Biomedical subjects

M T Holtzapple

Publications and source records attributed to M T Holtzapple.

6 recordsLinked to original sources

PubMed2001

Oxidative lime pretreatment of high-lignin biomass: poplar wood and newspaper.

Lime (Ca[OH]2) and oxygen (O2) were used to enhance the enzymatic digestibility of two kinds of high-lignin biomass: poplar wood and newspaper. The recommended pretreatment conditions for poplar wood are 150 degrees C, 6 h, 0.1 g of Ca(OH)2/g of dry biomass, 9 mL of water/g of dry biomass, 14.0 bar absolute oxygen, and a particle size of -10 mesh. Under these conditions, the 3-d reducing sugar yield of poplar wood using a cellulase loading of 5 filter paper units (FPU)/g of raw dry biomass increased from 62 to 565 mg of eq. glucose/g of raw dry biomass, and the 3-d total sugar (glucose + xylose) conversion increased from 6 to 77% of raw total sugars. At high cellulase loadings (e.g., 75 FPU/g of raw dry biomass), the 3-d total sugar conversion reached 97%. In a trial run with newspaper, using conditions of 140 degrees C, 3 h, 0.3 g of Ca(OH)2/g of dry biomass, 16 mL of water/g of dry biomass, and 7.1 bar absolute oxygen, the 3-d reducing sugar yield using a cellulase loading of 5 FPU/g of raw dry biomass increased from 240 to 565 mg of eq. glucose/g of raw dry biomass. A material balance study on poplar wood shows that oxidative lime pretreatment solubilized 38% of total biomass, including 78% of lignin and 49% of xylan; no glucan was removed. Ash increased because calcium was incorporated into biomass during the pretreatment. After oxidative lime pretreatment, about 21% of added lime could be recovered by CO2 carbonation.

Biomass↗

PubMed2001

Laboratory method for high-solids countercurrent fermentations.

Equipment and procedures were developed to study the conversion of lignocellulosic biomass to carboxylic acids using high-solids countercurrent fermentations. Countercurrent fermentations of cattle manure yielded a rapid fermentation (maximum 2.98 g of total acid/[L x d]) with high acid concentrations (maximum of 32.5 g of total acid/L), but the acid yield tended to be low (maximum of 0.24 g of total acid/g of volatile solids). Countercurrent fermentations of a mixture of 80% municipal solid waste/20% sewage sludge fermented more slowly (maximum of 1.98 g of total acid/[L x d]) with a lower acid concentration (maximum of 26.5 g of total acids/L), but higher acid yields were achieved (maximum of 0.34 g of total acid/g of volatile solids).

Animals↗

PubMed2000

Fundamental factors affecting biomass enzymatic reactivity.

Poplar wood was treated with peracetic acid, KOH, and ball milling to produce 147 model lignocelluloses with a broad spectrum of lignin contents, acetyl contents, and crystallinity indices (CrIs), respectively. An empirical model was identified that describes the roles of these three properties in enzymatic hydrolysis. Lignin content and CrI have the greatest impact on biomass digestibility, whereas acetyl content has a minor impact. The digestibility of several lime-treated biomass samples agreed with the empirical model. Lime treatment removes all acetyl groups and a moderate amount of lignin and increases CrI slightly; lignin removal is the dominant benefit from lime treatment.

Acetylation↗

PubMed1999

Biomass conversion to mixed alcohol fuels using the MixAlco process.

The MixAlco process is a patented technology that converts any biodegradable material (e.g., sorted municipal solid waste, sewage sludge, industrial biosludge, manure, agricultural residues, energy crops) into mixed alcohol fuels containing predominantly 2-propanol, but also higher alcohols up to 7-tridecanol. The feedstock is treated with lime to increase its digestibility. Then, it is fed to a fermentor in which a mixed culture of acid-forming microorganisms produces carboxylic acids. Calcium carbonate is added to the fermentor to neutralize the acids to their corresponding carboxylate salt. The dilute (approximately 3%) carboxylate salts are concentrated to 19% using an amine solvent that selectively extracts water. Drying is completed using multi-effect evaporators. Finally, the dry salts are thermally converted to ketones which subsequently are hydrogenated to alcohols. All the steps in the MixAlco process have been proven at the laboratory scale. A techno-economic model of the process indicates that with the tipping fees available in New York (126 dollars/dry tonne), mixed alcohol fuels may be sold for 0.04 dollars/L (0.16 dollars/gal) with a 60% return on investment (ROI). With the average tipping fee in the United States rates (63 dollars/dry tonne), mixed alcohol fuels may be sold for 0.18 dollars/L (0.69 dollars/gal) with a 15% ROI. In the case of sugarcane bagasse, which may be obtained for about 26 dollars/dry ton, mixed alcohol fuels may be sold for 0.29 dollars/L (1.09 dollars/gal) with a 15% ROI.

Journal Article↗

PubMed1989

Analysis of an algae-based CELSS. Part 1: model development.

A steady state chemical model and computer program have been developed for a life support system and applied to trade-off studies. The model is based on human demand for food and oxygen determined from crew metabolic needs. The model includes modules for water recycle, waste treatment, CO2 removal and treatment, and food production. The computer program calculates rates of use and material balance for food. O2, the recycle of human waste and trash, H2O, N2, and food production supply. A simple non-iterative solution for the model has been developed using the steady state rate equations for the chemical reactions. The model and program have been used in system sizing and subsystem trade-off studies of a partially closed life support system.

Ammonia↗

PubMed1989

Analysis of an algae-based CELSS. Part 2: options and weight analysis.

Life support components are evaluated for application to an idealized closed life support system which includes an algal reactor for food production. Weight-based trade studies are reported as "break-even" time for replacing food stores with a regenerative bioreactor. It is concluded that closure of the life support gases (oxygen recovery) depends on the carbon dioxide reduction chemistry and that an algae-based food production can provide an attractive alternative to re-supply for longer duration missions.

Ammonia↗