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Switchgrass is a native perennial grass that has been extensively studied for its potential in biofuel production, being given the designation of 'model' energy crop by the U.S. Department of Energy

Summary​

Switchgrass is a perennial grass native to the United States that has been extensively studied as a promising energy crop for biofuel production. Selected as the model energy crop by the U.S. Department of Energy, it offers high biomass yields, efficient C4 photosynthesis, and drought resistance. Switchgrass can grow 3 to 10 feet tall with deep root systems that can improve soil organic carbon and revitalize damaged soils. Switchgrass requires minimal pesticides once established and can be grown on marginal land unsuitable for high-value crops. Typical yields reach 11 tons per hectare annually, with optimized cultivars achieving 16 tons and maximum yields exceeding 40 tons per hectare.

Switchgrass is a perennial herbaceous grass that is native to the United States that has been investigated extensively for its high potential as an energy crop for the production of biofuels. Switchgrass has shown so much potential that it was selected as the "model" energy crop species by the United States Department of Energy in their extensive national studies into energy crops 1. Switchgrass first caught the interest of the United States Department of Agriculture (USDA) back in the 1930s when it was bred to develop varieties that could assist in regenerating land in Nebraska that was damaged by widespread drought 2. Afterwards, additional varieties were developed for use as animal forage and conservation purposes, leading to millions of acres of switchgrass being grown throughout the United States. This led to the development of an extensive database of growing and management practices being readily available for the development of switchgrass as an energy crop.

The biology of switchgrass​

Switchgrass can be grown from seed up to heights ranging from 3 to 10 feet tall, consisting mainly of leaves and stem made of lignocellulosic organic material. Switchgrass follows a C4 photosynthesis pathway (compared to the C3 photosynthesis pathway seen with crops such as wheat), which essentially means that it has more efficient water usage, produces more biomass, and captures more carbon from the atmosphere when grown in warmer and drier climates compared to C3 crops 2. Being a perennial grass, it can technically stand indefinitely, but it is typically re-sown after approximately 10 – 20 years in order to maintain productivity 2.

Switchgrass, like other potential herbaceous energy crops, has a deep and extensive root system that can penetrate to depths of around 10 feet 2. This allows it to access nutrients and water deep in the soil, providing drought resistance and general hardiness 2. The root systems of switchgrass are so extensive and require so much energy to develop that it is usually not harvested until its second year of growth and does not reach its full above-ground growth potential until its second year. In some studies, the root systems of switchgrass have been found to be larger than the above-ground biomass 3.

Why is switchgrass desirable as an energy crop​

Crop biology​

Because switchgrass is a C4 crop, it can be grown in areas that are under more water and heat stress where it is impractical to grow high-value crops that require irrigation 2. This is where part of the claim that switchgrass can be grown on 'marginal' land stems from, as the definition of marginal land can include land that is not currently profitable or practical to grow certain crops 4. Switchgrass is also a plant that has a relatively low lignin content which in most cases is ideal for the production of biofuels 3.

Soil organic carbon (carbon fixing)​

Switchgrass effectively increases soil organic carbon concentrations, which can revitalize damaged and overworked soils 1 2 3. The revitalization of the soil is primarily due to the deposition of root biomass into the soil as a result of switchgrass' extensive root system. Carbon from the atmosphere is removed in the form of carbon dioxide via photosynthesis, which is then used to construct new root material. Over time, as the root material begins to turn over and be replaced, the existing root material is deposited into the soil. Additionally, the root system can transport nutrients down into the soil, where metabolic action from microbes further contributes to the revitalization of the soil 5.

Pesticide and herbicide usage​

Because switchgrass is native to the United States, it is well adapted to resist insects and other pests, and once a switchgrass crop is established, it has been shown to require low pesticide usage 2. With regards to weeds, established crops may only require one or two applications of herbicide over its lifetime, but weeds can pose an issue during the establishment of the crop in the first two years 2.

Economics of switchgrass​

Switchgrass has a number of beneficial traits that make it appealing as a commercial energy crop. Overall, its production is considered highly cost effective especially when grown on marginal land 3. Switchgrass also has a number of potential alternative usages such as for forage, organic fibre, and heating fuel, which can provide additional security for farmers to respond to market variability 3. Switchgrass yields are also considered highly reliable across a wide range of growing environments, further increasing its dependability for farmers 3.

Biomass yields​

Lastly, and probably the most important aspect of switchgrass as an energy crop is its ability to grow large amounts of biomass. Switchgrass is considered a highly productive crop, with yields around 11 tons per hectare per year (~5 tons per acre per year) considered a typical and easily achievable yield once established 2. For cultivars that are optimized for their specific environments, average yields lie around 16 tons per hectare per year (~7.2 tons per acre per year), with maximum yields greater than 20 tons per hectare per year and the highest yields reaching over 40 tons per hectare per year (~18 tons per acre per year) 3. The high yields that are mentioned here are considered outliers but they show that switchgrass does have the potential to be further cultivated to produce higher average yields which is desirable as it would utilize less land. It should be noted that all of the yield values listed above involved the usage of fertilizers, and in studies where low input regimes are used, reported yields are typically lower around 6.2 tons per hectare per year (~2.8 tons per acre per year) 3.

Sources​

Footnotes​

  1. Wright, L. (2007, August). Historical perspective on how and why switchgrass was selected as a "model" high-potential energy crop (ORNL/TM-2007/109). U.S. Department of Energy, Office of Energy Efficiency & Renewable Energy. https://www.energy.gov/eere/bioenergy/articles/switchgrass-high-potential-energy-crop ↩ ↩2

  2. Downing, M., Eaton, L. M., Graham, R. L., Langholtz, M. H., Perlack, R. D., Turhollow, A. F., ... & Brandt, C. C. (2011). U.S. billion-ton update: Biomass supply for a bioenergy and bioproducts industry (No. ORNL/TM-2011/224). Oak Ridge National Laboratory. ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8 ↩9 ↩10

  3. McLaughlin, S. B., Bouton, J. H., Bransby, D. I., Conger, B. V., Ocumpaugh, W. R., Parrish, D. J., Taliaferro, C. M., Vogel, K. P., & Wullschleger, S. D. (1998). Developing switchgrass as a bioenergy crop. In J. Janick (Ed.), Perspectives on new crops and new uses (pp. 282–299). ASHS Press. ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8

  4. Russo, C., Cirillo, V., Pollaro, N., & et al. (2025). The global energy challenge: Second-generation feedstocks on marginal lands for a sustainable biofuel production. ChemBioTech Agriculture, 12, 10. https://doi.org/10.1186/s40538-025-00729-7 ↩

  5. Kasanke, C. P., Zhao, Q., Bell, S., Thompson, A. M., & Hofmockel, K. S. (2021). Can switchgrass increase carbon accrual in marginal soils? The importance of site selection. GCB Bioenergy, 13(2), 320–335. https://doi.org/10.1111/gcbb.12777 ↩