Prospects for expanded utilization of biogas in Germany

Abstract

The prospects for expanded utilization of biogas systems in German was analysed, by identifying the operational and policy factors affecting the complete chain of processes from implementation process for biogas plants, through to biogas production and utilization. It was found that the Renewable Energies Act (EEG) and energy tax reliefs provide bases for the support of expanded utilization. Upgrading of biogas to natural gas quality for utilization in the transportation sector was arguably the most promising technology that could support rapid utilization expansion. Sustainable deployment of biogas systems in light of the unstable feedstock prices and availability, and the need for subsidy-free operation in the long term requires; enhancement of feedstock flexibility and quality characteristics to maximise gas yield, and optimisation of the anaerobic digestion process management. Assessment of energy balance and potential environmental impacts of the integrated process chain provides a holistic assessment of sustainability. The results also support the development and foster of policies and framework for development of biogas as environmentally friendly energy resource, among a mix of renewable energy sources, hence, compete favourably with fossil fuels to enhance the prospects for expanded utilization.

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 kW_el in 1999 to 350 kW_el 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 MW_el 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:

• 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.

• 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.

• 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.

• 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].