What is Biogas?

Biogas most commonly known as biomethane is a renewable fuel constructed through the breakdown of organic matter (such as animal manure, municipal rubbish/ waste, plant material, food waste or sewage) by bacteria in an oxygen-free environment through a process called anaerobic digestion. Biogas systems use anaerobic digestion to repurpose these organic materials, converting them into biogas, of which consists of both energy (gas), and valuable soil products (liquids and solids). It can be used for many different functions; these include vehicle fuel and for heating and electricity generation.  

What industries is Biogas used in?

Biogas can be produced through the combustion process to produce heat only. When burned, one cubic metre of biogas produces around 2.0/2.5 kWh of thermal energy, providing the nearby buildings with the heat generated. The unused heat is dismissed, and unless it is heated and converted into hot water through a local pipe network into local houses, it is wasted. This concept of heating water and transferring to homes as part of central heating is popular in some Scandinavian countries. 

Biogas is eligible for support under the Renewable Transport Fuel Obligation due to the combustion of biomethane from vehicles being more environmentally friendly than those who use transport fuels such as modern petrol and diesel, thereby helping reduce greenhouse emissions. Examples of renewable transport fuels in vehicles that are formed out of biogas are compressed natural gas (CNG) or liquefied natural gas (LNG).  

Electricity can be generated from the combustion of biogas. Electricity is easier to transport and measure than heat and gas supply, however, requires the right infrastructure in order for it to feed into the grid, that is expensive and complex. Although, generating green electricity can benefit the generators (households and communities) by using the Feed-in Tariffs (FiTs) or for bigger players can maximise the Renewable Obligation Certificates (ROCs) for industrial scale production, thereby leading to a reduction in cost as well as being better for the environment. 

Other industries include hospitality, manufacturing, retail and wholesale. 

Which gases does Biogas contain? 

Biogas consists mainly of methane and carbon dioxide. The most common ratio is 60% CH4 (methane) and 40% CO2 (carbon dioxide), However, the respective quantities of these will vary depending on the type of waste involved in the production of the resulting biogas, therefore the most common ratio will be 45 to 75% methane and carbon dioxide from 55 to 25%. Biogas also contains small amounts of hydrogen sulphide, siloxanes and some moisture.  

What are the key benefits?

There are several reasons why biogas technology is useful as an alternate form of technology: Primarily, the raw material used is very cheap, and to farmers it is practically free with the biogas having the ability to be used for a range of household and farming applications. The burning of biogas does not produce harmful gases; therefore, it is environmentally clean. One of the most convenient benefits of biogas is that the technology required for its production is relatively simple and can be reproduced in large or small scale without the need for a large initial capital investment. As this type of energy is a renewable, clean source of energy that relies on a carbon-neutral process, therefore no new amounts of carbon are released into the atmosphere when using biogas. As well as it helping to divert food waste from landfills, positively impacting the environment and economics. Biogas also helps to reduce soil and water contamination from animal and human waste, allowing for the maintenance of a healthy and safe environment for many communities worldwide. With methane being a contributor to climate change, biogas contributes to its reduction that is emitted into the atmosphere, helping to counteract its impact on climate change, thereby helping to possibly help with its immediate impact on the environment.  

However, biogas as a source of energy does have its disadvantages, one is that Biogas production is dependent on a biological process that doesn’t have the ability to be controlled fully. Additionally, biogas works better in warmer climates, this consequently means biogas doesn’t have the capacity to be accessible equally worldwide. 

Is Biogas Good or Bad?

Biogas is an outstanding source of clean energy, due to it possessing a lower impact on the environment than fossil fuels. Although biogas doesn’t have a zero impact on the ecosystems, it is carbon neutral. This is because biogas is produced from plant matter, of which has previously fixed carbon from carbon dioxide in the atmosphere. A balance between the carbon being let out as a result of producing biogas and the amount absorbed from the atmosphere is maintained. 

Identifying Leaks from Natural Gas pipelines at a Safe Distance

The use of natural gas, of which methane is the principle component, is increasing worldwide. It also has many industrial uses, such as the manufacture of chemicals like ammonia, methanol, butane, ethane, propane and acetic acid; it is also an ingredient in products as diverse as fertilizer, antifreeze, plastics, pharmaceuticals and fabrics.

Natural gas is transported in several ways: through pipelines in gaseous form; as liquefied natural gas (LNG) or compressed natural gas (CNG). LNG is the normal method for transporting the gas over very long distances, such as across oceans, while CNG is usually carried by tanker trucks over short distances. Pipelines are the preferred transport choice for long distances over land (and sometimes offshore), such as between Russia and central Europe. Local distribution companies also deliver natural gas to commercial and domestic users across utility networks within countries, regions and municipalities.

Regular maintenance of gas distribution systems is essential. Identifying and rectifying gas leaks is also an integral part of any maintenance programme, but it is notoriously difficult in many urban and industrial environments, as the gas pipes may be located underground, overhead, in ceilings, behind walls and bulkheads or in otherwise inaccessible locations such as locked buildings. Until recently, suspected leaks from these pipelines could lead to whole areas being cordoned off until the location of the leak was found.

Precisely because conventional gas detectors – such as those utilising catalytic combustion, flame ionisation or semiconductor technology – are not capable of remote gas detection and are therefore unable to detect gas leaks in hard to access pipelines, there has been a lot of recent research into ways of detecting methane gas remotely.

Remote Detection

Cutting edge technologies are now becoming available which allow the remote detection and identification of leaks with pinpoint accuracy. Hand-held units, for example, can now detect methane at distances of up to 100 metres, while aircraft-mounted systems can identify leaks half a kilometre away. These new technologies are transforming the way natural gas leaks are detected and dealt with.

Remote sensing is achieved using infrared laser absorption spectroscopy. Because methane absorbs a specific wavelength of infrared light, these instruments emit infrared lasers. The laser beam is directed to wherever the leak is suspected, such as a gas pipe or a ceiling. Because some of the light is absorbed by the methane, the light received back provides a measurement of absorption by the gas. A useful feature of these systems is the fact that the laser beam can penetrate transparent surfaces, such as glass or perspex, so it may be possible to test an enclosed space prior to entering it. The detectors measure the average methane gas density between the detector and target. Readings on the handheld units are given in ppm-m (a product of the concentration of methane cloud (ppm) and path length (m)). In this way, methane leaks can be quickly confirmed by pointing a laser beam towards the suspected leak or along a survey line, for example.

An important difference between the new technology and conventional methane detectors is that the new systems measure average methane concentration, rather than detecting methane at a single point – this gives a more accurate indication of the severity of the leak.

Applications for hand-held devices include:

  • Pipeline surveys
  • Gas plant
  • Industrial and commercial property surveys
  • Emergency call out
  • Landfill gas monitoring
  • Road surface survey

Municipal Distribution Networks

The benefits of remote technology for monitoring pipelines in urban settings are now being realised.

The ability of remote detection devices to monitor gas leaks from a distance makes them extremely useful tools in emergencies. Operators can stay away from potentially dangerous leak sources when checking the presence of gas in closed premises or confined spaces as the technology allows them to monitor the situation without actually gaining access. Not only is this process easier and quicker, but it is also safe. Moreover, it is not affected by other gases present in the atmosphere since the detectors are calibrated to only detect methane – therefore there is no danger of getting false signals, which is important in emergency situations.

The principle of remote detection is also applied when inspecting risers (the above-ground pipes carrying gas to the customers’ premises and normally running along the building outside walls). In this case, the operators point the device towards the pipe, following its route; they can do this from ground level, without having to use ladders or access the customers’ properties.

Hazardous Areas

In addition to detecting gas leaks from municipal distribution networks, explosion-proof, ATEX approved devices can be used in Zone 1 hazardous areas such as petrochemical plants, oil refineries, LNG terminals and vessels, as well as certain mining applications.

When inspecting an LNG/LPG underground tank, for example, an explosion-proof device would be required within 7.5 metres of the tank itself and one metre around the safety valve. Operators therefore need to be fully aware of these restrictions and equipped with the appropriate equipment type.

GPS Coordination

Some instruments now allow spot methane readings to be taken at various points around a site – such as an LNG terminal – automatically generating GPS tracking of the measurement readings and locations. This makes return trips for additional investigations far more efficient, while also providing a bona-fide record of confirmed inspection activity – often a prerequisite for regulatory compliance.

Aerial Detection

Moving beyond hand-held devices, there are also remote methane detectors which can be fitted to aircraft and which detect leaks from gas pipelines over hundreds of kilometres. These systems can detect methane levels at concentrations as small as 0.5ppm up to 500 metres away and include a real-time moving map display of gas concentrations as the survey is conducted.

The way these systems work is relatively simple. A remote detector is attached beneath the aircraft’s fuselage (usually a helicopter). As with the handheld device, the unit produces an infrared laser signal, which is deflected by any methane leakage within its path; higher methane levels result in more beam deflection. These systems also utilise GPS, so the pilot can follow a real-time moving map GPS route display of the pipeline, with a real-time display of aircraft path, gas leaks and concentration (in ppm) presented to the crew at all times. An audible alarm can be set for a desired gas concentration, allowing the pilot to approach for closer investigation.

Conclusion

The range of remote methane detection systems is increasing rapidly, with new technologies being developed all the time. All these devices, whether hand-held or fitted to aircraft, allow quick, safe and highly targeted identification of leaks – whether beneath the pavement, in a city or across hundreds of kilometres of Alaskan tundra. This not only helps prevent wasteful and costly emissions – it also ensures personnel working on or near the pipelines are not exposed to unnecessary danger.

Because the use of natural gas is increasing worldwide we foresee rapid technological advances in remote gas detection in applications as diverse as leak survey, transmission integrity, plant and facilities management, agriculture and waste management, as well as process engineering applications such as coke and steel production. Each of these areas have situations where access may be difficult, combined with the need to put personnel protection at the top of the agenda. Opportunities for remote methane detectors are therefore growing all the time.

 

Gas Detection in Wastewater

There are many questions about the right approach to monitoring hazardous gases in the wastewater industry. One way I suggest, is to break it down into three main areas for consideration:

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Monitoring and Analysis of Landfill Gases

As recycling becomes more common, use of landfill is reducing, but it is still an important means of waste disposal. For example, 2012-13 figures from Defra (department of the environment, food and rural affairs) for England show that 8.51 million tonnes, or 33.9%, of waste collected by local authorities went to landfill.

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Cross Calibration of Pellistor (Catalytic Flame) Sensors‡

After last week’s comparative levity, this week, I am discussing something rather more serious.

When it comes to detecting hydrocarbons, we often don’t have a cylinder of target gas available to perform a straight calibration, so we use a surrogate gas and cross calibrate. This is a problem because pellistor’s give relative responses to different  flammable gases at different levels. Hence, with a small molecule gas like methane a pellistor is more sensitive and gives a higher reading than a heavy hydrocarbon like kerosene.

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How best to study cow burps?

We have covered some serious subjects over the past few weeks, so I thought this time I would talk about something a little bit more light-hearted, at least on the face of it.

Back in January of this year, there were reports from Germany of an explosion – a herd of cows nearly took the roof off their barn because of the amount of methane they were releasing, when a static electric charge caused it to explode. The blast damaged the roof of the barn and one cow (out of about 90) received minor burns.

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