A Unique Solution to Tail Gas Flaring for RNG Plants

By Koch Engineered Solutions | August 03, 2022

Traditional biogas flare systems such as the John Zink Hamworthy Combustion ZTOF Enclosed Flare and the ZEF Elevated (Open) Flare have long been utilized to destroy the methane and other volatile organic compounds (VOCs) in the gas that is produced by landfills and digesters. Through the combustion process, these compounds are converted into water vapor and carbon dioxide, which is better for the environment. Over the years, the biogas industry has evolved into capturing this energy for beneficial uses rather than simply flaring it off. More recently, these gas plants have started upgrading biogas to renewable natural gas (RNG).  A variety of technologies are used in RNG plants to purify biogas by removing carbon dioxide and other contaminants, resulting in RNG that meets stringent pipeline specifications. The gases removed from biogas to produce the purified RNG product gas are commonly referred to as a tail gas stream. The tail gas stream is comprised of low-heating value gases (approximately 1% to 15% methane), which are not combustible on their own, but still present the potential to harm the environment if not properly destroyed.

Sending the tail gas to a typical biogas flare system may require substantial amounts of supplemental fuel, which impacts operating costs. Therefore, it is important to minimize the overall supplemental fuel requirements. Aside from minimizing operating costs, reducing supplemental fuel consumption specifically for RNG projects can provide additional value by reducing the project’s carbon intensity score. 

A recent project utilizing a JZHC ZBRID Hybrid Thermal Oxidizer instead of a traditional biogas flare resulted in a reduction of supplemental fuel by more than 50% to destroy the tail gas. The resulting reduction in supplemental fuel requirements has saved the operator an approximate *$250,000 per year by utilizing a ZBRID over a traditional biogas flare.

These scenarios are where our clients realize the benefit of a ZBRID Hybrid Thermal Oxidizer. Designed specifically for the biogas industry, the ZBRID Hybrid Thermal Oxidizer utilizes a balanced approach to incorporating design innovations to minimize supplemental fuel while being a cost-effective alternative to traditional thermal oxidizers. This leads to substantial operational savings and reduction in capital expenditures. Specialty flare systems offer a valuable alternative to more traditional equipment, and each project application should be evaluated individually to ensure the right technology is selected.

John Zink Hamworthy Combustion, a Koch Engineered Solutions company, has been a long-standing technology provider in the biogas industry with installations dating back to the 1970s. This includes elevated and enclosed biogas flares, as well as specialty equipment including gas conditioning equipment, ultra-low emission enclosed flares, high/low pressure flares, leachate evaporators and many others.

*Site savings are estimates based on $5/MMBtu natural gas price and the plant operating continuously.


Contact: Alex Bycroft
Commercial Development Manager, RNG & Biogas Systems
[email protected]