Tuesday, October 09, 2012

Pennisetum purpureum - Biofuel, ornamental specimen, invasive species, weed with a tendency towards hybrid cultivars with common names like Napier grass or king grass


                The demands of the world's markets have resulted in the movement of species across continents and oceans. Some species are hitch hikers that find landscapes suitable for establishment and reproduction; they hang on for the journey and then drop off to start a new life occasionally becoming pests or worse in their new homes. If these accidental introductions are costly, they grow in the shadows of the intentional introductions of novel species that are cultivated for a wide variety of market interests from gardening to befouls; aquariums to commercial farming.

               When a new species gets loose for whatever reason and begins to harm natural areas, home owners' landscapes, and agricultural processes, the cost is not born by the persons who profited from the introduction, but rather by the people who are impacted directly or who try to clean up the mess. The initiating persons or companies (they are after all people too) externalize the potential costs and damages of clean up and mitigation onto the general public because their own self interest and profit taking in the present takes precedence over harm to the commons in the future.

               When the species is unknown and there is little information, one may hide behind the lack of data and claim preemption from precaution because of a lack of data. When however the species is well known to be a problem it becomes harder to see the logic of the moment other than self interest at the expense of the community. Almost exactly five years ago to the day, I listed on my web log plant species being considered as biofuel sources (Saturday, October 13, 2007 "List of Invasive Biofuel Species (updated with links to GRIN & GCW): Traits of Invasive Species"). I found that most of the species under consideration were invasive some place in the world.

               One species I listed was the grass Pennisetum purpureum Schumach. (elephant grass)[69] native-Africa[GRIN]; agricultural weed, cultivation escape, environmental weed, garden thug, naturalized, noxious weed, sleeper weed, weed: Caribbean, United States, Canada, Hawaii[GCW]. Pennisetum purpureum has many names: elephant grass, merker grass, napier grass , (English);  napier, herbe éléphant, fausse canne át; sucre (French);  Elefantengras (German);  capim-elefante (Portuguese);  pasto elefante (Spanish);  gigante (Costa Rica);  mfufu (Africa);  co voi (Vietnam);  'erepani (Cook Islands);  acfucsracsracsr (Kosrae);  bokso (Palau);  puk-soh (Pohnpei);  vao povi (Samoa).[1]  Because it cross pollinates relatively easily (Pennisetum purpureum Schumach. x Pennisetum glaucum (L.) R. Br., e.g.), a trait of many invasives, there is even report of an interspecific hybrid cultivar known as king grass.[2]  Pennisetum purpureum is native to Africa but now grows in tropical areas throughout the world, frequently becoming naturalized. It is grown as an ornamental in the Flora of North America  region, and, less commonly, as forage.

               Pennisetum purpureum spreads by seed, usually into disturbed areas, but mostly by short rhizomes and tall stems that fall and root at the nodes just like some running bamboos that are now terrorizing New England (Phyllostachys aureosulcata).  Pennisetum purpureum like other invasive biofuel species (Arundo donax, Phalaris arundinacea, Miscanthus × giganteu) have triggered scientists (subject matter experts) with the Weed Science Society of America (WSSA) to "caution that many of these crops also are known as invasive weeds in some of the regions where they are planted. That means growers must exercise caution in order to protect our natural ecosystems."

               Recent rumblings from EPA have indicated what everyone already knows: Invasive species reduce atmospheric carbon; they are, in fact, carbon sinks - and this is no surprise. What exactly are we looking for in a plant species but high levels of accessible carbon? Allow me to quote directly from my 2007 blog:

The long term challenges may collide with the short term benefits
“…because traits deemed ideal in a bio-energy crop are also commonly found among invasive species (note the following).”   
"C4 photosynthesis; Long canopy duration; Perennial; No known pests or diseases; Rapid growth in spring (to out-compete weeds); Sterility; High water-use efficiency; Partitions nutrients to belowground components in the fall” [3]

               What exactly are we doing when we allow private interests to make unsubstantiated claims of non invasiveness, when for profit interests can hide behind trademarks, when the environment can be destroyed for personal gain in the name of some greater nebulous undefined good?

Elephant grass, Napier grass, (see also: hybrid cultivar: king grass - no weed risk opr invasive species risk assessment found) 

1.     Pennisetum purpureum. 1827. Schumacher, Heinrich Cristian Friedrich. In: Beskrivelse af Guineeiske planter 44. Tropicos. http://www.tropicos.org/Name/25509854

2.     Pennisetum purpureum Schumach. Napier Grass. GBIF Data Portal.  http://data.gbif.org/species/Pennisetum%20purpureum

3.     Pennisteum purpureum. USDA Forest Service. John K. Francis, Research Forester; International Institute of Tropical Forestry, Jardín, Botánico Sur, 1201 Calle Ceiba, San Juan PR 00926-1119, in cooperation with the University of Puerto Rico, Río Piedras, PR 00936-4984 http://www.fs.fed.us/global/iitf/pdf/shrubs/Pennisetum%20purpureum.pdf

4.     Pennisteum purpureum. USDA Plants Database. http://plants.usda.gov/java/profile?symbol=PEPU2
5.     Pennisetum purpureum (Poaceae). Global Compendium of Weeds. http://www.hear.org/gcw/species/pennisetum_purpureum/

Napiergrass: A Potential Biofuel Crop for the Sunny Southeast

[2] Kukkonen, Carl. 2009. Giant King Grass An Energy Crop for Cellulosic Biofuels & Electric Power Plants. pdf. http://www.viaspace.com/docs/biofuels_jakarta_compressed_final.pdf [accessed October 9, 2012]
[3] Thompson, John Peter. 2007. List of Invasive Biofuel Species (updated with links to GRIN & GCW): Traits of Invasive Species.    http://ipetrus.blogspot.com/2007/10/biofuel-species-listing-traits-of.html

1 comment:

Richard R. Rodriguez CPA said...

Need more information from your research to agree with your statements. Giant King Grass is NOT invasive.Giant King Grass actually has 80% of its roots mass in the top 18 to 24” of the soil. The other 20% are small hair like roots that can ...go deeper and break down each year and regenerate new roots. In summary, very little of the root system is deeper than 24”. The roots could never get to an aquifer. A major benefit of GKG is its ability to stop run off water and erosion loss of surface water that would normally run into the ocean.