Agricultural biogas production in Germany - from practice to microbiology basics

Bernhard Munk,Michael Lebuhn,Mathias Effenberger

doi:10.1186/2192-0567-4-10

Bernhard Munk, Michael Lebuhn + Show 1 more

Open Access

https://doi.org/10.1186/2192-0567-4-10

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Abstract

Worldwide, anaerobic digestion for sanitation and utilization of the produced biogas as energy carrier have a long-standing history. Concomitantly, digested residues from biogas plants are utilized as valuable fertilizers in crop production. In Germany, guaranteed prices for electricity generated from renewable sources pushed the number of biogas plants from about 140 in 1992 to about 7,720 by the end of 2013, and the share of electricity supply from biogas close to 4.5%. In the midterm, biogas is given considerable potential to fill up the residual load from electricity generation based on wind and photovoltaic. In this review, we give an overview of the state-of-the-art of biogas technology for energy supply from agricultural inputs, based mainly on the situation in Germany. Focus is placed on the monitoring and control (M&C) of biogas plants as a means of meeting the growing demands for productivity and reliability of biogas supply. We summarize prominent factors for the stability and productivity of the anaerobic digestion (AD) process, and present latest findings about molecular biology tools, bioindicators, the ‘metabolic quotient’ and cDNA/DNA ratios for process analysis. In view of the large diversity of agricultural biogas installations, we discuss the cost-benefit ratio of M&C effort and equipment. In the light of the transformation of the energy system in Germany towards renewable sources (‘Energiewende’), we give an outlook on prospects and concepts for the future role of biogas technology in agriculture and energy supply. We also address recent misguided developments, as the sustainable development of biogas technology in agriculture can only be realized within the ecological, economical, and social boundaries of underlying agro-ecological systems.

Highlights

A brief history of biogas production is compiled from information publicly accessible in the internet [3,4,5,6,7]
It was found that the amounts of flammable gas and decaying organic matter were correlated, that the process developed under anaerobic conditions and that the flammable component of the gas produced in anaerobic digestion of cattle manure was methane
This review shows that agricultural biogas technology in Germany has been subject to quite a lot of scientific research and technological progress, there is still significant potential for optimization

Summary

Introduction

A brief history of biogas production is compiled from information publicly accessible in the internet [3,4,5,6,7]. Research on ammonia inhibition was revived in AD of energy crops, with the increased utilization of (clover) grass silage for biogas production due to reduced dairy farming (cf ‘Agro-environmental and social aspects’ section).

Results

Conclusion