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| Fig. 1: Types of biofuel. (Source: Wikimedia Commons) |
As we seek to elucidate the most efficient ways to meet the demands of global energy needs, it is critical to consider the biofuel sector from an analytical lens that centers concerns about land consumption, as well as how much energy it would actually provide. In the grand scheme, it has been shown that biofuels have a decreasing effect on CO2 emissions as compared to fossil fuels. Of course, with CO2 emission being a vital assessment in any energy source debate, it is also worth seeing how much the use of edible crops as feedstock for biofuel processing competes with the actual production of food. [1] It is also important to focus on the realistic capabilities of energy stores in these crops. Despite the aforementioned potential benefit, the energy production of biofuels would not offset the US energy usage.
We can illustrate the potential of using land for the purposes of biofuel energy by evaluating the the amount of energy produced by the dry mass of a crop within a specific region. It is particularly important to analyze the situation for different crops independently, because of the intricately complex relationships between individual crops' agricultural yield, their demand as a food source, and their varying measures in cost.
For the purposes of this article, we will focus on the corn crop, one of the key crops contributing to the global conversation surrounding biofuels as illustrated Fig. 1. The dry mass of corn as grain, as it is mostly sold, accounts for the amount of the corn potentially available for biofuel. A recent study found that the United States corn grain yield was 11.5 metric tons per hectare in 2021 from around 9.3 × 107 acres of corn. [2] As such we can calculate the total dry mass of corn yield in grain as follows:
| (9.3 × 107 ac × 11.5 tons/ha ) / 2.4 ac/ha | = | 4.46 × 108 tonnes |
| 4.46 × 108 tonnes × 103 kg/tonnes | = | 4.46 × 1011 kg |
From this dry mass total of 4.46 × 1011 kg, the total energy of this dry mass can be calculated by multiplying the mass in kg by 2.3 × 107 Joules, which is roughly the energy retrieved from burning wood (energetically, wood and dried corn plant are virtually equivalent).
| 4.46 × 1011 × 2.3 × 107 J kg-1 | = | 1.03 × 1019 J |
The United States consumes about 9.7 × 1016 BTU y-1 according to the Energy Information Administration. [3] This is about 1 ×1020 J. The 1.03 × 1019 J that would be provided by dry corn would only cover about 10% of this total energy consumption. In fact, this is in the most ideal of cases since the energy needed to farm and process the crops is not subtracted from the energy output.
The energy production of 1.03 × 1019 Joules proves to be relatively low in comparison to US energy consumption. Even if this value was higher, it is important to wrestle with the fact that the increased demand for the corn dry mass would have an immense effect on the prices of food. In addition, corn grows more dry plant mass per acre than other plants.Hence, the above calculations represents the most amount of energy we could get from any one plant. Even as technologies are developed to alter our understanding of crop maintenance and efficiency, the lack of land availability and adequate dry mass would remain uprooting issues.
The use of land is a necessity for agriculture, and in order to know how much of a crop is needed, one must also account for land requirement. In tandem with this is the consideration of quality land being available that is, having land most suitable for agriculture or even expanding unsuitable lands by using fertilizers and other applications to make more fertile space. Regardless, the initial requirement of having that available land is where the physical basis for using corn for energy falls short.
© Kyle Lambert. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] E. Moioli et al., "Analysis of the Current World Biofuel Production Under a Water-Food-Energy Nexus Perspective," Adv. Water Resour. 121, 22 (2018).
[2] M. Langemeier and L. Zhou, "International Benchmarks for Corn Production," Center for Commercial Agriulture, Purdue University, March 2022.
[3] "Monthly Energy Review, February 2023," U.S. Energy Information Administration, OE/EIA-0035(2023/2), February 2023.
