Natural gas vehicles are no longer a niche curiosity. With a global fleet already approaching 9.2 million cars, trucks and buses, and projections suggesting this could reach 50 million by 2020 and up to 200 million by 2030, the demand for gaseous fuels is growing fast. A meaningful slice of that demand — an estimated 10% — is expected to be met not by fossil natural gas, but by Compressed Bio-Methane (CBM): a renewable fuel derived from biogas and landfill gas.
CBM technology is mature, proven, and already deployed at scale around the world. This article explains what CBM is, how it’s produced, and why it represents one of the few waste-to-energy pathways that can be commercially viable without government subsidy.
What Is Compressed Bio-Methane?
CBM is methane recovered from biogas — the gas produced when organic material decomposes in the absence of oxygen — that has been cleaned of impurities and compressed (typically to around 200 atmospheres) so it can be used as a vehicle fuel, just like compressed natural gas (CNG).
The biogas feedstock can come from a wide range of sources, including:
- Landfill gas
- Anaerobic digestion of municipal solid waste (MSW)
- Manures and agricultural waste
- Tapioca mill effluent
- Palm oil mill effluent (POME)
- Brewery waste and human sewage
Key figure: The bio-methane share of the global NGV fuel market alone could represent 20,000–40,000 million litres of diesel-equivalent fuel per year by 2030.
Where Does the Biogas Come From?
Biogas is generated by anaerobic bacteria breaking down organic substrates — a process that is disrupted if oxygen is introduced. Suitable feedstocks are abundant in both industrial and municipal waste streams.
Municipal Solid Waste (MSW)
In Europe, MSW typically contains 40–50% organic material by wet weight. In Southeast Asia, that figure can rise to as much as 80–85%, making MSW an especially rich feedstock in the region.
Industrial and Agricultural Sources
Palm oil mill effluent, tapioca mill effluent, brewery waste, animal manures and other agricultural residues are all viable substrates. The correct digester technology — CSTRs, UASBs, dry fermenters, or in-ground reactors — depends on factors such as moisture content, solubility, ambient temperature and available land.
Landfill Gas
For landfill sites, the landfill itself acts as the digester, removing one entire stage from the production chain. However, this convenience comes with a trade-off: landfill gas is far more variable and complex to clean up than digester biogas.
Gas Clean-Up: From Raw Biogas to Pipeline-Ready Methane
Before biogas can be compressed and used as fuel, it must be stripped of impurities, moisture and particulates.
Biogas from a controlled anaerobic digester is relatively consistent in composition:
| Component | Typical Content |
|---|---|
| Methane | 60% – 70% |
| Carbon dioxide | 30% – 40% |
| Hydrogen sulphide | 0% – 3% |
Landfill gas, by contrast, is far less predictable. It can contain variable oxygen levels, elevated nitrogen (which reduces calorific value), siloxanes, and a range of corrosive volatile organic carbons. Some of these — particularly nitrogen and oxygen — may require cryogenic separation, while other applications may use Pressure Swing Adsorption (PSA), depending on the feed-gas composition.
Siloxanes are “particularly difficult to address” in landfill gas clean-up, and are one of the main reasons landfill gas processing is significantly more complex than biogas from a purpose-built digester.
Typical Process Parameters
To illustrate the scale of a CBM operation, the table below shows operational parameters based on 1,000 Nm³/hr of biogas from an anaerobic digester:
| Parameter | Value |
|---|---|
| Methane content | 60% |
| Carbon dioxide content | 40% |
| Methane mass flow rate | 10.3 tonnes/day |
| Carbon dioxide flow rate | 18.6 tonnes/day |
| Methane energy content | 6.0 MW thermal |
| Diesel equivalence | 13,400 litres/day |
| Process efficiency | 87% |
That’s a substantial diesel offset from a single, modest-sized digester — and it comes with a valuable by-product stream too.
Handling Mixed Municipal Waste
Real-world MSW arrives mixed with non-biodegradable material, which must either be removed upstream or passed through the digester. Two common approaches exist:
- Front-end separation — recovering recyclables before digestion, reducing the risk of digester blockages and capturing additional material value.
- Dry-cell fermentation — accepting waste directly into the digester, minimising delays at the point of receipt and allowing the biodegradable fraction to stabilise before later separation.
The right choice depends on a full waste-characterisation study. It’s also worth noting that an MSW-fed system will always produce a reject stream of material that can’t be digested or recycled — so this route isn’t a zero-waste solution. The digestate itself, however, has genuine value as a fertiliser and soil conditioner.
Why CBM Stands Out Among Waste-to-Energy Options
Compared with gasification, pyrolysis, and electricity generation — many of which depend on subsidised feed-in tariffs to remain viable — CBM production can compete directly against pump prices for diesel and petrol, based on global energy pricing rather than government support.
This is especially compelling where a captive vehicle fleet already operates near the production site — waste collection trucks, taxis, or delivery vehicles — allowing CBM to directly displace diesel purchases and deliver short payback periods.
Advantages at a Glance
- Converts biomass into commercially viable transport fuel
- Works with almost any biodegradable feedstock
- Can be sited close to the waste source, cutting transport costs
- Produces a marketable CO₂ by-product alongside the fuel
- Compatible with both biogas and landfill gas sources
- Offers flexible gas separation options (cryogenic or PSA)
- Supports both compressed and liquefied end-product formats
- Output is interchangeable with existing CNG distribution infrastructure
A typical CBM installation takes six to twelve months to build and commission, and relies entirely on proven engineering — there is no technology risk to underwrite.
Summary: Key Takeaways
- CBM converts biogas or landfill gas into a clean, compressed vehicle fuel, typically compressed to around 200 atmospheres.
- Feedstocks range from municipal solid waste and sewage to agricultural and industrial effluents such as POME and tapioca mill waste.
- Biogas from a digester is relatively consistent (60–70% methane), while landfill gas requires more complex clean-up due to variable nitrogen, oxygen, siloxanes and VOCs.
- A 1,000 Nm³/hr biogas feed can deliver roughly 13,400 litres/day of diesel equivalent at 87% process efficiency.
- CBM is one of the few waste-to-energy pathways that can be commercially viable without subsidy, particularly where a local vehicle fleet can use the fuel directly.
Get in Touch
Every waste stream, site and market is different, and the right configuration of digester, gas clean-up and compression technology depends on a proper characterisation of your feedstock and local fuel demand. If you’re considering converting biogas or landfill gas into a viable vehicle fuel, get in touch with our team to discuss how a CBM solution could work for your site.