The term biomass generally refers to a collection of animal or plant organisms present in a certain quantity in a given environment such as aquatic or terrestrial (biodegradable fraction of products, waste, and residues from agriculture, including vegetable and animal substances) used for energy production (electricity or heat), or in various industrial processes as a raw substance for a range of products. The concept of biomass is often developed and treated differently in the literature depending on the context in which it is placed. Biomasses are particularly important in two different fields: ecological and renewable energy, where they represent a source of energy of biotic origin.
Biomass contains stored energy from the sun. Plants absorb the sun’s energy in a process called photosynthesis. When biomass is burned, the chemical energy in biomass is released as heat. Biomass can be burned directly or converted to liquid biofuels or biogas that can be burned as fuels.
Biomasses are therefore, in addition to the essences cultivated specifically for energy purposes, all products of agricultural crops and forestry, including residues from agriculture and forestry, waste from agro-food products for human consumption or animal husbandry, residues, not chemically treated, of the woodworking and paper industry, all organic products resulting from the biological activity of animals and humans, such as those contained in municipal waste (the “organic fraction” of waste).
In the most general sense, therefore, we can consider Biomass all material of organic origin, both plant and animal, but to better outline this sector we can consider the three main supply chains that represent it:
- Wood chain
- Agricultural chain
- Waste and scrap chain
To exemplify some types of biomass, among the most common, we can mention: solid, liquid or gaseous fuels derived from these materials (either directly or as a result of transformation processes) are defined as biofuels, while any form of energy obtained through biomass conversion processes is defined as bio-energy.
The use of biomass has a great variability depending on the types of materials available and, over time, many energy conversion technologies have been developed, some of which can be considered at a level of development that allows their use on an industrial scale, others, however, more recent and very complex, need further experimentation in order to increase yields and reduce energy conversion costs.
Biomass energy, or bioenergy, is energy produced by the conversion of biomass directly to heat, or to a liquid or gas that can be converted to energy. Biomass energycan be produced by any material of organic-vegetable origin (trees, plants, farming or industrial waste, urban waste). Biomass energy is regarded as more of a valid resource for the environment than an answer to the energy shortage. As such the growth and informed use of the large quantities of vegetation across the world can contribute to improving the ecosystem through a greater level of carbon dioxide absorption.
The use of plants fuelled by biomass energy makes it possible to complete the so-called “carbon cycle”: the amount of carbon emitted through their use is the same as the amount absorbed by the plants to produce the same quantity of biomass. The process cycles fuelled by biomass generate bio-combustible subproducts such as bio-oil and methane gas. Elements that can be used to produce electricity and heat. Another economical electricity-producing technology is the direct combustion of dry biomass. Rather than developing new plants, this can take place in existing plants for a smaller investment.
Biomasses and fuels derived from them emit into the atmosphere, during combustion, an amount of carbon dioxide more or less corresponding to the amount previously absorbed by plants during the growth process. Carbon dioxide in the atmosphere is the main responsible for the greenhouse effect and the one accumulated in the biomass, even if it had already been in the atmosphere in the previous years and decades, at the moment of the cutting of the biomass was all absorbed in it and therefore it did not contribute anymore to the greenhouse effect.
With the combustion of biomass, all the carbon dioxide accumulated in them is instantaneously reintroduced into the atmosphere and this emission is particularly pronounced in the case of forest biomass, i.e. in the combustion of trees, perhaps tall trees that have accumulated carbon dioxide for tens or hundreds of years, felled specifically to be burned. If all the trees felled and burned are replaced by others, they will be able to reabsorb over the decades all the carbon dioxide released in the combustion and this allows to say to the proponents of the energetic use of forest biomass that their use for energy purposes does not cause the release of new carbon dioxide.
On the other hand, biomass has the following disadvantages:
- Due to economic necessity of operation it is a form opposed to policies to minimize waste production;
- Large areas are required due to low energy density;
- Demand for fertilizer use;
- Logistics issues for supplying the resource;
- Environmental/weather condition issues;
- Non-constant annual production.
Gasification (biomass gasification)
Biomass gasification is the thermal conversion process of biomass into a gas, by bio-gasification or thermal gasification, where solid fuel is transformed into a fuel gas (producer gas) with a gasifying agent (air, steam, etc.). In the latter, hydrogen is produced from high-temperature gasifying and low-temperature pyrolysis of biomass. The produced gas is normally a mixture of N2, H2, CO, CO2, H2O, CH4 and light hydrocarbons whose use in advanced applications is hindered by the presence of contaminants such as tar, ammonia and particulates.
- Biofuel (biomass fuel)
- How to Boost Plant Biomass: NYU Biologists Uncover Molecular Link Between Nutrient Availability and Plant Growth Rates. https://www.nyu.edu/about/news-publications/news/2020/may/how-to-boost-plant-biomass.html
- Biomass explained. U.S. Energy Information Administration (EIA). https://www.eia.gov/energyexplained/biomass/