초록
<P><B>Abstract</B></P><P>This paper presents laboratory results of biological production of hydrogen by photoautrotophic cyanobacterium <I>Anabaena</I> sp. Additional hydrogen production from residual <I>Cyanobacteria</I> fermentation was achieved by <I>Enterobacter aerogenes</I> bacteria. The authors evaluated the yield of H<SUB>2</SUB> production, the energy consumption and CO<SUB>2</SUB> emissions and the technological bottlenecks and possible improvements of the whole energy and CO<SUB>2</SUB> emission chain.</P><P>The authors did not attempt to extrapolate the results to an industrial scale, but to highlight the processes that need further optimization.</P><P>The experiments showed that the production of hydrogen from cyanobacteria <I>Anabaena</I> sp. is technically viable. The hydrogen yield for this case was 0.0114 kg<SUB>H2</SUB>/kg<SUB>biomass</SUB> which had a rough energy consumption of 1538 MJ/MJ<SUB>H2</SUB> and produced 114640 gCO<SUB>2</SUB>/MJ<SUB>H2</SUB>. The use of phototrophic residual cyanobacteria as a substrate in a dark-fermentation process increased the hydrogen yield by 8.1% but consumed 12.0% more of energy and produced 12.1% more of CO<SUB>2</SUB> showing that although the process increased the overall efficiency of hydrogen production it was not a viable energy and CO<SUB>2</SUB> emission solution. To make cyanobacteria-based biofuel production energy and environmentally relevant, efforts should be made to improve the hydrogen yield to values which are more competitive with glucose yields (0.1 kg<SUB>H2</SUB>/kg<SUB>biomass</SUB>). This could be achieved through the use of electricity with at least 80% of renewables and eliminating the unessential processes (e.g. pre-concentration centrifugation).</P> <P><B>Highlights</B></P><P>► Best H<SUB>2</SUB> photoautotrophic production yield is 0.128 kg<SUB>H2</SUB>/kg<SUB>biomass</SUB> (Ar + CO<SUB>2</SUB> + N<SUB>2</SUB> gas atmosphere; high intensity of light). ► Best H<SUB>2</SUB> production, energy and CO<SUB>2</SUB> balance is for Ar + CO<SUB>2</SUB> + 20% N<SUB>2</SUB> gas atmosphere and medium light intensity. ► H<SUB>2</SUB> yield can be increased 8% using the biomass leftovers but with 12% energy and CO<SUB>2</SUB> increase. ► Improving H<SUB>2</SUB> yield and using high shares of renewable electricity, allows significant decrease of energy and CO<SUB>2</SUB>. ► Cyanobacteria-based production of H2 must be further investigated to be sustainable relevant.</P>