Biofuels: A Possible New Renewable Energy Source

By Erik Heitsmith

Within a heavily industrialized society--as seen currently all over the earth--energy is quite literally what makes the world revolve. Whether running our own human internal batteries or powering massive production lines, energy has a prolific presence on our planet. Specifically as a result of this aforementioned ‘industrial society’, there has been a growing need for external power sources. Beginning with the start of the industrial revolution, the supply has been sourced from coal, gasoline, and natural gas due to their relatively easy access and ability to burn long and efficiently (U.S. Energy Information Agency (EIA), 2013). In recent years, however, there has been a greater acknowledgment of the negative environmental impacts of these abundant fuels. Thus, there has been a call for a fuel source that is truly renewable. One of the many proposed sources to gain prevalence in the modern energy portfolio is biofuels, such as corn ethanol and biodiesel.

As the name suggests, biofuels are directly manufactured from biological matter, mainly agricultural plant materials (U.S. Department of Energy (DOE), 2019). Therefore, as long as there is land to grow the crops necessary as well as appropriate amounts of sun and rain, there is no limiting factor for the input material of biofuel production. Compared to other fuels, for example coal, the useful life of biofuels is not restricted to a natural deposit; humans can simply grow more plants to produce more biofuels (Environmental Protection Agency (EPA), 2019). In this very simple sense, biofuels appear to be completely renewable. However, like most new proposals for renewable energy, there must be a deeper analysis of the true impacts and limitations.

To provide a brief history of biofuel use in society, humans have been burning organic matter to generate since fire has been discovered by man. Early on in the development of the human race, wood was the main energy-generating source used to do anything from heat homes to cook food. However, it wasn’t until recent years and technological advancement that the energy producing components of biological matter were harvested to an increased degree. Once grown, the maximum fuel potential of biofuel crops is not yet readily available; they must undergo various processes by which liquid fuels are extracted (DOE, 2019). Due to the liquid biofuel’s ability to burn much more efficiently, generating more energy compared to their solid form, the term ‘biofuel’ mainly refers to the liquid form to spare a large category of ambiguous energy sources (Somerville, 2007). The first widespread commercial use of liquid biofuels was in the early twentieth century, with the invention of cars. Many original-model automotive engines ran solely on biofuels such as peanut and hemp oils (Biofuel UK, 2010). During this time period, however, more of an emphasis was placed upon non-renewable fuel sources (specifically crude oil), as they were generally easier to harvest and produce commercially. Recently, greater awareness has been placed upon the potential for biofuel consumption as unsustainable energy deposits become exhausted and environmental concern mounts. Thus, biofuels have the possibility of re-entering the sphere of global energy consumption, depending on their true impact on the environment.

As of today, there are two main types of biofuels that are manufactured for public access: ethanol and biodiesel. Currently, the main application of power derived from biomatter is in cars. It is not common, however, for an ordinary citizen to own a vehicle that runs solely on either type of burnable energy. Rather, to increase the efficiency and safety of the combustion reaction of fossil fuels, ethanol is currently used as an additive to commercial gasoline. Usually, the two substances are combined in a 9:1 gasoline to ethanol ratio (EIA, 2020). When this ratio becomes heavier on the biofuel end, special “flexible-fuel” cars and sometimes specific climates are required to burn the ethanol-heavy mixture. With an ever-evolving technological society, however, advancement is possible for functional ethanol engines. Biodiesel, consisting mainly of vegetable oils, can be combusted directly in the regular diesel engine (EIA, 2020). In theory, a car with a diesel engine can run solely on spare oil sourced from restaurants.

To understand the true benefits and limitations to widespread biofuel use, first the methods by which they are processed must be understood in depth. Due to the fact that the steps involving the preparation of liquid biofuels from solids contain chemical processes, the potential for harmful gaseous molecules to be released into the atmosphere as byproducts is more than possible. According to the U.S. Department of Energy, the first broad step of the conversion of biological matter into usable liquid biofuels is called ‘deconstruction’, where the plant cell wall is broken down for easier access to energy-rich sugars. Within deconstruction, there are two more broad methods each containing different ways of breaking down the cell wall of biofuel crops: high-temperature deconstruction and low-temperature deconstruction.

The term ‘high-temperature deconstruction’ for producing biofuels from biological matter is fitting, as high levels of heat are required to complete these processes. The three major specific methods that fit under the high-temperature deconstruction umbrella are known as pyrolysis, gasification, and hydrothermal liquefaction. In pyrolysis the biofuel crop is heated to temperatures of 500-700ºC rapidly in an anoxic environment, breaking the matter down into a mixture of vapor, gas, and char. Ultimately, the char is removed and the resulting sample is condensed to an oil (DOE, 2019). Gasification is similar in nature to pyrolysis, rather, the biomass is heated in a slightly oxic environment and to temperatures greater than 700ºC. The resulting product is a highly flammable gaseous mixture of carbon monoxide and hydrogen known as synthesis gas (syngas), which can be directly used for energy (DOE, 2019). The hydrothermal liquefaction process is used primarily when the biological matter being used to manufacture biofuels considered to be wet. The biomass is heated to 200-350ºC at high pressures, where the moisture nears its critical point, greatly increasing the reaction rate for the breakdown of the plant cell wall, ultimately producing oil (Zhang, 2018). To a general degree, each of these three methods accomplish the goal of producing a biocrude fuel source.

Low-temperature deconstruction of biological matter occurs under normal temperature conditions, not in the cold as the name may otherwise suggest. Rather than heat being the drive for increasing the rate at which the cell wall of biomass is broken down, there are certain enzymes (complex chemical structures) that act similarly. Before enzymatic action, the biomass first undergoes a pretreatment to allow for more effective access to the sugars within the cell wall. Then, with a process commonly known as hydrolysis, these complex sugars are broken down by the enzymes into simpler fuel-rich sugars such as cellulose (DOE, 2019). At this point, the biocrude can progress towards the second step of biofuel preparation.

The second and final step of biofuel production is given the general umbrella term of “upgrading”. The goal in this step is to eliminate any unwanted reactive chemicals remaining in the sample, to improve handling quality and storage (DOE, 2019). As with deconstruction, there are multiple methods that can be employed when upgrading a biocrude fuel. The sub-method taken is dependent on the previous step taken to convert the biofuel; that is, one type of pre-fuel produced in the first step may be upgraded differently from a different kind of pre-fuel. Overall, there are two primary biological and chemical categories for upgrading. Fermentation is one method, in which certain biological microorganisms separate the valuable fuel from the unwanted compounds. It is primarily employed for sugars and gaseous products that are produced. The other common approach to upgrade biocrude is through chemical catalysts, which is useful for oils, syngas, and sugars (DOE, 2019). After upgrading, the biofuel production is complete and can be readily accessed by the public.

Much of the fault in biofuel production lies within the need for external fuel, which can potentially be sourced from a non-renewable feedstock. To deeply criticize the comprehensive manufacturing process, the first possible source of error with the release of carbon dioxide is the planting and harvesting of crops. If agricultural machinery is used, there is energy being consumed that has the possibility of not being clean. In addition, the application of fertilizers for crops releases other nitrogen-based greenhouse gases, such as nitrous oxide (EPA, 2019). At some point there must also be energy consumed in the transportation to and from a processing facility. After the raw biomatter is harvested and transported, there is an even larger call for energy consumption as a result of the conversion processes previously detailed. In biomass deconstruction-especially the high temperature options-incredibly large amounts of energy are required to heat the sample to the necessary temperature, depending on the specific process. Research has not yet been completely finalized, but there are field theories that emissions of greenhouse gases from biofuel production may surpass those currently emitted from fossil fuels (EPA, 2019). These concerning figures are enough to fund further research into the use of biofuels before they are commercially available.

Although there are many valid environmental concerns for commercial use in regards to projected greenhouse gas emissions, many characteristics are working in biofuel’s favor. A valid workaround to the energy consumption during the production of biofuels as in harvesting, transportation, and manufacturing is to only draw power from other renewable sources. At first when establishing facilities, nationally accessible energies such as solar, wind, and hydroelectric can be intermediately used until biofuels can become self-sustaining: eventually providing their own energy. In addition, the issue of excess greenhouse gas emissions as a result of the burning of biofuels has a convenient “sink”-a reservoir that reduces atmospheric concentrations of a substance-from earlier in the process. The crops that are grown to produce biofuels reabsorb large amounts of carbon dioxide previously released. As a result, another model predicts that the use of biofuels could in turn cause a reduction in greenhouse gas output after a thirty-year regeneration phase (EPA, 2019). Essentially, if there is time for this period of carbon consumption by plant matter, the effort placed into biofuels will be worthwhile.

The potential for an increase in biofuel production and consumption all over the world is promising. Despite the fact that there are faults in the system of manufacturing biofuels, there are justifications for the main environmental concerns. As with any other completely new fuel source, convincing the general public of approving the switch to bioenergy will take dedication, patience, and education. There are other concerns regarding biofuels economic-wise, but the current state of the environment strongly suggests that less worry should be placed on fiscal security and more onto saving the one planet that we live on. Once society is convinced to fulfill the thirty-year recovery plan, the future of energy in the form of biofuels will be on the horizon. Doing so will satisfy the current moral obligation of every person: by dedicating to reduce the carbon footprint of the human race and return nature to its previous unaltered state.

References

Biofuel UK. (2010). History of biofuels. Biofuel UK. Retrieved November 15, 2020, from http://biofuel.org.uk/history-of-biofuels.html

Luque, R., Herrero-Davila, L., Campelo, J. M., Clark, J. H., Hidalgo, J. M., Luna, D., ... & Romero, A. A. (2008). Biofuels: a technological perspective. Energy & Environmental Science, 1(5), 542-564.

Somerville, C. (2007). Biofuels. Current biology, 17(4), R115-R119.

Office of Energy Efficiency & Renewable Energy. (2019). Biofuels basics. U.S. Department of Energy. Retrieved November 15, 2020, from https://www.energy.gov/eere/bioenergy/biofuels-basics

U.S. Energy Information Agency. (2013, July 3). Energy sources have changed throughout the history of the United States. Energy Information Agency. Retrieved November 15, 2020, from https://www.eia.gov/todayinenergy/detail.php?id=11951

U.S. Energy Information Agency. (2020, August 24). Biofuels explained: Ethanol and biomass-based diesel. U.S. Energy Information Agency. Retrieved November 19, 2020, from https://www.eia.gov/energyexplained/biofuels/#:~:text=Using%20ethanol%20or%20biodiesel%20reduces,pure%20gasoline%20and%20diesel%20fuel

U.S. Environmental Protection Agency. (2019, November 22). Economics of biofuels. U.S. Environmental Protection Agency. Retrieved November 19, 2020, from https://www.epa.gov/environmental-economics/economics-biofuels

Zhang, Y., & Chen, W.-T. (2018). Hydrothermal liquefaction of protein-containing feedstocks. Science Direct. Retrieved November 17, 2020, from https://www.sciencedirect.com/topics/engineering/hydrothermal-liquefaction