초록 ▼

□ 연구 배경
○ 에너지/환경 이슈
- 에너지 소비증가율 5.6%, 높은 수입 에너지 의존도 (96.7%)
- 처리하기 어려운 고농도의 유기성 폐기물 (축산폐수)
○ 친환경 에너지전환 기술 필요 및 발생의 전환
- 축산 분뇨의 높은 유기물 농도 (평균 COD 농도 10,000 mg/L으로 에너지로 전환시 이론적 에너지 함량 120 GJ/day)
○ 하이브리드 미생물연료전지 기술개발 필요
- 혐기성 소화조와 미생물연료전지의 융합형 시스템을 이용 바이오가스/전기의 형태로 에너지 생산
- 공간적

□ 연구 배경
○ 에너지/환경 이슈
- 에너지 소비증가율 5.6%, 높은 수입 에너지 의존도 (96.7%)
- 처리하기 어려운 고농도의 유기성 폐기물 (축산폐수)
○ 친환경 에너지전환 기술 필요 및 발생의 전환
- 축산 분뇨의 높은 유기물 농도 (평균 COD 농도 10,000 mg/L으로 에너지로 전환시 이론적 에너지 함량 120 GJ/day)
○ 하이브리드 미생물연료전지 기술개발 필요
- 혐기성 소화조와 미생물연료전지의 융합형 시스템을 이용 바이오가스/전기의 형태로 에너지 생산
- 공간적 한계 극복 가능하며 기존 인프라에 적용 가능

□ 주요 연구성과
○ 2단 전처리 시스템 적용으로 질소 이온 제거능향상 및 전처리 전후 전류 발생값이 400%이상 증대
○ 전처리 시스템 적용 효과
- 에너지전환효율 : 0.2%에서 14%로 증가
○ 전류밀도(current density)와 전력밀도(power density) 측정
- 전처리 여부에 따라 최대전력밀도는 20%향상
○ 하이브리드 미생물연료전지 개발 및 전력량 향상 방법 탐색
- 축산폐수의 COD 농도 90% 이상 감소
- 직렬연결을 통한 전압의 3배 향상, 전력의 2배 이상 향상
- 직렬연결시 발생되는 전압역전현상 극복방안제시

□ 파급효과
○ 축산분뇨의 에너지화를 처리시설의 투자 및 운전비용 감소 효과
- 생산된 에너지의 실제 사용을 통한 직접적 에너지 수입 대체 효과 기대
- 영양염류 (질소, 인)의 회수가 가능하여 부가가치 산업 효과 기대
- 신재생에너지 선도기술 확보가 기대됨 (기후변화협약에 대처 가능)
- 원유의존도 축소에 따른 유가 안정화 도모
- 제안 핵심기술 개발 후 특허 취득을 통한 기술 로열티 확보
- 관련 산업 고용창출 효과가 기대
- 환경공학, 미생물학, 에너지 공학의 융합분야의 학문적 발전

Abstract ▼

Microbial fuel cell has received attention as an environmentally friendly energy conversion technology to change the energy conversion from organic contaminants in recent years. The research objective is to develop and optimize a hybrid microbial fuel cell (hybrid MFC) system which are combined with

Microbial fuel cell has received attention as an environmentally friendly energy conversion technology to change the energy conversion from organic contaminants in recent years. The research objective is to develop and optimize a hybrid microbial fuel cell (hybrid MFC) system which are combined with microbial fuel cell (MFC) and upflow anaerobic sludge blanket(UASB) for livestock wastewater treatment and energy recovery. For this studies, ammonia and nitrate nitrogen in livestock wastewater was controlled because these ions act as electron acceptor or inhibitor to bacteria in anode compartment. Therefore, pre-treatment system using microbubble and catalyst(Fe/MgO) was developed to decrease the nitrogen ions for increase the energy conversion efficiency of microbial fuel cell. After pre-treatment, ammonia nitrogen and nitrate nitrogen was removed up to 53% and 75%, respectively. The optimum operating conditions considering the economics was when 300g/L catalyst was used with air as the oxidant. When applied to the preo-treatment system, electricity generation efficiency was confirmed to be increased by about 400%. The maximum power density and current density 10.3W/m³ and 86A/m³ has occurred. This result showed that use of the pre-treatment system was to improve the efficiency of the microbial fuel cell by using a pre-treatment system. Utilizing the appropriate C/N ratio seems to be applied to biological treatment systems. Also, these studies were attempted to investigate if stainless-steel wire skein (SSW) could be used as anode electrode replacement a graphite felt electrode in microbial fuel cell. For these studies, pre-treated livestock wastewater used to dilute to 500 mg/L as COD. When stainless steel wire skein was used in place of an anode electrode (graphite felt), the current showed a little difference of about 5% initially, but current was increased over time, its difference was about 29%. The removal rate of organic pollutants of microbial fuel cells used graphite felt and stainless-steel wire skein was 40.6% and 87.5%, respectively. The COD removal of stainless steel wire skein was higher than that of graphite felt. Ammonium nitrogen was showed similar trend in two case all. These results about current generation and organic matter reduction were expected to apply a stainless steel wire skein to anode electrode. When the stain-less steel wire skein is used, the initial investment for system construction is expected to be able to reduce by approximately 1/50. Also to find electrochemically active bacteria in the enrichment step of microbial fuel cells, the change of microbial community was investigated. Microbial growth curve in enrichment culture step is changed to turn into stationary phases through an exponential phase and from lag phase. Microbial community in this step was estimated by confirmed by molecular biological techniques. In addition, the microorganism was isolated directly from the microbial fuel cell through the various combinations of electron acceptors with a carbon sources. Cupriavidus metallidurans (Rastonia) was confirmed that there is electrochemically activity bacteria. We investigated the conditions that can be mass-cultured Ralstonia. In order to develop the hybrid microbial fuel cell, each three units of 0.5 L scale of MFC reactors and 1.5 L scale of UASB reactors were manufactured. Each reactors showed the respectively 32% and 72% of COD removal rate, and 0.42 L CH₄/g SCODremoval of methane production rate during continuous operation. The performance of hybrid MFC which is combined with MFC and UASB reactor showed 544 mA/m² of maximum current density, 88 mW/m² of power density, 42% of coulombic efficiency, 0.39 L CH4/g SCODremoval of methane production rate, and 80% of COD removal rate. After change the type and material of the anode in the MFC, COD removal rate and coulombic efficiency were increased 90% and 50%, respectively. Increasing voltage and power (2 times) was observed through a series connection of MFC and the technology for overcoming voltage reversal phenomenon observation during series connection in MFC operation was developed. After 2 phase AD operation for economical production of biogas, methane gas was only detected as fuel but not hydrogen gas. This research is possible to improve the electricity generation efficiency of microbial fuel cell by control the nitrogen ions in livestock manure through the pre-treatment system. Also the system hybridized to enhance the energy efficiency. For this, this system can achieve the methane and electrical energy through the hybridization of the MFC and the UASB reactor at same time. Also a novel electrochemically active bacteria were isolated.