Prospects for expanded utilization of biogas in Germany
Introduction
Germany is currently the world leader in the deployment of biogas technology. In the last decade, the number of plants increased from 370 in 1996—3891 in 2008 [1]. The electrical power supplied to the national grid from biogas plants also increased from 60 kWel in 1999 to 350 kWel in 2008 on average [1], mainly due to implementation of the Renewable Energy Sources Act (EEG). Under the EEG, there is payment for supply of electricity from renewable resources [2], [3]. The biogas plants, with a total output of approximately 1400 MWel in 2008 produce about 10 TWh electricity per annum, which accounts for about 1.6% of the total demand [4], but the technical potential is estimated to be almost 60 TWh per annum [5]. Biogas is predominantly used for Combined Heat and Power (CHP) and in electricity generation and feed-in to the national grid [6]. A scheme that allows for injection of bio-methane (enriched biogas) into the natural gas grid is also in place, which has expanded biogas utility [7]. It is estimated that, optimisation of available feedstock for decentralised plants, has potential to further enhance biogas utilization [8].
Like with any other renewable energy resources, judicious deployment of biogas technology will contribute to reduction in greenhouse gas (GHG) emissions and air pollution, due to the expected reduction of the use of fossil fuels. Fig. 1 compares GHG emissions associated with different electricity production options from a life-cycle perspective for biogas, fossil fuels, and other renewable energy sources. The calculated negative emissions for biogas-CHP are explained by the substitution of oil fuel with biogas. The underpinning anaerobic digestion (AD) process can also be used for waste management and enhancement of soil fertility through spreading of the spent feedstock—the digestate. The requisite organic feedstock are locally available and renewable, therefore, with the right policy incentives, security of energy supply could be enhanced. The deployment of biogas technology created about 10,000 jobs in Germany in 2007 [9], and contributed to economic growth with the increased export of the technology. However, the competitiveness of biogas plants has lately been impeded by highly variable prices of feedstock like corn, and the decreasing government subsidy. Implementation and operation of biogas plants is a complex process; it requires planning permission from the municipal or regional authorities, rigorous feedstock supply logistics, AD process control, marketing of electricity/biogas, and disposal of the digestate. Environmental awareness of the populace and environmental protection regulations also strongly influence their feasibility.
The objective of this study was to assess the prospects for expanded deployment of biogas technology in Germany, by identifying key factors affecting the complete chain of processes in plant implementation from the planning process, installation and commissioning, to feedstock supply, and biogas production and utilization. The stepwise methodology included:
- (1)
Description of state-of-the-art and demarcation of elements biogas systems into feedstock supply logistics, biogas production and treatment of spent feedstock—the digestate, and biogas utilization elements.
- (2)
Literature review to compile quantified descriptors of the elements of production system, including feedstock types, deployed biogas production technologies, biogas utilization for electricity generation and transport fuel, and sustained utilization of the digestate including safe disposal option.
- (3)
Economic analysis was carried out for biogas production from different feedstock, including feedstock supply considerations and handling of the digestate on basis of industry data. Evaluation of different biogas utilization pathways based on energy audit of biogas production systems was also implemented.
- (4)
Analysis and discussion of active policy considerations entailing the incentives and barriers to biogas production and utilization with impacts on the potential for expanded biogas utilization. These were benchmarked against three selected ‘biogas-peer’ countries including, Italy, Sweden and Switzerland, as an intended continuous process by which Germany will seek to challenge its technology and practice leading to sustainable utilization of biogas and therefore enhanced contribution to renewable energy resource mix.
In all cases, the data used was derived from peer-reviewed scientific literature and technical reports with relation to current practice in biogas production and utilization technology in Germany, and corroborated on the basis of working experience of the authors, and through personal communication with selected experts in Germany. The policy issues covered are therefore focused on specific areas of weakness in the integrated biogas utilization system, where technical and economically viable potential for optimisation exist. The biogas peer countries were selected on the basis of; strategy for sustainable feedstock initiatives and existing high feedstock potential from agro-industry (Switzerland, Italy) [10], [11], pioneering and extensive use of bio-methane for transportation fuel (Sweden) [12], [13], and high feed-in-tariffs for biogas coupled with tradable green certificates for electricity generated from renewable energy sources (Italy) [11].
Section snippets
State-of-the-art in biogas energy systems
Biogas is produced by AD of organic feedstock, the most common being; animal waste and crop residues, dedicated energy crops, domestic food waste, and Municipal Solid Waste (MSW). Integrated processes include (Fig. 2), feedstock supply and pre-treatment; AD, gas treatment and utilization, and recovery, pre-treatment and use of digestate. Biogas consists of 50–75% methane (NH4), 25–45% carbon dioxide (CO2), 2–7% water (H2O) at 20–40 °C, up to 2% nitrogen (N2), trace of oxygen (O2), and less than
Production potential
The exuberance for complete replacement of fossil fuels by renewable energy resources, e.g. biomass, is not supported by maturity of the underpinning science, engineering and technology [20]. However, it is realistic that potential expansion in renewable energy utilization will depend on technology improvement and adoption of policies that enhance economics of individual components of the selected renewable energy resource mix [21]. The outcome of a comparative analysis of biogas yield and
Salient policy issues on potential for expanded utilization
Fuel extraction, energy utilization and transportation accounts for 80% of all GHG emissions in the European Union (EU) [45]. It is estimated that, with the current energy and transport policies in the region, CO2 emissions will increase by 5% by 2030 and global emissions by 55% [46]; hence, the current energy policies are unsustainable. Also, it is estimated that EU's energy import dependence will increase from current 50% of total consumption, to 65% in 2030, of which the increased reliance
Conclusions and recommendations
Biogas technology could make a significant contribution towards meeting the national targets for renewable energy deployment in Germany, but only about 10% of the total technical potential is currently utilized. This suggests that existing technology and policy drivers and the accompanying incentives need to be enhanced. Although the range of government supported investment grants and subsidies provided under the Renewable Energies Act (EEG) and energy tax reliefs are available, significant
Acknowledgements
This study was funded under the Charles Parsons Energy Research Programme (UCD) of Science Foundation Ireland (SFI), and the Dissertation Fellowship of the Universities of Applied Science in Bavaria, Germany.
Martina Poeschl is a PhD student in the Charles Parsons Energy Research Programme of Science Foundation Ireland, University College Dublin. Her research area of interest is in biogas technology; specifically, feedstock-to-biogas conversion, optimisation of AD systems and energy conversion, and environmental impact assessment and mitigation using LCA methodology.
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Martina Poeschl is a PhD student in the Charles Parsons Energy Research Programme of Science Foundation Ireland, University College Dublin. Her research area of interest is in biogas technology; specifically, feedstock-to-biogas conversion, optimisation of AD systems and energy conversion, and environmental impact assessment and mitigation using LCA methodology.
Shane Ward is Professor of Biosystems Engineering, and Head of School of Agriculture, Food Science & Veterinary Medicine at University College Dublin. He was founder and director of Bioresources Research Centre (BRC) at the university, with responsibility for a large research group dealing with a variety of aspects of the agri-food and bioresource industries. He was formerly Head of Production Research at the R&D Department of Bord na Mona (Irish Peat Board). Prof Ward is Fellow of the Institution of Engineers of Ireland and has over 28 years of experience in research and technology development. He has established several research units some of which are in partnerships with industry. A former Chairperson of its Agri-Food Division of the Institution of Engineers of Ireland, he was responsible for the promotion and development of the agri-food and bioresource industry among professional engineers and the industry. He has had a strong track record in Cooperation Projects that include collaboration with industry. Prof. Ward has in excess of 150 peer-reviewed research publications, and has supervised in excess of 40 Masters and PhD students. His current research team comprises ca. 30 researchers (Masters, PhDs and Post-Doctoral fellows), working on a variety of bio-resource projects.
Philip Owende is a senior research fellow in the Charles Parsons Energy Research Programme of Science Foundation Ireland, University College Dublin. His research area of interest is in biomass-to-energy systems covering energy feedstock production, pre-treatment standards, conversion technologies, and environmental impact assessment. Dr. Owende has published 40 scientific articles in peer reviewed journals, over 30 international conference papers, and three book chapters.