Biogas consists of a mixture of different gases, mainly methane and carbon dioxide, generated through the anaerobic fermentation (in the absence of oxygen) of organic material of plant or animal origin.
These materials can come from a variety of sources, such as waste from the agro-industry (e.g. maize chopping, sorghum or other crops), the food industry (such as waste meal or expired products) and the livestock industry (animal waste or carcasses). In addition, specific crops can be used to produce ‘biomass’, such as maize, sugar sorghum, wheat, common cane and beets.
The biogas production process involves the decomposition of organic material by certain bacteria that produce carbon dioxide, hydrogen and methane.
Bellin progressing cavity pumps and Bellin’s lobe pumps have been successfully used in various production steps of the biogas production process, ensuring efficiency and reliability.
The fermentation process involves the addition of organic mass to a first fermenter, where it is homogenised using a TM or LTM series progressing cavity pump. This pump facilitates mixing between the coferments and liquid substrate, ensuring uniform distribution.
In some plants, there is a collection tank in which both the liquid and solid matrix are combined. In these situations, the use of an NPL lobe pump, combined with an upstream macerator, is recommended. This solution optimises the efficiency of biogas production, ensuring a constant and adequate feed to the fermenter.
Fermentation takes place in three separate biological steps, using an organic mass with a dry matter content of between 5 and 15 per cent. The phases are: the hydrolytic phase, the acidogenic phase – divided into two sub-phases – and the methane production phase. Once fermentation is complete, the fermented pre-substrate is transferred to the post fermenter for further treatment or use.
The recirculation of the organic mass within the fermenters, carried out by means of progressing cavity pumps and/or lobe pumps, plays a crucial role in the fermentation process. Ineffective recirculation can compromise methane production, limiting the overall efficiency of the process.
The methane produced is fed to the cogeneration engine station, where it is used to generate electricity and heat for heating, contributing to a sustainable and efficient energy supply.
The residual biomass, known as digestate, is used as fertiliser or subjected to composting treatments, turning the by-products of the process into useful and environmentally friendly resources.