Environmental Engineering Reference
In-Depth Information
4
Phytomass Harvests
Modern phytomass harvests i t mostly into four distinct categories. Food harvests
have been transformed as humans have evolved from simple foragers collecting
edible plants, hunting animals, and catching aquatic species to agriculturalists
relying i rst on extensive shifting cultivation and later on intensive methods of
farming, including large-scale domestication of animals and worldwide i shing
efforts. Phytomass use as fuel was relatively limited in all foraging societies, but it
increased with a sedentary existence and with the use of wood and charcoal in the
production of metals. Because the evolution of agriculture also involved the domes-
tication of animals, the third major purpose of biomass harvest has been to secure
feed for these mammals and birds.
I hasten to add that the order of harvest purposes just presented is valid only in
terms of its evolutionary appearance. In many late nineteenth-century societies
fuelwood was mostly displaced by coal, but large quantities of feed were needed for
draft animals as agricultural activities continued to rely heavily on draft horses and
cattle. This animal labor was in turn displaced by machines, and wood became a
marginal fuel in all modern afl uent societies, but the importance of animal feed has
only increased: metabolic imperatives mean that the annual total of feed phytomass
that is required to produce an abundance of meat, eggs, and dairy products now
greatly surpasses that of global food harvests and is also greater than the aggregate
of woody biomass used for fuel in all afl uent economies.
The i nal, less homogeneous category subsumes all uses of plants as raw materi-
als. The earliest uses of phytomass in crafting simple tools go far back into our
hominin past, but once again, only sedentary habitation resulted in a voluminous
need for construction timber (in maritime societies also for building ships) and
wood for agricultural implements (hoes, plows, harrows), household utensils, fur-
niture, and an enormous variety of increasingly sophisticated manufacturing tools
