Chapter 113 Leave No Trace

Sustainability

According to the World Wildlife Fund, in the 21st century, mankind’s footprint exceeds the earth’s regenerative capacity by 30%.² Wildlife populations have declined by one-third over the last 35 years² and humans are consuming resources at a rate that far exceeds natural regenerative capacity. Biodiversity has declined as species have been overexploited.² In 2005, the single largest human footprint was carbon in the form of carbon dioxide from combustion of fossil fuels; ambient CO₂ has grown more than 10-fold since 1961.² At the present rate, by the year 2030, mankind will need two planets to maintain the present level of consumption.² Two generations ago, mankind was an ecologic creditor. Today, two-thirds of our species live in countries that consume more natural resources than exist within their national borders. Therefore, these countries must depend on nations, often Third World countries, with fewer environmental restrictions for resources.

The earth provides food, water, material goods, and fuel. These resources have present economic value. Less salient and less marketable services include such things as nutrient recycling, soil formation, pollination, pest control, and water purification, as well as the aesthetic, spiritual, and recreational provisions of the earth. Some natural resources with market value (e.g., fossil fuels) have been regulated, whereas others (e.g., the atmosphere) have been undervalued or regarded as a common good and therefore have had little to no market oversight, leading to exploitation and overuse. Sustainability is the science of managing mankind’s footprint on Earth to achieve a balance between what we use and what the earth can replenish.

Energy

The world is powered by fossil fuels that release carbon dioxide (CO₂) when burned. CO₂ is naturally present in the atmosphere as a trace component; it is released as a product of respiration by plants and animals and in small amounts from volcanoes and geysers. It is one of the greenhouse gases, which serve to keep the earth warm by absorbing and emitting infrared radiation. Without greenhouse gases, the earth would be much colder. The three main greenhouse gases—CO₂, methane and nitrous oxide—affect the atmosphere as functions of their chemistry and rate of decay. Methane, released by fossil fuel combustion, waste dumps, rice paddies, and livestock, accounts for 14.3% of greenhouse gas emissions but is greater than 20 times more effective at trapping heat than is CO₂. Nitrous oxide from fertilizers and industrial processes accounts for only 7.9% of emissions but is about 300 times more effective at trapping heat, ton per ton, than is CO₂.⁷ In 1750, prior to industrialization, atmospheric CO₂ concentration was approximately 280 parts per million (ppm). By 2005, it had reached 379 ppm; the rate of increase from 1995 to 2005 was the highest in recorded history. More CO₂ in the atmosphere is generally felt to mean more greenhouse gases and a warmer planet. Carbon dioxide is the greatest contributor to global warming, accounting for, depending on the reference, 43% to 56% of total greenhouse gases.⁷ The single largest contributor to atmospheric CO₂ is consumption of fossil fuels (e.g., coal, oil, and natural gas) for energy in transportation, industry, and forestry.⁷

Oil is the most carbon-dense fossil fuel, whereas natural gas (methane) is the “cleanest” of the carbon-based fuels, because it has more hydrogen atoms per carbon molecule. For each unit of energy, methane produces 117 lb of emitted CO₂, compared with 164 lb released by burning oil. To achieve a similar amount of heat, one would need nearly three times more weight of wood, which would release 195 lb of CO₂. Coal burns the dirtiest, producing 227 lb of CO₂ to achieve the same unit of energy.¹ Although some of these fuels are used primarily and directly for energy, such as in natural gas stoves, fossil fuels are also burned in power plants to create electricity. Various sources of fuels are combusted or otherwise converted into heat to generate steam, which spins turbines that produce electricity. Electricity then enters the “grid,” a large network of power lines, power stations, and transmission subsystems, to be distributed to homes and businesses (Box 113-1).

BOX 113-1 The Grid

The turbines that generate electricity from coal, natural gas, biomass, nuclear, wind, and solar power plants must distribute that power from the generating facility to the end users. Many power plants are not located close to population centers, so they must transmit electricity via overhead (and occasionally underground) high-voltage transmission lines to substations closer to cities for voltage step-down and further distribution. Energy storage at the substations is inefficient, so electricity is best distributed in real time. A sophisticated system of controls is therefore necessary to ensure that electric generation matches demand. If supply and demand are mismatched, electricity generation and distribution can become overloaded, causing a blackout. To prevent this, generating and distributing stations are all interconnected in a “grid” or “power grid” to allow for redundancy in the system, creating a series of transmission triangles rather than a branching hub. These individual triangles are then connected regionally and nationally. The grid allows for generally uninterrupted electricity delivery through periods of high and low demand and high and low power generation, as can occur with intermittent renewable fuel sources. Finally, the miles of transmission lines of the grid act to pool and store electricity from various sources, both renewable and nonrenewable. Therefore, electricity drawn from the grid is mixed-breed.

The network nature of the grid is ripe for computer management to improve efficiency. A “smart grid” delivers electricity from suppliers to consumers controlled by two-way digital technology. Such a system could alert the consumer, via smart meter devices such as a glowing orb, to high-use periods, giving direct feedback to limit the electricity use during expensive peak demand periods. Alternatively, the system could automatically turn off selected high-demand appliances during peak periods, which can be cost and carbon saving, turning them back on as demand lessens. A smart grid can charge an electric vehicle at night, a time of low electricity demand. Renewable energy sources will need a smarter grid. As the world converts to renewable energy, which is mostly intermittent power, a smart system will be necessary to limit demand during peak periods. Some of this can be accomplished by pricing energy as a function of demand and allowing market forces to work.

A “home grid” extends some of these capabilities into the home to allow the individual homeowner to cut electricity cost and the individual’s global footprint. Alternatively, individual homes can generate their own electricity “off the grid” or sell surplus to the grid. Many municipalities, regions, and countries already have established a smart or smarter grid. To view the present national power grid structure, log on to http://www.eere.energy.gov/de/electricity_grid.html.

Worldwide, a majority of the electricity produced comes from coal. Coal combustion is the largest contributor to CO₂ worldwide, but its production and use damage more than just the atmosphere. Coal is extracted by underground, open surface pit, and “mountaintop” mining. In mountaintop mining, the debris from the mountaintop is deposited in the adjacent valley, destroying vegetation, soil, habitats, and the aesthetics of the landscape. Acid, along with heavy metals such as mercury, selenium, and arsenic, from this debris seeps into waterways and groundwater. Coal combustion is the largest source of human-made mercury pollution. Acid rain is produced by burning high-sulfur coal.¹

Power stations can use any type of fuel (uranium, solar energy, biomass, oil, or methane) to power turbines to generate electricity, or the turbines can be turned directly by water and wind power. Although oil and natural gas burn cleaner than does coal, renewable sources of fuel can turn turbines and create electricity, so once the infrastructure is in place, the fuel is essentially free. According to the International Energy Agency, an intergovernmental energy policy advisor founded in the oil crisis of 1974 and located in France, renewal energy sources currently have the technological potential to supply nearly 20 times the current global energy demand, but presently account for no more than 17% of global energy consumption.³ Biomass and hydropower provide less than 15% of global energy need, whereas wind and solar power fuel provide approximately 2%.

Renewable Energy

Renewable energies are essential contributors to the global energy menu, and have the potential to reduce reliance on fossil fuel and to mitigate greenhouse gases, thereby lessening man’s ecological footprint. Regions of the world differ in the type of renewable energy used for energy and electricity, but overall, hydropower is the global renewable energy source of choice for electricity, and biomass for energy production.

Biomass

Biomass is an advanced form of photosynthetic solar power and a promising renewable replacement for fossil fuels in power plants. The energy generating process is relatively simple chemistry. Biomass is mashed and fermented with yeast to make ethanol. Ethanol is then burned for fuel. Initially, food crops, such as corn, were regarded as ideal biomass fuel options. However, the fossil fuel demands of industrial agriculture negated the benefits of decreased automobile emissions. Corn was replaced by nonfood sources of biomass when the economic and social impacts of using food for fuel became obvious. Many sources of renewable (and sustainable) biocellulose work, including grasses (especially Miscanthus [elephant grass]), waste paper, corn silage, and bagasse waste from sugar cane production. One acre of sugar cane will produce 2500 L (650 gal) of fuel; 1 acre of corn will produce 1500 L (400 gal); and 1 acre of Miscanthus grass will produce 4750 L (1250 gal) of fuel. Soybeans can be used to make 174 L (46 gal) of biodiesel. Oil palms can be converted into 2300 L (610 gal) of biodiesel per acre.¹

Wind Power

Wind power is, like biomass, a form of solar energy, because atmospheric temperature differentials from the sun create wind. It is so abundant that it could fuel the entire planet five times over, and is the fastest growing renewable energy source. As an energy source, wind power has the advantage of being rapidly installed, aesthetic, and scalable to the needs of the locale. An average windmill can generate enough electricity to power 400 average American homes and a smaller windmill 11 to 43 m (35 to 140 feet) tall can pay for itself after 6 years. The United States, Germany, and Spain generate the most electricity from wind power; however, India and China may soon surpass these countries because of their current investments in wind farms. England boasts the largest offshore wind farm in the North Sea, where winds are strong and reliable.¹

A typical windmill stands 50 to 100 m (160 to 325 feet) tall and has blades that range from 27 to 45 m (90 to 150 feet) in length, making construction and transportation a challenge, especially for offshore wind farms. Wind farms are regarded as hazardous for birds. However, cats kill 3000 birds for every one struck by a windmill, and tall buildings flatten 19,000 birds for every windmill kill.¹ Despite this relative safety, engineers are perfecting sensors to halt windmill operation when birds are nearby. The largest drawback to wind power is its intermittency. Power is not generated if the wind doesn’t blow.

Solar Power

The sun radiates enough energy to the earth in 1 hour, were it to be captured properly, to power the entire planet for a year. Solar energy is the most common form used by persons trying to “live off the grid.” Capturing solar power can be challenging and is limited by clouds and darkness of night and is, by its nature, intermittent. Technically speaking, there are two mechanisms to harness solar energy. Solar rays on a large scale can be focused by curved mirrors to heat liquids that turn turbines in power plants. Alternatively, and usually on a smaller scale, photovoltaic cells can convert sunlight directly into energy using semiconductor devices. Photovoltaic cells consist of a thin layer of silicon atoms that release free electrons when exposed to solar energy. They work in the presence of intermittent sunlight and can be deployed in small clusters or in large arrays. Free electrons flow out of the photovoltaic cell as electrical current, which is converted to alternating current by an inverter for use in residential homes and other applications.

Solar power can also be harnessed in a passive manner by intelligent design of residential and commercial buildings. The orientation of the building can take advantage of winter sun and minimize summer glare. The roof can be colored to reflect or absorb intense heat and can serve as a solar water heater. Building materials, such as stone, can be chosen to absorb heat, whereas proper ventilation can circulate both cool and warm air to limit the use of fossil fuels.

Geothermal

Geothermal energy has enough potential stored energy to satisfy the world’s needs many times over, according to the United Nations World Energy Assessment Report.⁶ Geothermal energy creates virtually no CO₂ emissions and is not intermittent, which is an advantage over other renewable sources that rely on wind or sun. Geothermal activity is greatest where the tectonic plates meet, such as in the Ring of Fire surrounding the Pacific Ocean. In addition, there are other naturally occurring hot spots where magma has found its way to the surface and created springs and geysers. Both of these natural formations can serve as direct sources of hydrothermal energy, where natural steam is used to turn the turbines. There is the potential for geothermal energy in unsuspected locations. In many areas, the rock below the ground surface is hot but dry. If the rock temperature exceeds 149° C (300° F) and this bedrock is close enough to the surface to be cost efficient, water can be injected into the ground in an Enhanced Geothermal System, and the resultant steam used to generate electricity. For personal consumption, a homeowner can install a geothermal heat pump to reduce the cost to heat and cool a building. Basically, a hole is drilled 12 to 60 m (40 to 200 feet) below the surface, where the earth’s temperature is a stable 16° C (60° F). A loop of copper pipes is installed and refrigerant pumped from the house to circulate in the loop, exchanging heat from the home with the earth. In the summer, warm air in the home is absorbed by the refrigerant and then circulates underground to bring cool air back to the surface. The process is reversed in winter.