E- FUELS : ELECTRICITY-


GENERATED FUELS, THE NEXT BASTION OF RENEWABLE ENERGY THAT MAY HELP POWER OUR FUTURE


Carbon emissions have plagued our planet to a point where a change is required to reverse any adverse effects on the environment. Global temperatures are rising at an alarming rate of over 20


C a year. The impending climate disaster is the


reason why the search for sustainable fuels has become a focal point in the fuel industry. The design and development of innovative electricity-generated fuels (e-fuels) have led to promising results of a product fuel that has a net-zero carbon footprint. The basis of e-fuel production is to convert electricity to hydrogen gas (H2 of carbon dioxide gas (CO2


), to both react together and form an e-fuel. The reaction between the CO2 synthetic e-fuels.


e-fuel product is comparable to the performance and cost of traditional petroleum-based fuels. Focusing on the synthesis of methanol through a sequence of reactions is explored throughout this paper.


Figure 1. Schematic of a typical e-fuel process [2]


The process of the creation of a methanol-based fuel will be discussed as a potential replacement for the traditional petroleum- based fuel. In addition, the benefi ts of e-fuels will be highlighted to further prove why this swap is necessary. The future scope is bright as the use of e-fuels can steer the way for a cleaner and more renewable future.


E-fuels have been revolutionary in the continuous search for a sustainable clean fuel source. Experts have experimented with many different processes in an attempt to fi nd the most effi cient process, fi nancially and energy-wise, to output the best product. The use of renewable electricity as the dominant source of energy and the main raw material used in the production of water and carbon dioxide is a commonality in the majority of e-fuel processes. Each different e-fuel, formulated from different processes, has its own unique features that can be specifi cally helpful for certain applications. Many different reactions have been experimented with to produce e-fuels. Some of the resulting e-fuels from various methods used include hydrogen, methane, methanol, dimethyl ether (DME), Fischer-Tropsch synthetic fuel products, oxymethylene ethers (OME), and mixtures of dimethylcarbonate and methylformiate [3]. While many of these methods have proven to be successful, some have exceeded expectations and the resulting


IET MARCH / APRIL 2022


In the earliest stage of formulating an e-fuel, hydrogen gas must be produced. The common and reliable method of hydro electrolysis is a clean and effective way of obtaining hydrogen gas. The reaction takes place in an electrolyzer which consists of an anode and a cathode separated by an electrolyte. When water is introduced to the system, it reacts at the anode to form oxygen and positively charged hydrogen ions. The electrons fl ow through an


external circuit and the hydrogen ions selectively move across the polymer electrolyte membrane to the cathode where the hydrogen ions combine with electrons from the external circuit to form hydrogen gas [4]. The visual representation of this process and the reaction equations can be viewed in Figure 2.


Now that hydrogen gas has been obtained, it must be reacted with a carbon compound to be used as a fuel base. To further improve environmental conditions, carbon dioxide is captured and reused in the e-fuel production process as the required carbon compound. Excess CO2


can be obtained from injected CO2 geological storage


locations including coal beds, deep saline formations, shale formations, or oil and gas reservoirs [5] but, to further improve environmental conditions the excess CO2


from processes such as


recycling or biomass gasifi cation is captured by an energy storage technique/system and used to formulate an e-fuel [6]. One of the most prevalent carbon capture methods utilized in the production of an e-fuel is physical separation of the CO2


. Physical adsorption


or absorption is the principal of this process. This can be done by a solid surface, such as metallic oxides, adsorbing the CO2


gas


or via a liquid solvent (typically Selexol or Rectisol) to absorb the CO2


gas [7]. The CO2 gaseous form can be released at a later time Figure 2. Typical electrolyzer


by increasing temperature or pressure from the adsorbent. In addition to physical separation, a newer carbon capture technique performed to be used in the production of synthetic e-fuels is direct air capture (DAC). The DAC process starts with an air contactor where a large fan pulls air into the system. Once the air has entered the system it’ll pass over thin plastic surfaces that have a non-toxic solution of potassium hydroxide fl owing over them. The CO2


molecules chemically bind with the solution, removing


them from the air and trapping them in the liquid solution as a carbonate salt [8]. To release a concentrated CO2


gas, to be


further utilized, the gas must fi rst be separated from the salt out from the solution. The subsequent reaction, in a pellet reactor, yields a precipitate that then gets passed through a calciner. The precipitated pellets are heated in the calciner (renewable sources such as hydroelectric, wind, or solar energy can be used to power the calciner) to obtain our desired CO2


calciner reaction concludes the pellets are recycled back into the system to reproduce the original capture chemical [8]. The DAC process is continued to be researched as there are some concerns with the amounts of energy it takes to heat the reaction that separates the CO2


commonly utilized and transformed into a product of synthetic hydrocarbon gases like methane (CH4 liquid form alcohol fuels like methanol (CH3


) or butane, or in OH) [1]. Figure 1 presents a visual of the processes necessary to produce these


) and use captured carbon, in the form and H2


gases is most


in pure gas form. After the


gas. It is critical to note that by utilizing either of


these methods maintains net-zero carbon emissions. The particular alternative fuel source of methanol has been studied


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