You would need to contact the manager of the community garden, they all have their own rules. Due to concerns about the spread of pathogens, there is a state regulation that addresses composting toilets. Oregon Administrative Rule<personal data hidden> states that "Humus from composting toilets may be used around ornamental shrubs, flowers, trees, or fruit trees and shall be buried under at least twelve inches of soil cover. Deposit of humus from any compost toilet around any edible vegetable or vegetation shall be prohibited."