Unit Five – Lesson 3

Alternative Energy Sources for Agriculture

As Fossil Fuel sources are depleted, new energy sources will be in greater demand

Sources being promoted are: Solar Hydroelectric Tidal Wind Biomass Fuels Geothermal energy Nuclear

Solar Energy

Energy from the Sun is absorbed by the Earth and used as a fuel by virtually all organisms.

Image courtesy of NASA

Solar Energy – many uses

Drives the Water Cycle. Energy for Photosynthesis. Thermal Energy can be used for heating and

electricity. Stored in Plants … eventually forming fossil

fuels.

Solar Energy – Two types

Passive Sun’s energy is collected, stored, and distributed

within a dwelling, such as heating a home.

Simplest and cheapest solar energy form.

Examples for Agriculture: Drying of crops in the field Curing of various other Ag products

Solar Energy – Two Types

Active Uses devices to collect, store and circulate heat

produced from collectors. Used in areas that receive maximum sunlight. Can be used to heat water (in tubes), the water

then can be used as hot water, or as a source of heating heat for a building.

Solar Energy and Electricity

Photovoltaic cells, known as solar cells, produce electricity by transferring electrons from a positive plate to a negative plate.

Used mainly to produce power for homes, industry and space applications.

Lightweight and long-lasting. Agricultural uses include greenhouses, livestock

buildings, and as a hot water source. Electric fences, lighting, pumps, and irrigation can

also be run on photovoltaic systems.

Advantages of Solar Energy

Free and unlimited Clean Non-polluting Renewable resource Low maintenance Little noise and machinery involved

Disadvantages of Solar Energy

Not a constant source (clouds, rain).

Upfront equipment cost is high.

Note: over time, the expenses involved can often be recovered through savings in energy costs

Hydroelectric Power

Energy produced form the kinetic energy of moving water. Very old process, used in a diversified manner. In 1925, 40% of the world’s electricity was

generated by flowing water. It supplies about 24% of the world’s electricity

(2007) … generating the same amount of energy annually as 36 million barrels of oil.

Necessitates the building of a large dam across a waterway, creating a deep reservoir.

Water is directed through the dam with enough force to turn large turbine blades.

The turbines spin within a magnetic field, producing electricity.

Hydroelectric Power

Photo courtesy of UN Atlas of the Oceans

Advantages of Hydroelectric Power

Flood control. Unlimited power. Non-polluting. Creates recreation areas. Stores water for irrigation purposes.

Photo courtesy of YTEP

Disadvantages of Hydroelectric Power

Alters the natural animal and plant life of an area. Water is colder on the upside of a dam.

Fish are unable to swim upstream, interfering with reproduction.

Erosion problems are created on the down-side of the dam from water not replenishing the soil with nutrients.

Tidal Energy

Works similarly to hydroelectric power, using turbines.

Water is captured in a reservoir during high tide, then released during low tide.

A difference of 16 feet is needed between tides.

Wind Energy

Generated by large wind generators with rotating blades.

Has been in use for power since the 1870’s. Windmills, previously used for pumping water

and grinding grains, were converted to produce electricity long ago.

Today, modern aero generators are used.

Aero Generators: Two Types

Horizontal type Airplane-shaped propellers used in areas where

15mph winds and higher are prevalent.

Vertical type Blades are shaped similarly to an egg-beater, able

to be used at lower wind speeds.

Advantages of Wind Energy

Free and unlimited source. Non-polluting. Source of income for farmers on land without

interfering with livestock and crops. Can be used to pump water (irrigation).

Disadvantages of Wind Energy

Requires a large land area. Set-up is expensive and dangerous. May take up to 15 years for a wind turbine to

pay for itself.

Future of Wind Energy

As of 2007, there were 32 states producing wind energy.

Represents 1% of total energy produced in the US, and can “save” 28 million tons of CO2

Since 1980, the cost of wind energy equipment has decreased by 90%.

Biomass Fuels

Fuels formed from living or recently living organisms, including forest, agriculture, and food processing wastes.

Are renewable source of energy (also called biofuels)

Energy is released by burning, providing heat or chemicals or other fuels.

Biomass Fuels and Sewage

Sewage treatment facilities use bacterial digestion to treat water, releasing methane gas (natural gas). Methane is a valuable fuel used in heating. Grain crops can be used for ethanol production, a

type of alcohol used as a fuel. Oil-bearing plants (soybeans, algae, etc.) possess

chemicals similar to diesel.

Ethanol

Alcohol-based fuel. Made from corn, sugar, barley, wheat, and other

grains. Lower fuel efficiency than gasoline. Reduces harmful emissions compared to gasoline. E-10 is 10% ethanol and 90% gasoline for all

gasoline-powered vehicles. E-85 is 85% ethanol and 15% gas, used in “flex-

fuel” vehicles only.

Biodiesel

Made from vegetable oils ,animal fats, or recycled restaurant greases.

B20 is 20% bio-diesel and 80% petroleum diesel, can be used in most vehicles with minor modifications.

Can be produced domestically. Biodegradable product

Advantages of Bio-fuels

Renewable resource that reduces greenhouse gases.

Increase economic growth. Increase agricultural employment.

Disadvantages of Bio-fuels

May decrease plant diversity. May cause food prices to increase, due to grain

compatibility as a fuel. Additional land is required to produce large

amounts. Emits Nitrogen Oxides (acid rain) Must be transported by truck or rail. Does not flow well at low temperatures. May not be compatible with seals and gaskets in

older vehicles.

Geothermal Energy

Heat energy created within the Earth through the decay of radioactive elements.

Heat is enough to melt solid rock (magma). Areas where it can be used is limited to the

edges of tectonic plates and volcanoes. Water that comes in contact with the hot

earth produces hot springs and geysers. Steam can be collected and used to spin turbines,

producing electricity.

Advantages of Geothermal Energy

Able to heat greenhouses. Able to dry out meat products. Heat water for aquatic farms. Heat and cool homes (heat transfer units).

De-ice roadways. Successful in other countries (Ireland gets 50% of

it’s energy from this source).

Disadvantages of Geothermal Energy

Emits hydrogen sulfide gas (toxic). Produces excessive salt and mineral buildup

in pipes. Lack of adequate water to produce steam in

some areas. Areas where enough water and heat are

present represent only 10% of the Earth’s surface.

Nuclear Energy

Energy released from the controlled splitting of atoms (fission), producing heat.

Heat is used to produce steam, which in turn, powers large turbines that produce electricity.

As of 2006, 19% of the electricity produced in the US was nuclear.

Uranium is mined to use in producing fuel rods that undergo fission.

Nuclear plants are called “reactors” …there are two types:

Burner reactors Large rods made of Uranium 235 (called the

“core”) produce immense heat while submerged in water.

Other rods are (made from energy-absorbing materials) are lowered into the core to keep the reaction from getting too hot.

Breeder reactors Uranium 238 is used to produce Plutonium 239,

which is then used to power the core.

Nuclear Energy

Advantages of Nuclear Power

Large amount of energy is available. Could potentially reduce the reliance on fossil

fuels and foreign oil. Does not produce greenhouse gases, smoke,

or ash.

Disadvantages of Nuclear Power Mining uranium is not a clean process, and it

will eventually run out. Cooling towers at nuclear power plants

produce heated water and steam, that is returned to the environment – resulting in “thermal pollution” which alters existing wildlife ecosystems.

Breeder reactors could be used to produce weapons.

Nuclear plants do produce dangerous wastes that are problematic to store and dispose.

Thermal Depolymerization

Process was invented in the mid 1990’s. Uses heat (steam) and pressure to convert existing

trash into short-chain hydrocarbons, used as fuels. During the process, all disease-producing

organisms are destroyed. In 2003 a full-scale plant went into operation in

Carthage, Missouri, more are being constructed. Source: http://www.thermaldepolymerization.org/