How Continuous Monitoring Can Maximize the Value of Biogas and RNG Facilities

By: Jarett Henry

Case Study Key Highlights

• A large U.S.-based renewable natural gas (RNG) producer deployed Qube’s continuous monitoring devices around their covered lagoon digesters

• Real-time leak detection allowed on-site personnel to repair leaks immediately that otherwise could have gone unnoticed for long periods of time

• Data analysis of the pilot project showed that just 5% of leaks represented ~55% of the total emission volume

• Price premiums for RNG are at 15-20x above conventional gas in the U.S. (over ~$50/MMBtu) which provide a high ROI for investing in continuous monitoring

• Utilizing Qube Continuous Monitoring Technology and our software platform providing real-time alarms and estimated location, an identified leak in this pilot saved an estimated $200k in lost revenue

Challenge

Figure 1: Covered lagoon at a California dairy farm (source: MDPI)

In recent years there has been a remarkable growth in farm-based biogas and RNG production, fueled by government programs in the United States such as Low Carbon Fuel Standards (state-based) and the Renewable Fuel Standards (federal), and in Canada through the Clean Fuel Regulations. These programs create a price premium for RNG, incentivizing farmers to capture and sell the methane from animal manure that could otherwise be leaked to the atmosphere.

This price premium – 15-20x above conventional gas in the U.S. (over ~$50/MMBtu) – makes it critical for operators to ensure that leaks are minimized throughout the gas capture and upgrading process. Unfortunately, several studies have demonstrated that this isn’t the case, with a recent survey campaign finding that farm-based biogas plants average 4.8% methane leakage.

Without an effective continuous monitoring system, these leaks represent a source of lost revenue for operators. Small holes in lagoon covers or at the top of digester domes are missed by visual inspections, while intermittent surveys using manual or aerial devices report leaks long after they originated. When it comes to preventing methane from entering the atmosphere and keeping it as a revenue source, every minute counts.

Solution 

Qube worked with a large U.S.-based RNG producer to place six devices around the perimeter of each covered lagoon at a series of swine farms. Device placement was optimized by Qube’s automated software that uses historical wind data to maximize coverage area and accuracy. Each lagoon was given a digital grid overlay of 30 potential source points, allowing Qube’s proprietary model to localize the source of the detected emissions and quantify the leak rate. 

Figure 2: Qube device deployed at a covered lagoon digester

Prior to this pilot, operators were spending significant amounts of time conducting manual visual inspections of each lagoon cover. Qube’s dashboard allowed for leak alarm notifications to be automatically sent once a trigger threshold was met. This simultaneously improved response time to identify and repair leaks and reduced the time spent on manual surveys. These alarm notifications also contain the calculated geo-location of the leak, saving additional time for personnel sent to investigate and repair. An additional benefit to this localization is the discovery of leaks from the “usual suspects” of tears in the cover. Qube devices have been instrumental in finding leaks from seals around the edge of the cover, piping, and other unexpected sources.

Figure 3: Qube dashboard showing suspected leak locations and wind roses for the selected time period

Results

A small number of leaks generate the majority of total emissions

This pilot showed that leaks do not occur at consistent intervals or emission rates. In fact, just 5% of the detected leaks represented ~55% of the total emissions over nine months of data collection. This distribution is similar to the oil and gas sector, where research has found that the top 5-10% of leaks represent 60-80% of emissions. Promptly detecting these leaks with intermittent surveys would have required very lucky timing!

Immediate leak detection can save operators from significant revenue losses

In addition to the environmental impact, large leaks represent substantial losses of potential revenue if they aren’t detected and repaired quickly. This pilot demonstrated many relevant examples of this in action, including the following incident from August. Qube devices detected a significant leak at around midnight, and automatically sent a leak alarm notification with the estimated location and emission rate through the dashboard. Operators used this information to locate and repair a three-inch tear in the lagoon cover the very next day. Based on the quantified emission rates, this leak would have represented over $200k in lost revenue if it had gone undetected for only a week!

Figure 4: Qube dashboard showing location of large leak and simulated plume visualization