Biomethane
Biomethane sales in BC
Anaerobic digestion systems owners in BC can sell their biogas to Terasen Gas Inc.
Under this program, anaerobic digestion system owners can sell either raw biogas or biomethane (see ‘biogas upgrading equipment’ below) to Terasen Gas for injection into their distribution system. While the price paid for the raw biogas and biomethane will vary between projects, Terasen Gas has set a maximum of $15/GJ for biomethane, and less (due to the cost of upgrading) for raw biogas.
For more information on Terasen Gas’s Biomethane project, please click here or view the document on the right-hand of this page
Biogas upgrading equipment
Upgrading of biogas to biomethane requires the removal of inert compounds such as carbon dioxide and nitrogen to enhance the energy content of the gas (i.e., get it to 97% methane). However, this technology is expensive and is generally only economically feasible for anaerobic digestion system that will generate 500kW or more.
The following technologies can be used to upgrade biogas to biomethane:
- Water wash: the most commonly used upgrading technology in Sweden, this system dissolves carbon dioxide and biogas into water at high pressure, just like in a can of soda. The water is then sent to a flash tank, where a reduction in pressure causes the biomethane to rise to the surface, where it is removed.
- Chemisorption and physisorption: this is similar to the water wash, except that it uses organic solvents instead of water.
- Pressure swing adsorption: the second most common upgrading technology in Sweden, this system uses four phases to trap selected molecules in an adsorbent medium that are released at lower pressure. These phases are pressure build-up; adsorption; depressurization; and regeneration.
- Membrane separation: selectively permeable membranes are used to retain methane on one side, while carbon dioxide migrates through the membrane due to a pressure differential on the other side.
- Cryogenic distillation: methane and carbon dioxide condense and freeze at different atmospheric pressures. This technology takes advantage of this fact to separate the two gases in different phases.
Feasibility Study – Biogas upgrading and grid injection in the Fraser Valley, BC
One of the key findings from the electricity feasibility study was that natural gas prices in BC mean that AD may have a greater likelihood of success if the biogas is upgraded to biomethane. This conclusion resulted in a second multi-industry and agency initiative in 2008 to determine the economic and technical feasibility of upgrading biogas to biomethane for injection into the gas grid. The key findings of this report were that biogas upgrading:
- Total biomethane potential from organic waste material in the Fraser Valley is estimated at 120 million m3/yr (approximately 3.5% of current lower mainland natural gas consumption),
- Automotive application of biomethane has the potential to:
- displace over 100 million litres of diesel,
- reduce greenhouse gas emissions by 335,000 tonnes per year, and
- significant improvement of air quality in the lower mainland,
- In BC, conversion of biogas energy into biomethane presents clear economical and environmental advantages to conversion into electricity,
- On-farm biomethane production can deliver renewable natural gas at a competitive price to fossil natural gas,
- The development of a biogas industry in the Fraser Valley would stimulate rural economic development and funnel significant revenue into a local rural economy.
For a copy of the report, please see the document on the right hand side of this page.
- Terasen Gas.pdf (1.2 MB)
- Biomethane Feasibility Study.pdf (2.9 MB)
