Soap has been around for thousands of years. Originally a combination of plants, soap is a unique substance that dissolves in water and removes dirt and grease. A century ago, the soap consumed in homes was solid: the same bars of soap for washing clothes, dishes, body and hair. Toilet soap also appeared in the form of a bar, and only in the 60s and 70s of the last century did shampoos and other types of liquid soaps become popular.
Today, most of the soaps and detergents we consume are liquid. Dishwashing liquid, shower gel and shampoo for body and hair, liquid hand soap in the sink, liquid detergent for our washing machine and even for the dishwasher. However, alternatives still exist, such as bar soap and powder detergents. Which option is more effective for cleaning and which is more sustainable for the environment?
Hygiene and effectiveness of liquid and powder soaps and detergents
From a hygienic point of view, both types of products, whether solid or liquid, are designed to fulfill their main function: cleaning. The effectiveness of a soap or detergent does not depend so much on its condition as on its chemical composition. However, solid soaps and detergents have a significant advantage in terms of hygiene because they are less subject to bacterial contamination.
Since the 1980s, it has been known that a solid bar of soap does not transfer bacteria when washing hands, even if it is dirty. This dispels the common belief that they can be a breeding ground for microorganisms. On the other hand, liquid soap dispensers, especially those that are filled manually, can be more easily contaminated with mold and bacteria, especially if they are not cleaned often. This is why liquid soaps and detergents of all types must include powerful preservatives in their formula, some of which, like phthalates and parabens, can cause adverse reactions in some people.
In terms of effectiveness against dirt, there are some minor differences. In powder detergents, the main surfactant is alkylbenzene sulfonate (LAS), a cheap ingredient that is effective against dirt, but not as effective against grease or oil stains. On the contrary, most liquids also contain alcohol ethoxylates, which are effective against more stubborn grease stains. For this reason, if our clothes have grease stains, we will get better results with a liquid detergent.
As for using a bar soap versus a shower gel or bath gel, there are also pros and cons. Bar soaps generally have an alkaline pH that is harsher on the skin, so they are not recommended for those with dry skin or conditions such as atopic dermatitis. On the other hand, gels and liquid soaps often contain moisturizing ingredients that may be recommended for this type of skin. On the other hand, bar soaps are paraben-free and it is easy to find hypoallergenic options.
Durability of solid detergents and soaps compared to liquids
In terms of sustainability, solid products lead the way. The main reason is their lower environmental impact compared to their liquid counterparts. Solid soaps and detergents are usually presented in simpler and more environmentally friendly packaging, such as paper or cardboard, biodegradable or easier to recycle than the plastic containers in which liquids are sold. Likewise, the solid format almost completely eliminates the need for water in its composition, unlike liquid products that contain a high percentage of water. This means that they have a lower weight and volume, and therefore the transport of solid products consumes less fuel and emits less CO2, thus reducing the carbon footprint associated with their distribution.
A report from the United States Environmental Protection Agency (EPA) on reducing packaging waste highlights that minimizing the impact of plastic containers for soaps and detergents and opting for more sustainable solutions can have a significant impact on reducing waste generated by consumer products.
Both soap formats have their advantages and the choice between one or the other may depend on personal preferences, specific conditions of use and environmental considerations. However, as consumers, from a hygiene and sustainability perspective, solid products offer the most significant advantages.
