Energy Renewable Biomass and Waste

I. Energy

B. Renewable4. Biomass and Waste

• Biomass fuels include residues from logging; mill operations; processing of wood, pulp, paper, fiberboard; agricultural crops; livestock and poultry operations; food processing; demolition (urban wood waste)

• Waste fuels include combustible residues from industrial processes, municipal solid & liquid wastes

• Currently supplies ~15% of electricity production worldwide, more in developing countries

• Benefits• Readily available fuel• Inexpensive• Reduces waste stream

• Concerns• Emissions – Especially for waste combustion• Low fuel density• Technology still being developed (mainly emissions)

I. Energy

B. Renewable5. Geothermal

• Heat from deep within earth captured and used to turn an electric generation turbine

• Benefits• Inexpensive• Minimal environmental impact – Little pollution• Energy security – US has extensive resources

• Concerns• Limited use geographically• Not truly renewable (water injection can prolong life

of geyser field)• Geothermal emissions may include CO2 and H2S, as

well as various toxic compounds• Not economically viable in most areas• Geological risks

I. Energy

B. Renewable6. Fuel Cells

• Many types• All have membrane that only allows positively charged

particles to cross and external shunt that channels electrons

• Have been used for decades (powered manned space flights)

• Benefits• Low emissions• Highly efficient (up to 85% in some cases)• No moving parts – Enhances durability, simplifies

maintenance• Energy security – Can be produced anywhere

• Concerns• Technology still in its infancy• Energy input during processing• Risks of handling hydrogen and other fuels• Currently very expensive

www.fuelcells.org

I. Energy

B. Renewable7. Biofuels

• Bioalcohols• Biodiesel• Biogas

• Benefits• Renewable• Energy security• Reduced waste stream for raw materials• Reduced environmental impacts vs. other energy

sources• Concerns

• “Food vs. Fuel” – Elevated food prices• Not carbon neutral or carbon negative• Growing crops & processing for fuel requires land

and water• Pesticides may contaminate local aquifers• Emissions from biofuels (air pollution)

Gibbs et al. 2008

Righelato and Spracklen 2007

US EIA

I. Energy

B. Renewable8. Other

• Tidal energy• Wave energy• OTEC (Ocean Thermal Energy Conversion)• Fusion

II. Fresh Water

• Historically limiting factor in arid regions• 1940-1990

• World population more than doubled • 2.3 billion 5.3 billion

• Per capita water use doubled• 400 m3 person-1 year-1 800 m3 person-1 year-1

• Global water use increased fourfold• 2000: USA ~2000 m3 person-1 year-1 (~1450 gal day-1)

A. Current Status• In 1996, world human population using estimated 54%

of all accessible fresh water in rivers, lakes, aquifers• Many people predict disastrous consequences for

world’s fresh water supply in coming years• This potential disaster may have several causes

II. Fresh Water

A. Current Status1. Distribution

• Uneven compared to population• 75% of annual rainfall in areas containing less than

one-third of global population• Amazon River carries 20% of global runoff through

area containing 10 million people• Congo River carries 30% of Africa’s runoff through

area containing 10% of population• Uneven in space

• North America contains 19,000 m3 per person per year vs. 4700 m3 per person per year in Asia

• <10% of Mexico supplies >50% of annual runoff• Uneven in time

• India gets 90% of annual rainfall during summer monsoon season (Jun-Sep); runs off too rapidly for efficient use

II. Fresh Water

A. Current Status2. Usage patterns

• Agriculture – 69%• Industry/Energy – 23%• Domestic – 8%• Varies among regions and with development

• Africa – 88% for agriculture (irrigation)• Europe – >50% for industry• Japan – Industrial but uses lots of water for growing rice• Spain/Portugal – Arid; use water heavily for agriculture

• Personal use tracks standard of living• Africa – 17 m3 year-1 (12.3 gal d-1)• Asia – 31 m3 year-1 (22.4 gal d-1)• UK – 122 m3 year-1 (88.3 gal d-1)• US – 211 m3 year-1 (153 gal d-1)

• By 2020, water shortages likely in Ethiopia, India, Kenya, Nigeria, China (parts of China already face problems)

• Mexico City uses groundwater for 80% of municipal water supply

• Depletion exceeds aquifer recharge rate by 50-80%• Sinking of land in some areas Damage to buildings• City imports water to meet demand

II. Fresh Water

A. Current Status3. Contamination

• Numerous examples worldwide• Biggest source = Agriculture• Europe – Over 90% of rivers have elevated nutrient levels

from agrochemicals• Hungary – Nearly 40% of well fields contaminated• Developing countries – On average, 90% to 95% of all

domestic sewage and 75% of all industrial waste discharged into surface waters without treatment

4. Impacts• Nile River – Diverting water + retention of sediment

behind dams has caused fertile delta to shrink• Rhine River – Lost 8 of 44 fish species; 25 more

endangered • Lake Chad – Diversion + drought has caused shrinkage

from 25,000 to 2,000 km2 in 30 years Link• Aral Sea – Diversion for agriculture has caused severe

shrinkage, with environmental & health problems L1 L2

II. Fresh Water

B. Possible Solutions• World may have enough fresh water but

inadequate distribution mechanism• Long pipelines and movement of icebergs

have been proposed• Excessively expensive• Technological limitations

II. Fresh Water

B. Possible Solutions1. Improved irrigation efficiency

• Drip irrigation reduces losses from evaporation• Cuts water use by 40-60% compared to conventional

systems• Used on <1% of irrigated land worldwide but used

extensively in some countries (Ex – Israel uses DI on 50% of irrigated land)

• Low-energy precision application (LEPA) methods apply water directly to plants

• Can lower use of water and energy (20-50%)

2. Municipal conservation• Infrastructural losses can be substantial

• Ex – 40-70% of water lost in transit in 15 major Mexican cities (similar rates in India)

• Ex – Djakarta, Indonesia could cut water losses an estimated 20% by fixing leaky distribution pipes; would save ~12 billion gallons of water a year, enough to supply 800,000 people

• Higher price could encourage conservation• Ex – Bogor, Indonesia increased water prices 3-4x; average

household water use dropped by 30% in less than one year

II. Fresh Water

B. Possible Solutions3. Reuse of urban wastewater

• Use of treated wastewater for irrigation• Today, at least half a million hectares in 15 countries are

being irrigated with “gray water”

4. More water-efficient industry• Practiced in industrialized nations.• Amount of water needed to produce a ton of steel ranges

from 23 to 56 m3 in China, compared to an average of less than 6 m3 in US, Japan, and Germany

5. Desalination• 2010 – Over 20 billion gallons of fresh water produced

daily in ~15,000 facilities worldwide• Minimum cost = 0.2¢ gal-1

• Current methods of desalination driven almost entirely by combustion of fossil fuels

• Solar powered desalination plants produced only 1.4 million gal d-1 in 2009