초록
<P><B>Abstract</B></P> <P>The concept of year-round biogas production to increase the capacity factor of anaerobic digestion (AD) plants in sugarcane biorefineries was investigated for the first time in semi-continuous feeding mode. To simulate the use of sugarcane vinasse during the sugarcane season and sugarcane filter cake (SFC) during the off-season period, a two-stage reactor system based on an acidogenic continuous stirred-tank reactor (1st stage) followed by solid–liquid separation and an upflow anaerobic sludge blanket (UASB) reactor (2nd stage) to convert the COD-rich liquid fraction into biogas was operated. Additionally, to optimize the biogas production from SFC, the effects of its thermo-chemical pre-treatment on AD were investigated in a parallel reactor set-up. The saponification effect provided by autoclaving the substrate with sodium hydroxide improved the hydrolysis/fermentation of SFC in the acidogenic reactor, which in turn resulted in a 28% higher volumetric methane production in the methanogenic reactor (<I>p</I> < 0.05). However, the methane yields observed during operation of the two-stage reactor system were markedly lower than previously found in biochemical methane potential tests using SFC. In this case, the feed-in with low suspended solids required by UASB reactors prevented the utilization of the non-hydrolyzed/fermented solid fraction of SFC (> 60% of the substrate’s methane potential). Nevertheless, the capacity factor of the AD plants in sugarcane biorefineries could be increased from 0.55 up to 0.69 when considering a 200 d a<SUP>−1</SUP> sugarcane season (0.66–0.83 for a longer season of 240 d a<SUP>−1</SUP>), representing an increase of 25.7%. The average capacity factor for biogas combined heat and power and upgrading units of around 0.91 (8000 h a<SUP>−1</SUP>) would be reached if further developments could improve the solubilization of non-hydrolyzed/fermented solids or alternatively allow their direct use in the methanogenic reactor.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A concept for year-round biogas production from sugarcane waste was developed. </LI> <LI> A thermo-chemical pre-treatment improved VMP (p < 0.05) from SFC during off-season. </LI> <LI> The pre-treatment method increased process stability in the 2nd stage UASB reactor. </LI> <LI> Most of the methane potential (>60%) was found in the form of solid acidified SFC. </LI> <LI> The proposed AD concept increased the capacity factor by up to 25.7%. </LI> </UL> </P>