Herein , the effect of changes in the organic loading rate in anaerobic digestion was evaluated. The experiment was carried out by a laboratory -scale semi-continuous stirred tank reactor, and feedstock was food-waste leached. The organic loading rate was increased by 0.5 kgVS/m3 in each phase from 1.0 kgVS/m3 to 4.0 kgVS/m3. At the end of the operation, to check the failure of the reactor, the organic loading rate was increased by 1.0 kgVS/m3 in each phase and reached 6.0 kgVS/m3. This shows that the biogas yield decreased as organic loading rate increased. Biogas production seemed to be unstable at 3.5–6.0 kgVS/m3. Moreover, biogas production dramatically fell to approximately 0 mL at 6.0 kgVS/m3, which was decided as the operation failure on the 16th day of the las tphase. The result of the reactor analysis shows that the cumulation of volatile fatty acid increased as the organic loading rate increased. This seems to occur due to the decreasein pH in the reactor and led to extinction of anaerobic bacteria, which were the biogas products. Although the buffer compound (alkalinity) could prevent the decline in pH, the concentration of alkalinity was found to be lacking at a high organic loading rate

Organic wastewater generated from polyester manufacturing processes was selected from H company to investigate the feasibility of anaerobic digestion that produces gases including methane. Bio Methane Potential (BMP) tests were conducted to measure the gas production and methane concentration for 7 process wastewater and 2 kinds of sludges from the H company. Also, along with monitoring pH and alkalinity during the anaerobic digestion process, the concentrations of COD and 1,4-dioxane were measured with 4 different operating conditions for N Emulsion (NE) and Ethylene Glycol (EG) wastewater. The BMP tests showed that 65% of methane was produced from NE and EG wastewater. This suggests that the organic wastewater from H company can be effectively treated by an anaerobic digester by which more than 90% of COD was removed.

화석연료의 고갈로 인한 고유가 상황과 온실가스에 의한 지구온난화가 가시화 되면서 재생 가능한 에너지개발과 자원의 효과적인 이용을 통한 자원순환사회 구축, 나아가 친환경적인 사회구현이라는 목표를 달성하기 위하여 선진국을 중심으로 환경과 에너지 문제를 해결하기 위한 연구가 진행되어 왔다. 이러한 전망을 토대로 국가적 부담을 최소화하고 실리를 추구할 수 있는 적극적이고 능동적인 대처방안을 강구할 필요성이 절실한 시점이다. 최근 신재생에너지의 확충과 기후변화 협약에 대한 적극적인 대응이 요구됨에 따라 단순 매립되던 폐기물을 에너지로 전환하여 처리하는 방식이 각광받으며 정부 계획 하에 적극적으로 추진되고 있다. 이러한 대응의 일환으로 1990년대 후반에는 유렵을 중심으로 연성에너지 체제에 부합하면서 지방자치단체 지역 공동체, 지역 주민들의 에너지 생산 활동 참여를 중시하는 지역에너지 체제가 대안으로 제시되었다. 에너지자립마을은 화석연료에 대한 의존도가 낮으며 지속가능한 마을과 유사한 것으로, 환경문제와 미래에너지 문제를 함께 고려한 개념으로 마을에서 발생되는 자원을 최대한 이용하고, 그 자원을 순환시키는 마을로 이해될 수 있다. 국내에서는 2009년부터 농림수산식품부, 환경부, 지식경제부 등 정부부처가 합동으로 각종 바이오매스를 이용하여 에너지 자립형 마을 시범사업을 추진하면서 축산 바이오매스를 이용하는 바이오가스화 기술은 농촌 지역에 도입할 수 있는 가장 실행 가능한 기술로 평가받고 있다. 본 연구에서는 농촌형 에너지자립마을에서 발생될 수 있는 다양한 유기성폐기물을 대상으로 혼합 원료의 특성과 병합 혐기성소화의 효율을 평가하기 위하여 biochemical methane potential test(BMP test)를 진행하였다. 또한, 본 연구를 바탕으로 혐기성소화와 C/N비의 관계를 알아보고자 하였다.

우리나라는 4계절이 뚜렷하여 안정적인 중온소화를 진행하기에 환경적 어려움이 있다. 혐기성 소화조의 안정적인 소화를 위하여 가온 에너지는 필수적인 요소이다. 이를 위해 본 연구에서는 이러한 환경에 적합한 소형 혐기성 시설의 개발을 위하여 고농도 유기성 폐기물인 돈분뇨와 음식물류폐기물을 전처리 과정 없이 고액분리만을 통하여 액상의 고농도유기물만을 혐기성소화조에서 에너지원인 바이오가스를 생산하는 Pilot Plant의 성능과 소화효율을 분석하였다. 혐기성 소화조의 가온을 위하여 겉에는 호기성 소화조를 설치하여 호기 발효열을 혐기성 소화 가온 에너지로 이용 가능하도록 설계하였다. 이 호기성 소화조에서는 음식물류폐기물을 이용, 호기성 분해를 통해 퇴비를 생산하였으며, 이 과정 중 발생한 분해열(최대 75℃)을 이용, 혐기성 소화조를 가온하였다. 혐기성 소화의 성분 변화에 따른 바이오가스를 분석하기 위하여 혐기성소화조에 투입되는 유기물(VS)농도, 원료배합(돈분뇨 중 분성분이 30%, 뇨성분이 70%) 등 운전조건의 변화에 따른 유기물(VS) 제거율, CODcr 제거율, 바이오가스 생산량 및 메탄농도, 유기물용적부하에 따른 바이오가스 발생량 등을 분석 하였다. 음식물류 폐기물과 돈분뇨 혼합비에 따라 CASE 1, CASE 2, CASE 3로 분류하였으며, CASE 1의 비율은 음식물류 폐기물 8kg과 돈분뇨 20L, CASE 2 음식물류 폐기물 10kg과 돈분뇨 20L로 진행하였다. 분석결과 호기성 발효조의 평균 온도는 계절에 관계없이 50℃~70℃로 나타났으며, 호기성 발효조의 발효열이 높을수록 혐기성 소화조의 온도 또한 증가하는 경향이 나타났다. 이 결과 혐기성 소화조의 온도는 평균적으로 38℃로 중온소화가 가능한 것으로 확인되었다. 혐기 소화의 경우 투입원료의 유기물(VS)량에 따른 바이오가스 발생량은 CASE1에서 유기물(VS)은 평균 6.09%으로 분석되었으며, 이에 따른 바이오가스 발생량은 0.29~0.31㎥/day로 나타났다. CASE 2는 유기물(VS)평균 농도가 7.7%, 바이오가스 발생량이 0.325㎥/day로 나타났다. CASE1, 2 각각의 CODcr, 유기물(VS) 평균 제거율은 CASE 1이 56%, 76.61%, CASE2가 62%, 81.86%로 분석되었다. 메탄 함유량 또한 60~77%로 측정되어 연료로써의 가치가 확인되었다. 본 연구를 통하여 호기성 산화열을 혐기성 소화의 가온 에너지로서 사용하는 방식의 상용화 가능성을 확인할 수 있었으며, 현재 운영하는 혐기성 소화 시설만이 아닌 마을단위의 유기성 폐기물을 처리할 수 있는 소규모 시설로서도 운영이 가능할 것으로 보이며, 이에 따라 좀 더 효율적인 유기성 폐기물의 처리를 가능하게 할 수 있을 것으로 기대된다.

The purpose of this study was to evaluate the characteristic and efficiency of anaerobic digestion (AD) of various organic wastes, and to find a way to enhance the efficiency of AD. Ten types of organic wastes including slaughterhouse waste (SHW), agricultural by-products (AB), animal manure (AM), sewage sludge, and food waste (FW) were selected. Elementary analysis was carried out to confirm the effect of C/N ratio on AD. Elementary analysis of the AB of maize showed the highest C/N ratio of 42.55. The lowest C/N ratio of 3.41 and 3.46, respectively, appeared from the SHW of the blood from cattle and swine. The cattle rumen content of SHW had a C/N ratio of 19.2, which was included at range of optimum C/N ratio, and AM showed a low C/N ratio because of the lack of a carbon source. The AB of beets had the highest biogas yield of 0.81 m3/kgVS, which was measured by the BMP test. Biodegradability was also calculated based on the BMP test result. FW was found to have the highest biodegradability of 92.14%. However, cattle rumen contents had low biodegradability (34.02%) because their substrate material consists of fibroid, while AM had the lowest biodegradability (15.34%) because of its low C/N ratio.

A bioelectrochemical anaerobic digester for food waste was developed by installing an anode (−250 mV vs. Ag/AgCl) and a cathode (−550 mV vs. Ag/AgCl) inside a conventional lab-scale anaerobic digester. The performance of the bioelectrochemical anaerobic digester was investigated at different organic loading rates of 0.70-4.25 g VS/L.d. The bioelectrochemical anaerobic digester was rapidly stabilized within 25 days after start up, and at an organic loading rate of less than 1.97 g VS/L.d., state variables such as pH (7.0-7.8) and alkalinity (10-12 g/L as CaCO3) were very stable. The volatile fatty acids were maintained at 400-500 mg HAc/L with their main component being acetic acid (80%). At an organic loading rate of 1.97 g VS/L.d, the performance was significantly high in terms of the specific methane production rate (1.37 L CH4/L.d) and the methane content in the biogas (around 74%). The removal efficiencies of volatile solid and chemical oxygen demand were also as high as 80.1% and 85.1%, respectively, and the overall energy efficiency was 91.2%. However, the process stability deteriorated at an organic loading rate of 4.25 g VS/L.d.

In this study the effects of co-digestion of sewage sludge and food waste leachate on the anaerobic digestion efficiencyfrom sewage treatment facilities in S. Korea were investigated. For this study 15 facilities were selected including 9facilities treating sewage sludge only (S-Only) and 6 facilities treating sewage sludge and food waste leachate (S-MIX).The average volatile solid (VS) removal rate of S-Only was 30.7% and that of S-MIX was 45.2%. The COD removalrate of S-MIX (61.3%) was higher than that of S-Only (48.6%). It has been observed that the anaerobic digestion efficiencyof S-MIX was superior to that of S-Only because S-MIX contained more sufficient nutrient with higher VS contents andtotal solid (TS) contents emerging from food waste leachate. Therefore food waste leachate addition in sewage sludgeanaerobic digestion would be the preferred option to treat only sewage sludge.

Seaweeds are received high attending as one of new and renewable energy sources. In this study, the effects of organic loading rate (OLR) and hydraulic retention time (HRT) on anaerobic digestion with Laminaria japonica were investigated using labrotory-scale semi-continuous stirred type reactors. The results demonstrated that anaerobic digestion of Laminaria japonica performed stably with OLRs in the range of 1.00 ~ 1.50 g-VS/L⋅d and HRTs in the range of 27 ~ 40 days. The maximum methane production obtained was 251.33 mL-CH4/L⋅d, which was achieved for an OLR of 1.50 g-VS/L⋅d and a HRT of 27 days. However, an OLR of 1.75 g-VS/L⋅d and a HRT of 23 days brought about a decrease in the pH and volatile fatty acids (VFAs) accumulation, causing the destabilization of the reactor and process failure. The reactors operated at a constant influent substrate concentration, i.e., 40 g-VS/L, thus OLR and HRT could not be treated separately and independently. According to the limited results of this study, it seems that the suitable OLR of anaerobic digestion of Laminaria japonica was lower than 1.50 g-VS/L⋅d and suitable HRT was higher than 27 days.