October 2020 - Technical Article

Top 6 Benefits of Using DMT Membrane Systems for RNG Projects

Carborex® MS: Technology of Choice for Biogas Upgrading Facilities

Author: Graham Hartlett

Industries: WWTP, SSO, Landfill, Agriculture/Dairy, Industry, Oil/Gas

Keywords: Carborex® MS, membranes, membrane systems, membrane technology, renewable natural gas, RNG, biogas upgrading


DMT Clear Gas Solutions is one of North America’s leading biogas upgrading technology providers for renewable natural gas (RNG) projects. Based in Portland, Oregon, DMT offers a wide range of biogas conditioning systems applicable in various industries. These industries include dairy, wastewater treatment, landfill, and source separated organics, among others. With over 30 years of worldwide experience, DMT focuses their engineering efforts exclusively on membrane systems for CO2 removal. But why this acute focus on only membrane systems for biogas upgrading?

The top 6 benefits of using DMT membrane systems for RNG projects are as follows:

1.   Operational Ease

Firstly, DMT’s membrane systems, the Carborex® MS (membrane separation), are extremely straightforward. They are engineered with operational ease in mind. This is ideal for operators who do not want to be burdened by a complex system. A complex system with consumables and waste streams will increase valuable time and effort.

What operators want is a system that is intuitive as well as easy to operate and maintain. DMT’s membrane systems provide exactly this. The integrated Programmable Logic Controller with touchscreen Human Machine Interface provides plant operators full control. Everything they need to know to optimize performance is at their fingertips. Additionally, because the feed gas compressor is the only piece of rotating equipment integrated into the system, this benefits operators by limiting the extent of mechanical servicing and maintenance. In contrast, this is not the case for other biogas upgrading technologies.

2.  Reliability: Uptime & Grid Specification

Reliability is a crucial element when comparing biogas upgrading technologies. It’s fundamentally going to impact your ability to consistently generate revenue from the sale of RNG. The uptime performance of DMT’s Carborex® MS makes this system incredibly reliable.

DMT offers bona fide performance guarantees stating uptimes of 95% and above. The company is confident in their technology and engineering. While most technologies can accommodate the injection grid specification, the Carborex® MS was designed to meet grid specifications consistently and reliably. And yes, part of the reason for these incredible uptime statistics is because the Carborex® MS is so straightforward. The potential for unexpected downtime is limited as such.

3. Membrane System Flexibility

It is guaranteed that factors will change while onsite. Flexibility is key and DMT’s Carborex® MS is the most flexible biogas upgrading plant available. With the likely possibility of fluctuations in the quality of the feedstock that enters anaerobic digesters, gas constituents will also vary. DMT’s membranes, in addition to removing CO2, will remove moisture, residual H2S and 50% of O2 entrapped in the gas.

Additionally, biogas flow rates will change over time due to feedstock variations and digester management and operations. The Carborex® MS has an unmatched turndown ratio of up to 30% in the design flow. What this means is that DMT’s engineers have designed the Carborex® MS to accommodate biogas flow rates of 30% of their design flow rate. The RNG produced will still be according to the required grid injection specification.

DMT's membrane system, the Carborex MS, in Leeuwarden, the Netherlands with 2 service team members walking by.
The Carborex® MS offers operational ease, reliability, flexibility, durability, a small footprint and cost savings.

4.  Membrane Lifetimes

Through effective pre-treatment of the raw biogas, in combination with DMT selecting the best available membranes, DMT offers an unmatched membrane life of 10 years or more. After the biogas goes through compression in the feed gas compressor, it passes through a series of filters designed to remove any impurities that may limit the performance of the membrane system. The cleaner the feed gas, the better the membranes will perform and the longer they will last.

5.  Membrane Systems: Small Footprint

It is always important to utilize available space effectively. Dairy farmers, for example, place a huge emphasis on land utilization since wastage amounts to the opportunity cost of using the same land area for another revenue-generating purpose. Many of DMT’s industrial clients also have very limited space to insert a biogas plant. Thus, through its design, the Carborex® MS has a footprint better than most competing technologies.

6.  RNG Project Cost Savings

Lastly, DMT’s Carborex® MS performs extremely well when comparing OPEX and CAPEX savings to other biogas upgrading technologies. Initial capital outlay is lower and operational costs are either on par with water systems or outperform other technologies. With main power consumers being the compressor and chiller, power costs are lower compared to liquefaction systems, and generally on par with both water wash and PSA systems. There are also no significant waste streams to consider during the cost analysis as one would include for technologies requiring chemicals and absorbents.

DMT has always been an advocate of providing clients with what they consider to be the best upgrading technology available in the market. In their view, membranes provide the most compelling value proposition. If in time a better technology were to exist, DMT would presumably switch again. However, with more and more project developers selecting membrane systems as their technology of choice for biogas upgrading, it’s clear why DMT’s membrane systems continue to be a compelling value proposition for RNG projects.