the thing with farming in the city - and especially a city with such an industrial history as detroit - is that the soil and air you're growing in is very likely to be contaminated and polluted. if you grow in dirty air and/or dirty soil, all the pollution will get stored in the plant; if you then eat that plant, you'll get sick from the pollution that it sucked out of the air. so, if you want to set up a carrot garden in your front yard, you need to understand that your carrots are probably going to be pulling in automotive emissions from the atmosphere and sucking up centuries of industrial waste from the ground. if your city has ever had acid rain, you want to think twice before planting in your yard.

it's not that the farm out of town doesn't have the same problems, on a lower scale, it's that they understand that it's a problem and do regular testing for it. you probably just don't have the resources or know-how to make sure you're doing this safely, but if you do then power to you. but, please understand what you're doing, and the risks you pose to the people that you're feeding if you don't. if you just start growing randomly downtown, those vegetables could very well end up as concentrated carcinogenic poison, in addition to being carbon sinks.

my suggestion - and i've made this over and over again in public spaces - is that you should leave outdoor growing explicitly for carbon sinks, meaning trees and non-edible plants, and that if you want to do urban farming then you should keep it to a controlled, indoor environment with fresh soil and minimal access to outside air. greenhouses are a bit more of an investment and require a bit more upkeep, but if you're doing this for the quality of the food then you should try not to be stupid or hypocritical about it.