What is in effect a methane combustion pledge to reduce massively climate-damaging anthropogenic methane emissions is the excellent news announced on the run-up to the COP26 Climate Change talks in Scotland next month.
Why is Methane Combustion Preferred to Methane Emission?
Methane combustion with the utilization of heat is preferred to reduce the climate change effect from methane discharges. However, simple gas flaring comes second because it's cheap and is much less damaging in terms of GHG emissions than venting landfill gas to the atmosphere from landfills.
Methane when it enters the atmosphere is a short-lived greenhouse gas, which has 80 times more global warming effect than CO2 over its first 10 year-half-life. So, despite the fact that mankind has to reduce CO2 emissions to avoid runaway global warming, it is EVEN MORE important to as far as possible stop human-emitted methane.
Methane combustion does that by converting the CH4 molecules into CO2 and water. Combusting (burning or flaring) it does this whether or not the methane has been made as a renewable energy source in a biogas plant or it is a fossil fuel (non-renewable).
Also, scientists have pointed out that because methane in the atmosphere dissipates much more rapidly than carbon dioxide this will have a much bigger effect in the short term in reducing the upward trend of global temperatures than the equivalent amount of CO2 emission abatement.
That's at the core of the praise provided for the US and EU governments for going ahead and leading the way with this new climate change reducing pledge as follows:
WBA Press Release 22 September 2021:
US-EU Methane Pledge: rapid rollout of anaerobic digestion and biogas required to achieve 30% methane emissions reduction by 2030 – says World Biogas Association
- The US and EU have announced a Global Methane Pledge to deliver a 30% reduction in methane emissions by 2030 at the 2021 Major Economies Forum on Energy and Climate last week. The Pledge will be formally launched at COP26 in November.
- Seven other countries have also indicated support for the pledge: Argentina, Ghana, Indonesia, Iraq, Italy, Mexico and the United Kingdom.
- Global trade body the World Biogas Association (WBA) says a rapid rollout of anaerobic digestion (AD) technology can help deliver on this commitment.
- Curbing methane emissions can reduce global warming by around one-third of a degree (0.3°C). AD is recognised by the EU, UN and Climate and Clean Air Coalition as a low-cost readily available technology to do so.
President Biden and European Commission President Ursula von der Leyen launched the Global Methane Pledge in the last few days, in which nations pledge to decrease global methane emissions by at least 30% from 2020 levels by 2030.
They made the statement during the Major Economies Forum (MEF) on Energy and Climate, praising the commitment from a number of MEF countries and urged additional governments to join the promise ahead of the formal opening of the COP26 talks in Glasgow in November.
Reacting to the news, Charlotte Morton, Chief Executive of the World Biogas Association (WBA), said:
“We welcome this decisive action on the part of the EU and US. The commitment to curbing methane emissions is a clear goal that can be achieved this decade. Ensuring all organic wastes are collected and recycled through anaerobic digestion is critical to achieving this.
We, humans, produce 105 billion tonnes of methane-emitting organic wastes annually. These are packed with valuable minerals that can be used to restore soils through the creation of biofertilizers while also producing energy, bio-CO2 and transport fuels. At its full potential, the AD sector can capture these wastes and deliver a 10% cut in global greenhouse gas emissions by 2030. It is recognised by the EU, UN and Climate and Clean Air Coalition as a low-cost readily available technology. But we need the full deployment of AD to happen really fast to deliver on this by 2030.
We look forward to coordinating a response to the Global Methane Pledge with national governments and international bodies. The commitment will also prove valuable to COVID recovery planning, creating hundreds of thousands of skilled jobs in the process.”
– ENDS –
Methane Combustion versus Other Hydrocarbon Fuels
Methane combustion is no different when burnt to any other fuel. All fuels have a fairly similar response when burned:
Carbon dioxide, water, and energy are produced when fuel (any hydrocarbon source) is combined with oxygen and pout simply that's what occurs during combustion (burning).
For methane, a basic combustion process is provided below.
Methane combustion implies that it is feasible to burn it. This combustion process is chemically composed of a reaction between methane and oxygen in the air.
When this reaction occurs, the end product is carbon dioxide (CO2), water (H2O), and a lot of energy.
Combustion Reactions
Methane combustion is represented by the following reaction:
CH4[g] + 2 O2[g] -> CO2[g] + 2 H2O[g] + energy
– the [g] denotes gaseous state.
One molecule of methane reacts with two oxygen molecules to create a carbon dioxide molecule and two water molecules, which are generally given off as steam or water vapour throughout the reaction plus energy.
Natural gas which is almost 100% methane is a non-renewable (fossil fuel a mineral/ geological) resource. However, it is the most environmentally friendly fossil fuel.
The other fossil fuels, coal and oil, are more chemically complex than natural gas. The result is that when burned those emit a range of potentially hazardous air pollutants.
When methane is burned, it produces solely carbon dioxide and water. Because natural gas is mainly methane, burning it produces fewer byproducts than burning other fossil fuels.
It is also of higher calorific value than coal. That means that for each unit of heat, less carbon dioxide has to be emitted to the atmosphere.
The Principle of Combustion Reactions
In combustion reactions (burning) the products' energies are lower than the reactants' energies.
Excess energy is discharged during reaction in the form of heat and light.
This is best explained by saying that all matter gravitates toward lower energy levels. That's a basic law of nature and called the Law of Entropy.
The way to think of this is to imagine a ball rolling down a slope, all physical reactions tend toward the bottom of the slope.
Exothermic reactions are more likely than endothermic ones. Endothermic processes are those that absorb energy. The products of these reactions have more energy than the reactants. Endothermic reactions are less common.
It's unusual, (to say the least!) to witness a ball spontaneously rolling upward.
When entropy drives the process, endothermic reactions can occur (pushes the ball up the hill). But, these are considerably less common responses. In those chemical hot packs you can buy such as hand and foot warmers, an exothermic reaction occurs. In a chemical cold pack, an endothermic reaction occurs.
Activation Power and Ignition of Combustion
When methane and oxygen are combined, a reaction does not occur immediately. There is a stumbling block in the way of the response. This barrier is caused by the fact that in order to produce CO2 and H2O, four carbon-hydrogen bonds and some oxygen-oxygen bonds must be broken. However, when the carbon-oxygen and hydrogen-oxygen bonds are formed, the initial energy input yields a greater energy payback.
The activation energy is the name given to the energy barrier. The energy released when methane burns is referred to as the “net energy” of the reaction.
How can you break over the initial energy barrier?
Typically, the reactants are ignited by a lighter or a spark. When we begin the reaction, the energy released allows additional reactions to overcome their activation energy, and the chain reaction of fire begins.
Why Natural Gas has for so Long Been Touted as Clean and Relatively Climate Friendly
Natural gas has been chosen for widespread use (with methane as its primary component) because is an appealing energy source. This is due to its availability and high heat of burning per mole of carbon dioxide produced.
However, the pollutants produced by traditional flame combustion (mostly NOx) have a negative impact on the environment and human health.
We also now know that fossil fuel burning is creating a build-up of carbon dioxide which is not sustainable. As there is no viable technology available to capture and hold the carbon dioxide produced by fossil fuels, they have to be phased out in a measure which is called “decarbonization”.
Technical Facts About Methane Combustible Fuels?
Methane, having the molecular formula CH4, is an alkane. It may undergo hydrocarbon combustion, which produces heat as hydrocarbons do. Methane is the primary hydrocarbon component of natural gas, the fossil fuel used in gas distribution networks globally.
At normal temperatures and pressures, it is a gas that accounts for approximately 95 percent of the content of liquefied natural gas and around 80-90 percent of natural gas.
Methane, like carbon dioxide, is a greenhouse gas (CO2). It has a shorter atmospheric lifespan than CO2, at 12 years, but this is “balanced” by the fact that methane is more effective at trapping heat than CO2, with a GWP (Global warming potential) of previously reported at 21. However, recently scientists have re-assessed this gas a having a far higher global warming effect. As stated earlier, the effect is 80 times more global warming (GHG) effect than CO2.
Methane combustion accounts for a large portion of the world's primary energy and is used for house heating, cooking food, heating water, and electricity generation. It can even supply transportation energy. However, because methane creates a substantial proportion of the carbon dioxide that people release into the atmosphere, it is also a big contributor to climate change.
Combustion of Renewable Methane Produced by the Anaerobic Digestion Process
The following is our assessment of the future of methane combustion as now supported by many governments.
Over the next 10 years especially natural gas will be phased out and replaced by renewable methane.
Hydrogen may follow, but in the short term, before hydrogen becomes available, sustainable methane will be mostly that produced by the anaerobic digestion (AD) process. The raw gas from AD is called biogas, and when that is purified to gas distribution grid quality it is known as biomethane.
An Introduction to Biogas and Biomethane
The argument for biogas and biomethane is at the crossroads of two key modern-day challenges:
- coping with the rising quantity of organic waste produced by contemporary society and economy, and
- reducing global greenhouse gas (GHG) emissions.
The generation of biogas or biomethane, which converts organic waste into a renewable energy resource, provides a glimpse into a society in which:
- resources are continually utilised and reused, and
- in which growing demand for energy services may be satisfied while simultaneously offering broader environmental advantages.
What are Biogas and Biomethane?
Biomethane is a flexible fuel generated by Anaerobic Digestion (AD) and used in a variety of applications.
Farm-derived waste feedstocks provide a major potential biomass resource for producing biomethane. Farm wastes and residues, such as manures and slurries, are plentiful, and present treatment options which traditionally has meant only one thing.
That method of disposal has been directly distributed to the fields of the farm, which tends to increase emissions.
By contrast, AD provides on-site waste management for farms, producing organic fertiliser as well as biogas.
Crop silage is often utilised to boost energy outputs and improve economics owing to the seasonality and lower biogas yields of crop wastes and food leftovers.
A range of different feedstocks can be used to produce biogas and biomethane
Modern communities and economies generate a growing amount of organic waste, which may be utilised to generate clean energy, with several potential benefits for sustainable development.
Biogas and biomethane are distinct products with distinct applications, but they both derive from a variety of organic feedstocks whose potential is now underutilised.
The creation and use of these gases exemplify the concept of a more circular economy, offering benefits such as lower emissions, improved waste management, and increased resource efficiency.
Gaseous pollutants from biogas combustion
Among all the gaseous pollutants considered in the direct emission from biogas combustion, nitrogen oxides (NOx) levels are worthy of concern in case studies of current farming land spreading practices.
Volatile organic molecules, on the other hand, do not appear to be a major concern for the digested AD output of fertilizer.
In order to completely analyse the long-term influence of digestate distribution on soil quality, further research is required to resolve matters such as metal content which may build up in the soil when MSW (organic fraction is used as a feedstock).
Nevertheless, in the medium to short term, digestate is superior to untreated biomass for land application.
Impact of biogas upgrading to biomethane
The impact of biogas upgrading to biomethane is one of a sustainable product. A renewable fuel made from the recent sun's energy. It is a pure product that is suitable for all uses previously attributed to natural gas.
However, the already carbon negative impact will be even lower if the carbon dioxide produced, and already captured in the process, is sold at an additional profit
Biomethane Combustion Landfill Gas and Safety Flares
Safety flares (with contained combustion in the flue chamber) must be provided at all commercial-scale biogas plants and biomethane upgrading plants for safety reasons and for essential Greenhouse Gas Emission Reduction.
These are usually specified to be dual-fuel biogas/biomethane combustion (enclosed flame types). Several top companies have developed a family of safety flares (HTB type).
These are capable of burning either “low quality” biomethane that has not been converted to natural gas or raw biogas that has bypassed the upgrading/purification facility in a controlled setting. The fundamental design and range of biogas flares has been enhanced and designed with particular technical solutions that make flare operation suited for the purpose.
Municipal solid waste dumps account for more than a quarter of all methane emissions in the United States. These now all need to have their own landfill gas extraction systems fitted with a flare used to burn landfill methane biogas produced. Alternatively, rather than losing the energy from flare burning, the biogas is used with an electric generator to supply power to the local electrical grid.
Landfill gas is an especially appealing natural gas supply alternative since it is a low-cost feedstock source due to the little processing required to remove contaminants in order to generate biomethane.
Biogas is often high in methane (approximately 65 per cent) and pollutants such as hydrogen sulphide (H2S), carbon dioxide (CO2), and water.
Through processing, technology is now commercially available to remove H2S, CO2, and water pollutants from biogas and landfill gas. The resulting biomethane is renewable and a sustainable energy source
Attempting to reduce methane emissions will have little effect. Seafloor methane is currently being released into the atmosphere as a result of rising waters.