| 摘要 | ABSTRACT
1. Research Purpose
Going forward, renewable energy sector is expected to see a rapid increase in deployment, especially given that expanded market creation policies focused on bioenergy would be implemented. Such development and use of bioenergy has, however, raised concerns over associated negative social, economic, and environmental implications including a severe competition with food production (a significant impact on food prices), deforestation, etc.
Against the background, the importance of the concept of ��sustainable use and development�� has already been highlighted at a global level. The concept is defined as offsetting or minimizing causes of such implications while extending the use and development of renewable energy. In particular, under the Sustainability Criteria in the Renewable Energy Directive (RED) adopted by the EU in 2009, only the bioenergy produced and used in accordance with the Criteria will be counted towards the share of renewable energy target of member countries.
One of the most significant quantitative indicators of the Sustainability Criteria is the reduction effect of Green House Gas (GHG) emission generated through the use of bioenergy. In other words, the Criteria is deemed to be fulfilled only when the percentage reduction of GHG emissions generated through the use of bioenergy instead of a fossil fuel is above a certain threshold in addition to meeting other standards.
In consideration of the global concerns and trend, it is recommended that Korea consider ways to produce and deploy bioenergy in a sustainable manner as well as being prepared for it. The objective of this research is to assess whether the bioenergy is developed and used sustainably in Korea, and to provide suggestions for improving the environmental performance of the whole life cycle of the development and use of bioenergy based on the assessment.
For the assessment of the sustainability, this research used the Life Cycle Assessment (LCA) methodology adopted by the EU RED. In consideration of the time constraint, this research specifically focused on the biogas among all bioenergy sources. It collected data related with the whole life cycle of six biogas plants in Korea. Based on the data gathered, it undertook LCA to assess sustainability of biogas in heat, power generation, and transport sectors.
2. Summary
Biogas refers to a gas mixture comprised primarily of methane (CH4) produced by breakdown of organic matter by microorganism in the absence of oxygen (under anaerobic condition).
As of the end of 2010, the number of biogas plants which have been installed and in operation reached 50 in Korea, with 2 newly installed, 3 halted operation, 2 converted into combined treatment facilities, and 2 added to existing facilities. Total number increased by one plant compared to 2009. 40 plants out of the 50 in operation were installed before 2007.
In the same year, the total biogas production came to 157,074,000m3, a 12.4% increase from the previous year, with sewage sludge accounting for 45% of the total production, followed by combined treatment with around 43.7%, food waste facility 7.0%, food waste leachate facility 4.2%, and animal manure facility 0.3%, each displaying a considerable difference in output depending on the method of production.
This research defined the goal and scope of the LCA for the six biogas plants, followed by compilation of information and Life Cycle Inventory Analysis, and the calculation of GHG emissions throughout the whole life cycle. In addition, GHG emissions of fossil fuels, which are replaced by biogas, in heat, electricity generation, and transport sectors were calculated to be compared against those of the biogas to measure the emission reduction effects.
With regard to the heat sector, total GHG emissions of LNG, bunker-C oil and bituminous coal used for industrial boilers were calculated for comparison, which showed that the biogas in Korea displayed 90%~94% of emission reduction rate.
Concerning the electricity generation sector, the GHG emissions generated through electricity production were calculated, using the national Life Cycle Inventory Data Base, for comparison, which proved that the emission reduction rate reached between 76% and 86% by plant.
With respect to the transport sector, the GHG emissions of LNG, LPG, diesel, and gasoline were calculated for comparison; the biogas showed 83%~95% of emission reduction rate when compared against the LNG, and 75%~95% against other fossil fuels.
The usage stage showed far more drastic emission reduction effect than the production stage, which is deemed to reflect the advantage of carbon-neutral nature of biogas. As a result, in all sectors of heat, power generation, and transport, Korea is assessed to fulfill the threshold value of 35% of green house gas savings as compared to fossil fuels directed by the EU Sustainability Criteria (a 50% threshold from 2017 on, and a 60% from 2018).
According to the Renewable Energy Directive of EU, all CNG-types of biogas showed total 73% of savings rate, with biofuel generated from dry manure recording the highest rate of 86%.
In comparison, Korea displayed relatively high savings rate in the transport sector. However, direct comparison with the EU is deemed irrelevant due to differences in system boundaries and GHG emission of comparable fossil fuels.
3. Policy Implications
Based on the analysis of this research, suggestions for enhancing environmental performance of Korea's biogas production plants, the infrastructure for LCA analysis, and Sustainability Criteria are as follows.
First, focus needs to be given to enhancing energy efficiency in the production stage at first in order to improve the environmental performance of biogas plants. Given that the production stage accounted for 92% of the GHG emission among all stages including pre-treatment, production, and so on, the impact of the improvement is expected to be felt the most.
Second, it is recommended that new facilities be operated independently if possible. According to the comparison of the six facilities under this research, independently run facilities tended to emit lower level of green house gas than those run together in connection with waste treatment facilities.
Third, with respect to biogas plants which are being newly installed, environmental load could be reduced by locating them adjacent to facilities simultaneously treating raw materials for input and wastes output generated after the digestion processes. If the waste treatment facilities for input and output are separately located, the biogas plant is recommended to be placed close to the treatment facility for raw materials or collection facility instead of the waste treatment facility for output for reducing the environmental load.
Fourth, digestion efficiency can be improved and environmental load can be reduced if facilities processing raw materials with low organic density mix and co-digest raw materials with high organic density. However, this co-digestion process has not been expanded due to a difficulty associated with meeting the water quality criteria by the effluent derived from the digestion process. In addition, the fact that relevant governmental agencies and systems are dispersed by type of waste is also served as an impediment to the implementation of co-digestion.
Five, efficiency of existing facilities needs to be enhanced by minimizing simple incineration of excess biogas and optimizing the use of resources. Four out of the six plants were found to be incinerating excess biogas; one of them incinerates 11% of biogas produced. In addition, 21% of biogas produced by the plants in Korea were found to be incinerated simply. Among them, animal manure and food waste leachate facilities displayed low usage rate of 12% and 49% respectively.
Six, a measurement system needs to be in place by process or by facility throughout the whole life cycle of biogas plants for the management of information and data. For future economic and environmental assessments which will serve as a basis for the Sustainablity Criteria of biogas facilities, establishment of the measurement system by facility is deemed essential.
Lastly, infrastructure needs to be improved for the LCA of bio-energy sector at the national level. To that end, it is advised that the national LCI DB define fossil fuels (in the form of a single type or a type of basket) which can be replaced by renewable energy in the heat and transport sectors, and based on the definition, emission coefficients need to be calculated and recorded. More fundamentally, a comprehensive guideline for the LCA method which can be applied to renewable energy sources needs to be developed. Although Korea has a national guideline for environmental performance assessment in place, a specifically designed methodology is needed to suit a particular policy as specified by the EU RED. |
