An average plane has 50t of mass and a landing speed of approx. 250 (lets be conservative) 200 km/h. Thus its kinetic energy at landing is about 75 MJ or 21 kWh. The plane catches the wire attached to a pneumatic or hydraulic system, which will decelerate the plane and harvest its kinetic energy. The built up pressure in the system can be released via some kind of turbine to convert the pressure (potential energy) to electricity. Lets say the system has 50% efficiency. Leading to 10kWh harvested energy, per landing.
The airport in Hamburg, Germany is just average. Not large and not small. They had 150 000 flight movements in 2017. Lets say half of them are big planes and 1/2 were landings. That is 37,5k landings per year. Lets say 2/3 could use the arresting gear system: This would provide a cumulative 250 MWh of harvested electricity per year. This is equivalent to the electric energy consumption of 100 two person households in Germany. In Germany 1kWh electricity costs about 30 euro cents (including tax etc). An airport could save 75000 euro per year when harvesting this energy and use it, instead of buying it from the net. I can't imagine, that such a harvesting system would not pay down after a couple of years.
Why there are no systems like this in the aviation industry?
You need to refit thousands of planes with a wire catching System
System has to be safe in case of a go-around