Advantages and disadvantages of biogas: 5 questions about this renewable energy

Biogas is one of the main sources of renewable energy, whose production is constantly growing and decisive for a future that provides for the elimination of fossil fuels by 2050, according to the objectives set by the Paris Agreement. Let’s discover together how and where it is produced, what are the advantages of biogas and how innovation and new technologies, such as BioBANG®, can help reduce the disadvantages it presents and optimize and improve its production.

1) How does the production of biogas take place?

Biogas is a natural gas composed of various types of gases deriving from the fermentation of biomass of various origins. It consists primarily of methane and carbon dioxide, as well as small amounts of other gases.

The biogas production can take place in two ways: through the process of anaerobic respiration, without the aid of oxygen, or, of course, through aerobic respiration, by large quantities of biomass of different types such as: biological waste, zootechnical wastewater, etc.

Biogas plants utilize the process of anaerobic fermentation to produce biogas: in the absence of oxygen, an organic substance is transformed into biogas, a gas consisting mainly of methane and carbon dioxide.
It is a biochemical process that exploits the action of different groups of micro-organisms present in nature, which transform the organic substance first into acetic acid, carbon dioxide and hydrogen and then into methane. This process needs an optimal environment, with neutral pH and a temperature of around 35 C for a period ranging from 14 to 16 days with the use of mesophilic bacteria; 55 C for 14-16 days if thermophilic bacteria are employed.

Biomass used for the production of biogas can be of animal, vegetable or waste origin. These are mostly agricultural waste biomass or bio-waste, originating from several sectors:

  • Zootechnical (livestock waste);
  • Agroindustrial (agricultural and animal by-products);
  • Agricultural production (crop waste and residues);
  • The organic fraction of solid organic waste or FORSU(material from the separate collection of organic waste);
  • Dedicated crops (silage, maize, triticale, sorghum, rye);

Depending on the biomass used in the energy production process, the types of pretreatment also vary, as well as those following the biogas production process.

The use of waste biomass is certainly one of the main advantages of biogas that allows to produce energy in a completely natural form from waste materials that otherwise would not be used by any other industry.

Advantages Biogas - BioBANG® with agricultural waste
A biogas plant built near agricultural fields to reuse waste and produce energy.

2) How does a biogas plant work and how much does it cost?

Biogas plants work using anaerobic digestion to produce biogas from biomass: in the digester, in the absence of oxygen, enzymes and specialized bacteria are activated that ferment biomass, determining the production of biogas.
The operation of a biogas plant, its technologies involved and structures, may vary with respect to the type of biomass used.

The structure of a biogas plant is usually as follows:

  • one or more tanks where biomass is mixed and pre-treated to prepare it for fermentation;
  • one or more anaerobic digesters, where fermentation takes place: here the digested by-products precipitate downwards, while the biogas produced is directed towards the upper part of the digester;
  • a storage tank for digested biomass and unused materials during digestion;
  • a gasometer, where biogas is stored and taken for use as fuel.

Before deciding whether to install a biogas plant, it is necessary to assess whether you have a large amount of vegetable or animal waste to use and whether the land where it will be built has an area of at least three hectares.

The total cost for the installation of a biogas plant is generally quite high and varies depending on the production of gas that you want to achieve, the volumes of tanks (for materials more difficult to ferment need larger volumes) and the type of technologies for loading, pretreatment and mixing the biomass that are used.

In recent years in Europe, many incentives and economic aid have been allocated to support the construction of plants and the sale of biogas resulting from them.

3) What are the advantages of biogas?

The advantages of biogas are many and significant:

  • It valorizes and exploits waste biomass and by-products to produce energy, reducing the environmental impact of waste treatment and that caused by the distribution of traditional fossil fuels;
  • It contributes to the realization of the green economy expected for the future, to the achievement of a circular economy model and a more sustainable use of energy, careful to the protection of the environment;
  • Reduces carbon dioxide emissions. The combustion of biogas does not give rise to additional CO2 compared to that previously used by vegetable or animal biomass, unlike fossil fuels that produce it from scratch;
  • Allows energy diversification. The use of biogas reduces dependence on traditional energy sources and is one of the choices of clean and sustainable energy;
  • In addition to generating electricity, it also produces heat. In fact, biogas can be used both to generate electricity and to meet the demand for heating.
  • It can be delivered in a continuous form because the energy from biomass is adjustable at will and can be blocked when desired, as well as fossil fuels.
  • Biogas plants are easier to build and implemented technologies are less sophisticated and easier to find. There is therefore a reduction in costs and a lower investment in their construction than other renewable energy plants;
  • Biogas, once purified from impurities and CO2 removed, can be transformed into biomethane. Subsequently, it is transported and used through traditional infrastructure, allowing countries to reduce emissions in some difficult sectors, such as heavy industry and freight transport.

4) And what are the disavantages?

Nothing is perfect. Even biogas, despite the countless advantages listed above, presents problems related to its production and use:

  • To power a 1MW power plant, at least 300 hectares are required, as minimum usable area. Large quantities of land must therefore be available;
  • The sewage used emits bad smells: it is therefore necessary that the plants are sufficiently far from the inhabited areas to ensure a state of comfort for citizens;
  • Transport: if the plant is located far away, suitable means of transport will be needed to transport the raw materials, as well as the final products. High traffic leads to high carbon dioxide emissions;
  • The use of waste biomass and by-products for gas production is not easy. Their high fibre concentration can limit the digestion of bacteria, which therefore implies problems related to mixing and the formation of surface crusts that lead to an increase in self-consumption and a reduction in the production of the plant

The use and production of biogas is currently a viable, effective and for the most part a sustainable solution, but technological improvements are needed so that even the few disadvantages resulting from it can be solved.

5) Why is it important to use efficient biomass pretreatment technologies?

Biogas Advantages - BioBANG® powered by manure
BioBANG® installed in a biogas plant in Bergamo (Italy), fed with manure
The biomass pretreatment is one of the keys to the best use of organic waste and thus enhance the production of a biogas plant. Technologies that allow to completely disrupt biomass, make it more homogeneous and reduce their retention time, are therefore necessary to ensure their effective loading and their complete digestion in the plant and help to reduce some disadvantages of biogas previously treated.
BioBANG® controls a phenomenon already present in nature, cavitation, to disrupt, homogenize and liquefy the biomass that are loaded into the plant, to ensure their easy mixing in digesters and their complete digestion in the retention times of the plant. BioBANG®, releases all the energy produced by cavitation directly into the fluid, without intermediation of mechanical parts, disrupting all mass. Thanks to the unique action of controlled cavitation, biogas plants can optimize their management efficiency, energy and production, enhancing the use of waste biomass, without having problems related to their loading, mixing and poor digestibility.

How to successfully manage the change with waste fibers in your plant? Read our article »

Moreover BioBANG®, working in recirculation on the digester, concentrates its cavitation action only on the biomass more difficult to digest than, not being hydrolysed, fleet on the surface. BioBANG® takes this undigested material, the cavity and recirculates it in the lower part of the digester, already soluble and ready to be attacked by bacteria and produce gas. With the installation in recirculation, brings the unique benefits of cavitation with maximum energy efficiency, because it does not treat biomass that are already digestible for bacteria, without the need for pretreatment.

Watch how BioBANG® works in this video »

The use of BioBANG® innovative technology therefore allows biogas plants to be more efficient, productive and sustainable as they can use waste biomass, optimizing agricultural production and reducing transport consumption. Thanks to BioBANG® it is therefore possible to complete the production cycle of organic agricultural and industrial waste, with a view to an increasingly green, zero km and circular economy.