Carbon Adsorption

Adsorption is the process of removing chemicals from a solution by accumulating the chemicals on a solid surface. Engineers refer to this as the transition from an aqueous environment to a solid environment. Large wastewater treatment plants have more than one method for removing hazards from wastewater; adsorption supplements these treatments because of its efficiency and ease of use. Sustainable wastewater treatment plants, small rural plants on a strict budget, and sustainable homes act as ideal places to use adsorption for cleaning wastewater.

Three types of adsorbents, substances that adsorb materials from water, work in treatment: activated carbon, synthetic long-chain compounds called polymers, and silica-based adsorbents. Polymers and silicabased compounds are expensive, but inexpensive activated carbon has been important in wastewater treatment for many years. Activated carbon consists of any material with high carbon content, which is treated to increase its capacity to draw contaminants from water. Also important, activated carbon holds onto the contaminants and does not release them back into the water.

Makers of activated carbon use any of the following high-carbon materials as precursors: almond, coconut, or walnut hulls; wood; bone; or coal. The activation process contains the following two steps: (1) heating the material to 700°F (371°C) to burn off hydrocarbons and make a material called char; and then (2) activating the char by exposing it to steam and carbon dioxide to create a porous structure. The extensive pore system in the carbon greatly increases surface area and thus makes the material much more efficient as an adsorbent. Activated carbon tends to contain the following pore sizes:

1. macropores—greater than 25 nanometers (nm)
2. mesopores—greater than 1 nm and less than 25 nm
3. micropores—less than 1 nm

 Wastewater treatment systems use either of two types of activated carbon: (1) powdered activated carbon (PAC) that contains small particles (less than 0.075 mm diameter), or (2) granular activated carbon (GAC) that contains larger particles of about 0.1–2.4 mm diameter. Smaller particle sizes also increase the adsorbing surface area compared with large particles.

Carbon adsorption works by exposing the solid surface to a flowing liquid. Contaminants drift toward the solid-liquid interface located adjacent to the solid adsorbent. Contaminant molecules diffuse through this static interface and enter the particles’ pores where they attach to sites called available adsorption sites, which are spaces on the adsorbent’s surface that are unclaimed and available to catch and hold onto a contaminant. Because water flows in and around the adsorbent’s pores, the method is often called carbon filtration. A variety of chemical interactions create the force that holds a contaminant on the surface: charge, covalent bonding, hydrogen bonding, or van der Waals forces. Covalent bonds occur when two atoms share electrons, while van der Waals forces develop when adjacent atoms share a weak attraction to each other because of an electromagnetic field.

Carbon adsorption offers an inexpensive and easy-to-maintain water cleaning method for sustainable homes, especially for treating gray water. The carbon can be reactivated once it has filled up with contaminants and no longer has many available adsorption sites remaining. Reactivation uses the same process as that used to activate char, that is, heating. For home systems, homeowners can simply replace the activated carbon filter every six months to a year after installing it rather than reactivate a used filter.

Energy from Wastewater

Sustainable wastewater treatment involves the reuse of the process’s byproducts for the treatment plant’s operations. A typical wastewater treatment plant offers several options for generating energy or carrying out other conservation measures. Carefully planned wastewater treatment can provide the following benefits: (1) the natural flow of water due to gravity can act as an energy source; (2) methane and hydrogen production from anaerobic digestion serve as energy sources for powering the facility; (3) the reactions inside the digester produce heat that can be rerouted to other biological processes; (4) the treatment plant’s gray water may be reused for flushing toilets; and (5) nutrient-rich sludge exiting the digester serves for landscaping the facility’s grounds or may be sent to local farmers. In summary, in sustainable wastewater treatment, everything is used and reused to the maximum.

The wastewater industry resembles other industries today in trying to meet stricter pollution requirements while reducing energy use. Water and wastewater treatment in the United States uses only 2 percent of the country’s total amount of energy, but with concerns over fuel and energy costs the industry faces the need to build more sustainable operations. Electricity needs of wastewater treatment plants vary by the amount of incoming wastewater they treat each day and the concentration of waste in the water.

Sustainable wastewater treatment plants allow water to naturally purify and consume minimal energy for pumping water. Methane gas from the treatment plant’s anaerobic digester can provide some or all of this energy. The Earth purifies the water due to the soil’s ability to remove particles and bind to many organic compounds.

Sustainable practices in wastewater treatment provide some or all of the energy needs for running pumps for the aeration step and other pumps, heating, and lighting. Methane serves as the most efficient energy source for these purposes, helped to a smaller degree by hydrogen gas. Wastewater-to-energy plants recover methane in a three-step process that involves (1) dehydration, (2) gas cooling, and (3) removal of hydrocarbon compounds heavier than methane. This process results in pure methane of natural gas quality. Methane contains a heating value of 55.5 megajoules per kg of material compared with natural gas’s 53.0 MJ/kg. Other fuels do not provide as much energy as methane: gasoline (48.1 MJ/kg); home heating oil (45.5); coal (28.5 MJ/kg); and wood (about 15 MJ/kg). Wastewater-to-energy therefore holds exciting promise for leading the way in new waste-to-energy technologies.

Ecological Wastewater Treatment

Ecological wastewater treatment encompasses three control methods for keeping wastewater from harming the environment: odor control, methane control, and discharge cleanliness. Odors from gases like hydrogen sulfide emitted from anaerobic digestion do not harm human health but make the surroundings unpleasant for neighbors of treatment facilities. Anaerobic digesters help solve most of this problem, and methane collection devices over manure tanks also reduce odors. Methane collection as previously discussed in this chapter is a critical part of ecological wastewater treatment because it can have a meaningful effect on greenhouse gas levels. The third factor, discharge of cleaned water, represents the wastewater industry’s major responsibility and the U.S. Environmental Protection Agency (EPA) enforces strict laws on the quality that treated wastewater must achieve. The government expects treatment plants to keep the amounts of treated wastewater constituents within certain predetermined limits. The following table describes the constituents in wastewater that the EPA monitors to avoid harm to the environment. These constituents must be controlled within the EPA’s acceptable limits whether a treatment

 facility runs traditional wastewater treatment or wastewater-to-energy processes.

 Wastewater treatment methods offer the following advantages: (1) easy to install and use; (2) small energy demand by most methods; and (3) inexpensive, except for ozone disinfection, ultraviolet disinfection, and ion exchange.

Methane—Cow Power

Cattle, meaning dairy cows and beef animals, belong to a diverse group of animals called ruminant animals, or simply ruminants. Ruminants possess a four-part digestive system composed of a stomach similar to a human stomach and three additional chambers that carry out a different digestion than found in the stomach. Ruminants exist on a diet of fibrous plants that require a good deal of chewing to digest. These animals do this by swallowing partially chewed food, regurgitating it, chewing it again to further break up the pieces (called chewing the cud), and then re-swallowing the material. The smaller, chewed pieces move into the other compartments that contain enormous numbers of anaerobic bacteria and protozoa, especially the biggest compartment called the rumen. Rumen microbes degrade fibers into organic acids that the animal relies on for energy. As the microbes work they release methane, which the animal must constantly eliminate by belching or passing along to the large intestines. The methane drifts upward into the atmosphere and mixes with other greenhouse gases.

CO2 receives most of the blame for the crisis of greenhouse gases and global warming, but, in fact, other gases cause much more harm to the environment. Methane contributes about 20 times more to global warming than CO2. The EarthSave environmental organization has calculated that animal agriculture produces 100 million tons (91 million metric tons) of methane a year. Cattle produce about 20 percent of the methane emissions in the United States, and, unlike new methane-reducing technologies for factories and wastewater treatment plants, these cattle must keep producing methane as long as they live.

Environmental scientists have considered two divergent solutions to cattle methane: capturing the methane for energy or altering normal ruminant digestion to produce less methane. Capturing the methane from belching cows presents an understandably difficult task, so engineers have turned their attention to the large amounts of methane that come from cattle manure. Pacific Gas and Electric Company has embarked on a program to capture this “cow power.” Roy Kuga, its vice president of energy supply said, “With nearly 2 million dairy cows in California, there is great potential for the state’s agriculture and power sectors to work together to address the challenges of climate change.” Cattle have become a hot topic among environmental scientists due to their enormous production levels of a renewable energy source.

Cow power farms work by conveying the manure to covered tanks or lagoons. Gas collecting devices receive the methane as it rises out of the waste load and, with a small amount of processing, pipe the natural gas to an energy utility company’s distribution system. On the other side of the country, Central Vermont Public Service, an electric utility company, uses manure methane to fuel an energy generator and converts the output to electricity for its customers. A Vermont environmental planner Jason Bregman has predicted, “The next generation of renewable energy systems will seek out organic matter in municipal, commercial and agricultural waste streams as a relatively easy source of fuel to obtain and process energy.” Other states and many other countries have begun their own methane waste-to-energy programs.

Reducing the methane a cow produces requires adjustments to the cow’s diet. Grasses that cattle graze contain a stringy fiber called lignin that can only be digested with cud chewing and the action of the rumen’s anaerobes. Laboratories have begun to develop new grasses that contain less lignin so that grass-fed beef and dairy cows emit less methane. The Carnegie Mellon University engineer Christopher Weber explained to Discovery magazine in 2008, “Genetically modified grass could be an appealing solution. It could be more acceptable to the carnivores among us than meat grown in test tubes or giving up meat altogether.” The promise of adjusting cattle’s diets offers some promise, but it is still a long way from helping solve climate change. A more daunting obstacle comes from the fact that cattle are not the world’s only methane producers. The following ruminant animals all produce methane: alpacas, antelopes, bison, camels, deer, giraffes, goats, llamas, oxen, pronghorns, sheep, water buffalos, wildebeests, and yaks.

Methane use and methane reduction are two rapidly emerging technologies. If environmental engineers can design successful means of capturing methane for energy use, they will certainly help in advancing sustainable energy sources. Overall, methane will continue to be a problem in global warming.

Gray Water Reuse

Gray water is water that has been used for showering, faucet uses, and clothes washing, and it usually disappears down drains as a wasted resource. Sustainable wastewater treatment involves the recapture of gray water for additional uses, a process better known as water reclamation. These recovery systems do not collect kitchen sink water or toilet water because these can be health hazards due to the presence of disease-causing microbes.

Sustainable houses collect gray water in pipes that run separate from toilets and the kitchen sink. After collection, building designers have options regarding how and where the gray water will be best used. The three main options for gray water use are: (1) as irrigation water; (2) for flushing toilets; or (3) in the home’s fire suppression system.

Two new technologies may soon join the three main uses for gray water. The first involves the routing of gray water into wetlands constructed near the building to naturally degrade liquid wastes. These constructed wetlands work similarly to natural wetlands in which wastes move very slowly through the site so that plants and microorganisms have time to degrade the organic matter. Lori Ryker explained in her 2005 book Off the Grid, “The goal of a man-made wetland is to replicate a natural wetland’s ability to clean and filter water. A constructed wetland system’s selected plants filter gray water in a specific order, and then return the water to the earth, eliminating the need for a fully developed septic system.” The second technology uses very efficient filtration systems to make the water suitable for drinking, known as potable water. The following filtration technologies may soon produce drinking water for direct reuse as potable water: ultrafiltration in which filters contain extremely small pores to capture all contaminants; nanotechnology in which nanoscale materials act to clean or even sterilize water; and reverse osmosis in which water is forced through a fine membrane to clean out all impurities.

A sustainable home manages three different water sources: (1) rainwater, which is usually captured in a cistern such as the 60-gallon (227-l) size shown here; (2) gray water, which is wastewater from showers, sinks, and washers that is not expected to contain diseasecausing microbes; and (3) blackwater, which is wastewater from toilets, sinks, or any other source expected to be contaminated with disease-causing microbes. (Natural Rainwater.com)

Most houses that recover gray water today send the water to a holding tank that degrades waste in a manner similar to a septic tank. The cleaned water moves out of the tank by passive energy; it is pushed along by the force of new gray water entering the system. The cleaned water flows through a short series of baffles that prevent most of the dirty gray water from mixing with the cleaner water, and then the cleaned water goes through the outflow pipe. After completing this cleanup process, the two main current uses for gray water are garden irrigation or flushing toilets. Gray water reclamation does not need to be confined to houses; these closed-loop systems can work in large office buildings, schools, and manufacturing plants.

Anaerobic Digesters

An anaerobic digester is any equipment or site that holds waste materials in an oxygen-free environment so that anaerobic bacteria can degrade the wastes. On a wastewater treatment plant’s property, the digester is a large tank that holds several thousand gallons of liquid and semiliquid material. Wastewater digestion also takes place in a similar way in lagoons or ponds even though these places are exposed to the air. Though the upper layers of the water contain some dissolved oxygen, the deeper layers become less aerobic and more anaerobic. If the contents of an anaerobic digester or pond receive little mixing, oxygen does not penetrate the depths and so anaerobic bacteria work at their best.

Anaerobic decomposition occurs naturally in swamps, bogs, stagnant ponds, deep bodies of water, and waterlogged soils. The bacteria in these places degrade organic matter to the simplest of compounds, which allows the nutrients to be recycled. For example, amino acids degrade to carbon dioxide (CO2), methane (CH4), hydrogen (H2), and small amounts of nitrogen and sulfur compounds.

Digestion of organic matter—in nature as well as in a digester—takes place in three stages. First, aerobic bacteria degrade complex compounds such as starches, proteins, and fibers into smaller carbohydrates or peptides. A second group of bacteria use these compounds as food and produce organic acids as end products of their enzyme reactions. The organic acids all have in common a carboxylic group as part of their structure (COOH). This section of the molecule contains a carbon that is linked both to an oxygen molecule and to an oxygen-hydrogen complex, called a hydroxyl group. Examples of the organic acids produced in this step are acetic acid (two total carbons), propionic acid (three carbons), and butyric acid (four carbons). As a third and final step, anaerobic bacteria use the acids for energy and produce methane, carbon dioxide, and a small amount of other gases (hydrogen, carbon monoxide, hydrogen sulfide, and nitrogen).

Anaerobic digesters at wastewater treatment plants make fuel in the form of methane gas, which can be burned to release its energy. Many sustainable wastewater treatment plants use the methane to provide heat for the digester so that the entire process can continue. This is an example of a sustainable loop.

The methane and the other biogases produced by anaerobic digestion serve as an energy source that can be used to run the treatment plant or do other work. Burning one cubic foot of biogas yields 10 Btu of heat energy. The amount of methane in the biogas mixture affects the energy production because methane is the main energy source. Each percentage of methane results in 10 Btu, so that a biogas containing 65 percent methane produces 650 Btu per cubic foot. Very active anaerobic digesters can produce enough methane to run a treatment plant’s heating, refrigeration, and electricity. Anaerobic digesters therefore play a role as the main powerhouse when designing a sustainable wastewater treatment plant.

Methane cannot solve every environmental problem. For one thing, though methane can be used for making energy, it is also a predominant greenhouse gas that causes global warming. Sustainable wastewater treatment plants help reduce this problem by capturing all the methane emitted by a digester and using it, but methane come from additional sources in the world. Human activities that lead to methane production are waste treatment, biomass burning facilities, energy plants, and landfills. Methane also comes from natural sources: anaerobic soil and water bacteria, some vegetation, fossil fuel deposits such as coal mines and natural gas fields, and certain animals. Scientists have begun to realize in the past decade or so that the animal sources of methane contribute a significant amount of greenhouse gas to the atmosphere.

Kufunda Learning Village, Zimbabwe

Kufunda Learning Village in Zimbabwe, located near the capital of Harare, was created in 2005 by Marianne Knuth for the purpose of creating strong, healthy communities that are responsible for their own future. In addition to cultural growth, Kufunda has embarked on an exploration of technologies to meet its most immediate needs. Kufunda residents focus on building self-sufficiency in two main areas: agriculture and community infrastructure. Knuth explained, “We are a small group of people who have decided to create a learning village aimed at the creation of locally rooted solutions to community self-reliance challenges. A starting assumption for my work here is that people already know how to work in creative and self-sufficient ways, and that the challenge is to help them access that knowledge—and the self-confidence to act on it—generating concrete and often surprising results in the process.” In time, Kufunda’s residents hope they can transfer their knowledge to neighboring villages that wish to create similar self-sufficiency.

In the face of periodic political unrest, villages like Kufunda have a greater need for self- reliance, perhaps, than any other communities. Residents have begun to investigate the developmentment of ecological projects such as renewable energy, organic farming, ecological building, and composting toilets. The Kufunda Learning Village Web site has reported, “Ecological sanitation is a system that makes use of human excreta and turns it into something useful, which can be used to grow plants or trees. By now all the toilets at the village are of this type. Our simplest compost toilet can now be built for roughly 10 U.S. dollars—an important factor when working with financially poor rural communities.” Not only are Kufunda’s plans cost-effective, but they make every use of natural clean-running systems.

The Kufunda Learning Village has already begun to run its main electronic systems on solar power—the satellite Internet was the village’s first system to run on solar energy. Kufunda’s residents have an advantage over richer, more industrialized communities: They own no preexisting energy or waste management systems to tear down. The Kufunda Learning Village continues to find the best solutions to its specific environmental issues and, in the process, provides a good example of building efficient and simple technologies that foster sustainability.

Wastewater in Developing Countries

Numerous developing parts of the world contend with a high incidence of infectious disease because of poor drinking water quality and poorly functioning wastewater systems. Leaks and contamination of either system come from faulty or missing infrastructure, meaning distribution pipes, collection pipes, treatment facilities, and disinfection methods. Because of serious health threats to humans, many developing countries that already struggle with poor infrastructure make wastewater treatment their priority. The World Health Organization (WHO) has warned that the problem will get worse in developing countries. Because these places have clean water shortages, wastewaters substitute for treated water for irrigation, fishing, and cleaning clothes.

Sustainable wastewater treatment refers to the production of energy from the wastewater treatment process. This method of energy production offers an opportunity for developing countries for two reasons: the efficiency in converting biomass’s chemical energy to other forms of energy, and low cost compared with other energy technologies. Sustainable wastewater treatment therefore relieves two problems that plague many developing parts of the world: energy and waste management.

Nonindustrialized countries have a great need for inexpensive, easyto- build waste treatment technologies. Some of these countries have adopted inventive and sustainable solutions to waste treatment. The Internet reporter Andrea Millar provided an example in a 2008 article: “A Kenyan jail has confronted the issue of its waste production by creating a sustainable wastewater treatment facility staffed by inmates and designed by both local and international organizations. Rather than employ hightech engineering, the bulk of the [treatment is] handled by natural processes in the facility’s man-made wetlands. Acting as a vast filtration system, the sustainable processes of anaerobic microbes convert human waste into materials for biogas and water for use on the jail’s vegetable fields.” Millar’s example illustrates a situation in which wastewater handling is done in a manner that requires no energy input at all other than a small amount of manual labor.

The next step in sustainable wastewater use involves methods for producing energy. Treatment plant anaerobic digesters offer the most efficient way to make energy-containing methane gas, but some villages may not have the funds to build a new plant from the ground up. A waste treatment pond offers an inexpensive option because it contains conditions similar to those found inside treatment plant anaerobic digesters. Treatment ponds contain anaerobic activity in the deepest parts of the pond where aerobic bacteria have depleted the oxygen. Anaerobic bacteria live naturally in these types of places so setting up a wastewater treatment pond carries little expense. Methane gas drifts up from the bottom of the pond and can be captured and piped to an energy-generating plant so that the pond produces energy rather than consumes it.

Some ponds tend to grow heavy mats of algae on the water surface. Rather than spend efforts to get rid of the algae, workers remove the algae layer and add it to a small anaerobic digester to produce heat. In fact, treatment ponds provide the same advantages of mechanical anaerobic digesters: They help in waste management and treatment and recycle nutrients. One disadvantage of ponds compared with closed anaerobic digesters comes from odors emitted by the bacteria in their normal digestion of organic matter. The odors do not cause a health problem, but smell unpleasant.

R. Otterpohl wrote an online article in 2007 for the Swiss Federal Institute of Aquatic Science and Technology describing new processes for wastewater treatment that seem suited for developing countries: “The conventional wastewater management concept, consisting of a waterborne wastewater collection system leading to a central treatment plant, has been successfully applied over many decades in densely populated areas of industrialized countries . . . However, the appropriateness of this model in the context of developing world cities must be questioned, given the urgent need for affordable, sustainable infrastructure. During the last decade, various researchers and institutions, including the World Bank, have started to consider the decentralized wastewater management approach as an alternative to conventional centralized systems, but these approaches have struggled to gain acceptance.” Part of the resistance comes from the worry that treatment plants intended for the use of only one or two towns might not be as efficient to run as big centralized wastewater treatment plants. But small, decentralized treatment plants also offer advantages to communities, as follows:

1. smaller treatment systems tailored to a community’s specific needs
2. experimentation with different wastewater treatment methods
3. reduces accidents that may occur in long-distance wastewater shipment
4. increases opportunities for treated water reuse
5. makes incremental changes and improvements manageable

 Today, the Engineers Without Borders-International (EWBI) organization helps communities in developing regions adopt new technologies to improve their health, income, and lives. The EWBI stresses sustainable methods in energy use, water management, and native natural resource conservation. EWBI engineers and other volunteers help disadvantaged communities build needed structures and teach residents basic engineering skills for future projects. The founder of the Engineers Without Borders-United States, Bernard Amadei, revealed his view of the organization’s purpose in a 2007 interview with the correspondent Spencer Michels. Amadei described San Pablo, Belize, as a village “where I noticed a lot of little girls, young girls, who were carrying water—that was their job—from the river to the village, back and forth, back and forth. And as a result, they could not go to school. It broke my heart. And I decided I was going to do something about it.” EWBI develops projects with a community, not for it, so that the community solves its own environmental engineering needs. EWBI helps train residents how to build a structure, how to fix it, and how to keep it running.

Developing countries therefore have options for the type of wastewater treatment they choose. Because of the health needs for safe wastewater management and the need to produce inexpensive energy, sustainable wastewater systems are ideal for developing parts of the world.

The Energy-Water Connection

Environmental engineers apply the first and second laws of thermodynamics in every project they plan and develop. The first law of thermodynamics states that energy can neither be created nor destroyed. The form of energy, however, can change. For example, the motion energy inside a turbine changes to electricity. The second law of thermodynamics states that energy flows from a region of high concentration to a region of lower concentration, much as water flows downhill. By the second law of thermodynamics, water at the top of a waterfall contains a high concentration of energy. As it pours over the waterfall and fills a basin, the energy concentration changes. The water that settles into the basin at the bottom of the waterfall holds a lower concentration of energy. This principle has been used for centuries to power daily operations.

Flowing water illustrates another component of energy—potential energy versus kinetic energy. Water at the top of the waterfall before flowing over the edge contains potential energy, that is, a form of stored energy. As the water pours downward it loses potential energy and gains kinetic energy, the energy of motion. All of the different types of energy

Operations that generate energy from flowing water—hydroelectric dams, wastewater treatment plants, mills— rely on capturing water’s kinetic energy. Water at the top of the waterfall in this diagram holds high potential energy, but after it reaches the bottom of the waterfall it contains low potential energy. Power plants take advantage of this transition.

in the solar system can be classified as either potential or kinetic, as the following table shows.

Energy can change from one type to another, as mentioned, illustrated by the following example:

1. A racehorse converts the chemical energy in hay to motion energy.
2. A person converts electrical energy to thermal energy by turning on an oven.
3. Plants convert radiant energy from the Sun into chemical energy through photosynthesis.

Water’s use as an energy source throughout history has usually been as motion energy. Wastewater treatment plants can take advantage of the natural flow of water to power operations, but wastewater offers an additional energy source in the form of biomass. Biomass is organic matter in wastewater that comes from plant and animal wastes. In the wastewater treatment industry, biomass represents a source of chemical energy that can be converted to other forms such as thermal energy.

Sustainable Wastewater Treatment

Hydrology, the science of water systems, has always been a central part of environmental engineering. Ancient societies used flowing water as a means of travel, a conveyance for moving timber and other goods downstream, and a waste disposal system. During the growth of civilization, people learned that bodies of water held a significant amount of force. Villages constructed mills next to fast flowing rivers to let the force of the water supply power for the milling operations. The next generation built enormous dams to control the force of water that powered turbines and produced electricity. Water systems will become part of new energy-generating systems in sustainable communities in the near future, mainly because water avoids the use of nonrenewable and pollution-causing fossil fuels.

Wastewater treatment follows a standard process that turns raw sewage into disinfected water safe for return to the environment. Almost all modern wastewater treatment plants conduct the following steps to treat wastewater: (1) wastewater passes through screens that remove large solids; (2) wastewater enters a grit chamber where heavy wastes settle out of the water by gravity; (3) water enters a larger settling tank where light, small particles slowly settle out of the water; (4) the water enters an aeration tank containing aerobic (oxygen-requiring) bacteria that digest organic substances, aided by a constant bubbling of air through the contents; (5) the water enters another settling step and then passes through a filtration tank, which removes very fine particles; (6) disinfectant kills the bacteria in the water; and (7) the treated water discharges into the environment.


Pipes carry much of the heavy organic sludge that collects in the settling tanks to another tank called an anaerobic digester. This digester contains anaerobic (requiring the absence of oxygen) bacteria that slowly degrade the heavy sludge and produce methane and small amounts of other gases. The wastewater treatment industry calls the methane biogas, and both biogas and solid biomass serve as energy sources produced by wastewater treatment.

Landscape Design Skills

The landscape design profession combines art and science for the purpose of planning and shaping the land that surrounds a structure. Ecological landscape design focuses on meeting a customer’s needs while also planting trees and plants, gardens and ponds, and other features that create a relationship between the building and the environment. Landscape designers must understand many of the same principles as environmental engineers, that is, hydrology, geography, topography, and climatology. The landscape designer, however, emphasizes the artistic use of plants, water, and land. The following table summarizes the basic skills that landscape designers call upon when they develop a new but natural look for a parcel of land.

Environmental landscaping begins with a plan agreed upon between a house’s architect and the property’s landscaper. A landscape designer also gives input to this process in order to create a visual meaning to an entire property. For instance, a country cottage would look out of place nestled among large rock formations and towering pines, and the property would be further confused by a modernistic landscape design including sculpted shrubbery and enormous fountains. Landscaping in harmony with nature eliminates most of these pitfalls: Nature always produces the best balance between art and design.

The landscape design process entails the following six steps:

1. Develop a design for a given parcel of land.
2. Conduct a site analysis to assess existing tree and plant life and physical features.
3. Assess the house design, landscaping objectives, and the residents’ desires.
4. Locate areas of the property that will be designed.
5. Create design plans for those individual areas.
6. Select the plants to be used and plant them in the designated areas.

 In order to carry out the tasks listed here, landscape designers depend on strong skills in horticulture. In this way they help eco-landscapers select plant life that blends with the following factors: local climate and any microclimates; soil conditions; wind and storm incidence; and potential freezing or drought. Landscape designers today also design biodiversity gardens and edible gardens.

America’s Scenic Byways

Since 1991 the U.S. Department of Transportation (DOT) National Scenic Byways Program has designated specific roads that lead to archaeological, historical, cultural, natural, recreational, or scenic locations. The DOT has so far designated 125 such roads in 44 states. All of the scenic byways encourage travelers to gain greater appreciation of the land and its local trees, plants, and wildlife. Because scenic byways often call attention to nature, they seem to be a perfect place to adopt ecolandscaping. But heavily traveled roads have also caused harm to biodiversity by breaking up habitats, blocking migration routes, and killing wildlife in road accidents. Current and future scenic byways hold an important opportunity to establish ecologically friendly methods to construct and maintain popular roads.

Scenic byways range in rustic quality from the Beartooth Highway that meanders through Montana’s mountains and forests to Delaware’s Brandywine Valley Scenic Byway that travels past large estates and magnificent botanical gardens. Regardless of the terrain that a scenic byway traverses, the program ensures that all portions of the highway minimize the presence of billboards, telecommunications towers, fast food restaurants, or other clutter. One goal of the scenic byways program involves saving open space, and keeping human activities away from the roads helps preserve open space. In many instances, scenic byways probably provide some people with a look at nature that they would otherwise miss entirely in their urban lifestyle.

Walkways and Driveways

Rainfall that seeps into the earth receives cleaning as it percolates past soil particles that remove chemicals and microbes. The water then trickles downward into natural aquifers that serve as underground reservoirs for clean drinking water. When communities pave over the ground for roads, driveways, and parking lots, rainwater can do nothing but rush downhill into streams and then to wastewater treatment plants. This event has two drawbacks: Rainwater does not become available for plants and aquifers, and the extra volume of water requires extra energy consumption by wastewater treatment plants. Stress put on treatment plants can be significant in heavy storms, and the incidence of drinking water contamination increases when storms overtax local wastewater treatment facilities. For these environmental and health reasons, permeable pavements offer a useful way to manage and conserve water.

Porous surfaces act as one of the best ways to reuse rainwater and irrigation water. They also reduce runoff to streams. (A) An ecological garden uses stones to create a pathway that allows water to enter the soil. The gardener has planted thyme between these stones. (Kurt Lawton) (B) A pebble driveway helps in water recycling much more than a paved driveway. (Bushnell House)

A permeable pavement is any material that provides pedestrians or vehicles with a strong surface but also allows water to drain through rather than run off the surface. Landscapers select from five main types of permeable pavements, described in the following table.

Permeable pavements must be selected with the soil conditions in mind. For example, clay soils do not drain well and have a tendency to turn to mud in heavy rains. Areas with a very high water table, meaning the area’s natural groundwater storage is close to the surface, present the opposite problem: Permeable materials allow too much water to enter already soaked conditions. Even the best-designed permeable pavements can clog and may need extra maintenance to keep them open.

Microclimates

A microclimate refers to a specific small area that has a climate different from the larger area around it. Eco-landscapers who work in regions that have many diverse microclimates must understand these differences in

Xeriscaping incorporates the best techniques for reducing water waste; xeriscapes often occur in very hot, dry climates. Irrigation covers any area that needs extra water, but it does not waste water on drought-resistant plants. Porous materials for driveways, walkways, and patios allow rainwater to run into the ground, as does the replacement of lawn with gravel.

order to select the best plants for a particular parcel of land. Some microclimates spread over several acres, but other microclimates are so distinct, they cover no more than a half-acre.

 The U.S. Department of Agriculture (USDA) publishes a “Plant Hardiness Zone Map” that shows North America divided into 21 distinct climate zones and helps landscapers and gardeners understand their unique growing conditions. Each different zone on the map contains conditions suitable for certain plants, and landscapers are wise to select plants that do best in these zones. But even within such discrete climate zones, much smaller microclimates often exist. The San Francisco Bay Area in California is a champion of sorts in microclimates: It contains 20 major microclimates and perhaps hundreds of small microclimates across its nine counties. In less than an hour, a person can drive from a hot, dry 100°F (38°C) climate to foggy and windy 50°F (10°C) conditions. During that journey, the driver will likely pass through rain, sunshine, and varying degrees of heat and cold. The San Francisco Chronicle writer Harold Gilliam explained in 2001, “The reasons for this extraordinary variety of weather lie deep in the geologic past—in the clash of tectonic plates. The Pacific plate of the Earth’s crust, moving eastward over the eons, smashed into the edge of the North American continental plate, prying it up into monumental chains of mountains, including the Sierra Nevada, and, much later, California’s coast ranges. It is this rumpled landscape, this hill-and-valley topography, this heterogeneous diversity of landforms that give the Bay Area its multiple climates, microclimates, and submicroclimates.” Each eco-landscape therefore consists of a design best suited to its microclimate.

Environmental engineers must understand geography and climate when seeking energy efficiency because these things contribute to microclimates, which in turn influence the efficiency of buildings and landscaping. The following list summarizes the factors that engineers consider when working with a microclimate:

1. path and intensity of sunlight
2. wind and rain directions
3. wind forces
4. barometric pressure patterns
5. morning, midday, and evening temperature and humidity
6. coldest and warmest temperatures by season
7. cold air drainage
8. soil evaporation rates and tree transpiration rates
9. bodies of water that absorb daily heat and moderate temperatures
10. north- or south-facing slopes
11. soil composition, chemistry, and moisture

 Microclimates and all the many factors they encompass explain why environmental engineers require training in diverse sciences in order to work within the natural boundaries of nature.

Rainwater Harvesting

Rainwater harvesting consists of the collection of rain in rooftop or ground vessels so that the water can be used in irrigation when needed or shunted to a safe water source for indoor use. Collected rainwater, along with gray water and reclaimed water, represents an alternative water source that helps reduce overall household water bills by 25 percent. Gray water is the excess water that runs into household drains connected to sinks, showers, bathtubs, and washing machine rinse cycles. (Blackwater comes from the same sources, plus toilets, and represents any wastewater expected to contain disease-causing microbes.) Water conservation systems pump gray water to holding tanks for later use in irrigation. Reclaimed water is water that has been treated for uses other than drinking, such as treated wastewater from dishwashers.

Rainwater collection systems use gravity to do the work, making these systems easy to use and inexpensive. Rainwater collects into large cisterns, barrels, or rooftop tanks connected to a downspout that carries it to a holding tank on or under the ground. The few precautions that should be taken in managing rainwater collection systems are the following:

1. a cover to prevent entry of animals or mosquito breeding
2. fencing or other security measures to prevent small children from falling in
3. state-by-state differences in laws regarding the use of rainwater

 Alternative water sources additionally play a role in xeriscaping by making use of almost every drop of water in an area to both aid the environment and conserve water use and costs.

Biodiversity Gardens

Land in temperate climates supports various gardens such as ornamental flowers, vegetables, herbs, or cacti. A biodiversity garden acts as another specialized type of garden that helps maintain diversity in nature. Biodiversity gardens contain plants selected to provide habitat, shelter, or feeding for reptiles, amphibians, insects, birds, small mammals, and even invertebrates and microbes. In some urban neighborhoods these gardens may present one of the few places where a healthy ecosystem can function.

In addition to providing for native plant and animal life, biodiversity gardens can serve a role in rescuing plant species that are slipping toward extinction. Two hundred years ago farmers grew a large variety of vegetable plants and fruit trees, but over time commercial farms reduced the number of varieties to make packing and shipping easier. Growers prefer plant and fruit varieties that mature quickly, resist bruising during shipping, and have a long shelf life. In the process of targeting these traits, many thousands of other varieties have become increasingly rare. The Public Broadcasting System (PBS) reported in 1998 that to save plants with a long history in North America, called heirloom varieties, “an increasing number of dedicated gardeners are growing these threatened plants and sharing the seeds with others. These ‘seed savers’ have rescued hundreds of varieties . . .” The naturalist Craig Tufts of the National Wildlife Federation explained in the PBS show, “When people open their eyes, they can be amazed at what they can find in their own backyards.” Biodiversity gardens offer an excellent way for a household to observe nature.

Planning and building a biodiversity garden adheres to the following steps:

1. Explore local open space and determine the types of bushes, shrubs, and plants that grow there.
2. Seek a natural location to plant the garden in a place where it will attract wildlife—near ponds, streams, meadows.
3. Plan vertically as well as horizontally by selecting climbing plants such as ivy or creepers or small trees and build a trellis if needed.
4. Provide water in a ground-level space and also in a raised birdbath.
5. Include plantings that provide hiding places for birds, reptiles, and small mammals.
6. Substitute organic fertilizers for chemical fertilizers and eliminate use of chemical pesticides.
7. Install raised nest boxes for birds and install nearby bat boxes.
8. Minimize trimming and clipping, but water often.

 The Royal Horticultural Society headquartered in London, England, suggests that the best way to assess whether a garden contributes to biodiversity is by watching for birds, bees, and butterflies. Birds indicate that the garden offers nectar, pollen, seeds, and insects and may possibly provide adequate nesting space for a new family of hatchlings. Birds also supply a food source for foxes and hawks. Birds and bats additionally act as effective insect pest control. Honeybees and bumblebees indicate that flowering plants and trees are breeding and producing pollen and nectar. The presence of other insects such as hoverflies and ladybugs indicates that pest control is working because these species eat harmful insects such as aphids. Butterflies contribute to the garden ecosystem because their larvae provide a protein source for birds, small mammals, and other insects.

 A good rule of thumb in answering the question of how well a biodiversity garden helps nature is to watch or listen for a variety of insect, reptile, amphibian, bird, and mammal life. Daytime and nighttime activity by a wide variety of species assures that the diverse plantings have successfully provided a space for nature to thrive.

Soil, Water, and Lawns

Natural ground cover vegetation such as wild grasses, clover, weeds, and small shrubs helps stabilize the land. Ground vegetation attracts wildlife that replenishes the soil with nutrients at death or by preying on other animals, which leaves body parts on the ground. Some wildlife aerates soil by rooting in search of prey or digging burrows. Natural ground vegetation and trees with strong root systems also conserve water by slowing runoff and evaporation. Despite all the benefits of natural vegetation, many people love the look of a yard blanketed with a green and trimmed lawn, called turfgrass. In some parts of the United States, the perfect lawn can be maintained only through extensive watering, fertilization, and chemicals.

Why do people continue to desire homogeneous expanses of lawn that look nothing like the vegetation that grows in nature? The British geog-

People waste thousands of gallons of water each year. Clean freshwater is a natural
resource that should be conserved like all other natural resources. Building designs and
plumbing devices are available to reduce water waste and in some cases to reuse gray
water, the wastewater from showers, sinks, and washers. Gray water can then be used
for landscape irrigation.

rapher Dennis Cosgrove suggested in his 1988 book The Iconography of Landscape that the desire for lawns rather than natural growth is a psychological choice based on how nature was depicted in the arts for centuries. For instance, European landscape paintings from the 17th century show natural land as parks and gardens. The famous gardens of Europe, Britain, and Australia followed this example so that people living in cities could enjoy nature by strolling through trimmed, shaped, and manicured plant life, often sidestepping water sprinklers! Nothing of course could be farther from how nature truly exists. Many people nevertheless have come to think of nature in a parklike sense and feel that natural wetlands, grasslands, and meadows look a bit too messy. Culture therefore has a significant bearing on whether a person chooses a natural landscape over a manicured landscape.

Manicured landscapes involve high-maintenance endeavors that do little to help the environment, mainly because of water waste. The EPA’s WaterSense program has highlighted the following factors in water use and its waste in manicured landscape upkeep:

1. People water lawns too often and for too long, oversaturating soil and plants.
2. Many irrigation systems overspray onto paved areas.
3. Weather-based sensors and controllers can reduce water waste on lawns by 20 percent.
4. Soil moisture sensors can determine the amount of water in the ground available to plants.

 Turfgrass lawns provide the benefit of reducing soil erosion, but their maintenance, lack of diversity, and thirst for water far outweigh that single advantage. Since eco-landscaping requires strict care in water use and reuse, a new type of natural landscaping has evolved for the purpose of maximum water conservation: xeriscaping. In xeriscaping, land contour, plant selection, and irrigation methods all coordinate for the purpose of minimizing water demand. (Xeri derives from the Greek word xero for “dry”; the word scape refers to any view or scene.)

 Xeriscaping professionals select native plants with an emphasis on the most drought-tolerant species. In some parts of the United States, such as the dry southwestern region, xeriscaping serves as a crucial water conservation tool. In addition to drought-tolerant plantings, shade trees take part in a xeriscape by preventing excess water loss through evaporation. In some instances, xeriscaping also needs soil amendments so that the natural soil holds water better and does not drain too quickly. Organic matter

The plants selected for a landscape should be native or adapted to the climate. Drought-resistant plants such as
these help reduce water waste. (A) red columbine (B) coral honeysuckle (Trees 4NC)

 and humus added to fast-draining soils retain moisture, and sand helps slow-draining soils drain faster and prevents rotting. Landscaping therefore offers homeowners a variety of techniques for conserving water.

Plants and Trees

Landscaping with native plants and trees relies on two principles. First, native vegetation requires less input from a landscaper or homeowner because the vegetation has already acclimated to the soil composition, water constituents, and climate. Second, diverse plant life provides a more stable environment than landscaping with a limited variety of plants. A diverse mixture of native plants and trees fosters a diverse mix of insects, birds, and predators, or in other words, a balanced ecosystem. The ecosystem’s animal life reduces pests, spreads seeds, pollinates, trims bark, thins out foliage, and recycles nutrients. Variety in vegetation therefore helps maintain animal diversity, which in turn promotes more plant diversity.

Despite the advantages of native trees and plants, people often prefer a manicured look to their property because they have become accustomed to trimmed and lush lawns with neat shrubbery. For this reason, eco- landscapers sometimes blend native vegetation with ornamental plants. For instance, large properties of more than two acres can accommodate both a natural section growing native vegetation and a more manicured section that mixes native trees and plants with ornamental varieties. Part of the property retains its wild appearance, and the other part contains trimmed clearings and periodic removal of underbrush.

Edible landscaping involves planting of
fruiting and vegetable plants in place of
lawn. The plants enrich the soil, reduce
erosion, and provide a sustainable use
of the landscape. By growing food at
home, gardeners decrease the fuel used
to drive to a market, and, in a small way,
home gardening decreases the energy
needed for transporting food around the
world. (iVillageGardenWeb)

Homeowners may also choose to take a step toward sustainability by creating an edible landscape, meaning a property containing native fruiting and vegetable plants. The Associated Press writers John Seewer and Doug Whiteman reported in 2008, “The idea goes back centuries, to times when people sustained themselves with food they grew on their own and filled every corner of their land with edible plants. But with the mass production of food, the practice gave way to manicured lawns.” There are more than 20,000 edible plants in the world comprised of seeds, stalks, petals, pollen, and roots in addition to familiar fruits and vegetables. The table on page 144 lists some of the most common types that can be used in their native environment as part of an edible landscape.

Edible landscapes can also make use of edible flowers that give color and aesthetic appeal to a yard. The following list summarizes the most common edible flowers used in landscaping today: alliums (leeks, chives, etc.), angelica, anise, arugula, borage, chamomile, chicory, chrysanthemum, clover, dandelion, hibiscus, jasmine, lavender, marigold, pansy, peony, rose, and violet. When growing any edible flower, landscapers should not use chemical pesticides, and they should choose native plants that contribute to the local habitat.

Ecological Architecture

Ecological landscape design must by definition blend a new structure’s design with the land. Architect Frank Lloyd Wright in fact stressed that structures are not built on the land but in the land to emphasize the connection between human-made structures and environment. Ecological architecture therefore goes hand in hand with ecological landscaping.

Ecological architecture has the following objectives for the purpose of building a connection between a new structure and nature:

• Buildings conform to a site’s natural ecology.
• Buildings maximize the use of natural materials.
• Materials and waste should be managed in a way that returns them to the Earth.
• Materials and wastes do not harm the environment.
• The architecture is based on renewable energy.
• Each building possesses a sense of place that is directly tied to the local environment.

 Nature is an overriding theme of ecological architecture, so houses built this way have certain features in common that seem to bring nature right into each room. These features are large windows, skylights, large doors opening onto natural stone patios or a garden, flowing natural water near or in the house, and an emphasis on sunlight during the day and moonlight and the Milky Way at night.

 In order to attain a feeling of cooperation between humans and nature, ecological architects create with form and function in mind, often by using Frank Lloyd Wright’s designs as models. Ecological architects also make use of sustainable materials, off the grid energy use, and they have recently begun to explore concepts of biomimicry. Ecological architecture creates designs for buildings that will emphasize the use of renewable resources, natural building materials, and nonfossil fuel energy, all for the purpose of reducing the building’s ecological footprint. The ecological footprint is the amount of Earth’s land area needed to supply the resources to sustain a person or an activity and dispose of the wastes.

Ecological architecture calls upon new technologies to help meet some of its objectives. The main technologies now being used in ecological architecture are alternative lighting methods, heat distribution, water conservation and reuse, and natural waste decomposition methods. Many of the clues as to how to accomplish these activities may already be part of human history. Ancient civilizations completed magnificent feats of architecture without the use of machinery or steel (but they did make liberal use of backbreaking manual labor). Nature offers its own set of examples on how to maximize lighting, distribute heat and cooling, ventilate, use natural water flow, and decompose wastes.

Frank Lloyd Wright

Frank Lloyd Wright (1867–1959) was born in Wisconsin but spent most of his early years and professional life in Chicago, Illinois. Wright had dreamed of becoming an architect since his youth, and, after studying civil engineering, he moved to Chicago in 1887 to work for architect Joseph Lyman Silsbee, where he drafted his first building, Unity Chapel. A year later Wright joined Chicago’s Adler and Sullivan Architects. Under his mentor, Louis Sullivan, who advocated the philosophy of blending form with function in architecture, Wright expanded his viewpoint to develop the idea of “Form and Function Are One.” With Sullivan as a main influence on his budding career, Wright continued designing buildings that had a style never before seen in American design.

Frank Lloyd Wright’s buildings in the United States contain several core features that have made them unique and collectors’ items in the world of architecture. The most common hallmarks of Wright’s designs are: emphasis on the horizontal plane; no basements or attics; no paint; low-pitched rooflines with deep overhangs; uninterrupted walls of windows; liberal use of skylights; large, stone fireplaces in the building’s heart; and emphasis on the use of natural materials, such as woods and stone.

As Wright’s career and designs progressed, he increasingly integrated nature into his buildings. Sloping roofs matched the slope of the hillsides; large doors and windows lessened the distinction between the indoors and outdoors; and flowing brooks ran under, around, and sometimes through a building. Wright likely became the first person to use organic to express a new way of developing and designing an object or even a lifestyle. “Organic buildings are the strength and lightness of the spiders’ spinning,” he remarked, “buildings qualified by light, bred by native character to everyone and married to the ground.” Wright probably never used sustainable in connection with his architecture, yet Wright’s designs provide excellent guides for present-day sustainable or green houses. Wright followed his own path to sustainability decades before it became fashionable and even necessary. By favoring natural materials, natural cooling and ventilation, and using landscape to create part of a building’s structure and support, Wright certainly contributed to today’s environmental engineering.

By the end of Frank Lloyd Wright’s life, he had developed 1,141 home or building designs and completed 532 of them. His designs and the philosophy behind them influenced architecture in North America, Europe, and Asia. Ten Wright-designed buildings were nominated in 2008 by the Frank Lloyd Wright Building Conservancy to be included on the World Heritage List of the most significant cultural or natural treasures. The United Nations Educational, Scientific and Cultural

Fallingwater in Mill Run, Pennsylvania, was designed by Frank Lloyd Wright. Built between 1936 and 1939 in
the Bear Run watershed in western Pennsylvania, the house contained features rarely seen in architecture at
the time. Portions of the house appear to float free over a natural waterfall—the house is built directly on
top of a stream—and the entire house is in harmony with the woods around it.

Organization (UNESCO) oversees the competition; the nominations and selections will take place between 2009 and 2019. The 10 buildings that have been nominated because they best demonstrate Frank Lloyd Wright’s scope, quality, and unique design are the following:

1. Unity Temple, Oak Park, Illinois (completed 1904)
2. Frederick C. Robie House, Chicago, Illinois (1906)
3. Hollyhock House, Los Angeles, California (1921)
4. Taliesin, Spring Green, Wisconsin (1925)
5. Fallingwater, Mill Run, Pennsylvania (1939)
6. S. C. Johnson and Son, Inc., Administration Building and Research Tower, Racine, Wisconsin (1936, 1944)
7. Taliesin West, Scottsdale, Arizona (1937)
8. The Price Tower, Bartlesville, Oklahoma (1952)
9. Solomon R. Guggenheim Museum, New York City, New York (1956)
10. Marin County Civic Center, San Rafael, California (1957)

 The sites listed here and hundreds of other Wright buildings continue to serve as study models in environmental and civil engineering, landscaping, and ecological design.

Landscaping with Nature

When landscaping with nature, eco-landscapers prepare a parcel of land so that a new building will behave as architects and the homeowners intend, but also reduce its effects on air, land, and water. To preserve air quality, the landscaper designs planting arrangements that prevent dust. Dust-preventing tactics consist of groundcover plants, such as low-growing evergreen shrubs or herbs, ground vines, or pebbles. The landscaper also considers ways to minimize noise from nearby roads or neighbors and reduce disturbance from city lights at night. To preserve the quality of the land, the design should retain much of the natural vegetation, restore ground cover to prevent soil erosion, and avoid landscaping that could lead to mudslides, flooding, or trees downed by severe storms. Water quality preservation can be accomplished by preventing erosion that pollutes streams with silt, retaining the natural course of streams, leaving wetlands undisturbed, and creating a natural buffer zone around flowing waters, lakes, or shorelines.

Biodiversity gardens filled with a variety
of native vegetation at varying ages and
heights made good artificial habitats
for birds, small mammals, reptiles, and
amphibians. This type of garden requires
clean freshwater in a pond or fountain.
Native vegetation gardens need minimal
care, and they will not lead to rodent
infestation as some people fear because
they draw a variety of predators: hawks,
owls, and foxes. (Oregon State University)

The table on page 136 highlights the main ways that environmental engineers who specialize in landscaping create space that works well for a new home and for the local environment.

Habitats, Inc., is an eco- landscaping company in Eugene, Oregon, that has promoted all of the methods listed in the table on page 136 for building landscapes that blend with nature. The

company expresses the following viewpoint: “Landscapes are part of a living ecosystem, exposed to the elements and forces of nature, and are therefore in a constant state of dynamic equilibrium in the cycles of growth and decay. Creating and maintaining healthy ecosystems reduces the need for intensive routine maintenance.” Eco-landscaping therefore has advantages beyond the ones mentioned here. That is, eco-landscaping reduces a property owner’s costs and labor because it reduces the need for applying chemicals, pesticides, fertilizers, intense watering, and—because the landscape blends with the natural contours of the land—the need to build retaining walls, drainage ditches, or other structures that try to hold back the forces of nature. The sidebar on page 138 “Frank Lloyd Wright” relates how one architect introduced the concept of designing with nature.

City residents can also participate in ecological landscaping with a bit of inventiveness. Some city townhouses and apartments include small backyards. Owners can plant these backyards with native shrubs and plants rather than cover the ground with concrete. One native tree fit into even a small yard helps to draw native birds, insects, and other life that bring nature into the city. Plant life additionally removes carbon dioxide (CO2) from the atmosphere, a process that aids the air quality of traffic-clogged cities. Some city dwellers with a serious commitment to the environment build permaculture farms inside their properties. A permaculture farm uses sustainable practices such as composting, rainwater collection, and cultivation of vegetables and fruits. Some city permaculture farms may even raise animals such as chickens if local ordinances allow it.
Cities would benefit from ecological landscaping because the trees and vegetation that are part of an ecological landscape help clean the air and regulate temperatures. But today’s metropolitan areas have lost most of their connection to nature so ecological landscaping may not be a practical undertaking. To return even a small parcel of land to the environment requires a landscaper to remove pavement, return streams to their natural shape and condition, and plant native vegetation. The brownfields program administered by the U.S. Environmental Protection Agency (EPA) and similar programs in other countries consist of voluntary agreements in which landowners return polluted property to safe use. Sometimes the owner works with the local community to return the cleaned-up brownfield to its natural condition. Once urban brownfields have been restored with natural vegetation and landscaping, they are called green spaces.

Traditional Landscape Design

Landscape design begins with a survey of a specific parcel of land, followed by mapping of all the physical features the surveyors have identified. These features include hills, gullies, trees, streams, ponds, and any preexisting structures, roads, or driveways. A landscaper then contours the land to accommodate any new building about to be constructed on the site.

A trimmed and fertilized lawn became
the hallmark of landscaping in the early
20th century. Green lawns appeal to
many people, but, unless the landscape
is carefully managed, a lawn breaks up
natural vegetation, destroys habitat,
wastes water, and often includes chemical
fertilizers that run off the lawn and
contaminate surface waters. Many lawncare
companies now use sustainable lawn
management by applying only organic
fertilizers and selecting grasses adapted
to the environment, so they need less
watering. (Taylor Made Lawncare Services)

Traditional landscaping for decades began by cutting down trees and bulldozing the site to make access easier for construction workers. Often landscapers used dynamite to break up large rock formations. They then hauled away surface boulders, filled ponds, and drained wetlands. Sometimes they lopped off the tops of trees to improve a view. These changes to the land were once thought to be enhancements to a property, but environmental engineers now understand that the greater the change made to a landscape, the greater the disruption to natural ecosystems. Ecological landscapers have now changed the way in which landscaping is done for three purposes: (1) preserving natural habitat, plants, and trees; (2) leaving as much natural contour in the land as possible; and (3) using the natural landscape to enhance the energy use of the new building.

Today’s ecological landscaping still has a need for heavy earthmoving equipment, but ecological landscapers make greater efforts to preserve natural hills and depressions, streams and wetlands, and trees. All landscaping has evolved so that today it incorporates the following aspects:

1. water, topsoil, and energy conservation
2. reduction of storm water runoff
3. horticulture of native plants
4. pest management that reduces the use of chemicals by using natural pest antagonists
5. nutrient replenishment of soils by methods other than chemical fertilizers
6. new plantings and gardens to restore habitat
7. waste reduction and recycling of construction wastes

 Landscapers who include these features in their work are called ecolandscapers. Unlike landscaping of just a decade ago, eco-landscaping makes every effort to include the natural geography and topography of the site to be altered. Eco-landscapers follow nature’s lead in order to preserve ecosystems and conserve energy.

Even landscapes that contain traditional features such as lawns, gardens with nonnative plants, and nonnative fruiting and flowering trees can be transformed into a more compatible fit with the surrounding ecosystem. Some homeowners have done this by replanting lawns with natural vegetation and replacing nonnative growth, such as a rose garden with a garden of native plants and shrubs. A landscape that in the past received major changes to its contour cannot be rebuilt to its original shape, but owners can take other steps to return the land to a natural state.

Ecological Landscape Design

Land degradation represents one of the biggest threats to the environment. The destruction of natural habitat by uprooting forests and grasslands disrupt carbon recycling and storage. New housing developments break up wildlife habitats, cloud streams with excess silt, and cause soil erosion. Even the best-planned developments disrupt nature’s landscape. Single houses built on undisturbed land produce similar harms to ecosystems, including the ecosystems that are almost invisible to people, such as soil ecosystems, the species living in foliage, and the microscopic life in nearby streams. Few people could miss the irony that comes from building an energy-efficient solar-powered home on a hillside that has been denuded of trees, bushes, and earth. In order to mesh the innovations of energy-efficient homes with nature, environmental engineers have begun to pay special attention to a new structure’s surroundings. For this reason, environmental engineering incorporates a component that considers land topography, climate, and natural vegetation. Ecological landscape design combines the task of coordinating a new building with its natural surroundings and remodeling the landscape to fit the new building in a natural way.

Today’s ecological landscape design has three main objectives: (1) minimize the disturbance done to the land during and after construction; (2) minimize all health risks to people and the environment due to the new construction; and (3) reduce construction wastes. At the end of a construction project that has worked within these guidelines, the new structure should function in harmony with the environment. As the theme of this book stresses, environmental engineering seeks to work in cooperation with nature rather than to find ways to subdue nature.

Energy from Nanotechnology

Energy-efficient electronics depend on some form of energy storage so that excess energy can be held for future use and not wasted. In fact power storage makes up one of the three main components of energy management for homes as well as vehicles: power generation, power transmission, and power storage. Lynn E. Foster, author of the book Nanotechnology: Science, Innovation, and Opportunity, opined, “If you can solve the problem of local storage, you’ve basically solved the whole problem. That’s because, by definition, the storage you need is local. You’ve got terawatts [equals one trillion watts or one billion kilowatts] of power moving into the grid. The biggest problem with renewable energy in general, and solar and wind in particular, is that they’re episodic and not dispatchable.” This means that the energy supplied on community power grids comes in pulses rather than in a steady stream, and utilities cannot dispense the energy in doses as needed. Foster continued, “You’ve got to have storage. Storing energy in batteries, capacitors, fuel cells, and some chemical systems like hydrogen depends on nanoscale interactions.” Nanoscale is a general term for the size of things that are no bigger than an atom or a molecule—a nanometer is one billionth of a meter. Nanotechnology is the science of working with nanoscale-sized devices.

Nanotechnology’s value to science lies in the observation that matter behaves differently at the nanoscale than it does on a larger scale. The DOE has explained this technology and its value: “All the elementary steps of energy conversion (charge transfer, molecular rearrangement, chemical reactions, etc.) take place on the nanoscale. Thus, the development of new nanoscale materials, as well as the methods to characterize, manipulate and assemble them, creates an entirely new paradigm for developing new and revolutionary energy technologies.” Nanotechnology is still in its

Engineers have been using nanotechnology to develop thin layers designed for generating an electrical current and producing light. The next step using nanoscale materials may be to convert solar power directly to light with a solid-state structure such as this one. Engineers also plan to embed tiny solar cells in window glass to produce electricity from sunlight. (Source: Paul Alivisatos, Lawrence Berkeley National Laboratory)

infancy, as scientists discover new behaviors of common materials when at the nanoscale level and find ways of applying this knowledge for practical uses. The following table provides a list of the main opportunities in nanotechnology for producing new energy-generation systems for electronics and other items.

Nanotechnology will likely help in the development of the following two energy conservation objectives: inventing future energy generation devices that perform in ways that current devices cannot, and finding new ways to catalyze reactions to minimize energy input and waste output. At present, ideas for new uses of nanotechnology have developed faster than actual methods have developed.

The Btu and the Kilowatt

The acronym Btu (or BTU) stands for British thermal unit. Energy utilities use two terms, Btu and kilowatt (kW) to describe energy and power; a Btu is a unit of energy and a kW is a unit of power. Energy equals the potential ability to do work or produce heat. By contrast, power is the rate at which work is done. The difference between energy units and power units can be expressed as follows:

1. A kilowatt is the rate of energy use at this instant.
2. Kilowatt-hours refers to the total amount of energy used over time.

 Therefore, utility companies, appliance companies, and fuel producers often relate the Btu to the kilowatt by transforming the expression for energy to an expression for power by the following conversion:

1 Btu = 2.9 × 10-4 kilowatt-hours (kWh)

(The Btu itself can be converted to a unit of power, the Btu-hour [Btu/h], though this term is less commonly used than kilowatt-hour.)

A person can visualize the Btu as the amount of heat required to raise one pound (0.45 kg) of water one degree Fahrenheit from 60°F to 61°F (15.6° to 16.1°C). Home appliances range from 5,000 to 50,000 Btu, and in the United States the population uses 100 quadrillion Btu (called Quad) in a single year.

Most home electrical devices use very small kilowatt amounts that can also be measured in watts, or one-thousandth of a kilowatt. Electrical devices typically range from 15 to 500 watts (0.015–0.5 kW). An appliance that provides a power value in amps, for amperes, rather than watts can be converted as follows:

number of amps × 120 volts = number of watts

By understanding the Btu and kilowatt-hours, homeowners can accomplish two objectives: gain a better idea of how appliances consume energy, and understand their rate of energy use in order to monitor energy savings.

Sensors and Feedback

Sensors that work with feedback systems easily and automatically conserve energy. Energy sensors monitor the use of electrical and heat energy within a room or an entire building. Sensors can be used in two different ways to conserve energy. First, they monitor a building’s peak and nonpeak times of energy use and so identify the periods in which a structure puts more or less stress on a community’s power grid. Second, on-off sensors such as motion sensors turn indoor or outdoor lights on when they detect motion and off when the area is no longer being used to reduce energy waste.

A wood stove generates heat without
using electricity. Stoves and fireplaces
conserve a house’s solar power and avoid
the need to draw from the municipal
power grid. Wood is a type of biomass
that produces an equivalent amount
of Btu as crop wastes, which are also
combusted for energy production. (Jotul)

Sensors in combination with feedback systems provide even better control of energy use because a feedback system tells a building’s residents how efficient they are in using energy. A sensor- feedback system contains two components: the detection unit called a transmitter that may be attached to an electrical or gas utility meter, a water meter, or a thermometer, and the display unit located inside the house, which receives wireless signals from the transmitter. Sarah Rich wrote for the online environmental magazine WorldChanging, “It’s one of those telling facts of human nature that when we are being monitored, our behavior changes.” Just like a speedometer in a car, people self-monitor when they receive helpful information. “The same holds true in households,” Rich explained, “where inhabitants can be made immediately aware of their energy consumption. If you can see your pennies piling up on account of a light you left on in the bathroom, you can bet you’ll remember to turn it off.” These so-called smart sensors offer one of the simplest ways to manage energy use.

New systems make energy savings even easier for people to save energy. Hotels or homes can be equipped with key cards that contain information on the indoor heating, cooling, and lighting systems. As a person enters a room, inserting the card into a small slot box near the door, lights and other systems turn on to make the environment comfortable, with heat, air-conditioning, or ventilation. The person simply removes the card from the slot when they leave, and the systems readjust to energy-saving mode. Sensors and automatic on-off switches are inexpensive, and the electricity savings make up for the price in a short period of time.