Biogas is emerging as one of the cleanest, cheapest and most efficient sources of energy in the world, as it is obtained from organic animal waste. For that reason, is important to know what it is exactly and how it can be used in our production system.

What exactly is biogas?

Biogas is a source of energy that is obtained from the decomposition of organic materials in an anaerobic environment, that is, where there is little or no oxygen; this source appears as a mixture of different gases. This task is carried out by specialized bacteria that consume all this organic matter and produce mainly methane gas (CH4) and carbon dioxide (CO2). Biogas consists of 50-70% methane and 20-40% carbon dioxide. It also contains other less important gases such as: hydrogen sulfide (which gives it the smell of a rotten egg), nitrogen and water vapor. These last elements must be removed to obtain a clean and fully usable biogas.

What characteristics does it have?

Unlike other non-renewable energy sources (such as petrol, which is a fossil fuel and gradually runs out), Biogas is obtained from organic matter from animals such as food scraps, fecal matter, litter and others (all of this is known as biomass). This means that it is renewable, so it can be obtained as many times as you want without running out. On the other hand, it is obtained from organic materials so waste can be recycled.

Another important feature of biogas is that it has wide applicability: we can use it as a source of thermal energy (heat), electrical energy and as fuel. It is the only source of energy capable of being used in all these tasks at the same time.

In addition to the above, we must emphasize that the generation and use of biogas is cheaper compared to other sources of energy. As it is obtained from organic waste produced on the farm itself, and even in the houses located inside the farm, it has the great advantage of being easy to obtain. It is even mentioned that it can be as efficient as natural gas in terms of the energy capacity which can generate. When the biogas has been purified it can be connected to the natural gas pipes.

As a sample of all the above, the FAO, in 2012, recognized biogas as a promising energy source for Latin America. Given the difficulty of future access to other energy sources, biogas, being a clean energy, is imposed as a tool for the sustainability and energy independence of developing countries, both for small and medium producers and for large agricultural producers.

But… How do we get it?

First, the organic matter or biomass from which we will get the biogas must be obtained. This can come from the following sources:

• Animal origin: manure from cattle, swine, poultry and small ruminants, shed litters, urine, fish waste
• Human origin: feces, food waste
• Plant origin: stubble and litter, decomposed forages, residues of agricultural crops.

It should be noted that, among all these sources of waste, those that generate the most amounts of biogas are those from animal manure due to their high load of methane-generating (methanogenic) bacteria. That is why animal production systems are recognized as ideal when implementing a biogas system.

To obtain biogas we need something called an organic biodigester to complete the biodigestion process. This process consists of a series of stages that we will briefly describe below:

1. Hydrolysis: large biomass molecules are transformed into smaller molecules (example: lipids become fatty acids, proteins become amino acids, and carbohydrates become sugars).
2. Acidogenesis: the above simple compounds are transformed into even smaller ones, such as volatile fatty acids, hydrogen and carbon dioxide.
3. Acetogenesis: these acids generated are short-chain and are now converted into acetic acid (this process is reminiscent of the one that occurs in the rumen of animals).
4. Methanogenesis: finally, methane-forming bacteria transform this acetic acid into methane (CH4), hydrogen (H2) and carbon dioxide (CO2), that is, biogas.
5. Digestate: finally, in addition to the gases obtained, the digestate is obtained, which is a semi-solid material rich in minerals and organic matter that can be used as a soil fertilizer or conditioner.

To achieve an efficient biogas formation process optimal conditions of temperature, humidity, pH, bacterial load and other factors are needed. These conditions must be periodically analyzed and constant evaluations and review of the biodigester must be done. It is essential to keep records of all these measurements and to try to maintain the optimal conditions of everything for a correct execution.

What advantages does biogas provide?

Among its many advantages, the following stand out:

1. Economical: compared to other higher cost sources. Its implementation is economical and profitable
2. Ecological: it helps the environment by reducing the load of waste destined for collection sites or garbage dumps, it reduces the amount of leachate produced.
3. Efficient: it has great power as an energy generator and high performance in multiple processes that demand energy, be it thermal, electrical or carburation in the farm facilities
4. State benefits: some countries provide support to producers who implement clean energy like this
5. Socially accepted: the use of biogas provides social opportunities by linking the community of the same region in the process of training, installation and use of a community biodigester, strengthening ties and supporting networks between producers.
6. Sustainability: some regions with difficulties in access to energy or its payment, can implement this system to obtain their own energy in the long term and at low costs.

What possible difficulties does it present?

One of the most urgent difficulties to solve is the technical training in the installation, use and maintenance of the biodigester. However, once installed, it is known that its use is simple and easy to replicate in other farms. The cost associated with the biodigester and its technical challenges can vary and depends on several conditions: geographic location and access to supplies for its construction, terrain and environmental conditions, implemented biodigestion system, human team dedicated to its maintenance, private or community use, among other. It is recommended to ask for advice when implementing a biogas system.

CONCLUSIONS

Renewable energy sources are emerging as the basis of the world’s energy future, even more in animal production systems. The advantages that biogas provides are enough to safely recommend its implementation and use on any farm. Technical training is also recommended to optimize all the processes that involve its installation and use.

References:

• FAO, 2011. Manual de biogás. Disponible online en: http://www.fao.org/
• 2019. GuĂ­a teĂłrico-práctica sobre el biogás y los biodigestores. Disponible en: http://www.fao.org/
• Instituto para la DiversificaciĂłn y Ahorro de EnergĂ­a, 2020. SituaciĂłn y potencial de generaciĂłn de biogás. Estudio TĂ©cnico PER 2011-2020. Disponible online en: https://www.idae.es/tecnologias/energias-renovables/uso-termico/biogas
• Ministerio de Ambiente de Colombia, 2020. GuĂ­a de biogás para el sector porcĂ­cola de Colombia. Disponible online en: https://www.minambiente.gov.co/images/AsuntosambientalesySectorialyUrbana/pdf/Guia_Biogas
• Noticias ONU, 2012. FAO destaca al biogás como fuente de energĂ­a para agricultura en AmĂ©rica Latina. Disponible online en: https://news.un.org/

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