Switchgrass  
   
  amount units comments
   
  18 Gj/tonne claim(1)
* 1,000,000,000 Giga conversion
/ 3,600 j/wh conversion
= 5,000,000 wh/tonne  
/ 1,000 kwh/wh conversion
* 10 tonne/ha claim (1) (2)
= 50,000 kwh/ha/yr net energy captured by switchgrass
* 3,413 btu/kwh  
/ 5,800,000 btu/barrel  
= 29 barrels equivalent/ha
   
  Compare  
   
est. 4.00 kwh/m2/day approximate sunlight to ground
* 10,000 m2/ha conversion
* 365 days/yr conversion
= 14,600,000 kwh/ha/yr total sunlight
* 0.33% 24 hr efficiency of photosynthesis
= 48,180 kwh/ha/yr net energy captured by photosynthesis
   
  4% difference
   
  Sanity Check  
   
   
  5,000,000 wh/tonne see above
/ 3.413 btu/wh conversion
= 17,065,000 btu/tonne  
  1,000 kg/tonne conversion
  17,065 btu/kg  
  2.2 lb/kg conversion
  7,757 btu/lb  
   
est. 8,000 btu/lb approximate energy content of wood
   
  -3% difference
   
  Potential using all cultivated land  
   
  In terawatts  
   
est. 150,000,000 hectares Cultivated Land USA
* 50,000 kwh/ha/yr net energy captured by switchgrass
/ 1,000,000,000 twh/kwh  
= 7,500 twh/yr  
/ 8,760 hrs/year  
= 0.86 tw equivalent
   
  In barrels of oil equivalent  
   
est. 150,000,000 hectares  
* 29 barrels equivalent/ha
/ 1,000,000,000 barrels/billion barrels
= 4.41 billion barrels equivalent
   
       
1 McLaughlin, S., J. Bouton, D. Bransby, B. Conger, W. Ocumpaugh, D. Parrish, C. Taliaferro, K. Vogel, and S. Wullschleger. 1999. Developing switchgrass as a bioenergy crop. p. 282299. In: J. Janick (ed.), Perspectives on new crops and new uses. ASHS Press, Alexandria, VA.
   
2 +200 kg of N/ha