CHAPTER 10
THE GEOSPHERE, SOIL, AND FOOD PRODUCTION: THE
SECOND GREEN REVOLUTION
From Green Chemistry and the Ten Commandments of
Sustainability, Stanley E. Manahan, ChemChar Research,
Inc., 2006
manahans@missouri.edu
10.1. The Solid Earth
Geosphere: All the rocks, minerals, soil and sediments that
compose the solid earth.
Geosphere connection to green chemistry
• Plants that provide most food for humans and animals grow on the
geosphere.
• Plants growing on the geosphere already provide, and have the
potential to provide much more, biomass for use as renewable
materials, such as wood, fiber, raw materials, and fuel.
• The geosphere is the source of nonrenewable minerals, ores, fossil
fuels, and other materials used by modern industrialized societies.
• Modifications and alterations of the geosphere have profound
effects upon the environment.
• Sources of fresh water are stored in lakes and rivers on the surface
of the geosphere, move by means of streams, rivers, and canals on
the geosphere, and occur in aquifers underground.
• The geosphere is the ultimate sink for disposal of a variety of
wastes
Physical Nature of the Geosphere
Solid inner core<liquid outer core<mantle<crust<soil
Crust consists of rocks made of minerals
• 49.5% O, 25.7% Si
• Mostly silicon oxides or silicates, such as quartz, SiO2, and
potassium feldspar, KAlSi3O8.
Igneous rock is solidified molten rock
• Undergoes weathering to produce secondary minerals.
• Clays are common secondary minerals, such as kaolinite,
Al2Si2O5(OH)4.
Human Influences on the Geosphere
Desertification in which normally productive soil is converted to
unproductive desert.
Usually in areas with marginal rainfall
As plant cover is destroyed, surface soil erodes away, surface water
is lost, groundwater in underground aquifers diminishes, fresh water
sources and soil accumulate salt, and eventually the land becomes
unable to support agriculture, grazing, or even significant human
populations.
Old problem
Desertification is reversible
• Recharge of underground water aquifers
• Maintenance of plant cover
• Genetic engineering of plants that grow under adverse conditions
10.2. ENVIRONMENTAL HAZARDS OF THE GEOSPHERE
Earthquakes consisting of violent horizontal and vertical movement
of Earth’s surface resulting from tectonic plates moving relative to
each other.
• Liquefaction of poorly consolidated ground during earthquakes
• Tsunamis from earthquakes
• The anthrosphere can be constructed to minimize the effects of
earthquakes.
Volcanoes due to the presence of liquid rock magma near the surface
• Can cause great loss of life
• Can affect weather and climate, such as occurred with the
astoundingly massive eruption of Indonesia’s Tambora volcano in
Indonesia in 1815.
Surface Effects on the Geosphere
Weathering is the physical and chemical breakdown of rock to fine,
unconsolidated particles.
Erosion occurs when weathered materials are moved by the action
of wind, liquid water, and ice.
Landslides occur when unconsolidated earthen material slides down
a slope.
Creep characterized by a slow, gradual movement of earth
Expansive soil
Permafrost
Sinkholes
10.3. WATER IN AND ON THE GEOSPHERE
Water commonly moves on the geosphere in streams or rivers
consisting of channels through which water flows.
Rivers collect water from drainage basins or watersheds.
Floodplains are subjected to periodic floods.
Efforts to control floods may be helpful, but also may be
counterproductive.
Snow, ice
Water in soil
River
Lake, impoundment
Groundwater aquifer
10.4. ANTHROSPHERIC INFLUENCES ON THE
GEOSPHERE
Human alteration of Earth surface is often harmful, but can be
beneficial.
Harmful effects include
• Aggravated flooding
• Landslides, such as from piles of mine tailings
• Acid pollutants from bacterial action on exposed pyrite, FeS2
• Filling and destruction of wetlands
Direct effects of humans on the geosphere
• Construction of dams and reservoirs
• Flattening whole mountain tops to get to underground coal seams
• Plowing natural prairies to grow crops
Anthrospheric Influences on the Geosphere (Cont.)
Indirect effects
• Pumping so much water from underground aquifers that the ground
subsides
• Exposing minerals by strip mining that weather to produce polluted
acidic water
Major effects of mining and extractive industries
10.5. THE GEOSPHERE AS A WASTE REPOSITORY
Municipal refuse in sanitary landfills
Methane from landfills
2{CH2O}  CO2 + CH4
(10.5.1)
Leachate from landfills
Minimization of the quantities of materials requiring sanitary
landfill
• Reduce at source
• Recycle wastes • Burn for fuel
Secure landfills for hazardous wastes
10.6. HAVE YOU THANKED A CLOD TODAY?
Good, productive soil combined with a suitable climate and adequate
water is the most valuable asset that a nation can have.
Areas that once had adequate soil have seen it abused and degraded
to the extent that it is no longer productive.
One of the central challenges faced by the practice of green
chemistry and industrial ecology is to retain and enhance the
productive qualities of soil.
Soil receives pollutants
• Direct, such as herbicides used to control weed growth
• Indirect, such as acid from acid rain
Soil Structure and Horizons
Soil
Soil is a term that actually describes a wide range of finely divided
mineral matter containing various levels of organic matter and water
that can sustain and nourish the root systems of plants growing on it.
Soil is the product of the weathering of rock by physical, chemical,
and biochemical processes that produces a medium amenable to
support of plant growth.
Healthy soil
• Contains water available to plants
• Has a somewhat loose structure with air spaces
Soil supports an active population of soil-dwelling organisms,
including fungi and bacteria that degrade dead plant biomass and
animals, such as earthworms.
Generally composed of about 95% inorganic matter, but some soils
contain up to 95% organic matter, and some sandy soils may have
only about 1% organic matter.
Soil Horizons
Soil horizons are formed by weathering of parent rock, chemical
processes, biological processes, and the action of water including
leaching of colloidal matter to lower horizons.
• Most important is topsoil.
• Plant roots take water and plant nutrients from topsoil
• Topsoil is the layer of maximum biological activity
• Rhizosphere where plant roots are especially active
• Relationships between plant roots and microorganisms in the
rhizosphere
Inorganic Solids in Soil
Silicates are the most common mineral constituents of soil, including
finely divided quartz (SiO2), orthoclase (KAlSi3O8), and albite
(NaAlSi3O8).
Other elements that are relatively abundant in Earth’s crust are
aluminum, iron, calcium, sodium, potassium, and magnesium
contained in minerals such as geothite (FeO(OH)), magnetite
(Fe3O4), epidote (4CaO•3(AlFe)2O3•6SiO2•H2O), calcium and
magnesium carbonates (CaCO3, CaCO3MgCO3), and oxides of
manganese and titanium in soil.
Soil parent rocks undergo weathering processes to produce finely
divided colloidal particles, particularly clays.
• These secondary minerals hold moisture and mineral nutrients,
such as K+ required for plant growth
• Can absorb toxic substances in soil, thus reducing the toxicity of
substances that would harm plants
Soil Organic Matter
The few percent of soil mass consisting of organic matter has a
strong influence upon the physical, chemical, and biological
characteristics of soil
• Holds soil moisture
• Holds and exchanges with plant roots some of the ions that are
required as plant nutrients
• Temperature, moisture, and climatic conditions significantly affect
the kinds and levels of soil organic matter
• Accumulates under cold, wet conditions in which soil stays
saturated with moisture
• Soil from tropical rain forests loses organic matter readily when
vegetation is removed.
Soil Humus
The plant biomass residues biodegraded by soil bacteria and fungi
losing cellulose and leaving modified residues of the lignin material
that binds the cellulose to the plant matter.
• Humification, residue is partly soluble soil humus
• Humin does not dissolve and stays in the solid soil.
Soil humus
• Strongly influences soil characteristics
• Strong affinity for water
• Exchanges H+ ion and acts to buffer the pH of water in soil (the
soil solution)
• Binds metal ions and other ionic plant nutrients
• Binds and immobilizes organic materials, such as herbicides
applied to soil
Water in Soil and the Soil Solution
Water is taken up by plant root hairs, transferred through the plant,
and evaporated from the leaves, a process called transpiration
• Most of the water in normal soils is absorbed to various degrees
upon the soil solids
• Waterlogging (saturation with water) is bad for soil.
• Soil solution transfers nutrients between roots and the soil solid.
10.7. PRODUCTION OF FOOD AND FIBER ON SOIL—
AGRICULTURE
Agriculture is the production of food and fiber by growing crops
and livestock.
Agriculture is very closely tied with the practice of green chemistry
in many ways.
• Fertilizers, herbicides, and insecticides are produced and applied to
crops and land in enormous quantities.
• Annual production of millions of kilograms of these chemicals
demands the proper practice of green chemistry and engineering.
• Conservation tillage, is in keeping with the best practice of green
chemistry and industrial ecology.
• Biomass produced by plants can be used as a renewable source of
organic matter as a raw material and fuel.
• Some plants are now being genetically engineered to produce
specific chemicals.
Agriculture and Green Technology
In many respects, past agricultural practices have not been very
“green.”
• Greatest incursion of the anthrosphere into the other environmental
spheres
• Cultivation of soil by humans has displaced native plants,
destroyed wildlife habitat, contaminated soil with pesticides, filled
rivers and bodies of water with sediments, and otherwise perturbed
and damaged the environment.
However domestic crops temporarily remove carbon dioxide from
the atmosphere and provide organic raw materials and biomass fuel
without any net addition of carbon dioxide to the atmosphere.
Plant Breeding
The basis of agriculture is the development of domestic plants from
their wild ancestors.
Humans selected plants with desired characteristics for the
production of food and fiber and developed new species that often
require the careful efforts of expert botanists to relate them to their
wild ancestors.
Modern plant breeding techniques
Modern Plant Breeding Techniques
Around 1900 the scientific principles of heredity started to be
applied to plant breeding.
• First “green revolution” in the 1950s and 1960s resulted in varieties
of rice and wheat, especially, that had vastly increased yields
• Techniques used included selective breeding, hybridization, crosspollination, and back-crossing
• Combined with chemical fertilizers and pesticides lead to much
higher crop yields
• India, for example, increased its grain output by 50%.
• Plants resistant to cold, drought, and insects further increased crop
yields.
• Increased nutritional values such as high-lysine corn
Modern Plant Breeding Techniques (Cont.)
Development of hybrids produced by crossing true-breeding
strains of plants
• Corn is especially amenable to hybridization.
Other factors in increased productivity include development of crop
varieties that resist heat, cold, and drought; irrigation; herbicides;
better tillage practices.
10.8. PLANT NUTRIENTS AND FERTILIZERS
Carbon, hydrogen, and oxygen in plant biomass from water and
atmospheric carbon dioxide
Calcium, magnesium, and sulfur are usually in sufficient abundance
in soil.
Calcium is commonly added to soil as lime (CaCO3), which
neutralizes soil acidity but also adds calcium to soil.
Soil}(H+)2 + CaCO3  Soil}Ca2+ + CO2 + H2 (10.8.1)
This process also adds calcium to soil.
Nitrogen, phosphorus, and potassium, are commonly added to soil as
fertilizers.
Aspects of the Nitrogen Cycle
Nitrogen cycle
• Atmosphere is 79% N2, but the N2 molecule is extremely stable
and not directly available to plants.
• Rhizobium bacteria growing on the roots of leguminous plants,
such as clover and soybeans, convert atmospheric nitrogen to
nitrogen chemically bound in biomolecules.
• NH4+ is produced when plant residues and animal feces, urine, and
carcasses undergo microbial decay.
• Lightning and combustion processes convert atmospheric nitrogen
to nitrogen oxides
• Ammonia manufacturing plants produce NH3 from atmospheric
elemental nitrogen and elemental hydrogen produced from natural
gas.
• Soil microbial processes oxidize ammoniacal nitrogen (NH4+) to
nitrate ion, NO3-, the form of nitrogen most readily used by plants.
• Microbial processes release gaseous N2 and NO2.
Synthetic Nitrogen Fertilizer
Production of fertilizer nitrogen starting with the catalytic Haber
process at about 1000 times atmospheric pressure and 500˚C. The
reaction is
N2 + 3H2  2NH3 (10.8.2)
Anhydrous ammonia can be applied directly below the soil surface
or applied as a 30% solution of NH3 in water.
• Held in soil as ammonium ion, NH4+
• Slowly oxidized by the action of soil bacteria using atmospheric O2
to nitrate ion, NO3-, which is used directly by plants.
Other forms of nitrogen include solid NH4NO3 and urea,
O
H
N
H
H
Urea
C N
H
Phosphorus Fertilizers
Phosphorus is an essential plant nutrient required for cellular DNA
and other biomolecules.
Phosphorus is utilized by plants as H2PO4- and HPO42- ions.
Phosphate minerals that serve as fertilizer phosphorus occur as
fluorapatite, Ca5(PO4)3F, and, Ca5(PO4)3OH.
Phosphate minerals are treated to make them more water soluble
2Ca5(PO4)3F (s) + 14H3PO4 + 10H2O 
2HF(g) + 10Ca(H2PO4)2•H2O (10.8.4)
2Ca5(PO4)3F(s) + 7H2SO4 + 3H2O 
2HF(g) + 3Ca(H2PO4)2•H2O + 7CaSO4 (10.8.5)
Potassium and Micronutrients
Potassium required by plants
• Potassium as the potassium ion, K+, is required by plants to
regulate water balance, activate some enzymes, and enable some
transformations of carbohydrates.
• Potassium for fertilizer is simply mined from the ground as salts,
particularly, KCl, or pumped from beneath the ground as
potassium-rich brines.
Plants require several micronutrients including boron, chlorine,
copper, iron, manganese, molybdenum (for N-fixation), and zinc.
• Soil normally provides sufficient micronutrients.
10.9. PESTICIDES AND AGRICULTURAL PRODUCTION
Most common agricultural pesticides are insecticides and herbicides
Recombinant DNA technology is having some significant effects
upon pesticide use.
• For example, splicing of genetic material into cotton, corn, and
other crops that cause them to produce an insecticide that is
generated by some kinds of bacteria.
• Breeding of genetically modified plants that are not affected by
herbicides, for example Roundup-ready soybeans
10.10. SOIL AND PLANTS RELATED TO WASTES AND
POLLUTANTS
Soil is a repository of large quantities of wastes and pollutants, and
plants act as filters to remove significant quantities of pollutants
from the atmosphere.
• Sulfates and nitrates from the atmosphere, including acid-raincausing H2SO4 and HNO3
• Gaseous atmospheric SO2, NO and NO2 are absorbed by soil and
oxidized to sulfates and nitrates.
• Soil bacteria and fungi are known to convert atmospheric CO to
CO2.
• Lead from leaded gasoline
• Organic materials, such as those involved in photochemical smog
formation, are removed by contact with plants and are especially
attracted by the waxy organic-like surfaces of the needles of pine
trees.
Potential Pollutants Added Deliberately to Soil
• Insecticides and herbicides added to soil for pest and weed control
• Chemicals from hazardous waste disposal sites can get onto soil or
below the soil surface by leaching from landfill or drainage from
waste lagoons
• Petroleum hydrocarbons, are disposed on soil where adsorption and
microbial processes immobilize and degrade the wastes. Soil can
be used to treat sewage.
• Leakage from underground storage tanks of organic liquids, such
as gasoline and diesel fuel
• PCBs contaminating soil in New York State from the manufacture
of industrial capacitors
• Analyses of PCBs in United Kingdom soils archived for several
decades have shown levels of these pollutants that parallel their
production.
• PCBs and similar pollutants in Arctic and sub-Arctic regions
believed to be due to the condensation of these compounds from
the atmosphere onto soil in very cold regions (next slide).
Distillation Process of Organohalides and Other
Organic Pollutants that Concentrate in Cold Regions
Degradation and Fates of Pesticides Applied to Soil
Many factors are involved in determining pesticide fate.
• Adsorption of pesticides to soil, strongly influenced by the nature
and organic content of the soil surface as well as the solubility,
volatility, charge, polarity, and molecular structure and size of the
pesticides.
• Strongly adsorbed molecules are less likely to be released and thus
harm organisms, but they are less biodegradable in the adsorbed
form.
• Leaching of adsorbed pesticides into water is important in
determining their water pollution potential.
• Effects and potential toxicities of pesticides to soil bacteria, fungi,
and other organisms
10.11. SOIL LOSS—DESERTIFICATION AND
DEFORESTATION
Soil erosion refers to the loss and relocation of topsoil by water and
wind action.
About a third of U.S. topsoil has been lost to erosion since
cultivation began on the continent and at present about a third of
U.S. cropland is eroding at a rate sufficient to lower productivity.
Erosion was recognized as a problem in the central United States
within a few years after forests and prairie grasslands were first
plowed to raise crops, particularly in the latter 1800s leading to soil
conservation measures.
Water erosion is responsible for greater loss of soil than is wind
erosion.
See erosion patterns in the continental U.S. on the next slide.
Soil Erosion Patterns in the Continental U.S.
Desertification
The ultimate result of soil erosion and other unsustainable
agricultural practices in relatively dry areas is a condition known as
desertification.
Desertification occurs when soil
• Loses permanent plant cover
• Loses its capacity to retain moisture
• Dries out
• Loses fertility so that plants no longer grow on it
Interrelated factors involved in desertification
• Wind erosion
• Water erosion (which occurs during sporadic cloudbursts even in
arid areas)
• Development of adverse climate conditions
• Lack of water for irrigation
• Loss of soil organic matter
• Deterioration of soil physical and chemical properties
Desertification (Cont.)
Desertification is actually a very old problem: Middle East, North
Africa, southwestern U.S.
Desertification is one of the most troublesome results of global
warming caused by greenhouse warming.
Deforestation
• Has occurred extensively in the United States, but is now being
reversed in New England
• Particularly severe problem in tropical regions
• Once destroyed, tropical forests are almost impossible to restore
because tropical forest soil has been leached of nutrients by the
high annual rainfalls in tropical regions.
• When forest cover is removed, the soil erodes rapidly, loses the
plant roots and other biomass that tends to hold it together, loses
nutrients, and becomes unable to sustain either useful crops or the
kinds of forests formerly supported.
Soil Conservation
The key to preventing soil loss from erosion as well as preventing
desertification from taking place lies in a group of practices that
agriculturists term soil conservation.
• Construction of terraces and planting crops on the contour of the
land (next slide)
• Crop rotation and occasional planting of fields to cover crops, such
as clover, are also old practices
• Relatively new practice of conservation tillage which involves
minimum cultivation and planting crops through the residue of
crops from the previous year using minimal quantities of herbicides
to deter weed growth until shading by crops prevents weed growth
Soil Conservation with Contour Planting and Terraces
Perennial Plants
The ultimate in no-till agriculture is the use of perennial plants that
do not have to be planted each year.
• Trees in orchards and grape vines in vinyards
• A successful grain-producing plant is one that dedicates its
metabolic processes to the production of large quantities of seed
that can be used for grain.
• Perennial plants put their energy into the development of large,
bulbous root structures that store food for the next growing season
rather than producing grain.
• Genetic engineering may eventually develop successful grain
producing perennial plants
Trees and Erosion
Among the most successful plants at stopping erosion are trees,
some of which grow back from their roots after harvesting.
• Wood and wood products are probably the most widely used
renewable resources.
• Hybrid tree varieties have been developed that are outstanding
producers of biomass.
• Wood is a renewable resource used for construction in place of
steel, aluminum, and cement, all produced by very energyintensive processes.
• Wood is about 50% cellulose, a carbohydrate polymer that is used
directly to make paper.
• Cellulose can be broken down chemically or biochemically to
glucose sugar which can be used by yeasts to generate ethanol and
protein.
Water and Soil Conservation
Conservation of soil and conservation of water go together very
closely.
The condition of the soil largely determines the fate of the water and
how much is retained in a usable condition.
Soil in a condition that retains water allows rainwater to infiltrate
into groundwater.
Measures taken to conserve soil usually conserve water as well.
10.12. AGRICULTURAL APPLICATIONS OF
GENETICALLY MODIFIED ORGANISMS
Recombinant DNA technology involves taking genetic material
from two different organisms and combining them so that traits of
both are displayed.
During the 1970s, the ability to manipulate DNA through genetic
engineering became a reality, and during the 1980s, it became the
basis of a major industry.
Direct manipulation of DNA can greatly accelerate the process of
plant breeding to give plants that are much more productive,
resistant to disease, and tolerant to adverse conditions.
In the future, entirely new kinds of plants may even be engineered.
Plants produced by this method are called transgenic plants.
Example: corn and cotton have been genetically engineered to
produce their own insecticide.
Could lead to a “second green revolution”
The Major Transgenic Crops and their Characteristics
Two characteristics of tolerance for herbicides that kill competing
weeds and resistance to pests, especially insects, but including
microbial pests (viruses) as well
The most common transgenic crop grown in the U. S. is the soybean,
of which about 89% of the crop was transgenic in 2006.
The percentage of U.S. corn that was transgenic in 2005 has been
estimated at 52%.
In 2006, it was estimated that 83% of the cotton grown in the U. S.
was transgenic.
Small fractions of the potato, squash, and papaya crops were
transgenic.
Insect-Resistant Transgenic Crops
Insect resistance has been imparted by addition of a gene from
Bacillus thuringiensis (Bt) that causes the plant to produce a natural
insecticide in the form of a protein that damages the digestive
systems of insects, killing them.
• Bt cotton has saved as much as a half million kilogram of synthetic
insecticides in the in the U. S. each year.
Herbicide-Resistant Transgenic Crops
The most common herbicide-resistant plants are those resistant to
Monsanto’s Roundup herbicide (glyphosate, structural formula
below):
O H H H O
HO C C N C P OH
H
H OH Glyphosate, Roundup herbicide
Virus resistance in transgenic crops has concentrated on papaya, a
tropical fruit that is an excellent source of Vitamins A and C and is
an important nutritional plant in tropical regions.
• Genetically engineered papaya resistant to ringspot virus
Future Transgenic Crops
Increased efficiency of photosynthesis, which is only a few tenths of
a percent in most plants
Development of the ability to support nitrogen-fixing bacteria on
plant roots in plants that cannot do so now
“Golden rice” which incorporates -carotene in the grain
• Two of the genes used to breed golden rice were taken from
daffodil and one from a bacterium!
Tomatoes that ripen slowly and can be left on the vine longer than
conventional tomatoes
Higher levels of lycopene, which is involved with the production of
Vitamin A, in tomatoes
Modification of the distribution of oils in canola to improve the
nutritional value of the oil
• Increased Vitamin E content in transgenic canola oil
Future Transgenic Crops (Cont.)
Decaffeinated coffee and tea
H3 C
O
O
C
CH 3
N
N
C
C
C
N
N
CH 3
C H
The caffeine
molecule
Coffee trees in which all the beans ripen at once
Improved transgenic varieties of grass and other groundcover crops
can be quite useful
• Tolerances for adverse conditions of water and temperature,
especially resistance to heat and drought
• Disease and insect resistance are desirable
• Reduced growth rates for less mowing, saving energy
Transgenic foods that produce contain vaccines against disease
• Cholera, hepatitis B, and various kinds of diarrhea
• Banana as a vaccine carrier