Benzene: Emissions Reduction Continues Apace

Discovered in 1825, benzene has become a highly versatile chemical, used for example as a raw material for the production of plastics, resins, lubricants and dyes. However, due care is needed when handling benzene as exposure can cause, amongst others, neurological effects, anemia, and cancer. Strict regulations are therefore followed and where necessary enforced in many geographies to reduce benzene emissions from refinery waste, as evidenced by recent desk research.

By KCI Editorial

The starting point for anyone looking to understand benzene waste control in the hydrocarbon industry in the US has to be the EPA website. This resource gives the background on a page entitled: Benzene Waste Operations: National Emission Standards for Hazardous Air Pollutants (BWON for short).¹

Other resources that provide an historical context include the U.S. Government Accountability Office website, with a text dated December 1985 on EPA’s Strategy to Control Emissions of Benzene and Gasoline Vapor.² Interestingly, this document notes that ‘benzene has been recognized since 1900 as a toxic substance capable of causing short-term and long-term effects on the blood-forming system.’

For a more succinct understanding of BWON, an article presented on the TEADIT website is most useful.³ For example: ‘The Benzene Waste Operations NESHAPs (National Emission Standards for Hazardous Air Pollutants), was promulgated in 1990 under the Clean Air Act (40 Code of Federal Regulations (CFR) Part 61, Subpart FF). The BWON standard was put in place to control benzene emissions from facility waste; it applies to petroleum refineries, chemical plants, coke by-product recovery facilities, and treatment, storage, and disposal facilities (TSDFs). TSDFs must only comply with this standard if they handle waste from one of the other facilities listed. BWON is a unique standard as it combines waste and wastewater quality management in an air standard for controlling benzene emissions.’

The TEADIT article further notes that BWON includes multiple subsections such as applicability, waste & waste stream determination, compliance operations, point of waste generation, and treatment & equipment standards.

Fenceline Monitoring

In September 2025, EPA posted an Enforcement Alert after identifying compliance concerns under the Clean Air Act’s benzene fenceline monitoring regulations at petroleum refineries.⁴ The Alert states that: ‘The regulations require root cause analysis reports and corrective actions anytime the annual average benzene concentrations recorded by a refinery’s fenceline monitors are greater than the regulatory action level.’ Giving context, EPA outlines issues such as the fenceline monitoring requirements, site specific monitoring plans, corrective action plan, and concludes with a case example.

Note that the EPA has created an online benzene fenceline monitoring dashboard which is freely accessible.⁵ EPA states: ‘Refineries began reporting monitoring data to EPA in May 2019 and continue to report on a quarterly basis. Although EPA has made this data publicly available via WebFIRE, this Dashboard is meant to make the data easier to access and analyze by EPA, state and other regulatory agencies, and members of the public’.

The complexities of fenceline monitoring are set out in an online article by Trinity Consultants.⁶ For example, referring to on-site meteorological monitoring services, the article states: ‘Typically these measurements are collected on a tripod-based system; however, when appropriate Trinity also installs meteorological towers from tripod two meters to 100 meters in height to collect multi-level measurements of horizontal and vertical wind direction and speed, temperature, delta-temperature, relative humidity, barometric pressure, solar radiation, net radiation, and precipitation. Meteorological towers can be completely powered with solar panels allowing for operation in remote locations without the logistics and costs associated with power drops.’

Identifying Unknown Benzene Discharges

Further searching on the Trinity website unearthed a very interesting case study.⁷ In a nutshell, Trinity was tasked with determining why a refinery’s TAB figures (total annual benzene) showed a discrepancy when compared to end-of-line sampling. The company reviewed existing waste stream characterization data, evaluated oil-water separator water and oil concentrations and flow rates, examined wastewater management equipment and procedures during field tours, and interviewed people working in operations, management, and maintenance roles.

During this process, the team was able to improve the characterization of specific waste streams and identify a previously unknown waste stream. In addition, the team was able to recommend process improvements that would reduce the amount of benzene being sent to the sewer system.

Global Attention

Elsewhere, the Copernicus Atmosphere Monitoring Service (CAMS – part of Copernicus, the Earth-Observation component of the EU Space Programme) delivers reliable, quality-controlled and freely available information on air pollution at the global and European scales, among other data.⁸ Every year, it publishes a report on Air Quality in Europe, a comprehensive look at the state of the air across the continent in the previous year.

One of the most valuable products of CAMS is its daily air quality forecasting, which provides five-day global forecasts and four-day European forecasts for the distribution of atmospheric pollutants. Particularly useful for weather centers and air quality agencies, these predictions can be used for health protection.

More specifically, the global forecasts track atmospheric pollutants (including gases and PM), greenhouse gases, and stratospheric ozone, among other things. “We base these on a version of the ECMWF weather forecast model, which combines the best available estimates of emissions and their chemical interactions in the atmosphere with satellite observations of the key atmospheric constituents,” explains Mark Parrington, CAMS Senior Scientist at ECMWF.

The European forecasts go a step further, focusing on the EU- and WHO-regulated pollutants, other air quality pollutants, pollens and aerosol tracers. “The European forecast works slightly differently,” says Parrington. “Boundary conditions are taken from the global forecast to account for worldwide impacts, and used by eleven independent, state-of-the-art European air quality models. We merge the results and take the median value, which gives us both the prediction and an indication of the uncertainty.”

EPA in Action

In September 2024, EPA posted details of a settlement agreement summary with a refinery on its website. The settlement set out to ‘resolve alleged Clean Air Act violations for excess emissions from wastewater of benzene and other volatile organic compounds from the refinery’.⁹

The complaint alleges that the refinery violated the Clean Air Act, including the National Emission Standards for Hazardous Air Pollutants (NESHAP) for Benzene Waste Operations (BWON). Details of the consent decree included a penalty of USD$19 million. The company would also implement various capital projects to reduce benzene, VOC, and other HAP emissions at an estimated cost of USD$150 million. For example: install a flash column  and either an oil/solids removal unit or a second flash column to reduce benzene in wastewater, upgrade the collection lift station, replace emergency vents to reduce emissions on two units and replace pressure-vacuum vents to reduce emissions on other units.

As regards BWON and QQQ Compliance, the refinery was required to: comply with the EPA-preferred “6 BQ” (6 Mg) compliance option of BWON, develop a program document that specifies the regulatory requirements applicable to each piece of covered equipment, annually review process information to ensure all new waste streams are included and managed in a waste stream inventory, complete an NDE engineering assessment for each piece of waste management equipment subject to an NDE standard, install and use low-emission components or leak-free design components, conduct a root-cause analysis and corrective action when detectable emissions above the NDE standard have occurred twice at the same location and update engineering documents accordingly, conduct BWON and QQQ third-party audits every two years.

The consent decree also called for more frequent monitoring, quarterly ‘end-of-line’ sampling, and the installation of additional air monitors for benzene, toluene, and xylene inside and outside the fenceline.

When fully implemented, the agreement is expected to result in the reduction of approximately 219 tons per year (tpy) of VOC emissions, over 16 tpy of HAP emissions (non-benzene), and over 4 tpy of benzene emissions.

Supplier Offerings

In terms of practicalities, it seems that process facilities looking to reduce benzene emissions have several options. These include process optimization and pretreatment, removing benzene from wastewater, and capturing benzene vapor.

Some technology providers have interesting case studies on their websites. ChemTreat for example discusses the challenge facing a natural gas liquids fractionation facility in the Gulf Coast.¹⁰ To clear out their filter pots, pre-filters, and coalescers of benzene, toluene, ethylbenzene, and xylene (BTEX) and hydrogen sulfide prior to discharging process wash water to effluent, the facility opted for a solution using frac tanks and bio-solvent. However, this process required large volumes of treatment chemicals, significant downtime, and did not sufficiently eliminate BTEX to meet their regulatory requirements. The solution delivered by ChemTreat – based on an oxidation process – significantly restricted chemical usage, saw a three-day reduction in downtime, and eliminated BTEX waste from process wash water in line with environmental goals.

Online information about materials suitability for O-rings and seals intended for benzene applications seems limited. One supplier that does present a chemical compatibility guide is Marco Rubber & Plastics.¹¹ For example, the company rates the compatibility of perfluoroelastomer (FFKM) and Viton® Extreme (ETP) as ’excellent’, whilst at the other end of the spectrum, Nitrile (NBR), ethylene propylene (EPDM) and silicone (SIL) are ’not recommended’.