Rick Gustafson

Converting lignocellulosic solid waste into ethanol for the State of Washington: an investigation of treatment technologies and environmental impacts.

There is little research literature on the conversion of lignocellulosic rich waste streams to ethanol, and even fewer have investigated both the technical aspects and environmental impacts together. This study assessed technical and environmental challenges of converting three lignocellulosic waste streams to ethanol: municipal solid waste (MSW), low grade mixed waste paper (MWP), and organic yard waste (YW). Experimental results showed high conversion yields for all three streams using suitable conversion methods. Environmental impacts are highly dependent on conversion technology, and process conditions used. Life cycle assessment results showed that both chemicals production and waste collection are important factors to be included within a waste-to-ethanol study.

Post-treatment mechanical refining as a method to improve overall sugar recovery of steam pretreated hybrid poplar.

This study investigates the effect of mechanical refining to improve the sugar yield from biomass processed under a wide range of steam pretreatment conditions. Hybrid poplar chips were steam pretreated using six different conditions with or without SO2. The resulting water insoluble fractions were subjected to mechanical refining. After refining, poplar pretreated at 205°C for 10min without SO2 obtained a 32% improvement in enzymatic hydrolysis and achieved similar overall monomeric sugar recovery (539kg/tonne) to samples pretreated with SO2. Refining did not improve hydrolyzability of samples pretreated at more severe conditions, nor did it improve the overall sugar recovery. By maximizing overall sugar recovery, refining could partially decouple the pretreatment from other unit operations, and enable the use of low temperature, non-sulfur pretreatment conditions. The study demonstrates the possibility of using post-treatment refining to accommodate potential pretreatment process upsets without sacrificing sugar yields.

Use of Raman spectroscopy for continuous monitoring and control of lignocellulosic biorefinery processes.

Abstract The production of fuels and chemicals from lignocellulosic biomass demands efficient processes to compete with fossil fuel-derived products. Key biorefinery processes, such as enzymatic hydrolysis of cellulose and microbial fermentation, can be monitored by advanced sensors in real time, providing information about reactant and product concentration, contamination, and reaction progress. Spectroscopic techniques such as Raman spectroscopy provide a means of quickly and accurately assessing many types of reaction mixtures non-destructively, in real time, and with no costly sample preparation and analysis time. Raman spectroscopy techniques have been developed to accurately quantify a number of compounds present in lignocellulosic processes, and methods have been developed to overcome the presence of fluorescent compounds that can increase the spectral background. Online Raman sensors also can provide the feedback measurements necessary for advanced process controls (APCs). Specifically, model predictive control, a common APC used extensively throughout similar processing industries, is especially well suited for ensuring optimal production of bio-based chemicals from lignocellulosic material.

Bridging the gap between feedstock growers and users: the study of a coppice poplar-based biorefinery

BackgroundIn the biofuel industry, land productivity is important to feedstock growers and conversion process product yield is important to the biorefinery. The crop productivity, however, may not positively correlate with bioconversion yield. Therefore, it is important to evaluate sugar yield and biomass productivity. In this study, 2-year-old poplar trees harvested in the first coppice cycle, including one low-productivity hybrid and one high-productivity hybrid, were collected from two poplar tree farms. Through steam pretreatment and enzymatic hydrolysis, the bioconversion yields of low- and high-productivity poplar hybrids were compared for both sites.ResultsThe low-productivity hybrids had 9–19% higher sugar yields than the high-productivity hybrids, although they have the similar chemical composition. Economic calculations show the impact on the plantation and biorefinery of using the two feedstocks. Growing a high-productivity hybrid means the land owner would use 11–26% less land (which could be used for other crops) or collect

Removal of non-structural components from poplar whole-tree chips to enhance hydrolysis and fermentation performance

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A contribution to the modeling of kraft pulping

3.46 MM/year extra revenue from the surplus feedstock. On the other side, the biorefinery would receive 5–10% additional revenue using the low-productivity hybrid.ConclusionWe propose a business model based on the integration of the plantation and the biorefinery. In this model, different feedstocks are assessed using a metric of product tonnage per unit land per year. Use of this new economic metric bridges the gap between feedstock growers and users to maximize the overall production efficiency.

Synergistic effects of mixing hybrid poplar and wheat straw biomass for bioconversion processes

BackgroundWhole-tree chips will be a likely feedstock for future biorefineries because of their low cost. Non-structural components (NSC), however, represent a significant part of whole-tree chips. The NSC can account for more than 10% of whole-tree poplar mass when the trees are grown in short rotation cycles. The influence of NSC, however, on the production of fuels and chemicals is not well known. In this study, we assessed the impact of NSC removal from poplar whole-tree chips on pretreatment and enzymatic hydrolysis yields, overall sugar recovery, and fermentation yield. In addition, we evaluated the economics of preprocessing as a new unit operation in the biorefinery.ResultsPoplar whole-tree chips were preprocessed by neutral or acidic washing before steam pretreatment, enzymatic hydrolysis, and fermentation. Preprocessing of poplar reduced ash and extractives content as much as 70 and 50%, respectively. The overall sugar yield after pretreatment and hydrolysis was 18–22% higher when the biomass had been preprocessed, which was explained by higher sugar yields in liquid fraction and more efficient enzymatic hydrolysis of the solid fraction. The liquid fraction ethanol fermentation yield was 36–50% higher for the preprocessed biomass.ConclusionsIt appears that preprocessing reduced the buffering capacity of the biomass due to ash removal, and thereby improved the enzymatic hydrolysis. Removal of extractives during preprocessing improved the fermentation yield. The economic modeling shows that a preprocessing unit could have significant economic benefits in a biorefinery, where poplar whole-tree chips are used as bioconversion feedstock.