Is exergy destruction minimization the same thing as energy efficiency maximization?

: This paper discusses whether the exergy destruction minimization or energy efficiency maximization comes first in resolving the climate emergency problem and provides sustainable solution options regarding the 2 nd Law of thermodynamics. It has been shown that low-temperature district energy systems with renewable energy sources and waste heat are effective in minimizing exergy destructions, while energy efficiency has a secondary impact. The research has been based on the Rational Exergy Management Model. The corresponding rational exergy management efficiency was directly related to nearly-avoidable CO 2 emissions responsibility with a global magnitude of around 80% of direct emissions in the built environment. One conclusion deduced from such an unrecognized magnitude so far is that nearly-avoidable CO 2 emissions may not be ignored anymore to develop new strategies for sustainable decarbonization, while the 1 st Law measures have limited remaining capabilities. New equations were developed to show the impact of exergy destructions on total CO 2 emissions. Sample results show that a 30 percent-point decrease of exergy destructions comparing to the supplied exergy in thermo-mechanical systems has the potential of reducing total CO 2 emissions by 35%. The paper argues that current exergy destruction is around 0.8 of the supply exergy, as an industry average, which gives ample room for improvement using the 2 nd Law, while the 1 st Law efficiency is already higher, and there is less room available for improvements concerning CO 2 emissions. The paper shows that the 1 st Law efficiency may be increased by about 0.15 points, which gives a window of opportunity about a 25 percent-point decrease in emissions. The second main conclusion is that nowadays, new decarbonization strategies are needed based on the 2 nd Law, which will positively impact when coupled with the current 1 st Law measures towards meeting the Paris agreement. These results show that even in a simple solar flat plate collector, the number and type of useful applications arranged in tandem, like further use of the remaining heat in preheating the municipal water supply instead of wasting the heat, is important about exergy-based high rationality. In a holistic view,  CO 2 may be related to exergy rationality, ψ R . From Equations 6-a and 6-b, and ψ R ~ε dem /ε des , for all cases, Equation 8 is derived.