The rising price of oil is hurting consumers all over the world. There is growing
interest in producing biofuels from non-food crops, such as sugarcane trash.
Lignocellulosic biomass (e.g., sugarcane trash) is an abundant, inexpensive, and
renewable resource. The patented MixAlco process is a cost-effective solution, which
does not require sterility or the addition of expensive enzymes to convert lignocellulosic
biomass to transportation fuels and valuable chemicals. In this study, the MixAlco
process was used to convert sugarcane trash to carboxylic acids under thermophilic
conditions.
Lime-treated sugarcane trash (80%) and chicken manure (20%) was used as the
feedstock in rotary 1-L fermentors. Ammonium bicarbonate buffer was used to mitigate
the effects of product (carboxylic acid) inhibition. Marine inoculum was used because of
the high adaptability of the mixed culture of microorganisms present. Iodoform solution
was added to inhibit methanogenesis.
Preliminary batch studies over a 20-day period produced 19.7 g/L of carboxylic
acids. Sugarcane trash had the highest average yield (0.31 g total acid/g VS fed) and highest average conversion (0.70 g VS digested/g VS fed) among the three substrates
compared.
Countercurrent fermentations were performed at various volatile solid loading
rates (VSLR) and liquid residence times (LRT). The highest acid productivity of 1.40
g/(L�d) was at a total acid concentration of 29.9 g/L. The highest conversion and yield
were 0.64 g VS digested/g VS fed and 0.36 g total acid/g VS fed, respectively. The
continuum particle distribution model (CPDM) was used to predict acid concentration at
various VSLR and LRT. The average error in between the predicted and experimental
acid concentration and conversion were 4.62% and 1.42%, respectively.
The effectiveness of several pretreatment methods was evaluated using the
CPDM method. The best-performing method was short-term, no-wash, oxidative lime
pretreatment with ball milling. At an industrial-scale solids loading of 300 g VS/L liquid,
the CPDM ?map? predicts a total acid concentration of 64.0 g/L at LRT of 30 days,
VSLR of 7 g/(L�d), and conversion of 57%. Also high conversion of 76% and high acid
concentration of 52 g/L are achieved at a VSLR of 4 g/(L�d) and LRT of 30 days.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2008-12-119 |
| Date | 14 January 2010 |
| Creators | Nachiappan, Balasubraman |
| Contributors | Holtzapple, Mark |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis |
| Format | application/pdf |
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