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Unit 7 Working with Complex Food Systems
The remaining wastes from the digestive process are made up mostly
of fi ber and bacteria.
Metabolism
The small intestines function as a semipermeable membrane in
the body. This membrane allows nutrient components to be absorbed
into the blood and lymph systems. Nutrients are then carried to cells
all through the body. Cell membranes are semipermeable. Osmosis
controls the fl ow of nutrients and oxygen into cells. Osmosis also
controls the fl ow of waste products out of cells.
Metabolism is the physical and chemical reactions that constantly
occur within cells. Metabolism involves an exchange of energy. There
Where Does the Waste Go?
Food processors
have recycled long
before recycling was a
popular and encouraged
practice. Compared to
many other industries, the
food industry has low profi t margins. They
therefore do everything possible to minimize
costs while maximizing profi ts. Rather than
pay to dump waste, most fi nd ways to recycle
it. The following are some examples of how
waste is put to use.
Example 1. The Bush Bean plant in eastern
Tennessee has two unique “green” features.
The fi rst is the recycling of bean residue and
spillage. The bean residue is collected and
converted into methane gas. This “gassy” bean
by-product is burned to produce energy
that runs the boilers for cooking beans. The
second involves maintenance of the fi elds
around the plant. Rather than mowing, the
company has herds of beef cattle grazing in
the fi elds. A staff to manage the beef operation
was hired instead of spending that money
for staff, equipment, and fuel to maintain
and mow the fi elds. The result is cleared
fi elds that also produce an income.
Example 2. The corn used to make fuel
ethanol can be further processed into live-
stock feed. The parts of the corn that remain
after ethanol production are sold to make
nutrient-rich livestock feed. However, one
problem has arisen. Feed from ethanol
by-products results in manure that is more
odiferous and higher in phosphorus and
pathogens. Research is underway to decrease
the environmental impact (odor and pathogens)
of using corn by-products for feed.
Example 3. An example similar to the
corn by-products is the cottonseed pulp that
remains after the oil is expressed. This pulp
has been successfully recycled as animal
feed for decades. No odor or pathogen
problems have arisen.
Example 4. Each year 20 million beef
cattle are produced, creating 100 million
tons of manure. This by-product yields over
$200 million worth of garden-ready composted
manure. Sold under numerous brands, this
fertilizer can be found at local hardware
stores and garden centers, especially in
spring.