Tag: Combustion

Open Burning of Tyres: Impacts on Public Health

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Burning of tyres as a cheap source of energy is common in many developing countries, such as India.  While burning tyres does provide a cheap and efficient source of energy, the harmful effects of such burning far exceed the benefits.

Emissions from open tyre burning include “criteria” pollutants, such as particulates, carbon monoxide (CO), sulfur oxides (SOx), oxides of nitrogen (NOx), and volatile organic compounds (VOCs). They also include “non-criteria” hazardous air pollutants (HAPs), such as polynuclear aromatic hydrocarbons, dioxins, furans, hydrogen chloride, benzene, polychlorinated biphenyls (PCBs); and metals such as cadmium, nickel, zinc, mercury, chromium, and vanadium.

Both criteria and non-criteria pollutants can cause significant short and long term health effects.  Depending on the length and degree of exposure, these health effects could include irritation of the skin, eyes, and mucous membranes, respiratory effects, central nervous system depression, anxiety and cancer.  Dioxin is a highly toxic compound which may cause cancer and neurological damage, and disrupt reproductive systems, thyroid systems, respiratory systems etc.

Uncontrolled tyre burning has been proven to be 16 times more mutagenic, i.e capable of inducing genetic mutation, than traditional residential wood combustion in a fireplace, and 13,000 times more mutagenic than coal-fired utility emissions with good combustion efficiency and add-on controls.

Uncontrolled tyre burning is highly dangerous for public health and environment

Especially troubling is the exposure that children living within these communities are inadvertently being subjected to. Children, foetuses, nursing babies, elderly, asthmatics, and immune suppressed individuals are all much more vulnerable to the pollutants released burning tyres. Even a nursing woman can transfer the pollutions she inhales to a baby through the fat in her breast milk.  During breast-feeding, infants are exposed to higher concentrations of organic pollutants than at any subsequent time in their lives.

Saving money on fuel by burning tyres should not take precedence over public health. Unfortunately, in small villages and other underdeveloped areas where tyre burning kilns sustain much of the local economy, exposure to these toxins is inevitable with the current practices being employed. The need of the hour is to promote sustainable scrap tyre management systems such as pyrolysis and crumb rubber production.

For more information, please email Salman Zafar on salman@cleantechloops.com or salman@ecomena.org

Thermal Processing of Agricultural Wastes

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Agricultural wastes are highly important sources of biomass fuels for both the domestic and industrial sectors. Availability of primary residues for energy application is usually low since collection is difficult and they have other uses as fertilizer, animal feed etc. However secondary residues are usually available in relatively large quantities at the processing site and may be used as captive energy source for the same processing plant involving minimal transportation and handling cost.

Agricultural wastes encompasses all agricultural wastes such as straw, stem, stalk, leaves, husk, shell, peel, pulp, stubble, etc. which come from cereals (rice, wheat, maize or corn, sorghum, barley, millet), cotton, groundnut, jute, legumes (tomato, bean, soy) coffee, coconut, cacao, tea, fruits (banana, mango, coco, cashew) and palm oil.

A wide range of thermal technologies exists to convert the energy stored in agricultural wastes to more useful forms of energy. These technologies can be classified according to the principal energy carrier produced in the conversion process. The major methods of thermal conversion are combustion in excess air, gasification in reduced air, and pyrolysis in the absence of air.

Conventional combustion technologies raise steam through the combustion of biomass. This steam may then be expanded through a conventional turbo-alternator to produce electricity. Co-firing or co-combustion of agricultural wastes with coal and other fossil fuels can provide a short-term, low-risk, low-cost option for producing renewable energy while simultaneously reducing the use of fossil fuels. Co-firing has the major advantage of avoiding the construction of new, dedicated, biomass power plant.

Gasification of agricultural wastes takes place in a restricted supply of oxygen and occurs through initial devolatilization of the biomass, combustion of the volatile material and char, and further reduction to produce a fuel gas rich in carbon monoxide and hydrogen. This combustible gas has a lower calorific value than natural gas but can still be used as fuel for boilers, for engines, and potentially for combustion turbines after cleaning the gas stream of tars and particulates. Biomass power systems using gasification has followed two divergent pathways, which are a function of the scale of operations. At sizes much less than 1MW, the preferred technology combination today is a moving bed gasifier and ICE combination, while at scales much larger than 10 MW, the combination is of a fluidized bed gasifier and a gas turbine.

Pyrolysis enables agricultural residues to be converted to a combination of solid char, gas and a liquid bio-oil. Pyrolysis technologies are generally categorized as “fast” or “slow” according to the time taken for processing the feed into pyrolysis products. Bio-oil can act as a liquid fuel or as a feedstock for chemical production. A range of bio-oil production processes are under development, including fluid bed reactors, ablative pyrolysis, entrained flow reactors, rotating cone reactors, and vacuum pyrolysis.

For more information, please email Salman Zafar on salman@cleantechloops.com or salman@ecomena.org

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