Environmental Engineering Reference
In-Depth Information
place and there is no net emission of greenhouse gases,
but that is not the case with today
'
is biofuels.
billion poor people on our planet, who
have no access to commercial energy, gather and burn
plant material for cooking and heat. They live according
to the theoretical model and generate no excess green-
house gas from their biofuels. As long as they use only
what grows naturally the model is correct. However,
modern farming requires extra chemical and energy
inputs, and here is where care is needed to identify all
the inputs and include them in balancing the energy and
environment scales. Energy is required to produce the
needed fertilizer, run farm machinery, harvest the crop,
transport it to the factory, and run that factory. Green-
house gas emission and energy consumption have to
include all of the inputs to the process.
There also are unintended consequences as food crops
are turned into fuel crops. These include increases in food
prices and competition for land and water. With world
population forecast to increase from six billion in the year
Roughly
.
, the food-into-fuel
program will have ever more serious unintended conse-
quences, particularly on prices, and become unsustainable
as now practiced.
Ethyl alcohol (ethanol) derived from plants can be used
as a motor fuel as well as for convivial drinking. Alcohol
biofuel has been trumpeted as a way to greatly reduce
emissions of greenhouse gases in the transportations
sector, as well as a way to reduce demand for the oil that
now is mainly used for transportation. In today
to about nine billion in
'
is biofuels
program, starches in corn and wheat are
rst converted to
sugar, or sugar comes directly from a plant like sugarcane.
