Solid wastes, sources, disposal problems and management technologies, Recycling, resource recovery

Sources of solid waste

Residential: (Single and multifamily dwellings) Food wastes, paper, cardboard, plastics, textiles, leather, yard wastes, wood, glass, metals, ashes, special wastes (e.g., bulky items, consumer electronics, batteries, oil, tires), and household hazardous wastes)

Industrial: (Light and heavy manufacturing, fabrication, construction sites, power and chemical plants). Housekeeping wastes, packaging, food wastes, construction and demolition materials, hazardous wastes, ashes, special wastes.

Commercial: (Stores, hotels, restaurants, markets, office buildings, etc.) Paper, cardboard, plastics, wood, food wastes, glass, metals, special wastes, hazardous wastes.

Institutional: (Schools, hospitals, prisons, government centers) Same as commercial

Construction and demolition: (New construction sites, road repair, renovation sites, demolition of buildings) Wood, steel, concrete, dirt, etc.

Municipal services: (Street cleaning, landscaping, parks, beaches, other recreational areas, water and wastewater treatment plants). Street sweepings; landscape and tree trimmings; general wastes from parks, beaches, and other recreational areas; sludge

Process (manufacturing, etc.): Heavy and light manufacturing, refineries, chemical plants, power plants, mineral extraction and processing (paper industries, Leather processing industries, sugar distillery industries, rubber sago processing industries, coffee, coconut spice, beverage and landscaping). Industrial process wastes, scrap materials, off-specification products, slay, tailings.

Agriculture (Crops, orchards, vineyards, dairies, feedlots, farms. Spoiled food wastes, agricultural wastes, crop residues, hazardous wastes (e.g., pesticides)

Common waste disposal problems

Various waste disposal problems

1.   Production of too much waste

One of the major waste disposal problems is attributed to the generation of too much waste. According to the World Bank report, the average global municipal solid waste (MSW) generation per person on daily basis is about 1.2 kg and the figure is expected to rise up to 1.5 kg by 2025. It therefore means that every state and local authority suffer the problem of effective waste disposal due to the generation of too much waste. The problem is that the present era is driven by a throw-away consumerism with companies and producers striving to maximize profits by producing one-time use products without prioritizing on reuse, recycling or the use of environmentally friendly materials.

2.       Most of the waste is toxic (Cr (VII) in tannery effluent)

The majority of the state and local authority legislations are generally lax on regulating the ever-expanding manufacturing industries. On a daily basis, these industries produce toxic products that end up getting thrown away after use. Most of the products contain hazardous and health-threatening chemicals.

A report by the U.S. EPA indicates that more than 60,000 untested chemicals are present in the consumer products in our homes. There are even products known to contain toxic chemicals, such as Biphenyl-A (BPA) – often present in plastic toys, but they are still poorly regulated. Packaging is also one of the biggest and rapidly enlarging categories of solid waste which accounts for 30% of MSW and approximately 40% of the waste is plastic which is never biodegradable. It’s this level of toxicity together with the lax regulatory laws that exacerbates the problem of dealing with waste disposal.

3.     Landfills are a problem as well

Most landfills lack proper on-site waste management thereby contributing to additional threats to the environment. In the long-term, landfills leak and pollute ground water and other neighboring environmental habitats making waste management very difficult. They also give off potentially unsafe gases.

Also, the laws and regulation guiding the operations of landfills are often lax at monitoring and regulating the different types of wastes namely medical waste, municipal waste, special waste or hazardous waste. With this kind of laxity of the laws in landfill waste management, the landfills toxicity and hazardous nature significantly increases to a point where the landfill waste problems often lasts for up to 30 years.

4.         Regulations are based on vested interests

Since waste disposal and management has become a profit making venture, those who advocate for safe, quality and proper management of waste disposal are outmatched by industries in the business. Large enterprises in the waste disposal business dictate all aspects of the market from operating landfills, sewer systems and incinerators to recycling facilities. The corporations simply aim at making profits regardless of the waste reduction requirements or the resultant destructive environment impacts.

As such, they collaborate with vested interest regulators thereby creating a big problem in the effective regulation of waste disposal, which has worsened the devotions to waste reduction and recycling programs. To make matters worse, even some state officials work together with such industry officials to expand landfills, increase waste tonnage, and develop new waste disposal or recycling or treatment facilities to augment profits.

5.         Reliance of dying technologies to reduce and recycle waste

Waste disposal and management facilities as well as state resources have continued to rely on myopic and quickie solutions instead of developing effective recycling and waste reduction programs. Consequently, it has created continued reliance on the use of outdated technologies to deal with waste disposal. The problem is that most states are reluctant and less creative towards advancing novel technologies for reducing the toxicity and volume of waste or enhancing recycling, especially solid waste.

6.         Some of the technologies marked as “green” are not true in actual sense

Recycling technologies such as plasma arc, gasification, and pyrolysis are often marked as “green” but the truth of the matter is that they are not 100% green. These recycling technologies burn up waste with little or no oxygen and for this reason; it doesn’t differentiate them from the traditional incinerators which produce energy from burning waste.

As much as burning waste to produce energy is considered green because it does not involve the use fossil fuel, it still releases toxic materials into the environment. Also like the traditional waste incineration systems, these technologies emit toxic ash into the atmosphere that can potentially harm people’s health and the environment. Therefore, the technologies simply divert concentration from the development of cleaner recycling and waste reduction technologies.

Solid management technologies

Compost

Compost is organic matter that has been decomposed in a process called composting. This process recycles various organic materials otherwise regarded as waste products and produces a soil conditioner (the compost). Compost is rich in nutrients used in gardens, landscaping, horticulture, urban agriculture and organic farming. The compost itself is beneficial for the land in many ways, including as a soil conditioner, a fertilizer, addition of vital humus or humic acids, and as a natural pesticide for soil. In ecosystems, compost is useful for erosion control, land and stream reclamation, wetland construction, and as landfill cover.

At the simplest level, the process of composting requires making a heap of wet organic matter (also called green waste), such as leaves, grass, and food scraps, and waiting for the materials to break down into humus after a period of months. However, composting also can take place as a multi-step, closely monitored process with measured inputs of water, air, and carbon and nitrogen-rich materials. The decomposition process is aided by shredding the plant matter, adding water and ensuring proper aeration by regularly turning the mixture when open piles or "windrows" are used. Earthworms and fungi further break up the material. Bacteria requiring oxygen to function (aerobic bacteria) and fungi manage the chemical process by converting the inputs into heat, carbon dioxide, and ammonium.

Incineration is a waste treatment process that involves the combustion of organic substances contained in waste materials at a temperature of more than 850⁰C for a minimum duration of 2 seconds. Incineration and other high-temperature waste treatment systems are described as "thermal treatment". Incineration of waste materials converts the waste into ash, flue gas and heat. The ash is mostly formed by the inorganic constituents of the waste and may take the form of solid lumps or particulates carried by the flue gas. The flue gases must be cleaned of gaseous and particulate pollutants before they are dispersed into the atmosphere. In some cases, the heat generated by incineration can be used to generate electric power.

Incineration with energy recovery is one of several waste-to-energy (WtE) technologies such as gasification, pyrolysis and anaerobic digestion. While incineration and gasification technologies are similar in principle, the energy produced from incineration is high-temperature heat whereas combustible gas is often the main energy product from gasification. Incineration and gasification may also be implemented without energy and materials recovery.

In several countries, there are still concerns from experts and local communities about the environmental effect of incinerators. In some countries, incinerators built just a few decades ago often did not include a materials separation to remove hazardous, bulky or recyclable materials before combustion. These facilities tended to risk the health of the plant workers and the local environment due to inadequate levels of gas cleaning and combustion process control. Most of these facilities did not generate electricity.

Incinerators reduce the solid mass of the original waste by 80–85% and the volume (already compressed somewhat in garbage trucks) by 95–96%, depending on composition and degree of recovery of materials such as metals from the ash for recycling. This means that while incineration does not completely replace landfilling, it significantly reduces the necessary volume for disposal. Garbage trucks often reduce the volume of waste in a built-in compressor before delivery to the incinerator. Alternatively, at landfills, the volume of the uncompressed garbage can be reduced by approximately 70% by using a stationary steel compressor, albeit with a significant energy cost. In many countries, simpler waste compaction is a common practice for compaction at landfills.

Incineration has particularly strong benefits for the treatment of certain waste types in niche areas such as clinical wastes and certain hazardous wastes where pathogens and toxins can be destroyed by high temperatures. Examples include chemical multi-product plants with diverse toxic or very toxic wastewater streams, which cannot be routed to a conventional wastewater treatment plant.

Waste combustion is particularly popular in countries such as Japan where land is a scarce resource. Denmark and Sweden have been leaders by using the energy generated from incineration for more than a century, in localized combined heat and power facilities supporting district heating schemes. In 2005, waste incineration produced 4.8% of the electricity consumption and 13.7% of the total domestic heat consumption in Denmark. A number of other European countries rely heavily on incineration for handling municipal waste, in particular Luxembourg, the Netherlands, Germany, and France.

A landfill site (a tip, dump, rubbish dump, garbage dumpor dumping ground and historically as a midden) is a site for the disposal of waste materials by burial. It is the oldest form of waste treatment (although the burial part is modern; historically, refuse was just left in piles or thrown into pits). Historically, landfills have been the most common method of organized waste disposal and remain so in many places around the world.

Some landfills are also used for waste management purposes, such as the temporary storage, consolidation and transfer, or processing of waste material (sorting, treatment, or recycling). Unless they are stabilized, these areas may experience severe shaking or soil liquefaction of the ground during a large earthquake.

Recycling is the process of converting waste materials into new materials and objects. It is an alternative to "conventional" waste disposal that can save material and help lower greenhouse gas emissions. Recycling can prevent the waste of potentially useful materials and reduce the consumption of fresh raw materials, thereby reducing: energy usage, air pollution (from incineration), and water pollution (from landfilling).

Recycling is a key component of modern waste reduction and is the third component of the "Reduce, Reuse, and Recycle" waste hierarchy. Thus, recycling aims at environmental sustainability by substituting raw material inputs into and redirecting waste outputs out of the economic system.

There are some ISO standards related to recycling such as ISO 15270:2008 for plastics waste and ISO 14001:2015 for environmental management control of recycling practice.

Recyclable materials include many kinds of glass, paper, and cardboard, metal, plastic, tires, textiles, and electronics. The composting or other reuse of biodegradable waste—such as food or garden waste—is also considered recycling. Materials to be recycled are either brought to a collection center or picked up from the curbside, then sorted, cleaned, and reprocessed into new materials destined for manufacturing.

In the strictest sense, recycling of a material would produce a fresh supply of the same material—for example, used office paper would be converted into new office paper or used polystyrene foam into new polystyrene. However, this is often difficult or too expensive (compared with producing the same product from raw materials or other sources), so "recycling" of many products or materials involves their reuse in producing different materials (for example, paperboard) instead. Another form of recycling is the salvage of certain materials from complex products, either due to their intrinsic value (such as lead from car batteries, or gold from circuit boards), or due to their hazardous nature (e.g., removal and reuse of   mercury from thermometers and thermostats).

Resource recovery

Resource recovery is when energy, a material, or a product is taken from waste and used. Resource recovery can be useful in waste disposal. For example, specific chemicals may often be recovered by stripping, distillation, leaching, or extraction.

The materials from which the items are made can be reprocessed into new products. Material for recycling may be collected separately from general waste using dedicated bins and collection vehicles, or sorted directly from mixed waste streams.

The most common consumer products recycled include aluminium such as beverage cans, copper such as wire, steel food and aerosol cans, old steel furnishings or equipment, polyethylene and PET bottles, glass bottles and jars, paperboard cartons, newspapers, magazines and light paper, and corrugated fiberboard boxes.

PVC, LDPE, PP, and PS  are also recyclable. These items are usually composed of a single type of material, making them relatively easy to recycle into new products. The recycling of complex products (such as computers and electronic equipment) is more difficult, due to the additional dismantling and separation required.