I just wrote a long reply that got lost. Thanks SOMD
To summarize, I called the Charles County Dept. of Health and talked to a guy named Jerard who is in charge of the Welcome, MD area where I am looking at land. He said they categorize things in one of three ways:
Conventional: standard septic systems, wells, etc.
Alternative: Compost toilets fall in here. He said they usually look at and approve things in this category if they fail optimum perc (<30 minutes to drain). If it's 31-60 minutes then they look at this category. Maryland does allow for compost toilets (
Information for Homeowners)
Innovative: Constructed wetlands for greywater recycling. This would require engineers and multiple signoffs. Probably would take a lot of money, a lot of connections, or maybe some academic support (say from UM).
In all Jerard was helpful and friendly. I think I have a fair chance of getting a compost toilet approved with him. I think I would probably need to get some help for the constructed wetlands however. He did say someone in the county got a grant to install such a system, but it wasn't maintained and so weeds took over and it stopped functioning before too long (such a system would need to be looked at a type of garden that needs continued care).
Finally, I found a company near Fredrick that has installed many such systems across Maryland and surrounding states:
Welcome To nutricyclesystems.com. They even installed one at the White Plains Post Office. I'm going to contact them for advice.