The objective of this project is to convert carbon dioxide into methane using E Coli. As the conversion is complete, methane can be stored until it is applied in other industries.
Methane is a colourless and odourless gas. It is also the simplest member of the alkane series.1 Methane is the major component of natural gas, accounting for about 90% of moles.2
Like carbon dioxide, methane is a greenhouse gas, meaning that it traps heat in the atmosphere.3 Its heat-trapping power is much higher than that of carbon dioxide, trapping 72 more times heat than carbon dioxide does in a 20-year period.4
Despite being seen as a big threat to global warming, methane has a lot of uses, and can bring benefits if used correctly.
Uses of methane
- Electricity generation
- Domestic uses
- Industrial uses
Methane can be burnt to generate electricity and energy, which can be supplied to businesses and households.5 Currently, a third of the electricity generated for the United States uses natural gas as fuel, which is the same as the amount generated using coal as fuel.6 The energy released from burning the fuel can be used to power turbines which generates electricity.7
Some families use electricity generated from methane as a source of power and heat. It is also possible to use methane or methane natural gas directly for cooking or heating,8 in gas cookers and central heating systems.9
Methane is a raw material for many other industrial processes and its products are often useful for manufacturing of other products. Under high temperatures, methane reacts with steam to give out carbon monoxide and hydrogen, and hydrogen can be used to manufacture ammonia which can be further applied into the production of fertilizers.10 Methane also reacts with halogens such as chlorine. The products are also widely used in industry, including paint removers and production of silicone resins.11 Decomposition of methane also gives carbon black,12 which can be used as a pigment or a reinforcing filler.13 In the form of natural gas, methane is also an ingredient for plastic, fabric and anti-freeze.14
Energy from the combustion of methane helps some businesses, such as food processors and petroleum refineries, to dehumidify, dry, melt and sanitize their products.15
Methane is a naturally-occurring substance. Anaerobic decomposition of vegetable matter by bacteria produces methane, a phenomenon commonly found in wetlands.16 Some organisms, such as ruminant livestock like cattle and sheep,17 and ocean microbes,18 are also known to produce methane from their biological processes. Manure and wastewater also contribute to emission of methane.19 Methane can also be found in landfill gas from the decomposition of municipal solid waste.20 Methane from these sources can be captured, processed and used as an energy source.21 Digesters are other devices that can be used to extract methane from its sources.22 Natural gas, formed from animal and plant remains from hundreds of millions years ago under heat and pressure, mainly consists of methane.23 After removing impurities and other hydrocarbons, methane that is almost pure is obtained.24
Disadvantages of traditional methods
Traditional methods mostly involve extracting methane from their sources, such as from manure or natural gas. The refining process may take several steps and require more facilities and energy. For example, in the extraction of methane from natural gas, multiple steps are required to remove impurities such as oil and condensate, and to separate other useful natural gas liquids.25 These processes often required large and specialized facilities, and the refining process takes time to complete. Current techniques also include purifying collected gas. Take landfill gas as an example. In addition to the multiple-step removal of impurities, large collection facilities are needed to collect landfill gas in the first place. The costs of construction and operation add up to a large sum of money.
Obtaining methane from manure faces the problem of an unstable supply. A type of bacteria crucial for methane to form from manure, the methane bacteria, can only survive under very specific conditions and is easily toxified by the presence of salts, ammonia or heavy metals.26 As digesters convert nitrogen in manure to ammonia, there is a risk of toxifying the methane formers and thus stopping the reaction.27 Also, the efficiency of these system is relatively low, as not all of the manure will be decomposed into methane. Depending on the type of manure used, different amounts of methane can be digested. The resultant product is also a mixture of methane, carbon dioxide and some other gases,28 which means refining processes are needed if pure methane is wished to be obtained.
Advantages of using the proposed system
The proposed system does not require extreme reaction conditions such as high temperatures and pressures. E. coli grows and survives well under typical conditions, with its optimum temperature of growth being 37°C.29 This means that if the system were to be used, it would not require extra costs or facilities to maintain an optimal reaction condition, which is favourable for small-scale applications such as individual corporations.
E. coli is a fast-reproducing bacteria, dividing once every 30 minutes under suitable conditions.30 With a large population of E. coli present, the rate of methane production is high. High methane production rates can ensure a stable and sufficient supply of methane, which can be directly used in industrial processes or electricity generation. This allows the system to be applied in businesses where a constant supply of methane or energy is needed.
The proposed system is also simple compared to other systems used to obtain methane. No large scale collection facilities are needed and methane can be directly obtained from a chamber containing the E. coli and carbon dioxide. The gas obtained can be transported to a storage tank immediately without having to go through facilities for purification. This allows a more efficient collection system where methane can be obtained more quickly once it is produced.
Since the only product of the proposed process is methane, refinement of the obtained product is not needed, unlike some processes which require the extraction of methane from the product. This makes the production process more efficient than some other systems. The production of pure methane from the proposed system also makes it more effective than system which rely on sources that only partly contain methane. Without the production of undesired products, the efficiency of the system increases.
Implications of using E. coli in conversion of carbon dioxide to methane
As discussed above, our system produces methane more efficiently as its agent is a fast-reproducing bacteria. Without the need of extreme reaction conditions or uncommon catalysts, this system can be widely applied in different situations. Moreover, the E. coli and methane can be stored in tanks, which makes the system easy and possible for smaller businesses to use.
Easy storage and production of methane leads to a wider use of it, which greatly changes the society.Changes in living habits
More production of methane leads to an alternative solution in fuel source for electricity generation. Instead of burning coal or natural gas to generate electricity, methane can be used. Mass production of methane leads to a drop in its prices. This encourages people who are still using coal or other fossil fuels as an energy source to convert to using methane as their fuel.
The increased availability of methane also encourages the public to convert to using methane as fuel in their daily lives. An example would be the fuel of vehicles. If the vehicle is not powered solely on electricity, it would require fuels to some extent. Using the proposed system, methane can be easily produced and can be used as car fuel. With mass production of the gas, its costs can be lowered and it can become a more popular choice of fuel. As methane produces less pollutants during combustion when compared to currently used fuels such as diesel oil, this also encourages people to adopt a cleaner lifestyle and to use cleaner fuels.Electricity generation in rural areas
Currently, about 1.5 billion people do not have access to a stable electricity source,31 which may be due to reasons like the high cost of extending the power grid.32 Under these situations, small-scale off-grid electricity generation is needed.
There have been projects aimed at installing small-scale electricity generators in rural areas using sources like biomass as fuel,33 or using other renewable energy sources such as solar energy, wind energy and hydroelectric power.34
While they are renewable energy source desirable for the sustainability for the environment, they all have individual problems. The most important of which is that all of the above energy sources rely on favourable external conditions, such as having enough sunlight or enough biomass fuel. Without a stable fuel or energy source, electricity generation will be unstable and people might not get a constant electricity supply. The proposed system, however, does not rely on such environmental conditions. As long as a supply of carbon dioxide is given to the E. coli and a place is provided for the E. coli to perform the conversion, a steady supply of methane can be produced and converted into electrical energy regardless of undesirable weather conditions or an inadequate amount of fuel.
Another disadvantage of currently used systems is that they required sufficient spacing and specific geographical characteristics. Take hydroelectric power as an example. The choice of location is narrow as many rural areas do not have access to rivers or a water source.35 For wind power, it is also difficult to find a location in which building a turbine farm is sufficient as not many places have strong enough winds blowing there.36 The proposed system, however, is not limited by geographical location. Since it does not rely on the environment, it can be implemented in any location as long as there is space for a tank of E. coli and a place to burn the methane they produce. Moreover, the proposed system does not take up a lot of space since the size of E. coli is small and can be contained in a relatively small container. No extra steps are required to obtain pure methane and thus the whole setup will not take up much space. This is especially advantageous in rural areas where small-scale electricity generators are needed. A small system can be easily installed in these areas where large-scale infrastructure are often impossible due to geographical constrictions. The system can also be adjusted to supply different amounts of energy, depending on the size of the area and its demand, by supplying different amounts of E. coli and carbon dioxide. As mentioned above, the production process is not easily affected. This ensures a rate of energy production that meets its demand, and is also stable at the same time.
Many current systems require high initial costs or high maintenance costs, which may become a financial burden to those living in rural areas, especially when they do not have high incomes to support such costly infrastructures. The proposed system does not involve specialized equipment that require precise and highly technical parts, nor does it involve moving parts which require frequent replacement. The E. coli are able to reproduce so it is unnecessary to frequently replace them. The system is long-lasting since it runs on a rather simple setup. The operational cost of our system is thus lower and more affordable for those using them. Maintenance is also made simple because no specialized parts have to be transported through the rural areas which may pose as a difficulty for some communities.37
The proposed system takes advantage of E. coli being able to survive in different conditions and its easy storage to create a small-scaled system that can be applied to areas of different geographical characteristics. The simple system allows it to run on a relatively low cost without complicated pieces of equipment needed. It is advantageous to rural areas which do not have developed economic and social system as it operates on a low cost and does not require high-skilled technologies. The system can be applied to rural areas where current electricity generation systems could not reach.
Methane can be used in the production of many products. With the proposed system in use, methane production can be greatly increased. Not only can methane manufacturers produce more methane that can be sold, some businesses may also be able to manufacture their own methane.
For electricity generators, they can make use of their own methane as a fuel for combustion. This eliminates the need to drill underground for extraction of fuels. They can own a storage tank with the bacteria and feed it carbon dioxide to produce methane. It does not require specific equipment and can be maintained rather easily, unlike drills that often need repairs. The whole processes can be done within the company itself, which also reduces the need of importing fuel sources. Overall, the cost of generating electricity is lowered as the cost of obtaining fuel and maintenance have decreased. Once their operating costs have decreased, they can gain more profit from the business. If they were to keep original electricity prices, their profits will increase as their costs have decreased. If electricity prices were cut, it increases their attractiveness to customers, whom more of which may purchase electricity from these businesses. As more people make use of electricity, their market will increase in size and profitability will also increase.
For methane manufacturers, making use of the system eliminates the need of extracting methane from large areas or producing it using chemical reactions. Since methane is directly produced and extracted from the tank containing E. coli, which is a small area compared to large fields where methane is currently taken from, the efficiency of obtaining methane increases. They can also reduce time of production since no purifying processes are needed. Conditions needed for E. coli to perform the conversion are also not difficult to maintain. No extreme pressure or temperature, or catalysts are needed. These factors combined reduces the operation cost of the manufacturers. Once again, they may gain profit by selling methane at a low price as it increases the business’ competitiveness in the market. This creates more opportunities for the company to do businesses with methane users.
There is also a possibility that some businesses may be able use the system to produce methane on their own. Producers who use methane as a raw material in their processes can install the system which supplies methane directly to their reaction chambers without having to purchase the gas. The tank containing E. coli can be connected to the reaction chamber and methane produced from the conversion can be used immediately. This simplifies their production process as there are no more concerns on transportation of the purchased methane. As the system is self-sustainable and E. coli will further divide over time, maintenance costs for the system is also low since it is unnecessary to often replace parts of the system, which reduces their operation costs. With a lower cost, they are able to manufacture more products and to sell them at lower prices. This attracts more customers who are interested in buying methane-produced products. Business opportunities are created for these businesses.Environmental considerations
With our system, a constant supply of methane can be obtained without having to extract it from underground non-renewable sources. This reduces the risks of accidents related to mining. Methane, which is flammable, is often found in coal mines. Coal mine methane may lead to serious explosions, which is why safety precautions taken by miners often include expelling methane gas into air through ventilation to lower its concentration in the mine.38 With the proposed plan, methane can be obtained on the surface. This eliminates the need of going underground and having to deal with coal mine methane. Without having to drill, undesired release of methane to the atmosphere can be avoided.
Another way the proposed system benefits the environment is that less pollutants are released when methane is burnt. Combustion of methane produces less carbon dioxide than various common fuels, such as coal and diesel oil.39 This is because methane has a high carbon dioxide-to-energy content and it does not contain impurities such as water and sulphur which lowers this content.40 The system converts carbon dioxide into methane directly, where no other substances are formed in the process. This allows the methane produced to maintain a high carbon dioxide-to- energy content. It also prevents formation of other harmful products, such as sulphur dioxide which may be found in the combustion of coal.41
The proposed system is a sustainable plan. The reagents used in the system, E. coli and carbon dioxide, are both renewable. E. coli has a high reproduction rate and divides once every half an hour.42 Unlike fossil fuels which have a limited supply, the E. coli can reproduce while retaining its carbon dioxide converting ability. Carbon dioxide can also be easily obtained from the environment, or from factories that produce the gas during industrial processes. Relative to underground fuel sources, there is a large abundance of carbon dioxide available for use in the conversion. Making use of renewable sources, the proposed system is expected to run for a long time. This ensures a sustainable and stable energy source in the midst of fossil fuel depletion which is expected to occur within the next century.43
In addition to the abundance of raw materials, the conditions in which the system can operate is non-specific. As discussed above, current renewable energy generators rely on environmental conditions, which may vary according to weather or human activities in the area. With unstable environmental conditions, energy supply is unsteady. Some other sources require very specific geographical characteristics in order for the system to work. This does not pose to be a problem in the proposed system. E. coli is known to survive in a wide range of temperatures and also in both aerobic and anaerobic conditions.44 This allows the system to be used in a wide range of conditions. Moreover, the system only includes a simple step of converting carbon dioxide to methane, without having to use energy from the environment. This lifts geographical constrictions and allows the system to be used in many places. Combined with the low emission levels of methane combustion, the proposed system appears to be one that serves to relieve current issues on global warming and can be used on a worldwide scale.
As a whole, the greenhouse gas content in the atmosphere would decrease. Carbon dioxide released into the atmosphere can be captured and used as a raw material for the proposed system. This decreases the carbon dioxide content in the atmosphere. Methane gas which is produced can be collected and sent to different facilities for various uses, such as energy generation or manufacturing of certain products, without releasing it into the atmosphere. As methane gas is used up, the total amount of greenhouse gases in the atmosphere would also decrease. Once applied in a wider scale and more people adopting methane as their energy source, both the amount of greenhouse gases in the atmosphere and the amount released into the atmosphere would decrease.Potential problems and possible solutions
While the proposed system has many benefits, it also comes with some potential problems during its application.
First of all, when the system is applied on a worldwide scale, the demand of power may be underestimated. The world requires energy for many uses, and the methane supply created by the E. coli must be fast enough to keep up with the consumption rate. The methane production rate of E. coli through the proposed system has yet to be known, so there lies a possibility where the bacteria cannot produce methane fast enough to meet the energy demand.
A possible solution to this problem is to transform more E. coli. It is known that E. coli that can convert carbon dioxide into other alkanes have extremely high growth rates, and thus makes mass production of the bacteria easy. Although the actual rate of production of methane is unknown, a larger number of E. coli is guaranteed to be able to convert more carbon dioxide per unit time. Also, E. coli is known to survive for a long time, with their die-off rate significantly higher than other bacteria.45 With a long life-span, each bacterium can produce convert more carbon dioxide to methane in their lifetime. On a macroscopic scale, more E. coli are surviving to produce methane. With the exponential growth of the number of E. coli doing the conversion, it is only a matter of time when the population of E. coli is large enough to produce enough methane to meet energy demands.
The proposed system also poses some risks. As the design of the storage system is not refined, there is a possibility that some methane would escape the system and enter the atmosphere. Improper storage of methane may also lead to leakage of the gas. As mentioned above, methane is a greenhouse gas much stronger than carbon dioxide. If the faulty design is applied to many industries and businesses, the accumulated release of methane into the atmosphere may worsen the greenhouse effect.
This issue cannot be solved at this stage. To lower the risk of leakage of methane, the system must first be built and examined for leakage. Before applying it on a large scale and in different industries, the system can be tested for potential problems. Detectors can be put around the tank containing the E. coli to monitor methane levels. If leakage is found, the design of the system can be improved to minimize the amount of gas going into the atmosphere. Possible improvements may include enhancing the sealing of the container or adding an outer casing containing chemicals that can convert methane to less harmful substances. Specific measures cannot be said for sure at this stage as further experiments and analysis is needed.1 https://www.britannica.com/science/methane