Ten fundamentals about bioenergy: Part 6 Perennial bioenergy crop systems

Kurt Thelen, Michigan State University Extension, Department of Crop and Soil Sciences - August 20, 2009

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Fundamental #6: Perennial bioenergy crop systems have environmental advantages compared to annual crops.

This article will discuss the environmental advantages of perennial energy crop systems relative to annual crop systems. Second generation energy crops including switchgrass and miscanthus are warm season perennial grasses. Being perennials, they maintain a viable root system year-round and following winter dormancy they will regenerate shoot growth from the same root system that supported the plant the previous year. In the fall when the shorter days and lengthening nights signal the onset of another winter, the plant will translocate nutrients to the root system to ensure survival until the next growing season. This perennial life cycle infers distinct environmental advantages relative to annual crops:

The continuous ground cover afforded by perennial crops reduces the potential for soil erosion.
The extensive robust root system characteristic of perennial crops has the potential to sequester more carbon than that of annual crops.
The post-growing season translocation of nutrients to the root system characteristic of perennial crops offers management options to decrease input costs and maintain nutrients in the soil profile.
Perennial crops reduce energy inputs by not requiring annual stand establishment, and they generally do not require herbicide inputs after stands have successfully established.
Ecological studies suggest that perennial crops such as switchgrass support a more diverse wildlife base, particularly birds, than do annual crop systems.

In earlier articles, we discussed the tremendous environmental advantages biofuels have relative to fossil fuels. Second generation bioenergy crops will further improve the already significant environmental advantage of bioenergy. The next article will discuss the importance of maintaining annual crops in our bioenergy arsenal and various management systems to improve their environmental profile.

Read part 1, part 2, part 3, part 4, part 5, part 7, part 8, part 9, part 10 of this series.

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