BIOLOGY Volume 1 - A Guide to General Biology - 2004

10. ORGANISMS AND THE ENVIRONMENT

10.9. Environmental Protection

10.9.6. Waste Recycling and Reuse

Modern society generates vast amounts of waste. Much of this waste contains valuable Materials that can be recovered and reused, thereby reducing the demand for extracting additional resources. An obvious example is The Use of scrap metal instead of iron ore. The energy costs and pollution associated with recycling are often much lower than those involved in the extraction and Processing of raw materials. For instance, in Europe, using steel scrap saves up to 50% of energy, and aluminum scrap saves up to 95%! Many manufacturers are now reducing their use of packaging materials, not only to lower production costs but also to minimize waste volume and, consequently, environmental pollution.

A very important positive aspect of recycling is precisely the reduction of environmental pollution. In Britain, the bulk of household and municipal waste is disposed of in landfills, which are rapidly filling up, especially in the densely populated southeast of the country. In 1996, in response to Agenda 21, the UK government introduced a new landfill tax designed to encourage both producers and consumers to reduce waste generation and reuse materials as secondary raw materials and fuel.

With municipal solid waste recycling rates ranging from 1 to 8%, the government set a target to raise this figure to 25% by 2000.

However, recycling is associated with several difficulties:

1) thorough sorting and cleaning of waste are required. For example, a single shard of Pyrex heat-resistant glassware in a batch of broken Glass can render the entire secondary product unusable;

2) prices for recycled materials fluctuate wildly. For instance, in 1996, waste paper fetched three times less than in 1995;

3) The process of returning recyclables must be made more accessible to the public. In most cases, a "self-service" system is in place, where consumers must take their recyclables to a designated collection point, which limits The Scope of participation. Recently, to expand this practice, experiments with mobile collection rounds similar to garbage trucks have been implemented.

A significant portion of municipal waste can be biodegraded. During this process, methane gas is released, which also possesses pronounced greenhouse properties. With a reliable capture system, this gas can be collected and used as fuel for electricity generation. At the Mucking landfill in Essex, which serves several London boroughs, a 3.5 MW power plant is in operation, supplying enough energy to run a factory or power 30,000 people. At the same time, such methane utilization reduces the risk of fires caused by uncontrolled gas emissions, and the carbon dioxide produced during combustion has a much lower greenhouse effect.

In the future, waste incineration for energy recovery will likely become the primary method of waste disposal. It will reduce the demand for both fossil fuels and landfill space.

Microorganisms commonly found in soil and fresh Water are used for sewage Treatment. If these liquid wastes were discharged untreated, the inevitable decomposition of the large amounts of organic matter they contain would lead to rapid and severe deoxygenation of the receiving water bodies. Wastewater treatment involves natural microbial feeding processes and yields nitrogen-rich sludge and methane as by-products. If the sludge is not contaminated with heavy metals (such as lead from leaded gasoline), it can be used as fertilizer after drying. Sludge is widely applied in land reclamation to improve soil Structure and enrich it with nutrients (Section 10.5.2). Methane (biogas) can be burned to generate electricity and heat for the treatment plants themselves, and sometimes for other enterprises or small settlements.

New Energy Sources

In Britain, the primary energy source is fossil fuels, which are a non-renewable resource. Nuclear power plants provide roughly 10% of electricity; however, they not only rely on non-renewable uranium reserves but also pose risks of radioactive contamination, alongside the challenges of radioactive waste disposal and the decommissioning of obsolete nuclear reactors. Concerns over the inevitable depletion of these fuel reserves and the environmental pollution associated with their use drive the search for alternative energy sources.

On a global scale, aside from fossil fuels, the main accessible and replenishable energy reservoir is biomass (wood, charcoal, crop processing residues, manure, and other organic waste). This source accounts for 14% of global energy demand, and in developing countries, it takes the lead at 35%. Biotechnology helps convert naturally occurring organic matter into ready-to-use alternative fuels. For instance, Brazil carries out large-scale processing of sugarcane into ethanol, which is blended with gasoline to produce gasohol, thereby reducing gasoline consumption. In North America, cereal grains such as corn, wheat, and barley are fermented for the same purpose, while in Europe, locally cultivated sugar beets could be used to produce ethanol fuel. Ethanol is a more environmentally friendly fuel than petroleum products because it contains no sulfur and requires no lead additives.

Many other renewable energy sources are well known: solar radiation, wind, rivers, tides, waves, and geothermal heat. This potential is virtually limitless, provided cost-effective ways to harness it are found.

Hydropower is the most widely utilized renewable source. Worldwide, hydroelectric power plants have a total capacity of 500,000 MW, supplying about 23% of all electricity. The majority of untapped hydroelectric potential is concentrated in developing countries. Large dams, such as Itaipu in Brazil, provide cheap electricity, but their distribution systems are often inadequate, limiting the economic viability of such projects. Moreover, they typically entail severe environmental and social problems, namely:

1) the displacement of people from flooded areas, turning them into "environmental refugees";

2) the inundation of valuable agricultural land and forests;

3) an increased risk of diseases whose pathogens or vectors thrive in stagnant waters (reservoirs), such as Schistosomiasis;

4) disruption of natural river flow regimes;

5) intensification of soil erosion.

Siltation and acidification often limit the economically viable lifespan of large hydroelectric complexes, sometimes reducing it to as little as 30 years.

Nevertheless, the use of most renewable energy sources is less harmful to the environment than fossil-fuel installations, including nuclear power plants. A serious problem, however, remains the inability to transition large-scale centralized energy supply to an alternative basis. Renewable resources themselves, such as ocean waves, wind, and solar radiation, are distributed very unevenly across the planet and, even under optimal conditions, possess a low power density per unit area of the respective power plants. Moreover, their output often fluctuates wildly due to variable cloud cover, wind speeds, etc., thus requiring traditional backup power supplies.

However, renewable resources can be integrated into existing electrification schemes to increase their capacity. For instance, wind turbines, which are still not very common in Britain, are widely used in A number of other countries. In California, solar space and water heaters have become a standard feature of modern architectural designs. At the 2000 Olympic Games in Sydney, Australia, it was proposed to generate 10 MW of energy directly from the sun. A tidal power station operates successfully in the Rance River estuary in northern France. At the same time, although several schemes for generating electricity from surf waves have been proposed, no commercially viable option for their use has yet been found.

Renewable energy sources are ideally suited for supplying small, isolated consumers, such as those on islands, in high-altitude regions, or in deserts. They are particularly promising in developing countries, where abundant solar energy can be effectively utilized in local industry, schools, clinics, pumping stations, and the like.