Environmental Engineering Reference
In-Depth Information
Box 9.5
Sawn Wood for Railroad Ties, 1830-1900
The standard rate of tie installation is about 1,900 (1,888) ties per kilometer of track
in the United States (where the rails are joined by spikes) and 1,500 in Europe (where
iron or steel chairs are used for joining). A single tie (255
17.5 cm) weighs
between 71 kg for pine and 99 kg for oak (Webb 2011), and hence 1 km of tracks
needs as little as 107 t of sawn wood in Europe and as much as 188 t in the United
States. The railroad age began in 1830 with the Liverpool-Manchester link (56 km).
By 1860 the worldwide length of railroads had surpassed 100,000 km, and by the end
of the nineteenth century the UK had about 30,000 km of track, the European total
was about 250,000 km, Russia had 53,000 km, the U.S. total had surpassed 190,000
km, and the worldwide length of railroad tracks had reached 775,000 km (Williams
2006). This means that between 1830 and 1900, the expansion of railroads consumed
at least 100 Mt of sawn wood for the initially emplaced ties and, with an average
annual replacement rate around 3%, at least another 60 Mt for track renewal.
×
22.5
×
in the eastern United States is 46 years: consequently, annual rates of 3% for the
decades before 1950 and 2% afterward would be a good approximation of typical
replacement demand. Fairly good historical statistics for the post-1830 expansion
of railroads make it possible to calculate the highest annual demand for new ties,
as well as to estimate the cumulative sawn wood demand for ties initially emplaced
and used in subsequent track maintenance during the nineteenth century (box 9.5).
Finally, wood is harvested to make paper. The production of mechanical pulp
became common during the 1870s, but this inferior product (with high lignin
content, prone to yellowing) is now used only for newsprint, toilet paper, cardboard,
and building board. Chemical pulp was made i rst by the alkaline (soda) process
and later (starting during the 1870s) by the acid (suli te) method, which, unfortu-
nately, produces notoriously brittle and crumbling paper (Smil 2005). This draw-
back was solved by the sulfate process that became commonly used after 1900 and
that now accounts for about 65% of the world's wood pulp production. These
innovations converted tree cellulose into the cheapest mass-produced commodity of
modern civilization and led to a still continuing increase of printed matter: during
the 1850s, European and American paper output was less than 5 kg per capita; by
1900 the U.S. rate had surpassed 30 kg/capita, and a century later it was more than
200 kg per capita; and by 2010 the global mean was above 50 kg per capita (FAO
2011e).
