Optimising H₂S removal and reducing TCO with DESOTEC’s carbon grade for biogas

1. Switching from a standard impregnated carbon grade to DESOTEC’s PF5 impregnated carbon increased the H₂S adsorption drastically, leading to significant cost cutting.
2. It also captures more volatile organic compounds (VOCs), extending the lifespan of any downstream VOC filters.
3. DESOTEC’s full-service solution reduces the total cost of ownership (TCO) and saves customer’s hassle: we provide ongoing support to optimise filtration set-ups; and we take care of all filtration waste, including paperwork, logistics, and the treatment and recycling of carbon – even with a high sulphur load.
4.  As the new product from our PF5 facility is more efficient, Europe-made from renewable sources, and recyclable, it has a much lower carbon footprint than virgin carbon from non-renewable sources often coming from Asia. 

This multinational waste management company produces biogas for co-generation at its landfill site in France. To protect the combined heat and power (CHP) engines downstream, the biogas must be purified of H₂S and VOCs, especially siloxanes.

DESOTEC has been providing this client with effective filtration services for several years. Originally, we used one filter filled with a regular impregnated carbon grade to adsorb H₂S, followed by a second filter filled with non-impregnated carbon to capture VOCs.

Once saturated, these filters would be exchanged for new ones, and we would transport the old filters away from the customer’s site for safe carbon waste handling. The carbon laden with VOCs was reactivated in our furnaces for reuse, but the technology did not exist to reactivate the H₂S-laden carbon, so it was sent for safe third-party disposal - until DESOTEC developped its PF5 facility. 

With the development of our innovative carbon production facility for the biogas sector, PF5, we were eager to offer this client an even more efficient, sustainable, and cost-effective solution. We recommended the company switch to our new PF5 carbon grade - produced locally in Europe, and achieving same quality as virgin carbon.

The solution has quickly proved to be even more effective than DESOTEC had forecast. Following the switch of carbon grades, from a standard impregnated carbon grade to our PF5 impregnated carbon, the H₂S loading capacity rose from round 30% on average to 60% and above – as shown on the graph below.

Filter lifespan has been extended dramatically: previously, the customer had required five filter exchanges per year, but this has now been reduced to three, cutting costs considerably. 

Outlet measurements show that H₂S concentrations are reduced from 5500 ppm to zero or just a few ppm, while siloxanes are consistently below detectable levels.

Like many biogas producers, this client also had a small fixed filter in place as a backup, which is now rarely needed – further reducing running costs. 

On our advice, the client will shortly optimise the system by installing a second AIRCON HC-XL filter in series, filled with the same PF5 product. By doubling the carbon filter beds, this set-up will achieve even higher loading capacities for both H₂S and VOCs, further extending the filter lifespan and reducing costs and hassle.

The client is delighted with the outcome, and the site manager is now considering replicating this filtration set-up at nine further biogas facilities under his management. 

To further close the loop, not only is the carbon reactivated and recycled in our PF5 plant, but the recovered sulphur is also used to create gypsum. This is then sold to the construction sector as a building material, lowering DESOTEC’s carbon footprint and making this entire recycling process fully circular.