July 1, 2004 | General


BioCycle July 2004, Vol. 45, No. 7, p. 57
Developed at North Carolina State University, digester needs to be operated at full-scale to verify rapid pathogen destruction, biogas production rates and economics.

THE THERMOPHILIC anaerobic digestion (TAnD) process developed in the poultry science department at North Carolina State University is reported to have several key advantages over other animal waste treatment technologies. According to Kurt Creamer of the North Carolina Solar Center in Raleigh – who worked with Prof. Jason Shih on its development, one crucial advantage is the rapid destruction of pathogens at the elevated temperatures associated with thermophilic AD. “The rate of volatile solids reduction is also greater at these elevated temperatures, resulting in much simpler design and small vessel volumes compared with mesophilic or ambient temperature digesters,” explains Creamer. But now the challenge is larger scale analysis.
Although the TAnD process has been pilot tested here and at full-scale overseas, it has never undergone a rigorous full-scale evaluation in the U.S. Nor has a thorough evaluation been conducted of the biogas production rates for the TAnD and the demonstration of biogas use in an engine/generator. Another area where commercially crucial information is missing is the potential uses and value of the digested solids that are a coproduct of the TAnD process.
An agreement was signed recently by North Carolina Attorney General and several pork industries to develop “environmentally superior technologies” for waste management. TAnD was selected as one of them for demonstration, but the Agreement will only pay for basic construction and short-term operation of the facility. Funding has been requested to conduct the following tasks needed to achieve commercialization and fulfill these objectives: To instrument and monitor the TAnD, evaluate its performance and operational characteristics, and prepare complete mass and energy balances for the system; To evaluate biogas treatment systems, utilization of the biogas in an engine/generator, and the use of the engine coolant to heat the digester feed; To develop horticultural substrates, potting mixes and fertilizer products using digested solids from the TanD; To evaluate a process for nutrient removal from the liquid effluent of the TAnD to increase application rates and reduce environmental impacts; and To conduct a detailed analysis of the economics of the TAnD that includes potential revenue streams such as the gas produced and the solids coproduct.
These objectives would be met through field research and laboratory analysis conducted over the course of two years primarily at the TAnD facility at the North Carolina Department of Agriculture’s Upper Coastal Plain Research Station near Rocky Mount, North Carolina.

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