Opinion: Making the most of the RHI reforms with membrane technology

Upgrading biogas to biomethane, for injection into the gas grid or for use as a vehicle fuel, is one of the most efficient uses of biogas. There are several upgrading methods available and in 2012, a new solution came onto the market: highly selective membrane technology.

However, the progress of biomethane in the UK has been halted due to uncertainty over the incentive regime. Having originally been proposed by BEIS back in December 2016, reforms to the Renewable Heat Incentive (RHI) were delayed due to the General Election and Brexit, leaving the industry in a state of uncertainty for almost 18 months. These reforms were finally passed on 22 May 2018, providing additional financial support and certainty for developers by resetting RHI tariff rates to June 2016 levels and offering tariff guarantees. Industry insiders are predicting another surge in plant construction, following the first wave of activity that saw 90 UK biomethane facilities built in just five years.

Upgrading options

Whereas biogas is only suitable for heat and electricity generation, once it is upgraded it can also be injected into the gas grid and used for the same purposes as natural gas. The upgrading process removes CO₂ and any contaminants, thereby increasing the methane content. This upgraded biogas is called biomethane.

The main upgrading solutions are:

• Water wash technology, which uses high pressure water to ’scrub’ impurities from raw biogas;
• Chemical wash, which uses absorber liquids such as glycol ethers or amines to remove the contaminants;
• Pressure swing adsorption (PSA), which uses adsorbent beds to remove impurities;
• Cryogenic upgrading, which involves compressing, cooling and then expanding the biogas until the CO₂ is condensed and can then be removed as a liquid;
• And membrane technology, which uses gas permeation to separate CO₂, O₂ and H₂ from CH₄ and N₂.

Make it membrane

All of these solutions are in use at biomethane facilities around the country, but in recent years, membrane technology has become the preferred upgrading solution for the majority of UK biomethane plants, largely due to its small footprint, low methane slip, minimal maintenance requirements and superior gas production.

Thanks in part to the RHI reforms, DMT sees a robust future for the UK biomethane sector and an increase in the use of modern membrane systems, such as the Carborex MS from DMT, which offer users a high quality, environmentally-friendly and flexible upgrading experience. Compact, efficient and simple to use, membrane upgrading technology is perfectly placed to take the UK towards a green gas revolution.

This article was written by Stephen McCulloch, UK Business Director, DMT Environmental Technology. Visit: www.dmt-et.com