National Environmental Management: Waste Act, 2008 (Act No. 59 of 2008)

Mechanical:

Briquetting

A briquette (or briquet) is a compressed block of coal dust or other combustible biomass material such as charcoal,sawdust, wood chips, peat, or paper used for fuel and kindling to start a fire. Biomass briquettes are a biofuel substitute to coal and charcoal containing untreated biomass waste.

Centrifuge

A centrifuge is a device, which employs a high rotational speed to separate components of different densities. This becomes relevant in the majority of industrial jobs where solids, liquids and gases are merged into a single mixture and the separation of these different phases is necessary. A decanter  centrifuge separates solid materials from liquids in slurry and therefore plays an important role in waste water treatment, chemical, oil and food processing industries. There are several factors that affect the performance of a decanter centrifuge and some design heuristics to be followed which are dependent upon given applications.

Chipping

Chipping Is the process of reducing woody waste to smaller pieces mechanically to speed up decomposition of the material. Once chipped, the woody material can be used as mulch, for composting, as a fuel source or even compressed fora slower burning fuel source.

Pelleting

Compressing of organic matter to create a dense, low moisture fuel source. Pellets can be made from industrial waste and co-products, food waste, agricultural residues,energy crops, and virgin lumber.

Sonification

Sonification is the act of of applying sound energy to agitate particles in a sample, for various purposes.

Chemical:

Chemical hydrolysis

Hydrolysis is a type of decomposition reaction where one reactant is water. Typically, water is used to break chemical bonds on the other reactants.  Sometimes this addition causes both substances and water molecule to split into two parts. In such reactions, one fragment of the target molecule (or parent molecule) gains a hydrogen ion.

Chemical oxidation

Chemical oxidation is a process involving the transfer of electrons from the chemical species being oxidized to the oxidizing agent. Oxidation chemically converts hazardous contaminants to non-hazardous or less toxic compounds that are more stable, less mobile, and/or inert. The oxidizing agents most commonly used are ozone, hydrogen peroxide, hypochlorites, chlorine, and chlorine dioxide. In water and wastewater engineering, chemical oxidation serves the purpose of converting putrescible pollutant substances to innocuous or stabilised products.

Transesterification

Animal and plant fats and oils are composed of triglycerides, which are esters formed by the reactions of three free fatty acids and the trihydric alcohol, glycerol. In the transesterification process, the added alcohol (commonly, methanol or ethanol) is deprotonated with a base to make it a stronger nucleophile.

Saponification

Soaps are sodium or potassium salts of long chain fatty acids. When triglycerides in fat/oil react with aqueous NaOH or KOH, they are converted into soap and glycerol. This is called alkaline hydrolysis of esters. Since this reaction leads to the formation of soap, it is called the Saponification process.

Anaerobic:

Anaerobic digestion

Anaerobic digestion is a fermentation process that causes the breakdown of organic compounds without the presence of oxygen. This process reduces, nitrogen to ammonia and produces organic acids. Carbon from organic compounds is released mainly as methane gas (CH4). A small portion of carbon may be respired as CO2. The decomposition occurs as four stages namely: hydrolysis, acidogenesis, acetogenesis, and methanogenesis.

Anaerobic Composting

Anaerobic composting is an anaerobic process that uses microorganisms to ferment organic waste in an acidic environment and prevent the putrifiication of such waste. The Bokashi treatment process is one such process that has an initial stage of anaerobic composting where a specifically selected group of microorganisms is added to the organic waste through a dry carrier such as an inoculated carbon source (e.g. wheat bran) or via a liquid form such as a microbial spray which ferments the organic waste in a closed system and avoids the production of unfavourable by-products

Aerobic:

Aerobic digestion

Aerobic digest on is a process in sewage treatment designed to reduce the volume of sewage sludge and make it suitable for subsequent use. More recently technology has been developed that allows the treatment and reduction of other organic waste, such as food, cardboard and horticultural waste. It is a bacterial process occurring in the presence of oxygen. Bacteria rapidly consume organic matter and convert it into carbon dioxide, water and a range of lower molecular weight organic compounds. Naturally, one of the most  important benefits of aerobic composting is that the heat which is produced during the decomposition process is great enough that it kills harmful bacteria and pathogens within the pile.

Black soldier fly larvae

Valorisation of organic waste through larval feeding activity of the black soldier fly, Hermetia illucens provides waste reduction and stabilisation while providing a product in form of the last larval stage, the so-called prepupae, which offers a valuable additive in animal feed.

Vermicomposting

When a variety of worms, including earthworms, digest organic, mainly food waste, the product is called vermicompost, which consists of partially decomposed food waste, organic bedding material and vermicast.

Thermal:

Aqueous phase reforming

The reaction of biomass-derived oxygenated compounds (E.g. glycerol) in aqueous solution at low temperature in the presence of a platinum catalyst to produce hydrogen.

Combustion

Combustion is an exothermic chemical reaction that produces heat and light.  The most common form of combustion is fire. Most forms of combustion happen when the gas oxygen joins with another substance.  For example, when wood burns, oxygen in the air joins with carbon in wood.

Drying

Application of heat to evaporate water from organic waste. Either direct or indirect heating methods are used. In the most common case, a gas stream, e.g., air, applies the heat by convection and carries away the vapor as humidity. Other possibilities are vacuum drying, where heat is supplied by conduction or radiation (or microwaves), while the vapor thus produced is removed by the vacuum system. Another indirect technique is drum drying (used, for instance, for manufacturing potato flakes), where a heated surface is used to provide the energy, and aspirators draw the vapor outside the room. In contrast, the mechanical extraction of the solvent, e.g., water, by centrifugation, is not considered "drying" but rather "draining".

Gasification

Gasification is a process that converts organic or fossil fuel based carbonaceous materials such as coal, petroleum coke (petcoke), biomass or waste, into carbon monoxide, hydrogen and carbon dioxide (synthesis gas or syngas). This is achieved by reacting the material at high temperatures (>700 °C), without combustion, with a controlled amount of oxygen and/or steam.

The syngas can be burned to produce electricity or further processed to manufacture chemicals, fertilizers, liquid fuels, substitute natural gas (SNG),or hydrogen.

Hydrothermal Carbonisation (HTC)

HTC is a chemical process for the conversion of organic compounds to structured carbons. It can be used to reduce the water content of the digestate / fertilizer and convert the solid fraction into "green coal" or brown coal formation (coalification).

Hydrothermal Liquefaction (HTL)

Hydrothermal liquefaction of biomass is the thermochemical conversion of biomass into liquid fuels by processing in a hot, pressurized water environment for sufficient time to break down the solid biopolymeric structure to mainly liquid components. Typical hydrothermal processing conditions are 523-647 K of temperature and operating pressures from 4 to 22 MPa of pressure.

Pressure heating / Supercritical water gasification (SCWG)

Mechanism using heat and pressure to improve char and lighter gases in biomass.

Pyrolysis

Pyrolysis is a thermochemical decomposition of organic material at elevated temperatures in the absence of oxygen (or any halogen). It involves the simultaneous change of chemical composition and physical phase, and is irreversible. The word is coined from the Greek-derived elements pyre "fire" and lysis "separating". This reaction involves molecular breakdown of larger molecules into smaller molecules in presence of heat. Pyrolysis is also known as thermal cracking, cracking, thermolysis, depolymerization, etc.

Rendering

Rendering is a process that converts waste animal tissue into stable, value-added materials.  The rendering process simultaneously dries the material and separates the fat from the bone and protein. A rending process yields a fat commodity (yellow grease, choice white grease, bleachable fancy tallow, etc.) and a protein meal (meat and bone meal, poultry by-product meal, etc.).

Rendering plants often also handle other materials, such as slaughterhouse blood, feathers and hair, but do so using processes distinct from true rendering.

Torrefaction

A thermal process to convert biomass into a coal-like material, which has better fuel characteristics than the original biomass. Torrefied biomass is more brittle, making grinding easier and less energy intensive.

Livestock Feed

Bio-processing (feeding of organic waste to domestic and livestock animals)

Livestock animals function as bio-processors for converting organic of organic waste, including food waste, into meat, eggs, and milk. Organic waste and food waste process nutritive properties and hence can be used as feed for domestic and livestock animals. Heat treatment of food waste prior to animal feeding is a global requirement with temperature and duration varying by country as well as depending on specific treatment processes. There are three broad treatment categories: wet-based, dry-based, and ensiling/fermentation. Wet-based methods typically include a simple heating step to sterilize the raw organic waste, rendering it safe for feeding to animals. Dry-based treatment combines heating (sterilization) with a drying step to produce feeds with an extended shelf life that are easier to handle. Ensiling/fermentation treatment typically consists of the heating-sterilization process followed by the addition of prescribed microbial/yeast agents. The latter utilizes readily degradable substrates, stabilizing the material while helping retain the nutrients.