Paul A. Funk

Anaerobic digestion of municipal solid waste and agricultural waste and the effect of co-digestion with dairy cow manure

Anaerobic digestion of dairy cow manure (CM), the organic fraction of municipal solid waste (OFMSW), and cotton gin waste (CGW) was investigated with a two-phase pilot-scale anaerobic digestion (AD) system. The OFMSW and CM were digested as single wastes and as combined wastes. The single waste digestion of CM resulted in 62m3 methane/ton of CM on dry weight basis. The single waste digestion of OFMSW produced 37m3 methane/ton of dry waste. Co-digestion of OFMSW and CM resulted in 172m3 methane/ton of dry waste. Co-digestion of CGW and CM produced 87m3 methane/ton of dry waste. Comparing the single waste digestions with co-digestion of combined wastes, it was shown that co-digestion resulted in higher methane gas yields. In addition, co-digestion of OFMSW and CM promotes synergistic effects resulting in higher mass conversion and lower weight and volume of digested residual.

Miniature radio-frequency mobility analyzer as a gas chromatographic detector for oxygen-containing volatile organic compounds, pheromones and other insect attractants.

A high electric field, radio-frequency ion mobility spectrometry (RF-IMS) analyzer was used as a small detector in gas chromatographic separations of mixtures of volatile organic compounds including alcohols, aldehydes, esters, ethers, pheromones, and other chemical attractants for insects. The detector was equipped with a 2 mCi 63Ni ion source and the drift region for ion characterization was 5 mm wide, 15 mm long and 0.5 mm high. The rate of scanning for the compensation voltages was 60 V s(-1) and permitted four to six scans to be obtained across a capillary chromatographic elution profile for each component. The RF-IMS scans were characteristic of a compound and provided a second dimension of chemical identity to chromatographic retention adding specificity in instances of co-elution. Limits of detection were 1.6-55 x 10(-11) g with an average detection limit for all chemicals of 9.4 x 10(-11) g. Response to mass was linear from 2-50 x 10(-10) g with an average sensitivity of 4 pA ng(-1). Separations of pheromones and chemical attractants for insects illustrated the distinct patterns obtained from gas chromatography with RF-IMS scans in real time and suggest an analytical utility of the RF-IMS as a small, advanced detector for on-site gas chromatographs.

Converting gin and dairy wastes to methane

Alternatives to gin trash and manure disposal would benefit both the cotton ginning and dairy industries. nAnaerobic digestion produces both methane gas and a class A soil amendment. Gin and dairy wastes were combined in the nsolid phase portion of a two-phase anaerobic system to determine the combinations of temperature, rewetting interval, and nmixture ratio that maximize potential methane gas production and minimize process completion time. No significant volatile nfatty acid formation occurred after leachate pH approached 7.0, indicating process completion. This took approximately three nweeks when temperatures were above 32°C (90°F), mixture ratios were below 5:1 (gin to dairy waste, dry mass basis), and nthe solid phase was wetted twice daily. Ten percent of the mass was converted to soluble chemical oxygen demand (COD), nwhich has potential for conversion to methane in the second phase.

PRODUCING ENERGY AND SOIL AMENDMENT FROM DAIRY MANURE AND COTTON GIN WASTE

Millions of tonnes of feedlot manure and cotton gin waste are generated in the U.S. each year. Dairy and feedlot noperations in New Mexico produce 1.2 million tonnes of manure annually. Traditionally, manure has been used as a soil namendment in agriculture. However, land application of manure is limited in New Mexico due to problems with salinity, npotential groundwater contamination, and limited availability of agricultural land. Waste treatment alternatives are sought. nA two-phase anaerobic digestion system was used to evaluate the feasibility of producing methane and soil amendment from nmixed agricultural wastes. Cotton gin waste and dairy manure were combined and used as feedstock. Under mesophilic nconditions, 48% of the combined waste was converted into biogas. The gas yield was 87 m3 of methane per tonne of mixed nwaste. Methane concentration in the biogas averaged 72%. Gas production with mixed waste increased 35% compared to ndigesting dairy waste alone. Nutrient analyses of the residuals showed that they could be used as soil amendments. Residual nsolid material from the two-phase anaerobic digester had a considerably higher nitrogen and lower sodium content than naerobically composted manure. Anaerobic digestion lasted from one to three months and required 0.15 m3 of water per 1 m3 nof waste. Aerobic composting of similar waste in New Mexico takes eight to nine months and consumes 1.2 m3 of water per n1 m3 of waste.

The Environmental Cost of Reducing Agricultural Fine Particulate Matter Emissions

Abstract The U.S. Environmental Protection Agency (EPA) revised the National Ambient Air Quality Standards (NAAQS) in 2006, reducing acceptable fine particulate matter (PM2.5) levels; state environmental protection agencies in states with nonattainment areas are required to draft State Implementation Plans (SIPs) detailing measures to reduce regional PM2.5 levels by reducing PM2.5 and PM2.5 precursor emissions. These plans need to account for increases in emissions caused by operating control technologies. Potential PM2.5 emissions reductions realized by adding a second set of dust cyclones were estimated for the cotton ginning industry. Increases in energy consumption were calculated based on dust cyclone air pressure drop. Additional energy required was translated into increased emissions using published emission factors and state emissions inventories. Reductions in gin emissions were compared with increases in emissions at the power plant. Because of the electrical energy required, reducing one unit of agricultural PM2.5 emissions at a cotton gin results in emitting 0.11–2.67 units of direct PM2.5, 1.39–69.1 units of PM2.5 precursors, 1.70–76.8 units of criteria pollutants, and 692–15,400 units of greenhouse gases at the point where electricity is produced. If regulations designed to reduce rural PM2.5 emissions increase electrical power consumption, the unintended net effect may be more emissions, increased environmental damage, and a greater risk to public health.

Co-digestion of agricultural and municipal waste to produce energy and soil amendment:

In agriculture, manure and cotton gin waste are major environmental liabilities. Likewise, grass is an important organic component of municipal waste. These wastes were combined and used as substrates in a two-phase, pilot-scale anaerobic digester to evaluate the potential for biogas (methane) production, waste minimisation, and the digestate value as soil amendment. The anaerobic digestion process did not show signs of inhibition. Biogas production increased during the first 2u2009weeks of operation, when chemical oxygen demand and volatile fatty acid concentrations and the organic loading rate to the system were high. Chemical oxygen demand from the anaerobic columns remained relatively steady after the first week of operation, even at high organic loading rates. The experiment lasted about 1u2009month and produced 96.5u2009m3 of biogas (68u2009m3 of CH4) per tonne of waste. In terms of chemical oxygen demand to methane conversion efficiency, the system generated 62% of the theoretical methane production; the chemical oxygen demand/volatile solids degradation rate was 62%, compared with the theoretical 66%. The results showed that co-digestion and subsequent digestate composting resulted in about 60% and 75% mass and volume reductions, respectively. Digestate analysis showed that it can be used as a high nutrient content soil amendment. The digestate met Class A faecal coliform standards (highest quality) established in the United States for biosolids. Digestion and subsequent composting concentrated the digestate nitrogen, phosphorus, and potassium content by 37%, 24%, and 317%, respectively. Multi-substrate co-digestion is a practical alternative for agricultural waste management, minimisation of landfill disposal, and it also results in the production of valuable products.

Comparative Mechanical Harvest Efficiency of Six New Mexico Pod–type Green Chile Pepper Cultivars

New mexico pod–type green chile (Capsicum annuum) is one of New Mexico’s leading horticultural commodities. Cultivated acreage of green chile in NewMexico is threatened because of the high cost and insufficiently available labor for hand harvest. Therefore, mechanization is necessary to sustain the industry. Successful mechanization depends on harvester design coupled with plant architecture that optimizes harvest yield and quality. Harvested green fruit must be whole, unbroken, and unblemished for fresh and processedmarkets, so harvester design and plant architecture must maximize yield while minimizing fruit damage. In two trials conducted at the New Mexico State University Agricultural Science Center in Los Lunas, six cultivars (AZ-1904, Machete, PHB-205, E9, PDJ.7, and RK3-35) were evaluated for plant architecture and harvest efficiency with a double, open-helix mechanical harvester with two counter-rotating heads. Cultivars were direct seeded on 17 Apr. 2015 and 14 Apr. 2016 and managed according to standard production practices. Plant architecture traits, plant width, plant height, height to first primary branch, distance between first primary branch and first node, basal stem diameter, and number of basal branches were measured before harvest. Mechanical harvest yield components, which included marketable fruit, broken fruit, ground fall losses, unharvested fruit remaining on branches, and nonpod plant material, were assessed after once-over destructive harvests on 2 Sept. 2015 and 31 Aug. 2016. Fruit width, fruit length, and pericarp thickness were measured from a representative sample of 10 marketable fruit. In 2015, ‘AZ-1904’ and ‘PDJ.7’ had significantly (P £ 0.05) more marketable yield than ‘Machete’ that had the least marketable yield. No statistically significant differences were found in marketable yield in 2016. When both years were combined, ‘PDJ.7’ had significantly more nonpod plant material harvested and the plants were taller than all other cultivars. We found mechanical harvest performance to be significantly affected by plant height, with shorter plants yielding less marketable fruit. Despite differences in fruit wall thickness, no significant differences were measured in broken fruit. In 2015, ‘AZ-1904’ had significantly less basal branches per plant, reducing obstruction for the picking mechanism. Harvest efficiencies (marketable harvested fruit yield as a percentage of total plot yields) ranged from 64.6% to 39.3% during this 2-year trial, with the highest harvesting cultivars PDJ.7 and AZ-1904. In the future, all new mexico pod–type green chile breeding efforts for mechanical harvest must incorporate desirable plant architecture traits to increase harvest efficiencies.

Detecting Plastics in Seedcotton

The US cotton industry wants to increase market share and value by supplying pure cotton. Removing contamination requires developing a means to detect plastics in seedcotton. This study was conducted to determine if Ion Mobility Spectrometry (IMS) could be used to find small amounts of plastic in a matrix of heated seedcotton. Commercial IMS analyzers equipped with membrane inlets sampled air displaced from heated flasks containing seedcotton and five common plastic contaminants; bale twine, new and weathered polypropylene tarp, polyethylene film and plastic film shopping bags. In the first of two sets of experiments the temperature was varied from 85 to 115°C to determine its influence on vapor emissions; in the second, air samples were taken from seedcotton containing various amounts of each plastic. Vapors from plastics associated with cotton contamination were detected with IMS in negative polarity; different plastics were distinctive. Vapor molecules and product ions from plastics and seedcotton both increased with temperature. Seedcotton vapors spectra coincided with plastics vapors spectra but had different slope characteristics at specific drift times. Digital signal processing may be used to detect plastic contamination, triggering an alarm or control action. Spectra from new and old polypropylene tarp were nearly identical suggesting detection will be possible after weathering. IMS detection of plastics vapors in seedcotton works in the laboratory. The next step is developing IMS systems for commercial cotton gins.

Laboratory Detection of Plastics in Seedcotton with Ion Mobility Spectrometry

The US cotton industry wants to increase market share and value by supplying pure cotton. Removing contamination requires developing a means to detect plastics in seedcotton. This study was conducted to determine if Ion Mobility Spectrometry (IMS) could be used to find small amounts of plastic in a matrix of heated seedcotton. Commercial IMS analyzers equipped with membrane inlets sampled air displaced from heated flasks containing seedcotton and five common plastic contaminants; bale twine, new and weathered polypropylene tarp, polyethylene film and plastic grocery bags. In the first of two sets of experiments the temperature was varied from 85 to 115°C to determine its influence on vapor emissions; in the second, air samples were taken from seedcotton containing various amounts of each plastic. Vapors from plastics associated with cotton contamination were detected with IMS in negative polarity; different plastics were distinctive. Vapor molecules and product ions from plastics and seedcotton both increased with temperature. Seedcotton vapors spectra coincided with plastics vapors spectra but had different slope characteristics at specific drift times. Digital signal processing may be used to detect plastic contamination, triggering an alarm or control action. Spectra from new and old polypropylene tarp were nearly identical suggesting detection will be possible after weathering. IMS detection of plastics vapors in seedcotton works in the laboratory. The next step is developing IMS systems for commercial cotton gins.

Cotton Stickiness Mitigation by Bacteria

Sugars deposited on lint by late season sucking insects can make cotton difficult to nspin and difficult to market. This study evaluated a lacto bacillus strain that metabolizes insect nsugars under low moisture conditions. Lint with known levels of stickiness was sprayed with nwater containing Lalsil Cotton® and compared to untreated material after 20 days in storage. nSugar quantity was estimated using a high speed stickiness detector, a minicard machine and nchemical tests. Fiber properties were tested using high volume instrument and advanced fiber ninformation system machines. Ring spun yarn quality was tested using statimat and evenness nmachines. Less than 2% moisture was added with treatment. Consequently, no degradation in nfiber quality was observed following treatment. After 20 days there were no statistically nsignificant differences in stickiness measures, fiber properties or yarn properties between ntreated and untreated samples. Only a limited number of samples was available. Additional nsamples will be tested after 60 and 180 days. This paper will be updated on the ASABE web nsite by the end of 2006.