Section Seventeen
ANAEROBIC PROCESSES
63    BIOGASIFICATION OF SORGHUM IN A NOVEL
ANAEROBIC DIGESTER
Vipul J. Srivastava, Manager
Bioengineering and Environmental Research
Richard Biljetina, Director
Engineering Technology Research
Institute of Gas Technology
Chicago, Illinois 60616
H. Ronald Isaacson, Manager
Renewable Resources
Thomas D. Hayes, Project Manager
Regional Biomass
Gas Research Institute
Chicago, Illinois 60631
INTRODUCTION
The Institute of Gas Technology is studying the biogasification of community wastes in an experimental test unit located at the Community Waste Research Facility (CWRF) at the Walt Disney World
Resort Complex in Florida. This project is part of a larger program designed to provide solutions to
community waste treatment and disposal problems. Of primary importance to this program is the
implementation of low-cost, nonenergy-intensive waste treatment technologies and the net production
of energy (methane) from waste resources.
Five waste resource streams have been identified as potential energy production sources for a
typical community and its surrounding areas (Figure 1). They are sludge and biomass from wastewater treatment plants, municipal solid wastes, industrial wastes, agricultural wastes, and manure.
Nationwide these resources total about 750 million dry tons annually and after conversion could add
up to 5 quads to the nation's energy supply.1
The concept of waste treatment and subsequent methane production from these sources is being
studied in a novel solids concentrating anaerobic digester at the ETU facility designed, constructed
and operated by IGT. Operation of the ETU digester was begun in January of 1984. During 1984 and
1985, tests were conducted on blends of water hyacinth and sludge in support of a process concept
that provides effective secondary and tertiary wastewater treatment using aquatic macrophytes such
as water hyacinths. The water hyacinths were harvested from five one-quarter acre treatment channels
at the CWRF and were mixed with sludge from the primary clarifier. Blend ratios were maintained
between 2:1 and 1:1 water hyacinth/sludge to simulate expected production quantities from larger
commercial treatment facilities. Results from these tests demonstrated that, using a 1200-gallon (160
ft3) solids concentrating anaerobic digester, water hyacinth and sludge blends can be converted to
methane at higher rates and efficiencies than conventional stirred tank reactors.2 An economic
assessment completed by an independent engineering firm has shown that a combined water hyacinth
wastewater treatment and anaerobic digestion process results in the production of methane at $2.50
per million Btu or less.3
Rationale
The second feedstock selected for testing at the ETU was an agricultural product, sorghum,
because, as discussed earlier, one of the largest waste sources in the U.S. is the agricultural sector. Its
wastes represent over one-third of the 750 million dry tons as identified in Figure 1.
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