Spain’s Green Revolution: Pioneering Digestate Pasteurization Unlocks Agricultural Potential
SOUTHERN SPAIN – In a significant stride towards sustainable energy and agricultural practices, a newly operational anaerobic digestion plant in southern Spain has become the first in the nation to integrate a Digestate Pasteurization System, supplied by HRS Heat Exchangers. This innovative installation not only bolsters the plant’s operational efficiency but also sets a precedent for maximizing the value of agricultural and livestock residues.
The inclusion of this dedicated treatment stage for digestate is crucial for the plant to adhere to stringent European animal by-product regulations, paving the way for the material’s potential use as a valuable agricultural fertilizer.
Construction of this cutting-edge facility commenced in 2025, with an ambitious target of producing 58 gigawatt-hours of biomethane annually at full capacity. This renewable gas will be seamlessly injected into Spain’s national grid, with projections indicating it could fulfill the energy demands of approximately 11,000 homes each year.
Pasteurization Prepares Digestate for Agricultural Reuse
The plant’s feedstocks are diverse, encompassing agricultural and livestock residues such as olive pomace, whey, pig slurry, and chicken manure. While anaerobic digestion efficiently converts these organic materials into renewable gas, it also yields digestate—a nutrient-rich byproduct with significant potential for farmland application.
Given that the input materials include animal by-products, the digestate must undergo pasteurization before it can be safely used in agriculture. This essential treatment is mandated by European Regulation (EC) No. 1069/2009, designed to mitigate the risk of pathogen transfer to soils, crops, or livestock.
The HRS system is engineered to process an impressive 220 metric tons of digestate per day. Its continuous operation is facilitated by three holding tanks, allowing for simultaneous filling, pasteurization, and emptying in separate vessels.
At the heart of the system is a corrugated double-tube heat exchanger, which precisely elevates the digestate’s temperature to 167 degrees Fahrenheit. A key design feature of the system is its ability to adapt to variations in feedstock temperature and consistency—a critical advantage for facilities handling a diverse range of organic wastes.
For farmers, this project presents an additional pathway for managing livestock and food-processing residues. The resulting digestate holds the promise of offsetting some of the reliance on synthetic fertilizers. However, the overall environmental benefit will be influenced by factors such as transport distances, nutrient application practices, and the quantity of conventional fertilizer it ultimately replaces.
Heat Recovery: A Cornerstone of Energy Efficiency
To further enhance the sustainability and economic viability of the pasteurization process, the HRS system incorporates a sophisticated heat recovery mechanism. This ingenious design transfers thermal energy from treated digestate to the colder material entering the process, significantly reducing the overall energy demand.
HRS estimates that this heat-recovery arrangement can recapture up to half of the process’s thermal energy. The supplier projects annual savings of approximately 1.75 million kilowatt-hours of heat and an impressive reduction of about 375 metric tons of carbon dioxide emissions.
It is important to note that these figures are supplier estimates and not independently verified operating results. Actual performance will be subject to various factors, including plant utilization, incoming digestate temperature, feedstock composition, and daily operating conditions.
HRS provided the equipment as a comprehensive turnkey package, encompassing pumps, tanks, controls, instrumentation, valves, pipework, and the crucial heat exchangers. The company stated that its client selected the system after a thorough review of comparable installations at anaerobic digestion plants in other countries, underscoring the system’s proven effectiveness.
This pioneering project also mirrors the broader expansion of Spain’s biomethane sector. HRS reported a significant increase in operational biomethane plants in Spain, from 12 in 2024 to 25 in 2025, with projections anticipating 46 by the end of 2026, and up to 90 additional projects potentially coming online during 2027.
These projections, however, remain contingent on critical factors such as permitting, financing, reliable feedstock supply, and access to the existing gas grid. As more biomethane projects advance, effective digestate management is increasingly moving from an ancillary consideration to a central element of commercial and regulatory planning.
For developers, robust digestate treatment solutions like pasteurization directly influence operating costs, foster successful agricultural partnerships, ensure environmental compliance, and garner vital local support. The Spanish installation serves as a compelling early case study, demonstrating how advanced pasteurization and heat recovery technologies can be seamlessly integrated into large-scale biomethane facilities, driving both environmental benefits and economic efficiency.
