This week McDonald’s surprised the sustainable food world by announcing it would start sourcing sustainable beef in the year 2016. The move is a part of ongoing efforts by the Oak Brook-based company to improve the sustainability profile of its products. But what will sustainable mean in this case and what does a move like this mean for the overall food market? WBEZ producer Monica Eng talks about the impact of sustainability in the fast food world. (Photo: Flickr/FabPins)