The Renewable Gas Show is one of the most important events in the bioenergy sector in Spain.
SITRA has been present since its first editions, and in this year's edition, which is held on September 29 and 30 at the Valladolid Fair , we return with something concrete to show: the results of our own research on anaerobic co-digestion with agro-industrial by-products , developed in our laboratory and validated on a pilot scale.
In this article we explain what this work involves, what we have learned, and why we believe it opens up a very interesting avenue for the industry.
The starting point: two waste products with great potential and a common problem
Spain generates millions of cubic meters of pig slurry each year; the country has around 33-34 million pigs , making it the main producer in the European Union.
At the same time, the olive oil industry generates alpechín, a liquid effluent with a high organic load, high acidity and phenolic compounds that make it difficult to treat by conventional methods.
Both types of waste have something in common: they are abundant, they create a real management problem for the companies that produce them, and they contain energy and nutrients that can be used if they are treated properly.
Conventional anaerobic digestion of each separately has known limitations. Slurry, due to its high concentration of ammonia nitrogen, can inhibit the biological process. Olive mill wastewater, due to its low pH and polyphenols, also presents resistance. Co-digestion of both in appropriate proportions allows these limitations to be overcome.
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That was the starting hypothesis of our research.
From the laboratory to the pilot plant: how we work at SITRA
At SITRA, we have our own laboratory where we conduct BMP ( Biochemical Methane Potential ) tests , which allow us to measure the biogas production potential of a substrate before scaling up the process. This is the first filter: if the numbers don't add up on a small scale, there's no point in building anything larger.
With validated BMP trials, and if the project requires it, at SITRA we can design and build a custom anaerobic digestion pilot plant , as we did in the case of Serena with a two-phase temperature-controlled (TPAD) configuration. However, this is not a fixed step in the process: each case is evaluated individually.
This configuration separates the hydrolysis-acidogenesis and methanogenesis stages into two independent reactors, each operating under its optimal conditions. The result is a more stable, efficient process that is less susceptible to the inhibition phenomena that often occur with complex substrates such as olive mill wastewater.
The pilot plant, with two 2 m³ digesters , operated in a fully automated manner and was designed for remote operation. This is a crucial detail: replicating real-world operating conditions on a reduced scale is what ensures that the data obtained can be extrapolated to an industrial plant.
Co-digestion was evaluated with a mixture of pig slurry and olive mill wastewater in a 60:40 (v/v) ratio, analyzing its behavior during the start-up phase and in steady-state conditions.
The results: biogas, quality water, and nutrient concentrate
The results confirmed the technical feasibility of the process . The TPAD configuration achieved operational stability and efficient biogas production , even with a substrate as demanding as olive mill wastewater.
But the process doesn't end with biogas. The final effluent from digestion, the digestate, was subjected to valorization treatment using VSEP ( Vibratory Shear Enhanced Processing ) vibratory membranes , a technology that uses high-frequency vibrations to minimize membrane fouling and maintain high filtration rates.
The result was three distinct value streams:
- Biogas as a renewable energy source, with the potential to be upgraded to biomethane.
- High-quality permeate, with a water recovery rate of over 90% and absence of pathogens (Salmonella, Listeria monocytogenes and E. coli not detected in any of the streams analyzed).
- Nutrient-rich concentrate — ammoniacal nitrogen, phosphorus and potassium — with potential as an agricultural biofertilizer.
This integrated approach is what distinguishes the SERENA plant as a benchmark project: it is not just about treating waste so that it ceases to be a problem, but about turning it into three resources with real economic value.
From research to real project
The journey from laboratory to pilot plant to industrial project is what lends credibility to any technology. At SITRA, this journey is not theoretical: the lessons learned from the Serena pilot plant are being integrated into how we design and operate real-world facilities.
In parallel, our WIM by SITRA platform , the proprietary industrial data monitoring and management system that connects field sensors, smart alarms and real-time trend analysis, is the tool that makes it possible for all that knowledge to be translated into operational decisions.
At an operating biomethane plant, WIM detected an upward trend of H₂S before it reached critical levels , allowing an intervention costing €6.000 and preventing the loss of €45.000 in biomethane invoiced that month.
That is the bridge between research and operation: knowing what is happening at the plant at any given moment and having the necessary information to act before the problem becomes irreversible.
Download the WIM success story — €45.000 recovered with a €6.000 investment
Come see it at the Renewable Gas Show: Stand 235 of SITRA
On September 29th and 30th, we will present the progress of the Serena project at the Salon and you can see live how WIM works in a real biomethane plant.
At our booth number 235 you will find:
- Touchscreens with the actual WIM interface operating on the plant floor.
- A simulator where you can enter the data of your own installation and see how the system would respond.
- Virtual reality glasses for visualizing bioenergy projects in 3D.
- Our technical team is available to discuss your specific case.
If you want to make sure you speak to someone from our team, schedule an appointment before you come.
Schedule your appointment at the Salon
Frequently Asked Questions about the Renewable Gas Show
Where is the Renewable Gas Show held? At the Valladolid Fairgrounds, Ramón Pradera Avenue, number 3.
When is this year's Renewable Gas Show taking place? On September 29th and 30th, 2026.
How much do tickets to the Renewable Gas Show cost? Access to the exhibition area is free. The International Bioenergy Congress, which runs concurrently, costs €300 and includes access to conferences, meals on both days, the poster session area, and materials.