In the modern industrial context, the management of diffuse emissions represents a crucial challenge for companies, both in terms of regulatory compliance and environmental sustainability. Unlike stack emissions, diffuse emissions do not pass through chimneys or ducts, but disperse into the environment from open surfaces, tanks, plants, or production processes.
The growing attention of European and national authorities has led to a strengthening of the regulatory framework, with increasingly stringent environmental controls and direct responsibilities for companies. The main regulatory sources include Directive IED 2010/75, recently updated by Directive UE 2024/1785, and the D.Lgs. 152/2006 and its subsequent amendments.
European regulatory framework
Directive 2010/75/EU (IED)
The IED Directive governs Integrated Pollution Prevention and Control (IPPC) from industrial activities and requires the adoption of Best Available Techniques (BAT), reference documents on the best available techniques, documented in sector-specific BAT reference documents (BREF). A specific BREF has been developed for monitoring emissions into air and water from plants subject to the IED Directive on industrial emissions, known as ROM, Report on Monitoring. Non-channelled emissions must be monitored and documented in environmental management plans, with obligations of traceability and transparency.
Other EU references
At the EU level, it is important to mention the European Green Deal, which represents the Union’s strategy to achieve climate neutrality by 2050, promoting a profound transformation of the economy and society in a sustainable, fair, and resilient way. In this context, the legislative package “Fit for 55” is also important, aiming to reduce greenhouse gas emissions by 55% by 2030, integrating and strengthening emissions legislation with concrete objectives for sustainable technological transition.
Regarding air quality, Directive 2008/50/EC constitutes the European regulatory reference, recently updated by Directive UE 2024/2881. The latter introduces stricter limits and reduction targets consistent with the Green Deal and the ambition to achieve zero pollution by 2050, aligning limit values with the recommendations of the World Health Organization (WHO) and enhancing monitoring, modelling, and environmental governance tools.
National transposition and Italian regulatory framework
In Italy, the IED Directive was transposed through D. Lgs. 46/2014, which amended Legislative Decree 152/2006. This legislative intervention strengthened the national regulatory framework on air protection, introducing stricter obligations for industrial plants subject to Autorizzazione Integrata Ambientale (AIA). In particular, the decree incorporated provisions relating to the application of BAT, making them binding for the definition of authorization conditions and for emissions monitoring. The AIA ensures that plants operate in compliance with emission limits and environmental requirements, taking into account technical characteristics, location, and overall environmental impact.
The Ministry of Environment and Energy Security (MASE) has functions of guidance, coordination, and issuance of AIA for plants under state jurisdiction, while for activities of local interest, responsibility lies with the Regions or Provinces. The Regional Environmental Protection Agencies (ARPA) are instead responsible for control activities, verification of compliance with authorization conditions, and technical support in the territory.
Technical and managerial obligations for companies
Installations subject to IPPC regulations and falling under the AIA regime are listed in Annexes VIII and XII to Part Two of Legislative Decree 152/2006 and are subject to technical and managerial obligations aimed at environmental protection and full regulatory compliance. These include the binding application of BAT, periodic review of authorizations, and structured environmental controls.
In general, each plant is required to prepare and update an Environmental Management Plan, describing the measures adopted to prevent and reduce pollution, and an Annual Environmental Report containing emissions data, actions taken, compliance status, and improvement objectives.
With regard to the assessment of diffuse emissions, companies must identify and characterize all sources of non-channelled emissions, such as those arising from open surfaces, cracks, material handling, or other operational activities, evaluating the conditions that generate dispersion and the related environmental risk. The adoption of monitoring systems, both direct and indirect, is also mandatory, with continuous or periodic recording of emissions data, storage of information, and transmission to the competent authorities. Self-monitoring and traceability systems must also be implemented.
Some activities are not subject to AIA because they are considered to have low environmental impact. Small and medium-sized enterprises with a more limited environmental impact may fall under the regime of the Autorizzazione Unica Ambientale (AUA), a simplified procedure that consolidates multiple permits (discharges, emissions, waste), with less onerous technical and managerial requirements compared to AIA.
Tools and methodologies for controlling diffuse emissions
Diffuse emissions, including fugitive ones, can represent a significant share of the total emissions of an industrial plant, with considerable environmental impacts. For this reason, environmental authorizations and BAT conclusions provide, where necessary, specific measures for their monitoring and containment.
According to the relevant BREF, diffuse emissions are unchannelled releases of volatile or dusty substances, originating from point, linear, surface, or volumetric sources. Typical examples include loading/unloading operations, outdoor storage, separation tanks, building openings, and electrolytic cells. Fugitive emissions, on the other hand, are a subset of diffuse emissions and derive from localized equipment leaks, such as valves or flanges.
Quantifying these emissions is complex and often costly, both economically and operationally, due to the large number of sources and the uncertainty of measurements. To address this challenge, a combination of techniques is used: direct measurements, atmospheric modelling, and continuous monitoring.
Among European technical standards, EN 15445:2008 proposes reverse dispersion modelling to estimate dust emissions using environmental data measured downstream of the plant and meteorological data. This is useful for identifying the most relevant sources and planning reduction measures. EN 15446:2008 introduces the “sniffing” method, which employs portable instruments to detect VOC leaks from valves, flanges, and pipelines, widely used in leak detection and repair (LDAR) programs. EN 16253:2013 describes the use of DOAS (Differential Optical Absorption Spectroscopy) to measure gaseous compounds along open paths. This technique, based on light absorption along an open path, is particularly useful when direct measurements are not applicable. EN 15259:2007, although not specific to diffuse emissions, is useful for planning and documenting measurements.
In addition to these standards, other methodologies can be used, such as direct sampling of pollutants near sources (under hoods, in wind tunnels, at building openings) or passive diffusion techniques, based on the spontaneous absorption of pollutants on chemical supports, without pumps or electrical power. These allow monitoring of large areas and assessment of prolonged exposure to pollutants.
As noted, dispersion modelling is a very useful tool for assessing diffuse emissions: it allows simulation of pollutant behavior and estimation of the emission contribution of different sources. It also supports the design of corrective measures and risk assessment. Receptor and source apportionment models further allow measured concentrations to be attributed to different sources, distinguishing between industrial emissions, vehicle traffic, domestic heating, etc.
Finally, continuous monitoring makes it possible to detect real-time variations in pollutant concentrations, providing data with high temporal resolution. These technologies are very useful for identifying emission peaks and operational anomalies and for verifying the effectiveness of containment measures.
Integration with corporate management systems
An additional boost to the effectiveness of integrated control systems comes from the digitalization of monitoring processes. The adoption of remote-control technologies, continuous sensors, and data management platforms enables real-time detection of emission variations, identification of operational anomalies, and prompt intervention. These tools not only simplify environmental reporting but also foster integration between technical and managerial functions within the company, contributing to stronger, more dynamic environmental governance oriented towards continuous improvement.
PM_TEN offers advanced expertise and specialist services that perfectly integrate with the needs of monitoring and managing diffuse emissions, supporting companies both technically and regulatory-wise. PM_TEN specializes in air quality and meteorological modelling, for diagnostic studies and environmental impact assessments. These skills are fundamental for evaluating non-channelled emissions and designing containment strategies based on realistic scenarios and scientific data.
In the context of digitalization of environmental systems, we propose solutions such as DigitalPlant, a platform that enables integrated management of environmental data, continuous monitoring, and predictive analysis of emissions. This tool provides early warning and prevention mechanisms, allowing timely corrective actions and contributing concretely to regulatory compliance and continuous improvement.
Regulatory non-compliance: consequences and sanctions for companies
Proper management of diffuse emissions is an obligation under environmental authorizations and national legislation. In case of non-compliance, companies may face various administrative, economic, and criminal consequences.
In the most serious cases, suspension or revocation of authorization is envisaged, with consequent shutdown of production activities. These measures may be adopted when non-compliance poses a significant risk to the environment or public health, or in cases of repeated violation of authorization requirements.
Furthermore, under Legislative Decree 231/2001, companies may be held liable for environmental crimes committed by managers or employees in the interest or to the advantage of the company itself. Administrative liability may entail prohibitive sanctions, confiscation of assets, and severe reputational repercussions.
Inspections and control activities for companies
Inspection activities are mainly entrusted to regional ARPA agencies, which operate in coordination with the competent authorities and the Ministry of the Environment. Inspections may be scheduled, random, or triggered by reports, and cover both documentary and technical-operational aspects.
The frequency of inspections depends on the environmental risk level of the plant, its authorization history, and the presence of previous critical issues. Plants subject to AIA are generally subject to periodic checks, with the possibility of unannounced inspections.
In this context, documentary traceability and transparency in emissions reporting are particularly important. The availability of updated, consistent, and easily accessible data is a key element in demonstrating regulatory compliance and reducing sanction risks. Digital environmental management systems, such as those proposed by PM_TEN, can facilitate the collection, analysis, and sharing of information, strengthening the company’s environmental oversight.
Regulatory evolution and future trends
Future prospects outline a scenario of increasing stringency in environmental controls, with strengthened inspection activities and greater emphasis on digital compliance. The adoption of digital systems for continuous monitoring, document management, and standardization of emissions data will be crucial to ensure regulatory compliance and facilitate dialogue with competent authorities.
In this scenario, companies will need to invest in smart technologies and specialist expertise to proactively and strategically address the challenges of the ecological transition of industries.