Comparing Photosynthesis and Photovoltaics
		Photosynthesis
		claim#1	2,400,000,000,000,000,000	btu/year
		*	0.293	watt-hrs/btu
		=	703,200,000,000,000,000	watt-hrs/year
		/	150,000,000	km^2 of land on earth
		=	4,688,000,000	watt-hr/sq km
		PV
		claim	1,000	watts/meter^2 at noon
		*	5	hrs/day of noon sun equivalent, global average
		=	5,000	watt-hrs/m^2/day
		*	365	days/year
		=	1,825,000	watt-hrs/m^2/year
		*	1,000,000	m^2/km^2
		=	1,825,000,000,000	watt-hrs/km^2/year
		Ratio PV:Photosynthesis
			389	PV:Biomass
			0.26%	Biomass:PV
		Validate Claim
		claim#1	2.4E+18	btu terrestrial plants
		/	1.2E+11	tonnes
		=	20,000,000	btu/tonne
		/	1,000	kg/tonne
		/	2.2	kg/lb
		=	9,091	btu/lb
		(This result meets sanity test.)
		Claim#1:
		Today, terrestrial plants produce about 120 billion metric tons of biomass (dry weight)1 globally each year (IPCC, 2001). The energy in this biomass totals about 2,400 quads2 (1 quad = 1015 Btu). Modern economies, however, rely extensively on fossil fuels rather than biomass for their energy. In 2001, the world consumption of fossil fuels totaled about 315 quads, about one-quarter of which was consumed in the United States (BP, 2002).
		http://www.nae.edu/nae/bridgecom.nsf/weblinks/MKUF-5NTMX9?OpenDocument