Environmental Engineering Reference
In-Depth Information
1992; Needham 1964), and then decreased even more with the introduction of the
i rst blast furnaces. These taller structures appeared i rst during the fourteenth
century in the Rhine-Meuse region and could produce cast iron (called pig iron, as
the metal was cast into shapes resembling chunky pigs). Their lower specii c demand
was far outweighed by the expanded production. which led to acute wood shortages
in some regions.
Sussex is now an afl uent county, but by the mid-sixteenth century, when a single
furnace claimed annually a circle of forest with a radius of about 4 km, its inhabit-
ants petitioned the king to shut down many furnaces, wondering “what number of
towns are like to decay if the iron mills and furnaces be suffered to continue” and
where the wood for their houses, wheels, and barrels would come from (Straker
1969, 115). During the i rst decade of the eighteenth century an English blast furnace
typically worked for eight months a year (between October and May) and smelted
about 300 t of pig iron (Hyde 1977). With 8 kg of charcoal per 1 kg of iron and 5
kg of wood per 1 kg of charcoal, a single furnace would have needed some 12,000
t of wood during its eight-month campaign, and the overall English demand for
metallurgical charcoal would have claimed more than 1,000 km
2
a year; a century
later the U.S. demand added up to an equivalent of nearly 2,500 km
2
of mature
forest cut every year (box 9.2).
In Europe, Sweden continued to be a heavy charcoal user throughout the nine-
teenth century. In 1850, 25% of the country's wood harvest was used to make
charcoal (Arpi 1953). By 1900 the typical charging ratio was less than 1.5 kg of
charcoal per 1 kg of metal, and the best Swedish furnaces needed as little as 0.77
kg (Greenwood 1907). Brazil is now the world's only consumer of metallurgical
charcoal, made from fast-growing eucalyptus trees, with large plantations mostly in
the state of Minas Gerais (Peláez-Samaniegoa 2008). Charcoaling is done in hemi-
spheric or cylindrical brick kilns, which exposes workers to a number of possible
injuries and to hazardous smoke (Kato et al. 2005). No by-products are recovered,
and the conversion efi ciency remains no better than 25%. Less than 10% of it is
used by households and in cement production, close to 10% goes for making
ferroalloys, and 75% is charcoal for blast furnaces. A typical requirement has been
about 2.9 m
3
(or 725 kg) of eucalyptus-derived fuel to smelt 1 t of hot metal
(Ferreira 2000).
Biofuels Today
At the beginning of the twenty-i rst century, biomass fuels were still more important
than either hydro- or nuclear electricity—at least when their contribution is expressed
