To explore the reduction of fossil fuel use in its Sunshine Farm
Project during 1991-2001, The Land Institute conducted energy
accounting of its 85-ha organic farm powered by commercial biodiesel,
draft horses, and a photovoltaic array. Legume crops provided nitrogen,
and no nutrients were imported except some purchased feed amounting to
only a few kg/ha of elemental nutrients annually. Three-fourths of the
consumed animal feed was produced on the Sunshine Farm for a team of
draft horses, beef cattle, and poultry. The proportion of cropland area
planted in legumes was 40%, of which one-fourth was green manure, and
the other three-fourths were also devoted to feed, marketed products,
and oil for biodiesel. About 34 and 26% of the cropland was devoted to
feed and marketed products, respectively. Based on published process
energy values for farm inputs, the Sunshine Farm could meet 90% of the
embodied energy in its yearly inputs through leguminous nitrogen
fixation, animal feed, oilseeds for biodiesel, and electricity from its
array. If the embodied energy in amortized capital such as farm
equipment, vehicles, physical facilities, and the photovoltaic array is
included with the yearly inputs, then half of the overall embodied
energy was provided by the farm. On a net energy basis including
oilseed production, processing, and meal cake credit, 30% of the
cropland area was devoted to soybeans and sunflowers for biodiesel fuel
that could be commercially produced to power the field operations and
off-farm transportation. The ratio of gross energy content in marketed
products to embodied energy in purchased inputs and capital was 2.4.
Inclusion of lifestyle support energy for average American rural labor
dropped this ratio to 1.5, and for austere Amish labor, 2.0.
Presented at the Third Biennial International Workshop, Advances in
Energy Studies: Reconsidering the Importance of Energy, Porto Venere,
Italy, 24-28 September 2002 (proceedings in press).
The tables for this article have been converted to a .PDF file. Click here to download the tables to view while reading the article.
Martin H. Bender, The Land Institute,
2440 E. Water Well Road, Salina, KS 67401, USA, Phone, (785)823-5376;
fax, (785)823-8728; e-mail, email@example.com
1. INTRODUCTION Food security dictates that the
dependence of farming on fossil fuels should be reduced by substitution
of on-farm resources for commercial farm inputs and by adoption of
renewable energy technologies. Energy analyses related to this endeavor
have shown in various countries that organic production generally
requires less energy than conventional production for crops [1,2] and
dairy farms [3-5]. The same was also found to be true for organic
treatments compared to conventional ones in long-term cropping
experiments [6-9]. Energy consumption per hectare was less on mixed
crop and livestock farms in six Amish communities compared to nearby
conventional production [10,11]. Amish farms are biologically
integrated because of their use of draft horses and livestock manure,
but they often employ stationary tractors to run threshing machines and
generators for milking equipment.
At least several national programs have been conducted on a
small group of energy-integrated farm systems, but with little energy
analysis of the overall systems. The US Dept. of Energy conducted its
Energy Integrated Farm System program during 1980-1987 with biogas
digesters on six swine and dairy operations and a fluidized-bed
gasifier on a cotton farm . Design requirements and economic
performance were reported for the technologies and some farms, but an
integrated energy analysis was published for only one farm, which
showed that energy conservation practices and alternative fuel sources
should reduce fossil fuel input into this farm by 60-70% . Some of
the farms were able to reduce their annual purchased energy
requirements by 20-60% . The other national program of
energy-integrated farm systems was initiated in the early 1980s by
EMBRAPA, the agricultural research system in Brazil . Pilot
demonstration projects were set up at eight research centers, employing
biogas digesters, gasifiers, small ethanol stills, and alternative
energy crops, but there appears to have been no reported energy
To explore the reduction of fossil fuel use in farming, The
Land Institute conducted its Sunshine Farm Project during 1991-2001. A
feasibility study was done during the first year to integrate the
cropping system, animal production practices, and power sources with
respect to demands for crop nitrogen, animal feed, biodiesel fuel, and
electricity. The amount of fuel, materials, and labor were recorded
during the next nine years for every farm task and for farm capital in
order to construct energy budgets for the crops, animals, power
sources, and the farm.
2.1 Farm and power sources
The mixed crop and livestock research farm was located near
Salina, Kansas (N 38°52'30", W 97°35'30") with its cropland on level,
coarse-silty Fluventic Haplustoll soil. The animal enterprises were
small-scale production of broilers and eggs and short-rotation grazing
of a cow-calf herd of Texas longhorn beef cattle on 65 ha of mostly
native pasture. Unirrigated, organic crops were grown on 20 ha in
narrow crop strips with different entry points in some five-year crop
rotations. To fix nitrogen, about 40% of the cropland was in legumes,
of which one-fourth was green manure and three-fourths, forage and
soybeans. No phosphorus or potassium was imported except a few kg per
ha of cropland annually in the form of manure from some purchased feed.
The three nutrients were adequate as indicated by soil tests and plant
tissue analysis conducted by the Kansas State University Soil Testing
Laboratory. Yields of wheat, oats, soybeans, alfalfa, and sweet sorghum
averaged over 1993-2001 were comparable to conventional dryland yields
averaged over the same years , but not grain sorghum and sunflowers
as a result of weed pressure and seed predation by birds, respectively
(Student's t-test, P<0.05).
A 4.5-kilowatt photovoltaic array provided electricity for
workshop tools, electric fencing, water pumping, and farmhouse.
Traction was provided by a pair of 450-kg Percheron draft horses and a
50-kw (70-hp) direct-injection diesel tractor run on biodiesel, namely
purchased soybean methyl ester fuel. In the analysis, we assumed that
the biodiesel was a 50:50 mixture of soybean and sunflower methyl
esters on a gross energy basis, with the oil mechanically presumably
extracted by a local farmers' co-operative in efficiencies of 50 and
75%, respectively [16,17]. We ignored our use of some purchased
high-protein feeds and assumed that we would have fed byproduct meal
cake from the co-operative, but still owned by the farm.
Although soybeans have a low oil yield, we did not consider
biodiesel consisting solely of sunflower, rapeseed, or canola methyl
ester because of agronomic limitations specific to the US. Future
expansion of organic production of sunflowers will be severely limited
by insect pests and diseases associated with its weedy ancestor, Helianthus annuus,
widespread in the US. Rapeseed and canola have been introduced to the
eastern and central US only in the past several decades and will
require genetic breeding and selection to overcome problems such as
pests and diseases, winterkill, vulnerability to drought, uneven
maturity, and excessive shattering [18-20].
2.2 Energy analysis
Embodied energy of farm inputs was based on weight-based process
energy values , except dollar-based energy intensities for
electronic materials  and medicines . Process energy values for
metal products were increased 25% to include energy used in fabrication
[24, 25]. Energy budgets included fuel to deliver farm inputs from
factories to dealers, based on national statistics for transportation
of freight . Primary energy displaced by electricity from the array
was 10.55 MJ (10,000 Btu) per kWh .
Embodied energy of purchased vehicles and farm machinery was
determined according to Doering . Embodied energy of facilities
constructed on the farm was obtained from our energy budgets. Next,
embodied energy in a purchased or constructed capital item was
amortized over its estimated lifetime to obtain an annual value that
was prorated among its uses within a given year on the farm in our
annual energy budgets.
Process energy values for purchased livestock, feed, and
seed were national or Midwestern estimates [26, 29]. For feed or animal
breeding replacements produced on our farm, the embodied energy was
determined from our energy budgets. Energy requirement was 75 and 25 MJ
per hour for human labor as a portion of the average lifestyle support
energy in the US and in Amish communities, respectively [11, 30]. Gross
energy content of farm outputs was based on the following sources:
crops , beef [32, 33], and broilers and eggs .
3. RESULTS AND DISCUSSION About 90% of the embodied energy
in annual inputs not counting capital or labor was in the form of
on-farm production of inputs, the latter in the following proportions:
feed, 35%; biodiesel fuel, 36%; leguminous nitrogen fixation, 24%; and
electricity from the array, 5% (Table 1).
The other 10% was purchased seed and phosphorus and potassium
fertilizer, the latter not actually used, but simulated in the energy
budget to offset nutrients removed in marketed products. Amortized
capital constituted about 40% of the total embodied energy in annual
and amortized inputs, not counting labor. On-farm production of inputs
met only 53% of the embodied energy in annual and amortized inputs, and
this dropped to 41 and 48% with the inclusion of labor as a portion of
average US and Amish lifestyle support energy, respectively.
Annual production from 20 ha of cropland on the farm amounted to
1,065 GJ of gross caloric energy in the following proportions: oil for
biodiesel, 8%; fed meal, 4%; marketed meal, 22%; fed crops, 34%;
marketed crops, 19%; and green manure legumes, 13%, the latter not
harvested (Table 2).
In other words, almost 85% of the byproduct meal was marketed, and of
the crops fed or marketed, nearly two-thirds were fed. The following
proportions of cropland area devoted to this production were fairly
similar to the respective proportions in gross energy: biodiesel and
byproduct meal, 30%; feed, 34%; marketed crops, 26%; and green manure
The Sunshine Farm is compared with other mixed farms in
terms of outputs relative to inputs. If a boundary is drawn around the
farm, then marketed outputs should be compared with purchased inputs.
The farm sold 440 GJ of marketed meal and crops, or 22 GJ per ha of
cropland, very much greater than most mixed crop and livestock farms (Table 3).
The reason for the great difference is that these farms feed most of
their crops, but the Sunshine Farm could feed only 15% of the byproduct
meal from its substantial biodiesel output and thus sold the remainder (Table 2).
The only exception to this pattern was the large crop output in the
group of conventional Illinois farms for which crops constituted nearly
60% of the gross energy in marketed outputs (Table 3).
In addition to the marketed meal and crops from the Sunshine Farm, the
19 GJ in animal products and the primary-energy equivalent of 42 GJ in
marketed electricity resulted in a total 501 GJ of marketed outputs, or
25 GJ per ha of cropland, not as different from the other mixed farms
as when crops alone were compared (Table 3).
The reason for the less pronounced difference is that crops made up
almost 90% of the gross energy in marketed outputs on the Sunshine
Farm, but only 14-29% on the other farms, except for the group of
conventional Illinois farms (Table 3).
In other words, much greater animal production on the other farms
brought them closer to the Sunshine Farm in total marketed outputs.
Gross energy in marketed outputs on the Sunshine Farm was 2.4,
2.0, and 1.5 times the embodied energy in purchased inputs, including
no labor, Amish-supported labor, and US-supported labor (Table 3).
The former energy ratio is the one most appropriate for comparison to
the other mixed farms because they contain charges for human labor that
are small as a result of considering only food consumption instead of
lifestyle support energy. This ratio of 2.4 is greater than the energy
ratios for most of the other mixed farms for two reasons. First, the
purchased inputs per ha for the Sunshine Farm are less than the values
for all conventional farms and some Amish farms in Table 3
despite the fact that purchased inputs included all amortized capital
on the Sunshine Farm but only equipment, machinery, and sometimes
building repair for the other farms. Second, proportionally less crops,
including meal from the oilseeds, were fed on the Sunshine Farm than
the other farms, thus incurring less energy losses in animal metabolism
and allowing greater marketed output (Table 3).
The greater energy ratio for the Sunshine Farm was not a result of the
photovoltaic array since its energy ratio was only 1.6, i.e.,
(11+42)÷34 (Table 1,
and 42 GJ noted above). These results are corroborated in 15
hypothetical farm energy budgets computed by Leach , in which
larger farm energy ratios were clearly associated with fewer purchased
inputs and greater proportion of outputs arising from crops. For the
same two reasons, national agricultural energy ratios are generally
higher in less developed countries than industrialized nations that can
afford energy-intensive inputs and diets based heavily on animal
It will be a challenge to provide society with considerable
energy from agriculture, let alone food, since the energy returns for
various energy technologies have generally been greater than the above
ratios for mixed crop and livestock farms. Fossil fuels usually have
ratios in the range of 10-30, and solar and wind technologies,
typically 3-10, but renewable liquid or gaseous fuels from agricultural
production, mostly 5 or less [37, 38]. Solar and wind technologies have
greater power densities than energy crops and thus require less land
area . Although the US exports one-fourth of its grain production
, diversion of this grain for conversion into useful energy would
meet less than one-half of the embodied energy in annual farm inputs
used by US agriculture .
Energy ratios in agricultural production could be raised by
reducing purchased inputs and by increasing marketed outputs. However,
in a future era of resources declining in quantity and quality, the
latter will be achieved less by increased yields than by diverting
cropland from supplemental animal feed to crops for direct human
consumption. The infrastructure and research needed to develop an
agriculture based on renewable power sources should be established now
while we have the luxury of high energy ratios from fossil fuels.
The author thanks The Land Institute for providing the facilities and procuring the funding for the Sunshine Farm Project.
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