Environmental Engineering Reference
In-Depth Information
petrochemical-derived polymers became available, such as fibers, wood, and paper.
However, because materials are renewable does not mean that they are impact free when
compared with nonrenewables. Because renewable feedstocks come from agriculture- and
forestry-related activities, their production has similar impacts to any agricultural activity
including:
1.
Use of land.
2.
Destruction of ecosystems and natural habitats.
3.
Lost of biodiversity.
4.
Use of fertilizers, herbicides, and pesticides.
5.
Use of water and pollution of surface and subterranean water.
6.
Use of petroleum-based liquid fuels.
7.
Release of carbon entrapped in the soil and in the biomass.
Renewable feedstocks is covered more in Chapter 14.
Energy consumption for each material
Glass
It takes about 10.9 GJ of heat, usually from burning natural gas, and 532 kWh of electricity to
produce 1 metric ton of glass containers from virgin materials. After converting the electricity
to GJ and adding it to the thermal energy, the total energy spent per metric ton of glass contain-
ers is 12.6 GJ. If 100-percent recycled glass is used instead, energy requirements go down to
7.7 GJ of thermal energy plus 551 kWh of electricity, or 9.7 GJ per metric ton of containers.
These estimates do not take into account transportation and conversion efficiencies to produce
electricity.
The energy spent in transportation of raw material (as diesel fuel), assuming the material is
moved 320 km (200 miles), is 0.45 GJ/metric ton for new glass and 0.85 GJ/metric ton for
100-percent recycled glass.
When transportation is included, as well as the conversion efficiencies to produce electricity
and diesel, then the energy requirements to produce 1 metric ton of glass containers is 19.7 GJ,
for new materials, and 17.2 GJ for 100-percent recycled material (Gaines and Mintz, 1994).
Aluminum
When done with materials obtained from the ground, without the incorporation of recycled
stock, it takes 345 and 351 MJ of energy to make 1-kg of sheet metal to build the body and lid
of aluminum cans, respectively (Boustead and Hancock, 1981). Parker (1991) reports an
energy consumption of 280 MJ per kilogram aluminum without specifying the type of alloy.
These energy requirements come from the cumulative use of electricity, natural gas, and diesel
from the point of mining of each individual component, which constitutes the aluminum alloys,
to alumina production, smelting, ingot casting, ingot remelting, and the final rolling into sheets.
The total energy required to produce a single 355-mL (12 oz.) aluminum can is around
6.9 MJ (Table 12.2). Paradoxically, considering that a 355-mL can of regular soda provides
around 150 calories (0.63 MJ), the packaging material has an investment of 10 times more
energy that the energy provided by the drink.
Aluminum is highly recyclable, and the energy requirement to produce aluminum from
recycled cans is only 5 percent to what it takes to produce it from mined ores (Martchek,
2006). When the energy used during the collection and recycling process in incorporated, the
95-percent energy savings may drop to 33 percent (Parker, 1991).
