snapshot of the cellulosic energy grasses

Whenever I mention what I work on, nobody has ever heard of Miscanthus. Of course I consider my friends, family, & acquaintances to be pretty well-informed smart people, so this seemed a bit surprising. This lack of awareness about the incredible potential of Miscanthus & other crops as biofuel crops has been a big reason why I started this blog.

In order to simplify and clarify, I decided to make a brief list & descriptor (in no particular order) of the major energy crops, focusing on the perennial grasses. There are also non-grass cellulosic energy crops (such as poplar, willow, Jatropha and Agave--see previous blog post), which I will not go into here. Disclaimer: this is hardly an exhaustive description of all of these grasses, just what I choose to include...

1) Miscanthus (known sometimes as Elephant grass or Amur silver grass, this includes mainly the sterile hybrid Miscanthus x giganteus, but also relatives such as M. sinensis, M. sacchariflorus, M. floridulus). Tropical to temperate. Native to Asia & Africa.


Advantages: No fertilizer (nitrogen) input required, low degree of invasiveness (hybrid M. x giganteus is sterile), cold-tolerant, highly productive (see photo above!!), a carbon neutral source of fuel when life-cycle is considered, lots of natural variation in M. sinensis & M. sacchariflorus, can grow on marginal lands
Disadvantages: high initial planting costs (must plant rhizomes rather than seeds, due to sterility), M.x giganteus plants typically grown are all cuttings from a single genetic clone (greater genetic variation is typically favored), fairly high water needs during growing season--limits use in arid western U.S.

2) Switchgrass (commonly known as panic grass, Panicum virgatum) Native to North America.
Advantages: cold-tolerant, fairly drought-tolerant, relatively low fertilizer inputs needed, a carbon neutral source of fuel when life-cycle is considered, highly diverse, can grow on marginal lands
Disadvantages: roughly half as productive as Miscanthus in most climates, relatively high water needs during warm growing season (spring/summer) which limits use in much of the western U.S.

3) Maize (corn). Native to North America. Annual rather than perennial.
Advantages: well-established as an ethanol crop when using seeds, annual crops have some benefits, can use the stover (leaf tissue) as a byproduct of seed production for cellulosic ethanol production
Disadvantages: very high fertilizer and water input needs--leading to high carbon costs, not as prolific as dedicated cellulosic perennial grasses, growth for ethanol production competes with growth for food

4) Sugarcane (many species of Sachharum) Tropical to warm temperate climates, Native to South Asia. Brazil is the largest grower of sugarcane, where they generate ethanol as a by-product of sugar production. Brazil is self-sufficient in terms of fuel production due to this investment in sugarcane-based ethanol.
Advantages: high sugar content--sugar is directly fermented into ethanol,
Disadvantages: very water intensive, grows in tropical (warm) climates only thereby limiting its growth in the primarily temperate U.S., not typically grown for cellulosic biofuel production

5) Energy cane (sugarcane hybrids produced to make low sugar varieties).
Advantages: hybrids (crop behind person in above photo) often have increased vigour and are highly prolific, the energy cane varieties are bred to be more cold-tolerant than sugarcane which increases the growing range in the U.S., can potentially convert to ethanol in the same way as other cellulosic biofuel crops, can be more productive than sugarcane (producing more ethanol per unit of land)
Disadvantages: unless a "no sugar" variety is developed, separate conversions to ethanol are necessary (e.g., different process to convert sugar to ethanol vs. converting cellulose to ethanol), relatively high water needs, initial planting costs are high/intensive (established from cuttings rather than seeds), not cold-tolerant

6) Sweet sorghum (many varieties of Sorghum with high sugar content). Native to tropical and sub-tropical regions on all continents (except Antarctica)
Advantages: fairly high yield, relatively drought tolerant, direct conversion to ethanol from sugar (not typically cellulose)
Disadvantages: grown primarily for sugar conversion directly to ethanol rather than as a cellulosic form of ethanol production...but could be used for both (like energy cane), annual rather than perennial, high fertilizer needs, susceptible to pests, not cold tolerant


7) Native prairie (many species, primarily Switchgrass [Panicum virgatum], Indiangrass [Sorghastrum nutans], Eastern Gamagrass (Tripsacum dactyloides), Big Bluestem (Andropogon gerardii), Little Bluestem (Schizachyrium scoparium), and others)
Advantages: high biodiversity, excellent habitat for wildlife, renewable, requires no fertilizer or irrigation
Disadvantages: generates only a fraction of the productivity compared with dedicated energy crops