The biogas sector has potential with slurry and fertilizers

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The biogas sector in Spain is committed to placing its plants at the center of the transformation of slurry and manure to produce fertilizers, creating new possibilities in the management of livestock waste and field fertilizer.

This was stated in an interview with Efeagro by the vice president of the Spanish Biogas Association (Aebig) and director of the specialized company Biovic, Luis Puchades, who highlights the potential of this circular economy model in Spain.

Biogas plants usually treat slurry, manure, chicken manure and other products rich in nutrients such as nitrogen, phosphorus and potassium, the mixtures of which in turn function as fertilizers.

For Puchades, the potential for integrating these plants with the livestock sector is “very high” and contributes to avoid environmental problems such as excess slurry application, drilling into aquifers or bad odors.

Plants not only biogas

Biogas plants not only act as recipients of these by-products and produce the gas that is later recovered by injecting it into the network or for energy consumption, but also offer other options such as slurry “regulating” centers.

Vila-Sana biogas plant (Lleida).  Epheagro/Biovic
Vila-Sana biogas plant (Lleida). Epheagro/Biovic

“Slurry is produced every day of the year on farms, but it can only be applied to the field at certain times of the year,” says Puchades.

In the midst of this dichotomy, the factory can receive the slurry every day, process it and apply it correctly in the field, minimizing odor problems, eliminating bacteria, facilitating logistics and contributing new sources of income and energy such as those represented by renewable gas.

Puchades specifies that most of the biogas plants in Spain are applying the digestates -by-products resulting from the anaerobic digestion of biomass in the biogas production processes- to agriculture through various forms of treatment.

“Composting plants can also be associated with biogas plants to make a more processed product or even use some digestate concentration plants to concentrate those nutrients and try to minimize logistics in the field,” he points out.

The vice president of Aebig maintains that, if the product resulting from these plants is currently being used as organic fertilizer in agriculture, in the future more hybrid processing will be sought to obtain finished fertilizers, products that can be applied in drip irrigation or concentrates. that contemplates the new fertilizer regulations.

In Spain there are biogas plants that are producing registered fertilizers and “the path of the sector is heading in that direction,” says Puchades.

a new industry

More than 200 facilities of this type operate in the country, many of which will go from being conventional electricity or heat production plants to biomethane plants, according to industry estimates.

It is estimated that a standard biogas plant produces between 20,000 and 50,000 cubic meters of digestedbut if the renewable gas industry develops as in other European countries, the potential volume can be “huge”, millions of tons.

However, Puchades acknowledges that there is not yet “the relationship that there should be” with the fertilizer industry, although “little by little there is beginning to be more interest in that industry to use these digestates as raw material and then formulate fertilizers.”

In the coming years, he predicts, progress will be made in this regard, since “knowledge from the world of fertilizers will have to be applied to biogas plants when formulating products, marketing them and guarantee its homogeneity and quality”.

The context is propitious, since the regulatory changes are expected to reward organic fertilization against the uses of chemicals in agriculture and the recycling of nutrients with a view to improving sustainability.

Currently, with the prices of chemical fertilizers skyrocketing in the European Union due to the war in Ukraine and the increase in energy costs, the price per unit of nutrient is lower in the case of organic fertilizers, says Puchades.

Although it is necessary to take into account the logistical costs and the efficiency of the projects, the director of Biovic believes that “very cheap fertilizers that are profitable and viable” can be achieved.

In his opinion, all renewable gas companies must have an “agricultural component”, because “if agriculture and local livestock do not interact well, they will not be viable” and the same occurs with the recovery of digestates for fertilizers.

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