The introduction of iron oxides in the process of biomethanisation of organic waste has considerably reduced the levels of H2S, the main cause of bad odours
The intensity of the odour at the plant could be further reduced after the implementation of a pilot test of a deodorisation system in the biomethanisation hall
Maresme Circular, the brand of the Maresme Waste Consortium, has begun to successfully apply an innovative solution to reduce the odorous impact of the Maresme Integral Centre for Waste Recovery. This involves the introduction of natural iron oxides in the digesters of the biomethanisation plant in order to reduce hydrogen sulphide (H2S) – the main cause of bad odours – from the decomposing organic matter.
Due to this, an 80% reduction in H2S concentration has been achieved since the iron oxides were incorporated, from 2000-3000 ppm in 2022 to the 400-500 ppm currently recorded. In addition, the intensity of the odour at the plant could be further reduced after the implementation of a pilot test of a deodorisation system in the biomethanisation hall.
How does it work?
The Maresme Integral Centre for Waste Recovery treats 100,000 tonnes of organic matter each year from the remainder fraction of the Maresme and Vallès Oriental regions. Once separated from the rejected material, this organic waste is treated by the anaerobic digestion process and transformed into biogas. During this biomethanisation process, the organic matter generates hydrogen sulphide, a colourless, flammable gas that smells like rotten eggs and is the main cause of the odorous impact of the plant and its surroundings.
The iron oxide used is a compound of iron ore from the Teruel mines that reacts with hydrogen sulphide and neutralises it. In addition to reducing the concentration of odours in the biomethanisation plant, the iron oxides provide other advantages: it is a natural product that is non-toxic and non-corrosive and helps to increase biogas production.
Investment of €75,000 per year
This measure has been introduced after the concessionary company of the Maresme Integral Centre for Waste Recovery, UTE TEM (Maresme Ecological Treatments), studied its application and good results in other state waste treatment plants such as the Valdemingómez Technological Park (Madrid).
The cost of this solution is €40,000 for the purchase of an automatic iron oxide dosing system and €75,000 per year for the estimated 160 tonnes of iron oxides needed anually.
Pilot test of a deodorisation system
In mid-April this year, Maresme Circular also launched a pilot test of a deodorisation system in the biomethanisation plant. An odour-inhibiting agent made up of natural and synthetic plant essences is dispersed in a nebulised form through pipes located at a great height in the building. The concentration values of odour units are currently being measured to assess the results of this system.
These two measures are part of the action plan that Maresme Circular is implementing with the aim of minimising the odour impact of the Centre in the short term and are in addition to other actions carried out such as the improvement of the seals and ventilation systems of the biomethanisation building.
The Maresme Integral Centre for Waste Recovery / Marga Cruz
