I am wanting an alternative to soap for handwashing in our school garden. Currently we station a bucket, scrubbing brush, and bar of soap near a tap. Students need to wash their hands before heading back to class. This uses a fair amount of water (kids aren't very efficient, and sometimes 5-10 kids might need to wash hands). I would love to use this water for something, or alternatively find some suggestions for garden friendly detergents (they need something as the scrubbing brush does not get their hands clean enough easily enough).