Heat and Thermal Pollution

As noted in Lenntech.com:

In most manufacturing processes a lot of heat originates that must be released into the environment, because it is waste heat. The cheapest way to do this is to withdraw nearby surface water, pass it through the plant, and return the heated water to the body of surface water. The heat that is released in the water has negative effects on all life in the receiving surface water. This is the kind of pollution that is commonly known as heat pollution or thermal pollution.

The warmer water decreases the solubility of oxygen in the water and it also causes water organisms to breathe faster. Many water organisms will then die from oxygen shortages, or they become more susceptible to diseases.

More information on this topic under thermal pollution.

This page from the Rensselaer Polytechnic Institute website notes that

Almost half of all water withdrawn in the United States each year is for cooling electric power plants.

Focus Fusion power plants are currently estimated to run at 50% efficiency, which means that 50% of their output will be in the form of heat.  They thus also require cooling. 

The more efficiently a plant can convert energy to electricity, the less it needs to withdraw water for cooling.  Heat pollution decreases, consumption of water drops and the quality of water in rivers and lakes improves dramatically.  This is an important aspect of energy production.  There is much room for improvement.  Something we need to do to reduce the human footprint on lakes, rivers and oceans. 

What we need for this section is a chart comparing the heat and thermal pollution footprint for different energy production processes.