||P.219 bottom paragraph: "Photosynthesis is the largest-scale synthetic process on earth. About 1.0×10^14kg (100 billion tons) of carbon are fixed annually into organic compounds by photosynthetic organisms (often called the net primary productivity). This equals about 1% of the world’s known reserves of fossil fuels (coal, gas, and oil), or 10 times the world’s current annual energy consumption. The carbon source used in photosynthesis is the 0.04% CO2 contained in the air (about 8×10^14kg carbon) and the CO2 or HCO3- dissolved in lakes and oceans (about 400×10^14kg carbon). In addition to the organic compounds, another product of photosynthesis essential for all respiring organisms is O2. At the current rate, the entire atmospheric content of O2 is replenished by photosynthesis every 2000 years."