I want to start making homebrew, but dont own a diesel car. How can i get rid of or sell my homebrew? 

Yes but even if you make it and use it yourself, you have to pay Unscle Sam and Brother State fuel taxes.

Yes but that does not answer my question. I know I can sell to farmers, but  are there any publick markets for hombrewers

 Where are you located?

 Maryland

IF your biodiesel gets tested and meets ASTM standards, and IF you pay all the requisite road taxes and IF you can manage to find regular buyers, it could work out for you as a legal commercial venture. That's really cost-prohibitive. More likely, you'd have to go into the legal grey area and sell it "under the table", perhaps through a local co-op or something.