A Few Quick Global Energy Stats
I was unsatisfied with slide 7 (see above) of Gail Tverberg’s presentation Rentier Debt and the Collapse of Debt-Based Finance. So I thought I would scratch out some numbers that I think forms a better basis for comparing human and “natural” systems in magnitude and interaction. Natural in the sense of “other than human” – of course human systems are a subset of natural systems.
Incoming solar radiation (top of atmosphere): ~170,000 Terawatts
(Makarieva, Gorshkov, Li, 2008)
Captured by photosynthesis: ~100 Terawatts
(Nealson and Conrad, 1999)
Total human energy production: ~500e15 BTU/yr
(EIA IEO 2011)
1e15 BTU = 1 quad
1 TWyr = 8.76 x 1012 kWh = 31.54 EJ = 29.89 quad
505 quads/yr * 1 TWyr / 29.89 quads = 16.9 TW
Human -v- Natural
16.9/100 ~ 17% ~ 1/6
Human energy uses 19% renewables.
Biomass = 13% of renewables.
Biomass ~ .19 * .13 ~ 2.5% of human energy
(REN21 (2010), pg 15)
On average, plant gross primary production on earth is about 5.83 x 106 cal m-2 yr-1. This is about 0.06% of the amount of solar energy falling per square meter on the outer edge of the earth’s atmosphere per year (defined as the solar constant and equal to 1.05 x 1010 cal m-2 yr-1). After the costs of respiration, plant net primary production is reduced to 4.95 x 106 cal m-2 yr- 1, or about 0.05% of the solar constant.
Human use of net primary production (NPP): 42-58 Pg
which is 30-39% of terrestrial production
or 17-25% of global production (terrestrial + aquatic)