Bringing Sustainability in Coal Mining Operations is need-of-the-hour

Bringing Sustainability in Coal Mining Operations is need-of-the-hour:

A. Introduction - The importance of sustainable development principles has been increasing within the mining sector over the past two decades. Early work focused mainly on mining metals and commodities other than coal and energy fuels. Because sustainability, however, is an important consideration for all human endeavors now, the coal industry has become active in sustainability efforts. A number of global coal mining companies have embraced sustainability as a key aspect of corporate philosophy.

Continued production of minerals and fossil energy fuels may not fit into commonly understood definitions of sustainability. Mineral and energy extraction and reclamation operations do, however, contribute significantly to sustainability through the benefits they provide to society, when they are conducted in a manner that supports sustainable economies, social structures and environments throughout all phases of mining, including closure. Significant progress can also be made through the inclusion of sustainability concepts in the original design of the operation, as well as in ongoing operations. Innovative engineering, mining and reclamation operations can be optimized through consideration of environmental and economic sustainability goals, side-by-side with traditional technical mining engineering considerations.

B. Abate hazards in coal mining areas by promoting reclamation - Coal mining operations can result in disturbances to the land surface that burden or adversely affect commerce and the public welfare by destroying or diminishing the utility of land for commercial, industrial, residential, recreational, agricultural, and forestry purposes, by causing erosion and landslides, by contributing to floods, by polluting the water, by destroying fish and wildlife habitats, by impairing natural beauty, by damaging the property of citizens, by creating hazards dangerous to life and property, by degrading the quality of life in local communities, and by counteracting governmental programs and efforts to conserve soil, water, and other natural resources. The predicted expansion of coal mining to meet the world’s growing energy needs makes it even more urgent to establish appropriate standards to minimize additional damage to the environment and to productivity of the soil and to protect the health and safety of the public. At the same time it is important to develop programs with associated funding mechanisms to restore the utility of land damaged by past mining.

For example, China has reported it has about 13.3 million acres “derelict” lands of which four million of those acres were caused by past coal mining. This adversely impacts nearly 1/10th of China’s total agricultural acreage. Although mining reclamation began in the early 1960s in China, it has not been consistently implemented and about 40,000 new hectares are presently being disturbed by coal mining activities each year. In India more than 80,000 people have to be shifted to safer places as they are residing in areas which are now considered unstable due to past unscientific mining and the coal mine fires endangering such areas. Large tracts of mined out/subsided areas of the past also require reclamation apart from dealing with fires in some of the old coalfields.

i. Goals and Objectives towards better Environmental Management - Mining becomes a temporary land use through programs of environmental management and land reclamation.
* Establish a nationwide program to protect society and the environment from the adverse effects of coal mining operations.
* Assure that the coal supply essential for any nation’s energy requirements and to its economic and social well-being is provided and strike a balance between protection of the environment and agricultural productivity and the country’s need for coal as an essential source of energy.
* Promote reclamation of mined areas left without adequate reclamation and which continue, in their un-reclaimed condition, to substantially degrade the quality of the environment, prevent damage of the beneficial use of land or water resources, or endanger the health or safety of the public.

ii. Management of topsoil for geo-environmental reclamation - Topsoil is an essential component for land reclamation in mining areas. It is seriously damaged if it is not mined out separately without being contaminated, eroded and protected. Systematic handling and storage practices can protect topsoil while in storage and after it has been redistributed onto the re-graded area. Removed topsoil should be reclaimed technically and its shelf-life period should be ascertained. Soil dumps of different age classes in the area were identified and analyzed critically to evaluate the deterioration of soil quality with respect to time, and compared with those of unmined areas. Changes in soil quality showed a continuous decrease every year and ultimately became biologically sterile. Biological reclamation is essential if the soil is to be stored beyond the shelf-life period.

C. Current Issues -
i. The future of coal extraction - It is widely recognized that coal is and will continue to be a crucial element in a modern, balanced energy portfolio, providing a bridge to the future as an important low cost and secure energy solution to sustainability challenges. Energy demand everywhere is expected to grow substantially. In emerging economy, most of developed and developing nations, almost every energy source is expected to grow, with coal, petroleum and natural gas dominating the energy mix. In these nations, electricity generation relies heavily on fossil fuels; coal is the dominant component which is expected to increase. As per estimation, overall, world use of coal is projected to grow by 44 % by 2025.

In addition, coal and crude oil can both be used as feed stock for conversion into liquid fuels and the choice depends on the price of feed stock. Energy economists maintain that coal liquefaction is viable for crude oil prices greater than $40 per barrel. Experts predict that Coal-to-Liquids (CTL) will be the largest contributor of “un-conventional” fuels.

ii. Corporate policies - The global coal and energy production industries have recently begun a major effort to identify and accelerate the deployment and further development of innovative, advanced, efficient, cleaner coal technologies. A number of coal producers in developed nations are also involved in sustainable development activities, including economic sup-port of communities and regions and environ-mental protection and restoration. These companies have corporate sustainable development policies in place that provide guidance for operations and some report annually on their contributions to sustainability. Challenges facing Mining industry for sustainable development are:
* Ensuring the long-term viability of the minerals industry,
* Control, use, and management of land,
* Using minerals to assist with economic development,
* Making a positive impact on local communities,
* Managing the environmental impact of mines,
* Integrating the approach to using minerals so as to reduce waste and inefficiency,
* Giving stakeholders access to information to build trust and cooperation,
* Managing the relationship between large companies and small-scale mining,
* Sector governance: Clearly defining the roles, responsibilities, and instruments for change expected of all stakeholders.

iii. Traditional mine design considerations - Most mine designs are based on traditional mining engineering factors, such as the quality of the commodity being mined, the geology, topography, hydrology, land ownership, geography, infrastructure, etc. Currently, environmental compliance and sustainability are considered in mine design and operation as a modifying factor to those designs.

iv. Optimization - A cursory review of the available literature on engineering optimization does not reveal any focus on mine design, environmental protection associated with mines or sustainability. Mathematical multi-criteria optimization approaches, however, have previously been used in resource management. Unfortunately, there is a paucity of literature about the practice.

As with any optimization problem, mine design optimization would need to consider all constraints, system parameters and characteristics and desired outcomes in order to build a useful and reliable model. Since optimization of mine design, and in particular coal mine design, to address sustainability along with other parameters has not been widely practiced, identifying the appropriate parameters for measurement and the mathematical or logical relation-ships between these parameters is not a trivial task.

D. Suggested approach - In order to optimize the design of coal mining and reclamation operations, traditional mining engineering considerations and environmental and sustainability goals must be accounted for simultaneously. It is essential to identify all of the parameters, relationships, constraints and desired outcomes related to the widely varying factors that contribute to mine design, as well as the additional factors that should be considered as a part of a new, sustainable design approach.

i. Parameters - For successful optimization of mine design, required parameters must be identified and measured as part of mine design and planning. To build an accurate model of those operations, data must be collected on ongoing operations. This data accounts for the modification of long-term designs as a part of permitting and the acquisition of information during mine operation. The design and operation of current coal mining properties should be evaluated by looking both at permitting documents and additional data which obtained from mining companies and other public and private sources. This data reflects the mining engineering, geologic, economic and other considerations currently integrated into the design and planning process.
It can then be determined how legal, policy, environmental protection and sustainability should be incorporated in mine design. Whenever possible, the effect of environmental and post-mining land use considerations on mine design and operation needs to be quantified in economic terms, so as to be on par with other engineering considerations.

ii. Relationships- Once sufficient data is collected, it will be necessary to determine if and how these parameters influence one another and the desired outcomes for the specific mining operation. These relationships may be apparent based on scientific, engineering or other considerations, or may require detailed statistical analysis in order to determine them. It may not be possible to state the precise interrelationships between numerous parameters, particularly given the lack of complete independence of many of them. It may be possible, however, to derive qualitative rather than quantitative models for those relationships.

iii. Desired Outcomes- In most cases, the ultimate desired outcomes are the profitability and long-term stability of the site. These are driven by corporate realities as well as the concern for long term liability. Coal mining is, after all, a business focused on profitability and long-term economic benefit for the shareholders or other owners. Additional out-comes for community economic benefits, enhanced environmental quality, and corporate image are also significant for many mining companies and in many locations.

The optimization approach must address the relative importance of these outcomes in order to weight them in the development of optimized models. For example, in an area with low avail-ability of safe drinking water, protection of hydrologic resources may prove to be of primary significance, and thus of higher weight in the models, since it will greatly impact the feasibility and long-term profitability of the operation as well as the post-mining health of the community.
The factors related to sustainability in the minerals industry, identified above, can serve as the basis for desired sustainability outcomes. The first factor, industry viability, is ad-dressed primarily through consideration of the economic profitability of an operation. Giving stakeholders access to information; defining the roles, responsibilities and instruments for change; managing the relationship between companies of different scales; benefiting local communities; and, promoting efficient use of minerals, are social factors which may be more difficult to measure and may not directly impact the design and operation of a specific mining property.

However, managing the environmental impact of mines and the control, use and management of lands are both more easily quantified and related to accepted practices and legal frameworks. Future work should focus on the parameters related to these goals. Many of these parameters may already be routinely measured as a part of environmental or other compliance mechanisms.

E. Nation’s Mission To Protect Environment by Enacting Laws– It is of national interest, Governments of every country should be dedicated to protecting the environment of the nation. In other words, to protecting the health and safety of the miner and to protecting the life, health, and property of citizens who are affected by mining or mining activities through the enforcement of suitable state mining and reclamation laws. The laws should ensure that the environment is protected during coal mine operations, and that lands mined for coal are adequately reclaimed after mining is completed. It allows alternative or experimental reclamation practices to encourage technological advances in mine reclamation and innovative post-mining land uses.

i. Environmental Impact Assessment (EIA) - Some form of Environmental Impact Assessment (EIA), and accompanying procedures for information disclosure, public participation and judicial or administrative review, have become widely adopted as part of the project and/or policy review process in most countries.

The US government introduced EIAs as an “action-forcing mechanism” to identify, assess, and mitigate environmental and human impacts of government actions in the United States. Since then, EIAs have spread to well over 100 countries, and have been enshrine in Principle 17 of the Rio Declaration, gaining worldwide legitimacy as a critical element of environmental management. EIAs have grown in both strength and scope and are now one of the premiere tools in environmental management in most countries. EIAs should address some of the basic factors listed below:

* Meteorology and air quality. Ambient levels of pollutants such as sulphur dioxide (SO2), oxides of nitrogen, carbon monoxide (CO), suspended particulate matters, should be determined. Additional contribution of pollutants at the locations are required to be predicted after taking into account the emission rates of the pollutants from the stacks of the proposed plant, under different meteorological conditions prevailing in the area.
* Hydrology and water quality
* Site and its surroundings
* Occupational safety and health
* Details of the treatment and disposal of effluents (liquid, air and solid) and the methods of alternative uses.
* Transportation of raw material and details of material and details of material handling.
* Impact on sensitive targets.
* Control equipment and measures proposed to be adopted including post-mining reclamation.

Preparation of environmental management plan is required for formulation, implementation and monitoring and of environmental protection measures during and after commissioning of projects. Planning for closure and reclamation should begin during the earliest stages of project development, before operations start at a new site, and continues throughout the mine life. Goal is to minimize the disturbance of land in all phases of the mine life and to provide a post-closure land use which is compatible with traditional uses or provides sustainable advantages to the local communities.

ii. Coal Mining Permit Process - Before commencement of coal mining operations, a mining and reclamation permit must be obtained from the Govt. departments. A coal permit should be issued when the mine operator submits an acceptable application and posts adequate bond to cover reclamation costs, should it be necessary for a third party to complete the reclamation process. The operator's permit application must include the requirements for legal and financial compliance, the safeguard of environmental resources, and an operation and reclamation plan. Before opening the site, the employees of the coal mining operation must be trained and certified in accordance with state and federal safety regulations. Mining practices, reclamation, and health and safety procedures are monitored on a regular basis by the Departments' field inspectors.

iii. Following goals, in general, should be accomplished through Permit Process -
* Reviewing permit, revision, field amendments applications for completeness and technical adequacy.
* Ensuring that adequate bond to complete reclamation is posted by the permittee.
* Conducting complete and partial inspections on coal permits as required by state and federal rules and regulations and the specific requirements of the approved permit such that non-compliance items are identified and appropriate abatement measures implemented.
* Conducting annual and mid-term permit reviews in compliance with statutes and regulations.
* Conducting bond release inspections in compliance with statutes and regulations.
* Conducting citizen complaint inspections in compliance with statutes and regulations.
* Gathering evidence and testifying at hearings as required by statutes and regulations.
* Conducting Student Outreach Programs at local area schools to provide students and teachers with a better understanding of the mining process.
* Receiving on-going training and information concerning current technical advances and trends in mining, safety, and reclamation.

F. Summary and Conclusion - It is widely recognized that coal is and will continue to be a crucial element in a modern, balanced energy portfolio, providing a bridge to the future as an important low cost and secure energy solution to sustainability challenges. In response, the global coal and energy production industries have begun a major effort to identify and accelerate the deployment and further development of innovative, advanced, efficient, cleaner coal technologies. A number of coal producers are also involved in sustainable development activities, including economic support of communities and regions, environmental restoration and social well-being.

The designer of coal mining operations needs to simultaneously consider legal, environmental and sustainability goals along with traditional mining engineering parameters as an integral part of the design process. The role of coal in the global energy supply mix makes this of primary importance. There is a need for research into the parameters for mining design that allow the building of models for optimization, the relationships between those parameters, and the desired outcomes that the system is being optimized to produce. In addition to quantifying the economic viability of the operation, a number of sustainability goals should be built into the model and the relative importance of those goals determined.

References:
1. Energy Information Administration (EIA), 2007. Annual Energy Outlook 2007 with Projections to 2030. Washington: US Department of Energy, Energy Information Administration. http://www.eia.doe.gov/oiaf/aeo/ in-dex.html accessed March 30, 2007.
2. Global Reporting Initiative (GRI), 2007. G3 Sustainability Reporting Guidelines. www.globalreporting.org accessed March 30, 2007.
3. Gibson, R.B., S. Hassan, S. Holtz, J. Tansey and G. Whitelaw, 2005. Sustainability Assessment. London: Earthscan Publications.
4. International Energy Agency (IEA), 2004. World Energy Outlook 2004, Paris: Organization for Economic Co-operation and Development/International Energy Agency.
5. International Institute for Environment and Development (IIED) and World Business Council for Sustainable Development (WBCSD), 2002. Breaking new ground: The report of the Mining, Minerals, and Sustainable Development Project. London: Earthscan Publica-tions.
6. Stadler, W. (ed.), 1988. Multicriteria optimization in engineering and in the sciences. New York: Plenum Press.
7. Waddell, S. and B. Pruitt, 2005. The Role of Coal in Cli-mate Change: A Dialogic Change Process Analysis. Presented at the Generative Dialogue Project Launch Meeting, New York, NY, October 6-8, 2005.
8. World Coal Institute (WCI), 2007. Environment and Society. http://www.worldcoal.org/environment_&_so-ciety.asp
9. http://sharynmunro.com/?p=134
10. http://www.sustainableenergyresources.co.uk/fossil_fuels/fossil_fuels.asp

Coal is Essential for Energy Security for many – Strategies to enlarge supply base and reduce environmental impacts are the prerequisites:

Coal is Essential for Energy Security for many – Strategies to enlarge supply base and reduce environmental impacts are the prerequisites:

A. More and more frequent environmental problems and disasters – floods, forest fires, tornados, air pollution in big cities – cause growing concerns everywhere. Energy harvesting, conversion, production and use contribute to these environmental burdens.

Hence, improving the environmental performance of the energy sector is of paramount importance. Thus, wider application of cleaner fuels and conversion technologies is a key element in the strategy to improve the environmental performance of the energy sector. Further, the lower price of coal as compare to petroleum based fuels; the interest in coal is renewed because of the more even geopolitical distribution of coal reserves and of larger supply bases of coal allover the world.

In fact, the environmental concerns about coal are not associated with coal itself, but with its utilization in different stages of the energy chain. Novel and more environmentally friendly technologies for coal utilization, commonly known as “Clean Coal Technologies” (CCT), are believed to be able to bring coal back into the picture. Hence, CCT recently enjoy a growing interest almost all parts of the world. At present, this interest mostly focuses on cleaner coal conversion through increased efficiency and CO2 capture technologies, for which large R&D efforts are ongoing worldwide.

B. Market implementation of CCT is expected to cause an increase in coal use. Coal demand could also rise significantly because the recent sharp increase in oil prices has a lower impact on coal than on gas prices. This is explained by the more favorable geopolitical distribution of coal reserves compared to that of gas. As a result, coal has become cheaper in relative terms than oil and gas. All in all, in a scenario of soaring oil & gas prices, coal is predicted to be the energy source with the fastest growing demand. The expected increase in coal demand for power generation raises the question of its secure availability in the future. Thus, enlargement of the coal supply base is essential throughout the world, with adoption of cleaner technology.

C. The enlargement of the coal supply base can take place in four main directions:

(a) More powerful mapping techniques for coal reserves - Modern geophysics and seismic techniques, improve mine planning and exploitation by reducing geological uncertainties and increasing extraction efficiencies. At the same time, they can reduce environmental externalities and energy use for coal extraction.

(b) Improvement of existing under-ground mining technologies - Underground (deep) coal mining accounts for about 60% of world coal production. Current best coal recovery rates for underground mining are 50-60% for the “room-and-pillar” technology and about 75% for “longwall” mining. The implementation of modern automated and computerized mining technologies can increase these recovery rates.

(c) Research and development for underground coal gasification - Underground gasification of coal deposits which are not technically or economically exploitable (anymore) with conventional mining technologies, can add enormous coal supply potential in Europe and worldwide. At present underground coal gasification is at an experimental stage. Significant further efforts are necessary to make it technically and economically viable. In many of the countries like India etc., commercialization of underground gasification technologies may reduce the energy import dependence and enhance energy security scenario, apart from creating new employment.

(d) Utilization of coalmine methane (CMM) gas - Methane gas, released from coalmines, has always raised serious safety and environmental concerns. Methane is highly explosive when accumulated in confined areas. It is also a powerful greenhouse gas with 20- times stronger global warming potential than carbon dioxide. On the other hand, CMM, which consists mainly of natural gas, is a suitable clean fuel. The capture and useful utilization of CMM can bring important synergy benefits in terms of enhanced security of supply and better environmental and safety performance of coal mining.

D. Therefore, for realizing the full potential of CCT, coal is sufficiently

(a) Abundant… only if we keep working on the enhancement of coal reserves,

(b) Cheap… as long as the supply continues to match the demand,

(c) Reliable… as long as the supplies are diversified.

To reach market maturity, clean coal technologies, covering extraction, preparation and conversion, need a long term vision and investment security. In the present pre-commercial stage they need firm political commitment and further R&D support.

Coke making process and its environmental impacts:

Coke making process and its environmental impacts:

Coke is a solid carbon fuel and carbon source used to melt and reduce iron ore. Coke and coke by-products, including coke oven gas, are produced by the pyrolysis (heating in the absence of air) of suitable grades of coal. The process also includes the processing of coke oven gas to remove tar, ammonia (usually recovered as ammonium sulfate), phenol, naphthalene, light oil, and sulfur before the gas is used as fuel for heating the ovens.

A. Coke making process: In the coke-making process, bituminous coal is fed (usually after processing operations to control the size and quality of the feed) into a series of ovens, which are sealed and heated at high temperatures in the absence of oxygen, typically in cycles lasting 14 to 36 hours. Volatile compounds that are driven off the coal are collected and processed to recover combustible gases and other by-products. The solid carbon remaining in the oven is coke. It is taken to the quench tower, where it is cooled with a water spray or by circulating an inert gas (nitrogen), a process known as dry quenching. The coke is screened and sent to a blast furnace or to storage. Coke oven gas is cooled, and by-products are recovered. Flushing liquor, formed from the cooling of coke oven gas, and liquor from primary coolers contain tar and are sent to a tar decanter. An electrostatic precipitator is used to remove more tar from coke oven gas. The tar is then sent to storage. Ammonia liquor is also separated from the tar decanter and sent to wastewater treatment after ammonia recovery. Coke oven gas is further cooled in a final cooler. Naphthalene is removed in the separator on the final cooler. Light oil is then removed from the coke oven gas and is fractionated to recover benzene, toluene, and xylene. During the coke quenching, handling, and screening operation, coke breeze is produced. It is either reused on site (e.g., in the sinter plant) or sold off site as a by-product.

B. Pollution during coke making process:

The coke oven is a major source of fugitive air emissions. The coking process emits particulate matter (PM); volatile organic compounds (VOCs); polynuclear aromatic hydrocarbons (PAHs); methane, at approximately 100 grams per metric ton (g/t) of coke; ammonia; carbon monoxide; hydrogen sulfide (50–80 g/t of coke from pushing operations); hydrogen cyanide; and sulfur oxides, SOx (releasing 30% of sulfur in the feed). Significant amount of VOCs may also be released in by- product recovery operations. For every ton of coke produced, approximately 0.7 to 7.4 kilograms (kg) of PM, 2.9 kg of SOx (ranging from 0.2 to 6.5 kg), 1.4 kg of nitrogen oxides (NOx), 0.1 kg of ammonia, and 3 kg of VOCs (including 2 kg of benzene) may be released into the atmosphere if there is no vapor recovery system. Coal-handling operations may account for about 10% of the particulate load. Coal charging, coke pushing, and quenching are major sources of dust emissions.

Wastewater is generated at an average rate ranging from 0.3 to 4 cubic meters (m3) per ton of coke processed. Major wastewater streams are generated from the cooling of the coke oven gas and the processing of ammonia, tar, naphthalene, phenol, and light oil. Process wastewater may contain 10 milligrams per liter (mg/l) of benzene, 1,000 mg/l of biochemical oxygen demand (BOD) (4 kg/t of coke), 1,500–6,000 mg/l of chemical oxygen demand (COD), 200 mg/l of total suspended solids, and 150–2,000 mg/l of phenols (0.3–12 kg/t of coke). Wastewaters also contain PAHs at significant concentrations (up to 30 mg/ l), ammonia (0.1–2 kg nitrogen/t of coke), and cyanides (0.1–0.6 kg/t of coke). Coke production facilities generate process solid wastes other than coke breeze (which averages 1 kg/t of product). Most of the solid wastes contain hazardous components such as benzene and PAHs. Waste streams of concern include residues from coal tar recovery (typically 0.1 kg/t of coke), the tar decanter (0.2 kg/t of coke), tar storage (0.4 kg/t of coke), light oil processing (0.2 kg/t of coke), wastewater treatment (0.1 kg/t of coke), naphthalene collection and recovery (0.02 kg/t of coke), tar distillation (0.01 kg/t of coke), and sludges from biological treatment of wastewaters.

C. Pollution Prevention and Control: Pollution prevention in coke making is focused on reducing coke oven emissions and developing coke-less iron & steel-making techniques. The following pollution prevention and control measures should be considered.

1. General -

(a) Use cokeless iron- and steel-making processes, (b) such as the direct reduction process, to eliminate the need to manufacture coke. (c) Use beneficiation (preferably at the coal mine) and blending processes that improve the quality of coal feed to produce coke of desired quality and reduce emissions of sulfur oxides and other pollutants. (d) Use enclosed conveyors and sieves for coal and coke handling. Use sprinklers and plastic emulsions to suppress dust formation. Provide windbreaks where feasible. Store materials in bunkers or warehouses. Reduce drop distances. (e) Use and preheat high-grade coal to reduce coking time, increase throughput, reduce fuel consumption, and minimize thermal shock to refractory bricks.

2. Coke Oven Emissions –

(a) Charging: dust particles from coal charging should be evacuated by the use of jumper-pipe systems and steam injection into the ascension pipe or controlled by fabric filters.

(b) Coking: use large ovens to increase batch size and reduce the number of chargings and pushings, thereby reducing the associated emissions. Reduce fluctuations in coking conditions, including temperature. Clean and seal coke oven openings to minimize emissions. Use mechanical cleaning devices (preferably automatic) for cleaning doors, door frames, and hole lids. Seal lids, using a slurry. Use low-leakage door construction, preferably with gas sealing.

(c) Pushing: emissions from coke pushing can be reduced by maintaining a sufficient coking time, thus avoiding “green push.” Use sheds and enclosed cars, or consider use of traveling hoods. The gases released should be removed and passed through fabric filters.

(d) Quenching: where feasible, use dry instead of wet quenching. Filter all gases extracted from the dry quenching unit. If wet quenching, is used, provide interceptors (baffles) to remove coarse dust. When wastewater is used for quenching, the process transfers pollutants from the wastewater to the air, requiring subsequent removal. Reuse quench water.

(e) Conveying and sieving: enclose potential dust sources, and filter evacuated gases.

3. By-Product Recovery –

(a) Use vapor recovery systems to prevent air emissions from light oil processing, tar processing naphthalene processing, and phenol and ammonia recovery processes.

(b) Segregate process water from cooling water.

(c) Reduce fixed ammonia content in ammonia liquor by using caustic soda and steam stripping.

(d) Recycle all process solid wastes, including tar decanter sludge, to the coke oven.

(e) Recover sulfur from coke oven gas. Recycle Claus tail gas into the coke oven gas system.

Carbon emission from bio-fuels:

Carbon emission from bio-fuels:

Bio-fuels are the fuels of solid, liquid or gaseous in nature, which has been derived from bio-mass – recently living organisms or their metabolic byproducts. Thus, it could be oils from plants, manure from cows, wood from trees etc. For example, bio-gas (i.e., gas produced by the biological breakdown of organic matter in the absence of oxygen); bio-ethanol; bio-diesel; straight vegetable oil etc., are the bio-fuels. It is a renewable energy source, mostly have agricultural based, unlike other natural resources such as petroleum, coal and nuclear fuels.

It has been seen that certain social and environmental benefits bio-fuels has as compare to use of fossil fuels, such as reduction of greenhouse gas emission, increased national energy security, increased rural earnings and development and above all, reduction of use of fossil fuel.

Bio-fuels and other forms of renewable energy are thought to be ‘carbon neutral’ or ‘carbon negative’. Carbon neutral or carbon negative is the difference of quantum of carbon produced and emitted to the atmosphere when these are used as fuels and the quantum of carbon absorbed in the process of their growth. If both are same, is called carbon neutral or if quantum of carbon absorbed through photo-synthesis is more than the emission is called carbon negative. Both the cases are advantageous towards environment point of view and reduction of global warming.

Strictly speaking, bio-fuels are neither carbon neutral nor carbon negative. This is because extra energy is required to grow crops and process them into fuel. This extra energy releases extra carbon to atmosphere as emission. For example, plants require fertilizer to grow, requires energy for transportation and processing; this extra energy releases carbon to the atmosphere as emission. Therefore, this emission aspect is to be debated, whether we are really gaining in respect of carbon emission, by using bio-fuel. However, the arid lands can be better utilized if people shift towards bio-fuels; so the rural earnings. The poorly irrigated land mass also can be taken up for cultivation.