An overview of peat research, utilization, and environmental considerations

International Journal of Coal Geology, 8 (1987) 1-31 Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

1

An O v e r v i e w of Peat Research, Utilization, and E n v i r o n m e n t a l Considerations DAVID J. BORON 1, EARL W. EVANS 2 and JEFFREY M. PETERSON 3

1Virginia Polytechnic Institute and State University, Department of Mining and Minerals Engineering, 213 Holden Hall, Blacksburg, VA 24061, U.S.A. 2U.S. Department of Energy, Pittsburgh Energy Technology Center, P.O. Box 10940, Pittsburgh, PA 15236, U.S.A. :~New York State Energy Research and Development Authority, Two Rockefeller Plaza, Albany, N Y 12223, U.S.A. ( Revised and accepted for publication August 7, 1986)

ABSTRACT Boron, D.J., Evans, E.W. and Peterson, J.M., 1987. An overview of peat research, utilization, and environmental considerations. In: D.J. Boron (Editor), Peat: Geochemistry, Research and Utilization. Int. J. Coal Geol., 8: 1-31. The peat reserves in this country represent a vast resource for fuel and for chemical feedstock. As a fuel for combustion, peat generally has a low to moderate sulfur content (0.5-3.0% on a dry basis), a low to high ash content (5.0-20% on a dry basis), and an intermediate Btu content {6,000-10,000 per pound on a dry basis). As a chemical feedstock, peat can be extracted to provide various aliphatic, cyclic, and aromatic compounds, particularly oxygenated derivatives of these. Because of its chemical structure, peat provides a suitable feedstock for gasification not only for energy production but also for the synthesis of more complex compounds. In agriculture, peat and peat-derived chemicals are excellent soil additives and fertilizers. With such diversified application, peat is a valuable resource. The objective of this chapter is to provide some background information on peat and to overview select research, utilization, and environmental considerations involving peat.

INTRODUCTION Peat has formed throughout the world in areas of wetlands. On the North American continent, a principal area of wetlands formed as glaciers melted 9,000 t o 12,000 y e a r s a g o a c r o s s t h e n o r t h e r n t i e r o f t h e U n i t e d S t a t e s . A n o t h e r band of wetlands formed by erosion and sedimentation along the Gulf and Atlantic coasts. Wetlands and peat are also scattered throughout the western mountains and Pacific northwest. A 1982-survey of the United States, which included the State of Alaska, e s t i m a t e d t h i s c o u n t r y ' s p e a t r e s o u r c e s a t a b o u t 78 b i l l i o n t o n s a n d p l a c e d t h e

0166-5162/87/$03.50

© 1987 Elsevier Science Publishers B.V.

2 TABLE 1 Preliminary estimated U n i t e d States peat resources State

Q u a n t i t y (billions tons-dry basis) Soil survey estimation a

C u r r e n t state estimates

Alaska ~ Minnesota Wisconsin Louisiana Michigan N o r t h Carolina Florida Maine New York Massachusetts Georgia O t h e r states

40.1 10.7 4.2 2.7 6.7 1.8 4.5 1.2 1.0 0.5 0.7 4.2

40.1 4.0 2.3 1.0 2.2 0.6 4.5 0.7 0.2 0.5 0.7 4.2

Total

78.3

61.0

~Farnham, 1967. bExcludes peat in permafrost areas. Source: Honea, 1982.

recoverable fuel value of peat at about 1443 quads (1015 Btu), equivalent to 240 billion barrels of oil (Honea, 1982). Table 1 reflects the total estimated U.S. peat resources and the current state estimates based on fuel-grade peat (defined as peat with a minimum heating value of 8000 Btu/lb on a dry basis, a maximum ash level of 25% on a dry basis, and a minimum depth of 5 feet and area of 80 acres per square mile). Table 2 (Kivinen and Pakarinen, 1980) provides a 1980-estimate of world peat resources and peat production (the reader is cautioned that the peat resources reported in Table 2 are based on land area, i.e., hectares, and reflect 1980-estimates, whereas Table 1 reflects tonnage quantities as 1982-estimates).

Peatlands and the types of peat Peat is composed mainly of organic matter, with the organic content varying from a low of 20% (when classified under organic soils for geotechnical purposes) to as high as over 99% for very pure peats. Peat forms under saturated conditions when the rate of accumulation of plant material exceeds the rate of decomposition. The bacterial decomposition of the deposited vegetation is slow because of limited oxygen under the saturated conditions. As more vegetation is deposited and decomposes, the peat becomes layered or stratified. Peatlands can be classified according to their biological makeup and geolog-

TABLE 2 World peat resources Peat production ( t o n s × 103 )

Biological peatland ( h a X 106)

Fuel peat

Moss peat

Total

Canada USSR USA Indonesia Finland Sweden China Norway Malaysia United Kingdom Poland Ireland West Germany

170.0 150.0 40.0 26.0 10.0 7.0 3.5 3.0 2.4 1.6 1.4 1.2 1.1

-80,000 --3,100 -800 1 -50 -5,570 250

488 120,000 800 -500 270 1,300 83 -500 280 380 2,000

488 200,000 800 -3,600 270 2,100 84 -550 280 5,950 2,250

Total

417.2

89,771

126,601

216,372

Country

Source: Monenco Ontario, Limited, 1981.

ical setting. Biologically, a peatland is land having a water table near the surface and covered by vegetation typical of waterlogged conditions. Depending on its age, a biological peatland may not contain peat, since the accumulation of peat may not have had time to occur. Geologically, one can consider any land containing an overburden of peat of specified minimum thickness as peatland. For geologists, 30 cm is considered an acceptable thickness. For the peatmining industry, one meter is considered minable. Peatlands are commonly divided into bogs, fens, and swamps. Bogs are ombrotrophic (receive water and nutrients solely from precipitation), strongly acidic, poor in nutrients, and often dominated by stunted black spruce. Fens and swamps are minerotrophic (water and nutrients percolated through the mineral soil). Fens are rich in nutrients, have a pH between 4 and 7, are meadowlike, and have a cover dominated by sedges. Swamps are rich in nutrients, slightly acidic, and usually dominated by trees or small shrubs. Peatlands are formed by two processes: lakefill (hydrarch succession) and swamping (paludification ). Lakefill occurs as plants die and accumulate as a mat of peat that gradually fills the lake. Swamping occurs on areas that are poorly drained as vegetation dies, accumulates, and gradually expands in area. The composition of peat varies greatly among and within, peatlands because of the various types of contributing vegetation, the extent of decomposition, and the resulting chemical makeup. There are a number of classification schemes for peat depending on the specific uses. Most schemes incorporate the

degree of decomposition and botanical origin of the organic materials. One widely used scheme developed by von Post in the 1920's consists of a scale from H1 for undecomposed peat to H10 for completely decomposed peat (Stanek and Worley, 1983). The International Peat Society proposed a classification scheme in 1976 that contracts the ten-point von Post system into three divisions: R1, which includes H1-H3; R2, which includes H4-H6; and R3, which includes H7-H10 (Table 3, Minnesota Department of Natural Resources, Division of Minerals, 1984). A classification scheme commonly used in the United States references the degree of peat composition based on recognizable plant matter in the peat ( Peat Prospectus, 1979). The three categories - - fibric, hemic, and sapric - - are described below. Table 4 provides an overview of the peat classification schemes based on various physical and chemical properties ( Monenco Ontario, Limited, 1981 ).

Fibric peat. Fibric peats (peat moss) are generally younger peats. The organic fraction of the peat consists of more than two-thirds recognizable plant fibers of either Sphagnum, Hypnum, or other mosses. Fibric peats normally represent the latest deposit of organic matter within bogs and swamps. Decomposition has not progressed to where these peats would be valuable fuels, and because the fiber content is still fairly high, they have a water-retention capacity. Fibric peats also have low densities and usually very little ash.

Hemic peat. Hemic peats (reed-sedge) are formed from reeds, sedges, swamp plants, and trees that are somewhat older and more decomposed than fibric peats. These peats have about one-third to two-thirds of the organic matter as identifiable fibers, with the majority of the fibers coming from reeds, sedges, and other plants not of the moss family. Hemic peats are regarded as intermediate between fibric and sapric peats with respect to decomposition, bulk density, and ash content. They have a high energy value because of their high level of fixed carbon and their low ash content.

Sapric peat. Sapric peats (humus) consist of organic matter that is decomposed beyond botanical recognition. They are the oldest and most decomposed peats. Sapric peats are normally brown to black in color. Less than one-third of the organic fraction of this peat is recognizable fibers. Normally, sapric peats are the first peats formed when a basin is filled. Consequently, sapric peats are the most dense and colloidal (Cameron, 1980). Due to their colloidal strength, sapric peats take on less water but retain it more strongly than other peats. The ash content of sapric peats generally varies from as little as 2% to as high as 60% (well-decomposed organic material with high ash content is called muck). As a result, it has a lower value as a source of energy (Fuchsman, 1978).

TABLE 3 IPS three-grade scale of peat decomposition Scale grade

Percent of fibers

Structure and look of the peat bulk

Presence and look of humus

Amount and look of water

R1 Weakly decomposed peats

70%

Spongy or fibrous, built of plant residues tied with one another, For separation tearing off the plant residues is required. Easily recognizable plant residues (well preserved). Elastic, compact.

Not visible or occurs in little amounts as a dispersed dark mass, saturating and coloring plant residues,

Great amount of water, which can be easily pressed out and pours as a streamlet. Almost totally pure or slightly brownish. May contain dark h u m u s spots.

R2 Medium decomposed peats

70-40%

Amorphous-fibrous, grass and most peats contain numerous plant residues of various size; woody peats are more friable due to the presence of wood residues in amorphous humus. When pressed in fingers, transforms into an amorphous, plastic mass.

Distinctly discernible against which plant residues are visible. H u m u s can be pressed out between fingers of the clenched fist but not more than 1/3 of the taken sample.

Can be pressed out or flows by few drops; usually thick and of dark color/humus. In drained peat slightly colored with h u m u s coagulated in consequence of partial drying.

R3 Strongly decomposed peats

40%

Lumpy-amorphous, consisting in main part of humus. In lumpyamorphous peat greater fragments of plant residue/wood, rhizomes, greater rootlets occur. Friable, disintegrates under pressure. Amorphous peat strongly plastic, with sporadic greater plant residues.

Uniform mass, can be pressed out between fingers of the clenched fist in the amount of a half or the whole of the taken sample.

Cannot be pressed out, instead the h u m u s mass is squeezed.

Source: Minnesota Department of Natural Resources, 1984. PEAT: A DIVERSIFIED

FEEDSTOCK

As with many commodities and process feedstocks, the physical characteristics and chemical makeup of peat largely determine its most suitable use. The physical properties and chemical reactivities of peat can be compared most easily to those of cellulosic biomass and are highly characteristic of the plant

TABLE4 Classification of peats Type

Sphagnum moss peat (peat moss)

Hypnum moss peat

Reed sedge peat

Peat humus

Other peat

Minimum of 66 2/3 Sphagnum moss fibre

Minimum of 33 1/3 total fibre, of which over 50% is Hypnum moss

Minimum of 33 1/3 total fibre, of which over 50% is Reed sedge or other non-moss

Less than 33 1/3 fibre

All forms not otherwise classified

Farnham: Fibre, wt.% ~''h

Type

Sphagnum moss

Hypnum moss

peat

peat

Reed sedge peat

Partly decomposed ( reeds, sedges, grasses )

Decomposed ( humus )

3.2-4.0 48-80 90-0.5 0.7-1.2 85-95

5.0-7.0 64-96 90-92 1.5-2.5 80-85

4.0-7.0 80-96 90-92 1.0-2.5 70-80

4.0-7.5 112-192 80-90 1.2-3.0 40-60

3.5-8.0 280-480 80-90 1.5-3.5 10-20

--

4,5,6

7,8,9,10--

--

Hemic

Sapric - -

ASTM/Farnham': pH kg/m :~ Max. water, wt.% Av. nitrogen, wt.% h Av. fibre, wt.% h

yon Post degree of Humidification: 1,2,3

U.S. Department of Agriculture Soil Class: Fibric

~'Fibres are defined as plant material retained in an ASTM No. 100 sieve; that is, material 0.15 mm or larger, consisting of stems, leaves, or fragments of bog plants, but containing no particles larger than 0.5 inch (12.7 mm). It excludes fragments or other materials such as shells, stones, sand, and gravel. ~'Oven-dried peat, underground. 'ASTM Designation D2607-69 (effective April 25, 1969). American Society for Testing and materials. Source: Monenco Ontario, Limited, 1981.

matter from which the peat was formed. The variability of the plant matter, the deposition environment, and the age of the peat bog all impact the chemical and physical makeup of peat.

The chemical characteristics of peat Peat is composed primarily of plant matter and secondarily of mineral matter ( Raymond et al. 1987, this issue ). As for its chemical structure, peat is best described as a polymeric composite of plant ligno-cellulosic matter (Neavel, 1981; Rhoads et al., 1987, this issue; Ryan et al., 1987, this issue; Stout and Spackman, 1987, this issue). Because of the diverse plant matter and deposi-

tion environment influencing peat bogs, the chemical composition of peats can be quite different. The formation of peat is near the beginning of the coalification process, a process represented by the condensation and transformation of plant organic matter rich in oxygen and having a high hydrogen-to-carbon ratio to a condensed organic structure with a lower oxygen content and hydrogen-to-carbon ratio. Cameron (1980) depicted the peat stage of coalification by the reaction C72 H12o06o -~ C62 H72 024 with by-products largely of carbon dioxide and water. Orem and Hatcher (1987, this issue) described the diagenesis of peat as the loss of plant carbohydrates dissolved into pore waters, with those components of peat more resistant to degradation concentrated in the humin fraction. Since peat is at an early stage in the coalification process, with little organic plant matter transformation having occurred, the type of plant matter can be recognized and identified, hence, the botanical basis for many of the peat classification categories. Similarly, peat's basic composition allows for easily extractable and marketable products, such as waxes, acids, and polyaromatic hydrocarbons (Kumari, 1987, this issue; Spigarelli et al., 1987, this issue. The humic acid content of peat is of particular value for horticultural use. With proper conditioning, peat can store nutrient cations via its humic acids, and release them for the plant's use. A high cation-exchange capacity is common with most sphagnum peat types, even the energy peats (humification of' H9 or more). However, lower humified sphagnum peats with high water retention and structural resilience are more suitable for horticultural use than wellhumified peats. Humic acids, which do not occur in the living plant, are separated from peat by dissolving in alkaline solution and precipitating with acid. The structure of' humic acids may differ owing to the pretreatment of the peat, such as drying conditions, alkaline solution, and whether or not bitumens are removed first ( Fuchsman, 1983 ). Tri-, tetra-, and pentacarboxyl phenols have been isolated in humic acid decomposition studies (Schnitzer, 1981). Table 5 reflects the cation-exchange capacity for various peat types (Monenco Ontario, Limited, 1981). Table 6 provides a breakdown of the organic matter content represented in peat based on the degree of humification (Assarsson, 1961 ). Table 7 provides the elemental composition of peat based on the degree of humification (Fuchsman, 1980). The chemical composition provided in these tables is fairly representative of the composition of U.S. peats (Monenco Ontario, Limited, 1981; Raymond et al., 1987, this issue; Orem and Hatcher, 1987, this issue). Tables 4 and 12 provide some additional properties and chemical compositions representative of peat.

The physical and mechanical properties of peat The physical and mechanical properties of peat are also related to its chemical structure. Recognizing its early stage of coalification, the physical struc-

TABLE5 Cation-exchange capacity of peat types used for horticultural purposes Peat type

Degree of decomposition

Humic acid

Humin (me/100 g)

Total (me/100 g)

Total lime (kg/m 3)

Light sphagnum peat Dark sphagnum peat Very highly humified peat

H2 H4 H8

11 15 33

113 101 95

124 116 128

4.8 6.0 10.0

Values are for exchange capacity of humic acid relative to the weight of peat, in milliequivalents/100 g (me/100 g) and as lime in kg/m :~of peat at pH 7. Source: Puustjarvi (1977). TABLE6 Percentage of various organic matter in peats of varying degree of humification H1-H2 (% dry matter)

H5-H6 (% dry matter)

H9-H10 {% dry matter)

15-20 15-30 5-40 0- 5 1-10 3-14

5-15 10-25 5-30 20-30 5-15 5-20

0- 1 5-20 50-60 5-20 5-25

Cellulose Hemicellulose Lignin Humic acids Bitumen Nitrogen compounds Source: Assarsson, 1961. TABLE7

Elemental composition of peat ( % of dry organic material) Organic element

Slightly decomposed sphagnum peat a

Highly decomposed sphagnum b

Highly decomposed low-moor peat c

Carbon ( % ) Hydrogen ( % ) Oxygen ( % ) Nitrogen ( % ) Sulfur ( % )

48-53 5.0-6.1 40-46 0.5-1.0 0.1-0.2

56-58 5.5-6.1 34-39 0.8-1.1 0.1-0.3

59-63 5.1-6.1 31-34 0.9-1.9 0.2-0.5

~'Humification H I - H 3 (Post). L'Humification H6-H7 (Post). 'Humification H9-H10 (Post). Source: Fuchsman, 1980. ture of the plants that compose peat (such as sphagnum moss, sedges, trees, shrubs, and grasses) also account for its physical and mechanical properties. As with chemical makeup, these various properties are impacted by the depth of the peat in the bog.

5.0

\\ \

\

\ \\

1.0 c

\\\ \

\

\\\\ \\\ \ \\

o.1

\\~\ \\\\\\

8

C 1.5"~ 1.0t S

H

u

0.01

o.ool

r

'

2 3 4 5 6

I

~

I

8 g 10

Degree of Humification

0.1_]

0

I

20

I

50

i

80

Depth cm

l

120

Fig. 1. Hydraulic conductivity of sphagnum peat in vertical direction vs. yon Post degree of humification. Fig. 2. Hydraulic conductivity of sphagnum peat in three degrees of humification vs. depth.

The physical and mechanical properties of peat are of more value and interest from a non-energy perspective, e.g., for horticultural purposes, than for fuel use. For example, the permeability of peat is of practical importance when considering the drainability of peatlands for peat mining or forestry and agricultural uses. On-site permeability may affect water table fluctuations in drained peatland areas as well as the leaching or runoff of fertilizers from cultivated peatlands into adjacent streams or land areas ( Monenco Ontario, Limited, 1981 ). Permeability varies with the degree of humification, and with type and depth of the peat. For example, the hydraulic conductivity (permeability) of horticultural sphagnum peat is as high as 5 c m / m i n at a humification of H2, and as low as 0.01 c m / m i n at H8 (Fig. 1, Monenco Ontario, Limited, 1981). Peat permeability also varies with the depth of the sample. For example, sphagnum peat with a humification of H3 near the surface has a permeability value of about 1.1 cm/min. At a depth of 120 cm, however, an H3 sphagnum peat has a value around 0.4 c m / m i n (Fig. 2, Monenco Ontario, Limited, 1981 ).

10 The characteristics of select peat types that make them valuable for agricultural purposes are their high water-holding capacity, high cation-exchange capacity, high pore space, and relatively high permeability and compressibility. All these characteristics depend on the structure of sphagnum moss. Some other physical properties of peat are presented in Tables 4 and 12. Mineral matter in peat

The mineral matter in peat deposits may occur in situ (authigenic), originate outside the deposit (detrital), or result from alteration of other mineral species (diagenetic). The paper by Raymond et al. (1987, this issue) is an illustration of the significance of geographic setting with respect to detrital mineral matter deposits in a peat bog. The site selected for study (Cranberry Island, Maine), shows the influence of marine waters near the coastal edge of the bog in comparison to the bog's mineral and elemental composition farther inland. Another paper by Schell (1987, this issue) addresses the detrital deposition of a variety of trace and heavy metals in a uniquely situated peat bog in western Pennsylvania. The inference here is that the elemental composition of the bog is greatly influenced by heavy and trace metals from anthropogenic sources via dry and wet atmospheric deposition. The mineral matter content of an ombrotrophic bog in Maine consisting of muck (well-decomposed sapric peat) overlain by hemic and fibric peat layers is presented in Table 8 (Cameron and Schruben, 1983). The mean moisturefree ash content for the peat types sampled are 57.4% for the muck, 4.9% for the hemic, and 1.25% for the fibric. Similar chemical elemental composition was found from the leaching and accumulation of seven trace metals (Cu, Mo, Ni, Pb, Th, U, Zn) in the lower horizons of a bog in Colorado ( Sarneki, 1983 ). A range of values for 12 compounds in the ash composition of peats from Finland, Germany, Canada, and the United States are shown in Table 9 (Minnesota Gas Company, 1977, 1983; Monenco Ontario, Limited, 1981; Wheelabrator-Frye Inc., 1983; D.V. Punwani, pers. commun., 1986). An extensive discussion of peat mineral occurrence, forms, distribution, and analysis is presented in the proceedings of the Workshop on Mineral Matter in Peat, which was held at Los Alamos National Laboratory in 1983 (Raymond and Andrejko, 1983). Peat petrography/microscopy

Cohen has sought to define peat types based on their botanical and "premaceral" compositions (Cohen and Andrejko, 1984). "Premacerals" are the organic components in peat that likely represent the predecessors of corresponding macerals in coal. The color, opacity, shape, fluoresence, and chemical

11 TABLE 8 Means for ash and elements in each type of organic material in the great heath Ash and element

Muck

Hemic peat

Fibric peat

Ash Fe Be Pb Ga Mg Y Nd Ca Cd Zn Ti Co Zr Mn Cr Sc Si Ag Cu Sn Al La Sr Na Mo K B Nb P Ba Ni V Ce Yb

57.4% 1.73% 1.90 17.33 9.84 0.49% 12.33 33.52 0.60% -30.18 0.11% 6.39 109.32 312.90 40.05 8.55 14.54% 0.09 22.60 3.19 4.87% 20.17 110.31 1.15% 0.82 1.25% 35.41 7.37 0.80% 237.99 16.81 39.98 46.04 2.68

4.9% 0.40% 0.20 2.09 0.58 0.44% 1.39 4.27 0.24% 0.87 9.70 0.007% 0.69 5.55 176.00 3.59 0.79 0.51% 0.02 7.82 0.37 0.21% 3.03 35.54 0.05% 0.48 0.57% 8.23 3.67 0.35% 22.60 2.38 2.67 13.80 0.20

1.25% 0.08% 0.01 1.24 0.78 0.10% 0.11 0.54 0.09% 1.03 .388 0.001% 0.15 1.08 35.57 1.33 0.08 0.07% 0.007 1.50 0.07 0.03% 0.34 13.3 0.03% 0.10 0.008% 2.67 0.07 0.01% 6.06 1.14 0.43 0.58 0.008

Note: Ash is moisture free. Elements obtained from ash are calculated on whole-sample basis and given in parts per million unless indicated in percent. Source: Cameron and Schruben, 1983. c o m p o s i t i o n ( p r o x i m a t e a n d u l t i m a t e ) of these c l u e s i n a s s e s s i n g t h e i r role as p r e c u r s o r s t o coal T h e value a n d objective of p e a t p e t r o g r a p h y c o m p o n e n t s are precursors to the m a c e r a l s f o u n d

"premacerals" are important macerals. are in assessing which p l a n t i n coal, r e c o g n i z i n g t h a t s o m e

12 TABLE 9 Ash composition of peats from Germany, Finland, Canada a n d the U n i t e d States Substance

Germany~

Finland 2

Canada 3

U n i t e d States 4

CaO AI20:~ SiO_, Fe=,O:~ S MgO Mn0 K~O Na~O P~O;

2.0-45.0 1.0-11.0 10.0-45.0 1.5- 5.5 1.0-20.0 0.1- 0.3 0.1- 2.5 0.2- 5.0 1.0- 3.0

1.5- 4.6 1.3- 5.1 50.0-72.0 4.6- 7.1 0.2

1.3 -42.7 3.3 -23.1 7.9 -38.8 2.4 -11.6 0.01- 0.75 1.3 -27.8 0.1 - 0.2 0.4 - 2.8 0.3 - 2.0 0.0 - 2.6

2.3-47.8 5.1-16.6 42.0-91.2 0.3- 8.9

2.3- 4.2

0.5- 7.0 0.2- 2.8 0.1- 2.9

Sources: lNaucke, 1968. 2Ekman, 1976. :~Korpijoakko a n d Phenney, 1975; Tibbets, 1976. ~D.V. Punwani, pers. commun., 1986; Wheelabrator-Frye Inc., 1983; M i n n e s o t a Gas Company, 1977 a n d 1983.

transformation of plant matter has already occurred and that the coalification process is at its initial stage. Early work in this area was conducted by Thiessen and White (1913) and Stopes (1919), who studied coal with the objective of identifying plant components. Table 10 (Ting, 1982) presents the classification and categorization of coal components reflecting likely plant origin according to Thiessen. Since this time, there have been many efforts involved in correlating plant contributions to coal composition (Neavel, 1981 ). Stout and Spackman (1987, this issue) compared degraded woody tissues from peats with fresh wood from southwest Florida and the Okefenokee Swamp in Georgia. Remnants of other plant parts (leaves, pollens, spores, fungal remains, etc. ) and their degradation in peats from the same geographic region have been investigated previously ( Cohen and Spackman, 1977). Cohen and Andrejko (1984) conducted the petrographic characterization of peats from Minnesota, Maine, North Carolina, and Georgia. Preliminary relationships of petrographic parameters for the peats with industrial properties, such as dewatering potential, volatile matter content, and organic chemical yield (Cohen, 1983 ), and proximate and ultimate analyses (Cohen and Andrejko, 1984) have been reported.

13 TABLE 10 Microscopical composition of coal Occurs in bands ranging in thickness from 0.0145 m m to several millimeters. Cellular structure is usually distinctive, revealing functional nature of plant tissues, intensity of color increases with rank from yellowish to orange, bright red, and dark red.

Derived from wood, bark, root, leaf tissues, and tissues of certain fruiting organs of herbs, shrubs, and trees; retain well-preserved structural evidence of original fl~rms.

Translucent humic matter

Occurs in thin anthraxylon-like shreds less than 0.0145 m m thick, small irregularly shaped particles, and aggregated masses of close packed particles. Resembles anthraxylon in color, which varies to the same degree.

Derived from the parts of plants similar to the parent material of anthraxylon, subjected to intense biochemical degradation, which destroyed structural evidence of original plant forms.

Brown matter

Occurs closely associated with opaque matter and translucent hemic matter; resembles these in general appearances except for its semitranslucency and absence of granular structure at high magnification.

Derived from plant remains similar to parent material of translucent hemic matter, subjected to more than ordinary biochemical alteration, which resulted in incomplete carbonization apparent microscopically in the semiopaque quality and gradation into opaque matter.

Opaque matter

Occurs in attritus as irregularly shaped particles and distinctly blacked aggregated masses. Opaque quality persists in all sections of normal thinness. Reveals granular structure at high magnification.

Derived from plant remains similar to the parent substance of brown matter, subjected to intense biochemical alteration, which resulted in a certain degree of carbonization readily apparent microscopically in the granular structure and true opaque quality. No structural evidence of original plant forms.

Spore and pollen remains

Occur in attritus as yellow particles of definite structural form varying in shape and size. The individual spores and pollen forms can be specifically identified. Color slowly deepens with increasing rank.

Derived from the protective coverings of spores and pollen, reproductive organs of spore- and pollen-bearing forms of' vegetation.

Anthraxylon

Attritus

Source: Thiessen and White (1913).

PEAT: A DIVERSIFIED

PRODUCT

Peat has been used in Europe as a fuel for cooking and heating for centuries. Other commercial products from peat are peat wax (Soviet Union), coke (Germany, Finland), activated carbon (The Netherlands), electrical utility

14

fuel ( Soviet Union, Finland, Ireland), and agricultural and horticultural growing medium. The particular product largely depends on the characteristics of the peat feedstock, i.e., degree of humification, ash content, etc.

Preparation Mining Peat is mined in either the dry or wet form, referring to the condition under which the peat is handled and removed from the original site. Dry mining is often referred to as harvesting owing to the similarity to equipment and techniques of agriculture. Because harvesting incorporates spreading and drying in the field, it is strongly dependent on weather conditions and is feasible only when evaporation exceeds precipitation (a function of the daily temperature, the number of daylight hours, and the number of consecutive days permissible for harvesting). The total harvesting season is generally limited to about 2-4 weeks before the last freeze day in the spring and perhaps a month after the first freeze in the fall, depending on the geographic location. As an example, the harvesting season in Virginia, Minnesota (47 ° 32'N) is about 50-60 days (Zandlo, 1984), while that for Creswell, North Carolina (35°49'N) is about 140 days (Robinson et al., 1983). (See Zandlo, 1984, for an analysis of the climatic conditions for peat harvesting in Minnesota. ) Dry mining can be classified into milled and sod methods. Both require draining the bog through a pattern of ditches and canals, and clearing the surface. Milling, which is employed in Finland, Ireland, Canada, and USSR, entails scarifying the surface and milling up to 2 inches deep, the depth depending on drying conditions (as an example, Finland mills to about 0.5-inch depth, while North Carolina mills to 1.5-2 inches). The milled peat is turned with a harrow and ridges until sufficiently dry (1-3 days), and then is transported to a field Stockpile. The milled peat product is sized to 1.5 inches, with a mean of 0.1-0.3 inch. The moisture content of the peat product thus prepared is generally less than 50%. Sod peat is obtained by either excavating narrow channels of peat from 10to 40-inch depth or by the bagger method used in Ireland where the peat is cut in a 5-foot-wide section from the vertical face of a well-drained bog. The peat is then macerated, extruded in 2- to 4-inch-diameter cylinders or 4- to 5-inchsquare cross sections, and left for air drying. These methods produce a sod moisture content of about 35% after 5-15 days, depending on weather conditions. Sod production of peat is not as weather-dependent as milled production because the surface of the sods tend to harden and become somewhat waterrepellent. Wet mining is used where more valuable sphagnum peat is produced for horticultural use ( Mankinen and Gelfer, 1982; Carncross, 1983 ). Wet methods can be used where dry methods are not feasible because of drainage or climate.

15

In the slurry pond method of mining, the most common approach, peat is extracted from an unprepared bog by employing a dredge with a cutter suction head. An operation in Louisiana produces a slurry of 2-4% peat that is pumped to a settling basin and later removed and spread for air drying (Ludlow and deBakker, 1982 ). A method once in operation in British Columbia used a clamshell on a hover-barge to mine the peat (Carncross, 1983). The peat was screened and pumped to a dewatering plant, where mechanical pressing and thermal drying were used to prepare the product for horticultural uses. Although wet mining can be used in northern climates for a longer season than dry mining, it is not economically competitive owing to energy-intensive slurry pumping (Carncross, 1979a, b) and the lack of economical dewatering methods. Ludlow and deBakker (1982) have provided an evaluation of novel systems for both wet and dry mining methods.

Dewatering In situ peat contains about 90% water by weight, while most uses of peat require that it be at least 50% solids. Water is retained in peat by the macropores contained in the original plant materials, by micropores derived from degradation of the plant material that is colloidally bound, and by chemisorption (Chornet et al., 1981 ). The amount of water retained is dependent on the peat type and the degree of humification, with the low humified peat retaining more water than the highly humified peat. Conventional methods of dewatering generally involve harvesting and spreading for air drying. This technique depends on a combination of weather conditions, including precipitation, temperature, and insolation. Although this approach has limited application in higher latitudes owing to short harvesting seasons, it can generally produce a peat with an acceptable moisture content (50% or less). Mechanical pressing of peat serves to remove the loosely held water and commercially available presses can provide a product with 65-70% water. Mechanical pressing, however, cannot remove the more highly bound water. Two representative mechanical presses for peat dewatering are made by Ingersoll-Rand and Sulzer Brothers (Switzerland). The Ingersoll-Rand press uses perforated horizontal rollers, whereas the Sulzer press utilizes a special belt system that is pressed between a large number of rollers. Both presses are capable of producing a product of 65-70% water from a well-humified peat (H6-H7) ( Monenco Ontario, Limited, 1981 ). The Institute of Gas Technology has conducted dewatering tests using a newly designed press with a 24inch-o.d, roller inside a 34-inch-i.d. cylinder that yielded a dewatered peat with about 50% water (Lau et al., 1986). Solvent extraction is another means of dewatering peat. In theory, the operation involves contacting peat with an organic solvent in which the water is extracted into the organic phase. Economics dictate that the two-phase water-

16 solvent system must be separated for reuse of the solvent. As an example of this approach, Honea et al. (1981) used acetone with a contact time of two minutes followed by pressing to reduce the moisture in peat to 22%. Workers at the Institute of Gas Technology (Paganessi et al., 1981 ) have used the temperature dependence of the solubility of water in solvent as a means of separating the aqueous and organic phases. In this approach, the peat is contacted with solvent at elevated temperatures when the water solubility is high. The two-phase system is then separated at lower temperatures when the water solubility is significantly less. Diethyl ketone (DEK) solvent gave the best results in terms of water extraction and reagent recovery. In work using Minnesota, Maine, and North Carolina peat feedstocks, the moisture was reduced to 67% after phase separation and ultimately to about 50% after pressing. Although benzene was less effective than DEK in the extraction step, it provided lower moisture content ( 26% ) after pressing.

Peat for chemical and agricultural uses There are various uses of peat that are related more to its physicochemical properties than strictly to its energy content. Examples that will be briefly discussed include the cultivation of yeast and solvent extraction for chemicals. The most valuable use of peat, perhaps, is for agricultural and horticultural purposes. Sphagnum moss peat is typically mined as milled peat, then air dried, compressed, and packaged in bales for shipment. It is used as a growing medium for greenhouses and for household, domestic, and commercial gardens; in landscaping; and in the manufacture of peat pots, pellets, growing plates (instant lawn), and insulating boards, to mention a few. Sphagnum peats of a low degree of humification (H2-H4) are the most suitable peat for these purposes, although peat with a humification value of H5-H6 might also be suitable in some cases. The characteristics of low humified sphagnum peats that make them suitable for agricultural purposes are their high water-holding capacity, high cationexchange capacity, high pore space, relatively high permeability, and high compressibility.

Cultivation of yeast The acid hydrolysis of peat yields products that can be used as a culture medium to grow yeast or other microorganisms. While peat is high in cellulosic material, the hydrolyzates contain reducing sugars and nitrogen required in metabolism of yeast. The amount of reducing sugars and total nitrogen obtained depends on the particular acid hydrolyzing agent and concentration of acid (see Table 11; Chang, 1983). The species of yeast can be optimized for the production of alcohol or single-cell protein, which are the two products of most interest. Other products are fat and carotene (Fuchsman, 1978).

17 TABLE 11 Reducing sugars (RS), total nitrogen ( TN ), and dextrose equivalent values (DE) in peat hydrolysates using various hydrolyzing acids Normality of hydrolyzing acid 0.5 N

1.0 N

Acid

RS

TN

HC1 H~S04 HNO:~ H:~PO4

3.46 3.62 2.89 3.33

0.37 0.40 -0.36

DE 8.5 8.9 7.1 8.2

1.5 N

RS

TN

DE

4.80 4.55 3.50 4.67

0.49 0.52 -0.50

11.8 11.2 8.6 11.5

2.0 N

Acid

RS

TN

DE

RS

TN

DE

HCI H2 SO4 HNO:~ H:~PO4

5.45 5.08 3.74 5.33

0.56 0.58 -0.54

13.4 12.5 9.2 13.1

5.98 5.53 3.98 5.73

0.58 0.65 -0.57

14.7 13.6 9.8 14.1

Note: Presented values are the means of three replicates; DE = 100 ( %RS/% dry solid) ; RS and TN are given in g/1 of hydrolysate. Source: Chang, 1983. S t u d i e s b y C h a n g (1983) of t h e g r o w t h f a c t o r s in t h e p r o d u c t i o n of singlecell p r o t e i n f o u n d t h a t sulfuric acid h y d r o l y z a t e was t h e b e s t g r o w t h m e d i u m for Torula (Candida) utilis. T h e r e w a s also good c o r r e l a t i o n b e t w e e n t h e r e d u c i n g - s u g a r c o n t e n t a n d t h e b i o m a s s of C. utilis. A m i x t u r e of g r o w t h factors, s u c h as v i t a m i n s ( t h i a m i n t h e m o s t e f f e c t i v e ) a n d a m i n o acids, s t i m u l a t e d g r o w t h m o r e t h a n a n y single c o m p o n e n t . T w o g r a d e s of s p h a g n u m a n d one of fuel p e a t , a n d five d i f f e r e n t species of e t h a n o l - p r o d u c i n g y e a s t h a v e b e e n r e p o r t e d for t h e f e r m e n t a t i v e p r o d u c t i o n of e t h a n o l f r o m sulfuric acid p e a t h y d r o l y z a t e ( L e D u y a n d L a r o c h e , 1983). T h e c u l t u r e m e d i u m c o n t a i n e d n i t r o g e n , sulfur, p o t a s s i u m , a n d m a g n e s i u m n u t r i e n t s in t h e f o r m of ( N H 4 ) 2 8 0 4 , K2 H P O 4 , a n d MgSO4" 7 H 2 0 . H o r t i c u l t u r a l s p h a g n u m p e a t yielded high t o t a l c a r b o h y d r a t e , w h e r e a s fuel p e a t yielded low t o t a l c a r b o h y d r a t e .

Solvent extraction S o l v e n t e x t r a c t i o n c a n be u s e d as a m e a n s to d e w a t e r p e a t or to o b t a i n c h e m ical f e e d s t o c k s s u c h as b i t u m e n s , oils, or waxes. A c o m b i n a t i o n of p r o c e s s e s

18 can be used to produce dewatered peat and chemicals depending on the solvents (the use of solvents for the purpose of dewatering was discussed previously). Organic solvents can be used to dissolve the peat bitumens and separate them from the bulk peat solids. Two papers contained in this issue give results on the solvent extraction of peat bitumens. In the paper by Kumari (1987, this issue), the extraction is performed on air-dried peat, whereas the paper by Spigarelli et al. (1987, this issue), compares the solvent extraction yield of bitumens from air-dried peat with that from peat that has been subjected to hydrolysis or wet carbonization. Peat for energy uses

The value of peat as a fuel for energy is largely related to its fixed carbon content. As peat ages, there is a gradual increase in the fixed carbon with the conversion of carbon, hydrogen, and oxygen to water, carbon dioxide, and methane. In this manner, the cellulose and lignin matter of plants is condensed and converted to a structure more complex and representative of coal. The corresponding increase in the fixed carbon is accompanied by a reduction in volatiles. This condensation process is characteristic of the coalification process. Thus, peat deposits may be considered as the initial stages of a coalification process that takes millions of years, and peat can be represented in geological terms as a young coal. The value of any fossil deposit as an energy source is largely related to its fixed-carbon, volatile, and oxygen contents. Figure 3 shows the correlation of carbonaceous matter according to age and composition (Peat Prospectus, 1979). Note that peat is the youngest of the fossil fuels and contains high volatile and oxygen contents and a low fixed-carbon content compared with those of the other fossil fuel types. This correlation is further exemplified in Table 12 (Monenco Ontario, Limited, 1981 ). The peat information provided in this table is based on high-quality fuel peat from Europe. These values are fairly representative for all peat, but the ranges are not all-inclusive for peats found in the United States and Canada. The basic characteristics sought for an energy peat are a high degree of humification (high fixed carbon), high bulk density, relatively low ash content, low pollutants content ( such as sulfur), and a high calorific value (indicative of a higher humified peat). Sphagnum peats with a humification of H4 or greater and sedge peats ( H3 or greater) represent excellent sources of peat for energy use.

F u e l uses

As a source of fuel, peat has found application mainly in residential heating and power generation. In the Soviet Union, peat is used predominantly as a

19 GEOLOGIC RECENT

TERTIARY 65 MILLION YRS

AGE

CRETACEOUS I O0 MILLION YRS

ii =-

CARBONIFEROUS 300 MILLION YRS 16 15

14

0,-

-

o"=

Z g.~ 12 _j~

~_~ ~

'"

'~o 9

B I,-

Fig. 3. Comparisonbetweenpeat and older coals. residential heating fuel in rural areas of the country, but it also has significant use in electric power generation. Eighty power stations totaling 5000 MW represent about 1.5% of the total generating capacity in the Soviet Union. In regions where power demand is near peatlands, power produced by peat represents 10% of the supply capacity (Mankinen and Gelfer, 1982). Peat is also used for power generation in other countries. For example, in Ireland, power generation from peat represents about 17% of the total; Finland started using peat for power generation in 1972 and maintains a small capacity load (Electric Power Research Institute, 1983). Peat is fired in two forms: sod (shaped bulk) and milled (shredded). Sod peat generally is used for small grate or fluidized-bed boilers. Milled peat on the other hand, can be fired in grate, cyclone, pulverized-fuel, and fluidizedbed boilers. The larger utility boilers (100 MW) are fired with milled peat in a pulverized fuel-type boiler. Peat-fired boilers are larger than coal-fired boilers of the same rating owing to the longer residence time required for complete combustion and to the greater radiant-heat-absorbing surface to minimize slagging and fouling (Electric Power Research Institute, 1983).

0.1

9"20-970 900-10,000

83-86 11.5-12.5 1.5-2.5 0.2-0.3 2.0-2.8 0.3

Source: Monenco Ontario, Limited, 1981.

Carbon ( % ) Hydrogen ( % ) Oxygen ( % ) Nitrogen ( % ) Sulfur ( % ) Ash content ( % ) Melting point of ash (%) Volatiles (%) Specific gravity (kg/m :~) Effective heat value of dry matter (kcal/kg) Operational moisture ( % ) Effective heat value at the lowest operational moisture content (kcal/kg) Effective heat value at the highest operational moisture content (kcal/kg)

Heavy fuel oil

Comparison of various fossil fuel types

TABLE 12

40-60 2640-3240

1560-1960

6200-7220

65-75 4.5-5.5 20-30 1-2 1-3 6-10 1100-1300 50-60 650-780 4800-5800

Coal (lignite)

3-8 6570-7640

76-87 3.5-5.0 2.8-11.3 0.8-1.2 1.0-3.0 4-10 1100-1300 10-50 720-880 6800-7900

Coal (bituminous)

1780-1960

40-60 2500-3000

50-60 5.0-6.5 30-40 1.0-2.5 0.1-0.2 2-10 1100-1200 60-70 300-400 4700-5100

Peat

1550-1740

30-55 2900-3040

0.4-0.6 1350-1450 75-85 320-420 4400-4600

48-50 6.0-6.5 38-42 0.5-2.3

Wood

t~

21

Sod peat boilers fire fuel with about 50 percent moisture and incorporate the fuel drying on the grate. Milled peat firing in pulverized fuel boilers uses hot flue gas to dry the fuel in the pulverizer (to about 20% moisture) for suspension firing. Fluidized-bed boilers are of two types: (1) conventional, with the bed occupying the lower part of the boiler, and the bed temperature controlled by water tubes in the bed or by excess air; and (2) circulating, where the bed expands out of the primary chamber to a cyclone separator, and the material is recycled to the primary bed. Fluidized-bed boilers are the preferred approach to combusting peat owing to their versatility in handling peat containing wide ranges of moisture and ash.

Peat processing Processing peat is generally undertaken to achieve better handling characteristics, better dewatering, and higher heating value, or to extract chemicals. Thermal treatment of raw peat at atmospheric pressure is generally too energy intensive to be economical, although it has application to further dewater peat under pressurized conditions. Table 13 provides an overview of a number of processes employing thermal methods for dewatering peat under pressure. In general, the severity of the processing conditions can be classified by the ratio of carbon to oxygen in the product to that in the feedstock (Leger et al., 1987, this issue). The process conditions provided in Table 13 present a range of operating parameters, but a set of optimum conditions in terms of economics and energy use depend on several factors, such as the particular peat feedstock, size of plant, by-products, and water processing. The low-severity and wet-carbonization processes are described later in this volume (Leger et al., 1987, this issue; Lau et al., 1987, this issue). The wetoxidation processes differ from those of wet carbonization in the heat source for raising the process temperature. In wet oxidation, part of the peat feedstock is combusted by the air or oxygen within the process. In wet carbonization, however, the heat source is external. All of the processes shown in Table 13 are capable of dewatering raw peat except the Koppelman process, which requires a feedstock that has been dewatered to 50 percent moisture. A technical and economic evaluation of these processes has been performed by Montreal Engineering Company, Ltd. (1983). Conversion The gasificat!on of peat requires a dried feedstock (50% moisture or less) before reaction with air or oxygen and steam in a reactor. The products provided include a mixture of CO, H2, and CH4 gases; solid char; and some liquids. Using peat in a coal gasifier may require unique preparation and feeding systems, and a modified reactor to accommodate the low density and low ashmelting temperature of peat. Because of its high-volatile matter content, peat

22 TABLE 13 Operating parameters of selected peat-processing technologies Process

Temperature ( °C )

Pressure (MPa)

Time (min)

Source footnote

90-190 175-290 210-220 320-420

1.4-2.8 1.3-7.6 3.4 5.5-13.8

0.25-1.4 1-30 30 15-30

1 2 3 6

150 204

2.2 4.6

Wet carbonization

Low severity IGT JP-energy Koppelman Wet oxidation

Zimpro (3% oxidation) ORF (10.7% oxidation)

30 10

4 5

1. Leger et al., 1987, this issue. 2. Lau et al., 1987, this issue. 3. Rohrer, 1984. 4. Canney et al., 1983. 5. Gallo and Sheppard, 1981. 6. Montreal Engineering Company, Limited, 1983. is a much more reactive feedstock than coal or lignite. In general, the char produced is more reactive than coal char, and less gas cleanup is required because of the lower sulfur content. A literature review of early peat gasification was conducted by Leppamaki et al. (1979). The status of peat gasification projects in 1981 is given in the symposium papers of the Peat as an Energy Alternative II, Arlington, Virginia ( Gallo and Sheppard, 1981 ). The largest project involving gasification was the P E A T G A S pilot plant that achieved integrated operation in 1981 at a rate of 2-tons-feedstock per-hour (Biljetina and Punwani, 1981 ). A feasibility study was performed for the Minnegasco peat gasification plant to be sited in Minnesota that would produce 80 million cubic feet per day of substitute natural gas using the P E A T G A S technology (Minnesota Gas Company, 1982). Other gasification techniques that have been studied include a 1/2-ton feedstock-per-day fluidized-bed reactor (Lau, 1981) and a 3/4-ton-per-day unit for hydrogasification in an entrained bed (Friedman and Garey, 1981 ). Liquid fuels can be produced from peat through direct or indirect processes. Research on direct liquefaction of peat has been conducted on a laboratory scale (Punwani, 1981 ). Most of the research has been directed at peat conversion in the presence of reactant gases (H2 and/or CO), at relatively low temperature ( 300-500 ° C ), and pressures high enough to prevent vaporization of the water. Indirect liquefaction incorporates a gasification step to produce synthesis gas (H2, CO) and then converts the synthesis gas catalytically to liquids. A major indirect liquefaction project was planned by Peat Methanol Associates

23 that involved a facility to convert milled peat to methanol near Creswell, North Carolina. The project, planned for startup in 1986, was to convert 2600 tons of peat (40% moisture) per day into 200,000 gallons of methanol per day. The project was cancelled after attempts to receive loan and price guarantees from the U.S. Synthetic Fuels Corporation were unsuccesssful (Robinson et al., 1983). PEAT AND THE ENVIRONMENT Peat is a nonrenewable surface resource, the mining of which changes the local environment and may impact, to some extent, regional environmental variables. Effective peatland management and utilization depend not only on the selection and development of appropriate technologies and markets but also on the knowledge of the specific peatland ecosystem and the varied benefits it may provide. Of major concern and consideration in this regard are water resource impacts, water quality impacts, and biological resource impacts. Air quality impacts during the mining phase are generally minor. During utilization, however, air quality impacts depend on the end-use application (i.e., fuel, horticultural, etc. ). In most cases, any adverse air-quality impacts can be readily mitigated through the use of existing control technologies (i.e., baghouse, FGD, etc. ). Water resource impacts

The peatlands' existence is controlled by the hydrological regime of the site, and in turn, the peat mass influences the surface and groundwater flows from the site ( King et al., 1980 ). Peatlands ( when also considered wetlands ) gather precipitation runoffand help in regulating the release of water to streams, thus reducing peak flood flows ( Larson, 1973). Peat mining can impact the hydrologic budget associated with the surrounding area. Actual impacts on and off the site are a function of the size of the operation, the procedures followed in mining, and the peat-processing technology utilized (Newman et al., 1985). Hydrologic issues, listed in decreasing order of importance, include the following ( Newman et al., 1985 ) : (1) Floodwater runoff response (2) Groundwater elevations (3) Surface flow patters (4) Minimum stream discharges (5) Mean surface-water discharges (6) Hydrologic budgets (7) Groundwater aquifers (8) Evapotranspiration rates. Table 14 provides a judgment as to the magnitude of potential environmen-

24 TABLE 14 Summary of potential hydrology and geohydrology impacts from peat mining in New York State Regional

Increased floodwater flow potential Groundwater elevation modification Modification of surface water flow patterns Increased minimum stream flow rate Increased mean stream flow rate Altered hydrologic budget Altered groundwater aquifer Reduced evapotranspiration

Site-specific

Small scale ~

Large scale ~

Small scale

Large scale

Minor

Moderate

Minor

Major

Minor

Moderate

Minor

Moderate

Minor

Moderate

Minor

Moderate

Minor

Minor

Minor

Minor

Minor

Minor

Minor

Minor

Minor Minor Minor

Minor Minor Minor

Minor Minor Minor

Moderate Moderate Minor

~Small scale = Production rate equals 100,000 dry tons/season, dry mining methods, mine life of 6-19 years. 2Large scale = Production rate equals 300,000 dry tons/season, dry or wet mining methods, mine life of 5-6 years. Source: Newman et al., 1985, pp. 3-96.

tal impacts for each of these issues. While this hypothesis is based on New York State information, it provides the basis for evaluating impacts in other locations. An analysis of the table provided by Newman et al. (1985) is presented below. "Impacts from a small-scale peat mining operation are expected to be minor in magnitude when viewed from a state, regional, and site-specific perspective. The impacts are expected to be minor because of the small bog size in relation to surrounding systems, the greater degree of control afforded by the small project size, and the relative magnitude of the mining operation. On a regional basis, the potential for floodwater, drainage pattern, and/or groundwater elevation impacts are of moderate concern because development of a several-thousand-acre bog can affect surrounding systems up to several miles away if the systems are directly connected. The potential floodwater impact from large-scale peat projects on a site-specific basis can be of major concern because of the increased runoff volume and decreased time until peak flow."

The potential impacts can be mitigated through the establishment of detention basins to simulate the water-detentional function of natural peatlands throughout the site (Edelman et al., 1983).

Water quality impacts The surface waters being discharged from a peatland have characteristic quality parameters that to some degree control the on-site and downstream

25 TABLE 15 Summary of potential water quality impacts from peat mining in New York

Discharge of low pH water Discharge of high BOD/COD Discharge of nutrients Discharge of organic compounds Discharge of colloidal and settleable solids' Discharge of heavy metals Discharge of toxic materials

Regional impacts

Site-specific impacts

Small scale

Large scale

Small scale

Large scale

Moderate Minor Moderate Minor Minor

Major Moderate Major Minor Minor

Major Moderate Major Moderate Moderate

Major Major Major Moderate Major

Minor Minor

Minor Minor

Moderate Minor

Major Moderate

Source: Newman et al., 1985, pp. 3-99.

aquatic habitats and water uses (King et al., 1980 ). Peatland development will necessitate the eventual discharge of water and wastewater from the peat mining and utilization activities. Water-quality issues are listed in decreasing order of importance below (Newman et al., 1985) : (1) Low pH ( 2 ) High biochemical oxygen demand and/or chemical oxygen demand (3) Nutrients (4) Organic compounds (5) Colloidal and settleable solids (6) Trace metals ( 7 ) Carcinogenic toxic metals. Table 15 provides a summary of potential water-quality impacts from peatmining operations. Increases in organic carbon, as expressed by biochemical oxygen demand and chemical oxygen demand, can be expected as a result of dissolution and erosion of peat by rainfall runoff and airborne particulate matter. These elevated organic-carbon levels in surface water will result in increased microbial activity with lower dissolved-oxygen levels (Edelman et al., 1985 ). For water resources, major and moderate impacts may be considered to occur at the site-specific level. Newman et al. (1985) outlined the types of data required to make an impact determination as follows: Water-quantity data requirements Determine site water budget - - Determine subsurface geology - - Collect meteorological data - - Assess on- and off-site flood potential -

-

26 Water-quality data requirements Determine background surface-water and groundwater quality Determine land use within the watershed Characterize existing point-source discharges into receiving waters -

-

-

-

-

-

A number of options are available to the developer to mitigate water-quality impacts. Hazen and Beeson (1979) have outlined the following: B u f f e r z o n e s - - An area left undisturbed and unaffected by the peat mining operation. T h e y are used to control or limit subsurface and surface interchange of waters within the mining area and between the mining area and surrounding environment. p H c o n t r o l - - Natural or artificial methods to control the pH of ponded waters within the affected area. Edelman et al. (1983) also offers mitigation options: S t a b i l i z a t i o n b a s i n s - - Holding basins to retain wastewater with t r e a t m e n t through the action of gravity sedimentation, natural aeration, biological and chemial oxidation, and exposure to sunlight. C o n v e y a n c e f a c i l i t i e s - - Location of new points of water discharge from the affected area to points least likely to impact the receiving body of water. Biological resource impacts

The mining of peat involves the removal of surface vegetation and the control of the hydrologic characteristics of the site. Biological resources will receive the greatest environmental impact. Impacts due to the removal of plant species populations will be significant under the following circumstances (Larson, 1973; Newman et al., 1985) : Threatened, rare, or endangered species inhabit the site. - - An assemblage of unique species occur on the site. These species may be unusual to the region or a combination of rare species. A sufficient number of peat deposits are mined in a region to cause a cumulative impact on more common species. Flora of unusually high visual quality and infrequent occurrence are present. - - The presence of flora or fauna at or very near the limits of their range. Table 16 presents a s u m m a r y of potential biological resource impacts. To determine the ecological importance of the site, base-line information should be determined. N e w m a n et al. (1985) outlines the information required: (1) Composition and abundance of dominant species and acreage of major vegetation communities on-site. (2) Identification and relative abundance of ecologically, recreationally, and economically important fauna that utilize the site. ( 3 Presence of state and federally listed threatened and endangered plant and animal species. ( 4 ) Functional values as a wetland. -

-

-

-

-

-

27 TABLE 16 Summary of potential biologicalresource impacts from peat mining in New York State

Impacts on threatened and endangered species Impacts on fish and other aquatic resources Impacts on vegetation Impacts on wildlife

Regional impacts

Site-specific impacts

Small scale

Large scale

Small scale

Large scale

Major

Major

Major

Major

Minor

Minor

Moderate

Major

Minor Minor

Minor Minor

Moderate Minor

Major Moderate

Source: Newmanet al., 1985, pp. 3-104. (5) Existing stresses on plant or animal populations. ( 6 ) Aquatic resources potentially affected by the project. Site reclamation plans will directly influence the post-mining biological resource base. Wildlife habitat reclamation can be utilized to enhance wildlife use. Reclamation plans for agriculture or silviculture must consider long-term impacts on region. CONCLUSION The various types of peat largely reflect their histories and deposition environments. Their histories and deposition environments in turn largely reflect their composition (chemical makeup and structure), and chemical and structural compositions in turn largely impact suitable end-use applications. Accordingly, all peat types do not serve all end-uses. For this reason, peat research serves to properly correlate peat feedstock with end-use application and to identify required support technologies to do so. Prior to the utilization of peat, however, consideration must be given to the environmental consequences. While a number of mitigation actions are available to the developer, once the resource is mined, the ecosystem cannot be returned to its original state. Disclaimer Reference in this report to any specific commercial product, approach, or service is to facilitate understanding and does not necessarily imply its endorsement or favoring by the United States Department of Energy, the New York State Energy Research and Development Authority, or the State of New York.

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