Kiran L. Kadam

Availability of corn stover as a sustainable feedstock for bioethanol production.

The amount of corn stover that can be sustainably collected is estimated to be 80-100 million dry tonnes/yr (t/yr), a majority of which would be available to ethanol plants in the near term as only a small portion is currently used for other applications. Potential long-term demand for corn stover by non-fermentative applications in the United States is estimated to be about 20 million dry t/yr, assuming that corn stover-based products replace 50% of both hardwood pulp and wood-based particleboard, and that 50% of all furfural production is from corncobs. Hence, 60-80 million dry t/yr of corn stover should be available to fermentative routes. To achieve an ethanol production potential of 11 billion L (3 billion gal) per year (a target level for a non-niche feedstock), about 40% of the harvestable corn stover is needed. This amount should be available as long as the diversion of corn stover to non-ethanol fermentative products remains limited.

Development and Validation of a Kinetic Model for Enzymatic Saccharification of Lignocellulosic Biomass

A multireaction kinetic model was developed for closed‐system enzymatic hydrolysis of lignocellulosic biomass such as corn stover. Three hydrolysis reactions were modeled, two heterogeneous reactions for cellulose breakdown to cellobiose and glucose and one homogeneous reaction for hydrolyzing cellobiose to glucose. Cellulase adsorption onto pretreated lignocellulose was modeled via a Langmuir‐type isotherm. The sugar products of cellulose hydrolysis, cellobiose and glucose, as well as xylose, the dominant sugar prevalent in most hemicellulose hydrolyzates, were assumed to competitively inhibit the enzymatic hydrolysis reactions. Model parameters were estimated from experimental data generated using dilute acid pretreated corn stover as the substrate. The model performed well in predicting cellulose hydrolysis trends at experimental conditions both inside and outside the design space used for parameter estimation and can be used for in silico process optimization.

Rice straw as a lignocellulosic resource: collection, processing, transportation, and environmental aspects.

As open-field burning of rice straw is being phased out in California, rice growers and government agencies are looking for new rice straw uses. The amount of rice straw that may be available as a feedstock ranges from 1.0 to 1.4 million t yr−1. Irrespective of its actual use as a source of raw material for liquid fuel, fiber, or power generation, a study of issues dealing with its harvest is needed. This paper reviews possible harvesting systems and provides an analysis of operating parameters such as straw moisture, density, storage, and optimal number of transport units. A case study of rice straw production in the Sacramento Valley was conducted, which illustrates that 550 t d−1 of straw can be accessed at an estimated net delivered cost of about US

Power plant flue gas as a source of CO2 for microalgae cultivation : Economic impact of different process options

20/t (dry), which is generally considered attractive for an ethanol feedstock. Gainfully utilizing this residue can ease the disposal problem facing agricultural operations in the State. Furthermore, the potential environmental benefits of diverting rice straw from open-field burning will be to significantly reduce criteria air pollutants such as VOC, SOx, NOx, and PM10, and also silica emissions, which are not specifically monitored but can be a health hazard.

The use of microalgae for assimilation and utilization of carbon dioxide from fossil fuel-fired power plant flue gas

As CO2 plays a central role in the economics of microalgae cultivation, an accurate estimate of its cost is essential. Toward this end, an economic model was developed for CO2 recovery from power-plant flue gas and its delivery to microalgae ponds. A design basis was devised for recovering CO2 from flue gas emitted by a typical 500 MW power plant located in the Southwestern United States. For the standard process, which included monoethanolamine (MEA) extraction, compression, dehydration, and transportation to the ponds, a delivered CO2 cost of

Environmental benefits on a life cycle basis of using bagasse-derived ethanol as a gasoline oxygenate in India

40/t was estimated. The model was also used to evaluate the efficacy of directly using the flue gas, however, this option was found to be more expensive. The economics of microalgae cultivation using power-plant flue gas can be evaluated by integrating this model for CO2 recovery with a previously developed model for microalgae cultivation. The model predictions for a long-term process are: a lipid cost of

Softwood forest thinnings as a biomass source for ethanol production: a feasibility study for California.

1.4/gal (unextracted) and a mitigation cost of

Fourier transform infrared quantitative analysis of sugars and lignin in pretreated softwood solid residues

30/t CO2 (CO2 avoided basis). These costs are economically attractive and demonstrate the promise of microalgal technology.

Enhancement in cellulase production by Trichoderma reesei Rut-C30 due to citric acid

Abstract The accumulation of carbon dioxide in the atmosphere, primarily as a result of the combustion of fossil fuels, has been linked to potential global climate change. Capture and utilization of the carbon dioxide by microalgae has emerged as a promising technology to help reduce emissions from fossil fuel-fired power plants. Microalgae are of particular interest because of their rapid growth rates and tolerance to varying environmental conditions. We are currently conducting experiments on the growth of microalgae exposed to simulated flue gas. This technology is envisioned for open raceway cultivation ponds as a low cost implementation strategy. Coupling the production of fuel or commodity chemicals with the use of flue gas carbon dioxide as a microalgal nutrient is envisioned to be a cost-effective method of reducing the amount of carbon dioxide contributed to the atmosphere by fossil fuel-fired power plants.

Infrared Quantitative Analysis of Sugars and Lignin in Pretreated Softwood Solid Residues

Abstract Bagasse is the fibrous residue generated during sugar production and can be a desirable feedstock for fuel ethanol production. Excess bagasse left after satisfying the mills’ energy requirements can be used in a bioconvesion process to make ethanol. A life cycle assessment (LCA) was conducted to quantify the environmental benefits of diverting excess bagasse to ethanol production as opposed to disposing it through the current practice of open-field burning. The LCA results demonstrated lower net values for the ethanol scenario for the following: carbon monoxide, hydrocarbons (except methane), SO x , NO x , particulates, carbon dioxide, methane, and fossil energy consumption. Reduced carbon dioxide and methane emissions for the ethanol scenario also lower its greenhouse potential. Additional drivers are the lower values observed for the following impact assessment categories for the ethanol scenario: depletion of natural resources, air acidification potential, eutrophication potential, human toxicity potential, and air odor potential. Specifically, deployment of the bioethanol option, due to its significantly lower greenhouse potential, can be facilitated via the Clean Development Mechanism, as specified under the Kyoto Protocol.