Best Practices for Controlled Burns
- • Determine the time for the controlled burn of a given area based on what vegetative response is desired.
- • Minimize smoke production by burning based on prevailing weather conditions, existing air quality, forecast air quality for the immediate area and areas downwind of the controlled fire, and the time of day.
- • Do not start fires early in the morning or late in the evening.
- • Take into account the amount of surface winds and transport wind (the rate at which the pollutants will be moved to other areas).
- • Take into account the mixing height/dispersion potential for vertical mixing above the fire. Understand how relative humidity, fuel moisture, and air temperature can affect controlled burns and utilize this information to reduce potential for pollution.
- • Understand ignition and burn techniques and the type of prescribed fire for safety purposes and pollution control.
- • Contact appropriate fire authorities and advise them of the scheduled controlled burns.
- 6. Erosion
Erosion is the removal of soil and rock fragments by wind, water, snowmelt, flooding, rain, organisms, and gravity. It is also caused by fires, construction, agriculture, tree removal, drought, etc. (See the section on “Erosion” in Chapter 14)
7. External Combustion Sources
External combustion sources include: electric power plants using steam; industrial, commercial, and institutional boilers; process heaters; commercial and industrial solid waste incinerators; and combustion systems for commercial and domestic use. These systems use fossil fuel (coal, oil, both distillate oil and residual oil, and natural gas as their major source of fuel). Solid waste incinerators may use biomass, which can be wood and wood waste, municipal waste, corncobs, oats, etc., as their source of fuel.
The energy produced in external combustion units is used for generating electric power, process heating and space heating, and along with the production of energy are the unwanted pollutants including sulfur oxides, nitrogen oxides, particulates, carbon dioxide, mercury, hydrogen chloride, carbon monoxide, lead, cadmium, VOCs, arsenic, etc. a. Electric Power Plants (See endnotes 29, 51)
Electric power plants primarily use fossil fuels which are burned in a boiler to produce steam to turn the blades of the steam turbine that turns the shaft of the generator to produce electricity. In a nuclear power plant, the heat produced in the reactor is used to make steam. In a gas turbine, the combustion of the natural gas and distillate oil under high pressure produces hot gases, which spins the generator to produce electricity. In a combined cycle turbine, hot gases which have been used to spin one turbine generator go to a waste heat recovery system boiler where the water is heated again to produce steam and produces electricity. All of this uses one input of fuel to gain greater efficiency of production of electricity. In a hydroelectric generating system, the falling water or natural river current drives the turbine blades to cause the generator to produce electricity. Geothermal power uses the heat energy buried in the earth. Solar power uses the energy from the light and heat of the sun with photovoltaic conversion to generate electricity. The energy in wind power is converted to electricity.
Electric power plants, because of the use of fossil fuels as a source of energy, are a major contributor to criteria air pollutants, acid rain, greenhouse gases, and toxic air pollutants in North America, as well as throughout the world, especially in newly industrialized countries. In the United States, the Government Accountability Office (GAO), in 2010, conducted a study of 3443 electrical generating units, of which 1485 were older units (93% of the older units used coal) commissioned prior to 1978, and 1956 units were newer and more efficient. The older units using fossil fuel including coal produced 45% of the electricity used in the United States, but produced 75% of the sulfur dioxide emissions, 64% of the nitrogen oxides emissions, and 54% of the carbon dioxide emissions. For each unit of electricity produced by the older units, they emitted about 3.6 times as much sulfur dioxide, 2.1 times as much nitrogen oxides, and 1.3 times as much carbon dioxide as the newer units. This resulted in 90 times as much sulfur dioxide being released, twice as much carbon dioxide being released, and five times as much nitrogen oxides being released. (See endnote 11.)
Oil, used as a fuel, produces nitrogen oxides, sulfur dioxide, carbon dioxide, methane, and mercury compounds. The sulfur dioxide and mercury compounds vary widely with the sulfur and mercury content of the oil that is burned.
Natural gas, used as a fuel, produces nitrogen oxides, carbon dioxide, and methane (which is a natural component of the gas) in lesser amounts than coal or oil, but still in large enough quantities to pollute the air. Levels of sulfur dioxide and mercury are negligible.
Municipal solid waste has been used as a source of energy to produce electricity. This is still controversial because the burning of the waste produces nitrogen oxides, sulfur dioxide, and small amounts of toxic pollutants such as mercury and dioxins.
Landfill gas has been used as a source of energy to produce electricity. The burning of the landfill gas produces nitrogen oxides as well as small amounts of toxic materials depending on the waste that is burnt.
About 45% of the hazardous air pollutants identified by the EPA are found in coal, and approximately 40% of all hazardous air pollutants emitted from point sources come from coal usage. Coal-fired power plants are major sources of particulate matter, mercury, arsenic, etc. Noting the problems in the United States from coal-generated electric power, it is easy to understand the serious problems of newly industrialized societies, especially in China and India.
The Commission for Environmental Cooperation Council made up of cabinet level environmental health administrators from Canada, Mexico, and the United States issued a report in 2004 saying that electric power plants were the number one source of toxic air pollution in North America. They stated that 46 of the top 50 air polluters in North America were power plants. Hydrochloric acid and sulfuric acid were the most commonly released chemicals. (See endnote 12.)
b. Industrial, Commercial, and Institutional Boilers
Boilers are combustion units used to produce hot water or steam. The steam can run a variety of industrial processes and machinery, and produce heat or electricity. The boilers not only emit the pollutants from the fossil fuels, if they use them, but also from a variety of industrial processes. These may include nitrogen oxides, sulfur dioxide, particle pollution, carbon monoxide, formaldehyde, polycyclic aromatic hydrocarbons (PAHs), lead, hydrogen chloride, cadmium, mercury, dioxins, furans, greenhouse gases, etc.
There are approximately 1.5 million boilers in the United States. New emission standards issued in 2013 by the US EPA will apply to about 13% of all the boilers. These standards when enforced will lower emissions of hazardous air pollutants. These boilers in the United States are found in refineries, chemical plants, and other industrial facilities. These boilers are of greatest concern, contributing to the amount of hazardous air pollutants found in the air.
c. Process Heating Systems
In a fuel-based process heating system, the heat is generated by the combustion of solid, liquid, or gaseous fuel and is transferred either directly or indirectly to the material being processed. The system needs to be energy efficient and product friendly. The systems may produce the same types of pollutants as in boilers as well as additional pollutants based on the type of industry involved. (See endnote 52.)
d. Municipal, Industrial, Commercial, Hospital Solid, and Hazardous Waste Incinerators (See Chapter 12, “Solid Waste, Hazardous Materials, and Hazardous Waste Management”)
Best Practices for External Combustion Sources (See endnotes 53, 54, 55, 56)
- • Wash the coal to remove impurities including sulfur compounds or free sulfur, and hazardous air pollutants which are not bound to the coal carbon matrix, before using the coal as a fuel source for power plants.
- • Treat flue gases to remove sulfur dioxide, nitrogen oxides, and mercury.
- • Trap and then separate carbon dioxide from flue gases, compress the carbon dioxide usually in pipelines, and either inject deep underground for storage purposes or utilize a portion of the chemical in other processes or products.
- • Use natural gas where feasible as the source of fuel for power plants since the byproducts of nitrogen oxides and carbon dioxide are lower than in other fossil fuels.
- • Burn the natural gas fully and efficiently to prevent methane from entering the atmosphere.
- • Evaluate the storage and use of fuel oil to prevent leaks, spillage, and other means of evaporation of the fuel into the atmosphere. Take necessary corrective action.
- • Sample and evaluate the composition of flue gases to make sure that they meet the specifications and regulations of the US EPA.
- • Use the desulfurization techniques including dry scrubbing and sorbent injection systems prior to the burning of coal.
- • Use denitrification techniques including selective catalytic reduction and/or selective non-catalytic reduction.
- • Use particulate collection techniques including electrostatic precipitators, fabric filters/ baghouses, and mechanical dust collectors.
- • Contain ash and fly ash to keep it from contaminating the air, land, and water.
- • Use condensing heat exchanger systems, where the latent heat in the flue gas is returned to the system, to reduce the emissions of hazardous air pollutants.
- • Use activated carbon filters to collect hazardous air pollutants, especially mercury.
- • Inject activated carbon powder onto fabric filter systems to reduce mercury.
- • Use combined heat and power systems (cogeneration) where feasible in manufacturing plants, hospitals, colleges, and other large buildings. This is a much more efficient use of fuel, while producing electricity and utilizing the waste heat for either space heating or for process energy.
- • Where coal is the fuel of choice, use a pulverized coal boiler where the burning is much more efficient than in the Stoker-type coal boiler and therefore less contaminants enter the air while more energy is being produced.
- • Install emissions control systems on existing boilers where needed.
- 8. Evaporative Sources
These are volatile liquids that are not enclosed in a tank or other container and evaporate or release vapors to the air. They are typically liquids such as paints, solvents, pesticides, hair sprays, aerosol sprays, gasoline, etc. Evaporative sources are found in many of the major sources of air pollution and area sources of air pollution. (See individual sources of interest for Best Practices.)
Smoke from wildfires contains gases and fine particles from the burning of trees, grasses, and bushes. These fires also burn houses, businesses, and potentially industries. The contaminants include the criteria pollutants, hazardous air pollutants, and greenhouse gases. When houses and businesses burn, pollutants are created which are similar to those that are found in incinerators that do not have air pollution controls. These hazardous air pollutants include PAHs, dioxins; furans; hydrochloric acid; formaldehyde; heavy metals including lead, mercury, and arsenic; styrene from foam cups, meat trays, and egg containers; household chemicals including cleaning materials, pesticides, and fertilizers; etc.
The smoke can have a profound effect on an individual’s health. It causes shortness of breath, chest pain, rapid heartbeat, fatigue, headaches, and the inability to breathe normally. People at greatest risk are the elderly, children, those with asthma, those with COPD, heart patients, etc. The smoke may also be a precursor to many diseases in the future.
Some people believe if they have a respirator or a mask that the smoke will not harm them. This may not be correct. The effectiveness of the respirator for the given problem depends on whether it will filter out very small particles, the type of chemical cartridge that is used, the fit of the mask on the individual, the amount of filtering capacity, etc.
Best Practices for Fires
- • Follow the orders for evacuation issued by appropriate authorities.
- • If you are elderly, very young, have asthma, or have other chronic diseases or allergies, leave the immediate area of the fires and go downwind from the fires as quickly as possible.
- • Listen to local air quality reports and public health messages concerning your safety and act on them immediately.
- • Stay indoors and make sure that you have clean air filters and the outside doors and windows are kept closed.
- • Cease the use of wood stoves, smoke, candles, or fireplaces during fire emergencies.
- • Delay the vacuuming of carpets during fire emergencies to prevent small particles from becoming airborne.
- • A person with any health or physical problems should immediately call the doctor for specific directions on what to do because of the fire.
- 10. Fugitive Dust (See the section on “Particulate Matter” above)
- 11. Hazardous Waste (See Chapter 12, “Solid Waste, Hazardous Materials, and Hazardous Waste Management”)
- 12. Internal Combustion Engines (See the section on “Mobile Sources” later in this chapter)
- 13. Iron and Steel Manufacturers
Iron and steel making consists of several processes which produce criteria air pollutants especially considerable particulate matter, sulfur dioxide, nitrogen oxides, hazardous air pollutants, and greenhouse gases. The greenhouse gases, primarily carbon dioxide, come from the production of coke; use of the blast furnace, boiler, process heater, reheating furnace, flame suppression system, annealing system, flare, ladle, re-heater, etc. (See endnote 7.) The processes, which produce numerous pollutants, include: sintering which recovers raw material from waste material; iron production from the original ore; iron preparation and removal of the sulfur; steel production; steel pickling which is the use of an acid solution to remove the oxides found in scale on the steel as it cools from its molten state; production of the semi-finished product; finished product preparation; and the handling and treatment of the raw materials, intermediate materials, and waste materials. (See endnotes 6, 70.)
Best Practices for the Iron and Steel Industry (See endnote 71)
- • Remove waste gas from the sintering process and utilize modern electrostatic precipitators followed by fabric filters to trap dust, heavy metals, sulfur dioxide, hydrochloric acid, polyaromatic hydrocarbons, and organochlorine compounds.
- • Use a wet scrubbing process with calcium oxide on waste gases to remove sulfur dioxide.
- • Use encapsulated or semi-encapsulated housings for the steps of coke crushing, raw material handling, belt charging and discharging, and sintering to trap and remove dust and associated contaminants.
- • Reduce the nitrogen oxides by rapidly cooling down flue gases.
- • Recirculate waste gas if it can meet the quality standards of the sintering process.
- • Reduce the heavy metals by using a wet scrubbing system.
- • Remove dust from bag filters and recycle byproducts containing iron and carbon and then place remaining dust in a secure landfill.
- • Use frequent and complete maintenance to keep equipment operating properly.
- 14. Land Development and Building Construction
Construction activities can produce substantial amounts of air pollution over short periods of time in a given area and therefore can have a substantial if limited local impact on people and the environment. Construction consists of site preparation, earthmoving including the hauling of the materials, the material used in paving of surfaces, tearing down of old buildings and structures, erecting new buildings and structures, waterproofing materials, paint for the structures, and tar for roofs.
The emissions coming from construction activities include particulate matter and fugitive particulate matter from concrete, cement, silica, disruption of the soil, various demolition activities, etc., and may have attached to them a variety of other contaminants; oxides of nitrogen and other contaminants from the combustion of diesel fuel and gasoline from large equipment, trucks used in construction activities, material delivery trucks, and the vehicles used by the workers; VOCs which come from paving activities and use of paint and tar, etc.; carbon monoxide from improper burning of fossil fuels; carbon dioxide from the burning of fossil fuels in diesel engines and construction equipment; asbestos previously used in a considerable amount of construction; mercury which can be found in demolition sites from switches, thermostats, electronic equipment, and batteries; lead which may be found in paints in older structures; and other toxic materials, such as arsenic, which was used previously to preserve wood.
The timing, magnitude, and duration of construction have to be taken into account when determining the problems related to release of criteria air pollutants, toxic air pollutants, and greenhouse gases. Weather conditions and existing levels of air pollution can complicate the problems of additional air pollutants released during destruction of facilities and preparation of the land and/or construction.
Best Practices for Land Development and Building Construction
- • Develop a construction proposal which enumerates the duration, type, and size of the construction and its component parts. What are the types of pollutants which will be added to the air, how much, and for how long?
- • Determine the countermeasures that will be utilized if equipment fails, such as dust collectors, etc., during the process of demolition or construction. Use controlled water spraying to mitigate dust problems.
- • Use equipment that crushes material and produces as little dust as possible, and which uses crushing under pressure instead of pounding.
- • Use equipment that contains dust traps which are cleaned and serviced regularly.
- • Enclose the filling and emptying mechanism of structures that contain powdery materials and then filter the air within the structure where materials are stored.
- • Use protective walls to prevent wind from blowing dust and other materials from road debris, etc.
- • Restrict speed on construction sites and reduce the dust through compaction and water sprinkling.
- • During demolishing of structures, break the demolition material into the largest pieces feasible to reduce dust.
- • Keep Hot remix tar-based coating substances for surfaces and sealing purposes away from building sites.
- • Use asphalt, pitch, or tar in an emulsion form instead of solution form, and use materials that have low emission rates of air pollutants.
- • Reduce welding emissions by capturing and filtering the fumes.
- • Use products which have less VOCs for painting, plastering, gluing, and sealing rather than more volatile ones.
- • Use low emission explosives.
- • Use low emission equipment, such as that with electric motors where possible.
- • Inspect and maintain all gasoline or diesel engine equipment in a very careful manner to prevent pollutants from entering the air.
- • Use dust abatement procedures such as wetting, trapping, suction, and filtering, for all dusty mechanical work.
- • Cover trucks when hauling dirt or other materials.
- • Stabilize the surface of dirt piles if they are not removed immediately.
- 15. Natural Gas and Crude Oil Extraction Industry
Natural gas and petroleum production from the well, processing, storage, transmission, and distribution, onshore or offshore, are the largest sources of methane emissions from industry in the United States. The oil goes from well extraction to the refinery for processing. The gas from the wells goes to gathering and boosting stations and then flows to processing plants, where impurities and water are removed and the gas can then be sent along pipelines to the ultimate user. All through this process, there may be a series of emissions to the air. If it is not cost-effective to use the gas associated with the oil, then it may not be handled properly and could become an air contaminant. All equipment used in drilling, other production operations, storage, and transportation become sources of air emissions.