United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
 Research and Development
EPA-600/S2-80-199  Mar. 1981
Project  Summary
Production  of  Non-Food-Chain
Crops  with  Sewage Sludge

Lilia A. Abron-Robinson, Cecil Lue-Hing, Edward J. Martin, and David W. Lake
  A beneficial use for sewage sludge?
This study investigated the feasibility
of using sewage sludge in cultivating
three non-food-chain crops currently
sold on the open market or with good
potential for marketability. A  cost
analysis determined how cultivation
costs using sewage sludge compared
with costs using commercial fertilizer.
  Cotton,  sod,  and energy  biomass
trees were determined to have the
best potential  for cultivation  using
sewage  sludge, based on the market
values and nutrient requirements for
each crop and  on the hectares pres-
ently under cultivation for production
of these crops.
  Results indicate that large quanti-
ties of sewage sludge can be used,
based solely on the  nitrogen and
phosphorus requirements for the cul-
tivation  of these crops.  In addition,
although the total costs  for fertiliza-
tion using commercial fertilizer are
less than the costs for using sewage
sludge,  the latter would be viewed
more  favorably if the municipality
generating the sludge bore the costs.
  This Project Summary was devel-
oped by EPA's Municipal Environ-
mental Research Laboratory, Cincin-
nati. OH 45268. to announce key
findings of the research project that is
fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
  Sewage sludge has historically been
viewed as a spent by-product of sewage
treatment. Recognition of the valuable
properties of sludge, including its high
concentrations of plant nutrients and
organic matter, has led to increasing
emphasis on its beneficial uses for re-
claiming disturbed lands and fertilizing
agricultural soils. The prospect of wide-
spread application on agricultural land
has,  however, been accompanied by
concern over possible accumulations of
toxic substances in  soils and  potential
translocation of toxics throughout the
human food chain.
  The purpose  of this study was to
evaluate the feasibility and market
potential of land application of munic-
ipal sewage sludge in the cultivation of
non-food-chain  crops (NFCC).  Using
sludge in this manner would realize the
advantages of its beneficial properties
while circumventing the potential prob-
lems associated with  the  unknown
impacts of toxic materials on the human
food  chain. This study entailed three
broad activities: (1) assessing the fertil-
izer value of sludge, (2) selecting NFCC
amenable to cultivation using sewage
sludge,  and (3) determining  land re-
quirements and costs associated with
producing NFCC using sludge and com-
paring these costs to the costs of pro-
ducing the same crops using commer-
cial fertilizer. The analyses were based
on data  available in the literature or
obtained through personal interviews.

Fertilizer Value of Sludge
  The nutrient  content  of municipal
sewage sludge was  found to vary with
the composition of the influent waste-
water and the sewage and sludge treat-

-------
ment processes employed. Municipal
sludges were found to have a total
nitrogen (N) content of 1 % to 6%, a phos-
phorus (P) content of 1% to 6%, and a
potassium (K) content of 0.04% to 6.1 %.
Because of  its low potassium  levels,
sludge is generally not considered to be
a good source of this nutrient.
  Based on  mean sludge  N, P, and K
values of 3.2%, 1.8%, and 0.3%, respec-
tively; on inorganic, N, P, and K prices of
$0.253/kg  ($0.115/lb),  $1.37/kg
($0.621/lb),   and   $0.259/kg
($0.1176/lb); and on a projected 1985
U.S. sludge  production rate of 16,012
dry  metric  tons/day  (17,650  dry
tons/day),   the   total   daily  sludge
produced in the United  States has an
estimated chemical fertilizer equivalent
market value of $537,000 per day for
the year 1985 (based on 1980 dollars).
Other benefits of using sewage sludge,
such as improvements in tilth and water
holding capacity of soils, are difficult to
quantify. It is crucial also to  consider
that using sewage sludge in place of or
as a supplement  to chemical  fertilizer
avoids or reduces the high energy costs
associated with both commercial fertil-
izer production and sludge incineration.

NFCC Amenable to Sewage-
Sludge Cultivation
  The next step was to  identify NFCC
and  determine which   of these  are
amenable to cultivation  using sewage
sludge. Food-chain crops are defined as
(1) tobacco; (2) crops grown for human
consumption; and (3) pasture, forage,
and feed grain for animals whose prod-
ucts are consumed  by humans. NFCC
are, therefore, the crops that remain.
These crops were first identified using
the Standard Industrial  Code  (SIC), to
which were added research crops such
as jojoba, euphorbia, guayule,  and bio-
mass crops. Cotton and soybeans were
also included because these crops have
significant inedible uses, both  respond
favorably to  commercial fertilization,
and cotton clearly has a high N demand.
  The selection  of  NFCC  feasible for
cultivation using  sewage sludge was
based on a developed set of criteria. The
most important of these criteria were:
(1) the crop must not produce edible
matter that could easily become a part of
man's food chain; (2) the crop must have
a demonstrated or a high probability of
future  market potential; (3)  the land
used to raise the crop must have a high
probability of being  continuously used
exclusively for production of that crop;
and (4) data must be available giving the
response of the crop to sludge, or suffi-
cient data must be available for similar
crops,  to enable a probable response
determination  using data extrapolation
and inference.
  Six crop categories composed of 20
crops were studied in  relation to the
above criteria: timber tracts (five hard-
wood and  three softwood varieties);
forest  nurseries;  flax;  horticultural
specialties  (greenhouse  varieties,
shrubs, sod  and  turf  grasses,  lawn
grasses); research  crops  (jojoba,
guayule,  euphorbia,  energy  biomass
crops); and oil crops (cotton, soybeans).
Using sludge for cultivating hardwood
forests   was  deemed  unacceptable
because  hardwoods are best grown in
the open forest  environment.  These
sites are generally remote from sludge
generating centers and are only inter-
mittently accessible;  also, the impacts
of  sludge   on  the   open  forest
environment  are  poorly  understood.
Furthermore, hardwoods have a slow
rotation  period  and low  N  and  P
requirements.  Flax  was  deleted
because  the  market for this crop  is
declining and  a reasonable possibility
exists that land used to raise this crop
could be used to grow food-chain-crops.
Of the research crops, all were rejected
except  biomass  crops because  not
enough data  were available to  deter-
mine feasibility.
  Based  on the above  criteria, crops
retained  for  further study  included
monoculture  timber tract  operations
using softwood, forest  nurseries,  sod,
and energy biomass  trees,  and  cotton
and soybeans. Of these, cotton, sod, and
biomass trees were selected for detailed
case study analysis. These three crops
are currently sold on the open market or,
in the case of biomass crops, are being
actively researched. Thus, information
was readily  available  describing the
preferential  climatic  condition for the
crop, nutrient requirements of the crop,
land required, and minimum size of a
city that could generate enough sludge
to support crop production.
Land Requirements and Costs
  Given  both the  sludge  quantities
generated and the land currently under
harvest for each crop in each state, the
following  were  determined: (1)  the
maximum amount of land that could be
fertilized  for each crop in  each state,
constrained  by  either the amount of
sludge generated in that state or by the|
land currently  harvested; (2) the unitf
costs (excluding  land  costs) of using
sludge to fertilize this  land (by three
application  modes—injection,  surface
irrigation, truck spreading); and (3) the
unit costs of fertilizing this land using
custom application of commercial fertil-
izer. Application  rates  of sludge and
commercial fertilizer were calculated in
two different ways: rates needed to
satisfy crop nitrogen requirements and
rates needed to satisfy crop phosphorus
requirements.  Aqueous   ammonia
containing  30% NHa was used as the
basic source of commercial  N; phos-
phorus pentoxide containing 40% P was
used as the basic source of commercial
P. The current cost of commercial fertil-
izer was determined from the chemical
marketing  literature, and the costs of
transport and custom application were
based on  information from companies
providing these services. The cost of the
sludge itself was taken as zero, and the
sludge transportation  costs from the
centers of sludge  generation  to the
application   sites  were   considered
separately.

Conclusions and
Recommendations              |
  The cost comparisons for  sludge and
commercial fertilizer are compared in
Table 1 . Of the three sludge application
modes, injection is the  most expensive
and truck spreading appears to be the
cheapest. Using sludge in lieu of com-
mercial fertilizer appears to be most cost
effective  when  applying  sludge  to
biomass crops via truck spreading and
surface  irrigation at rates sufficient to
satisfy  nitrogen  requirements.
Research on  the  use  of sewage  as a
substitute for commercial fertilizers for
the production of biomass crops should
be encouraged.
  Using sludge for sod production is the
most  feasible  beneficial sludge  use
option  at  this  time.  Sod  production
would conservatively use 5% to 10% of
the total sludge generated  in the sod
producing states. As stated  previously,
biomass crops are still  in the research
stage.  Although  most  of the  cotton
being produced  is used  in part for food-
chain products, the possibility does exist
whereby a portion of this crop could be
grown  for  non-food-chain  purposes
only.
  It became evident from the case study
analysis of the three crops that all of the *
sewage sludge generated  cannot be|

-------
Table  1.    Cost Comparisons for Sludge Versus Commercial Fertilizer (Fertilizer Costs Include Both N and P)
                                       Cotton
                          Average Total Annual Cost ($/ha)

                                            Sod
                                                              Biomass
Application Mode
 N(S)
P(S)  Fertilizer'      NfSJ      P(S)   Fertilizer'     NfS)
           P(SJ   Fertilizer"
Injection

Surface
Irrigation

Truck Spreading
1,229     1,034       290      1,364      1,156


  709     1,127       290       660      1,048

  296       290       290       704       336
                                          350     1,197
                                          350

                                          350
255

417
746


361

338
432


432

432
 'All fertilizer costs are custom application.
 used to produce NFCC. Based only on
 the crops analyzed in this study, how-
 ever, at least 20% of the sludge gener-
 ated could be used for NFCC production.
 This  is  significant.  The  problem of
 generating  more  sludge  than  that
 required  for application raises other
 concerns  such  as the need for storage
 facilities and the need for other benefi-
 cial  sludge  use options. These needs
 should  be addressed  if the  eventual
 objective is to use and recycle sludge to
 the greatest extent possible.
  Transportation costs from the centers
 of sludge generation to the application
 site  will have a significant impact on
 cost. When transport costs are added to
 the costs  presented in Table 1, the dif-
 ference between costs  for sludge  and
 commercial fertilizer become even more
 pronounced. Clearly, if sewage sludge is
 to compete with commercial  products,
 the costs  for the operation will have to
 be borne by the municipality generating
 the sludge. If the municipality were to
 transport  the sludge to  the application
 site  and provide the  application equip-
 ment, the sludge would be a sought-
 after commodity.
                Lilia A. Abron-Ftobinson and Cecil Lue-Hing are with PEER Consultants, Inc.,
                  Rockville. MD 20852; Edward J. Martin and David W. Lake are with Environ-
                  mental Quality Systems, Inc., Rockville, MD 20852.
                Gerald Stern is the EPA Project Officer (see below).
                The complete report, entitled "Production of Non-Food-Chain Crops  with
                  Sewage Sludge," (Order No. PB 81-125296; Cost$11.OO, subject to change)
                  will be available only from:
                        National Technical Information Service
                        5285 Port Royal Road
                        Springfield, VA 22161
                        Telephone: 703-487-4650
                The EPA Project Officer can be contacted at:
                        Municipal Environmental Research Laboratory
                        U. S. Environmental Protection Agency
                        Cincinnati, OH 45268
                                                                                        « U.S.QOVERMMBIT PRINTING OFFKC:1M1-757-Ol2/70l7

-------
 Unit»— •"*-—                      Center for Environmental Research                                       Postage and
 _                                                                                            r-ees raia
 "j                                                                                            Environmental
  90              UNITED STATES                                                                 Protection

       ENVIRONMENTAL PROTECTION AGENCY                                                        &MB
	           Cincinnati, Ohio 45268                                            	

 Offi           ~~~~~~~~~~~~~~~
 Pa,.              OFFICIAL BUSINESS
            PENALTY FOR PRIVATE USE $300
           AN EQUAL OPPORTUNITY EMPLOYER
                           Region 5 Library
                           2D3o%En£:rrs
                           Chicago,  IL   60604
      EPA-353(Cin) (Rev. 11-80)

-------