"Eliminating water shortages depends on a global attempt to raise water productivity similar to the effort launched a half-century ago to raise land productivity, an initiative that has nearly tripled the world grain yield per hectare." –Lester R. Brown, World Facing Huge New Challenge on Food Front in Plan B 3.0: Mobilizing to Save Civilization
Chapter 7. Raising Water Productivity: Raising Nonfarm Water Productivity
Nonfarm water use is dominated by the use of water simply to wash away waste from factories and households or to dissipate heat from thermal power plants. The use of water to disperse wastes is an outmoded practice that is getting the world into trouble. Toxic industrial wastes discharged into rivers and lakes or into wells also permeate aquifers, making water—both surface and underground—unsafe for drinking. And they are destroying marine ecosystems, including local fisheries. The time has come to manage waste without discharging it into the local environment, allowing water to be recycled indefinitely and dramatically reducing both urban and industrial demand.
The current engineering concept for dealing with human waste is to use vast quantities of water to wash it away in small amounts, preferably into a sewer system where it will be treated before being discharged into the local river. There are four problems inherent in this "flush and forget" system: it is water-intensive; it disrupts the nutrient cycle; most of humanity cannot afford it; and it is a major source of disease in developing countries.
As water scarcity spreads, the viability of water-based sewage systems will diminish. Water-borne sewage systems take nutrients from the land and dump them into rivers, lakes, or the sea. Not only are the nutrients lost from agriculture, but the nutrient overload has led to the death of many rivers, including nearly all of those in India and China. Water-based sewage also contributes to dead zones in coastal oceans. Sewer systems that dump untreated sewage into rivers and streams, as so many do, are a major source of disease and death.34
Sunita Narain of the Centre for Science and Environment in India argues convincingly that a water-based disposal system with sewage treatment facilities is neither environmentally nor economically viable for India. She notes that an Indian family of five, producing 250 liters of excrement in a year and using a water toilet, requires 150,000 liters of water to wash away the wastes.35
As currently designed, India's sewer system is actually a pathogen-dispersal system. It takes a small quantity of contaminated material and uses it to make vast quantities of water unfit for human use, often simply discharging it into nearby rivers or streams. Narain says both "our rivers and our children are dying." India's government, like that of many other developing countries, is hopelessly chasing the goal of universal water-based sewage systems and sewage treatment facilities—unable to close the huge gap between services needed and provided, but unwilling to admit that it is not an economically viable option. Narain concludes that the "flush and forget" approach is not working.36
This dispersal of pathogens is a huge public health challenge. Worldwide, poor sanitation and personal hygiene claim 2.7 million lives per year, second only to the 5.9 million claimed by hunger and malnutrition.37
Fortunately there is an alternative to the use of water to wash away human waste: the composting toilet. This is a simple, waterless toilet linked to a small compost facility. Table waste can also be incorporated in the composter. The dry composting converts human fecal material into a soil-like humus, which is essentially odorless and is scarcely 10 percent of the original volume. These compost facilities need to be emptied every year or so, depending on their design and size. Vendors periodically collect the humus and market it for use as a soil supplement, returning the nutrients and organic matter to the soil and reducing the need for fertilizer.38
This technology reduces residential water use, thus cutting the water bill and lowering the energy needed to pump and purify water. As a bonus, it also reduces garbage flow if table waste is incorporated, eliminates the sewage water disposal problem, and restores the nutrient cycle. The U.S. Environmental Protection Agency now lists several brands of dry toilets for use. Pioneered in Sweden, these toilets are used in widely varying conditions, including Swedish apartment buildings, U.S. private residences, and Chinese villages.39
At the household level, water can be saved by using appliances that are more water-efficient, including showerheads, flush toilets, dishwashers, and clothes washers. Some countries are adopting water efficiency standards and labeling for appliances, much as has been done for energy efficiency. As water costs rise, as they inevitably will, investments in composting toilets and more water-efficient household appliances will become increasingly attractive to individual homeowners.
For cities, the most effective single step to raise water productivity is to adopt a comprehensive water treatment/recycling system, reusing the same water continuously. With this system, a small percentage of water is lost to evaporation each time it cycles through. Given the technologies that are available today, it is quite possible to comprehensively recycle urban water supplies, largely removing cities as a claimant on water resources.
At the industrial level, one of the largest users of water is the energy sector, which uses water to cool thermal power plants. As fossil fuels are phased out and the world turns to wind, solar, and geothermal energy, the need for cooling water in thermal power plants will diminish. In the United States, for example, thermal cooling of power plants accounts for 39 percent of all water withdrawals. With each coal-fired power plant that is closed as a new wind farm comes online, water use for thermal cooling drops, freeing up water for food production.40
Many of the industrial processes now used belong to a time when water was an abundant resource. Within the steel industry, for example, water use efficiency may vary among countries by a factor of three. Much of the water used in industry just washes away waste. If this is stopped, and more and more companies move into zero-emissions industrial parks, water use in industry could drop dramatically.41
The new reality is that the existing water-based waste disposal economy is not viable. There are too many factories, feedlots, and households to simply try and wash waste away. It is ecologically mindless and outdated—an approach that belongs to an age when there were many fewer people and far less economic activity.
34. Sunita Narain, "The Flush Toilet is Ecologically Mindless," Down to Earth, 28 February 2002, pp. 28-32.
38. U.S. Environmental Protection Agency, "Water Efficiency Technology Factsheet-Composting Toilets," information sheet (Washington, DC: September 1999).
40. Noel Gollehon, William Quinby, and Marcel Aillery, "Water Use and Pricing in Agriculture," in USDA, Agricultural Resources and Environmental Indicators 2003 (Washington, DC: February 2003), Chapter 2.1, p. 2.
41. Postel, op. cit. note 15, pp. 136-45.
Copyright © 2003 Earth Policy Institute