What is Green Gas? Is it a Scam?
Green gas is a promising renewable energy source that can be used in the same way as energy produced by fossil fuels - but without the harsh environmental impact. Here we take a look at what green gas is, which energy providers offer green gas tariffs and how it is produced.
What is green gas?
Green gas refers to biofuel products sourced from decomposing biodegradable materials such as human waste, manure, crops and other organic matter - all of which are generally subsumed under the term biomass in the context of energy production.
The primary green gas biofuel released from the decomposition of organic matter is known as biogas, which is harvested in large quantities in biogas plants. A derivative biofuel called biomethane is also produced in these plants by concentrating and refining the methane present in biogas.
Both biogas and biomethane can be used for generating energy in the same way as fossil fuels, although each has a distinct application in the energy system.
UK net-zero emissions targetIn June 2019 the UK became the first G7 country to set a legally binding net-zero emissions target. The 2050 Target Amendment to The Climate Change Act 2008 commits the UK to reduce all greenhouse gas emissions by 100% of 1990 levels - net-zero - by 2050.
Biogas is a naturally occurring by-product of decaying organic matter, readily found in landfills, compost heaps and swamps. It is made up primarily of methane and carbon dioxide - with trace levels of other contaminants, making it highly combustible and, as such, apt for energy production.
Raw biogas extracted in biogas plants can be burned near the point of production to generate electricity and heat to be consumed locally, stored for future consumption or exported.
Green gas in this form cannot, however, be integrated into the gas grid and used interchangeably with extant natural gas. The latter is predominantly methane and has been treated to meet gas quality and safety requirements; moreover, it has distinct thermal qualities.
Biogas, on the other hand, is rather unpolished by comparison. This is to say, it is not pipeline quality. Indeed, its injection into the gas grid would be harmful to both the grid and the end-user.
Biomethane is produced in a treatment plant where the methane present in biogas is purified, ‘scrubbed’ and concentrated to levels equal to or greater than 95%. The resultant biofuel (biomethane) thus acquires the same properties and quality certification conditions as natural gas.
Following the treatment process, Biomethane can be injected into the gas network and used in domestic and industrial gas appliances. Of course, in our current energy context, it is used in conjunction with natural gas, though it has been touted, along with other forms of eco gases - namely, green hydrogen - as the green alternative.
How does it differ from natural gas?
Natural gas is a fossil fuel. Much like oil and coal, it is a product of natural processes that convert plant and animal matter into gaseous hydrocarbons over millions of years.
These hydrocarbons rise close to the earth’s surface over time and are extracted through such means as vertical drilling, fracking, and as by-products of other fossil fuel extraction processes.
Crucially, fossil fuels are finite resources and carbon-intensive from extraction to end-use. The former means that fossil fuels diminish over time; the latter contributes to the climate crisis by emitting more greenhouse gases into the atmosphere than are being removed (surplus emissions).
Green gas biofuels differ from natural gas on these two points. Not only are they sourced from renewable organic materials, but they also have the potential to achieve carbon neutrality and, therefore, reduce surplus emissions.
Green Gas & Greenhouse GasesDon't get green gas mixed up with greenhouse gases! Green gas is a renewable energy source that releases greenhouse gases when burned, although not as much as fossil fuels. Greenhouse gases trap heat in the atmosphere and, in our production of surplus emissions, have contributed to global warming.
Is green gas renewable?
Yes. Green gas is a renewable energy source. Organic materials like food, animal and agricultural waste, used in the production of green gas biofuels, are easily renewed, and at a faster rate than fossil fuels.
Other materials like grass and wheat crops, algae, wood and straw require careful management but are also relatively easy to replace.
How does it affect the environment?
This is a more complex matter than the question suggests. Green gas puts to use greenhouse gases - namely, methane, which is far more potent than carbon dioxide - that would have otherwise been released into the atmosphere by the natural decay of the organic matter used to produce it.
And although the burning of green gas for the generation of energy does release carbon dioxide into the atmosphere, studies have shown that it is quantifiably less than the amount of CO2 released from burning fossil fuels, thus making it comparatively better for the environment.
Is green gas carbon neutral?
While often proclaimed as such, green gas is by no means inherently carbon neutral. Rather, it requires an emissions mitigation network to ensure that our carbon balance and cycle is equilibrated. This includes:
- Low carbon green gas infrastructure
- Sustained reforestation
- Careful management of energy crops
- Carbon capture and storage
- The integration of renewables in energy systems
- The phase-out of fossil fuels
Consumers should be aware that, currently, energy suppliers offering ‘carbon-neutral’ gas options apportion a minuscule percentage of green gas in their gas mixes. The majority rely heavily on natural gas which they offset with carbon credits.
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Green gas suppliers in the UK
There are a growing number of UK electricity and gas providers that focus on integrating green gas in their tariffs. However, at present, only Green Energy UK offers 100% green gas on their tariffs. The majority of other green energy suppliers, such as Bulb, Ecotricity, Good Energy and Ovo offer a percentage of green gas with the rest of the emissions produced being carbon offset.
Where does green gas come from?
There are four types of energy plants that can produce green gas: three biogas plants, each employing different methods to break down and collect organic materials, and one biomethane treatment plant.
Below are descriptions of the processes used in each biogas production plant:
- Anaerobic digestion (AD):
Anaerobic digestion (AD) plants remove oxygen from sealed tanks in which organic materials such as agricultural waste, manure, sewage, grass crops and other ‘energy crops’ are left to decay.
Microorganisms break down and digest these organic materials, in the process releasing methane-rich gas (biogas). The absence of oxygen is crucial as it allows for a higher concentration of methane.
The Biogas produced is either stored for generating energy or moved on for treatment in a purification plant. The residual waste from the organic material is used for fertilisation.
- Thermal Gasification:
Thermal Gasification plants primarily use wood chips, straw, and seaweed or other marine algae. These materials are hermetically sealed in tanks and heated to very high temperatures.
Oxygen or steam is injected to induce gasification reactions that produce biogas, which is collected and either stored for consumption or treated in a purification plant. Residual waste can also be used for fertilisation.
- Landfill biogas collection:
Landfill plants collect biogas that has been produced passively by waste products in landfills.
Although not quite as productive as AD or gasification, these plants can still play a crucial role in cutting emissions by putting to use greenhouse gases that would have otherwise been released into the atmosphere.
The biogas collected is used in the same way as biogas from AD and Thermal Gasification plants
Biomethane production plants
Biogas extracted from the methods outlined in the preceding section can be treated in a purification plant to produce biomethane. This production process includes concentrating methane to levels equal to that of natural gas (95% or over) and removing carbon dioxide along with other toxic gases and water vapour.
Propane may be added to increase biomethane’s heating power (Calorific Value), and odorant applied to eliminate unpleasant smells.
The road to net-zero emissions
Britain has more than doubled the number of biogas plants in operation since 2015. Currently, there are more than 640 AD biogas plants, 583 of which produce, use or export electricity; 42 of them produce and use heat; and 102 are used for producing biomethane for the national gas grid.
On the way to net-zero emissions, biomethane is of particular importance, as natural gas accounts for almost two-thirds of domestic energy demand. According to a report commissioned by the Energy Networks Association, £109-122bn of investment is required to decarbonise Britain’s gas network by 2050.
Green gas around Europe
Other European countries are investing in green gas production for their national energy mixes and in some cases for their export markets too. Learning and partnering with them may hold the key to improving Britain's energy independence and renewable energy production over the next decade.
Germany relies on its green gas capacity to generate 1.7% of its renewable electricity. Additionally, 20% of fuel used by gas-powered green buses and lorries comes exclusively from sustainable green gas.
Germany has the largest amount of green methane gas facilities in Europe, with almost 200 plants so far. This allows them to export green gas.
Sweden has built several large-scale green gas facilities that use forestry residues, dung, wastewater and food waste as biomass for biomethane production.
The biomethane produced in these facilities will be sent directly to Sweden's national gas grid for use in heating, electricity production and transport. Sweden is looking to green gas as a way to meet stringent air quality and emission reduction deadlines as part of its energy policy.