Organic materials, in other words biomass, are major players in the energy system, in many different ways and with increasingly advanced and sustainable technologies. What is biomass, as an energy source? In the energy field, biomass can be defined as all substances that are derived from living organisms and which can be used as a source of energy. This is a comprehensive definition that requires, however, fundamental clarification. Fossil fuels (coal, oil and natural gas) are also derived from living things but, as the term clearly suggests, these are organisms that lived in the very remote past and which have fossilized over time. Biomass, on the other hand, comes from very recent organisms, such as trees that have been cut down or animal droppings. For the purposes of clarity, then, biomass is defined as non-fossilized organic materials. This distinction implies a fundamental difference in terms of supply for energy purposes: fossil fuels sooner or later run out, because the fossilization time of recent organisms points to a future so far from now that it cannot be considered; biomass, like all forms of life, it is in a constant state of renewal. Trees grow, animals are born and reproduce. This is the difference between non-renewable and renewable sources. Types of biomass Biomass can be divided into three categories, depending on the biological origin: plant biomass: this includes wood and residue from agricultural, forestry and gardening activities, as well as energy crops, i.e., crops intended specifically for energy purposes; animal biomass: this is mainly manure, or dung, but also animal waste; microbial biomass: this consists of organic substances in the soil that are the result of the decomposition caused by fungi and bacteria. Moreover, the same microorganisms are themselves a potential source of energy, which will be increasingly exploited, thanks to technological innovation. An alternative way of categorizing the different types of biomass is their physical state: solid biomass: includes wood, manure, waste and organic residue; liquid biomass: this can be biomass that is in a liquid state (such as animal sewage and civil and industrial wastewater) or (increasingly) biomass that has been liquefied as a result of an artificial process: for example, vegetable oils and liquid biofuels; gaseous biomass: this is essentially biogas, a synthetically produced gas that’s used as a biofuel. For what purposes can biomass be used? In energy production, the key difference is between traditional and modern use: Traditional use consists of simply burning easily available biomass (such as manure and wood) for immediate purposes. So, for example, in the kitchen and for heating through ovens, fireplaces or stoves. Modern use, on the other hand, refers to cultivating biomass specifically, or to process it appropriately, for industrial use in order to maximize efficiency, health and safety, and sustainability. In particular, today raw wood is often replaced by high-quality, inexpensive and efficient wood pellets: they are used for space heating and water heating, both for sanitary uses and for powering air-conditioning systems. Combustion also enables biomass to produce renewable electricity: biogas and liquid and solid biofuels can be employed for this purpose. Biomass can also be used in order to produce other substances: in this case, it isn’t burned but is subjected to chemical processes. The best known application is the production of biofuels: for example, bioethanol, methanol, and biodiesel, which are more sustainable alternatives for fueling vehicles than gasoline, methane, and conventional diesel. Other biomaterials obtained from biomass can have applications in numerous fields: from biofertilizers in agriculture to bioplastics in the chemical industry to biocosmetics. How a power plant works and how energy is obtained A biomass power plant is an electricity-generating facility that uses biomass (which can be solid, liquid, or gaseous) as its energy source. It operates similarly to fossil-fueled thermal power plants: the heat generated by combustion raises the temperature of a fluid (typically water) to the point of evaporation, and the steam produced drives an electric turbine. As in conventional thermal power plants, some of the heat generated is lost to the environment without contributing to the generation of electricity. This waste heat can be recovered and used for space or water heating: this is the technique known as cogeneration (simultaneous generation of electricity and heat), which can contribute significantly to the overall efficiency of the energy system. Biomass conversion technologies and processes The main techniques used for converting biomass into energy or biomaterials include: Direct combustion: this is used for generating electricity and heat. It takes place in special plants (biomass boilers) that may vary in terms of their technical characteristics, depending on the type of biomass used; Gasification: this is a technique for converting raw biomass into biogas (synthesis gas, or syngas), which in turn is used for generating electricity by combustion, or else it is further converted into biofuel for transportation; Pyrolysis: this involves the decomposition of biomass into simpler components (solid, liquid and gaseous), with which electricity is generated more efficiently; Anaerobic digestion: this is a biological process by which certain microorganisms degrade biomass. In this case, the result is also a mixture of biogas that can be used for producing electricity and heat. The benefits and challenges of biomass energy The most immediate advantage of biomass for energy production lies in the fact that it’s a renewable source. Furthermore, when compared to other renewable sources, biomass can be found anywhere, it can be stored, and is capable of generating electricity in the desired amount and at any time of day, regardless of weather conditions. Therefore, the modern use of biomass, when conducted in a responsible and sustainable way, contributes to the energy transition to a cleaner system. It is thus a benefit to the climate and consequently to human health. In contrast, the traditional use of raw biomass for domestic activities can cause harm to people's health, due to the particulate matter emitted from indoor combustion. For this reason, the challenge, especially in developing countries, is to gradually abandon these habits in favor of more efficient and healthy cooking and heating technologies. From the point of view of environmental impact, it’s important that resource consumption is managed responsibly and sustainably: with regard to wood, for example, there is a need to ensure continuous replacement of felled trees, in order to avoid contributing to deforestation. The international scenario According to data from the International Renewable Energy Agency (IRENA), biomass accounts for three-quarters of the world's total use of renewable sources. This figure also refers to its still widespread traditional use for domestic purposes, which is not usually considered in statistics for renewable sources. The use of biomass for electricity generation is steadily increasing globally: the total installed capacity of all power plants worldwide more than doubled between 2011 and 2023, from 72,652 MW to 150,261 MW. The largest element is clearly solid fuels which, with 104,588 MW, account for nearly 70% of the total. In terms of individual countries, China leads the way with a total of 31,255 MW (of which 16,880 MW, or 54%, is solid biomass), followed at a distance by Brazil with 17,596 MW (at 97% solid biomass). Italy has lower figures but a more balanced picture, with 701 MW of solid biomass, 1,429 MW of biogas, 909 MW of liquid biomass, and 396 MW of renewable waste, for a total of 3,435 MW (a 52% increase from 2,262 MW in 2011). Future developments A dual path is envisioned for the future for biomass. On the one hand, traditional use will decline significantly, in line with SDG 7 (Clean and Affordable Energy) in the United Nations’ 17 Sustainable Development Goals. Indeed, it should fall to zero in 2030, according to the International Energy Agency's (IEA) Net Zero Emissions scenario. On the other hand, the modern and sustainable use of biomass will continue to grow: the same scenario predicts an 83% increase by 2030, with respect to 2022. However, this will also depend on policies at the global level. The IEA therefore recommends that decision makers recognize the benefits of biomass fuels for the energy transition and establish appropriate regulatory frameworks to incentivize their production and use as renewable sources. Furthermore, the IEA calls on governments and other administrative bodies to encourage the integration of technologies for energy production from organic waste into the energy system. This solution places biomass squarely not only in the field of sustainability but also in that of the circular economy.
