, has been increased from 5% to 10-15%. This will impose a higher oxygen demand on sewage works. In addition, there have been few toxicity studies on alcohol ethoxylates, according to a recent report (ENDS Report 222, p 9 ).
The formulation also contains a new zeolite builder with a crystal structure which eliminates more air from the powder, making the product more weight-effective. However, the zeolite concentration has had to be increased from 25-35% to 30-35%. This has been partly compensated for by leaving out the small amount of polycarboxylates which is needed with conventional zeolite. For areas with hard water, this will increase the amount of sludge produced at sewage works. In soft water areas, the lower dosage rates will compensate for the increased sludge generation.
A third change to the detergent's formulation is the replacement of perborate with percarbonate, bringing additional environmental benefits. On washing, perborate is turned into boric acid, which is moderately toxic to aquatic organisms, while percarbonate is turned into soda, which is not toxic.
The product contains a new ingredient - the "accelerator". This is a bleach catalyst complex of a manganese ion, oxygen and two ligands containing nitrogen. It is degraded to the ligand within 30-60 minutes at a sewage works. However, the ligand is not "readily biodegradable". But Lever claims the compound has a low acute toxicity, is non-irritant, non-sensitising and non-mutagenic.
Lever is heralding the accelerator as "certainly the greatest advance in twenty years" in detergent technology. It gives better stain removal than any of the market leaders, according to tests by the Dutch TNO laboratory.
This improvement in performance has the potential to nullify the argument by phosphate producers that zeolite-based detergents are not as effective as phosphate-based products - the central plank of a recent life-cycle comparison of the two products sponsored by phosphate producer Albright & Wilson (ENDS Report 228, pp 29-31 ).
In addition, Lever says that this improved performance can be delivered at lower wash temperatures or in a quicker wash cycle. The detergent becomes effective at 20°C rather than the 40°C of Persil Micro, giving scope for huge energy savings during use. Whether consumers change their washing habits will be the key to whether these are realised. If they do, says Lever, average wash temperatures will be cut by 5%, giving a 14% reduction in energy used for washing in the UK.
Energy consumption during washing is identified in the EC eco-labelling criteria as a major impact in the detergent life-cycle. However, no criterion was proposed for this because existing detergents are formulated to work across the whole range of wash temperatures and for a large variety of textile types and washing programmes. With the new compact the opportunity is now there.