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Measuring Emissions from Heavy Oil Storage Tanks

Two EETD scientists, Donald Lucas and David Littlejohn, have developed a method to measure air pollution emissions from heavy oil storage tanks. The method measures hydrocarbon emissions using a simple oil-sampling device fashioned from parts available at hardware stores for less than $20 (see Figure). Older measurement methods that were developed for lighter oils overestimated emissions from heavy oil tanks by orders of magnitude.

The researchers were approached by the Heavy Oil Storage Tank (HOST) Committee, which represents three air quality districts in Southern California, the U. S. Environmental Protection Agency (EPA), the California Air Resources Board, as well as members from the industry that these agencies regulate: oil companies and the Western States Petroleum Association. HOST was seeking new, accurate methods to inexpensively measure emissions from heavy oil storage tanks. By working with industry, they hoped to develop a consensus method for measuring these emissions.

Oil-sampling device developed for heavy oil tank emissions test.

Figure. Oil-sampling device developed for heavy oil tank emissions test.

Inexpensive Components

The new technology consists of a simple sampler built from off-the-shelf parts and used with the Tank Atmosphere Perturbation method, which measures the total gas emissions (reactive organic compounds, carbon dioxide, water vapor, methane) from a tank. The method involves blowing air into a tank headspace to perturb the concentrations of gases there and then taking measurements as the concentrations return to their equilibrium state. The samples are collected and then analyzed in the lab.

Thousands of oil storage tanks dot the landscape of oil-rich counties in southern and central California. Typically 30 feet high and 40 to 50 feet across, they store the crude oil extracted by pumps scattered across numerous oil fields, which can be as small as a few acres. HOST approached EETD seeking an inexpensive, reliable, and accurate method of measuring the emissions from these storage tanks to address the various concerns of its members. The region's air quality districts needed a way of determining the magnitude of the contribution that these tanks made to air pollution problems in the region, particularly the Central Valley, which has one of the worst air pollution problems in the nation today, including high levels of ozone and particulates. The oil industry stood to lose tens of millions of dollars mitigating a problem whose magnitude was unknown because the standard Reid Vapor Pressure (RVP) method, which is well-suited for liquids like gasoline, does not work at all for heavy crude oil. For example, one of the steps in the RVP method calls for cooling the liquid in an ice bath and transferring it to the analysis system. Existing tests fail because crude oil thickens like peanut butter once cooled.

The Berkeley Lab researchers went into the field to study oil tanks made available to them by HOST members and developed the test method. HOST issued no mandates in how to proceed; the Lab team took a leadership role in conducting the research, and meetings were run by a mediator who ensured that all parties reached consensus as the work progressed.

Transferring the Technology

After developing the oil sampler and measurement method, Lucas and Littlejohn made numerous measurements of tanks operated by HOST members. Their measurements demonstrated to regulators that the approach yielded accurate results. Oil industry members were satisfied that the new technology was accurate, inexpensive, and could be used reliably by the private firms that provide measurement services. The Lab team worked with all local and state regulators to gain official approval from local air districts, the California Air Resources Board, and the U.S. EPA for the testing methods. Then they taught commercial vendors, selected by HOST, to use the test method and technology; Aeros Environmental, Zalco Laboratories, Oilfield Environmental & Compliance, and Genesis Environmental Services participated.

One result of this work was that continued measurements demonstrated that oil tanks emission levels were much lower than expected. This helped both regulators, who, once they knew that the problem was not as large as they had feared, could free up resources to address other, larger pollution sources in their districts. The Industry also benefited by avoiding expenditures of tens of millions of dollars that would have been required to alter the tanks if they had been found to be a significant source of pollution.

— Allan Chen

For more information, contact:

  • Don Lucas
  • (510) 486-7002

This work was funded by the Department of Energy and the Western States Petroleum Association.

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