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19 August 2015

Reevaluating hydrogen sulfide control equipment helps landfill owners realize substantial long term cost savings

Beebe_MattNot long ago I was involved in a project at a landfill in New Jersey where a client was looking for ways to reduce the cost of treating landfill gas (LFG). The team conducted an evaluation of the changing parameters associated with the LFG and was able to generate substantial cost savings. I thought readers might be interested in the path we took to get there.

Spoiler alert: After reviewing the available technologies in the marketplace, the client opted for MV Technologies H2SPlus™ equipment, which has been successfully working for nearly two years. They have just performed their first media change-out. With the lowest O&M costs, this option has a net present value (NPV) less than half that of their prior system. Those are savings to shout about!

Setting the scene

The landfill in question opened in 1990. The 45-acre landfill is on a 300-acre site, containing an energy plant, an LFG control system, and a leachate treatment plant with storage lagoons. The landfill takes in MSW, C&D debris, industrial waste and ash. Ash is currently used an alternative daily cover (ADC), however the landfill had previously used C&D screening for this purpose. The use of C&D screening resulted in the generation of hydrogen sulfide gas (H2S).

Removal of H2S from the LFG is required to meet the terms of the client’s contract agreement with the energy developer and New Jersey Department of Environmental Protection (NJDEP). The developer was required to keep H2S at <500 parts per million (ppm). The site air permit required a 98 percent reduction in H2S. To meet the requirements, the site installed a Merichem LO CAT® sulfur scrubbing system in 2006, which was designed to process 2,200 standard cubic feet per minute (scfm) of LFG at concentrations of 11,400 ppm H2S.

In fact, our evaluation showed that the landfill is recovering approximately 700-1,000 scfm of LFG, containing approximately 1,000 ppm H2S, meaning the existing treatment system was over-designed. The over-design with respect to both flow and H2S concentration made the existing system less efficient at H2S removal and encouraged the client to look around for a more cost-effective treatment option.

What is out there?

Several technologies are available to remove H2S from LFG. Technologies can basically be classified into solid scavenger systems and liquid reduction-oxidation (liquid-redox) systems. In general solid scavenger systems are most cost effective for applications producing less than 150 pounds (lbs) of H2S per day, whereas liquid redox systems are most cost effective for applications producing more than 150 lbs of H2S per day.

Each type has advantages and disadvantages and the analysis looked at such factors as operator involvement, installation costs, and ease/cost of media change out. Also considered were media disposal issues and system efficiency.

Evaluating the best option

We asked for quotes for a system capable of processing 800 to 1,000 scfm of LFG, with H2S concentrations ranging from 500 ppm to 1,000 ppm, and achieving 98 percent H2S removal efficiency. The quotes included initial capital cost and projected operating and maintenance (O&M) costs. We got quotes for the MV Technologies H2SPlus system and the SulfaTreat system, which are both solid scavenger systems. The costs were then compared to those of the existing liquid-redox LO CAT system (with one absorber operating).

Here’s what we found. Both solid scavenger systems are generally passive, requiring minimal operator attention. While initial capital costs of the two solid scavenger systems are similar, MV Technologies H2SPlus System has a much lower O&M cost due to a lower media cost ($0.89 versus $5.50 per pound of H2S removed). By comparison, total current O&M costs for the existing LO CAT system are approximately $3.50 to $4.00 per pound of H2S removed. The net present value of total costs for the systems evaluated were

  • Existing System (Merichem LO CAT) – $2,285,262
  • MV Technologies H2SPlus – $1,000,180
  • SulfaTreat – $3,274,536

The new system is in the foreground and the old system is pictured in the background

The new system is in the foreground and the old system is pictured in the background

In addition, the site’s existing air permit required the previous system to reduce the H2S concentration by 98 percent, regardless of what the initial concentration was. We were able to work with NJDEP to modify the landfill’s new air permit to a fixed value of 120 ppm for the outlet concentration. In other words, the new permit would allow the system to be bypassed if the inlet concentration fell below 120 ppm or allow for a lower reduction in concentration on a percent basis (i.e., if the inlet was at 150 ppm it only needs to be reduced 20 percent to reach the permitted value, as opposed to the 98 percent reduction that would require treatment to 3 ppm).

By evaluating changing parameters associated with the landfill gas generated, the landfill’s owners were able to realize substantial savings.

Do you have any ideas for reducing costs associated with LFG?

Matt Beebe has 11 years of experience in the solid waste industry, including design and permitting for solid waste facilities, landfill gas system design, and construction quality assurance.

Categories: Air Quality, Alternative Energy, Biogas and Landfill Gas, Environmental Planning & Compliance, Solid Waste
Posted By Matt Beebe at 11:30 AM  |  No Comments on Reevaluating hydrogen sulfide control equipment helps landfill owners realize substantial long term cost savings

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