This is an interesting idea. I know I would be interested in buying foods that would get wasted otherwise and most people might if they are a little cheaper. 

To throw out an idea to answer Jacob's question, maybe design the grocery store as a circle. For simplicity, let's say the circle is a hexagon with 6 shelves where people can buy food. 

On day 1, you stock shelf 1 and put a label on it that says the food expires in 6 days. 
On day 2, you stock shelf 2 and put a label on it that says the food expires in 6 days. You change the label on shelf 1 to say the food on it expires in 5 days. 
On day 3, you stock shelf 3 and put a label on it that says the food expires in 6 days. You change the labels on shelves 1 and 2 to say the food on them expires in 4 and 5 days respectively. 
Keep doing this until all shelves are stocked. 
On day 7, your food from day 1 is expired and replaced with new food. The new label on this shelf says the food expires in 6 days. The other shelves are also updated. 

With this model, people always walk sequentially around the circle, but start in a different place depending on the day they come to the store. 

The model I explained here is an over simplification to help explain the concept. In real life, there would be some challenges like
1) Food doesn't often expire in an exact number of days.
2) Even the same type of food put on the shelf on the same day might expire in different amounts of time

Thank you both! :) 

I think the key is to communicate the information in pictures and charts rather than words. The old saying, "a picture is worth a thousand words" is applicable here. 

I think the challenge with communicating the information is to personalize the impact of wasting food. What do you think of using pictures of local water sources, natural landscapes, and farms in some with/without food waste scenarios to make it "real"?

I love this idea! I was wondering if you've considered bringing the Waste Pickers into a collective/coop for additional peer-to-peer support, development of shared/improved social identity, and collective bargaining capabilities? 

http://www.psmag.com/nature-and-technology/rise-of-the-trash-picker-collective?utm_source=Pacific%20Standard%20Newsletter&utm_campaign=1025954bf8-daily-rss-newsletter&utm_medium=email&utm_term=0_a4fd1bcb7e-1025954bf8-76402701