Environmental Engineering Reference
In-Depth Information
everyday cooking, as well as because of uncertain population totals. Estimates
become more defensible for the modern era, and my choice of a plausible global
approximation is an average annual fuel wood consumption of about 20 GJ/capita
in 1800 (Smil 2010b). With a global population of one billion, that would yield a
worldwide woody phytomass combustion of about 20 EJ (about 1.3 Gt of air-dried
wood). Crop residues used as fuel added most likely no more than another 2 EJ,
within the conservative error range of
15%. By the mid-nineteenth century the
total mass of wood and crop residues used for fuel surpassed 25 EJ, but then the
rapid shift to coal lowered the phytomass contribution to a level only slightly higher
than in 1800.
As a result, the nineteenth century's cumulative combustion of wood-dominated
solid biofuels added at least 2.4 YJ, while all fossils fuels (until the early 1860s only
coal and peat, afterward also small volumes of crude, and just before the century's
end also small volumes of natural gas) consumed between 1800 and 1900 contained
only about 0.5 YJ (Smil 2010b). On the global scale, wood-dominated phytomass
combustion thus provided no less than 85% of all fuel burned during the nineteenth
century, making it—contrary to a common impression that it was the i rst century
of fossil fuel (more accurately, coal) era—still very much a part of the long wooden
(or, more accurately, wood-and-straw) age.
Fernandes et al. (2007) offer a slightly different account: they put the global
biofuel use at 1 Gt in 1850 and about 1.2 Gt in 1900; these totals would translate
to about 18 (17-20) EJ/year, somewhat lower than my estimates. In most national
cases accuracy of fuelwood consumption accounts does not improve signii cantly
during the twentieth century as approximations are unavoidable even when quan-
tifying a relatively high dependence on phytomass fuels that lasted in the world's
most populous Asian nations (China, India, Indonesia) well into the second half of
the twentieth century and that still dominates rural energy use in Brazil, the most
populous country in Latin America and the world's eighth-largest economy. Perhaps
the best illustration of the data problem is the fact that Fernandes et al. (2007) put
the uncertainty range of their global biofuel estimate in the year 2000 (2.457 Gt)
at
±
±
55%, no smaller error than for 1950 (their uncertainty range for 1850 was
±
85%).
My reconstruction puts the global combustion of fuelwood and crop residues
at 22 EJ (1.45 Gt) in 1900, 27 EJ (1.8 Gt) in 1950, and 35 EJ (2.3 Gt) in 1975.
The lowest total of global fuelwood combustion at the end of the twentieth century
is the FAO's 1.825 Gm
3
of coniferous and nonconiferous “wood fuel” (the latter
category accounting for nearly 90% of the total), as well as 75 Mm
3
of “wood
