Biogas is one of the most promising renewable alternatives for decentralized energy generation. Its production from organic waste allows for the recovery of materials that would otherwise be discarded, offering a sustainable and circular energy source. However, its use presents certain technical challenges, including the presence of hydrogen sulfide (H₂S), a highly corrosive and polluting compound that must be eliminated to ensure the viability of the process.

An invisible enemy: H₂S in biogas

H₂S is generated naturally during anaerobic digestion, especially when processing sulfur-rich waste, such as manure, sewage sludge, or agro-industrial waste. This gas, in addition to being toxic at high concentrations, causes corrosion in engines, pipes, and power generation systems, resulting in shutdowns, breakdowns, and additional maintenance costs.

Furthermore, its combustion can generate sulfur dioxide (SO₂) emissions, which prevents compliance with current environmental regulations.

Methods for Biogas Desulfurization

There are different approaches to removing H₂S, which are applied depending on the size of the plant, the sulfur content, and the destination of the biogas:

Adsorption on solids such as activated carbon or metal-impregnated zeolites, especially useful for low concentrations.
Chemical washing with alkaline solutions, which neutralize the gas but generate liquid waste.
Biological treatments, such as biofilters or biotrickling filters, which use bacteria to oxidize H₂S to sulfur or sulfate.
On-site solutions, which involve adding materials to the digester that react directly with H₂

This last system has gained prominence due to its operational simplicity and low cost. One of the most widely used techniques is the addition of iron oxides, which precipitate H₂S as iron sulfide. This is a clean method, generating no liquid waste and offering the potential for valorization of the byproduct generated.

Iron Oxide Desulfurization: Proven Effectiveness

Among the solutions employing this technology, the use of mixtures of iron oxides and hydroxides specifically formulated for this purpose stands out. Companies such as Promindsa have developed products designed for direct application in the digester, allowing H₂S to be captured at its source without the need for additional equipment.

These systems offer several advantages:

Reduced maintenance costs.
Improved stability of the digestive process.
Ease of use.
Direct application without modifying the facility.

Furthermore, the resulting product can be used as an agricultural fertilizer, thus closing the waste recycling cycle in a circular economy context.

A Strategic Decision for Biogas Plants

At a time when biogas is gaining importance as a renewable energy source, optimizing its quality from the source is more important than ever. Removing hydrogen sulfide not only improves the performance and durability of the equipment, but also opens the door to more demanding upgrading processes, such as the production of biomethane for grid injection or vehicle use.

The choice of an appropriate desulfurization method must consider the balance between efficiency, sustainability, and operating costs. In this regard, the addition of iron oxides on site is established as one of the most effective solutions for small and medium-sized facilities, both in the agricultural sector and in industrial plants.

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