Human and dog digestive systems are very similar, but they also have some significant differences. Everyone knows that dogs can not eat or digest chocolate, but few people understand why that is. Chocolate contains theobromine, a stimulant found in the cocoa. Theobromine is harmful to dogs.
Don't simply leave doggie feces on the street. If it is close to the sewage system, during a storm it will wash into a sewer, and into the main waterways. This will cause a spread of bacteria and disease, making the water unfit for consumption. When the dog poop decomposes, it will use up oxygen needed by fish and other aquatic life.
Do not try to put the dog poop into the compost bin because the bacteria from the feces will contaminate the compost and the environment it is placed into. A good way of disposing the poop is by wrapping it in a plastic bag, closing it tightly and putting the bag in the trash if your city allows that. The plastic bag will contain the waste in the event of a trash spill or landfill leak.
The best way of disposing the poop is to recycle the plastic bag by flushing the poop into the toilet when you get home. That way you recycle the bag for many uses, and the dog poop gets flushed, which will eventually make it to through sanitation filters to kill harmful bacteria. If you can, use plastic doggie bags, which are smaller, and switch to reusable fabric bags for groceries. There are even biodegradable doggie bags.