Environmental Engineering Reference
In-Depth Information
A medium-processed food such as tomato ketchup has a relatively low impact at the agricultural,
transportation, and consumption stages, and the highest impacts produced by packaging
(39 percent) closely followed by processing (33 percent). Bread, on the other hand, has the
highest impacts in the field and transportation followed by processing and a low impact at con-
sumption.
If the consumption of energy had been analyzed for these five products, then it is likely the
outcome would have been completely different; in addition, the relative impacts at each stage
will depend on the continent, country, or even region, and the only reliable way to determine the
real impact at each stage is by conducting a life cycle assessment.
Independent of the magnitude of the environmental impact of each particular food industry,
food-processing facilities have impacts that are common to most industries, which includes
energy in the form of electricity and heat, huge volumes of water, raw materials, packaging
materials, ingredients, gases and cryogenic fluids, biocides and sanitizers, just to mention the
most important. A consequence of processing along with the final product is the generation of
air pollution, wastewater streams, and solid waste.
Electricity and thermal energy
Food-processing plants use two types of energy: electricity and process heat. Electricity is
used for illumination and transformed into mechanical energy by electric motors that power
refrigeration units, air compressors, fans, grinders, mixers, dryers, conveyor belts, and so on.
Process heat is obtained normally with natural gas, other fossil fuels, or biomass where
available. Fuels are either burned in a boiler to generate steam that is delivered through pipes
to the points of use or burned directly at the equipment, for instance in dryers, ovens, and
fryers.
Commonly, electricity is purchased from utility companies and in some cases process heat
(or cold) can be obtained from third-party providers. Purchased energy creates indirect emis-
sions, whereas energy produced in-house generates direct emissions. Major emissions from
energy production are greenhouse gases, nitrogen oxides, sulfur oxides, and particle matter.
Emissions of greenhouse gases are believed to be contributors to the planet climate change
whereas nitrogen and sulfur oxides are responsible for acid rain.
The second impact on the use of energy is the contribution to the depletion of fossil fuels.
This is especially important for natural gas, which is a high-quality material that serves as
ideal feedstock for the production of chemicals (e.g., polymers) through synthesis. Natural gas
is a favorite fuel in the food industry because of its “clean” burning due to its high purity when
compared to other fossil fuels.
More on air emissions can be found in Chapter 8 and on energy in Chapter 11.
Water
With exception of facilities that process exclusively dry products, the food industry is an
intensive water user. Water has many applications such as cleaning and moving raw materials,
processing, chilling, cooling, in cooling towers, cleaning equipment, heat transmission, and as
ingredient food products.
Water is still not a problem in certain parts of the world, especially where surface water is
abundant or where aquifers are easily replenished. However, a water crisis in the future is
expected, so it is important to analyze the impacts of water use, which has three components:
