using waste as a fuel source for cooking or heating and the use of the gas fuel (see above), to fuel for boilers to generate steam and electricity in a turbine. pyrolysis and gasification are two related forms of thermal treatment where waste materials are heated to high temperatures with limited oxygen availability. the process usually occurs in a sealed vessel under high pressure. pyrolysis of solid waste converts the material into solid, liquid and gas products. the liquid and gas can be burnt to produce energy or refined into other chemical products (chemical refinery). the solid residue (char) can be further refined into products such as activated carbon. gasification and advanced plasma arc gasification are used to convert organic materials directly into a synthetic gas (syngas) composed of carbon monoxide and hydrogen. the gas is then burnt to produce electricity and steam. an alternative to pyrolysis is high temperature and pressure supercritical water decomposition (hydrothermal monophasic oxidation). pyrolysis pyrolysis is often used to convert many types of domestic and industrial residues into a recovered fuel. different types of waste input (such as plant waste, food waste, tyres) placed in the pyrolysis process potentially yield an alternative to fossil fuels. pyrolysis is a process of thermo-chemical decomposition of organic materials by heat in the absence of stoichiometric quantities of oxygen; the decomposition produces various hydrocarbon gases. during pyrolysis, the molecules of object vibrate at high frequencies to an extent that molecules start breaking down. the rate of pyrolysis increases with temperature. in industrial applications, temperatures are above 430 °c (800 °f). slow pyrolysis produces gases and solid charcoal. pyrolysis hold promise for conversion of waste biomass into useful liquid fuel. pyrolysis of waste wood and plastics can potentially produce fuel. the solids left from pyrolysis contain metals, glass, sand and pyrolysis coke which does not convert to gas. compared to the process of incineration, certain types of pyrolysis processes release less harmful by-products that contain alkali metals, sulphur, and chlorine. however, pyrolysis of some waste yields gases which impact the environment such as hcl and so2. resource recovery main article: resource recovery resource recovery is the systematic diversion of waste, which was intended for disposal, for a specific next use. it is the processing of recyclables to extract or recover materials and resources, or convert to energy. these activities are performed at a resource recovery facility. resource recovery is not only environmentally important, but it is also cost-effective. it decreases the amount of waste for disposal, saves space in landfills, and conserves natural resources. resource recovery (as opposed to waste management) uses lca (life cycle analysis) attempts to offer alternatives to waste management. for mixed msw (municipal solid waste) a number of broad studies have indicated that administration, source separation and collection followed by reuse and recycling of the non-organic fraction and energy and compost/fertilizer production of the organic material via anaerobic digestion to be the favoured path. as an example of how resource recycling can be beneficial, many items thrown away contain metals that can be recycled to create a profit, such as the components in circuit boards. wood chippings in pallets and other packaging materials can be recycled to useful products for horticulture. the recycled chips can cover paths, walkways, or arena surfaces. application of rational and consistent waste management practices can yield a range of benefits including: economic – improving economic efficiency through the means of resource use, treatment and disposal and creating markets for recycles can lead to efficient practices in the production and consumption of products and materials resulting in valuable materials being recovered for reuse and the potential for new jobs and new business opportunities. social – by reducing adverse impacts on health by proper waste management practises, the resulting consequences are more appealing civic communities. better social advantages can lead to new sources of employment and potentially lifting communities out of poverty especially in some of the developing poorer countries and cities. environmental – reducing or eliminating adverse impacts on the environment through reducing, reusing and recycling, and minimizing resource extraction can result in improved air and water quality and help in the reduction of greenhouse gas emissions. inter-generational equity – following effective waste management practises can provide subsequent generations a more robust economy, a fairer and more inclusive society and a cleaner environment. waste valorization this section is an excerpt from waste valorization. waste valorization, beneficial reuse, value recovery or waste reclamation is the process of waste products or residues from an economic process being valorized (given economic value), by reuse or recycling in order to create economically useful materials. the term comes from practices in sustainable manufacturing and economics, industrial ecology and waste management. the term is usually applied in industrial processes where residue from creating or processing one good is used as a raw material or energy feedstock for another industrial process. industrial wastes in particular are good candidates for valorization because they tend to be more consistent and predictable than other waste, such as household waste. historically, most industrial processes treated waste products as something to be disposed of, causing industrial pollution unless handled properly. however, increased regulation of residual materials and socioeconomic changes, such as the introduction of ideas about sustainable development and circular economy in the 1990s and 2000s increased focus on industrial practices to recover these resources as value add materials. academics focus on finding economic value to reduce environmental impact of other industries as well, for example the development of non-timber forest products to encourage conservation. liquid waste-management liquid waste is an important category of waste management because it is so difficult to deal with. unlike solid wastes, liquid wastes cannot be easily picked up and removed from an environment. liquid wastes spread out, and easily pollute other sources of liquid if brought into contact. this type of waste also soaks into objects like soil and groundwater. this in turn carries over to pollute the plants, the animals in the ecosystem, as well as the humans within the area of the pollution. industrial wastewater this section is an excerpt from industrial wastewater treatment. wastewater from an industrial process can be converted at a treatment plant to solids and treated water for reuse. industrial wastewater treatment describes the processes used for treating wastewater that is produced by industries as an undesirable by-product. after treatment, the treated industrial wastewater (or effluent) may be reused or released to a sanitary sewer or to a surface water in the environment. some industrial facilities generate wastewater that can be treated in sewage treatment plants. most industrial processes, such as petroleum refineries, chemical and petrochemical plants have their own specialized facilities to treat their wastewaters so that the pollutant concentrations in the treated wastewater comply with the regulations regarding disposal of wastewaters into sewers or into rivers, lakes or oceans.: 1412 this applies to industries that generate wastewater with high concentrations of organic matter (e.g. oil and grease), toxic pollutants (e.g. heavy metals, volatile organic compounds) or nutrients such as ammonia.: 180 some industries install a pre-treatment system to remove some pollutants (e.g., toxic compounds), and then discharge the partially treated wastewater to the municipal sewer system.: 60 (most industries produce some wastewater. recent trends have been to minimize such production or to recycle treated wastewater within the production process. some industries have been successful at redesigning their manufacturing processes to reduce or eliminate pollutants. sources of industrial wastewater include battery manufacturing, chemical manufacturing, electric power plants, food industry, iron and steel industry, metal working, mines and quarries, nuclear industry, oil and gas extraction, petroleum refining and petrochemicals, pharmaceutical manufacturing, pulp and paper industry, smelters, textile mills, industrial oil contamination, water treatment and wood preserving). treatment processes include brine treatment, solids removal (e.g. chemical precipitation, filtration), oils and grease removal, removal of biodegradable organics, removal of other organics, removal of acids and alkalis, and removal of toxic materials. sewage sludge treatment this section is an excerpt from sewage sludge treatment. sludge treatment in anaerobic digesters at a sewage treatment plant in cottbus, germany sewage sludge treatment describes the processes used to manage and dispose of sewage sludge produced during sewage treatment. sludge treatment is focused on reducing sludge weight and volume to reduce transportation and disposal costs, and on reducing potential health risks of disposal options. water removal is the primary means of weight and volume reduction, while pathogen destruction is frequently accomplished through heating during thermophilic digestion, composting, or incineration. the choice of a sludge treatment method depends on the volume of sludge generated, and comparison of treatment costs required for available disposal options. air-drying and composting may be attractive to rural communities, while limited land availability may make aerobic digestion and mechanical dewatering preferable for cities, and economies of scale may encourage energy recovery alternatives in metropolitan areas. sludge is mostly water with some amounts of solid material removed from liquid sewage. primary sludge includes settleable solids removed during primary treatment in primary clarifiers. secondary sludge is sludge separated in secondary clarifiers that are used in secondary treatment bioreactors or processes using inorganic oxidizing agents. in intensive sewage treatment processes, the sludge produced needs to be removed from the liquid line on a continuous basis because the volumes of the tanks in the liquid line have insufficient volume to store sludge. this is done in order to keep the treatment processes compact and in balance (production of sludge approximately equal to the removal of sludge). the sludge removed from the liquid line goes to the sludge treatment line. aerobic processes (such as the activated sludge process) tend to produce more sludge compared with anaerobic processes. on the other hand, in extensive (natural) treatment processes, such as ponds and constructed wetlands, the produced sludge remains accumulated in the treatment units (liquid line) and is only removed after several years of operation. sludge treatment options depend on the amount of solids generated and other site-specific conditions. composting is most often applied to small-scale plants with aerobic digestion for mid-sized operations, and anaerobic digestion for the larger-scale operations. the sludge is sometimes passed through a so-called pre-thickener which de-waters the sludge. types of pre-thickeners include centrifugal sludge thickeners, rotary drum sludge thickeners and belt filter presses. dewatered sludge may be incinerated or transported offsite for disposal in a landfill or use as an agricultural soil amendment. energy may be recovered from sludge through methane gas production during anaerobic digestion or through incineration of dried sludge, but energy yield is often insufficient to evaporate sludge water content or to power blowers, pumps, or centrifuges required for dewatering. coarse primary solids and secondary sewage sludge may include toxic chemicals removed from liquid sewage by sorption onto solid particles in clarifier sludge. reducing sludge volume may increase the concentration of some of these toxic chemicals in the sludge. avoidance and reduction methods an important method of waste management is the prevention of waste material being created, also known as waste reduction. waste minimization is reducing the quantity of hazardous wastes achieved through a thorough application of innovative or alternative procedures. methods of avoidance include reuse of second-hand products, repairing broken items instead of buying new ones, designing products to be refillable or reusable (such as cotton instead of plastic shopping bags), encouraging consumers to avoid using disposable products (such as disposable cutlery), removing any food/liquid remains from cans and packaging, and designing products that use less material to achieve the same purpose (for example, lightweighting of beverage cans). international waste trade this section is an excerpt from global waste trade. the global waste trade is the international trade of waste between countries for further treatment, disposal, or recycling. toxic or hazardous wastes are often imported by developing countries from developed countries. the world bank report what a waste: a global review of solid waste management, describes the amount of solid waste produced in a given country. specifically, countries which produce more solid waste are more economically developed and more industrialized. the report explains that "generally, the higher the economic development and rate of urbanization, the greater the amount of solid waste produced." therefore, countries in the global north, which are more economically developed and urbanized, produce more solid waste than global south countries. current international trade flows of waste follow a pattern of