Construction, Operation, Maintenance and Research Evaluation of the Demonstration Anaerobic Sequencing Batch Reactor System to be Located at the Steve and Audrey Crawford Farm

Principal Investigator:

Shihwu Sung, sung@iastate.edu (other projects)

Co-Principal Investigator:

• Timothy Ellis, tge@iastate.edu (other projects)

Project Status: In Progress

Start Date: 04/15/1998
End Date: 03/16/2001


Research Objective: 1. Biogas production is in the range of 32,000 - 40,000 cuft/day with a +/- 70% methane content. Equivalent BTU for the biogas produced is 20-25 MBTU/day. How much was used to heat the building or digester is varied with the ambient and waste temperature. General speaking, in the hot summer day heat is not needed for the building, and for every 10 deg F difference between waste temperature and digester temperature (93 deg F) 1.5 MBTU is needed to heat the waste.

2. Propane was not used for heating purpose in the farm during the last quarter.

3. Crawford farm has an average 2,800 head of pigs. At an average weight of 160 lg/pig, estimated N, P, and K nutrients of 185, 70, and 100 lb, respectively, are produced daily. Nutrients in swine manure are mineralized into inorganic forms i.e. ammonia, phosphate during the anaerobic digestion and retain in the liquid effluent and solid residuals after the digestion. Most of the P is associated with the solid residuals and N is in the liquid. If the treated liquid is stored in a open space a an extended period of time say 6 month, a approximately 50% or high loss can occur due to volatilization. The ASBR is capable to destruct volatile solids of 55 to 65% at current operating conditions.

4. O&M costs: Electricity bill was $28-40/month. Last quarter, several equipment broke down including 2 submersible waste pumps and the biogas blower. The pumps were still under warrantee and blower was sent to shop for rebuild. Total cost of equipment maintenance cost was $800.

5. The ASBR waste treatment system provides benefits in the following areas:

a. Odor reduction: reduce odor by at least 70%, less ventilation during the winter due to the improvement of air quality in the confinement means less energy for ventilation

b. Energy recovery: 25 MBTU of heat can be recovered from the waste which equivalent to 25 MBTU x $2.8/MBTU = $70/day of energy.

c. Stabilize the waste with less pollution potential; convert organic nutrients to inorganic nutrients which can be readily uptake by the crops; pathogens reduction in the digestion process

d. Lessen the green house effect by control methane emission and use a renewable energy source other than fossil fuel.

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