Environmental Engineering Reference
In-Depth Information
for instance, generates little solid waste because most of it is treated as by-products at
rendering plants; therefore, virtually no solids are wasted. An exception to this statement is
solids mixed with polymers that are recovered from flotation cells designed to remove
suspended solids and fat from wastewater streams. As a rule, these solids cannot be reintroduced
in the rendering process or used for other applications such as animal feed and are placed in
landfills.
In the vegetable-processing industry, wastes come from sorting, trimming, and peeling or
the extraction of juices from fruits vegetables. All these wastes—that in many cases are
considered by-products or coproducts—have use as animal feed.
The largest impact of solid food wastes that reach landfills comes from food preparation
and scraps either produced at home and or by the food service sector. These materials are
biodegradable and therefore compostable, but a difficult logistic and lack of composting
facilities make these materials more likely to reach a landfill than being composted. A more
comprehensive discussion of solid wastes is presented in Chapter 10.
Is a 100-percent sustainable food company attainable?
A 100-percent sustainable food company would be desirable, but unfortunately it is unrealistic
at the moment. The first road block to 100-percent sustainability is the lack of renewable
energy. There are many initiatives to produce renewable energy from wind, solar, and biomass
sources. However, it is far from being enough to satisfy the demand of the food industry and
the industries that support food production.
The second road block to attain 100-percent sustainability is the lack of ingredients and
packaging materials made from renewable resources. Many ingredients used by the food
industry are renewable based, but they are produced with nonrenewable fuels and with the use
of petroleum-based precursors and solvents.
The third road block is water use. During the processing phase, water use can be minimized
and water even reused if it is treated with membranes using renewable energy. However, water
use for crop irrigations is having a devastating effect on aquifers in many parts of the world.
One solution is switching to surface water, but the problem is that surface water is not available
in most places where fertile soils exist.
The fourth road block is the intrinsic nature of food production. Many emissions of
greenhouse gases such as nitrous oxide and methane come from the field where raw materials
are produced. Nitrous oxide resulting from livestock, production of nitrogen-fixing crops,
cultivation of high-organic content soils, and the application of livestock manure to croplands
and pasture are difficult to address. Methane from enteric fermentation, which is the main
emission from milk and meat production, can be minimized with better diets (Leng, 1993), but
it cannot be eliminated or captured.
So, the idea of zero emissions may be possible from the viewpoint of burning renewable
fuels in stationary systems where nitrous oxides can be captured, and because fuels are renew-
able the net carbon dioxide balance would be zero. But the idea of having zero emissions from
the production of raw materials is a more difficult proposition.
The fifth road block is lack of degradable packaging made from renewable resources. To a
great extent, secondary and tertiary packaging is made from cellulosic fibers. However, with
the exception of polylactide, most primary packaging still relies almost exclusively on plastics
made from nonrenewable fossil raw materials.
Polylactide is not the only plastic made from renewable resources, but it is the only one that
is price competitive with homologous petroleum-based polymers. However, polylactate is not
a direct replacer for all plastic packaging materials. Its use is mostly limited to food products
