1 class periods of 45 minutes each
Large Groups
Systems Thinking
Students will discover potential careers in agriculture with a focus on the growing field of biofuel development.
Plants take in light energy from the sun and turn it into sugars. They store
the sugars in their roots, leaves, stems, flowers, and seeds. The energy in the
sugars makes them grow. When people or animals eat food made from plants
like soybeans, corn, and wheat, the sugars or carbohydrates give them energy.
In addition to the carbohydrates in plant parts, the seeds of plants contain
sugars, protein, and fats or oils.
The sugar or carbohydrates in plants may be distilled to make ethanol, a
fuel source for combustion engines. The seeds of plants have long been used
as an energy or fuel source for diesel engines. Peanuts and soybeans have
commonly been used to make diesel, but several other seeds high in oil have
been used to make biodiesel. Soybeans belong to the legume family--plants
that produce beans in pods. Legumes also take in nitrogen from the air and
release it into the soil. Nitrogen is important for good soil and healthy crops.
One soybean plant produces about 70 soybean pods with two to four beans
in each pod. The seeds are about the size of peas and may be yellow, green,
brown, black, or speckled.
Soybeans are native plants of Asia. Farmers in China have grown them
for more than 5,000 years. They use soybeans for food, fertilizer, animal feed,
medicines, and oils.
Soybeans were first grown in the United States in the early 1800s. They
were used as a source of food for humans and farm animals. During the Civil
War, coffee beans were hard to get. Soybeans were roasted and used to make
a coffee substitute. They were called coffee berries.
In 1904, George Washington Carver began studying soybeans. He discovered
that soybeans are a valuable source of oil, as well as protein. A 60-pound
bushel of soybeans produces 48 pounds of soy protein, 11 pounds of soy oil,
and one pound of hulls (the coatings of the beans). Henry Ford used soy oil
to make plastic parts for his cars. Farmers harvest the soybeans, which can
be eaten fresh in their pods or dried and roasted. They can also be broken
down into different forms. The beans are taken out of their pods by a machine
called a combine. The beans are then sent to a processing plant where they
are crushed, rolled into flakes, and mixed with a solvent to separate the oil and
protein.
The oil and protein can be made into many kinds of animal and human
foods, as well as products such as crayons, paint, glue, and plastics. Biodiesel
can be blended (mixed) with regular diesel, which is a petroleum fuel. Many
cities and school districts use a blend of 20 percent biodiesel and 80 percent
diesel in their buses. This is called a B20 blend. Using B20 reduces pollution
from the buses, making the air cleaner.
Most trucks, buses and tractors in the United States use diesel fuel. Diesel
fuel is made from petroleum, a nonrenewable energy source. Petroleum is
a fossil fuel; it takes millions of years to form under the ground, so we can't
make more in a short time. We use so much petroleum in the U.S. that we
have to buy two-thirds of it from other countries. When petroleum fuels are
burned in vehicle engines, they can pollute the air. If they spill onto the soil or
into the water, they can damage the environment for a long time. Petroleum
fuels are toxic and should be handled carefully.
Biodiesel is a fuel made from vegetable oils or animal fats. It is usually
made from soybean oil, but it can also be made from corn oil or used restaurant
grease and oil. If it is made from restaurant oil, it can smell like French
fries. Since biodiesel is made from plant and animal oils, it is a renewable fuel.
We can grow more plants in a short time to make more biodiesel. However,
with the demand for food and land resources increasing, some scientists are
looking at a "plant-like" organism--algae--as a possible fuel source. High oil
prices, competing demands between foods and other biofuel sources, and the
world food crisis have ignited interest in algaculture (farming algae) for making
vegetable oil, biodiesel, and other biofuels using land that is not suitable for
agriculture.
Algae are not plants, algae lack the structures that characterize land plants,
such as leaves and roots. Nearly all algae have photosynthetic capability and
algae cells contain both carbohydrates (sugar) and fats (oils). Scientists are
looking at efficient ways to grow algae for biofuels. Algae don't need fertile soil
and can grow or colonize in wastewater. Several types of algae grow well in
salt water. Algae use sunlight, little water, and produce oil in its cells 50 times
faster than regular crops. The biodiesel can be used in a car and can be used
to generate electricity. Among algal fuels' attractive characteristics: they do not
affect fresh water resources, they can be produced using ocean and wastewater,
and they are biodegradable and relatively harmless to the environment if
spilled.
How do you get oil out of soybeans? Soybeans are crushed and then using
hexane, a solvent, the oil is removed from the seed. If you crush soybeans
in a mill and then boil the meal, the oil from the seeds will float on the surface
of the water. How do you get the oil out of algae? It is similar to soybean oil
extraction; you remove the oil from dried algae chemically with hexane, or
mechanically using an expeller press or ultrasound. How much energy is in
oil? Conduct the following activity to measure the calories in vegetable oil.
How do you convert ml
to grams?
One gram of water is always
equal to 1 ml. But for other
substances, you need the
density. For example, iron's
density is about 7 grams for
each 1 ml. So if you had 1
ml of iron powder, it would
weigh about 7 grams.
1 ml of water = 1g, because
1ml of water weighs 1g
1 ml of iron = about 7 g,
since 1 cc of iron weighs
about 7 g