biomass (energy) refers to a type of energy useful in formal energy terms: plants transform the Sun's radiant energy into chemical energy through photosynthesis, and part of that chemical energy is stored in the form of organic matter; The chemical energy of biomass can be recovered by burning it directly or transforming it into fuel.

A very common mistake is to confuse "organic matter" with "living matter", but it is enough to consider a tree, in which most of the mass is dead, to undo the error; In fact, it is precisely the "dead" biomass that is most useful in the tree in terms of energy. This is an important debate in ecology, as this assessment by Margalef (1980:12) shows.

Another very common error is to use "biomass" as a synonym for the useful energy that can be extracted from it, which generates a lot of confusion because the relationship between useful energy and biomass is very variable and depends on countless factors. To begin with, useful energy can be extracted by direct combustion of biomass (wood, animal excrement, etc.), but also from the burning of fuels obtained from it through physical or chemical transformations (methane gas from organic waste, for example), processes in which some of the original useful energy is "always" lost. Furthermore, biomass can be directly useful as organic matter in the form of fertilizer and soil treatment (for example, the use of manure or mulch). And of course we cannot forget its most common use: serving as food for very diverse organisms, humanity included (see "food chain").

Biomass from wood, agricultural residues and manure continues to be a main source of energy and useful materials in low-income countries.

industrialized.

In energy terms, it can be used directly, as is the case with firewood, or indirectly in the form of biofuels (note that ethanol can be obtained from wine by distillation): "biomass" should be reserved to refer to the raw material used in the manufacture of biofuels.

Biomass could provide substitute energy for fossil fuels, thanks to liquid agrofuels (such as biodiesel or bioethanol#Bioethanol "Ethanol (fuel)"), gaseous (methane gas) or solid (firewood), but it all depends on not using more biomass "Biomass (ecology)") than the net production of the exploited ecosystem, on not incurring other fuel consumption in the transformation processes, and that the energy utility is the most appropriate compared to other possible uses (such as fertilizer and food).[1]​.

Currently (2022), biomass provides complementary fuels to fossils, helping the growth of global consumption (and its corresponding environmental impacts), especially in the transportation sector.[1]​ This fact contributes to the already extensive human appropriation of the total product of photosynthesis on the planet, which currently exceeds more than half of the total (Naredo and Valero, 1999), an appropriation in which we compete with the rest of the animal and plant species.