Renewable Gas #4 : CBG

Terminology is important, which is why I use the term “Renewable Gas” to describe all sustainable resources of gas, rather than the clutch of acronyms that are being sprayed about at engineering conferences. I chose “Renewable Gas” as it is a parallel term to Natural Gas, which is in common use, and which most people are aware comes from mining operations, often from the same wells as petroleum crude oil. And by using the word “Renewable”, it is clear that I am talking about sustainable sources.

Since this is an emerging field of energy research and development, much of the engineering language could be opaque to the average Joe Blogger, particularly since people are using different terms and acronyms to describe the same things.

Over time, the descriptive language and the acronyms and categories are becoming consolidated – one such term being CBG, which stands for Compressed Biogas. It’s derived from the rather more well-known term CNG, which stands for Compressed Natural Gas.

CNG is used as a correlate to a very well-known term, LNG, which stands for refrigerated Liquid Natural Gas, of which the UK imports rather a lot by ship, so has entered common language. CNG, by comparison, is not liquid, just very compacted gas, and is becoming a solution for urban air quality around the world, used in large public service vehicles (buses), originally, but now in a range of transport options.

However, despite the fact that fuelling by CNG helps improve air quality, it’s still derived from Natural Gas, which is a fossil fuel, and therefore finite in supply. And this is where the many sources of Renewable Gas can be useful, in prolonging the use of remaining resources of Natural Gas, by mixing with or substituting for the fossil fuel.

There are varieties of Renewable Gas, depending on the source material and the chemical process used to collect or create the gas. One of the most well-known is Biogas, which is drawn from the composting of plant and animal waste, and is divided into categories, such as Landfill Gas and Sewage Gas, and where the process can be augmented and accelerated by various Anaerobic Digestion treatments.

But besides the microbiological breakdown of formerly living tissue, which creates Biogas, it is also possible to create what are called synthesis, synthetic or substitute gases, generally from plant waste, such as forestry residue. This is being referred to as BioSNG in places, where SNG refers to Synthetic, Synthesis or Substitute Natural Gas. However, it can also just be called Syngas, and it’s up to us, the audience, to work out whether this particular syngas has been renewably sourced.

Gassy fuels will become essential in the near future, as liquid petroleum fuel products are going to come under significant supply stress due to depletion and geopolitical factors.

The key point is that, as the Marginal Abatement Cost Curve (MAC) at the top of this post shows, the drive towards using gaseous rather than liquid fuels for Heavy Goods Vehicles (and other large vehicles such as buses), will probably cost more than any carbon price or tax that can be agreed at the political level. The chart seems to suggest that a carbon price of £ 150 GBP per tonne of Carbon Dioxide will be reached.

What is not considered is that the cost of petroleum-derived fuel products could cost around $ 300 USD a barrel in the not-too-distant future. If that becomes the reality, then it won’t matter if a carbon price is set or not, CNG, CBG and mixes of these gas fuels will quite possibly become the cheapest option for the world’s trade and transportation systems.

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