Oh, I agree. The minimizing of waste heat energy is a major topic in stationary engineering. Physical plants that generate steam, for example, are optimized to minimize waste. The people who own physical plants, power plants, etc, certainly have always had a strong interest is reducing fuel costs.
How about this, then: A bank of Stirling heat engines using the waste heat. Actually, I'm not sure if 80 C is enough to run one of those, either.
We are already bringing the discharge steam down to condensate at about 28" Hg vacuum and at less than 100 degrees F to maximize the efficiency of the steam cycle. Now think. We immediately heat the water back up under pressure to about 450 degrees. Any energy you took out of that water. Any energy that we took out of this feedwater, would have to be added back as reheat.