[Brad]

The answer is simple – replace (or supplement) your activated carbon vessels with a regenerative system. A technology that is massively underutilized in the RNG space is the regenerative siloxane and VOC reduction system. The media is regenerated automatically, often lasting for years without replacement. For any waste water or landfill gas project, the return on investment is incredible. It has a higher CapEx than vessel(s) of carbon, but a far, far lower OpEx providing rapid ROI.

In terms of providers, there is only one worth considering – the engineers at Willexa Energy invented this technology and have never missed a performance guarantee. It’s worth checking them out at http://www.WillexaEnergy.com.

willexaenergy.com

Siloxane & VOC Reduction for Biogas & RNG by Willexa Energy

Siloxane & VOC reduction for landfill & digester biogas to energy or renewable natural gas (RNG). Guaranteed, reliable and cost effective biogas treatment by Willexa Energy.

[Peter]

Thanks @RNGinsight , What is the minimum flow and concentration where these regenerative VOC and siloxane removal systems are cost effective? How do they respond to high turpine concentrations?

[Brad]

Long term, lower OpEx will always eventually pay for higher CapEx, but you are correct, in small flow applications with relatively clean gas, it may take a while. I’d say any landfill, and most WWTPs would be a fit for a regenerative system with payback measured in months to 1 – 2 years. Ag projects generally have little or no siloxanes, so the benefit is limited to VOCs only.

[Peter]

As @RNGinsight says regenerative systems are the lowest operating cost long term when you are treating very contaminated gas. In some cases the biogas flows on smaller agricultural projects will never justify the upfront cost of a regenerative system. In lower flow cases carbon costs can be managed by using carbon for siloxane, turpine, and voc removal only with iron based media beds and in situ iron treatment used for sulfur removal. We give some rules of thumb for when to consider a regenerative system for sulfur removal in this article: https://azuraassociates.com/three-risks-of-h2s-at-rng-plants/

azuraassociates.com

Three Unexpected Risks of Hydrogen Sulfide at RNG Plants – AZURA

Three Unexpected Risks of Hydrogen Sulfide at RNG Plants – AZURA

[Justin]

Another strategy would be to treat hydrogen sulfide production inside the digester, significantly reducing the load that the carbon is exposed to and responsible for, making it last significantly longer.

At PlanET we use a combination of micro-aeration (O2 injection into the digester), eco-net for sulfur accumulation and precipitation, and dosing with iron oxyhydroxide.
The dosing can be accomplished several ways, including with our own PlanET SmartDose systems. The SmartDose mixes the iron powder into solution and injects it directly into the digester for maximum reactivity.

They are available in different sizes and configurations to fit your plants, so reach out if you’d like to learn more.