Methane and biogas containment

Posted by Albert Berenguel - 03 May, 2021

Permeability of waterproofing membranes - Part 2

In the second part of this series of posts about the permeability of waterproofing membranes to gases, (see Part 1 “How to prevent Radon gas penetration in concrete structures”) we will review another important gas that has a big effect on the economy and on the environment: Methane.


What is methane?

Methane (CH4) is a colourless and odourless gas that is, in general, very stable. However, mixtures of methane and air, with a methane content between 4% and 16% by volume, are explosive; in coal mines, methane or “firedamp” is much feared by miners.

Methane is generated naturally from the anaerobic decomposition of organic material in natural wetlands, flooded rice fields or organic waste in landfills. Other contributors to methane generation are the fermentation of animal waste and other emissions from livestock production and the burning of biomass (including forest fires, charcoal combustion, and firewood burning).

It is important to mention that methane is the second biggest contributor to climate change, after Carbon Dioxide. Therefore, as part of the EU Green Deal, it is essential to accelerate actions to control methane emissions to achieve targets of climate neutrality by 2050.

Researchers at the NASA Earth Observatory have found that the amount of methane in the Earth’s atmosphere continues to rise. Concentrations of methane in the atmosphere now are about 2.5 times higher than in the 1850s.

However, although methane is an environmental problem, it can also bring environmental benefits as a source of renewable energy that reduces the use of fossil fuels and helps recycle organic waste.

What is Biogas?

Biogas is a mixture of methane, carbon dioxide (CO2), hydrogen sulphide (H2S), water vapour and other trace gases that is produced industrially by anaerobic digestion of a wide range of biomass types including agricultural waste, manure, municipal waste, and primary or secondary crops.

Biogas production has enormous economic benefits, which has made it the third fastest growing renewable energy source in the world after photovoltaic solar and wind power (source: European Biogas Association).

Industrial Biogas plants upgrade waste to valuable fertiliser, allowing for nutrient recycling and renewable energy production.

Biogas as a renewable energy source

According to the European Biogas Association, renewable electricity produced from biogas amounts to roughly 6% of total renewable electricity generation in Europe. Generating power with biogas can deliver greenhouse gas (GHG) savings of 240% compared to EU fossil fuels.

Biogas production is a source of energy that can be used:

  • for the own treatment plant, providing electricity and heat in electricity-only plants, heat-only plants or Combined Heat and Power (CHP) plants.
  • to meet the local heat demand on a farm or for external users.

Biogas can additionally be upgraded to biomethane, with proper purification to remove trace gases such as H2S, water and CO2, and used in natural gas networks or transport vehicles with natural gas engines.

Digestate (the remains of the degraded biomass after the biogas production process) can still be used as a fertiliser, having the same nutrient content as manure. This reduces the use of chemical fertilizers in farms and stops nutrient runoff, a perfect example of a circular economy.

The removal of hydrogen sulphide (H2S) from biogas means that biomethane is not chemically aggressive. But for the biogas digesters, additional measures are needed to prevent corrosion due to potential biogenic acid attack.

Concrete structures are not gastight

Based on its composition, a concrete element with a certain minimum thickness should prevent substances such as water or gas from passing from one side to the other. However, all materials are permeable to gases and vapours to some extent, and concrete is not an exception.

As we explained in the first post in this series, concrete has a strongly connected pore system. If we add to this the presence of cracks, due to drying shrinkage or surface defects during placement, it can be concluded that gases, vapours and even water can find an easy diffusion path to permeate through structures built with this material.

Considering the economic and environmental impacts of methane leakages to the atmosphere, prevention and repair of damage in biogas infrastructure becomes clearly necessary. Also, as part of the EU Methane strategy which was published in October 2020, an obligation to improve leak detection and repair (LDAR) on all fossil gas infrastructure, production, transport and use will be regulated.

Methane barriers and recommended evaluation criteria

To evaluate the capacity of a material to act as a methane barrier, we can refer to DIN 53380 “Testing of plastics – Determination of gas transmission rate – Part 1: Volumetric method for testing of plastic films”, the criteria developed by DLG e.V. (Deutsche Landwirtschafts-Gesellschaft e.V. – German Agriculture Society) and the „Sicherheitsregeln für landwirtschaftliche Biogasanlagen (TI 4)“ (Safety rules for agricultural biogas plants. Both include the following definitions of permeability:

cm3 / m2 · d · bar

Comments

< 10

Material dense to gas

< 400

Very good

400 to < 700

Good

700 to < 1000

Weak

> 1 000

Not acceptable

 

As an additional reference for the evaluation, we can mention the permeability to methane of flexible membranes that are commonly used in low pressure storage biogas holders like HDPE or LDPE. Such membranes provide permeability values between 200 and 500 cm3 / m2 · d · bar.

In the table below are the results and recommended application thickness for two of our materials that have recently been tested as methane barriers:

MasterSeal M 689 is a highly elastic, solvent-free, ultra-fast curing, spray-applied polyurea from Master Builders Solutions that offers high elasticity and crack bridging capacity combined with high chemical resistance.

MasterSeal 7000 CR is a waterproofing and concrete protection system from Master Builders Solutions with a unique combination of application and performance properties that are especially suited for use in the most aggressive environments, such as wastewater treatment plants and biogas facilities, where hydrogen sulphide and biogenic sulphuric acid can be present.

 

MasterSeal M 689

MasterSeal 7000 CR

 

image-png-May-03-2021-06-00-39-77-AM

image-png-May-03-2021-06-01-29-89-AM

Figure 3: MasterSeal M 689 in a sludge digester at a wastewater
treatment plant in Granada (Spain).

Figure 4: Sealed concrete surface with MasterSeal 7000 CR
in a digester in Denmark.

Permeability

195 cm3 / m2 · d · bar

5,97 cm3 / m2 · d · bar

Application thickness

2,1 mm

1,5 mm

Consumption

2,1 kg /m2 for 2 mm thickness.

MS P 770: 1 x 0,35 kg/m2

MS M 790: 2 x 0,5 kg/m2

Results of tests according to ISO 15105-1, “Plastics - Film and Sheeting - Determination of Gas-Transmission Rate - Part 1: Differential-Pressure Method”, equivalent to DIN 53380.

In summary, the use of MasterSeal M 689 or MasterSeal 7000 CR ensures high methane tightness when applied to concrete domes, sealing cracks and defects to prevent gas leakages. This protects the value of the resource and prevents a gas with a strong greenhouse effect from escaping into the atmosphere.

Additionally, MasterSeal 7000 CR offers high specific chemical resistance to hydrogen sulphide (H2S) and to biogenic sulphuric acids, which makes it suitable for biogas digesters as well as biomethane containers.

Find Part III of our series on the "permeability of waterproofing membranes to gases" here:
Increase insufficient concrete cover to reinforcement using coatings and membranes

References: 
Nasa Earth Observatory.
https://earthobservatory.nasa.gov/images/146978/methane-emissions-continue-to-rise
EU Methane Strategy. https://ec.europa.eu/energy/topics/oil-gas-and-coal/methane-emissions_en
EBA: European Biogas Association Statistical report 2020.
DLG e.V. (Deutsche Landwirtschafts-Gesellschaft e.V.) „Sicherheitsregeln für landwirtschaftliche Biogasanlagen (TI 4)“
IEA (2021), Driving Down Methane Leaks from the Oil and Gas Industry, IEA, Paris https://www.iea.org/reports/driving-down-methane-leaks-from-the-oil-and-gas-industry
DIN 53380: Testing of plastics – Determination of gas transmission rate – Part 1: Volumetric method for testing of plastic films.
ISO 15105-1: Plastics - Film and Sheeting - Determination of Gas-Transmission Rate - Part 1: Differential-Pressure Method

 

Topics: Waterproofing, MasterSeal 7000 CR


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