The Energetics of Agroecosystems - Agroecology: The Ecology of Sustainable Food Systems - page 265

products away from direct human consumption and use
in agriculture (Hunt et al., 2006). Moreover, biofuels don't
always have a positive energy balance. For example, pro-
ducing 1000 L of ethanol requires 8.3 million kcal of
energy (much of it from fossil fuels) but that same 1000
L of ethanol has an energy value of only 5.0 million kcal
(Pimentel et al., 1998). Although biofuels have their place
in developing more sustainable agroecosystems, they are
not the easy solution that some claim.
The rapid increase in energy use in agriculture dur-
ing the 20th century radically changed the nature of

farming. With an understanding of energy as an eco-
logical factor in agriculture, and its use and flow as an
emergent quality of the entire agroecosystem, better
means of evaluating current practices can be developed,
contributing at the same time to the development of
practices and policies that establish a more sustainable
basis for the world's food production systems in the
21st century. The longer it takes to develop alternative,
ecologically sound energy use and conversion systems,
the more vulnerable our current energy-dependent sys-
tems will become.

THE SUNSHINE FARM PROJECT

Before the middle of the 1900s, many farms ran mostly on sunlight. They used crop rotations and farm-produced
manure to maintain soil fertility, and work was done by draft horses and people fed by on-farm production. With
these farms of 100 yr ago in mind, Marty Bender at the Land Institute set out in the early 1990s to create a modern
farm that could provide its own fuel and fertility. The result was the Sunshine Farm, a 10-yr-long demonstration
project consisting of 50 acres of conventional crops and 100 acres of prairie pasture grazed by cattle near Salina,
Kansas.
As the farm took shape, it showed many similarities to farms of the early 1900s and before. Livestock and
crops were integrated, draft horses performed work, a variety of crops were grown, and at any one time about
40% of the cropland was planted in legumes. Unlike a farmer in the 1920s, however, Bender had, at his disposal,
some newer renewable energy technologies.
He had a 4.5-kW photovoltaic array installed to provide for all of the farm's electricity needs, which included
running the workshop tools, charging the electric fencing, running the water pumps, heating the chick brooders,
and providing electricity for the farmhouse. A pair of Percheron draft horses and a biodiesel tractor provided
motive power for field operations. Bender planted about one quarter of the farm's cropland in soybeans and
sunflowers to provide the raw material for the tractor's biodiesel fuel; however, since on-farm processing was not
feasible, the oilseed was sold to a local cooperative, and an equivalent amount of biodiesel fuel purchased.
The livestock side of the farm's commercial enterprises consisted of a beef cattle operation, along with poultry
raised to produce eggs and broilers. About three fourths of the feed for these animals (and the draft horses) was
produced on the farm. On the crop side, wheat was grown for sale, and excess oilseed meal was also sold. The
major components of the farm operation are listed in Table 18.4.
Energy accounting was a crucial facet of the Sunshine Farm project. Bender and colleagues carefully measured
the weight of every farm input and output, using energy factors published in the academic literature to derive
equivalent energy values. These data were painstakingly entered into a database, and used to generate energy
budgets for the farm as a whole and for its constituent enterprises. These budgets included both direct and indirect
energy costs.
The energy accounting showed that over the course of the demonstration, about 90% of the farm's energy
needs — not counting the energy embodied in capital outlays and human labor — were supplied by on-farm
inputs. The remaining 10% was the energy embodied in purchased seed and feed, and in the phosphorus and
potassium removed in the marketed crops (Bender, 2002).
The Sunshine Farm project served many purposes. Primarily, it demonstrated that farming operations can
come close to attaining energy self-sufficiency without sacrificing yields. It showed that many traditional farming
practices — rotations, green manuring, livestock integration, crop diversity, use of draft animals — can be essential
components of energy-efficient agroecosystems, and that modern alternative energy technologies can also play an
important role. In addition, it showed that increasing the energy self-sufficiency of individual farms is not the
only means of reducing agriculture's dependence on fossil fuels. Farms may also need to be integrated into a local
renewable energy economy, as the Sunshine Farm did in growing oilseed but leaving biodiesel fuel production to
a larger-scale cooperative, and in tying its photovoltaic array into the local power grid.