Hydrothermal process for bioenergy production from corn fiber and swine manure

With the soaring of ethanol production in the U.S., significant amount of corn fiber is left behind in the corn milling plants, which is more than the livestock feed manufacturing demands. To realize the maximum economic value of the corn fiber, the feasibility of ethanol production from corn fiber is extensively investigated. As one of the most costly steps, the pretreatment of biomass usually imposes a major impact on costs of ethanol and performance of the entire process. So, this study starts with the pretreatment of corn fiber at 20% (by weight) solid content collected from a wet corn milling with a batch reactor. A maximum of about 50% (by weight) of corn fiber can be solublized in water without addition of a catalyst. A simplified first-order reaction equation was used to model the decomposition of corn fiber and the production of glucose and xylose in a low acid environment. The highest yield (g/g dry matter of corn fiber) of glucose (6.1%) and the highest yield of xylose (8.7%) were obtained at 170°C and 40 minutes, and at 140°C and 50 minutes respectively. In this study a maximum 22.1% total sugar yield was observed at 140°C with small amounts of acetic acid, 5-(hydroxymethyl)-2-furaldehyde (HMF), and furfural found in the liquid products.;With the increasing concerns about the net energy balance of corn ethanol, food prices, and efficiency of the corn milling process, other types of liquid fuels such hydrocarbons from thermochemical conversion of biomass have become potentially promising. This study aims at investigating the oil-formation mechanism during hydrothermal conversion of swine manure. For the purpose of mechanism research, a new method was developed first and employed to meet the experimental requirements on materials balance. The swine manure was then converted in a batch reactor at 240-280°C and 10-120 minutes in the absence of a catalyst and the major products were classified into four categories, i.e., oil product, aqueous product, gas product, and solid residue. This study shows that about 33% of toluene soluble oil product can be obtained from swine manure at a temperature as low as 240°C and reaction time as short as 30 minutes. The material balance of experiments implies that the origin of the toluene soluble oil product may be closely related to the non-fiber components in swine manure such as lipid and protein. The separate leaching tests further convince that the toluene soluble oil yield almost proportionally increase with the lipid and protein content in swine manure. The product distributions at different reaction time imply that swine manure experiences a hydrolysis process where a significant fraction of biomass in swine manure decomposes to water-soluble organics, and then derived organics are subsequently gasified to form the gas product under hydrothermal conditions. Within the investigated ranges, the process conditions including reaction temperature, reaction time, initial and system pressure have no significant effect on the oil formation in hydrothermal conversion of swine manure.