This BBC article features a device that helps recover heat from kitchen fumes in restaurant kitchens. That heat from the hot air vented from the kitchen can be recovered, for example, to heat air coming from the outside into the restaurant. This reduces the overall heating needed to keep the restaurant warm. 

Heat exchange systems that transfer warmth from one part of a building to another are already common in many industries and operate at several of our Intertek facilities. However, there is still potential to extend their use, especially in laboratories where air is renewed frequently (to reduce worker's exposure to hazardous substances), saving energy and reducing our carbon footprint. 

Why there is serious money in kitchen fumes - BBC News