초록 ▼

연구개발 결과
본 연구개발은 마을단위에서 발생되는 각종 유기물 폐기물을 직접 처리하여 호기성산화발효열을 가온용에너지로 이용하여 혐기성소화조를 가온하는 시스템으로써 대상 마을의 에너지 자립화가 가능한 Pilot Plant를 개발하는 것을 목적으로 수행.

1. 호기성 발효조 및 혐기성소화조의 온도영향
호기성발효조의 경우 외기온도에 관계없이 40~60℃정도의 일정한 수준의 온도범위를 나타내었으며, 운전기간동안 호기성발효조의 평균온도는 약 51℃정도로 나타나 동절기에도 영향을 받지 않는 것으로 판단.

운

연구개발 결과
본 연구개발은 마을단위에서 발생되는 각종 유기물 폐기물을 직접 처리하여 호기성산화발효열을 가온용에너지로 이용하여 혐기성소화조를 가온하는 시스템으로써 대상 마을의 에너지 자립화가 가능한 Pilot Plant를 개발하는 것을 목적으로 수행.

1. 호기성 발효조 및 혐기성소화조의 온도영향
호기성발효조의 경우 외기온도에 관계없이 40~60℃정도의 일정한 수준의 온도범위를 나타내었으며, 운전기간동안 호기성발효조의 평균온도는 약 51℃정도로 나타나 동절기에도 영향을 받지 않는 것으로 판단.

운영결과 혐기성소화조의 온도는 봄, 여름, 가을, 겨울 각각 33.05℃, 41.86℃, 34.83℃, 25.77℃로 분석되어 겨울철에 온도가 하락하는 현상이 나타났지만 25℃이상을 유지 할 수 있는 것으로 판단.

2. 혐기성소화 효율
전체 운전기간동안 COD 및 VS의 평균 유기물제거효율은 62.68%, 75.41%로 상당히 높은 유기물 제거효율을 나타내는 것으로 분석되었음. 또한 혐기성 소화를 통한 최대 바이오가스 량은 약 554L/day로 나타났으며, 하루 평균 350L/day의 바이오가스가 발생되었음 이는 혐기성소화에 의한 미생물분해가 활발히 이루어진 것으로 판단.

3. 발효 및 소화 부산물 타당성
3-1 퇴비
퇴비의 타당성을 평가하기 위하여 pH, 중금속, 종자발아법, 원형크로마토그래피 등을 평가한 결과 pH는 비료로서의 활용이 가능한 것으로 분석 되었고, 중금속은 세 번의 측정을 시행한 결과 실험에 사용된 시료가 중금속 기준치보다 낮은 결과가 측정되었으며, 종자발아법을 시행한 결과 발아지수 70이상을 나타내어 비료로서의 사용이 타당한 것으로 사료.

3-2 액비
액비의 타당성을 평가하기 위하여 중금속, 염도, pH를 측정한 결과 중금속의 경우 모든 항목에서 기준치 이하로 측정됨. 염도의 경우 충분한 액비의 발효기간을 거친다면 액비로서의 사용이 가능한 것으로 분석되었으며, pH의 경우 일부 9.0이상을 나타냈지만 크게 초과하지 않는 것으로 전체적인 결과에서는 혐기성 소화를 통하여 발생되는 액비는 비료로서 사용이 가능한 것으로 판단.

다수의 호기성 산화열을 이용한 혐기발효시스템을 응용한 기술의 특허를 등록한 상태로 본 연구를 통하여 개발된 혐기발효 시스템을 대용량화(Scale-up)하면 대규모 병합처리가 가능한 혐기발효 시스템으로 소규모와 대규모 모두 운영할 수 있는 시스템 또한 본 연구를 통하여 혐기발효 시스템의 운영 매뉴얼, 이용가능 부지 선정에 대한 정보 제시.

(출처 : 요약서)

Abstract ▼

Ⅳ. R&D result
A. Summary of year 1 R&D result
(1) Effect of temperature on aerobic fermenter and anaerobic digester
Temperature of anaerobic tank may be kept over 27℃ in cold weather, 33℃ in fall and over 35℃ in summer. Accordingly, while external temperature affect anaerobic tank and aerob

Ⅳ. R&D result
A. Summary of year 1 R&D result
(1) Effect of temperature on aerobic fermenter and anaerobic digester
Temperature of anaerobic tank may be kept over 27℃ in cold weather, 33℃ in fall and over 35℃ in summer. Accordingly, while external temperature affect anaerobic tank and aerobic tank temperature, if organic matter supply and air supply are controlled normally, it is possible to keep anaerobic tank temperature maintenance by the temperature of aerobic tank

(2) Effect of air supply on aerobic tank
Air supply has an effect on temperature change of aerobic fermenter and also on organic water content in aerobic fermenter. When, organic matter property in aerobic fermenter was examined, the water content level of 61% was reduced to 57%. Air supply of 15L/min·㎥ and 20L/min·㎥ increased aerobic fermenter temperature while keeping optimal water content for aerobic digester operation. Thus, it was found that the effect of external temperature on aerobic fermenter was insignificant.

(3) Effect on biogas and methane gas generation
Factors affecting biogas from anaerobic digest in year 1 include temperature of aerobic fermenter, circulation of digest liquid, suitable concentration of organic matter and pH of organic matter. Suitable value of each item was figured out.

B. Summary of year 2 R&D result
The study aimed to develop a pilot plant (aerobic fermenter and anaerobic digester) for energy self-supporting by treating organic waste directly. As Korea has winter season, it is hard to secure anaerobic digester warming energy, a new system of warming anaerobic digest using oxidation heat from aerobic fermenter was suggested.
The device was designed, produced, installed and operated followed by upgrade and improvement of problems. In doing so, the optimal operating condition was figured out and feasibility of biogas production from efficient operation was reviewed.

When a small anaerobic digest system was applied to farm houses, food waste and organic wastes could be handled directly and fermentation and digest products were restored to farm houses to recycle such materials which resulted in economic benefits.

It was found that treatment cost of organic waste such as livestock excretion and food waste was reduced and fertilizer and liquid fertilizer decay could be obtained through aerobic fermentation and anaerobic digest. If biogas from anaerobic digest is collected through collecting facility and stored in compressed storage, it could be used as cooking and heating energy of farm houses.

(1) Effect of temperature of aerobic fermenter and anaerobic digester
This study reviewed the effect of external temperature and in house temperature on temperature maintenance of aerobic fermenter or warming anaerobic digester with the target of keeping anaerobic digester for 30℃ without external warming.

There was a limit of over 30℃ mid-temperature digest of anaerobic digester in cold weather without external warming. If improved solar power hot water is used which was applied to improved pilot plant, it is analyzed that mid-temperature digest would be possible.

Air supply was carried out to fermenter in order to increase oxidation heat of aerobic fermenter. It was confirmed that high oxidation heat of 50~70℃ was generated due to increase of oxidation heat by air supply. When input air supply is 0L/min·㎥, 15L/min·㎥, 20L/min·㎥, added value of temperature change by aerobic reaction process was indicated. When air of 15L/min·㎥ was input, the added value of temperature was about 1.3 times higher. When air of 20L/min·㎥ was input, it had about 1.6 times higher than other conditions. Accordingly, to keep efficient aerobic oxidation heat generation, it was analyzed that air of 20L/min·㎥ was suitable.

(2) Anaerobic digest efficiency
In the year 2 study, temperature and organic matter loading had the greatest impact on anaerobic digest operation. According to this study, by keeping a certain temperature of anaerobic digester, the efficiency of anaerobic digest increased and biogas generation and organic matter removal rate increased.
The temperature maintenance of anaerobic digester is the greatest influence factor of oxidation heat on aerobic fermenter. Temperature between aerobic fermenter oxidation heat and anaerobic digester has proportionate relation. While temperature of anaerobic digester is influenced by external temperature, if oxidation fermentation heat efficiency of aerobic fermenter was good, it was not affected by external temperature.
Therefore, along the increase of aerobic fermenter oxidation heat, temperature of anaerobic digester increased too.

(3) Feasibility of digest residue
(A) Fertilizer
It was analyzed that pH of fertilizer belonged to pH 6~8 in all experiment groups except for October. At the initial fertilization stage, pH tends to increase to pH 8∼10, and if decay progresses, pH decreases. Fertilizer in October had pH 10 which is considerably high. It is the PH in initial fertilization. Thus, fertilizer in October needs more oxidation fermentation process.

As for seed germination method, all test groups had more than 70 of germination index. If storage period was shortened, germination index tended to reduce. It seems because decay of fertilizer is progressed as storage period continues.

As for salinity, it was measured in dry and wet amount. For salinity in wet, it belonged to basic value with less than 2% in ‘Fertilizer standard setting and designation’. If it was based on dry, all test groups had higher level than basic value.

It is because salinity increased by continual accumulation of salinity. To control salinity of fertilizer, it is necessary to add airflow improver in the course of fertilization of food waste that is mixed with fertilizer for decay. This study introduced the concept of annihilation to refrain release of internal material. It is required to transfer system that release partial material by adding sawdust.
Circular chromatography is a test to determine corrosion in fertilizer. It was measured as full fermentation in April. And, it showed a stage after decay in all test groups.
This also shows the process of decay of fertilizer by storage period.

As for heavy metal content, fertilizer of S Company was analyzed to exceed basic value of nickel in May, July, August, September and October. It is necessary for the above fertilizer to reduce nickel in order to use as fertilizer.

(B) Liquid fertilizer
As for liquid fertilizer pH, September, October, November and December are mid-decay and full decay was measured from February to June.
As for August and September, pH over full decay was measured. Liquid fertilizer was stored at room temperature without further fermentation after sampling. It seems more time required for complete decay of liquid fertilizer.

Salinity of liquid fertilizer exceeded basic value in all test groups. Thus, it needs to control salinity in liquid fertilizer after further fermentation. To control salinity, it is required to sporadic removal of anaerobic digest sludge deposited in anaerobic digester.

Based on ‘Fertilizer standard setting and designation’, as for the content of fermentation liquid (%), the total amount of nitrogen, phosphoric acid and potassium was more than 0.3% respectively. In this study, livestock excretion fermentation liquid was sampled monthly. The ingredient analysis content of nitrogen, phosphoric acid and potassium is as follows. Content of heavy metal in liquid fertilizer is lower value that does not exceed the basic value determined in ‘Fertilizer standard setting and designation’.

(4) Scope of use and application for applying a small anaerobic digest system to the site
To achieve greenhouse gas reduction target, Korea performs RPS system to supply renewable energy. In this system, biogas is classified as an important renewable energy source.
The issue is stable operation of biogas facility. And technical development for stable operation is actively progressed.

Organic waste and organic sludge require much cost for treatment (150,000 won per ton). Cost reduction and collection of energy are key issues. It needs recycling of organic waste at the same time of treatment. Solid waste can be used as fertilizer and liquid waste can be used as liquid fertilizer that contributes to resource circulation.

As for market trend of biogas facility in Korea, while it is operated in many places together with public treatment plant, actual effect of biogas is not significant. . As produced biogas is used as anaerobic digester warming energy, the use of biogas is rather low.

It is expected that the small anaerobic digest system developed in this study would change the current market trend of biogas facility. While a small biogas facility has difficulties in warming, and warming may reduce economic feasibility, it is possible to securer warming energy by linking between aerobic and anaerobic. As no other external warming energy is required to operate stable anaerobic digester, it is thought that the utilization of biogas would increase.

(A) Applicable scope and application target of small anaerobic digest system
It is a small anaerobic digest system that improves problems of existing large anaerobic digest facilities and that secures operating convenience. Such system could be applied to a small village unit, livestock and organic waste generating facility. It is targeted to small size farm houses, dense residential area, small business place where livestock and organic waste are generated for a certain amount, and small village unit with less than 50 households. The basic concept of the system is to input liquid organic matter and solid organic matter respectively for separating treatment, which needs to grant solid and liquid separating function. To secure convenience of management and operation, an unmanned system is applied for automation. And A/S needs to be performed quarterly.
Biogas from small anaerobic digest system needs to be used without separate purification process. Anaerobic digest residue can be recycled as liquid fertilizer and aerobic fermentation can be used fertilizer. As such, it can develop resource recycling village that facilitates the reuse of waste resources by means of organic waste treatment. At the initial stage of small anaerobic digest system distribution, it is installed in the site by the government support project. In the next place, a wide distribution would be available. After checking response of residents and their interests, the distribution could be further widely made. But, as for small anaerobic digest system, it has limited capacity in the organic waste processing, it is analyzed that the expectation of biogas use seems not significant.

(B) Available scope of use by applying small anaerobic digest system
By applying the strength and the basic concept of the small anaerobic digest system developed in this study for the use of warming up energy from aerobic oxidation fermentation heat, it needs to develop the technology to treat large amount of organic waste. Technical application can be divided into large scale sewage and waste anaerobic digest system using aerobic fermentation heat as warming energy, and large organic waste anaerobic digest system using aerobic fermentation heat as warming energy. It is revised design of the existing small anaerobic digest system. It changes existing circular shape fermenter and digester into oval shape to expand treatment capacity.

It needs to develop structure to input liquid waste and solid waste separately and to grant solid and liquid separating function to treat high concentrated waste water and solid organic matter.

As for large biogas facility which applies technology, while the on-site operator and manager are essential, it is necessary to embody unmanned or automated management system. Biogas can be used in various ways and anaerobic digest waste can be used as liquid fertilizer and aerobic oxidation fermentation waste can be used as fertilizer. Thus, it enables to make resource recycling system in the relevant area.
Through economy of scale, expanded use of biogas may be possible and organic waste can be recycled as waste resources in the region.

Large sewage and waste water anaerobic digest system is an anaerobic digest system designed to suit large treatment of concentrated sludge in the waste water treatment facility. After concentration of waste water sludge, it is introduced to anaerobic digester to decompose organic matters and to produce biogas. It is designed that anaerobic digester is divided into acid fermenter Ⅰ and Ⅱ, anaerobic digester and deposition room to decompose concentrated sludge. Digest liquid is separated from liquid to solid.

The residue liquid is returned to sewage and waste water treatment plant and solid matters are input to aerobic fermenter to decompose organic matter through oxidation fermentation. Aerobic oxidation fermentation product can be used fertilizer or decay soil. Oxidation fermentation heat from aerobic fermenter can keep anaerobic digester temperature (over 30℃) using anaerobic digester warming energy. By anaerobic treatment of dehydrated sludge, the waste could be reduced and the final solid matters could be used as fertilizer and decay soil which facilitated sludge free system.

The large organic waste anaerobic digest system is fermentation and digest system that is suitable to treat organic waste in a small city using oxidation fermentation heat of aerobic fermenter. Organic waste is separated by solid and liquid. Solid is input as aerobic fermenter and liquid is input as anaerobic digester. Fermentation heat of aerobic fermenter can be used as warming energy of anaerobic digester to keep a certain degree of temperature (over 30℃). Oxidation fermentation matter of aerobic fermenter can be used for fertilizer and biogas of anaerobic digester can be used for cooking. And, digest liquid can be used as liquid fertilizer. Thus, it may increase value of waste resource and utilization.

Anaerobic digester is divided into acid fermenter Ⅰ and Ⅱ, anaerobic digester and deposition room for perfect decomposition of organic waste. Anaerobic digester is developed to input organic matter with 1 pumping system and to enable internal circulation of digest that prevents deposition of digest liquid inside and to return part of final digest liquid.

C. Summary of year 3 R&D result
This R&D aimed to develop a pilot plant for energy self-support of the target village by direct handling of organic waste to warm up anaerobic digest using aerobic oxidation fermentation heat as warming energy. As anaerobic digester warming energy is essential in Korea due to winter season, this R&D system suggests anaerobic digester warming system using aerobic oxidation heat. It updates and revised operating technical issues and problems and final design drawing was prepared and reviewed.

The small anaerobic digest system developed in this study could handle organic waste from food waste and farm. Fermentation and digest byproducts could be recycled to farm houses which give economic profits. It is available to treat large volume of organic waste and it increases large biogas facility to improve use of biogas. Therefore, it can be efficiently used in city, borough and county areas.

(1) Temperature effect of aerobic fermenter and anaerobic digester
This study aimed to keep anaerobic digester temperature at over 30℃ using oxidation fermentation heat at aerobic fermentation without using external heat energy. The study reviewed external temperature, in house temperature and factors affecting aerobic fermenter temperature and warming anaerobic digester.

As for aerobic fermenter, it showed constant level of temperature scope at 40~60℃ without external impact. Average temperature of aerobic fermenter during operating period was about 51℃. It was found not to be influenced in winter season. Anaerobic fermenter having been greatly affected by external temperature seems to have temperature buffer effect that prevents rapid decrease of digest in winter season thanks to oxidation fermentation heat of aerobic fermenter. As a result of operation, temperature of anaerobic digester was 33.05℃, 41.86℃, 34.83℃ and 25.77℃ in spring, summer, fall and winter respectively. While temperature decreases in winter, it can maintain over 25℃.

(2) Anaerobic digest efficiency
Anaerobic digest is made by diverse microbes and organic decomposition is made by each microbe. Besides organic waste decomposition, it has microbe proliferation and destruction with unique bioreactor followed by decomposition of protein, lipid and carbohydrate. Anaerobic reaction can be divided into hydrolysis, acid production and methane production. With the decomposition of anaerobic microbe, biogas is generated with organic composition ultimately.

Input material of anaerobic digester can be divided into Case 1~5. As for TS concentration and COD concentration per each case, CASE 1 is 3.77%, 53,980mg/L, CASE 2 is 7.94%, 54,655mg/L, CASE 3 is 11.31%, 60,160mg/L, CASE 4 is 4.96%, 40,484mg/L and CASE 5 is 5.30%, 50,687mg/L.

After stabilization of anaerobic digest, as for biogas production and methane concentration per case, it was 166L/㎥·day, 67%, 389L/㎥·day, 66%, 554L/㎥·day, 63%, 165L/㎥·day, 64% and 213L/㎥·day, 62% respectively. As for methane concentration, concentration was analyzed in inverse proportion to organic matter loading.

As for organic matter removal rate, COD and VS removal rate by organic matter loading in CASE 1~5 was 64.27%, 61.86% at 0.54kg·vs/㎥·day, 58.81%, 84.08% at 1.29kg·vs/㎥·day, 67.94% 83.44% at 1.90kg·vs/㎥·day, 56.14%, 74.11% at 0.63kg·vs/㎥·day and 69.29%, 75.03% at 1.06kg·vs/㎥·day. During the whole operation period, the average organic matter removal efficiency of COD and VS was 62.68%, 75.41% having considerably higher removal efficiency. It demonstrates active microorganism decomposition by anaerobic digest.

(3) Feasibility of fermentation and digest byproduct
(A) Fertilizer
It is known that general pH fertilizer is pH 6~8. The scope of pH of fertilizer from aerobic oxidation fermentation was 7.00~8.90. Monthly fertilizer pH from April to December was 7.50, 7.00, 7.43, 7.79, 7.71, 7.68, 8.53 and 8.90 respectively. Except for November and December, all test groups had normal scope. Fertilizer in November and December had rather higher pH, which seemed the storage period of fertilizer was shorter than others. According to ‘Fertilizer standard’ if the germination rate is over 70, it can be used as fertilizer. As for the germination rate of byproducts from seed germination test from April to December, it was 140, 123, 113, 135, 83, 125, 72, 91 and 138 respectively. As the value is higher than 70, it can be used as fertilizer.

As a result of feasibility review of aerobic oxidation fermentation byproduct using circular chromatography, the fertilizer from April to August was fully decayed and fertilizer from September to December is post-decay period. Thus, fertilizer from September to December seems to have more preservation time.

As for heavy metal measurement of fertilizer, Cr exceeded basic value in April and July. As for Ni, it exceeded basic value from June to December. As such, Cr and Ni exceeded basic value. Therefore, it needs to take action to reduce such value according to ‘Fertilizer standard setting and designation.’

(B) Liquid fertilizer
According to a study on the regulatory improvement of necessary farmland for spraying liquid fertilizer, pH in under decay, mid-decay and full decay was 8, 8∼8.5 and 8.6∼9.

As for April, July and September, the scope of pH in full decay was slightly exceeded from suitable scope. Therefore, it was considered to comply with the full decay standard.

As for salinity, it was designated below 0.3% according to ‘Fertilizer standard setting and designation.’ As a result, except for liquid fertilizer in March, all liquid fertilizers showed slightly higher level than basic value.

As liquid fertilizer was generated from combined treatment of food waste in this test, salinity concentration was rather higher. Therefore, sufficient fermentation of liquid fertilizer is required.

(출처 : SUMMARY)

목차 Contents

• 표지 ... 1
• 제 출 문 ... 3
• 요 약 서 ... 4
• 요 약 문 ... 7
• SUMMARY ... 20
• 목차 ... 32
• 표목차 ... 34
• 그림목차 ... 36
• 1. 연구개발과제의 개요 ... 40
• 1-1. 연구개발 목적 ... 42
• 1-2. 연구개발의 필요성 ... 42
• 1-3. 연구개발 범위 ... 47
• 2. 국내외 기술개발 현황 ... 48
• 2-1. 유럽 바이오가스화 기술 현황 ... 50
• 2-2. 해외 소형 바이오가스화 기술 현황 ... 57
• 2-3. 국내 바이오가스화 기술 현황 ... 61
• 3. 연구수행내용 및 결과 ... 66
• 3-1. 연구개발내용(범위) 및 최종목표 ... 68
• 3-2. 연구개발 내용 및 결과 ... 69
• 3-3. 연구개발 결과 요약 ... 148
• 3-4 연차별 Pilot Plant 개선사항 ... 160
• 4. 목표달성도 및 관련분야 기여도 ... 182
• 4-1. 목표달성도 ... 184
• 4-2. 관련분야 기여도 ... 184
• 5. 연구결과의 활용계획 등 ... 186
• 5-1 연구활용계획 ... 188
• 6. 연구과정에서 수집한 해외과학기술정보 ... 202
• 6-1. 국외 혐기성 소화조 보급 현황 ... 204
• 6-2. 해외 기술개발 동향 ... 204
• 7. 연구개발결과의 보안등급 ... 208
• 8. NTIS에 등록한 연구시설·장비 현황 ... 212
• 9. 연구개발과제 수행에 따른 연구실 등의 안전조치 이행실적 ... 216
• 10. 연구개발과제의 대표적 연구실적 ... 220
• 11. 참고문헌 ... 224
• 부 록 ... 228
• 끝페이지 ... 238