Is it possible to achieve >97% CH4 (Methane) purity with a PSA-based Biogas Upgradation System?

That's one of the most common questions we get asked, and our answer is Yes, it is possible. Most of our latest upgradation systems are capable of achieving >97% CH4 purity considering that the Nitrogen & Oxygen levels are maintained below a certain level. Don't take our word for it, have a look at the recent picture of a German Gas analyser installed at one of our many installations.

However, the most important question that is ignored and should be asked by aspiring Compressed Biogas (CBG) plant owners is what is the CH4 Recovery achieved by the upgradation system??Before we answer this question, let’s first understand the meaning of CH4 Recovery/Loss. The CH4 recovery is the amount of CH4 that the upgradation system can capture from the incoming Raw Biogas and pass on to the product/purified gas stream rather than inevitability exhausting it along with the C02. Most single-stage upgradation systems do a terrible job at CH4 Recovery.

It is CRUCIAL to understand that the CH4 purity is only Half the battle. Most clients and owners aren't focusing on the CH4 Recovery. For example, if you have 100m3 of raw biogas with 55% CH4 content, this means that you have 55m3 of pure CH4. Now, if after the upgradation process, you get only 46m3 as product gas having 96% CH4 purity, this means you got back only 44m3 (46m3 product gas x 96% CH4) of CH4 as compared to the 55m3 of CH4 that was present in the Raw Biogas. This translates to a CH4 recovery of only 80% (44m3/55m3), or in other words this translates to a CH4 loss of 20%. A CH4 loss of 20% is HUGE. That's 20% of possible revenue that you could have made but couldn't because of the inefficient upgradation system. Imagine setting up a plant that can generate a revenue of INR. 20 Crores a year by selling CBG but is only generating Rs. 16 Crores and losing Rs. 4 Crores every year due to the ignored CH4 losses. Now multiply this yearly loss of Rs. 4 Crores over the life cycle of the plant, which is typically 15 to 20 years. To make it easier, we have posted a working example in the post to help you understand the massive revenue loss that can occur if the CH4 loss is ignored.

Based on empirical evidence shared by clients and our own experience, CH4 Loss is the most common problem that plagues most Biogas Upgradation systems, especially Single Stage Biogas Upgradation systems. Be it Membranes, Water Scrubbing, or PSA. Based on the most recent rectification contract that AtmosPower was awarded by a frustrated client, it was observed that their PSA system had a loss of more than 20%. That is 20% of possible revenue, which is getting exhausted into the atmosphere and significantly harming your bank account and the environment.

What are we doing differently at AtmosPower? (Time for a well-deserved publicity plug ??). Based on AtmosPower’s Patented 2 Stage V-PSA System, we have been able to reduce this CH4 loss to close to 1%, which is similar to what can be achieved using an expensive 3-stage membrane-based system. This wasn't an easy battle since our own initial systems had large CH4 losses. However, after setting up more than 100 Biogas Upgradation systems and building on the learnings of each installation, we have finally been successful in achieving a CH4 recovery of 99%. Is this system more expensive than conventional single-stage systems? Yes, it is. Why is it more expensive? It's got two stages/systems - you are getting one Main system and one Secondary system to capture the CH4 losses. Can the additional cost of this system be recovered within a year? Yes, it most definitely can.

Circling back, please do not ignore the forest for the trees and ask/demand your preferred Biogas Upgradation Vendor to show you the Methane recovery/losses of at least 1 of their running plants. An extremely simple method is to use a handheld gas analyser and place it at the exhaust/vent of the upgradation system. In the majority of cases, this should be a good enough test.?However, you can contact us for more sophisticated methods for measuring CH4 losses, and we will be happy to assist.

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