All Biomass Gases Are Not the Same: What Are the Differences Between Biogas, Biomethane, Landfill Gas and Gasification Gas?

Many people believe that only gas produced through the gasification of agricultural and forestry waste is classified as biomass gas. In fact, biogas, biomethane, and landfill gas are also forms of biomass-derived gas.

Although they all fall into the same general category, these four types of gas differ significantly in their sources, composition, calorific values, and impurities. These differences determine their respective applications and utilization methods.

1. Different Sources

Biogas: Produced through the anaerobic digestion of organic waste. Typical sources include livestock farms, wastewater treatment plants, and food waste treatment facilities.

Biomethane: Produced by upgrading and purifying biogas.

Landfill Gas: Generated through the natural decomposition and fermentation of organic matter in landfills.

Gasification Gas (Producer Gas): Produced through the pyrolysis and gasification of dry biomass materials such as straw and wood chips.

2. Different Gas Compositions

Biogas: Primarily consists of CH4 (50%–70%) and CO2 (30%–50%), with small amounts of H2S and moisture.

Biomethane: Primarily consists of CH4 (more than 95%). Most other impurities are removed during the upgrading process, making its composition similar to that of conventional pipeline natural gas.

Landfill Gas: Primarily consists of CH4 (40%–60%) and CO2 (35%–50%). Its composition is similar to biogas, but its methane concentration is generally slightly lower.

Gasification Gas (Producer Gas): Primarily consists of CO (15%–25%) and H2 (10%–20%), with a very low CH4 content. It also contains relatively large amounts of N2 and CO2.

3. Different Calorific Values

Biogas: Approximately 4,800–6,000 kcal/Nm³, roughly half the calorific value of natural gas.

Biomethane: Approximately 8,400–9,600 kcal/Nm³, generally comparable to conventional pipeline natural gas.

Landfill Gas: Approximately 3,600–4,800 kcal/Nm³, slightly lower than that of biogas.

Gasification Gas (Producer Gas): Only approximately 1,000–2,000 kcal/Nm³, making it the lowest among the four types.

4. Different Impurities

Biogas:

The primary concern is hydrogen sulfide (H2S), typically present at concentrations of 1–12 g/m³.

H2S is an acidic gas. When dissolved in water, it can cause corrosion of metal pipelines and valves. Therefore, biogas must undergo desulfurization before utilization.

Industry standards generally require the H2S concentration to be reduced to below 20 mg/m³ after desulfurization.

Desulfurization technologies are relatively mature. Both wet and dry desulfurization methods are widely used, and H2S removal is not particularly difficult.

Biomethane:

H2S, moisture, siloxanes, and other impurities are largely removed during the upgrading and purification process.

As a result, biomethane can generally be used directly according to pipeline natural gas standards. Among the four types of gas, it presents the fewest impurity-related challenges.

Landfill Gas:

Its composition is similar to biogas. In addition to H2S removal, siloxanes must also be eliminated.

Siloxanes mainly originate from residues of everyday products such as cosmetics and detergents.

During combustion, siloxanes are converted into fine SiO2 particles, which can accumulate on spark plugs, cylinder walls, and oxygen sensors, resulting in component wear and ignition failures.

Siloxane concentrations in landfill gas typically range from 7–70 mg/m³, although higher levels may be found in certain landfills based on actual measurements.

Internal combustion engine manufacturers generally require siloxane concentrations to be reduced to below 15 mg/m³.

Siloxane removal is relatively complicated. Activated carbon adsorption and cooling-based separation are commonly used methods, but their treatment costs are higher than those of conventional desulfurization.

Gasification Gas (Producer Gas):

It has the most complex impurity profile, with tar and particulate matter being the main concerns.

At low temperatures, tar can condense and accumulate, potentially blocking pipelines and valves, contaminating lubricating oil, and causing carbon deposits inside engine cylinders.

Particulate matter, meanwhile, can cause mechanical wear of engine components.

Before gasification gas can be supplied to an internal combustion engine, tar and particulate concentrations generally need to be controlled below 50 mg/Nm³.

Among the four types of gas, tar and particulate removal presents the greatest technical challenges.

Tar has a complex chemical composition, while particulate matter often has a very fine particle size. Existing treatment technologies each have their limitations, and achieving low cost, high efficiency, and long-term stable operation simultaneously remains a significant challenge.

5. Different Utilization Methods

Biogas:

The most common application is direct power generation using gas-fired internal combustion engines.

Many livestock farms, wastewater treatment plants, and food waste treatment facilities adopt the following process:

Biogas → Desulfurization → Power Generation

Biogas can also be upgraded into biomethane or burned directly in boilers for heat supply.

Biomethane:

Its applications are essentially the same as those of conventional pipeline natural gas.

It can be injected into municipal gas networks, used as vehicle fuel, or supplied to industrial production processes.

Among the four types of gas, biomethane is the only one that can be readily transported and utilized away from the production site through existing gas infrastructure.

Landfill Gas:

Its utilization methods are relatively limited, with power generation being the primary application.

The electricity generated is mainly supplied to the national grid. A small number of projects are located within industrial parks and adopt a "self-generation for self-consumption, with surplus electricity fed into the grid" operating model.

Gasification Gas (Producer Gas):

Its applications are quite different from those of the other three types.

It can be used for power generation and heat supply. However, its greater potential lies in the production of green fuels and chemicals, such as green methanol, sustainable aviation fuel (SAF), and green ammonia.

Essentially, these four types of gas can be divided into two main categories: biogas, biomethane, and landfill gas are methane-based gases, with CH4 as their primary component. They mainly differ in methane purity and impurity content, while generally featuring higher calorific values and relatively simple compositions. Gasification gas, on the other hand, belongs to the synthesis gas category, with CO and H2 as its primary components. It has a lower calorific value and a more complex composition.
Although all four are classified as biomass-derived gases, they are fundamentally different in terms of both composition and applications. Identifying the type of gas available, understanding its impurities, and selecting the appropriate equipment are the first essential steps in determining whether a project can be successfully implemented.

Disclaimer: The information presented in this article is sourced from publicly available industry information and is intended solely for industry communication and discussion. Project investment decisions and technology selection should be comprehensively evaluated based on actual site conditions. Please exercise due diligence before making any decisions.