Fat...
Fat with 9 calories per gram
Most of Gram+ bacteria and for Gram- ones, Segnilliparus spp.
The most energy rich nutrient is fat. There are two other nutrients that produce energy for the body and they are protein and carbohydrates.
Fat has the most calories per an ounce. There are 9 calories per a gram, so an ounce of fat has 255.06 calories.
Lipids store more energy per gram than carbohydrates or proteins.
Carbohydrate's I think.
Topsoil contains all the most recently decomposed bio-matter . It is therefore the most nutrient rich layer, best for growing plants and such.
This element is sodium.
In food, there are three macronutrients that provide energy. They are fat, carbohydrates, and protein. Fat is the nutrient that provides the greatest amount of energy at nine calories per gram. Protein and carbohydrates provide only four calories per gram.
The forgotten nutrient and the most important is water.
Fat. More calories =more heat=more energy.
Based upon how fast you can loose consciousness when deprived, oxygen is the most indispensable nutrient.