Calculating Emission Rates and Heat Release Rates for Controlled Burns in Grass Fuel, Summaries of Forestry

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The: staff of the Southern Fomst Fim Labratory resptfully dedicP-iLes this work

to the memory of R o b & W. Cooper whose guidance and inspiration long helpd to

b ~ n gscience to the a r t of prescribed burning in the South.

HOW THIS BOOK WAS WRITTEN

Contributions from many scientists were required to complete this Guidebook. These contributors are listed as authors of the individual Chapters, and they take sole responsibility for technical content. Advice on overall content and applicability for users was provided by a group of eomprlers. The senior compiler worked directly with the authors to achieve a team product.

The compilers were:

SENIOR COMPILER Hugh E. Mobley, Technical Specialist Southeastern Area, State and Private Forestsy USDA Forest Service Atlanta, Georgia ASSOGIATE COMPILERS Charles R. Barden, Executive Director Texas Air Control Board Austin, n x a s A. Bigler Crow, Professor of Forestry Louisiana State University Baton Rouge, Louisiana Damin E. Fendec Director of Land Management International Paper Company Mobile, Alabama David M. Jay, Director Division of Fire Management Region 8, USDA Forest Service Atlanta, Georgia Ralph C. WinkworLh, D i ~ c t o r Division of Forest Resources Raleigh, North Carolina Additional contributions in the form of technical reviews and assistance have helped to shape the final result. m e ~ eare acknowledged in a Special Acknowledgments Section following the Glossary.

ABSTRACT

A system for predicting and modifying smoke concentrations from prescription

fires is introduced. While limited to particulate matter and the more typical southern fuels, the system is for both simple and complex applications. Forestry smoke constituents, variables affecting smoke production and dispersion, and new methods for estimating available fuel are presented.

KEIYWORDS: Air quality, pollution, prescribed burning, smoke management,

particulate matter, smoke concentrations, emission factors, com- ponents of forestry smoke, fuel loading.

TABLE OF CONTENTS

page

Adaptation of the Turner Workbook Methods to a Model for

• CHAPTER I: SMOKE MANAGEMENT WHAT IS IT? PERSPECTIWS .v - Purpose of These Guidelines. - A Source of More Information. - What's in This Guidebook. - There are Alternatives -
• FIRE SMOKE CHAPTER 11: CONTENTS AND EFFECTS OF FOREST - h e 1. - Burning Process. - Primary Products. - Secondary Products. - Particulate Matter
• CHAPTER 111: AIR QUALITY ADMINISTRATION - The Federal Clean Air Acts. - Applicable to Forestry Prescribed Burning A Review of Key Sections of the 1970 Clean Air Act (PL 91-604) - State and Local Air Quality Regulations. - Air Quality Control Regions and Maintenance Areas. - Prevention of Significant Deterioration. - A Voluntary Decision Procedure Proposed for Forestry Smoke Management
• CHAPTER IV: FUELS. FIRE BEHAVIOR. AND EMISSIONS
  • Variables Affecting Emissions and Fire Phases
    • Heat Release Rate to the Atmosphere.
    • Particulate Matter Emission Rate
  • Grass With Pine Overstory Fuel Type.
  • Pine Needle Litter and Light Brush Fuel Types. - Brush Fuel Types. Emission Factor for Slash and hblolly Pine Litter and Light
  • Palmetto-Gallberry With Pine Overstory Fuel Type.
  • Pine Logging Debris Fuel Type.
  • Conclusions
  • CHAPTER V: SMOKE TRANSPORT AND DISPERSION - Phenomena Affecting Smoke Transport and Dispersion - Pollution Climatology.................................................................... - Mathematical Models. - Managing Smoke h m Prescribed Fire in the South...................................... - Long-Range Transport - Limitations of the Mathematical Model....................................................
  • CHAPTER VI: HOW TO MANAGE SMOKE - Part 1 Planning for Smoke Management - Part 2 Decision Logic.................................................................... - Decision-Logic Stage No. 1: Initial Screening............................................... - Palmetto-Gallberry Fuel Type. Decision-Logic Stage No. 2: Rate Determinations for: - Grass With Pine Overstory Fuel Type.................................................... - Pine Needle Litter and/or Light Brush - Unpiled Logging Debris................................................................
    • Decision-Logic Stage No 3: Long-Range Margin
    • Decision-Logic Stage No. 4: Matching Prescriptions to Typical Cases......................... - Modifications, and Multiple-Source Analysis Decision-Logic Stage No. 5: Plots of Concentration, Comparisons, - Analysis Decision-Logic Stage No. 6: Automatic Data Processing Assisted
    • Part 3 .Tables.
• GLOSSARY
  • METRIC CONVERSION AM) PREFIX LE
  • SPECIAL ACKNOWLEDGMENTS

CHAPTER I

SMOKE NAGEMENT - T IS IT?

Hugh E. Mobley, nchnical Specialist

Southeastern Area - State and Priuate firestry USDA Flnrest Seruice Macon, Georgia

PURPOSE OF THESE A SOURCE OF MORE

GUIDELINES INFORMATION

This Guidebook is designed to help you deter- mine in advance:

IVIZAT YOUR FIRE WILL PUT INTO THE

AIR

WiYERE THIS MATERUL WILL GO

?V.HAT WILL H;.1PPEN IIYI)IT

T EFFECT IT WILL IrL4Vi

IVIZAT YOUCANDOABOUTIT

. ..and doing something about it to minimize en-

vironmental impact is smoke management.

As this Guidebook is being written, a parallel

Forestry Smoke Management Sourcebook is also

being developed. This Guidebook provides a great deal of information to practitioners in condensed

form, while the Sourcebook will provide much addi-

t i o n a l information to key specialists. Any

references made to the Sourcebook are intended to

let you know t h a t additional information is already available - at least in manuscript form.

The first edition of the Sourcebook will probably be

distributed in 1977 to regional and areal levels of the Forest Service and to State Foresters in a looseleaf format. Fire in the forest-natural, accidental, or deliberate- has been an important process in the

ecology of the south for thousands of years, WHAT'S IN THIS

especially in the fire subclimax pine stands of the

Coastal Plains. The use of prescribed fire to ac- GUIDEBOOK

complish specific forest management objectives is now regarded as an indispensable tool of the forest A lot of information is presented for the first manager ( ~ ~and b othersl ~ 1973). ~ m a y , nearly time in this Guidebook. Much is based on limited

3 million acres a year are burned by prescription in data and will^ be^ subject to updating. New infor-

the Southern United States. In the past, the mation forest manager had only a minimum of informa-

tion to help him determine what smoke from a

prescription fire would do to visibility or to the at- mosphere. This Guidebook was developed for southern forest-land managers who prescribe fires, and for

public agencies that are ~ s p n s i b l efor maintain-

ing air quality in southern rural areas where forests are burned. What is presented is based upon t h e best available technology. Because knowledge is presently incomplete, the scope is

limited to:

A broad breakdown of important southern fuels Single pmscription fires

A system for estimating total fuel loading

A system for estimating available fuel Particulate matter emission factors for major fuel types and burning techniques A procedure for detemining particulate mat- ter production rate

A proedure for predicting smoke concentra-

tions at any target area.

All are described in Chapters IV and I? This infor- mation is put together in a step-by-step decision- logic framework in Chapter VI that can be used

to predict what smoke from a planned burn will do

to the immediate airshed, and how it will affect

visibility at any point downwind. Predictions of particulate matter emissions Although much more information can be

only. found in the^ Soumebook^ that is being developed,

Table 1. --Considerations in reducing forest debris by different treatments

Considerations : Prescription burning Chemicals : Forced-air burners

Adverse effect Produces smoke on a i r

Adverse effect on water xone

Adverse effect on soil PJegligible

Chemical drift in foliar application

Very little visible emissions

May contaminate3 Negligible

Negligible2 Some compaction

Erosion Possibly on steep slopes5 ~ e ~ l i g i b l e " Possibly on steep slopes4' '

Overstory Negligible2 Negligible2 Skin t r e e s 4

Energy use None None to very little Very high

Portability a t s i t e Yes

Transportation Crew truck requirements

Yes None

Crew truck & / o r tank truck Lowboy & tractor ( 2 units) Spray unit if used

c o s t s 6 2 0 ~to $2.50/acre (avg. $1) $20 to^ $ 4 5 / a c r e^ (avg. $25)^ $5^ to^ $lO/ton^ of material Site preparation up to $ 6 / a c r e treated

Effectiveness Effective under stands

Effectiveness EXfective only on in the open s m a l l material

Advantages Inexpensive F a s t Multiple benefits

Effective on all s i z e s Not effective (live vegetation only)

Not effective on dead material

Effective

Versatile Can handle l a r g e boles Can t r e a t any s i z e material

Disadvantages Air pollution Public disapproval Need support equipment Usable days a r e limited Regulated Costly Not effective on l a r g e Possible offsite effects Cannot t r e a t understory m a t e r i a l Volume not reduced Increased fire hazard

Best use Hazardous fuel reduction Timber stand improvement Change in land use Wildlife habitat improvement o r conversion Site preparation Grazing improvement Right-of-way clearing

continued

Table 1. --Considerations in reducing f o r e s t debris by different treatments1 (continued)

Considerations : Drum choppers : Rotary-blade^ :^ Dozing o r shearing^ ' choppers : and root raking : A^ Total-tree^ chlppers

Adverse effect Only exhaust Only exhaust Only exhaust (^) Only exhaust on a i r emissions emissions emissions emissions

Adverse effect Kegligible2 Negligible" Sedimentation if Xegligible" on water on slope

Adverse effect Possible on soil compaction

Some compaction Compaction and Some compaction removal of topsoil

Eroslon Moderate to _ Possibly on Very susceptible5 Possibly on steep siopesa steep slopes6 steep s l o p e s 4 ~

Overstory Skin t r e e boles Xone & damage roots

Excessive damage Skin t r e e s 4

Energy use High High High Very high

Portability at site Limited in stands Limited in stands Limited in stands Kone

Transportation requirements Lowboy S; t r a c t o r Lowboy & t r a c t o r Lowboy & t r a c t o r Lowboy E; t r a c t o r (2 units)

c o s t s G $30 to $ 5 0 / a c r e $10 to $ 2 0 / a c r e $50 to $125/acre About $101ton of m a t e r i a l treated

Effectiveness Very limited Limited under stands Damage overstory

Cannot be used Not effective

Effectiveness Effective in the open

Effective on small Effective material

Effective

Advantages Effective in Effective on s m a l l Leaves ground clean Salable product logging resldue standing material Can handle l a r g e boles Thorough treatment

Disadvantages Damages leave t r e e s Limited where Debris left Need support equipment Blades tend to break can be used Erosion Initial investment on rocky ground Costly Cannot t r e a t understory Cannot t r e a t understory

Best use Site preparatron Maintenance of Change in land use Pulpwrood logging openings and Site preparatron Change in land u s e rights-of-way

'.Adapted from E a r r l s o n (19'75). "fmproper use could cause some adverse effects. 3 ~ flong-term chernrcals a r e used o r if treatment 1s close t o s t r e a m o r r e s e r v o i r. *Support equlprnent. "These treatments a r e not feasrble on s t e e p slopes due to erosion a n d / o r excessive cost- -and generally not needed. E ~ o s t sa r e usually higher In Predmont a r e a s.

Control of Undesirable Species In the absence of fire, most pine sites in the South tend to succeed to a climax type of scrub hardwoods. If these species are prmitted to in- vade and compete with overstory pine, production is impaired and regeneration is very difficult.

Complete elimination of understory brush is not ecologically desirable or economically practi- cal. It can be controlled with fire, however, if done while the understory is small. The resulting sprouts and growth of annuals provide good food and improved habitat for wildlife as well.

Disease Control

?b control brownspot needle blight (Scirrhia

acicola lDearn.1 Siggers) in longleaf pine (Pinus

palustris Mill.) seedlings, the infected needles

must be removed without damaging the bud. Fire is the only known practical way to properly remove the brownspot-infected needles of longleaf pines. Long experience with fire for this purpose has made it possible to do so without killing the bud.

Improve Forage for Grazing Cattlemen produce beef on forested ranges. However, native grasses in the timber understory are smothered by shrubs and inferior hardwoods. Periodic, low-intensity fires control competition and maintain the grass species. In addition, the grass produced after such burning is especially nutritious and palatable for cattle.

Other Objectives Other treatment objectives are to fireproof stands before initiating naval stores operations, to enhance esthetic appearance, and to improve ac- cessibility for timber operators and hunters.

UTILIZATION After allocating sufficient woody material to protect the soil from erosion, moisture loss, and un- wanted loss of nutrients, most managers of com- mercial woodland would like to utilize all the re- maining woody material for production of energy or as a raw material. Progress is being made in this

Figure 4. - Whole-tree chipping may be a practical alternative to burning in some places.

7

CHAPTER I

AND EFFECTS OFFOREST

FIRE SMOKE

Charles D. Rngren, Physical Scientist Charles K. McMahon, Research Chemist Paul W Ryan, Research Forester Southern Forest Fire Laboratory Southeastern Forest Experiment Station USDA Forest Service Macon, Georgia

The components of smoke are determined by the fuel and the process that converts this fuel to smoke. We therefore begin this Chapter with a description of the chemical elements of wood and the fuel. We then describe the process that first separates, and then recombines, these elements into the constituents of smoke. Although there are only a few major chemical elements in wood, the complex burning process results in numerous com- binations and thereby generates a large number of chemical compounds. We will then describe the products emitted from forest fires and their effects. Most investiga- tors have measured only the major combustion products: carbon dioxide (COz),carbon monoxide (CO), total hydrocarbons (HC), and particulate matter. A few have measured nitrogen oxides (NOx),organic acids, and aldehydes. The effects of forest fire smoke on man and his environment have not been measured directly. However, since the components of this smoke are similar to those of smoke from other combustion sources, we will draw information on effects from studies of in- dividual components. In the last section, we discuss particulate matter at some length. We provide detail on polycyclic organic matter (POMI and on physical characteristics. Size is perhaps the most impor- tant physical property of particulate matter. This size distribution is a good indicator of the potential for causing both health and visibility problems.

FUEL

ing land clearing and logging. Wildfires, which are often more intense than prescribed fires, may consume the foliage and small limbs of tree crowns, all litter layers, and organic soil. When burned, these fuel elements emit smoke with a chemical character that is basically determined by the chemical character of the fuel. Therefore, our discussion will start with an examination of the chemical character of forest vegetation.

CHEMICAL ELEMENTS

OF WOOD

Chemical analysis of wood shows that it is composed of about 50 percent carbon, 6 percent hy- drogen, 44 percent oxygen, and a fractional per- cent of what are called trace inorganic compo- nents. Surprisingly, there is only a minor difference in the major components between various wood species. The variability among trace components such as ash and nitrogen is greater.

Ash content varies from 0.2 to over 0.9 percent for

wood species in the United States. For nitrogen, the variation can be tenfold; for example, pon-

derosa pine (Pinus ponderosa Laws.) ranges from

0.13 percent nitrogen in boles to 1.04 percent nitrogen in growing needles. More than half of the elements in the periodic table have been found in plants. At least 27 ele- ments were identified in certain samples of white

pine (Pinus strobus L.) wood and others doubtless

occur in very small quantities.

Many of these elements are commonly recog-

The fuels of prescribed fires in the South, de- nized growth nutrients. Those occurring in fairly

scribedingreaterdetailinChapterIV,aremostly l a r g e q u a n t i t i e s a r e c a l l e d t h e m a j o r or

understory foliage, small branches, and the upper macronutrients: nitrogen, phosphorus,potassium, layers of ground litter. 1Cb a lesser extent, fuels also calcium, magnesium, and sulfur. Elements re- include the large branches and treetops left dur- quired in smaller quantities are the minor or

micronutrients: iron, manganese, zinc, copper, boron, and molybdenum. This list may be ex- panded further as more is learned about plants. Table 2 shows an example of the type and con- centration of trace elements.

Table 2. - Relative amounts of various elements found in dried leaf tissue of healthy plantsl'

Nitrogen Potassium Calcium Magnesium Phosphorus Sulfur Iron Boron Manganese Zinc Copper Molybdenum

Element

Percent

-^11 F'rom^ Kramer and Kozlowski^ (1960).

Content

the xylans, mannans, and glactans - plus related substances such as the uronic acids and their derivatives. No single, structural formula can be

presented for this group; in fact, objections are

oftezl raised to the use of the collective term hemicellulose. The hemicellulose content of wood varies from 15 to 25 percent, depending on species. The lignin portion of wood is quite different chemically from cellulose and hemicellulose. It consists of polymeric, aromatic materials charac- terized by the presence of phenolic hydroxyl groups. Lignin includes a variety of substances that have similar chemical compositions, but may have structural differences. The basic building block of lignin is the phenyl propane unit. The lig-

nin content varies from about 23 to 33 percent in

softwoods, and from about 16 to 25 percent in hardwoods.

Content percentage

BURNING PROCESS

How the components of smoke are generated from burning forest vegetation is best understood by recognizing that fire is a two-stage process of pyrolysis and combustion. Although both stages occur simultaneously, pyrolysis occurs first; it is

consideration of trace components may the initiating stage of chemical decomposition at

seem trivial and unnecessary at first glance. Trace temperatures-^ It^ is^ most^ often^ viewed^ as^ a

components, however, can cause major environ- heat-absorbing (endothermic) reaction that con-

mental problems. example, the emission of verts large molecules into smaller ones.^ Fuel^ ele-

sulfur oxides (regarded as a major pollutant) ments^ are^ separated^ into^ char,^ vapors,^ and^ high-

results from relatively minor amounts of sulfur in molecular-weight.^ ,^ hydrocarbons^ and^ particulate coal, oil, and other fossil fuels. matter. Combustion is the burning or rapid oxidation

CHEMICAL COMPOUNDS of the pyrolysateof the fuel. Defined in the most rigorous sense,^ vapors escaping from the surface

IN WOOD combustion is a relatively fast, heat-releasing (ex-

Ninety to ninety-five percent of the dry weight of wood is composed of three polymeric cell- wall constituents: cellulose, hemicellulose, and

lignin. The other 5 to 10 percent includes constit-

uents often listed as extractables or extraneous components. The extraneous components consist of several hundred individual chemical com- pounds that vary greatly between species, within species, and even within parts of the tree. In this group we find terpenes, tannins, resins, oils, pec- tins, gums, free organic acids, and minerals.

Wood contains between 41 and 53 percent cellulose. The composition of cellulose is quite uniform and independent of source; it consists of several hundred glucose-type carbohydrate units linked in a polymeric chain. Hemicellulose in-

cludes all noncellulosic polysaccharides such as

othermic), chemical reaction among pyrolysate vapors and oxygen. Pyrosynthesis is a third activity that is a part of both the pyrolysis and combustion stages. It forms large and complex organic compounds fronn smaller free-radical hydrocarbons in the high- temperature and low-oxygen regions of the fuel and combustion zone. The formation of these corn- pounds occurs in any combustion of carbonaceous fuel, and is due more to combustion charac- teristics than fuel characteristics. Brown and Davis (19731, Browne (1963),and

Murty W u r y (1972) have described what takes

place during combustion of forest fuels. Combin- ing their views, we can recognize three distinct phases of decomposition within fuel particles that are consumed. These phases-pre-ignition, flam- ing, and glowing -occur both sequentially and simultaneously in a moving fire front.