• Korean Journal of Soil Science and Fertilizer
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• v.35 no.4
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• pp.216-222
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• 2002

Field experiments were conducted to investigate the effect of various cultural practices on methane($CH_4$) emission in tillage and no-tillage practice in a clayey paddy soil from 1998 to 2000. The factors evaluated in tillage and no-tillage methods were types of nitrogen fertilizers, application method of chemical fertilizers, rice straw application and cultivation method. Of the nitrogen fertilizers, the amount of $CH_4$ emission in ammonium sulfate plot was the lowest, regardless of tillage and the application method. 26.4~41.1% of reduction by ammonium sulfate compared with urea. But in no-tillage which have problem of poor rice yield than tillage, coated urea was more effective nitrogen fertilizer because that showed similar $CH_4$ emission and highest rice yield at 80% of dosage of nitrogen. No-tillage plot emitted lower $CH_4$ than tillage plot where the fertilizers were incorporated. On the contrary, no-tillage plot showed a little higher $CH_4$ emission compared with tillage plot for the surface application. When rice straw was applied, no-tillage practice reduced methane emission by 26.6% compared with tillage practice, but showing a little difference of 10.7% in no application. With cultivation method, no-tillage practice reduced methane emission 26.6% compared with tillage for the 30-d-old seedling transplanting. But for the dry direct seeding practice, no-tillage was a less effective because considerable amounts of rice straw incorporated by tillage were more decomposed aerobically in the soil and emitted as $CO_2$ to the atmosphere with flooding in no-tillage soil.

• Journal of the Korea Organic Resources Recycling Association
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• v.27 no.3
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• pp.81-89
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• 2019

The major problem encountered during the storage of pig slurry (PS) is the release of huge amounts of greenhouse gases (GHGs), which are dominated by methane ($CH_4$). To reduce this, concentrated sulfuric acid has been used as an additive to control the pH of pig slurry to 5.0-6.0. However, other low-risk substitutes have been developed due to some limitations to its use, such as corrosiveness, and hazards to animal and human health. In this study, sugar addition was proposed as an eco-friendly approach for limiting $CH_4$ emission from PS during storage. The pH of PS has been reduced from $7.1{\pm}0.1$ (control) to $5.8{\pm}0.1$, $4.6{\pm}0.1$, $4.4{\pm}0.1$, $4.1{\pm}0.1$, and $4.0{\pm}0.1$, by the addition of 10, 20, 30, 40, and 50 g sugar/L, respectively. Lactate, acetate, and propionate were detected as the dominant organic acids and at sugar concentration above 20 g/L, lactate concentration represented 42-72% (COD basis) of total organic acids. For 40 d of storage, $20.6{\pm}2.3kg\;CO_2\;eq./ton\;PS$ was emitted in the control. Such emission, however, was found to be reduced to $8.7{\pm}0.4$ and $0.4{\pm}0.1kg\;CO_2\;eq./ton\;PS$ at 10 and 20 g/L, respectively. Small amount of $CH_4$ from PS at 10 g/L was emitted until 30 d of storage, while for rest of storage period, it has increased to $8.7{\pm}0.4kg\;CO_2\;eq./ton\;PS$ ( 40% of the control) when methanogens have recovered by increasing pH to 7.0. By the end of storage, VS and COD removal in the control reached 24% and 27%, while their ranges reached 15-4% and 12-17% in the sugar added experiments, respectively. It was found that more than 90% of COD removal was done by aerobic biological process.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.109-112
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• 2007

유동층 반응기를 이용한 프로판의 촉매 분해는 $CO_2$를 방출하지 않고 수소를 생성하는 새로운 방식이다. 카본블랙을 이용한 프로판 분해는 메탄보다 상대적으로 분해가 잘되며, 같은 온도에서 전환률이 높기 때문에 수소 생성량이 더 많다. 촉매로 사용된 카본블랙은 반응 중 생성되는 탄소의 침적에도 불구하고 8시간 이상 촉매의 활성이 유지되어 전환율이 일정하게 유지되었다. 프로판 촉매 분해 실험은 상압에서 600 ${\sim}$ $800^{\circ}C$ 온도 변화 실험을 수행하였고, 가스 유속 변화는 2.0 ${\sim}$ $4.0U_mf$에서 실험 조건 변화에 따른 실험을 하였다. 온도, 유속 변화에 따른 생성 가스의 몰분율과 프로판 전환율을 분석하였다. 프로판 분해에 의해 생성된 기체는 수소뿐만 아니라 메탄, 에틸렌, 에탄, 프로필렌과 분해되지 않은 프로판이 배출되었다. 수소를 제외한 여타 가스들은 고온에서 실험을 할수록 몰비가 줄어들었다. 고온에서 프로판의 전환율과 수소 수득률이 증가하였다. 프로판 분해 실험 전후의 카본블랙 표면의 변화는 FE-TEM으로 관측하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.152.2-152.2
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• 2010

LFG는 매립된 폐기물 중 유기성분이 혐기성조건에서 미생물에 의해 분해가 되면서 발생하며, 이러한 매립지가스는 주변 지역의 자연 및 생활환경에 악영향을 미치기 때문에 소각 등의 방법으로 LFG를 처리하고 있다. 일반적으로 매립지로부터 발생하는 가스의 량은 폐기물 1톤 당 $150{\sim}250m^3$로서 매립 후 2~3년 후에 최대량이 발생하며 매립 후 20~30년 후까지 지속적으로 발생함으로 안정적인 LFG의 공급이 가능하며, 메탄함량이 50%인 경우 약 $5,000kcal/m^3$의 높은 발열량을 가지므로 대체에너지원으로 이용할 경우 환경적인 문제 해결 및 신재생에너지원으로 활용할 수 있다. LFG 자원화 할 경우 가장 안정적인 방안으로 발전 및 중질가스로 활용하는 것이나, 발전의 경우 최소 200만톤 이상의 매립용량을 갖추어야 경제적인 사업성을 확보할 수 있으며, 중질가스로 활용하는 경우 인근에 가스 수요처를 확보해야 하는 어려움이 있다. 만약 중 소규모의 매립장에서 발생하는 LFG를 안전하고 경제적인 조건으로 저장 및 수송할 수 있다면 중 소규모의 매립지에서 발생하는 LFG도 활용할 수 있을 것으로 기대되며, 안전하고 경제적인 저장과 수송기술을 통하여 발전이 아닌 중질가스로의 활용도 가능하게 될 것이다. 또한 여러 곳의 매립장에서 발생한 LFG를 한 곳으로 집중시켜 고질가스로 전환하는 설비비용을 절감할 수 있으며, 정제된 고질가스를 이용하여 발전보다 경제적인 자동차 연료나 도시가스로 활용할 수 있을 것이다. 본 연구에서는 LFG의 저장과 수송기술 중 GTS 기술을 통하여 저장과 수송에 제약이 크고 많은 비용이 소비되는 기체 상태의 에너지원을 하이드레이트화 시킴으로서 중 소규모 매립지에서 상대적으로 적은 비용으로 가스저장과 지상수송이 가능하게 할 수 있다. 본 연구의 결과로 LFG 에너지화 실증화 플랜트를 설계/제작 하였으며, 메탄+이산화탄소+물 하이드레이트 형성 실험 결과 4.56 Mpa, 277.2 K 조건에서 3시간을 한 사이클로 하는 공정운전을 가지는 것을 확인하였다. 이때 생성된 슬러리상의 하이드레이트를 고압으로 배출하여 펠릿으로 형성시켰으며, 형성된 하이드레이트 펠릿의 경우 92.27%의 메탄을 포함하는 것을 확인하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.1
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• pp.21-27
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• 2015

In order to meet the current emission regulations (EURO-6), it is necessary to significantly reduce $CH_4$ and $NO_X$ emissions. This study investigated the effect of a reduction in the valve overlap on the combustion and emission characteristics of a hydrogen-compressed natural gas engine under a part-load operating condition. The combustion and emission characteristics were analyzed for each fuel using the original camshaft and an altered camshaft with reduced valve overlap. The results showed that the thermal efficiency was decreased and the fuel flow was increased when using the altered camshaft. The $CO_2$ and $CH_4$ emissions were increased as a result of the reduced thermal efficiency. Under lean operating conditions, the $NO_X$ emission was decreased compared with one of the conventional camshaft. Thus, under the same fuels and operating conditions, it had a harmful influence on the emission characteristics and thermal efficiency.

• Korean Journal of Soil Science and Fertilizer
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• v.46 no.6
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• pp.502-509
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• 2013

To estimate greenhouse gas (GHG) emission, we established inventory of conventional rice cultivation from farmers in Gunsan and Iksan, Jeonbuk province in 2011~2012. This study was to calculate carbon footprint and to analyse the major factor of GHGs. We carried out a sensitivity analysis using the analyzed main factors of GHGs and estimated the mitigation potential of GHGs. Also we tried to suggest agricultural methods to reduce GHGs that farmers of this case study can apply. Carbon footprint of rice production unit of 1 kg was 2.21 kg $CO_2.-eq.kg^{-1}$. Although amount of $CO_2$ emissions is largest among GHGs, methane had the highest contribution of carbon footprint on rice production system after methane was converted to carbon dioxide equivalent ($CO_2$-eq.) multiplied by the global warming potential (GWP). Source of $CO_2$ in the cultivation of rice farming is incomplete combustion of fossil fuels used by agricultural machinery. Most of the $CH_4$ emitted during rice cultivation and major factor of $CH_4$ emission is flooded paddy field in anaerobic condition. Most of the $N_2O$ emitted from rice cultivation process and major sources of $N_2O$ emission is application of fertilizer such as compound fertilizer, urea, orgainc fertilizer, etc. As a result of sensitivity analysis due to the variation in energy consumption, diesel had the highest sensitivity among the energies inputs. If diesel consumption is reduced by 10%, it could be estimated that $CO_2$ potential reduction is about 2.5%. When application rate of compound fertilizer reduces by 10%, the potential reduction is calculated to be approximately 1% for $CO_2$ and approximately 1.8% for $N_2O$. When drainage duration is decreased until 10 days, methane emissions is reduced by approximately 4.5%. That is to say drainage days, tillage, and reducing diesel consumption were the main sources having the largest effect of GHG reduction due to changing amount of inputs. Accordingly, proposed methods to decrease GHG emissions were no-tillage, midsummer drainage, etc.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.173.2-173.2
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• 2011

대체 에너지 자원 중 폐기물의 소화 가스를 이용한 바이오가스 발전은 이산화탄소에 비해 온실효과 영향력에 21배에 해당하는 메탄가스를 연료로 사용하여 환경부하를 저감시키고 에너지를 생산한다. 바이오가스에 포함된 $H_2S$는 연소 후 $SO_2$형태로 발생되는데 $SO_2$는 수분과 반응을 하게 되면 $H_2SO_4$등의 강한 산성을 띄는 물질로 생성되어 배관 및 발전기에 손상을 주고 저온부식현상을 유발하게 하며, 동물이나 인체에 노출되면 기관지 수축현상이 일어나 호흡기에 영향을 주는 질식성을 띄는 가스이다. 축산바이오가스에 포함된 $H_2S$의 함유량과 가스엔진의 연소 시 배출되는 $SO_2$ 배기가스 성분의 관련성을 검증하기 위해 60-65%의 $CH_4$와 30-35%의 $CO_2$ 성분의 바이오가스를 50kW급 발전기에서 사용하였고 연소 후 배출되는 가스 성분을 분석하였다.

• Journal of the Korea Organic Resources Recycling Association
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• v.23 no.4
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• pp.40-51
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• 2015

This study is to estimate the viability of aerobic stabilization technology for reducing greenhouse gas (GHG) emissions from landfills in Korea. In this study, methane emissions were estimated by applying Landfill gas estimation model (LandGEM) to Y landfill in Korea. By comparison of an anaerobic condition (baseline) and an aerobic condition, the amount of $CO_2eq$ savings was calculated. The $CO_2eq$ savings take place inside the landfilled waste during aeration due to the conversion of previously anaerobic biodegradation to aerobic processes, releasing mainly $CO_2$. It was demonstrated that 86.6% of the total GHG emissions occurring under anaerobic conditions could be reduced by aerobic stabilization technology. This means the aerobic stabilization technology could reduce environmental contamination through early stabilization and GHG emissions considerably at the same time. Therefore, the aerobic stabilization technology is one of the optimal technologies that could be employed to domestic landfill sites to achieve sustainable landfill.

• Journal of the Society of Disaster Information
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• v.15 no.4
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• pp.560-569
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• 2019

Purpose: Greenhouse gases are one of the major causes of global warming, a global disaster. This study aims to calculate road sector greenhouse gas emissions more precisely than conventional methods. Method: Currently, the average speed of a vehicle is used to calculate greenhouse gas emissions. In this study, GHG emissions are calculated using the speed of individual vehicles and compared with current methods. Result: It was confirmed that the existing emission estimation method underestimated about 15% in the case of carbon dioxide, about 1% in the case of nitrous oxide, and about 1% in the case of methane. Conclusion: Current methods of estimating greenhouse gas emissions were developed before 2000 and were developed to meet the limits of available data. However, with the advancement of technology, the quality of available data is now high, and new emissions estimation methods are needed. Therefore, in this study, we propose a method for estimating the velocity-based greenhouse gas emissions of individual vehicles as a more accurate method for calculating greenhouse gas emissions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.41-46
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• 2018

In this research, numerical analysis was performed to determine the effects of hydrogen on biogas combustion for homogeneous charged compression ignition (HCCI) engines. The target engine specifications were a 2300cc displacement volume, 13:1 compression ratio, 15kW of electricity, and 1.2 bar boost pressure. The engine speed was fixed to 1800rpm. By varying the excess air ratio and hydrogen contents, the cylinder pressure, nitric oxide, and carbon dioxide were measured as a function of the hydrogen contents. According to preliminary studies related to the reaction mechanism for methane combustion and oxidation, a GRI 3.0 mechanism as the base mechanism was selected for HCCI combustion calculations describing the detailed reaction mechanism. By adding hydrogen, NO was increased while $CO_2$ was decreased. The cylinder pressure was also increased, having advanced timing for the maximum cylinder pressure and pressure rise region. Furthermore, lean operation limits were extended by adding hydrogen to the HCCI engine.