Environmental Engineering Reference
In-Depth Information
Cradle-to-cradle
Cradle-to-grave
Cradle-to-gate
Gate-to-gate
Gate-to-grave
Raw
materials
Processing
Distribution
End
consumer/
disposal
Figure 4.7
Variations of life cycle assessmentss that are dependent on boundary setting.
waste. This would represent a closer approach to a real cradle-to-grave assessment for
food products.
Other variations of LCAs are
gate-to-gate and cradle-to-cradle
(Fig. 4.7). A gate-to-gate
LCA is a partial analysis that is limited to a certain part of the production chain to
evaluate the impact of that part (e.g., processing, distribution, recycling, etc.) A cradle-
to-cradle approach is specific to products that can be recycled into the same product, can
be made into different products without downgrading the recycled material, or returned
to the soil as compost. A true cradle-to-cradle approach would also use renewable energy
for manufacturing and distribution.
An example of a cradle-to-cradle system is the recycling of glass bottles or aluminum cans,
from which materials can be considered 100 percent reusable. From the point of view of
material use, a cradle-to-cradle production system is truly sustainable and this is the direction
society needs to move in to create a sustainable economic system.
Well-to-wheel LCA
Although this discussion is limited to sustainability of food products, the growing development
of biofuels made from agricultural products makes the opportunistic inclusion of specific
terminology for fuels into the LCA.
Well-to-wheel
is a specific LCA for transportation fuels
that is equivalent to a cradle-to-grave analysis. A typical well-to-wheel analysis for
nonrenewable fuel includes extraction of the feedstock (e.g., petroleum or natural gas),
refining to transform the feedstock into usable fuel (e.g., gasoline and diesel), distribution,
efficiency of the engine that burns that fuel, and the efficiency of the vehicle transmission.
Partial analyses are also possible. For instance a
well-to-station
analysis includes extrac-
tion, production, and distribution; a
station-to-wheel
encompasses fuel lost during pumping
and vehicle efficiency; a
well-to-tank
incorporates all the steps but vehicle efficiency; and a
tank-to-well
includes only engine and transmission efficiency.
In the case of fuels made from agricultural products (biofuels), the well-to-wheel analysis
differs in the well-to-station portion. The well-to-station segment includes cultivation,
transformation of the feedstocks, and distribution. Cultivation contains land use, fertilizers,
water, fuel for tractors, and so on. The transformation of feedstocks into fuel involves process-
ing corn into starch and then into ethanol, or oilseeds into vegetable oil with posterior
