An in-depth analysis and update of an article that appeared in issue 08-09/2025 of the magazine ConsulenzaAgricola.it
Legal review by Atty. Francesco Tedioli – Tedioli Law Firm, Mantua.
Understanding photocatalytic filtration: Principles and mechanisms
In recent years, agriculture has experienced a progressive expansion of technologies employed not only to support production but also to manage environmental quality and product integrity in the post-harvest phase. Among the most promising innovations in this field is photocatalytic filtration, an advanced air purification technique based on the use of light-activated catalytic materials. Originally developed within scientific and industrial circles, this technology has recently found applications in the agricultural sector, proving effective in addressing two particularly pressing challenges: the management of odor emissions and the preservation of fruit and vegetable products.
The unique feature of this system lies in its ability to degrade organic molecules and air pollutants rather than merely trapping them, as traditional filters do. This effect is made possible by the use of titanium dioxide (TiO₂), a material that, when activated by ultraviolet light, generates highly oxidative free radicals. These radicals are capable of breaking down undesirable substances into harmless elements, such as carbon dioxide, water, and mineral salts.
Scientific Evolution: From the Japanese Discovery to Advanced Air Remediation
The scientific basis of photocatalytic filtration lies in the phenomenon of heterogeneous photocatalysis, an oxidative process that occurs on the surface of a solid catalyst in the presence of light. By far the most widely used material is titanium dioxide (TiO₂), specifically in its anatase crystalline form.1, characterized by a band gap of approximately 3.2 eV, which can be activated by UV radiation (wavelength < 385 nm).
The birth of environmental photocatalysis is commonly traced back to the 1972 publication of Fujishima and Honda’s studies on the photoelectrolysis of water using TiO₂ electrodes illuminated by sunlight.2. Starting in 1977, this experimental evidence sparked extensive research into the potential of TiO₂ for the degradation of toxic substances, such as phenols, pesticides, and chlorinated compounds. Since then, the use of TiO₂ has expanded to the treatment of wastewater, air, and surfaces, due to its ability to generate oxidative species (for example, hydroxyl radicals OH, superoxides, and peroxides) capable of attacking and decomposing complex organic and inorganic molecules.
More recent studies confirm the effectiveness of nanostructured photocatalytic materials in the abatement of pollutants, with degradation levels exceeding 80% under controlled conditions.3 .
Nature-Inspired Filtration: Understanding the Role of TiO2 and UV Light
To understand the mechanism of photocatalytic filtration, it is helpful to draw an analogy with a process familiar to every farmer: chlorophyll photosynthesis. This natural mechanism allows plants to transform solar energy into nutrients using carbon dioxide, water, and mineral salts. The process is made possible by chlorophyll which, once activated by light, enables the synthesis of complex molecules (primarily carbohydrates) that are essential to plant life.
Heterogeneous photocatalysis is inspired by a similar principle: in this case too, a catalyst—titanium dioxide (TiO₂)—is activated by a light source, typically ultraviolet. The irradiation of TiO₂ generates electron-hole pairs on its surface, which trigger the formation of oxidizing radical species capable of attacking and degrading contaminants in the surrounding environment. The complex molecules of pollutants (odors, ethylene, volatile organic compounds, or microorganisms) are thus broken down into simpler, harmless products: CO₂, H₂O, and inert minerals.
The operational value of this mechanism is significant from a dual perspective. First, the catalyst used (typically titanium dioxide) is not subject to consumption during oxidative reactions; therefore, it can be reused across numerous cycles without the need for frequent replacement. Second, the photocatalytic process is distinguished by the absence of additional chemical reagents and the lack of hazardous by-products or toxic residues, establishing itself as a low-environmental-impact solution.
As a technology that has now reached application maturity, photocatalytic filtration is currently finding its place within the agricultural sector. It offers concrete advantages in protecting air quality within confined environments and in extending the shelf-life4 of fruit and vegetable products and in the management of odorous emissions. This is not a theoretical prospect: photocatalytic reactions have been the subject of experimentation and application for over forty years and currently constitute reliable and strategic tools for promoting increasingly sustainable and innovative agricultural models.
Applications in the Fruit and Vegetable Sector: Ethylene Abatement and Post-Harvest Preservation
Tra le applicazioni più promettenti della filtrazione fotocatalitica in ambito agricolo rientra la possibilità di prolungare la vita commerciale dei prodotti ortofrutticoli mediante la selective removal of ethylene, ormone vegetale gassoso che accelera i processi di maturazione e, conseguentemente, il deperimento dei vegetali.
Ethylene (C₂H₄) is a molecule naturally emitted by numerous fruits and vegetables, particularly by species defined as 'climacteric,' including apples, bananas, kiwis, tomatoes, and avocados. Post-harvest, in enclosed spaces or cold storage rooms, this gas tends to accumulate and triggers accelerated ripening which, if left unchecked, rapidly compromises the marketable quality and shelf-life of the product.
TiO₂-based photocatalysis has proven effective in reducing airborne ethylene concentrations, contributing to the deceleration of senescence processes. Experimental studies conducted at the Vegetable Research Institute of Tottori University (Japan) have shown that the use of TiO₂ photocatalysts, activated by UV sources, can reduce ethylene concentrations by over 80% in less than eight hours within simulated storage cells containing climacteric fruit. Of particular interest for visual demonstration is the test that immediately documents the contrast between photocatalytic treatment and the absence of treatment.5
Closed-loop photocatalytic systems, specifically designed for use in refrigerated storage environments, are now available in Italy. The integration of TiO₂-based filters in these settings helps reduce the incidence of accelerated ripening, thereby helping to preserve the tissue firmness and original color of fruits and vegetables for significantly longer periods than in environments without photocatalytic filtration systems.
The system’s operating principle is characterized by a linear operational structure: air drawn from the storage environment is channeled into a module containing photocatalytic filters paired with LED light sources, which provide the ultraviolet radiation necessary for catalytic activation. Exposure of titanium dioxide (TiO₂) to UV rays triggers the formation of oxidizing species on the catalyst’s surface, causing ethylene molecules to break down into carbon dioxide and water. The treated air is then recirculated into the storage rooms, ensuring an environment with reduced concentrations of ripening accelerators.
The process requires no addition of chemicals or external maintenance: once installed, the system requires only the periodic replacement of the photocatalytic filters (typically on an annual basis), while the low-energy LED light sources have a service life of several years.
This approach, in addition to being technically effective, is characterized by environmental sustainability and cost-effective management, offering agricultural businesses and fruit and vegetable cooperatives the opportunity to:
• significantly reduce losses due to post-harvest waste;
• optimize the timing of marketing;
• streamline the costs associated with product storage.
Ultimately, this solution can contribute, on the one hand, to process innovation and, on the other, to more efficient management of the storage and marketing phases, aligning with the needs of short supply chains and quality-oriented agricultural models.
Management of Odorous Emissions in Livestock Farms and Dairies
In numerous agricultural and livestock sectors—ranging from intensive farming to dairies, through to composting and storage plants—odorous emissions represent a critical issue that is often underestimated. Although Volatile Organic Compounds (VOCs)6 are not always harmful to human health, their olfactory impact causes significant distress among local communities.
Specifically within dairies, the processing and ripening phases generate organic effluvia that can compromise the facility's social acceptance and corporate reputation, with potential repercussions on licensing procedures and overall business competitiveness.
Regulations and Liability: Article 844 of the Italian Civil Code and Odor Nuisance
Within this framework, a judicial trend has progressively consolidated in Italy in recent years aimed at strengthening protection against odor nuisance. This trend recognizes the legal significance of intolerable odorous emissions under Article 844 of the Italian Civil Code, regardless of whether the specific numerical limits set by environmental regulations have been exceeded.
The Court of Cassation7 has reaffirmed that the lawfulness of emissions must be evaluated not only based on quantitative parameters but also on the basis of their quality and impact on the normal enjoyment of property. In this context, the SNPA Technical Document 2025 ('Odorous emissions: reference elements and methodological approaches for monitoring') currently serves as the pivotal national reference for the monitoring and management of odorous emissions.
A Viable Solution: TiO₂ Photocatalytic Filtration
In this scenario, photocatalytic filtration emerges as an innovative, low-impact tool for mitigating odorous emissions. Unlike chemical masking systems, photocatalytic filtration does not mask odors but eliminates them through molecular decomposition. The process relies on the action of titanium dioxide (TiO₂), which, when activated by UV light, generates free radicals capable of irreversibly oxidizing odor-causing molecules, transforming them into harmless compounds such as CO₂ and H₂O.
This technology offers distinct advantages over simple physical retention, as it chemically transforms contaminants and provides a biocidal effect—meaning that, in addition to eliminating unpleasant odors, it inhibits the proliferation of bacteria, viruses, and mold. These benefits are complemented by low energy consumption and the absence of chemical additives.
Installing photocatalytic modules at the outlets of exhaust fans in critical areas (aging, packaging) allows for the neutralization of vented emissions before they are released outdoors, demonstrating a proactive approach during administrative inspections or legal disputes.
Sanitization and Antibacterial Action in Food Industry Processes
Photocatalytic filtration is not limited to purifying the air of organic compounds and odorous molecules; it also exerts a potent antimicrobial action.8, of significant interest for food processing environments. When exposed to UV radiation (and, in certain configurations, even to visible light), titanium dioxide (TiO₂) generates Reactive Oxygen Species (ROS). These species can damage microbial cells, interfere with biofilm formation, and contribute to the degradation of microbial components, including certain toxins.
Mechanism of Action
Light-activated TiO₂ produces oxidizing radicals—including hydroxyl radicals (•OH) and other ROS—which exert a simultaneous action on multiple biological targets, including: (i) cell membranes; (ii) genetic material (DNA/RNA); (iii) structural and functional proteins.
Due to the non-selective nature of these oxidizing species, the effect can impact a broad spectrum of microorganisms, including Gram-positive and Gram-negative bacteria, spores, fungi, and viruses. Concurrently, the process can contribute to the degradation of endotoxins without the catalyst being 'consumed' by the reaction, provided that suitable operating conditions (irradiation, active surface area, and contact times) are maintained.
Performance and Integration with UVC
The literature reports laboratory results (and, in certain applications, results from healthcare and industrial environments) highlighting significant reductions in microbial load on treated air and surfaces.9 In many cases, the efficacy is particularly evident in the presence of biofilms, where the combination of photocatalytic oxidation and proper airflow management can offer an additional contribution compared to systems based exclusively on chemical agents.
To enhance performance, some systems integrate UVC lamps, leveraging the germicidal action of ultraviolet light. This combined adoption (photocatalysis + UVC) allows direct disinfection to work alongside oxidative decomposition, providing significant benefits, particularly in environments with high hygienic criticality.
Operational Impacts on Agri-Food Plants
In practice, the use of photocatalytic systems for the sanitization of process air translates into the following advantages:
- Reduction of microbiological contamination of air in contact with food;
- Containment of foodborne pathogens (e.g., Salmonella, Listeria, E. coli), limiting or eliminating the use of airborne chemical substances;
- Support for maintaining HACCP standards and, more generally, internal hygiene and sanitation procedures;
- Reduction of non-compliance risk, with potential positive impacts in terms of product withdrawals/recalls and litigation;
- Deceleration of spoilage processes associated with airborne microorganisms and shelf-life extension of fresh and processed products;
- Reduction of waste due to contamination;
- Appreciable efficacy even in refrigerated environments, where certain chemical treatments may prove less effective;
- Adaptability to different process stages (storage, processing, packaging, ripening) and the possibility of integration into existing systems with limited interventions.
Operational Advantages for Agri-Food Enterprises: Why Choose Photocatalysis
Photocatalytic filtration is now a mature, effective, and sustainable technology that is fully applicable in the agricultural and agri-food sectors as well. The operational benefits it offers—in terms of improved air quality, extended shelf life of fruits and vegetables, and reduced odor emissions—make it a particularly attractive solution for addressing some of the most pressing challenges facing the primary sector: production efficiency, environmental sustainability, and social responsibility toward the local community.
The main advantages stem, first and foremost, from generally low energy consumption, especially when the system is powered by LED lighting (and, in theory, even zero energy consumption when using sunlight). Added to this are the system’s compact size and resulting ease of installation, along with an overall simple system design. From a management perspective, the system is also user-friendly: maintenance is minimal, and, as a rule, filters can be replaced independently without the need for specialized expertise. Finally, the system’s effectiveness in removing pollutants stems from the fact that the process occurs at the molecular level, through the degradation of unwanted substances rather than mere retention.
The adoption of these technologies also falls within the framework of incentive measures established at the regional and national levels to promote technological innovation in agriculture, as well as within the scope of programs and calls for proposals aimed at modernizing agri-food businesses.
For businesses operating in the fruit and vegetable supply chains, as well as in the logistics, poultry, and livestock sectors, the implementation of photocatalytic filtration systems does not require invasive structural modifications, as they can be functionally integrated into cold storage rooms, processing tunnels, or agricultural sheds. These devices therefore provide constant monitoring, safeguarding both the product quality and the health and safety of the work environments.
Ultimately, photocatalytic filtration emerges as a practical, replicable solution with low operating costs, capable of delivering measurable and verifiable benefits. In an agricultural context increasingly focused on quality, sustainability, and innovation, it can represent a strategic investment toward more efficient and safer production models that are compatible with the protection of people and the environment.
