Bar soap is better than liquid soap based on its lower cost per use, equal effectiveness at cleansing and disinfecting, lower packaging and overall lower environmental impact.
Cost – Bill Chameides, in his blog post referenced below estimates a cost of .4 cents per use with bar soap and 3.5 cents per use with liquid soap. Liquid soap is almost ten times more expensive to use.
Effectiveness – Both products clean and disinfect equally. Although bacteria can remain on the surface of soap and the surface of a liquid soap dispenser, there is no evidence that these bacteria (or viruses) will remain on the skin after you wash your hands. See the Scientific American reference below.
Environmental Impact – Liquid soap creates more solid waste including the often one-time use dispenser and the packaging for the liquid soap. Bar soap can be bought without a wrapper in bulk or with minimal packaging. More energy is required to transport liquid soap because of the bulk and weight. People use more water when they use bar soap than liquid soap. I would suggest this is because we leave the tap on as we lather our hands. This can be reduced by turning the tap off during lathering.
Optimizing use/minimizing waste –
- Opt for soap without packaging or with minimal packaging
- If using liquid soap, look for refills versus single-use dispensers.
- Turn off the tap while lathering. Wet your hands and turn off the tap. Lather and then turn the tap on to rinse off.
- Use the minimal amount of liquid product when washing. A full pump might be more than you need.
- When using bar soap, keep it elevated using a soap dish and platform.
- Consider using a soap sponge or washcloth to contain smaller soap scraps
Conclusion: Bar soap is better than liquid soap economically and ecologically.