"Reverse graffiti, also known as clean tagging, dust tagging, grime writing or clean advertising, is a method of creating temporary images on walls or other surfaces by removing dirt from a surface. It is often done by removing dirt/dust with the fingertip(s) from windows or other dirty surfaces, such as writing 'wash me' on a dirty vehicle. It is also used commercially as a form of guerilla advertising to reach consumers in an unconventional new way. The duration of adverts lasting in the street ranges from 8 - 16 weeks depending on the footfall intensity and weather conditions of any given advertising location.
Sustainable, eco-friendly advertising is highly visible due to its overt placement, predominantly in urban areas. Companies such as Microsoft, the BBC and Smirnoff have advertised their products in this way. In this context, marketers call it, "clean advertising" and "clean graffiti"."

I know ink isn't really included in this "biodegradable way of working" but maybe I could use water soluable ink and get it onto walls with a stencil?