Biogas Upgradation Methods

Upgradation of biogas is primarily achieved by carbon dioxide removal which then enhances the energy value of the gas to give longer, driving distances with a fixed gas storage volume. Removal of carbon dioxide also provides a consistent gas quality with respect to energy value. The latter is regarded to be of great importance from the vehicle manufacturers in order to reach low emissions of nitrogen oxide.

At present four different methods are commercially used for removal of carbon dioxide from biogas, either to reach vehicle fuel standard or to reach natural gas quality for injection to the natural gas grid. These methods are:

  • Water absorption
  • Polyethylene glycol absorption
  • Carbon molecular sieves
  • Membrane separation

Water Scrubbing

Water scrubbing is used to remove carbon dioxide but also hydrogen sulphide from biogas since these gases is more soluble in water than methane. The absorption process is purely physical. Usually the biogas is pressurized and fed to the bottom of a packed column where water is fed on the top and so the absorption process is operated counter-currently.

Polyethylene Glycol Scrubbing

Polyethylene glycol scrubbing is a physical absorption process. Selexol is one of the trade names used for a solvent. In this solvent, like in water, both carbon dioxide and hydrogen sulphide are more soluble than methane.

The big difference between water and Selexol is that carbon dioxide and hydrogen sulphide are more soluble in Selexol which results in a lower solvent demand and reduced pumping. In addition, water and halogenated hydrocarbons (contaminants in biogas from landfills) are removed when scrubbing biogas with Selexol.

Carbon Molecular Sieves

Molecular sieves are excellent products to separate specifically a number of different gaseous compounds in biogas. Thereby the molecules are usually loosely adsorbed in the cavities of the carbon sieve but not irreversibly bound. The selectivity of adsorption is achieved by different mesh sizes and/or application of different gas pressures.

When the pressure is released the compounds extracted from the biogas are desorbed. The process is therefore often called “pressure swing adsorption” (PSA). To enrich methane from biogas the molecular sieve is applied which is produced from coke rich in pores in the micrometer range. The pores are then further reduced by cracking of the hydrocarbons. In order to reduce the energy consumption for gas compression, a series of vessels are linked together.

Pressure swing adsoprtion process for biogas upgradation

The gas pressure released from one vessel is subsequently used by the others. Usually four vessels in a row are used filled with molecular sieve which removes at the same time CO2 and water vapour.

Membrane Purification

There are two basic systems of biogas purification with membranes: a high pressure gas separation with gas phases on both sides of the membrane, and a low-pressure gas liquid absorption separation where a liquid absorbs the molecules diffusing through the membrane.

  • High pressure gas separation

Pressurized gas (36 bar) is first cleaned over for example an activated carbon bed to remove (halogenated) hydrocarbons and hydrogen sulphide from the raw gas as well as oil vapour from the compressors. The carbon bed is followed by a particle filter and a heater. The raw gas is upgraded in 3 stages to a clean gas with 96 % methane or more.

The waste gas from the first two stages is recycled and the methane can be recovered. The waste gas from stage 3 (and in part of stage 2) is flared or used in a steam boiler as it still contains 10 to 20 % methane.

  • Gas-liquid absorption membranes

Gas-liquid absorption using membranes is a separation technique which was developed for biogas upgrading in the recent past. The essential element is a micro-porous hydrophobic membrane separating the gaseous from the liquid phase. The molecules from the gas stream, flowing in one direction, which are able to diffuse through the membrane will be absorbed on the other side by the liquid flowing in counter current.

The absorption membranes work at approx. atmospheric pressure (1 bar) which allows low-cost construction. The removal of gaseous components is very efficient. At a temperature of 25 to 35°C the H2S concentration in the raw gas of 2 % is reduced to less than 250 ppm.

Synthetic Biology – A Catalyst to Revolutionize Biogas Industry

Essentially a process operating by living organisms, the biogas industry is a natural target for synthetic biology. Synthetic biology combines biology and engineering to design and construct biological devices. Contrary to traditional genetic engineering that only alters an already existing DNA sequence, synthetic biology allows us to build entirely new sequences of DNA and put them to work in cells. This allows us to build novel biological devices that would never exist in nature.

Constructions and operations of devices that do not exist in nature, such as tools, vehicles, computers and the internet, have crafted modern civilization. Now, it is synthetic biology that is challenging nature’s limitations and advancing civilization to a higher level.

Generating biogas via anaerobic digestion of biomass and organic waste is one of the few proven, cost-effective, scalable biomass energy strategies. Biogas consists of mainly methane and carbon dioxide, and combustion of methane with air generates energy which can be used for many purposes such as cooking, heating, producing electricity and vehicle fuel. As a result, countless biogas plants are operating around the globe helping to clean up waste and generate energy. With more plants being built, they come in all sizes ranging from household to factory scales.

Anaerobic digestion is a process where extremely complex microbial communities degrade organic matter, such as sugars, fats and proteins, resulting in biogas as the primary end-product. Such inherent complexity makes this process very difficult to optimize. Mechanical engineers have made tremendous progress to optimize this process, but in many places it still requires government subsidies to be profitable.

Synthetic Biology and Biogas Industry

Essentially a process operating by living organisms, the biogas industry is a natural target for synthetic biology. In terms of their genetic content, organisms are classified into three natural groups, Archaea, Bacteria and Eukarya. Most microbes are Archaea and Bacteria, while humans are Eukarya.

In an anaerobic digester, many different types of Bacteria convert the complex organic matter in waste or biomass to hydrogen gas, carbon dioxide, formate and acetate. A unique group of methanogenic Archaea then produces the invaluable part of biogas, methane, by eating hydrogen and carbon dioxide, formate or acetate.

One can imagine creating a super microbe to convert the complex organic matter directly into biogas, thus making anaerobic digestion faster, more efficient and easier-to-manipulate. Making a synthetic microbial community by reprogramming key microbes may also help them work together when a tough job (i.e., eating extremely complex waste) needs to be done.

Among numerous microbes in anaerobic digester, methanogenic Archaea are one of a few microbial groups that have been extensively studied, and a number of genetic tools are available for engineering via synthetic biology. Therefore, scientists have begun to reprogram methanogenic archaea, allowing them to eat organic matter such as sugars and directly produce methane. If they succeed, they may engineer a super microbe that never existed in nature and revolutionize the biogas industry by making anaerobic digestion much simpler and more efficient.

There is also the possibility of more applications downstream. For instance, upgrading biogas by removal of carbon dioxide improves its combustibility. A super microbe could be made to upgrade biogas using hydrogen gas or even electricity to form more methane from carbon dioxide.

Conceptualized super cell that converts idealized organic matter (2CH2O) directly into biogas.

Grand Challenges

However promising, grand challenges remain when it comes to applying synthetic biology to the biogas industry. About 10,000 moving parts are needed to make an automobile, millions of parts for an airplane, and all the parts are standardized.

Similar to those engineering sectors, synthetic biology also needs many standardized genetic parts and modules to be able to create biological devices that can really revolutionize an industry. Sophisticated genetic tools are needed as well to assemble these parts and put them to work. However, few such parts, modules and tools are at disposal for engineering microbes in an anaerobic digester.

Take methanogenic Archaea for example, only three parts are available in the iGEM registry, the world largest collection of biological parts for synthetic biology. Another challenge is an apparent neglect of synthetic biology by the biogas industry. Symposiums bringing professionals from biogas industry and synthetic biology together for discussions are rare, as are major investments for promoting synthetic biology.

As a result, few research groups are developing synthetic tools and parts for the biogas industry. For example, the aforementioned three iGEM parts were all contributed by only one group, the UGA-iGEM team at the University of Georgia.

Future Perspectives

Synthetic biology is developing faster than ever, and its cost continues to fall. Thanks to prompt actions of many industrial pioneers in embracing and supporting synthetic biology, it is already starting to revolutionize a few fields.

Synthetic biology also holds great potentials to revolutionize the biogas industry. To achieve this goal, joint efforts between the biogas industry and academia must be made. The former side needs to understand what synthetic biology can achieve, while the latter side should identify which parts of the process in the biogas industry can be re-designed and optimized by synthetic biology.

Once the two sides start to work together, novel synthetic parts and tools are bound to be invented, and they will make anaerobic digestion a better process for the biogas industry.

Air Genius: An Indoor Air Quality Monitor With a Difference

Indoor Air Quality (IAQ) refers to the air quality within and around buildings and structures, especially as it relates to the health and comfort of building occupants. Understanding and controlling common pollutants indoors can help reduce your risk of indoor health concerns. Health effects from indoor air pollutants may be experienced soon after exposure or, possibly, years later.

Immediate Health Effects

Some health effects may show up shortly after a single exposure or repeated exposures to a pollutant. These include irritation of the eyes, nose, and throat, headaches, dizziness, and fatigue. Such immediate effects are usually short-term and treatable.

Sometimes the treatment is simply eliminating the person’s exposure to the source of the pollution, if it can be identified. Soon after exposure to some indoor air pollutants, symptoms of some diseases such as asthma may show up, be aggravated or worsened.

The likelihood of immediate reactions to indoor air pollutants depends on several factors including age and preexisting medical conditions. In some cases, whether a person reacts to a pollutant depends on individual sensitivity, which varies tremendously from person to person. Some people can become sensitized to biological or chemical pollutants after repeated or high level exposures.

In long-term effects, Other health effects may show up either years after exposure has occurred or only after long or repeated periods of exposure. These effects, which include some respiratory diseases, heart disease and cancer, can be severely debilitating or fatal. It is prudent to try to improve the indoor air quality in your home even if symptoms are not noticeable.

Factors Behind Poor IAQ

Gas and respirable particulates in the air are the primary sources that contribute to poor IAQ. Sources can include inadequate ventilation, poorly maintained HVAC systems, cooking stoves, non-vented gas heaters, tobacco smoke, vehicle exhaust emissions, building materials, carpeting, furniture, maintenance products, solvents, cleaning supplies etc.

The actual concentrations of these pollutants can also be amplified by other external factors including poor ventilation, humidity, and temperature.

Air Genius – Best Indoor Air Quality Monitor

Air Genius is a state-of-the-art indoor air quality monitor that you should have at your house or in your office to monitor the air that we breathe. The device, developed by India-based Next Sense Technologies, uses the latest sensors to determine particulate matter, VOCs, total volatile organic compounds (TVOCs), carbon dioxide, temperature, humidity and other important parameters.

We have taken a leap in technological advancement by relaying the data automatically to the server so that you can access the data remotely and in real-time. Through this, one could take initiatives on switching on the Air purifier or by keeping the window open for allowing the fresh air.

Typical Applications for Air Genius Indoor Air Quality Monitor

  • IAQ complaint investigation and analysis
  • HVAC system performance monitoring
  • Air quality engineering analysis
  • Mold investigation and remediation
  • Health and comfort assessment
  • Airport lounges, shopping malls, offices
  • Colleges, schools and kindergartens
  • Hospitals and healthcare establishments

For business enquiries about Air Genius Air Quality Monitor, please visit or contact Mr. Mohammad Hamza on +91-9540990415 or email on or

Obstacles in Implementation of Waste-to-Energy

The biggest obstacle to the implementation of Waste-to-Energy (or WTE) lies not in the technology itself but in the acceptance of citizens. Citizens who are environmentally minded but lack awareness of the current status of waste-to-energy bring up concerns of environmental justice and organize around this. They view WTE as ‘dumping’ of pollutants on lower strata of society and their emotional critique rooted in the hope for environmental justice tends to move democracy.

An advocate of public understanding of science, Shawn Lawrence Otto regrets that the facts are not able to hold the same sway. Some US liberal groups such as the Center for American Progress are beginning to realize that the times and science have changed. It will take more consensus on the science and the go ahead from environmental groups before the conversation moves forward, seemingly improbable but not without precedent.

Spittelau Waste-to-Energy Plant

The Spittelau waste-to-energy plant is an example of opposition coming together in consensus over WTE. It was built in Vienna in 1971 with the purpose of addressing district heating and waste management issues. Much later awareness of the risks of dioxins emitted by such plants grew and the people’s faith in the technology was called into question. It also became a political issue whereby opposition parties challenged the mayor on the suitability of the plant. The economic interests of landfill owners also lay in the shutting down of the WTE facility. The alternative was to retrofit the same plant with advanced technology that would remove the dioxins through Selective Catalytic Reduction (SCR).

Through public discussions it appeared that the majority of the people were against the plant altogether though thorough studies by informed researchers showed that the science backs WTE. The mayor, Helmut Zilk eventually consulted Green Party members on how to make this technology better perceived in the eyes of the people, and asked the famous Austrian artist Freidensreich Hundertwasser, who was a green party member to design the look of the plant. Freidensreich Hundertwasser after carefully studying the subject wrote a letter of support, stating his belief as to why WTE was needed and accepted Mayor Helmut Zilk’s request. Later public opinion polls showed that there were a majority of people who were either in favor of or not opinionated about the plant, with only 3% in outright opposition of the plant.

Polarized Discussion

Waste-to-Energy or recycling has kept public discourse from questioning whether there may not be intermediate or case specific solutions. This polarization serves to move the conversation nowhere. For now it can be agreed that landfills are devastating in their contribution to Climate Change and must be done away with. The choice then, of treatment processes for municipal solid waste are plentiful. If after recovery of recyclable materials there remains a sizeable waste stream the option of waste-to-energy can be explored.

Primary Considerations

  • Environmental implications (i.e. CO2 emissions vis-à-vis the next best fuel source) given the composition of the local waste stream. If the waste stream consists of a high percentage of recyclables the more sustainable waste strategy would be to ramp up recycling efforts rather than to adopt WTE,
  • Likely composition and variation of the waste stream and the feasibility of the technology to handle such a waste stream,
  • Financial considerations with regards to the revenue stream from the WTE facility and its long term viability,
  • Efforts at making citizens aware of the high standards achieved by this technology in order to secure their approval.

Note: This excerpt is being published with the permission of our collaborative partner Be Waste Wise. The original excerpt and its video recording can be found at this link

What is Algaculture

High oil prices, competing demands between foods and other biofuel sources, and the world food crisis, have ignited interest in algaculture (farming algae) for making vegetable oil, biodiesel, bioethanol, biogasoline, biomethanol, biobutanol and other biofuels, using land that is not suitable for agriculture. Algae holds enormous potential to provide a non-food, high-yield, non-arable land use source of biodiesel, ethanol and hydrogen fuels. Microalgae are the fastest growing photosynthesizing organism capable of completing an entire growing cycle every few days. Up to 50% of algae’s weight is comprised of oil, compared with, for example, oil palm which yields just about 20% of its weight in oil.

Algaculture (farming of algae) can be a route to making vegetable oils, biodiesel, bioethanol and other biofuels. Microalgae are one-celled, photosynthetic microorganisms that are abundant in fresh water, brackish water, and marine environments everywhere on earth. The potential for commercial algae production is expected to come from growth in translucent tubes or containers called photo bioreactors or open ocean algae bloom harvesting. The other advantages of algal systems include:

  • carbon capture from smokestacks to increase algae growth rates
  • processing of algae biomass through gasification to create syngas
  • growing carbohydrate rich algae strains for cellulosic ethanol
  • using waste streams from municipalities as water sources

Algae have certain qualities that make the organism an attractive option for biodiesel production. Unlike corn-based biodiesel which competes with food crops for land resources, algae-based production methods, such as algae ponds or photobioreactors, would “complement, rather than compete” with other biomass-based fuels. Unlike corn or other biodiesel crops, algae do not require significant inputs of carbon intensive fertilizers.  Some algae species can even grow in waters that contain a large amount of salt, which means that algae-based fuel production need not place a large burden on freshwater supplies.

Several companies and government agencies are funding efforts to reduce capital and operating costs and make algae fuel production commercially viable. Companies such as Sapphire Energy and Bio Solar Cellsare using genetic engineering to make algae fuel production more efficient. According to Klein Lankhorst of Bio Solar Cells, genetic engineering could vastly improve algae fuel efficiency as algae can be modified to only build short carbon chains instead of long chains of carbohydrates.

Sapphire Energy also uses chemically induced mutations to produce algae suitable for use as a crop. Some commercial interests into large-scale algal-cultivation systems are looking to tie in to existing infrastructures, such as cement factories, coal power plants, or sewage treatment facilities. This approach changes wastes into resources to provide the raw materials, CO2 and nutrients, for the system.