How Enzymes Can Reduce the Environmental Impact Of Liquid Detergents

Environmental regulations and consumer concerns are putting pressure on the entire detergent value chain to offer more environmentally friendly detergents to the market. The environmental impact of doing laundry in the U.S. is primarily affected by the raw materials used to manufacture detergents and, more importantly, the temperature used in washing machines.
The development of new enzyme solutions by Novozymes allows detergent manufacturers to reduce the environmental impact of their detergents by replacing traditional chemicals such as surfactants with a multienzyme solution. This can be done without compromising performance or cost, while at the same time allowing for good cleaning performance at low wash temperatures.

Enzymes are natural substances that are efficient at low concentrations, readily degradable in the environment, deliver low toxicity levels, and most importantly, perform well at low wash temperatures. Thus, detergent manufacturers can reformulate their detergents with enzymes to make them more sustainable and attractive to their customers.

Novozyme researchers insist enzymes boost performance and lower environmental impact of liquid detergents.

It has already been illustrated that there are significant environmental benefits from replacing surfactants with enzymes in a powder detergent in the European market (Nielsen et al., 2007) and from reformulation of detergents for the French market (Dewaele, 2006).

This article highlights the environmental benefits of cost-neutrally replacing surfactants with enzymes in a standard mid-tier U.S. liquid laundry detergent, assessed by doing wash experiments and life cycle assessments (LCA) through ISO 14040-series where all significant processes from “cradle to grave” are included.

Test Method
This study uses a mid-tier U.S. liquid detergent formulated by Novozymes. The detergent was compared to two U.S. mid-tier commercial detergents through wash trials and was found to be similar in performance. Since liquid detergents do not contain a significant amount of builders, it was assumed that reducing the dosage of the detergent is equivalent to reducing the surfactant content. In this study, three sets of detergents were compared. The cost of all three detergents is the same.

1. Baseline detergent (100% surfactant): The standard or baseline detergent was a mid-tier detergent containing only a protease.

2. Medium compacted detergent (90% surfactant + 1% multi-enzyme solution): The detergent where 10% of the detergent content was replaced with 1% enzyme content (protease, amylase and mannanase).

3. Highly compacted detergent (70% surfactant + 2.55% multi-enzyme solution): The detergent where 30% of the detergent content was replaced with 2.55% enzyme content (protease, amylase, mannanase, cellulase and lipase).

The wash performance was tested in a Whirlpool top loader washing machine (WTW5300VW) at a heavy wash program (15 minutes) and a medium load (63 L) – and the wash experiments were repeated four times.

The stain set used is a broad range of consumer-relevant enzyme- and surfactant-sensitive stains regularly applied for testing in North America. The applied conditions (ballast: 2.7kg total fabric load; wash temperature: 59°F and 86°F) represent current standard U.S. wash conditions (in U.S. washing machines temperature settings of cold equal 30°C, 65–85°F; warm equals 40°C, 105°F; while hot equals 50–95°C, 120–200°F).

After wash, all swatches were air dried overnight and remissions of the dry swatches were measured at 460nm using a ColorEye reflectometer.

Fig. 1: The new detergents with multienzyme solutions and reduced surfactant content show better wash performance The wash performance was measured across 22 enzyme- and detergent-sensitive consumer-relevant stains. It is clear from the above graph that even when the temperature is reduced from 86°F to 59°F, there is improvement in wash performance. Wash conditions: U.S. full wash, Whirlpool top loader, 2.7kg total fabric load.

Environmental Assessment
The study is based on LCA principles, where all significant processes in the product chain from raw material extraction through production and use to final disposal are included. The LCA is performed according to the method described by JRC (2010) and environmental modeling is facilitated in the SimaPro 7.1.8 LCA software.

The study compares the impacts that are generated when the new, enzyme-rich detergents are introduced with the impacts that are avoided when the conventional detergents are replaced.

The considered environmental impact categories include:
• Global warming (g CO2 equivalents),
• Acidification (mg SO2 equivalents) and
• Nutrient enrichment (mg PO42- equivalents).

The wash trial results clearly show that when surfactants are replaced by enzymes the wash temperature can be reduced from 86°F to 59°F while at the same time improving performance (Fig. 1).

There are some minimal losses on specific stains (Fig. 2, next page)—but on average the end consumer will experience the enzyme reformulated detergents to offer improved or similar wash performance even as the wash temperature is reduced.

Environmental Impact
The positive environmental effects of replacing surfactants with enzymes and of reducing wash temperature from 86°F to 59°F are shown in Fig. 3 (p. 000) for a broad range of impact categories for the detergent with 70% surfactant and a multienzyme solution. The impact is nearly the same for the detergent with 90% surfactant with a multienzyme solution.

The results show that the environmental impact caused by enzyme production is generally quite small compared to the environmental impact savings obtained by the wash temperature reduction and the reduced use of surfactants. The overall reduced environmental impact reflects the use of a small amount of enzyme having a relatively small impact on the environment as opposed to a much larger amount of surfactants and a relatively large amount of electricity.

For global warming, the saved environmental impacts are primarily caused by reduced production of surfactants and propylene glycol and the reduction of the wash temperature.

Agricultural land savings are primarily caused by surfactant ingredients such as fatty alcohol that is produced from vegetable oil because agricultural land is used for palm oil plantations. Freshwater use show similar results, because of the irrigation water used in the palm oil plantations.

Seen in a life cycle perspective, the new, enzyme-reformulated detergents result in environmental benefits on all investigated impact categories (see Fig. 3).

For global warming, a decreased wash temperature will result in savings of 300g CO2 eq. per wash, and benefits from the change in composition of the detergent are 6.0g CO2 eq. per wash for the detergent reformulated with 1% weight multienzyme solution, and 17g CO2 eq. per wash for the detergent reformulated with 2.55% weight multienzyme solution.

Toxicity
Water bodies around the world are facing manmade pressures that are harming the aquatic environment. Toxicity, acidification, and loss of habitat due to sinking water levels are contributing significantly to diminishing the health of aquatic flora and fauna. Globally, nearly 22% of all evaluated aquatic vertebrates are on the endangered list—this includes fish and amphibians.

Fig. 2: Enzyme reformulated detergents show better performance on most relevant stains The detergent with 90% surfactant + 1 wt% multienzyme solution and the detergent with 70% surfactant and 2.55% weight multienzyme solution show improved performance at 86°F on most relevant stains. There are some losses on specific stains, however, these losses are negligible and the end user will see a marked improvement in wash performance with the new enzyme reformulated detergents. Wash conditions: U.S. full wash, Whirlpool top loader, 2.7kg total fabric load.

Detergents entering these water bodies through the wash water contribute in part to increasing the toxicity of the water bodies. In the U.S., most of the wash water goes through wastewater treatment facilities (UNSD, 2010). However, European Chemical Agency estimates that in Europe nearly 20% of this water, due to overflow, goes directly into environment without processing (ECA, 2008), and similar conditions may very well apply in U.S. as well.

By replacing a percentage of surfactant with readily biodegradable and significantly less toxic enzymes, the toxicity contribution of detergents to the planet’s water bodies can be reduced dramatically (see Fig. 3, next page).

In this study, eco-toxicity assessments of both surfactants and enzymes after use were measured based on a screening method, calculation of critical dilution volume (CDVtox). CDV offers a way to understand the potential toxicity of cleaning products and toxic chemicals on the water system. CDV measures how much water is needed to neutralize a substance. It takes 240 times less water to neutralize enzymes than surfactants (Fig. 3). If all washes in the U.S. were done with detergents that were reformulated to have only 70% surfactant and 2.55% weight multienzyme solution—the equivalent to more than 3,600 million Olympic swimming pools worth of water couldbe safeguarded against toxicity from detergents in one year.

Conclusions
The cost-neutral replacement of surfactant with enzymes in a standard laundry detergent allow for reduction of laundry wash temperatures and toxicity impact on water bodies without compromising the total wash performance. Enzyme use is small compared with surfactant savings and the environmental impact caused by the extra enzyme use is insignificant compared with the savings obtained by reducing the surfactant content and particularly reducing consumption of energy used to heat wash water.

Fig. 3: Enzyme-based formulas have little environmental impact This graph clearly shows the environmental impact from added inputs (enzymes), saved inputs (chemical detergent ingredients) and saved heat from reduced wash temperature when a consumer changes from the standard detergent to use a detergent with 70% surfactants plus a multienzyme solution and reduces wash temperature from 86°F to 59°F. All data is per one wash of 2.7kg laundry.

Data quality assessments and sensitivity analyses show that exact results are uncertain and depend on the magnitude of the temperature reduction, the applied water heating systems and a range of other factors, but they also show that the overall conclusions of the study are robust. The enzyme-rich detergent examined in this study costs the same as the conventional detergent and substantial environmental impact improvements can be realized while saving on the consumers' electricity bill.

Surfactant savings and temperature reducing results in a savings of 317g CO2 eq. per wash for a detergent where the surfactant content is reduced by 30%. If all consumers in North America washed their hot/warm washes at the low temperature of 59°F, the savings in fossil fuel would equal nearly 21 million barrels of oil or 19 fully loaded oil tankers. The savings to the environment will be nearly 7.4 million tons of CO2, which equal the annual emissions from two million cars.

These are significant environmental savings and Novozymes is pleased to join forces with colleagues in the detergent industry across the value chain to realize this potential in the coming years.

References
Dewaele J. Pant R. Schowanek D. Salducci N (2006): Comparative Life Cycle Assessment (LCA) of Ariel “Actif à froid” (2006), a laundry detergent that allows washing at colder wash temperatures with previous Ariel laundry detergents (1998. 2001). Available at http://www. scienceinthebox.com/ en_UK/pdf/ Ariel%20Actif% 20a% 20Froid%20LCA%20report%20Nov%202006.pdf

European Chemical Agency (2008):Guidance on information requirements and chemical safety assessment Chapter R.16: Environmental Exposure Estimation.Available athttp://guidance. echa.europa.eu/docs/guidance _document/information_requirements _en.htm

Joint Research Center (2010): International Reference Life Cycle Data System. General Guide for Life Cycle Assessment – Detailed Guidance. European Union. Available at http://lct.jrc.ec.europa.eu/publications

Nielsen PH. Oxenbøll KM. Wenzel H (2007): Cradle to gate environmental assessment of enzyme products produced in Denmark by Novozymes A/S. Int J LCA OnlineFirst. http://dx.doi.org/10.1065/lca2006.08.265.1

United Nations’ Statistical Database (2010). Map over percentage of population connected to urban waste water collecting system. http://unstats.un.org/unsd/environment/wastewater.htm


About the Authors
Anne Merete Nielsen is senior life cycle economist, Dr. Teresa J. Neal is regional marketing manager, Sandra Friis-Jensen is global launch manager and Amulya Malladi is global communication manager, all with Novozymes. For more information about enzyme-rich detergents, call or email: Teresa J. Neal at +1 919-494-3064 or tjna@novozymes.com