Green gas or renewable gas includes biogas/biomethane and renewable hydrogen involving different production methods (anaerobic digestion, biomass gasification, electrolysis to hydrogen, power to gas).
Green gas can have a considerable impact in future energy systems through sector integration and play a key role in decarbonising heat and transport. This session considered the state of the art of green gas and development opportunities.
Presentations included: State of the art in Green Gas; Integration and flexibilization of biogas systems; Increasing the green gas resource with gasification technologies; Hydrogen in Australia; and Innovation from an industry perspective.
Jerry Murphy, Director SFI MaREI Centre for Energy, Climate and Marine, University College Cork, Ireland
State of the art in Green Gas
Jerry Murphy , Director SFI MaREI Centre for Energy, Climate and Marine, University College Cork, Ireland
Integration and flexibilization of biogas systems
Jan Liebetrau, Head of the Department Consulting and Research, Rytec GmbH, Germany
Increasing the green gas resource with gasification technologies
Berend Vreugdenhil, Senior Scientist Specialist Biomass and Circular Technologies, TNO, The Netherlands
Green Hydrogen developments – Australia
Amy Philbrook, Future Fuels and Renewables, ATCO Group, Australia
Innovation from an industry perspective
Ole Hvelplund, CEO, Nature Energy, Denmark
- In the EU and US, up to twice as much energy is sourced from gas grids as electricity grids. Fossil gas replacement requires much more attention. Three green gas options are generally considered: (1) biomethane produced from anaerobic digestion (AD) or from gasification processes; (2) green hydrogen; (3) synthetic methane produced from hydrogen combined with CO2.
- In the near future the integration of energy vectors (power, heat, gas) will be essential to facilitate variable renewables such as solar or wind energy, where dispatchable renewable energy sources such as bioenergy gain importance for grid balancing and cover seasonal fluctuations (particularly for heat). Biogas plant operation itself can be controlled extensively and with this control comes high levels of flexibility (for power production or other uses). Nevertheless, flexibility comes with an extra cost as it results in reduced capacity utilization and/or requires extra gas storage capacity; these costs need to be balanced by financial benefits.
- Biogas is circular economy at its best. It generally starts from organic wastes and/or farm wastes; the co-product of AD is a digestate that can go back to the field as efficient fertiliser. The biogas can be used for local heat/electricity demand, or it can be upgraded to biomethane which can be injected in the gas grid and used for different applications instead of fossil natural gas. When hydrogen is used in the upgrading process it can boost the methane production by up to 67% (from reaction of hydrogen with CO2 from the biogas). Alternatively, the CO2 can be separated and used for other industry applications. In Denmark, biomethane already represent 25% of the gas grid. Several large-scale biogas plants have been built, and they can be replicated in all parts of the world.
- Next to the anaerobic digestion pathways, biomethane can also be produced through gasification, followed by methane synthesis. This opens up a broader biomass resource base and could also be done in more central facilities. CO2 from the process can be captured and sequestered, which can lead to negative emissions. Biochar co-products can also be sequestered in soils.
- Hydrogen currently receives a lot of attention, also in government support programmes. There are different markets where it could be used, for example chemical and refining industries (which already use fossil-based hydrogen), heavy industries, transport, power production, or to produce power-to-X fuels such as methane, methanol, or ammonia. At the moment it is unclear which markets will be the main driver for green hydrogen in the coming years/decades and it will depend on the willingness to pay in these markets. Replacing existing hydrogen uses by renewable hydrogen would be least complex; the highest paying capacity currently seems to come from transport, although the implementation would be much more complex, requiring building hydrogen infrastructure / filling stations and investing in fuel cell vehicles (while direct use of electricity is more efficient).
- Australia has high prospects for producing renewable hydrogen as it has very windy and sunny areas and a lot of land available. First electrolyser plants are being supported and constructed at a scale of 10MW. Hydrogen is mainly considered for export on the longer term but can also be used to decarbonize national gas networks. International export of hydrogen tends to shift to intermediates such as ammonia, methane of methanol.
- Overall, it was concluded that different technologies are not competing but complementing. There is still a large undersupply of green electricity for what it is expected to produce in future and enormous efforts will be needed in that area. Taking care of waste products and valorising biogas and its co-products is an option that can make a difference today.