A study of high solids anaerobic digestion of Bucknell University food waste followed by aerobic curing

Anaerobic digestion of food scraps has the potential to accomplish waste minimization, energy production, and compost or humus production. At Bucknell University, removal of food scraps from the waste stream could reduce municipal solid waste transportation costs and landfill tipping fees, and provide methane and humus for use on campus. To determine the suitability of food waste produced at Bucknell for high-solids anaerobic digestion (HSAD), a year-long characterization study was conducted. Physical and chemical properties, waste biodegradability, and annual production of biodegradable waste were assessed. Bucknell University food and landscape waste was digested at pilot-scale for over a year to test performance at low and high loading rates, ease of operation at 20% solids, benefits of codigestion of food and landscape waste, and toprovide digestate for studies to assess the curing needs of HSAD digestate. A laboratory-scale curing study was conducted to assess the curing duration required to reduce microbial activity, phytotoxicity, and odors to acceptable levels for subsequent use ofhumus. The characteristics of Bucknell University food and landscape waste were tested approximately weekly for one year, to determine chemical oxygen demand (COD), total solids (TS), volatile solids (VS), and biodegradability (from batch digestion studies). Fats, oil, and grease and total Kjeldahl nitrogen were also tested for some food waste samples. Based on the characterization and biodegradability studies, Bucknell University dining hall food waste is a good candidate for HSAD. During batch digestion studies Bucknell University food waste produced a mean of 288 mL CH4/g COD with a 95%confidence interval of 0.06 mL CH4/g COD. The addition of landscape waste for digestion increased methane production from both food and landscape waste; however, because the landscape waste biodegradability was extremely low the increase was small.Based on an informal waste audit, Bucknell could collect up to 100 tons of food waste from dining facilities each year. The pilot-scale high-solids anaerobic digestion study confirmed that digestion ofBucknell University food waste combined with landscape waste at a low organic loading rate (OLR) of 2 g COD/L reactor volume-day is feasible. During low OLR operation, stable reactor performance was demonstrated through monitoring of biogas production and composition, reactor total and volatile solids, total and soluble chemical oxygendemand, volatile fatty acid content, pH, and bicarbonate alkalinity. Low OLR HSAD of Bucknell University food waste and landscape waste combined produced 232 L CH4/kg COD and 229 L CH4/kg VS. When OLR was increased to high loading (15 g COD/L reactor volume-day) to assess maximum loading conditions, reactor performance became unstable due to ammonia accumulation and subsequent inhibition. The methaneproduction per unit COD also decreased (to 211 L CH4/kg COD fed), although methane production per unit VS increased (to 272 L CH4/kg VS fed). The degree of ammonia inhibition was investigated through respirometry in which reactor digestate was diluted and exposed to varying concentrations of ammonia. Treatments with low ammoniaconcentrations recovered quickly from ammonia inhibition within the reactor. The post-digestion curing process was studied at laboratory-scale, to provide a preliminary assessment of curing duration. Digestate was mixed with woodchips and incubated in an insulated container at 35 °C to simulate full-scale curing self-heatingconditions. Degree of digestate stabilization was determined through oxygen uptake rates, percent O2, temperature, volatile solids, and Solvita Maturity Index. Phytotoxicity was determined through observation of volatile fatty acid and ammonia concentrations.Stabilization of organics and elimination of phytotoxic compounds (after 10–15 days of curing) preceded significant reductions of volatile sulfur compounds (hydrogen sulfide, methanethiol, and dimethyl sulfide) after 15–20 days of curing. Bucknell University food waste has high biodegradability and is suitable for high-solids anaerobic digestion; however, it has a low C:N ratio which can result in ammonia accumulation under some operating conditions. The low biodegradability of Bucknell University landscape waste limits the amount of bioavailable carbon that it can contribute, making it unsuitable for use as a cosubstrate to increase the C:N ratio of food waste. Additional research is indicated to determine other cosubstrates with higher biodegradabilities that may allow successful HSAD of Bucknell University food waste at high OLRs. Some cosubstrates to investigate are office paper, field residues, or grease trap waste. A brief curing period of less than 3 weeks was sufficient to produce viable humus from digestate produced by low OLR HSAD of food and landscape waste.

A General Approach Towards the Synthesis of Amido-Functionalized Biodegradable Polyesters

The thesis presented here describes methodologies to produce pendant group functionalized polyesters from amido-functionalized α-hydroxy acids. The synthetic methods used to produce the functionalized α-hydroxy acids are compatible with a wide array of functional groups, making this technique highly versatile. The synthesis of functionalized polyesters was investigated to develop polymers with properties that may improve the capabilities of existing biodegradable polyesters for applications in controlled release pharmaceuticals. Chemically modified a-hydroxy acids were synthesized by reacting glyoxylic acid with a primary or secondary amide. To demonstrate the utility of this reaction, fourstructurally dissimilar amide substituents were examined including 2-pyrrolidione, benzamide, acetamide and acrylamide. The reaction is synthetically simple, provides high yields and is uniquely flexible, functionalized monomer. The compatibility of this procedure with the collection of functional groups mentioned circumvents the need for syntheses. The amido-functionalized monomers were polymerized by two different techniques: melt polycondensation and solution polymerization. Melt polycondensation was conducted by heating the monomer past its melting temperature under reduced pressure. Oligomeric functionalized polyesters (= 800 g/mol) with low PDIs (= 1.05) were obtained by melt polycondensation. Melt polycondensation was not compatible with all of the synthesized monomers. Two of the monomers (containing benzamide and acrylamide functionalities) degraded before the polycondensation reaction occurred. Thermal gravimetric analysis confirmed that a process other than polyesterification was occurring, indicating that some amido-functionalized α-hydroxy acids cannot be synthesized in the melt.Solution polymerization was conducted to polymerize functionalized α-hydroxy acids that were incompatible with melt polycondensation. Several modified Steglich polyesterifications were tested including p-toluenesulfonic acid mediated and scandium (III) triflate catalyzed. Only oligomeric functionalized polyesters were formed bythis method. A number of possible side reactions including the formation of an N-acylurea and a cyclic polymer ring were possible. The utility of this procedure appears to be limited due to the complexity of the reaction and its inability to produce high molecular weight polymer.

Characterization of Biodegradable Polymer Nanocomposites Fabricated via Solid-State Processing

Biodegradable polymer/clay nanocomposites were prepared withpristine and organically modified montmorillonite in polylactic acid (PLA) and polycaprolactone (PCL) polymer matrices. Nanocomposites were fabricated using extrusion and SSSP to compare the effects of melt-state and solid-state processing on the morphology of the final nanocomposite. Characterization of various material properties was performed on prepared biodegradable polymer/clay nanocomposites to evaluate property enhancements from different clays and/or processing methods.

The Use Of Amido- And Imido-Functionalized Alpha Hydroxy Acids In The Creation Of Biodegradable Polyesters: An Exploration Of Va

The purpose of this thesis was to synthesize biodegradable polyesters from a wide array of functionalized ¿-hydroxy acids. The initial strategy was to use amido-functionalized ¿-hydroxy acids and 2-bromopropanoyl bromide to form amido-functionalized cyclic diesters. Then, the resulting cyclic diesters would be used in ring opening polymerization to create biodegradable polyesters. However, the spontaneous rapid degradation of the secondary amido-functionalized cyclic diester structure, as seen with 2-benzamido-hydroxyacetic acid, limited ring formation to tertiary amido-functionalized ¿-hydroxy acids. Also, the hydrophilic nature of most ¿-hydroxy acids allowed water into the crystal structure of the ¿-hydroxy acid. Then, when the ¿-hydroxy acid was used in ring forming reactions, the associated water deactivated reactive reagents and limited cyclic diester synthesis. These issues led to the synthesis of hydrophobic and tertiary amido- and imido-functionalized ¿-hydroxy acids, 2-phthalimido-2-hydroxyacetic acid and 2-(1-oxoisoindolin-2-yl) hydroxyacetic acid. The new ¿-hydroxy acids were used in two new polymerization techniques, melt polycondensation and solution polymerization, instead of ring open polymerization. Melt polycondensation and solution polymerization had shown previous success in forming oligomers of amido-functionalized ¿-hydroxy acids. Melt polycondensation was conducted by heating the monomer past its melting temperature under reduced pressure. The uncatalyzed melt polycondensation of 2-(1-oxoisoindolin-2-yl) hydroxyacetic acid created polyesters (¿ 960 g/mol). The scandium(III) trifluoromethanesulfonate enhanced melt polycondensation polymerization created slightly larger oligomers (¿ 1340 g/mol). However, 2-phthalimido-2-hydroxyacetic acid was not compatible with melt polycondensation because thermal degradation occurred. Thus, solution polymerization was conducted via Steglich esterification. Only oligomeric functionalized polyesters were formed (¿ 1060 g/mol). Future work should focus on optimization of the catalyst and the reaction conditions to obtain higher molecular weight polyesters. Also, 2-(1-oxoisoindolin-2-yl) hydroxyacetic acid should be utilized in the cyclic diester synthesis technique.

Full Cups, Full Coffers: Tax Strategies and Consumer Culture in the Early Modern German Cities

During the sixteenth and seventeenth centuries, the excise taxes (Ungeld) paid by town residents on the consumption of beer, wine, mead and brandy represented the single most important source of civic revenue for many German cities. In a crisis, these taxes could spike to 70-80% of civic income. This paper examines civic budgets and 'behind-the-scenes' deliberations in a sample of towns in southern Germany in order to illuminate how decisions affecting consumer taxes were made. Even during the sobriety movements of the Reformation and post-Reformation period, tax income from drinkers remained attractive to city leaders because the bulk of the excise tax burden could easily be shifted away from privileged members of society and placed on the population at large. At the same time, governments had to maintain a careful balance between what they needed in order to govern and what the consumer market could bear, for high taxes on drinks were also targeted in many popular revolts. This led to nimble politicking by those responsible for tax decisions. Drink taxes were introduced, raised, lowered and otherwise manipulated based not only on shifting fashions and tastes but also on the degree of economic stress faced by the community. Where civic rulers were successful in striking the right balance, the rewards were considerable. The income from drink sales was a major factor in how the cities of the Empire survived the wars and other crises of the early modern period without going into so much debt that they lost their independence.

Full Cups, Full Coffers: Tax Strategies and Consumer Culture in the Early Modern German Cities

During the sixteenth and seventeenth centuries, the excise taxes (Ungeld) paid by town residents on the consumption of beer, wine, mead and brandy represented the single most important source of civic revenue for many German cities. In a crisis, these taxes could spike to 70–80% of civic income. This paper examines civic budgets and ‘behind-the-scenes’ deliberations in a sample of towns in southern Germany in order to illuminate how decisions affecting consumer taxes were made. Even during the sobriety movements of the Reformation and post-Reformation period, tax income from drinkers remained attractive to city leaders because the bulk of the excise tax burden could easily be shifted away from privileged members of society and placed on the population at large. At the same time, governments had to maintain a careful balance between what they needed in order to govern and what the consumer market could bear, for high taxes on drinks were also targeted in many popular revolts. This led to nimble politicking by those responsible for tax decisions. Drink taxes were introduced, raised, lowered and otherwise manipulated based not only on shifting fashions and tastes but also on the degree of economic stress faced by the community. Where civic rulers were successful in striking the right balance, the rewards were considerable. The income from drink sales was a major factor in how the cities of the Empire survived the wars and other crises of the early modern period without going into so much debt that they lost their independence.