Patrick Thomas Murphy

Biofuels and water quality: challenges and opportunities for simulation modeling

Quantification of the various impacts of biofuel feedstock production on hydrology and water quality is complex. Mathematical models can be used to efficiently evaluate various ‘what if’ scenarios related to biofeedstock production and their impacts on hydrology and water quality at various spatial and temporal scales. Currently available models, although having the potential to serve such purposes, have many limitations. In this paper, we review the strengths and weaknesses of such models in light of short- and long-term biofeedstock production scenarios. The representation of processes in the currently available models and how these processes need to be modified to fully evaluate various complex biofeedstock production scenarios are discussed. Similarly, issues related to availability of data that are needed to parameterize and evaluate these models are presented. We have presented a vision for the development of decision support tools and ecosystem services that can be used to make watershed management decisions to minimize any potentially adverse environmental impacts while meeting biofeedstock demands. We also discuss a case study of biofeedstock impact simulation in relation to watershed management policy implications for various state and federal agencies in the USA.

Comparison of common lignin methods and modifications on forage and lignocellulosic biomass materials.

BACKGROUND A variety of methods have been developed for estimating lignin concentration within plant materials. The objective of this study was to compare the lignin concentrations produced by six methods on a diverse population of forage and biomass materials and to examine the relationship between these concentrations and the portions of these materials that are available for utilisation by livestock or for ethanol conversion. RESULTS Several methods produced lignin concentrations that were highly correlated with the digestibility of the forages, but there were few relationships between these methods and the available carbohydrate of the biomass materials. The use of Na₂SO₃ during preparation of residues for hydrolysis resulted in reduced lignin concentrations and decreased correlation with digestibility of forage materials, particularly the warm-season grasses. CONCLUSION There were several methods that were well suited for predicting the digestible portion of forage materials, with the acid detergent lignin and Klason lignin method giving the highest correlation across the three types of forage. The continued use of Na₂SO₃ during preparation of Van Soest fibres needs to be evaluated owing to its ability to reduce lignin concentrations and effectiveness in predicting the utilisation of feedstuffs and feedstocks. Because there was little correlation between the lignin concentration and the biomass materials, there is a need to examine alternative or develop new methods to estimate lignin concentrations that may be used to predict the availability of carbohydrates for ethanol conversion.

Midwest vision for sustainable fuel production.

This article charts the progress of CenUSA Bioenergy, a USDA-NIFA-AFRI coordinated agricultural project focused on the North Central region of the US. CenUSA’s vision is to develop a regional system for producing fuels and other products from perennial grass crops grown on marginally productive land or land that is otherwise unsuitable for annual cropping. This article focuses on contributions CenUSA has made to nine primary systems needed to make this vision a reality: feedstock improvement; feedstock production on marginal land; feedstock logistics; modeling system performance; feedstock conversion into biofuels and other products; marketing; health and safety; education, and outreach. The final section, Future Perspectives, sets forth a roadmap of additional research, technology development and education required to realize commercialization.

Use of Swine Manure to Improve Solid-State Fermentation in an Integrated Storage and Conversion System for Corn Stover

Swine manure contains a host of chemical and biological constituents which make it desirable for amending lignocellulosic biomass in storage for year round processing in a biorefinery. Application of swine manure in an integrated biomass storage and conversion system was investigated to determine the potential for improved conversion of corn stover to organic acids and soluble carbohydrates during ensiling. Corn stover- swine manure mixtures were prepared containing swine manure at rates of 0%, 15%, 30%, 45%, and 60% while simultaneously being adjusted to 65% moisture on a wet basis and ensiled for 0, 1, 7, and 21 days. Samples were analyzed for pH, dry matter, water-soluble carbohydrates, and organic acids. All treatments, with the exception of the 60% manure substrate, produced a pH less than 4.5, which is sufficient for stable storage. Water-soluble carbohydrates were highest in the control treatment, producing a level of 3.0% DM at day 21. Lactic acid production was unaffected by the rate of manure, with a concentration of 2.8% DM reached at day 21. Acetic acid production was improved with the manure substrates. Manure amendment rates of 30%, 45%, and 60% produced the highest acetic acid concentration of 1.8% DM. Treatments of 0%, 15%, 30%, and 45% swine manure would be acceptable substrates for use in this system; however, if preservation of fermentable carbohydrates is a higher priority than organic acid production, then the pure corn stover substrate would be the most appropriate material to use.

Use of Iodoform to Improve Lactic Acid Production in the Biomass Ensilage Conversion System

Iodoform, an iodine-containing compound used in antiseptic applications, has been found to be effective at selectivity inhibiting certain microbial populations. Application of iodoform in a hybrid fermentation system was investigated to determine the potential for increased lactic acid production by inhibiting undesirable microbes which can metabolize lactic acid. Iodoform treatment rates of 0, 0.03, 0.06, 0.11, and 0.23 g/kg dry matter (DM) were applied to a swine manure-corn stover substrate, containing 60 % manure, adjusted to 65 % moisture on a wet basis and ensiled for 0, 1, 7, and 21 days. A hemicellulase-cellulase enzyme mixture was also applied to all samples at a rate of 5 and 12.5 IU/g DM of hemicellulase and cellulase activity, respectively. Samples were analyzed for pH, water soluble carbohydrates, and organic acids. A substantial decrease in pH was observed in all treatments, but none of the treatments reached a pH of 4.5, which is sufficient for stable storage of corn stover biomass at 65 % moisture. Lactic and acetic acid production was increased with application of iodoform at 0.23 g/kg DM. Iodoform was also found to inhibit butyric fermentation, with a rate of 0.23 g/kg DM determined to be appropriate. Overall, iodoform can improve fermentation in the biomass ensilage conversion system by improving lactic acid production and inhibiting butyric fermentation.

Carbohydrate Availability Assay for Determining Lignocellulosic Biomass Quality

Current methods for characterization of lignocellulosic biomass feedstocks for biological conversion are dominated by compositional analysis and digestibility/ fermentation tests; however, both these groups of laboratory methods have their respective advantages and disadvantages. The purpose of this paper is to develop a wet-chemistry assay for determination of lignocellulosic biomass quality that combines both compositional analysis and fermentation methods. This assay also should not require expensive or highly specialized laboratory equipment and should be able to be adapted for high throughput applications, such as near infrared reflectance spectroscopy (NIRS).