Radiative Heat Balance

The earth absorbs 0.6 W/m² more than it emits - out of an average global flux of 250 W/m². The total input power is 0.6 W/m² * ( 4 π 6371000^{2 ) m}2^ or 3.06e14 W or 306 Terawatts. Times 31557600 s/y that is 9.66e21 Joules.

How much of this is stored as biomass? Most biomass is recycled, consumed, turned back to heat. We are burning coal and cutting down trees far faster than nature is making them, so biomass is diminishing.

One human activity that preserves biomass is wood construction. The world harvested 425 million cubic meters of wood in 2006, the latest numbers I have. Let's pretend that is all energy-dense hardwood, 1500 kg/m³, and that all of that has an energy density of 16 MJ/kg . The energy stored in construction wood cannot exceed 425e6 * 1500 *16e6 or 8.2e18 J. 1e19 joules, about 0.1% of the incoming energy difference. In actual fact, some wood is burned as fuel, some wood is scrap, some wood buildings burn or decay, so the amount stored as wood in construction (or papers in file cabinets) is much less than 0.1% .

When someone talks about the incoming energy difference ending up as permanent biomass somewhere, assume they are innumerate. The sums must balance over time.