the iron and steel products, the dry bulk products, the containerized freight
and the “other freight,” which total 98million tons per year. I’m leaving
the vehicles to one side for a moment. I subtract from this an estimated
25million tons of food which is presumably lurking in the “other freight”
category (34 million tons of food were imported in 2006), leaving 73 million
Converting 73 million tons to energy using the exchange rate suggested
above, and sharing between 60 million people, we estimate that those im-
ports have an embodied energy of 33 kWh/d per person.
For the cars, we can hand-wave a little less, because we know a little
more: the number of imported vehicles in 2006 was 2.4 million. If we take
the embodied energy per car to be 76 000 kWh (a number we picked up on
p90) then these imported cars have an embodied energy of 8 kWh/d per
I left the “liquid bulk products” out of these estimates because I am not
sure what sort of products they are. If they are actually liquid chemicals
then their contribution might be significant.
We’ve arrived at a total estimate of 41 kWh/d per person for the em-
bodied energy of imports – definitely in the same ballpark as the estimate
of Dieter Helm and his colleagues.
I suspect that 41 kWh/d per person may be an underestimate because
the energy intensity we assumed (10 kWh/dE per person) is too low for
most forms of manufactured goods such as machinery or electrical equip-
ment. However, without knowing the weights of all the import categories,
this is the best estimate I can make for now.
Tables H.4 and H.5 show estimates of the Process Energy Requirement of
building materials and building constructions. This includes the energy
used in transporting the raw materials to the factory but not energy used
to transport the final product to the building site.
Table H.6 uses these numbers to estimate the process energy formaking
a three-bedroom house. The gross energy requirement widens the bound-
ary, including the embodied energy of urban infrastructure, for example,
the embodied energy of the machinery that makes the raw materials. A
rough rule of thumb to get the gross energy requirement of a building is
to double the process energy requirement [ ].
If we share 42 000 kWh over 100 years, and double it to estimate the
gross energy cost, the total embodied energy of a house comes to about
2.3 kWh/d. This is the energy cost of the shell of the house only – the
bricks, tiles, roof beams.