Enzyme Production

 Enzymes are among the most important products obtained for human needs through microbial sources. A large number of industrial processes in the areas of industrial, environmental and food biotechnology utilize enzymes at some stage or the other. Current developments in biotechnology are yielding new applications for enzymes. Solid state fermentation (SSF) holds tremendous potential for the production of enzymes. It can be of special interest in those processes where the crude fermented products may be used directly as enzyme sources. This review focuses on the production of various industrial enzymes by SSF processes. Following a brief discussion of the micro-organisms and the substrates used in SSF systems, and aspects of the design of fermenter and the factors affecting production of enzymes, an illustrative survey is presented on various individual groups of enzymes such as cellulolytic, pectinolytic, ligninolytic, amylolytic and lipolytic enzymes, etc.

Solid state fermentation (SSF) holds tremendous potential for the production of enzymes. It can be of special interest in those processes where the crude fermented product may be used directly as the enzyme source1. In addition to the conventional applications in food and fermentation industries, microbial enzymes have attained significant role in biotransformations involving organic solvent media, mainly for bioactive compounds. This system offers numerous advantages over submerged fermentation (SmF) system, including high volumetric productivity, relatively
higher concentration of the products, less effluent generation, requirement for simple fermentation equipments, etc.

Microorganisms used for the production of enzymes in solid state fermentation systems

A large number of microorganisms, including bacteria, yeast and fungi produce different groups of enzymes. Selection of a particular strain, however, remains a tedious task, especially when commercially competent enzyme yields are to be achieved. For example, it has been reported that while a strain of Aspergillus niger produced 19 types of enzymes, a -amylase was being produced by as many as 28 microbial cultures3. Thus, the selection of a suitable strain for the required purpose depends upon a number of factors, in particular upon the nature of the substrate and environmental conditions. Generally, hydrolytic enzymes, e.g. cellulases, xylanases, pectinases, etc. are produced by fungal cultures, since such enzymes are used in nature by fungi for their growth. Trichoderma spp. and Aspergillus spp. have most widely been used for these enzymes. Amylolytic enzymes too are commonly produced by filamentous fungi and the preferred strains belong to the species of Aspergillus and Rhizopus. Although commercial production of amylases is carried out using both fungal and bacterial cultures, bacterial a -amylase is generally preferred for starch liquefaction due to its high temperature stability. In order to achieve high productivity with less production cost, apparently, genetically modified strains would hold the key to enzyme production.

Substrates used for the production of enzymes in SSF systems

Agro-industrial residues are generally considered the best substrates for the SSF processes, and use of SSF for the production of enzymes is no exception to that. A number of such substrates have been employed for the cultivation of microorganisms to produce host of enzymes . Some of the substrates that have been used included sugar cane bagasse, wheat bran, rice bran, maize bran, gram bran, wheat straw, rice straw, rice husk, soyhull, sago hampas, grapevine trimmings dust, saw dust, corncobs, coconut coir pith, banana waste, tea waste, cassava waste, palm oil mill waste, aspen pulp, sugar beet pulp, sweet sorghum pulp, apple pomace, peanut meal, rapeseed cake, coconut oil cake, mustard oil cake, cassava flour, wheat flour, corn flour, steamed rice, steam pre-treated willow, starch, etc.. Wheat bran however holds the key, and has most commonly been used, in various processes.


 Aspects of design of fermenter for enzyme production in solid state fermentation systems

Over the years, different types of fermenters (bioreactors) have been employed for various purposes in SSF systems. Pandey8 reviewed the aspects of design of fermenter in SSF processes. Laboratory studies are generally carried out in Erlenmeyer flasks, beakers, petri dishes, roux bottles, jars and glass tubes (as column fermenter). Large-scale fermentation has been carried out in tray-, drum- or deep-trough type fermenters. The development of a simple and practical fermenter with automation, is yet to be achieved for the SSF processes.

Factors affecting enzyme production in solid state fermentation systems

The major factors that affect microbial synthesis of enzymes in a SSF system include: selection of a suitable substrate and microorganism; pre-treatment of the substrate; particle size (inter-particle space and surface area) of the substrate; water content and aw of the substrate; relative humidity; type and size of the inoculum; control of temperature of fermenting matter/removal of metabolic heat; period of cultivation; maintenance of uniformity in the environment of SSF system, and the gaseous atmos-phere, i.e. oxygen consumption rate and carbon dioxide evolution rate.

Enzymes produced by solid state fermentation processes

Ideally, almost all the known microbial enzymes can be produced under SSF systems. Literature survey reveals that much work has been carried out on the production of enzymes of industrial importance, like proteases, cellulases, ligninases, xylanases, pectinases, amylases, glucoamylases, etc.; and attempts are also being made to study SSF processes for the production of inulinases, phytases, tannases, phenolic acid esterases, microbial rennets, aryl-alcohol oxidases, oligosaccharide oxidases, tannin acyl hydrolase, a -L-arabinofuranosidase, etc. using SSF systems (cf. Table 2). In the following sections, a brief account of production on various enzymes in SSF systems is discussed.


L-glutaminase is considered a potent anti-leukamic drug and has found application as a flavour-enhancing agent in food industry. In a maiden report, Prabhu and Chandrasekaran reported L-glutaminase production by SSF using marine Vibrio costicola. Polystyrene was used as the inert substrate. They also evaluated several organic substrates for their ability to produce glutaminases by SSF using the same strain. Among the tested materials, wheat bran and rice bran were found superior in comparison to saw dust, coconut oil cake, and groundnut cake. However, use of polystyrene as the substrate offered several advantages over organic substrtes. For example, leachate from polystyrene-SSF system was not only less viscous but also showed high specific activity of the enzyme.



  • 1957
  • Isaacs and Lindenmann
  • Did an experiment using chicken cell cultures
  • Found a substance that interfered with viral replication and was therefore named interferon
  • Nagano and Kojima also independently discovered this soluble antiviral protein

Interferons (IFNs) are proteins made and released by lymphocytes in response to the presence of pathogens—such as viruses, bacteria, or parasites—or tumor cells. They allow communication between cells to trigger the protective defenses of the immune system that eradicate pathogens or tumors.

IFNs belong to the large class of glycoproteins known as cytokines. Although they are named after their ability to “interfere” with viral replication within host cells, IFNs have other functions: they activate immune cells, such as natural killer cells and macrophages; they increase recognition of infection or tumor cells by up-regulating antigen presentation to T lymphocytes; and they increase the ability of uninfected host cells to resist new infection by virus. Certain host symptoms, such as aching muscles and fever, are related to the production of IFNs during infection.

About ten distinct IFNs have been identified in mammals; seven of these have been described for humans. They are typically divided among three IFN classes: Type I IFN, Type II IFN, and Type III IFN. IFNs belonging to all IFN classes are very important for fighting viral infections.

What is Interferon?

  • Naturally occurring proteins and glycoproteins
  • Secreted by eukaryotic cells in response to viral    infections, tumors, and other biological inducers
  • Produce clinical benefits for disease states such   as hepatitis, various cancers, multiple sclerosis, and many other diseases
  • Structurally, they are part of the helical cytokine family which are characterized by an amino acid chain that is 145-166 amino acids long
  • bio-4


Penicillin was the first naturally occurring antibiotic discovered. It is obtained in a number of forms from Penicillium moulds. Penicillin is not a single compound but a group of closely related compounds, all with the same basic ring-like structure (a β-lactam) derived from two amino acids (valine and cysteine) via a tripeptide intermediate. The third amino acid of this tripeptide is replaced by an acyl group (R) and the nature of this acyl group produces specific properties on different types of penicillin.

There are two different types of penicillin.

Biosynthetic penicillin is natural penicillin that is harvested from the mould itself through fermentation.

Semi-synthetic penicillin includes semi synthetic derivatives of penicillin – like Ampicillin, Penicillin V, Carbenicillin, Oxacillin, Methicillin, etc. These compounds consist of the basic Penicillin structure, but have been purposefully modified chemically by removing the acyl group to leave 6-aminopenicillanic acid and then adding acyl groups that produce new properties.

These modern semi-synthetic penicillins have various specific properties such as resistance to stomach acids so that they can be taken orally, a degree of resistance to penicillinase (or β-lactamase) (a penicillin-destroying enzyme produced by some bacteria) and an extended range of activity against some Gram-negative bacteria. Penicillin G is the most widely used form and the same one we get in a hypodermic form.


Penicillin G is not stable in the presence of acid (acid-labile). Since our stomach has a lot of hydrochloric acid in it (pH2.0), if we were to ingest penicillin G, the compound would be destroyed in our stomach before it could be absorbed into the bloodstream, and would therefore not be any good to us as a treatment for infection somewhere in our body. It is for this reason that penicillin G must be taken by intramuscular injection – to get the compound in our bloodstream, which is not acidic at all. Many of the semi-synthetic penicillins can be taken orally.

Penicillium chrysogenum that produce antibiotics, enzymes or other secondary metabolites frequently require precursors like purine/pyrimidine bases or organic acids to produce said metabolites. Primary metabolism is the metabolism of energy production for the cell and for its own biosynthesis. Typically, in aerobic organisms (Penicillium chrysogenum) it involves the conversion of sugars such as glucose to pyruvic acid2 and the production of energy via the TCA cycle.

Secondary metabolism regards the production of metabolites that are not used in energy production for example penicillin from Penicillium chrysogenum. In this case the metabolite is being utilized as a defence mechanism against other microorganisms in the environment. In essence Penicillium chrysogenum can kill off the competition to allow itself to propagate efficiently. It should be noted that these secondary metabolites are only produced in times of stress when resources are low and the organism must produce these compounds to kill off its competitors to allow it to survive.


Lactose: 1%

Calcium Carbonate: 1%

Cornsteep Liquor: 8.5%

Glucose: 1%

Phenyl acetic acid: 0.5g

Sodium hydrogen phosphate: 0.4%

Antifoaming Agent: Vegetable oil


To begin the fermentation process, a number of these spores will be introduced into a small (normally 250-500ml) conical flask where it will be incubated for several days. At this stage, explosive growth is the most desired parameter and as such the medium in the flask will contain high amounts of easily utilisable carbon and nitrogen sources, such as starch and corn-steep liquor. At this stage, the spores will begin to revive and form vegetative cells. Temperature is normally maintained at 23-280C and pH at ~6.5, although there may be some changes made to facilitate optimum growth. The flask will often have baffles in it and be on a shaking apparatus to improve oxygen diffusion in the flask.

Once the overall conditions for growth have been established and there is a viable vegetative culture active inside the flask, it will be transferred to a 1 or 2 litre bench-top reactor. This reactor will be fitted with a number of instruments to allow the culture to be better observed than it was in the shake flask. Typical parameters observed include pH, temperature, and stirrer speed and dissolved oxygen concentration.

This allows tweaking of the process to occur and difficulties to be examined. For example, there may not be enough oxygen getting to the culture and hence it will be oxygen starved.  At this point, the cells should be showing filamentous morphology, as this is preferred for penicillin production. As before, cell growth is priority at this stage. At this stage, growth will continue as before, however, there are often sudden changes or loss in performance.

At this stage the medium being added to the reactor will change. Carbon and nitrogen will be added sparingly alongside precursor molecules for penicillin fed-batch style. Another note is that the presence of penicillin in the reactor is itself inhibitory to the production of penicillin. Therefore, we must have an efficient method for the removal of this product and to maintain constant volume in the reactor.

Other systems, such as cooling water supply, must also be considered. If all goes well we should have penicillin ready for downstream processing. From here it can be refined and packaged for marketing and distribution to a global market.


Lactic acid

First discovered by Scheele (1789) from sour milk. Later Pasteur (1857) identified the MO involved in the lactic acid production.

In the Year 1881, first commercial production was started by Cointon processing Company, Iowa based on fermentation process.

Lactic acid is commercially produced by the synthetic method and as well as fermentation process.

Lactic acid is largely used in pharma and some plastic industries.


  • Good solvent properties.
  • Provides acidity in foods and beverages and served as preservatives in food stuff.
  • Textile and laundry use lactic acid in fabric treatment.
  • Calcium lactate is employed in baking powder and as a source of calcium in pharma industries.
  • The pure form of lactic acid is used in plastic industry.

Carbon source :

glucose, maltose, sucrose or lactose

Crude substrate such as corn starch, potato starch, rice starch, lolassed have been used to supply carbon in the production medium.

Pre-treatment to starchy materials by enzyme or acid  is necessary to bring about hydrolysis to maltose and glucose.

The sugar concentration in the production medium is initially adjusted to 5-20%.

Nitrogen source:

Ammonium salts have been used. For eg. Ammonium hydrogen phosphate in the concentration of 0.25% is used (USA).

Growth factors and mineral source:

Vitamin B-complexes.

Those may be supplied by enriching the medium with crude vegetable sources.

pH : 5.5 -6.5

Temperature :

45-50o  C for L. bulgaricus / 30o C for L. casei, L. pentosus

Recovery :

A major problem in lactic acid production is that of product recovery and not of fermentation.

The method to be employed for recovery depends on the type  of grade required.

There are different tuypes of grades needed for different purposes. Viz.

  • Food grade
  • Technical grade
  • Plastic grade
  • Bio1Bio-2

Food preservation Methods


Food preservation involves preventing the growth of bacteriafungi (such as yeasts), or other micro-organisms (although some methods work by introducing benign bacteria or fungi to the food), as well as retarding the oxidation of fats that cause rancidity. Food preservation may also include processes that inhibit visual deterioration, such as the enzymatic browning reaction in apples after they are cut during food preparation.


Cooling preserves foods by slowing down the growth and reproduction of micro-organisms and the action of enzymes that cause food to rot. The introduction of commercial and domestic refrigerators drastically improved the diets of many in the Western world by allowing foods such as fresh fruit, salads and dairy products to be stored safely for longer periods, particularly during warm weather.


Freezing is also one of the most commonly used processes, both commercially and domestically, for preserving a very wide range of foods, including prepared foods that would not have required freezing in their unprepared state. For example, potato waffles are stored in the freezer, but potatoes themselves require only a cool dark place to ensure many months’ storage. Cold stores provide large-volume, long-term storage for strategic food stocks held in case of national emergency in many countries.


Heating to temperatures which are sufficient to kill microorganisms inside the food is a method used with perpetual stews. Milk is also boiled before storing to kill many microorganisms.


Salting or curing draws moisture from the meat through a process of osmosis. Meat is cured with salt or sugar, or a combination of the two. Nitrates and nitrites are also often used to cure meat and contribute the characteristic pink color, as well as inhibition of Clostridium botulinum. It was a main method of preservation in medieval times and around the 1700s.


The earliest cultures have used sugar as a preservative, and it was commonplace to store fruit in honey. Similar to pickled foods, sugar cane was brought to Europe through the trade routes. In northern climates without sufficient sun to dry foods, preserves are made by heating the fruit with sugar “Sugar tends to draw water from the microbes (plasmolysis). This process leaves the microbial cells dehydrated, thus killing them. In this way, the food will remain safe from microbial spoilage.” Sugar is used to preserve fruits, either in ananti-microbial syrup with fruit such as applespearspeachesapricots and plums, or in crystallized form where the preserved material is cooked in sugar to the point of crystallization and the resultant product is then stored dry.


Smoking is used to lengthen the shelf life of perishable food items. This effect is achieved by exposing the food to smoke from burning plant materials such as wood. Smoke deposits a number of pyrolysis products onto the food, including the phenols syringolguaiacol andcatechol. These compounds aid in the drying and preservation of meats and other foods. Most commonly subjected to this method of food preservation re meats and fish that have undergone curingFruits and vegetables like paprikacheesesspices, and ingredients for making drinks such as malt and tea leaves are also smoked, but mainly for cooking or flavoring them. It is one of the oldest food preservation methods, which probably arose after the development of cooking with fire.


Pickling is a method of preserving food in an edible anti-microbial liquid. Pickling can be broadly classified into two categories: chemical pickling and fermentation pickling.

In chemical pickling, the food is placed in an edible liquid that inhibits or kills bacteria and other micro-organisms. Typical pickling agents include brine (high in salt), vinegar,alcohol, and vegetable oil, especially olive oil but also many other oils. Many chemical pickling processes also involve heating or boiling so that the food being preserved becomes saturated with the pickling agent. Common chemically pickled foods include cucumberspepperscorned beefherring, and eggs, as well as mixed vegetables such as piccalilli.


Sodium hydroxide (lye) makes food too alkaline for bacterial growth. Lye will saponify fats in the food, which will change its flavor and texture. Lutefisk uses lye in its preparation, as do some olive recipes. Modern recipes for century eggs also call for lye.


Canning involves cooking food, sealing it in sterile cans or jars, and boiling the containers to kill or weaken any remaining bacteria as a form of sterilization. It was invented by the French confectioner Nicolas Appert. By 1806, this process was used by the French Navy to preserve meat, fruit, vegetables, and even milk. Although Appert had discovered a new way of preservation, it wasn’t understood until 1864 when Louis Pasteur found the relationship between microorganisms, food spoilage, and illness.

Foods have varying degrees of natural protection against spoilage and may require that the final step occur in a pressure cooker. High-acid fruits like strawberries require no preservatives to can and only a short boiling cycle, whereas marginal vegetables such as carrotsrequire longer boiling and addition of other acidic elements. Low-acid foods, such as vegetables and meats, require pressure canning. Food preserved by canning or bottling is at immediate risk of spoilage once the can or bottle has been opened.



Food may be preserved by cooking in a material that solidifies to form a gel. Such materials include gelatinagarmaize flour, and arrowroot flour. Some foods naturally form aprotein gel when cooked, such as eels and elvers, and sipunculid worms, which are a delicacy in Xiamen, in the Fujian province of the People’s Republic of China.


Meat can be preserved by jugging. Jugging is the process of stewing the meat  in a covered earthenware jug or casserole. The animal to be judged is usually cut into pieces, placed into a tightly-sealed jug with brine or gravy, and stewed. Red wine and/or the animal’s own blood is sometimes added to the cooking liquid. Jugging was a popular method of preserving meat up until the middle of the 20th century.


Burial of food can preserve it due to a variety of factors: lack of light, lack of oxygen, cool temperatures, pH level, or desiccants in the soil. Burial may be combined with other methods such as salting or fermentation. Most foods can be preserved in soil that is very dry and salty (thus a desiccant) such as sand, or soil that is frozen.


Fermented foods are created by allowing one type of microbe to act on a food substance in order to convert some of its components into alcohols or acids. Alcohols are fermented by yeasts, while most foods are fermented by lactic acid bacteria. Some mold-ripened cheeses are created by the work of fungi, and other cheeses are fermented by the work of bacterial cultures. This family of preserved foods includes some of the world’s greatest culinary treasures, including bread, cheese, pickles, sauerkraut, chocolate, beer, coffee, wine and a whole host of cured meats, to name but a few.

The bacteria, yeasts and fungi necessary to ferment different foods can be naturally occurring or wild, as it was for each of these marvelous foods to have been discovered in the first place. Or it can be purposefully cultured with ingredients obtained via cheesemaking or home brew suppliers. To try fermentation at home, start with the simple recipe for sauerkraut below.


Many foods last longer if they are simply dunked in a bath of vinegar. Just as vinegar rids dirty clothes and kitchen countertops of infectious germs, it can be put to the same—though tastier—use with fruits, vegetables and herbs. The most famous vinegar-preserved foods are cucumbers (though some cucumber pickles are actually fermented), but many other foods are delicious in vinegar, too—turnips, beets, radishes, carrots, leeks, kale, garlic scapes, Swiss chard, green beans, cauliflower, zucchini, peppers, asparagus, cantaloupe and green tomatoes are just some of the options that are delicious when pickled. From balsamic and apple cider to rice and champagne, a wide world of vinegar flavors awaits. The recipe above provides a supersimple way to preserve fresh cucumbers using acidification.

Drying Food 

Dehydrating food makes it less attractive to moisture-loving bacteria. Removing the water also concentrates flavors in a mighty tasty way, and it’s a fitting trick for fruits and veggies of all kinds. Dried foods take up the least pantry space of all the preserved treats you might make, and the benefactors of this technique are limited only by your imagination. Food dehydrators make easy work of drying food, but it’s easy to do in an oven set on low heat, too. Once they’re dried to a crisp, store foods in an airtight container. Some foods, such as plum tomatoes, are also great halfway dried and then stored in oil.

Root Cellaring

The practice of “putting food by” refers to storing produce for long periods of time, and it is often quite simple. Many foods will last weeks or months if kept in a cool, dark spot. Some foods benefit from being coated first in oil or being stored in a bucket of sand; others will keep when simply set on a shelf. You can build a fancy ventilated root cellar if you’ve got the space, time and inclination, but a cool, dark corner of your garage or basement will probably do nicely.

Home Canning

From simple canned tomatoes to homemade soups, canning is a great way to preserve the peak-harvest flavors of many fresh foods. However, it is extremely important to do it right, so be sure to learn the basics. While canning is simple and safe with the proper instruction, improperly canned foods can make you and your family sick. The easiest method of canning is called water-bath canning, and it’s a great way to preserve acidic foods such as pickles and tomatoes. For nonacidic foods, you will need to rely on the more complex system of pressure canning. We recommend starting with the easier water-bath canning to learn the technique before moving on to pressure canning.

Freezing Food

Freezing helps prevent food from spoiling before we’re ready to eat it. Several tricks and tips can improve your freezer strategies. Many foods freeze well, but a few—such as lettuce, cream sauces and whole eggs in shells—really just don’t. Obviously, it’s helpful to know the difference. Some foods, such as blueberries, can be frozen as is; others, such as greens, must be blanched first. To blanch, bring a pot of water to boil, dunk food for a brief time, then pat the food dry and freeze in freezer proof containers. To make efficient use of freezer space, try freezing liquids such as soups in baggies laid flat on a baking sheet. Once frozen, they can be stacked neatly elsewhere in the freezer. You can also fill ice cube trays with sauces such as pesto and then pour the cubes, ready for single-serving uses, into a freezer container.


Solid Water Pollution

Solid waste is a collective term used to distinguish non-biodegradable materials and discards that come from sources like:

  • Households
  • Businesses and Commercial establishments
  • Manufacturers or Industrial sites
  • Biomedical sources like hospital and clinics.

They are the trash collected by the municipal waste management units for segregation according to the process of disposal.

Solid wastes are generally composed of nonbiodegradable and non-compostable biodegradable materials. The latter refer to solid wastes whose biodeterioration is not complete; in the sense that the enzymes of microbial communities that feed on its residues cannot cause its disappearance or conversion into another compound.

Parts of liquid waste materials are also considered as solid wastes, where the dredging of liquid wastes will leave solid sedimentation, to which proper waste management techniques should also be applied.

  • What Is Pollution Caused by Solid Waste?


Solid waste pollution is when the environment is filled with nonbiodegradable and non-compostable biodegradable wastes that are capable of emitting greenhouse gases, toxic fumes, and particulate matters as they accumulate in open landfills.

These wastes are also capable of leaching organic or chemical compositions to contaminate the ground where such wastes lay in accumulation.

Solid wastes carelessly thrown in streets, highways, and alleyways can cause pollution when they are carried off by rainwater run-offs or by flood water to the main streams, as these contaminating residues will reach larger bodies of water.

  • The Effects of This Pollution to Climate Changes

Studies by scientists at the National Academy of Sciences reveal that the Earth’s surface temperature has increased by one degree Fahrenheit in the last century. However, what was alarming was the noticeable acceleration of warming temperatures during the last two decades. Stronger evidences have connected the acceleration to the mounting presence of greenhouse gases, namely:

  • Carbon Dioxide
  • Methane
  • Nitrous Oxide .

Most of these greenhouse gases emanate from the chemical compositions widely used for human activities during the past 50 years. Scientists believe that the increase in carbon dioxide by at least 30 percent can be traced back to the initial years of industrialization.

Additional human activities, which involved the use and consumption of industrially manufactured products, including the use of automobiles and its fossil fuel, all contributed to the sudden surge of heat-trapping greenhouse gases in the Earth’s atmosphere. In addition, power generating plants used by industries and consumers alike, contribute 98 percent to carbon dioxide emissions, 24 percent to methane emissions and 18 percent to nitrous oxide.

However, use and consumption is one thing, the accumulation of the non-biodegradable waste in landfills is another. The discarded materials still containing much of the chemical ingredients used in the manufacture of these products created mountainous landfills. The concentration of solid wastes reacting to heat, moistures and air as they lay exposed to the environment also meant a concentration of greenhouse gas emissions.

While in this state, they contributed to the release of greenhouse gases in the Earth’s warming atmosphere. A 1997 survey of total global greenhouse gas emissions showed that about one-fifth of these emissions emanated from the United States.

This is why solid waste management solutions are considered important, in order to lessen the greenhouse gas being added by solid wastes, to global warming climate change.

  • The Importance of Solid Waste Management

One important aspect of solid waste management (SWM) is the segregation process that ensures proper disposal of solid wastes. Segregation at SWM units includes the classification of wastes into: (1) municipal solid wastes and (2) hazardous solid wastes.

At this point, consumers should be aware that segregation alone requires tremendous costs.

Basic Facts about Municipal Solid Wastes (MSW)

MSWs are mostly discards coming from human activities like, but not limited to:

  • Product packaging
  • Furniture
  • Clothing
  • Newspapers
  • Paint and paint cans
  • Bottles
  • Batteries
  • Electronic appliances and devices
  • Food scraps
  • Grass clippings
  • Other refuse

Studies show that from a 1960 figure of 2.7 million tons of MSW generated in the US, the figure dramatically increased through the years, reaching a total approximation of 232 million tons by the year 2000. This was further equated as equivalent to 4.5 pounds of waste per person per day in contrast to the 1960 figure, which was equivalent to 2.7 pounds of waste per person per day.

Basic Facts about Hazardous Wastes

Hazardous wastes and their use on land result in refuse and discards requiring proper disposal. These wastes contain nutrients and chemicals that contaminate the air and soil, often reaching groundwater levels.

In spent-washes that contain hazardous wastes, their sedimentations are carried by water run-offs to streams and bodies of water, which tend to contaminate drinking water sources.

  • Learn the procedures employed in solid waste management and know the procedures observed in solid waste disposal . What is solid wastes that one of its remedies Include product bans and restrictions and why do communities implement strict measures for waste reduction? Understand the costs entailed in order to manage solid wastes.

Solid Waste Management of Hazardous Wastes

Household Hazardous Wastes (HHW)

Examples of HHWs are :

  • Discarded paint materials and their implements, such as brushes, rollers, trays and paint containers
  • Cleaners in the forms of solvents
  • Oils
  • Batteries
  • Pesticides
  • Other leftover portions of materials and implements containing chemicals, particularly those that are classified as volatile organic compounds or VOCs.


Generally, municipal landfills can accept HHWs, in which the SWM units will be responsible for handling their disposal. However, recent developments and the costs entailed to manage household wastes have caused the implementation of certain local laws.

Industrial Hazardous Wastes

Industrial hazardous waste generators, like manufacturing plants, businesses, laboratories, and universities, are under strict government regulations. They are held responsible and accountable for the proper containment and disposal of their hazardous wastes.

  • Methods of Solid Waste Disposal

The following SWM disposal practices have been established and are required to be observed in the following order of hierarchy:

(1) Source Reduction

(2) Recycling and Composting

(3) Combustion/Incineration

(4) Landfills

(1) Source Reduction Techniques

Refuse – Environmentalists suggest that another R should be added to the governing principles of waste management, which stands for Refuse. Consumers, as major contributors to solid waste increments, should refuse to use products that make use of packaging or implements made from nonbiodegradable or non-compostable biodegradable materials.

Bans and Restrictions – Some local government units have implemented local laws that exclude nonbiodegradable materials as part of household wastes. Community members who insist on using these materials shall be responsible for their proper disposal. The cost of solid waste management facilities and equipment are taking their toll on community coffers; hence, the matter of source reduction should begin at the consumer level as they become the end-generators of such wastes.

  • The State of Massachusetts, for example, has specifically banned televisions and computer monitors from inclusion in landfills.
  • The State of Minnesota has banned the sale of mercury-filled thermometers, while any other devices, appliances, gadgets, or implements containing mercury are being banned from landfills. The state is also considering the banning of unprocessed MSW such as yard wastes.
  • The State of Illinois has completely banned appliances, implements, and gadgets that contain toxic wastes, which include Freon and chlorofluorocarbon refrigerants, from inclusion in landfills.
  • Accordingly, there are now twenty-two states that ban the inclusion of yard wastes such as leaves, grass clipping, computer paper, newsprint, paper board, plastic, glass, aluminum and steel containers, tires and lead-acid batteries just to name some of the banned solid wastes that used to form part of MSWs.
  • The main considerations for this banning, aside from pollution, are the costs entailed in providing and maintaining solid waste management solutions and facilities for the proper waste disposal of MSW.


Deposit and Refund Systems – Commercial methods of MSW source reduction include the deposit and refund system, which enables the manufacturer to recycle and reuse the containers and packages. To ensure their return, consumers pay fees to be refunded upon the return of the nonbiodegradable material, thereby facilitating the collection and authorized return of packaging materials to its manufacturer.


Donation, Sale and Disposal – Materials that are otherwise discarded and included in landfills are donated to materials exchange centers where they can be properly distributed for recycling, repurposing, and reclaiming methods as ways to reduce solid wastes. Solid wastes included under this program are building materials, furniture, computers, clothing, and appliances.

Methods of Solid Waste Disposal

(2) Recycling Methods Including Composting

Different methods of recycling apply to different types of solid wastes and are often designed as sustainable methods:

  • Composting involves careful selection of materials regarded as compostable biodegradable and purely compostable organic materials. For more information on compostable solid wastes, please refer to a separate article about “Defining Biodegradable and Comparing to Compostable”.
  • Repurposing and Reclaiming Scrap Components

Electronic appliances and various electrical products produce scrap wastes, which provide a secondary supply of reusable materials like:

  1. Metals, which may include, gold, silver, platinum, iron, copper, aluminum, nickel zinc, tin and lead,
  2. Minerals like mercury and cadmium,
  3. Halogens like arsenic, bromine, and chlorine
  4. Organic plastics
  5. Glass
  6. Ceramics

The recycling of these valuable components reduces the need for mining and other outsourcing methods but requires efficient technical recycling processes and effective emission controls.

  • Recycling of PET Bottles

Sustainable methods of recycling PET bottles are also in place as they are used in textile manufacturing. Details about this recycling method can be gleaned from the article about “Polyester fiber from Recycled Bottles Providing Cost Efficiency in Textile Manufacture”.

  • Recycling of HDPE Plastics

Sustainability in the method of recycling high-density polyethylene or HDPE plastics, otherwise known as plastic No. 2, makes use of technologies that convert these plastic materials into polywood or poly lumber. These are ideal for use in outdoor furniture as they posses the durability and weather resistance required for outdoor use. See this related article about “Ending the Search for Patio Sets Made from Recycled Materials” for more information.

Other innovative and creative methods of recycling materials at household levels are, likewise, means of reducing MSW management costs.


(3) Combustion or Incineration of Solid Wastes

This is the process of burning MSWs in a way that will generate energy and at the same time reduce the amount of solid wastes left in open landfills. However, this method operates under the regulation of the Environmental Protection Agency’s Office of Air and Radiation, inasmuch as air emissions are the main environmental concerns. Accordingly, there are about 102 combustors which have been operating in the US since the year 2000, and being used for energy recovery. They are said to have the capacity to burn as much as 96,000 tons of MSWs in a day.

  • (4) Landfills

Landfills are the last in the hierarchy of solid waste management solutions, and the aim is to reduce the number of landfills operating on U.S. soil. Although smaller landfills have been eliminated, which resulted in a decrease in the number of landfills from 8,000 to 1,967 by the year 2000, they have been replaced by larger and newer landfills, because the increase in solid waste has remained constant.

Landfills are regulated primarily by the state laws and local government laws, all of which, take into consideration existing tribal laws in the areas where landfills operate. These regulating units implement sets of standards, which landfill operations should meet.


In understanding what is solid waste and the effects of solid waste pollution, we are drawn to the conclusion that consumers can help hasten the achievement of zero-wastes in the environment,by minimizing, if not eliminating the use of nonbiodegradable or solid wastes.


Marine Pollution

Marine pollution includes a range of threats including from land-based sources, oil spills, untreated sewage, heavy siltation, eutrophication (nutrient enrichment), invasive species, persistent organic pollutants (POP’s), heavy metals from mine tailings and other sources, acidification, radioactive substances, marine litter, overfishing and destruction of coastal and marine habitats (McCook 1999, Nyström et al. 2000, Bellwood et al. 2004). Overall, good progress has been made on reducing Persistent organic pollutants (POP’s), with the exception of the Arctic. Oil discharges and spills to the Seas has been reduced by 63% compared to the mid-1980’ies, and tanker accidents have gone down by 75%, from tanker operations by 90% and from industrial discharges by some 90%, partly as a result of the shift to double-hulled tankers (UNEP, 2006; Brown et al., 2006). Some progress on reducing emissions of heavy metals is reported in some regions, while increased emissions are happening in others. Electronic waste and mine tailings are included amongst the sources of heavy metal pollution in Southeast Asia. Sedimentation has decreased in some areas due to reduced river flows as a result of terrestrial overuse for agricultural irrigation, while increasing in other regions as a result of coastal development and deforestation along rivers, water sheds and costal areas, and clearing of mangroves (Burke et al., 2002; McCulloch et al., 2003; Brown et al., 2006; UNEP, 2004, 2006).

A major threat beyond overexploitation of fisheries and physical destruction of marine coastal habitats by dredging, is undoubtedly the strong increase in coastal development and discharge of untreated sewage into the near-shore waters, resulting in enormous amounts of nutrients spreading into the sea and coastal zones. This, together with changes in salinity, melting sea ice, increased sea temperatures and future changes in sea currents may severely affect marine life and their ability to recover from extreme climatic

Together with agricultural run-off to the Sea or into major rivers and eventually into the ocean, Nitrogen (mainly nitrate and ammonium) exports to the marine environment are projected to increase at least 14% globally by 2030 (UNEP, 2006). In Southeast Asia more than 600,000 tons of Nitrogen are discharged annually from the major rivers.

These numbers may become further exacerbated as coastal populations are depicted to increase from 77 people/km2 to 115 people per km2 in 2025. In Southeast Asia, the numbers are much higher and the situation more severe. Wetlands and mangroves are also declining rapidly, typically by 50-90% in most regions in the past 4 decades (UNEP, 2006). All of the above, together with changes in salinity, melting sea ice, increased sea temperatures and future changes in sea currents may severely affect marine life and its ability to recover from extreme climatic events.

Also, it will severely exacerbate the effects of extreme weather and the productivity of coastal ecosystems to supply livelihoods and basic food to impoverished. Hence, the poor management of sewage not only presents a dire threat to health and ecosystems services, it may increase poverty, malnutrition and security for over a billion people.