RECLAMATION OF COAL REFUSE WITH A PAPERMILL SLUDGE AMENDMENT

by

RS. Li and W. Lee Daniels2

~ Reclamation of coal mfuae is difficult due to the harshgrowing conditions resulting

from the refuse’sunfavorable chemical andphysical properties.This researchpm- focused

on the utilization potential of a papermill sludgeproducedby the Mead Paper Company in

K@ksP@ Term., which ~~i~ PritilY of a mi~ of waste wood fiber, lime, kaoliq and

traces of fly ash. A field experiment was initiated in 1992. Loading rateswere O, 112,224 Mg

M-l for the paperrnillsludge and O, 112,224, and336 kg lur’ for N. Our results suggest that th

N-fertilizer additions gave a short-term boost to biomass production suppressed legume gmwtlL

and resulted in a higher yield and thicker vegetation cover in the first year. From the second yea

OILhowever, the vegetation on the papermill sludge plots was superior to that on the Osludge

plots across all N ratea, suggesting that papermill sludge did not lead to excessive Nimmobilization as expected. By contributing organic matter, acid-neutralization potential, and

light color, the paperrnill sludge significantly improved the refuse ~ increased the available P

increased the water holding capacity, and decreased the refuse temperatm during the summeF

all of which were beneficial to establishment and maintenance of vegetation. The addition of

papermill sludge also improved leachate quality. Thus, a proper combination of N-fertilizer and

papermill sludge, for example, 112 kg ha_lN and 112 Mg hd sludge, is recommended in

addition to balanced P and K fertilization.

Additional Key Words: Revegetatiou nitrogen immobilization, acidity, water holding capacity.

The safe disposal of papermill sludge and

other paper making residuals is a challenging problem.

Currently, the majority of wastes are disposed of in

landfills. Nevertheless, these alternatives are becoming

more expensive and pose substantial threats to water

quality ifdeaign standards are not strictly met and

maintained over the lifetime of the disposal fwility.

llms, there is considerable interest in the pulp and

paper industry over whether (and which @ their waste

residurds can be successfully and safely land-applied.

This research program was implemented to determine

ifa paperrnill sludge product could be successfully

utilized to reclaim coal processing waste materials in

southwest Virginia.

lPaper presented at the 1997 National Meeting of the

American Society for Surfke Mining and Reclamation,

Austin, Texas, May 10-15, 1997.

2Ren-sheng Li is a Senior Research Associate and W.

Lee Daniels is Associate Professor in the Dept. of Crop

and Soil Environmental Sciences, Virginia Tech

Blacksburg, VL 240614)404.

Coal refusedisposal areas cover thou

acres in Virginia alone, and tend to be quite d

revegetate or stabilize without topsoil covers o

significant surface amendments. The revegeta

coal refhse is limited by low soil water holding 

high summer heat loads, and variable levels o

acidity (Stewart and Daniels, 1992). The refu

coal preparation is low in organic matter, quit

textured, and is generally characterized by po

physical and chemical properties. On many c

piles, revegetation potential is strongly limited 

potential acidity and resultant low pH and hig

content of the refuse. A number of Appalachi

piles are non-acid forming in ovemll reaction 

but still suffer from the physical limitations to 

growth discussed above, particularly if they a

direct-seeded without topsoil covers.

A considerable amount greenhouse a

research has been conducted to date on the ut

papermill sludge on natural and disturbed lan

studies have shown that appropriate rates of p

sludge as a topical amendment have the poten

greatly improve the water holding and aggreg

raw mine spoils and refuse, supply plant nutr

decrease acidity. These numerous benefits hav

277
better plant growthand greater vegetative cover,

particularlywhen combined with appropriate

fertilization strategies (Owusu-Gyima and Roy, 1991;

Del Roaario, 1990: Feagley et al., 1994alx Bellamy, et

al., 1995; Dollar, et al., 1972; WatsonandHoithdq

1985; Cline and Chong, 1991; Pichtel, et al., 1994).

The specific objectives of this studywere:

1. To characterize the chemical andphysical

properties of a papermill by-product material

that was available for utilization in the central

Appalachian regiom and to determine its

suitability for land application.

2. To determine the optimal loading rates for the

product when used as a surface amendment for

direct revegetation of coal refhse.

3. To measure the amendment’s influence on

coal refuse leachate quality, and to determine

the extent of pH buffering over multiple seasons.

The papermill sludge generated by Mead Paper

Co. in Kingsport (acquired by Willamette Paper in

1995) was particularly attractive for this use since it is

a mixture of primarily waste wood fiber (600A)and lime

(25%), with minor amounts of kaolin clay (10%) and

fly ash (5?40).The material is a non-biological water

tm.atment sludge, is finely groundj and can be easily

land-applied with manure spreadem or through

conventional hydro-seeders. For the balance of this

paper, we will refer to this material as lime-fiber mulch

since that term best describes its properties and

potentially beneficial role in mined land reclamation.

Papermill waste materials can contain dioxins

that are a by-product of the bleaching process. There is

currently considerable public and agency debate over

the environmental and human health risks associated

with dioxins (Olson et al., 1988; Owusu-Gyima and

Roy, 1991; Baker, 1994). Fo-tely, due to process

changes at the Kingsport plant in the early 1990’s,the

dioxin (TCDD) levels in this product were below

detection (< 0.3 ppt) when this research experiment

was installed. However, a considerably less toxic

daughter isomer (TCDF) was detectable at <5 ppt.

Plot cmitrwh

The experimental ~ 45 m by 90 Q was

located on the Pine Branch coal refuse pile operated by

the Westmoreland Coal Company in Wise County,

Virginia. This site was chosen because our earlier

lE@OIUdColdwaste research program (Stewart and

Daniels, 1992) indicated that Pine Branch was close to

the regional median for potential acidity. The area

where this particular experiment was installed was near

neutral in pm however, but was very coarse in texture

and black on the surhce. Noticeable salt accumulations

were also apparent at the time of plot installation. Thus,

while this location is somewhat atypical of Apprdachian

coal refuse with regard to acidity, it still posed a severe

challenge for revegetation due to water stress coupled

with severe N and P limitations. Other studies (lhniels

et al., 1989; Stew@ 1990) at this and other refuse piles

in the region have established that once potential acidity

has been neutralized, N and P are the principal growth

limiting nutrients, and that micro-nutrient deficiencies

are rare.

This experiment was a randomized complete

block design with three replications and two main

experimental factors. The first experimental fhctor was

lime-fiber mulch applied at three rates: O, 112 and 224

Mg ha-l. The second factor evaluated was fertilizer-Nat

four applied levels, O, 112,224 and 336 kg hd as

ammonium nitrate. All plots also received 336 kg ha-l P

and 112 kg ld K with the initial fertilization based

upon earlier research by Daniels et al. (1989). In March,

1992, the area was graded with a bulldozer and the

individual field plots were laid out and sampled for soil

analyses.

In May 1992, lime-fiber mulch from Mead’s

Kingsport plant was trucked to the Pine Branch refhse

pile. A front-end loader was used to measure (by loader

bucket) and spread the lime-fiber mulch at the

appropriate rate on each plot. The weight/density/water

content relationships for this material were determined

in the lab the week before spreading. The lime-fiber

mulch was immediately chisel-plowed to incorporate it

into the refuse surface. On June 9, 1992, the entire area

was seeded with 17 kg hd German millet (Sekwia

itaiica) as a summer cover crop. The appropriate

amounts of fefilizer were applied to each plot just

before seeding. The millet was hamested on September

8, 1992, and these plots were then seeded with the

reclamation species mix are given in Table 1. On April

13, 1993, N-fertilizer was again applied on each plot at

one-half the rate applied in 1992.

278
Table 1. The seed mixture used in 1992.

Variety Purity(%) Ger.(%)

KY-3 1 Tall feseue

Festuca arundinacea Schreber 49.00 85

AmIud ryegrass

Lofium muMjlbrum 9.78 90

Redtop

Agrostis afba 1.96 90

Alsike clover

Trifofiumhybridum 7.91 90

Alta-swede Red clover

Trz~oEitmpratense 9.95 90

Birdsfoot trefoil

Lotim comidatus 1.92 85

Yellow sweetclover

A4efifoti offxinah 17.72 90

To monitor the effkzts of the surfhce

treatments on leaehate quality, zero-tension lysimeters

were installed under fourplots In October, 1992.

Lysimeters wem installed under two treatedplots (224

Mg lid mulch+ 336 kg hd N), andtwo controlplots

(OMg ha-l mulch+ Okg hd N). The lysimeters were

made of a 0.4 m length of smoothbore 0.24 m (diam)

ABS plastic pipe with a fitted endeap. The lysimeter

was plumbed with a plastic tube to evaeuate leaehate.

One endofthetube was fixed tothebottom of

lysimeter and was screened with 80 mesh nylon sieve

clotlL and other end was broughtto the surfhee.A hole

was excavated in the refuse with a shovel (separating

the top layer of- from deeper ret%se)andthe

lysimeter was put into the hole, with a ten-em layer of

coarse sand in the bottom of the lysimeter. Refuse was

then paeked around and in the lysimeter with the top

layer of refuse returned back over the top of the

lysimeter and returned to original grade.

l&XhiWk Leaehates were pumped up monthly fkom

eaeh lysimeter with a vacuum pump. The pH was

measured on-site immediately and subsamplea were

taken into a 250-ml plastic bottle for later laboratmy

analyses. In the laboratory, the turbid samples were

filtered through a #42 filter paper before analysis.

Conductance was measumd with a conductivity meter

and then we acidified these samples with HN03 to

prepare them for fbrther analysis. The leachate

samples were subsequently analyzed for. Al, CILFe, -. -

Iv@ S, ZIL and Caby ICP and/or AA speetroseopy.

Refuse samples

were taken at randomffom the aurfaee 15 em of each

plotbefo~ treatmentswere applied. The mulch was

also sampledbefore application to develop

weight/volume relationships as discussed earlier.

Vegetation performancewas evaluatedfor eaeh plot by

estimating the percentage groundcover, the species

composition andthe vigor of growth each spring,

summer, andfhll. 13aehfhll in September,standing

biomass samples were takenfrom eaeh plot randomly

by handclipping to groundlevel within two 0.25 mz

quadrata.The plant tissue was oven-dried at 65°C for

48 hours and weighed. The plant tissue was

subsequentlygroundto determine nutrient and heavy

metallevels. Soil samples were excavatedbeneath the

biomass sampling quadratsto a 15-em depth with a

shovel. Soil samples wem air-driedand passed through

a 2-mm sieve to separatefine soil ilom coarse

fragments. All analyses wereperformedon the

fine-soil fkaetion.Soil samples were analyzed for pm

water retentio%and heavy metals. Soil pH was

determinedin a 1:1 soil:water slurrywith a

glass-calomel electrodepH meter (McLemL1982).

Water retention was determined by the method of

Klute (1982). Total analysis of the original lime-fiber

mulch material and a combined sample of the

untreated refuse was determined by ICP and AA

spectroscopy after high temperature HF digestion

279
(Hmtstein et al., 1973). The Neutralization potential of

the lime-fiber mulch material was estimated by

treating the sample with an excess of HC1followed by

back titration with NaOH (Sobek et al., 1978). Total N

was measured calorimetrically after KjelW

digestion (Bremner and Muhmney, 1982). Plant

available P was analyzed with 0.5M NaHCOj method

(Olsen and Sommers, 1982). Total P was determined

with the perchloric acid digestion method (Olsen and

Sommers, 1982).

Physical and chemical conditions of the soil

are critical for vegetation grow@ and the reclamation

of coal refbse generally is not successfd without

topsoiling or heavy use of amendments. For

comparative purposes, the total elemental content of

the lime-fiber mulch material and the raw refuse from

Pine Bmnch are given in Table 2. The mulch material

as applied was 29°AC and very high in Ca derived

from its waste lime content which led to a high

neutralization potential (197 tons linwlthousand tons

material). The Pine Branch refbse averages around

19% C due to its carbonaceous nature (Stew@ 1990).

Previous studies have shown that heavy metal

bioaccumulation is generally not a problem for

applications of papermill sludge because of the low

concentrations applied and the lack of uptake or toxic

effects in sensitive crops like tomatoes, cucumbers and

peppers (Ritter et al., 1992; Cline and Chong, 1991;

and Bellamy et al., 1995). In general, the lime-fiber

mulch material applied at Pine Branch was similar to

or lower than the host refhse in heavy metals and

should pose no long term heavy metal loading

concerns, particularly when the pH buffering of the

lime component is taken into account. Thus, this waste

Ptiuct appeWsveryattractive as a mine soil

amendment particularly for acid-forming materials. In

one application%wood fiber residues are added to work

as a surf’ mulching agent and organic matter

amendmen4 lime is added to neutralize acidity and

buffer soil solution pm and a smaller amount of clay

and ash are added to aid with water retention and to

slow the rate of water percolation down away from the

rooting zone.

Lab analyses indicated that addition of limefiber mulch not only increased and stabilized the soil

pELbut also increased the available P levels in the soil

(Figs. 1 and 2). This portionof the Pine Branch refuse

pile was moderate in pH before the plots were

establish perhaps due to earlier lime additions by

the company. In 1992, the pH of the refuse was

around 6.5 with a large amount of point to point

variation. Lime fiber mulch additions increased pH to

7.0 to 7.8, but by 1993, the pH of refuse from control

plots had decreased somewhat most likely due to

oxidation of trace pyrites due to incorporation

disturbance.

It appeared that due to its high neutralization

potential, the lime-fiber material neutralized acidity

and/or inhibited the pyrite oxidatiorL and reduced the

volubility of Fe (Backes et al., 1986). Pichtel and Dick

(1991) report that organic materials can serve as

inhibitors to reduce acid production from pyrite by

preventing Fe-oxidation and by removing soluble Fe

from solution. The effects of Liming and inhibition

probably worked together by raising soil pH and

reducing Fe and Al levels. This combined effect should

also increase the availability of P, since at low pH, P is

immobilized mainly by Fe and Al (see discussion of

soil leachate properties). The average extractable P

increased (p< 0.05) from 4.9 to 21.3 mg kgi with

addition of lime-fiber mulch.

Adverse soil water conditions including

seasonal waterlogging and drought are common

problems during reclamation (Rimmer, 1982). Our

monthly field observations indicated that waterlogging

and runoff occurred only on the untreated refhse plots

in the winter and after heavy storm events in summer.

In contrast, there was no waterlogging and/or runoff

observed on the lime-fiber mulch plots due to

improved infiltration and water holding capacity

(WHC). Without lime-fiber mulch the average WHC

was 87 g kg-l; with treatment it increased to 175 and

230 g kg-l with the addition of 112 and 224 Mg M’

lime-fiber mulck respwtively (Fig. 3). Figure 4

indicates that the increase in WHC occurred mostly in

the low tension portion (or readily available) of the

curve.

The surface temperature of bare coal waste is

very high in the summer, reaching as high as 75°C

(Deely and Borden, 1973; Lee et al., 1975), a level

lethal to plants. Our field measurements indicate that

the lime-fiber mulch effectively moderated the surface

temperature (Fig.5, p < 0.05). This temperature

buffering is most likely due to the combined effects of

direct mulching, improved vegetative cover, soil

albedo effkxts(lighter), and improved soil WHC.

280
Table 2, Elemental analysis of coal refuse and lime-fiber mulch materials.

Sample Neutralizationpotential To~ N% To~ PA c% Si% A1’?40 Fe% CaYO

refhae ------------------ 0.27 0.016 19.0 22.2 9.1 3.0 2.3

sludge 197tonslime(1000tijl 0.14 0.030 29.2 9.5 5.0 2.6 7.9

Sample Mg?? % c% ~ PbP N% CrW c%

0.8 112.0 26.0 1026 15.8 29.8 83.8 6.4

sludge 0.3 98.7 47.3 1213 24.0 33.7 103.4 2.5

8.0

7.!5

x

Q 7>0

6.5

6.0

NOMON, ~ N2M0N3M0 NOM,

1- 1-

,M, N2M1 N3M1NOM2N1M2N2M2 N3M2

Figure 1. Soil pH in 1992 and 1993. No: no N fertilizer; Nl: 112kg N ha-l; N2: 224kg N ha-l; N3: 336kg N

ha-l; Ma: no .&-& ~~ch; M<: 112 Mg ha-l sludge m~ch; Mm:224 Mg ha-l sludge mulch; SOilsamples

taken on”March 1992, and on At. 1993 before and after applic~tion of papermill sludge. Values are means

(n= 3) with standard errors.

281
30

25

5

0

Treatment

Figure 2. Available P in 1993. Sludge:Lime-fibersludge; NO:no N fertilize~ Nl: 112kgN ha-l; N2: 224k

N ha-l; N3: 336kg N ha-l; M : no sludgemulch; Ml: 112Mg ha-l sludgemulch; M2: 224 Mg ha-l sludge

mulch; Sod samplestaken on &t. 1993, and values are means(n=3)withstandard errors.

0.30

0.25

0.05

0.00

N M NM NM N M N M N, M, N2M1N3M, NOM2N,M2N2M2N3M2 ooio 203004

Treatment

Figure 3. Soil water holding capacities(-O.OIMpa to -1.5Mpa)in 1993. N : no N fertilizer; N : 112kgN ha

N2: 224kg N ha-l; N3: 336kg N ha-l; MO:no sludgemulch; Ml: 112 Mg #a-l sludge mulch; I/f2:224 Mg

ha-l sludgemulch. Soil samplestaken on Oct.1993, and values are means(n = 3) with standard errors.

282
f

:

:

0 NOMO 4 0 N2M0

T N2M1

o N2M2

.................................

0.0 1

0.0 0.5 1.0 1.5

saturation wilting

(-O.OIMpa) Soil water potential (Mpa) (-1.5Mpa)

Figure 4. Soil moisture potential curves for samples taken in 1993. N : no N fertilizer; N : 112kg N ha-l;

N2: 224kg N ha-l; N3: 336kg N ha-l; MO:no sludge mulch; Ml: 112&g ha-l sludge mulck; M2: 224 Mg

ha-l sludge mulclq

32

I

30

] -T ~ depth: 2.5cm

~ depth: 10cm

20

18

Treatment

Figure 5. Effkets of treatment on soil temperature. NO:no N fertilizer; N1: 112kg N ha-l; N2: 224kg N ha-l;

N3:336kg N ha-l; MO:no sludge mulch; Ml: 112 Mg ha-l sludge mulch; M2: 224 Mg ha-l sludge mulch;

Temperatures measured on Aug. 18, 1994, and values are means (n = 3) with standard errors.

283
Biomass yield and overallplantperformance

are the most commonly employed indicators of

revegetation success. Total standingbiomass yields in

the fall of 1992, 1993 and 1994 are shown in Fig. 6. In

1992, standing yields were determinedon the German

millet cover croponly. In 1992, there were signitlcant

effects due to N-fertilizer rate, but no differences

among mulch treatments. Millet is known to have a

strong N-fertilizer response, and both the raw

lime-fiber mulch and the raw refuse are quite Ndeficient. Thus, in 1992, the millet biomass

accumulation appeared to be driven primarily by

fertilily with no obvious effkct from the mulching

treatment, In f- the mulched treatments appeared to

be less vigorous than the ummdched plots. We

attribute this to (1) the fact that the millet is adapted to

hot summer conditions, (2) our relatively late spring

seeding date, and (3) that the wet summer of 1992 may

have negated any positive mulching effects.

The mixed gradlegume stand was

established in the fall of 1992, and by the fall of 1993

it had established a vigorous and nearly complete cover

over the better performing treatments. Both N and

mulch application rates influenced (p=O.01) yields in

1993 (Fig. 6), and worked well in combimtion.

Variation of biomass productionwithin each treatment

was less in 1993 than that in 1992 andthe total

vegetative production was consistently improvedby

mulch and moderate N application. The applicationof

lime-fiber mulch increasedoverall plant cover across

all N ratesin 1993 (Fig. 7), and provided almost

complete vegetative cover when combined with

moderate N rates. Increasing the mulch rate from 112

to 224 Mg ha-l did not appear to improve vegetation

performance, however. The composition of the

vegetation varied (p< 0.05) in response to N rate

across all mulch treatments. In general, the higher the

N application the less the legume component and the

greater the grass component (Fig. 7). Nitrogen

fertilizer applications clearly increased the total

vegetative cover but had the tendency to suppress

legume grow@ which is a commonly observed

phenomenon in mixed stands.

Increasing the fertilizer beyond 112 kg ha_]

did not appear to improve total biomass production.

This indicates that the application of lime-fiber mulch

material does not lead to excessive N-fertilizer

immobilization by soil microbial decompose as we

had feared. Apparently, the C substrate within the

mulch is either extremely resistant to microbial attack

or has already been significantly degraded in the wate

treatment process at the mill. Regardless of the reason

it does not appear that heavy N applications will be

Mcessa@ for this product to be successfully utilized in

mine reclamation.

The overall evaluation of vegetative cover

shown in Figure 7 was made in October 1993,

integrates both total ground cover and plant vigor, and

therefore varies somewhat from the percent cover

evaluation for each treatment. Based on the overall

evaluation data it is clear that the NW (no N, no

mulch) plot performance was poor (grade <2. 5); while

the NIIv$(112 kg ha-l N, no mulch) and the N&41(no

N, 112 Mg ha_*mulch) resulted in fair vegetation

performance with grades of 3.3 and 2.7, respectively.

Treatments that combined lime-fiber mulch and N

fertilizer generated thick and vigorous vegetation (Fig

7), reinforcing our finding that a combimtion of the

lime-fiber mulch and N fertilizer appears to be a very

successful treatment for direct seeding of this coarse

coal refbse material. The data in Figure 7 also indicate

that the ratio of legume/grass can be regulated by the

rate of N fertilizer, particularly when the lime-fiber

mulch is utilized. This effixt was particularly

pronounced in the highest mulch rate treatments.

Apparently, increasing N-fertilizer in this situation

decreases the competitive advantage held by the

N-iIxing legume and leads to a higher gradlegume

ratio in the mixed stand.

The yield data from 1994 indicate that the N

treatment effect became some negative, and only the

lime-fiber mulch effect continued ~ be positive and

significant (Fig. 8, p < 0.01). We also detected a trend

of lower 1994 yields with increasing N fertilizer

applied. As discussed earlier, N-fefizer had the

tendency to depress legume community establishment

therefore, the legume component clearly decnased

with increasing N rate (Figs. 7 and 8). In a short

period of time, the N fkom the original fertilization is

lost through leaching, uptake, gaseous loss, etc..

Subsequently, those plots which lack the N-fixation

capability of the legumes, become Ndeficient for gras

production and hence their lower yields over time.

The overall plant performance respond

patterns varied behveen 1993 and 1994. In 1993, there

were three performance peaks that corresponded to the

high rate of N across the three high lime-fiber mulch

rates (Fig. 7). This pattern indicated that both the N

fertilizer and lime-fiber mulch were playing an

important role in vegetation performance. However, i

1994, the performance appeared as a stair-step

284
‘18000

10000

n

y

2 8000

2000

0 k

N3M2

Treatment

Figure 6. Biomass yield as influenced by lime fiber mulch and N application. N : no N fertilizer N : 112kg N

~-l; N : 224kg N ~-l; N : 33&g N ha-l; M : no sludge mulch; Ml: 112 Mg%a-1 sludge mulch; hz: 224

Mg ha-~sludge mulch; val~es are means (n = 35 with standard errors.

40

20

0

Ilii3 Total cover% ,0..- 0 .X2

t

5

Lqmw% ,p-.--a .- -Q t ---e -- -. )

Treatment

Figure 7. Vegetation cover% and performance evaluation in 1993. N : no N fertilizer; N : 112kg N ha-l;

N2: 224kg N ha-l; N3: 336kg N ha-l; MO:no sludge mulch; Ml: 112 ~g ha-l sludge mulck; M2: 224 Mg

ha-l sludge mulch. *2: POOL 3: fti, 4: good; 5: exeellent. Field survey of vegetation on Oct. 5,1993,

and values are means (n=3) with standard errors shown.

285
40

20

0

5

4

al

0

%

SE

e

:

2

NOMO NtMo N2Mo N3Mo NOM, N1M1N2MI N3M1 NOM2N1M2 N2M2 N3M2 1

Treatment

Figure 8. vegetation cover YOand performance evaluation in 1994. N.: no N fertilizay N.: 112kg N ha-l;

N2: 224kg N ha-l; N3: 336kg N ha-l; MO:no sludge mulch;

ha-l sludge mulch. *2: poor; 3: faiq 4: good; 5: excellent.

and values are means (n=3) with standard errors shown.

pattern. The overall performance increasedstrongly

with increasing mulch rate,indicating that the mulch

contributedthe majorityof the positive impact on

vegetation performance.It was notable that the higher

rate of N appmred to have a negative effect on

performanceto some extent (Fig. 8). The vegetation

performance in the group with no lime-fiber mulch

(NM, N1~, Nz~, and N$Q was poor, andhadan

average grade of 2.2. The vegetation for the N~l

- (112 I@ id lime-fiber mulch) performedwell

and its average grade was 3.9. The NM groupas a

whole (224 Mg ha-llime-fiber mulch) exhibited

excellent vegetation performance with a grade of 4.9.

During the three years of this study (1992-

1994), the yields increased over time on the plots with

Oor low rates of N fertilizer application across all

lime-fiber mulch treatments (Fig. 6; see plots of NW,

N]Iv& N&fl, NIM1, NW, N1~). Simultaneously, the

yields were decreasing on plots receiving high rates of

N fertilizer and no lime-fiber mulch (Groups of NJ%,

NM). This result is consistent with other studies that

have shown that a single application of N can have a

major et%ct on the initial growth of non-leguminous

vegetation but little effect on establishment of a selfM1: 11] Mg ha-l sludge mtdch; M2: 224 Mg

Field survey of vegetation on Oct. 21, 1994,

sustaining grass cover on coal waste (Davison and

JefFerie$ 1%6; Bloomfield et al., 1982). There was no

doubtthat lime-fiber mulch improvedboth physical

and chemical properties of coal refbse, supplied a

better condition for plant grcm@ and led to more

vigorous vegetation growth and associated higher

yields over multiple seasons.

The leachate data from the lysimeters at Pine

Branch suggested that with lime-fiber mulch

application the pH of the leachates were relatively

stable. The pH varied from 6.5 to 7.2 with an average

of 7.2, well within the range suitable for vegetative

growth (Table 3) and minimal heavy metal volubility.

In cent.n@ without lime-fiber mulch applicatio~ The

pH of leachates was lower (5.9) with greater variation

(4.5 to 6.9). As mentioned earlier, the levels of soluble

Fe, Al were controlled by p~ which in turn

determined the level of available P. Lime-fiber mulch

treatment reduced the concentration of heavy metal in

leachate (Table 3); Mn, Zn and Cu levels were lower

and more stable than untreated controls. The

improvement in leachate metal content presumably

286
Table 3. Average leachate properties under control and lime-fiber mulch plots

fiwmDecember, 1992 to July, 1994 (n=20) .

Treatment Mean STD Error Miximum Maximum

OMg ha-*Mulch 5.88 0.11 4.46 6.90

pH

224 Mg ha-l Mulch 7.23 0.06 6.53 7.59

0 Mg ha”lMulch 0.09 0.09 0.04

EC(S m“’)

0.16

224 Mg ha”’Mulch 0.08 0.01 0.04 0.14

0 Mg ha-i Mulch 1.41 0.50 0.02 8.05

Fe(mg ~’)

224 Mg ha-lMulch 0.08 0.02 0.02 0.48

0 Mg ha-’Mulch 6.64 3.99 0.00 75.94

Al(mg ~’)

224 Mg ha-i Mulch 0.11 0.02 0.00 0.34

0 Mg ha-*Mulch 1.12 0.51 0.05 9.80

Mn(mg ~’)

224 Mg ha-*Mulch 0.09 0.04 0.00 0.55

0 Mg ha”lMulch 0.47 0.27 0.00 5.19

Zn(mg ~’)

224 Mg ha-l Mulch 0.04 0.02 0.00 0.48

0 Mg ha-]Mulch 0.07 0.05 0.00 1.00

Cu(mg ~1)

224 Mg ha-lMulch 0.01 0.00 0.00 0.04

0 Mg ha-l Mulch 190.61 27.03 49.26 471.75

Ca(mgl-’)

224 Mg ha-’Mulch 203.24 22.33 89.07 438.50

0 Mg ha-’Mulch 210.99 43.58 49.33 861.70

S(mg k’)

224 Mg ha-iMulch 144.54 25.93 20.33 452.70

287
would benefit deeper waterquality in the reiise pile,

but the overall eiTeetof this surficial treatment on net

pile discharge desewes further study.

The specific conductance of soil leachates is

proportional to ionic strength, and is increased

dramatically by pyrite oxi&tion products. Conductance

values may also increase due to lime and fertilizer

dissolution products. Inmost cases, the EC of leachates

obswved under the lime-fiber mulch was lower than

that of control overtime due to the buffering action of

the lime-fiber mulch material (Table 3). The Ca levels

in leachates varied from 50 to 370 mg 11(Fig. 9),

while other cations ranged from O-16 mg 11for

control and O-0.5 mg 1-1for the lime-fiber mulch

treatment (’Table3), respectively. Taken together with

Table 3, these data indicate that Ca was the dominant

cation in leachates. The solution sulfate (S) levels

under lime-fiber mulch deemased with time, and were

generally lower than that of controls (Fig. 9). Over

time, the S levels for both control and mulch

treatments varied between 50 and 400 mg 11,which

was similar to that of Ca. The Ca and S rose and fell

along with each other (Fig. 9); correlation coefficients

(r) betsveen S and C!awere 0.96 for both control and

lime-fiber mulch, indicating that they are controlled b

a emrunon solid phase mineral, most likely a complex

gypsum salt (Stewart and Daniels, 1992).

4oo - A P

/

‘;\ L

P’ “i,--0-- Sat oontrol plot

f

A

5, A ;4 ,

I —.—s at 224 Mg ha-l plot

● ,4 R‘1 It \

A ‘t

At!!

--A- - Ca at oontrol plot

ft ‘~ ‘I _A— Ca at 224 Mg ha-l Plot \

‘,+

2s0 ‘$,,

L \\

m200

‘ Tyjy(\

%t

E

1$$$\*

160

\

\

\ “

; h“

A-&:$\

100-

/d .A\ A t4 ●

qs%.i ‘“

\

“*;Q

so- -~+

~ %24/92

I I I I I I I

Z24193 5/24/93 3124193 11/2493 2/24/94 5/24/94 3/24/94

Date

Figure 9. Leachate Ca and S in immediate surface (0.45m in depth) from January 8,1992 to July 21, 1994.

288
Application of N-fertilizer in combination

with lime-fiber mulch can greatly improve the

establishment and growth of vegetation when it is

di~-seeded onto coal refuse. Nitrogen fertilizer alone

improved millet establishment and gave a short-term

boost to biomass production but lime-fiber

applications led to even higher biomass production by

btiering the soil pH and improving soil physical

conditions over the long term. The combination of Nfertilizer and lime-fiber mulch resulted in the highest

mixed stand vegetative cover and production in 1993,

and the ratio of grass to legume was regulated by the

rate of N fertilizer. The combined mulch and fertilizer

treatments produced ground covers greater than 90’%

at the end of the second growing season. During the

third growing season (1994), there was a positive effect

from lime-fiber mulch coupled with a significant

negative effkct of the high N-rate on vegetation due to

the suppression of legumes in earlier years.

Application of lime-fiber mulch onto coal

rei%seis not only beneficial to revegetation objectives,

but appears to improve leachate quality as well. With

the application of lime-fiber mulch the leachates were

higher in pH and lower in toxic metals, which could

reduce the chance of groundwater contamination with

heavy metals and moderate the impact of discharged

waters on the environment. Surface treatment of an

entire pile with a reasonable loading rate of this

product could efk?ctively charge all waters percolating

through the pile surface with alkahnity. Whether or

not this would have any significant impact on

whole-pile discharge water quality deserves fhrther

study.

In ~j the lime-fiber mulch material

appears to have outstanding potential as a soil

amendment for coal refuse in the ctntral

Appalachians. Due to ita lime content we ako

presume that this product would have great utility in

treating acid-forming materials as well. From both a

short and a long-term perspective, a proper

combination of N fertilizer (112 kg IM-*)with

lime-fiber mulch (112 Mg hd) is recommended for

the reclamation of coal refuse materials.

This has been a cooperative effort among

Virginia Tech Mead Paper Company, and the Powell

River Project. In particular, we appreciate the field

assistance of Ken Roddenberry and Steve Sutphin of

Westmoreland Coal Company, Dave Bryer of Mead

Paper, and Ron Ails and Bany Stewart from Virginia

Tech. In 1995, the Mead Kingsport papermill fhcility

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