Storage and pre-treatment of substrates for biogas production - The Biogas: Science, Production and Applications - page 83

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Storage and pre-treatment of substrates for
biogas production

GU ¨ NTHER BOCHMANN and LUCY F.R.
MONTGOMERY, University of Natural Resources
and Life Sciences, Austria

DOI: 10.1533/9780857097415.1.85

Abstract: Biogas substrates are typically moist, which can make them
difficult to store because bacteria and mould can grow on them. Ensiling,
which involves the production of acid by lactic acid bacteria, is often
used to preserve crops cheaply. Biogas substrates are also often fibrous,
which can make them difficult to mix and means that some of their
energy is locked up within the fibres. Different pre-treatment
technologies are being investigated to access the energy in these fibres, to
increase the rate of biogas production and to improve the mixing
qualities of the substrates. Pre-treatment technologies are based on three
principles: physical (including mechanical shear, heat, pressure and
electric fields), chemical (acids, bases and solvents) and biological
(microbial and enzymatic). Combinations of these principles are also
used, including steam explosion, extrusion and thermo-chemical
processes. Although many of these processes have been investigated at
small scale, few have been analysed at large scale in un-biased studies.
Many of these techniques are associated with high energy input (e.g.
mechanical and heat pre-treatment), high equipment costs (e.g.
mechanical systems where the blades erode) or use large volumes of
chemicals (e.g. alkali pre-treatment). Different pre-treatment technologies
work better with different substrates, and more research is required in
this field to understand which combinations are worthwhile. This chapter
describes some of the common pre-treatment technologies along with
some advantages and disadvantages.

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Key words: biogas, anaerobic digestion, pre-treatment, ensiling, anaerobic
digestion analysis.