Environmental Engineering Reference
In-Depth Information
fireplaces) through brick or stone flues under concrete-
covered granite floors. The Chinese kang was just a large
heated platform (@4-5 m
2
) that served as a resting place
during the day and a bed at night. The advantages of
these arrangements are clear in comparison with brazier
heaters that were common in both Asia and Europe (the
British House of Commons was heated by large charcoal
fire pots until 1791). The brazier heaters offered only a
spot source of warmth and could produce dangerous
levels of carbon monoxide.
Advances in residential heating and cooking were slow
(W. Lawrence 1964). Draft chimneys appeared in Eu-
rope only during the late Middle Ages, when tile stoves
were used in Germany and Scandinavia but smoky, ineffi-
cient fireplaces were still used in England (Edgerton
1961). In Europe iron plate stoves spread widely only
during the seventeenth century, when they were brought
by French and German settlers to North America. Dur-
ing the late eighteenth century Benjamin Franklin and
Count Rumford (Benjamin Thompson) came up with
major efficiency improvements (Brown 1999). The per-
formance of these simple stoves varied widely with design
and fuel, but they certainly did not surpass the levels
measured in modern tests of their contemporary counter-
parts (mostly less than 25%). The best available studies of
those societies that still rely almost solely on phytomass
for their thermal energy put their annual consumption
of woody matter and crop residues at less than 10 GJ
per capita for the poorest communities in the warmest
regions. The rates could have been 30-40 GJ per capita
in relatively rich mid-latitude cities, where wood-based
production of beer, bricks, tiles, metals, and glass added
considerably to the residential demand.
This estimate receives excellent confirmation from a
careful reconstruction of firewood demand in London,
where per capita (dry matter) demand in 1300 averaged
about 1.75 tons, or roughly 30 GJ (Galloway, Keene,
and Murphy 1996). In societies on the verge of industri-
alization the needs were certainly much higher. Those
nineteenth-century North American and European fami-
lies who lived between 40
N and 50
N and in houses
well heated with large iron stoves needed annually 50-
200 GJ per household, or about 15-50 GJ per capita.
Cooking, water heating, and industrial needs would
have easily doubled these rates. Indeed, the best per cap-
ita fuel wood consumption estimate for the United States
in 1850 is about 97 GJ (Schurr and Netschert 1960).
Global estimates of preindustrial biomass consumption
can aim only at the right order of magnitude. With 20
GJ per capita for the 1800 population of about 1 billion,
it would be some 20 EJ, and up to 30 EJ is plausible. In
gross energy terms, this would be at most one-tenth of
the total energy content of fossil fuels that were burned
annually in the year 2000, but considering the much
higher efficiencies of modern fuel converters, the differ-
ence of actually available (useful) heat energy would be
at least 30-fold.
The availability of phytomass was also a key determi-
nant of metallurgical progress because charcoal was the
only source of carbon used to reduce ores in preindus-
trial societies (Biringuccio 1540). Copper, the principal
constituent of bronze (together with tin and smaller
amounts of lead and silicon), was the first metal smelted
in relatively large amounts. Forbes (1966) presented
careful studies of Roman copper production that in-
volved roasting and smelting of chalcopyrite followed
by refining. Specific fuel needs were enormous, about
90 kg of wood per kilogram of copper, or 1.3 GJ/kg.
With average wood growth of 900 kg per tree in 40
years, and 300 trees per hectare (about 6.75 t/ha
a),
