Napier grass: a novel energy corp development and the current status in Thailand

In recent years, there has been increasing an interest in the potential role of perennial C4 grasses, such as switch grass (Panicum virgatum) in the US and miscanthus (Miscanthus spp.) in Europe, as promising energy crops. Characteristics making perennial C4 grass attractive for biomass energy production are their high biomass yield potential, high lignocellulosic content, low input demand, and positive environmental impact. In Thailand, the Energy Regulatory Commission has established the Renewable and Alternative Energy Development Plan to reduce fossil fuel usage by 25% over 10 years (2012-2021). One of its targets is to increase alternative energy production to 13,927 MW by 2021 from the present 7,294 MW. To meet this goal, approximately 8,400 MW of electricity is needed, which could be sustainably supplied through 221,760,000 tons of harvestable biomass each year, exploiting current land resources. Of the 221,760,000 tons of available biomass, napier grass (Pennisetum purpureum) accounts for the majority. Napier grass originated from Africa where it is called Giant King Grass. This grass was introduced into Thailand over 30 years ago. After evaluating perennial grasses available in Thailand. 'Pakchong 1' napier grass has showed the greatest potential for biofuel production. In irrigated areas, napier grass provided up to 438-500 tons of fresh biomass/ha after harvesting 5-6 times per year. One ton of napier grass can produce 90 cu m of biogas. The heating value for compressed biogas (CBD) produced from its biomass is 14-18 MJ/kg. The Royal Thai Government strengthened its support for renewable power generation from napier grass for two reasons: to generate electricity to feed the grid, and to produce CBG as an alternative for exhausting NGV [natural gas vehicle] and as a substitute LPG. However, since research on producing napier grass as a bioenergy source in Thailand is comparatively recent, there are still significant limitations for further development. The key challenges for napier grass production are the unavailability of a water supply source to allow high yield potential, need for the appropriate cultivars for given ecological conditions, and cost-effective management methods.