Conditioning equipment for biogas quality

May 16, 2012 | General

How To Speak “Natural Gas”

Achieving optimal communications with local natural gas distribution and transmission pipeline companies can help bring renewable natural gas projects to successful fruition.

Diane L. Saber
BioCycle May 2012, Vol. 53, No. 5, p. 41
Conditioning equipment for biogas quality

Gas quality objectives will dictate the type of conditioning equipment (example above) for the project, which in turn influences project costs and other parameters. Photo courtesy of Greenlane Biogas

Renewable Natural Gas (RNG), otherwise known as biomethane, is a product that has many uses and applications. Project developers, municipalities, landfill owners and operators, waste collection companies, farmers, technology providers and supporting consulting companies have or are beginning projects aimed at converting a naturally-produced “waste” gas into a high demand product. Natural gas utilities are a primary market for RNG. However, the question remains, “How do I sell this valuable product to an industry which seems to speak another language?” It is not a matter of translation; it is a matter of priorities.
Maneuvering through the world of natural gas utilities can be confusing and sometimes confounding, especially when considering sale of RNG to or through its pipelines. A review of gas industry “hot buttons” may aid in ushering new projects into reality. This article is aimed at helping RNG producers “speak natural gas” to utilities, so that their projects may be streamlined with better results.

“Green Gas” Versus “Green Electrons”

The term “Renewable Natural Gas” is appropriate and accurate; a methane-containing gaseous waste derived through the natural anaerobic digestion of organic materials can be captured and upgraded to meet the gas quality specifications in the natural gas industry. All organic materials degrade, but under conditions that are devoid of oxygen, the products of breakdown include methane, carbon dioxide, sulfur and other constituents. This “raw gas” or biogas can sometimes be burned directly in smaller, on-site generators to produce electricity or “green electrons.” Partial cleanup of the biogas (sulfur and siloxane removal) may be necessary for cogeneration (co-gen) or engine operation, and off gases from the burning process may require stringent cleaning prior to release into the atmosphere (NOx, SOx and particulate matter). Biogas conversion to electricity is also inefficient, as there is waste heat produced; in North America, waste heat is often not captured for productive use.
Biogas can also be cleaned or conditioned (undesirable constituents are removed and captured) to produce a “green gas” that is highly similar to natural gas currently used today in North America. The Renewable Natural Gas may then enter the natural gas pipeline network and used productively. RNG may also be burned to produce “green electrons” as part of regular, large-scale electricity production by a utility.

LDCS Versus Transmission Companies

The drivers for RNG projects vary and sale price for RNG remains in a state of flux, as natural gas prices continue to be at record low levels. However, the price of natural gas is not the only consideration. Price and terms of sale may be influenced by the needs locally or by markets in states far away. Unless the RNG producer is able to supply a dedicated pipeline directly to a specific end user and buyer of the gas, the RNG will require transport using an existing local distribution company (LDC) system or a transmission pipeline. Generally, LDCs support a low-pressure, small diameter local distribution network which services customers directly, and the transmission pipeline grid (high volume, high pressure) carries gas great distances and feeds LDC networks throughout North America. Regardless, RNG quality and specifications are governed by conditions required at the point of injection, despite the distance the gas will ultimately travel to meet its buyer or end user.
Therefore, the RNG producer will need to engage in discussions at a local level. Some common tips for “speaking natural gas” with both the LDC and transmission companies may be helpful for all those wishing to bring their RNG projects to successful fruition.

Ten Tips For Speaking Natural Gas

1. Start Discussions Early
In project planning, remember the gas company may “hold the keys” to success and will need to be involved, unless the project plan includes complete separation from the gas grid. The receiving gas company (either LDC or transmission company) will want to be a part of the process. Gas companies are concerned for their pipeline network; they require time to evaluate aspects such as current loading, seasonal variations and demands, pipeline capacity, gas routing and other factors. Additionally, immediate end users and sensitive conditions on the line are considered. Immediate end users directly use the RNG (e.g., industries burning natural gas as a part of their process) and may have burners engineered around specific natural gas specifications. Additional constituents or variations in the Wobbe Index (measure of combustion energy output) may be a problem, and sensitive efficiency sensors can be impacted by even trace constituents of atypical constituents. Similarly, sensitive line conditions may include a series of these end users or other RNG receivers who require a gas product of defined specifications.
This outreach to the gas company may take time and internal effort between various internal departments. The expression “early and often” describes optimal communications between the RNG developer and the gas company, and it is never “too early.” Gas companies are conservative, cautious and hate surprises. Most of the time, various departments, such as marketing, gas operations, metering and engineering, who do not regularly interface will be required to come together and discuss your project. Remember, this may be the first time they have encountered an RNG project and they want successful results. A smooth project is best executed as a team effort between all parties.
2. Correct Wording
Using the correct words in discussions with the gas companies makes all the difference. The term biogas refers to a raw gas; it will never enter the network. This gas requires cleanup to biomethane or RNG for inclusion in the pipeline network. Use of correct terminology provides a level of comfort as professionals speak to each other on a common topic. Incorrect use of wording is not only confusing, but it may indicate a lack of knowledge of the industry and will slow your project.
3. Conversion Terminology
The following conversions may be of help when speaking of volumes of gas:
1 foot (cf) = 1,000 BTU (British Thermal Units)
100 cf = 100,000 BTU
1,000 cf = 1 Mcf
1,000,000 cf = 1 MMcf
1 Therm = 100,000 BTU = 1.055 x 108 joules = 29 – 30 Kilowatt (kWt) hours
1 Dekatherm = 1000 cf = 1 Mcf = 1,000,000 BTU = 1 MMBTU
.9478134 MMBTU/Gigajoule (GJ) or 1.055 GJ/MMBTU
1 Bcf (billion cf) = 1,000 MMcf
The energy in a cubic foot of gas varies slightly and therefore there is no exact value for a Therm. Natural gas has a BTU of approximately 1,000 (most slightly higher). RNG possesses a BTU of less than 1,000, due to the percent methane with the absence of hotter burning gases, such as propane, butane, etc. The BTU of RNG is approximately 960 to 980. In 2006, the US used 21,700,000,000,000 or 21.7 x 1012 cf of gas.
4. Get The Gas Specification As Soon As Possible
Because the quality of the RNG is of such importance to the natural gas network, determining the gas quality goal should be one of the project’s first benchmarks. The gas quality objectives will dictate the type of conditioning equipment for the project, which in turn influences project costs, consumables, analytical equipment necessary, personnel required and other parameters. Gas quality objectives vary between gas companies. In addition, the gas may need to be compressed (brought to a higher pressure) before it can enter the pipeline network. Chemical, physical and mechanical aspects of the project required by the gas company should be determined early in the project, in order to predict both costs and overall scope. The gas conditioning approach will need to accomplish the specified goals of cleanup and some gas specifications can be quite rigorous.
5. Natural Gas And RNG Comparisons — Analytical Perspective
The natural gas company will require that the RNG comply with requirements it sets forth. To have productive discussions, become familiar with typical natural gas parameters as well as the quality of your RNG product. Be prepared to speak about your product with knowledge; some conditioning companies will offer performance guarantees with supporting data. Understand your data, be open to discussions and try not to get defensive about your product or system. The natural gas company may simply be asking for clarification or for the purpose of education. Be aware that natural gas is regularly tested for BTU and other parameters. Welcome independent gas testing of your RNG; the gas company may require it!
6) Help Find the Win/Win
Gas utilities may not see the opportunities for RNG as readily as a developer or producer. The natural gas industry is changing rapidly and assisting the gas company with ideas for RNG promotion or marketing may be the start of new exciting ventures for all. From current customers who wish to purchase green products, to fulfilling RPS (Renewable Portfolio Standard) goals, to new growth areas, such as natural gas vehicles (NGVs), placement of RNG in the marketplace will require creative promotion and new product placement. Rather than expecting the natural gas company to immediately recognize the unique value of RNG, help to bring forth ideas and concrete solutions.
7. Be Flexible and Creative
Depending upon the LDC or transmission company, there may be numerous departments and entities involved in project approval. Every project is different and must be evaluated separately. Simply because a project was streamlined in one city or state does not guarantee similar reaction elsewhere. Try to develop interim plans for the RNG, or develop “Plan B,” until all issues are resolved. Alternatively, develop a smaller project as a demonstration, with plans for further expansion once quality/quantity or other issues have been resolved. Be mindful that the demands of the RNG project are not the #1 concern of the natural gas company — they need to be assured that the gas will be delivered safely and without incidence.
8. Try Not to be Too Passionate
Approach the natural gas industry with respect and sober thoughtfulness. Most gas company representatives will listen carefully, take notes and remember specific details which key them into understanding your ability to: 1) Get the project started and completed; 2) Understand and interface with the natural gas industry; 3) Stay reliable and consistent; and 4) Appreciate their requirements and commitment to their customers, for continuous supply of a high quality product. Be prepared to speak from a point of knowledge rather than authority and listen, more than talk.
9. Quality and Safety: Words of Importance
The words Quality and Safety are hallmarks of the natural gas industry. Gas companies are ultimately concerned with the quality of the gas because it impacts human health and the environment, the pipeline network itself and end user equipment. Understanding these parameters greatly assists in project credibility and streamlines the process for all. A “Start-Up” and “Verification Testing” regime will most likely be required. The Start-Up testing may be executed over a one month period, where on-line, real-time instrumentation will analyze and record the gas quality for specific parameters. Regular laboratory testing for parameters not monitored in real-time will be concurrent. This step is executed once the RNG producer is secure that its installed conditioning process is running optimally and quality RNG is being consistently generated. Nothing worries gas companies more than off-spec gas! Verification Testing may accompany the first few months of start-up. Don’t forget contingency plans, if the RNG plant experiences an upset. Gas will be locked out of the natural gas line and may be flared or recirculated back to the facility.
10. Confer With An Expert
Biogas to RNG is a relatively new venture in North America but experienced conditioning companies and support consultants are available. Find experts with knowledge of both the industry and options for gas cleanup. Experienced conditioning companies possess data and “hands on” knowledge of gas characteristics and cleanup. Other experts assist with the interface with the natural gas companies. Using the right experts can cut both time and costs substantially, while increasing confidence in project execution.
Diane L. Saber, Ph.D. is President of REEthink, Inc. in Kildeer, Illinois. She is a nationally recognized expert in the area of production and characterization of biomethane. Prior to starting REEthink, Dr. Saber was a Director at the Gas Technology Institute (Des Plaines, IL) and responsible for a portfolio of projects and research specific to this industry in the areas of environmental science and forensic chemistry.

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