Ambient Aeration Research Articles

Effects of air discharge on bubble dynamics in vertically discharged bubble plumes

Vertically discharged bubble plumes have many applications in the industry and environment, such as aeration and sludge removal, gas and liquid mixture, and gas transfer enhancement. Circular nozzles mainly generate vertical bubble plumes and the ambient aeration requirement determines the design parameters such as nozzle size and air discharge. A series of laboratory experiments was performed to test the effects of air discharge on bubble dynamics by evaluating, bubble interfacial area, bubble size frequency, and other related parameters. Four air discharges were selected and bubble characteristics such as bubble mean velocity, bubble concentration, bubble mean diameter, and bubble size distribution were measured with a Bubble Refractive Instrument (RBI) probe. The results showed that bubble characteristics such as bubble interfacial area, bubble frequency, and bubble concentration/gas fraction significantly varied with the distance from the nozzle and all parameters gradually decreased afterwards. It was found that bubble parameters were independent of air discharge for x/H < 0.35, and strong discharge dependency was observed for x/H ≥ 0.35 where × is the distance from the nozzle and H is the water depth. Experimental results indicated that as air discharge increased by four times, the mean bubble diameter increased by an average of 32 %. The direct correlation between air discharge and bubble frequency indicated that both the number of bubbles and their velocities increased non-linearly with air discharge. The effect of air discharge on the distribution of bubble turbulent intensity indicated a non-linear growth on the probability of higher ranges of turbulent intensity.

Economic and Technical Feasibility of Grain Chilling in Brazil

Grain quality is critical due to the more stringent food-safety demands. Chilled aeration has become a popular technology for preventing grain spoilage during storage, mainly in warmer regions. However, a limiting factor in broad-scale adoption of chilling is the general belief that this technology is much more expensive than other post-harvest methods, such as the aeration with ambient air. In this work, ambient and chilled aeration were simulated considering the three major grain-producing regions in Brazil. Also, three storage capacities (95, 5000, 10500 t), five-grain types (corn, coffee, rice, bean, soybean), and two storage periods (beginning at the first and the last months of the harvest period) were used in the study, totalling 180 simulation scenarios. Based on these simulations a comparative cash flow analysis was performed aiming at evaluating the influence of the product, storage period, region, and silo size on the costs and profits from using these technologies. Results were strongly affected by the weather patterns of the studied regions, market values of grain, storage sizes, and fan operation hours. Chilled aeration should be economically competitive with ambient aeration, and the two technologies appeared as low-risk investments in Brazil, achieving average profits for 20 years by considering the time of money of US$ 68 and 59.4 million, respectively. Considering the technical factors, chilling presented higher energy consumption, but showed a greater potential for reducing grain temperatures and resulted in grain dry matter losses around 58% smaller than those verified when using ambient air.

Air Injection of Subsurface Drip Irrigation Water Improves Tuber Yield and Quality of Russet Potato

Irrigation water for potato production is becoming an issue in most irrigated production regions. Producing potatoes under drip irrigation has proven to reduce irrigation water use. However, tuber productivity has to increase under drip irrigation to offset the initial cost of installing the drip system. Ambient aeration of drip irrigation water may improve tuber yield and quality. A field study was conducted at Colorado State University’s San Luis Valley Research Center, Colorado, USA, to evaluate the effect of ambient air injection of subsurface drip irrigation water on leaf growth and tuber performance of potato cultivar Rio Grande Russet. Treatments included aerated and non-aerated drip irrigated plots that were randomly assigned within four replicated blocks. The Mazzei Venturi system was inserted in the main drip line to inject ambient air into drip tapes that supplied aerated water to the air injected treatment plots. Plants that received aerated drip irrigation water produced higher total tuber yield and increased the yield of large marketable size (> 170 g and > 285 g) tubers compared to plants grown under non-aerated drip irrigation water. The yield increases were, 8%, 19%, and 5%, for total, > 170 g, and > 285 g tuber yield, respectively. Early tuber bulking was observed, Leaf Area Index increased, and root mass production increased in plants that received aerated drip irrigation water compared to plants that received non-aerated irrigation water. Tuber external defects (growth cracks, knobs, and misshapes) were reduced by 9.2% in tubers produced under aerated drip irrigation water. Data from this study clearly indicate that ambient air injection of subsurface drip irrigation water can improve potato productivity and tuber quality. AJPR-D-20–00030R1.

Chilled Aeration to Control Pests and Maintain Grain Quality during Summer Storage of Wheat in the North Central Region of Kansas

Abstract.Chilled aeration allows grain to be cooled, independent of ambient conditions, to “safe” temperatures at which insects, fungi, and spoilage development are reduced to a minimum. The objective of this research was to evaluate the advantages of using grain chilling to preserve the quality of grain and reduce post-harvest losses caused by insects and fungi, compared to the conventional aeration and storage strategies used during summer storage in central Kansas. The research trials were developed at a farmer’s cooperative in central Kansas in 2015 and 2016 on low-moisture wheat harvested during the summer of 2015 and 2016, respectively, and stored in two 1,350 metric ton (t) steel silos in which one was chilled and the other was used as a control managed by the cooperative. Temperature of the grain inside each silo was monitored with temperature cables. Variables evaluated were: moisture content (MC), grain and flour quality, insect-pest development and reproduction rate, insect fragments per 500 g of grain, and fungi presence. In 2015, the chilling treatment reduced the grain temperature from 28°C to 17°C in approximately 175 h, while in 2016 it took 245 h to reach about the same temperature with an initial grain temperature of 39°C. Grain temperatures below 25°C were not achieved in the control silo during the summer using ambient aeration. Minimum variation of MC was observed in the Chilled silo while ambient aeration reduced the moisture content by 0.5%. Reproduction rates of the red flour beetle and lesser grain borer were significantly reduced by chilling temperatures lower than 17°C. Lower temperatures also reduced insect populations detected in probe traps and insect damaged kernels. Insect fragments and fungi presence had no significant increase throughout the trials in either of the silos. No clear evidence of flour quality being better preserved at lower temperatures was detected. The energy cost of running the grain chiller was between 0.26-0.32 $/t higher than ambient aeration. Keywords: Ambient aeration, Grain chilling, Grain quality, Stored-product fungi, Stored-product insects, Summer storage, Wheat.

Technical and economic evaluation of ambient and chilled aeration strategies to maintain the quality of paddy rice during storage in a tropical climate: Presentation

Warm and moist conditions of some tropical climate regions make it difficult to use ambient aeration to cool stored grain, which contributes to pest problems and increases dependence on chemical control as part of grain management strategies. Grain chilling is a non-chemical alternative to cool grain stored under high risk climatic conditions. The objective of this research was to use computer simulation to evaluate the technical and economic viability of using grain chilling compared to four ambient aeration strategies developed for paddy rice stored under the tropical climatic conditions of the North Pacific coast of Costa Rica. The minimum grain temperature achieved through ambient aeration at the end of the six-month simulated storage period was 30.8°C, using an aeration strategy based on a grain-ambient temperature differential greater than 10°C. Grain chilling lowered the average grain temperature from 35°C to below 15°C in 117 hours and the maximum average temperature it registered after six months of storage was 15.5°C. The economic evaluation of the ambient aeration and chilling strategies determined that the operational costs of grain chilling were 1.83 US $/t lower than ambient aeration plus chemical control of pests. However, the initial cost of the grain chiller made the net present cost (NPC) of the grain chilling strategy 0.22 US $/t higher than the cost of ambient aeration plus chemical control over a 10-year analysis. Several potential financial options were analyzed to make the grain chiller economically feasible for a rice miller in Costa Rica.

Chilled aeration to control pests and maintain grain quality during the summer storage of wheat in north central region of Kansas.

Chilled aeration allows to cool grain, independent of ambient conditions, to safe temperatures where insect, fungi, and spoilage is reduced to the minimum. The objective of this research was to evaluate the advantages of using grain chilling to preserve the quality of grain and reduce post-harvest losses, compared to conventional aeration and storage strategies used during the summer storage of wheat in Central Kansas, U.S.A. The research trials were developed in two 1,350 metric ton (t) steel silos in a Farmer’s Cooperative during the summer and fall of 2015 and 2016. One of the silos was chilled and the other was used as a control managed by the Cooperative. Variables evaluated were: grain temperature, moisture content (MC), grain quality, insect development and reproduction rate. The chilling treatment reduced the grain temperature from 28°C- 39°C to a minimum of 17°C- 17.6°C in less than 250 hours. Grain temperatures below 25°C were not possible during the summer using ambient aeration. Minimum variation of MC was observed in the Chilled silo while ambient aeration reduced the MC by 0.5%. Reproduction rates of RFB and LGB were significantly reduced by chilled temperatures lower than 17°C. Lower temperatures also reduced insects discovered in probe traps and insect damaged kernels (IDK). The energy cost of the grain chiller was between 0.26 US $/t- 0.32 US $/t higher than ambient aeration.

Investigating the Role of Electrolyte Composition and Oxide Structure in Galvanic Corrosion Susceptibility Under Atmospheric Electrolytes

The goal of this study is to develop a better mechanistic understanding of how electrolyte composition and surface oxides can influence corrosion kinetics in the electrolytes formed from atmospheric processes. It has been observed that galvanic couples between aluminum alloys and titanium or stainless steel fasteners exposed to electrolytes formed from atmospheric processes lead to very different corrosion rates (Z. Feng, G. Frankel, Corrosion, 70(2014) pgs 95-106). In order to collect the data necessary to accomplish this goal, sixteen 2”x2” panels of AA2024, AA7075, CRES 13-8, CRES 17-4, Ti-6Al-4V, and Custom 465 were cut from panel or bar stock and polished to 600 grit SiC. The samples were then mounted in 300 mL Gamry Paracells and exposed for 18 hours to the following electrolytes: 0.6M NaCl at ambient aeration, 6M NaCl at ambient aeration, deoxygenated 0.6M NaCl saturated with nitrogen,0.6M NaCl + 0.01M HCl, 0.6M NaCl + 0.01M H2SO4, and 0.6M NaCl + 0.005M HNO3 + 0.005M H2SO4. The aluminum alloys were then anodically polarized at 0.167 mV/sec from -0.02V below EOC to + 1.5VSCE. The other alloys were polarized cathodically at 0.167 mV/sec from +0.02V above EOC to -1.4VSCE. Results for the cathodic polarization scans of the CRES 13-8PH stainless steel and the Ti-6Al-4V titanium alloy are shown in Figure 1. The differences in cathodic current capacity for materials exposed to the same electrolyte at the same aeration level reinforces the fact that oxide microstructure plays a significant role in catalyzing reduction reactions, though the kinetics of the reaction rates may not be predicted from a simple galvanic series. Of more interest are the changes in reaction rates from acidification of the electrolyte. This suggests that the electrolyte is changing the the oxide microstructure or that new reduction reactions are supported. This is significant because overlays of the anodic polarizations of the aluminum alloys indicate that material loss rates can be orders of magnitude higher for acidified atmospheric electrolytes. These effects are being investigated using microelectrode experiments on droplets of the various electrolytes along with supporting experiments using Scanning Kelvin Probe techniques. Acknowledgements The authors gratefully acknowledge the financial support of the Office of Naval Research Figure 1: Cathodic polarization curves for the titanium alloy Ti-6Al-4V and the stainless steel CRES 13-8PH in 0.6M NaCl and 0.6M NaCl + 0.005M H2SO4 + 0.005M HNO3, showing that materials with different surface oxides and in near-neutral to low-pH electrolytes can support very different cathodic reaction rates with potentially very deleterious consequences for galvanic couples with more active materials.

Fate of microconstituents in biosolids composted in an aerated silage bag

Although most composting studies report pathogen concentrations, little is known about the fate of Endocrine Disruptor Chemicals (EDCs) during composting. In this study, a positively aerated polyethylene bag composting system was filled with a mixture of woodchips and limed biosolids from a large Waste Water Treatment Plant (WWTP) to study the removal efficiency of two different groups of EDCs. Two antibacterial compounds, Triclocarban (TCC) and Triclosan (TCS), and a TCS byproduct, Methyltriclosan (MeTCS), as well as seven congeners of flame retardants known as PBDEs (Polybrominated Diphenyl Ethers) were studied during two phases of composting: 1) a thermophilic phase, in which positive mechanical aeration, pushing air into and through the materials matrix, was conducted for 2 months; and 2) a curing and stabilization phase in which no mechanical aeration was provided and the bag was opened to ambient passive aeration to simulate storage conditions for seven months. Our results showed that while TCC concentrations remained constant, TCS degradation took place during both phases. The degradation of TCS was corroborated by the formation of MeTCS in both phases. The TCS concentrations decreased from 18409 ± 1,877 to 11955 ± 288 ng g−1 dry wt. during the thermophilic phase and declined from 11,955 ± 288 to 7,244 ± 909. ng g−1 dry wt. by the end of the curing phase. Thus, slightly greater TCS transformation occurred during the second than during the first (35.1 vs. 39.4%). MeTCS concentrations increased from 189.3 ± 8.6 to 364.6 ± 72.5 ng g−1 dry wt. during the first phase and reached 589.0 ± 94.9 ng g−1 dry wt. at the end of the second phase. PBDEs concentrations were below quantification limits for all but two of the congeners analyzed (BDE-47 and BDE-99). PBDE concentrations were measured at the end of the first phase only and were comparable to initial concentrations.

Optimal Conditions for the Post-Harvest Storage of Rhizoids of the Brown Seaweed Undaria pinnatifida (Phaeophyta) for Arachidonic Acid Production

The non-utilized biomass of the aquacultured seaweed Undaria pinnatifida, particularly the rhizoid, is an alternative source of arachidonic acid (AA). Of the five aquacultured kelps that were tested, U. pinnatifida yielded the highest amount of AA, which was isolated from the rhizoids. Its identity (C20:4 n-6) was confirmed from gas chromatography-mass spectrometry spectral data. The optimal conditions for post-harvest storage or pretreatment of the rhizoids in Provasoli's enriched seawater for AA extraction were determined to be pH 7.8, 2% CO2-enriched air, 20 μmol m -2 s -1 light, and 10°C. Under these conditions, the AA content after 1 day of storage was enhanced by up to 127%. In the absence of light under ambient aeration, the AA content after 1 day of storage diminished to 90%. Rhizoids collected late in the season (April and May) contained the highest amounts of AA (approximately 2.5 mg/g tissue).

Use of sodium bicarbonate to stimulate triacylglycerol accumulation in the chlorophyte Scenedesmus sp. and the diatom Phaeodactylum tricornutum

There is potential for algal-derived biofuel to help alleviate part of the world’s dependency on petroleum based fuels. However, research must still be done on strain selection, induction of triacylglycerol (TAG) accumulation, and fundamental algal metabolic studies, along with large-scale culturing techniques, harvesting, and biofuel/biomass processing. Here, we have advanced the knowledge on Scenedesmus sp. strain WC-1 by monitoring growth, pH, and TAG accumulation on a 14:10 light–dark cycle with atmospheric air or 5% CO2 in air (v/v) aeration. Under ambient aeration, there was a loss of pH-induced TAG accumulation, presumably due to TAG consumption during the lower culture pH observed during dark hours (pH 9.4). Under 5% CO2 aeration, the growth rate nearly doubled from 0.78 to 1.53 d−1, but the pH was circumneutral (pH 6.9) and TAG accumulation was minimal. Experiments were also performed with 5% CO2 during the exponential growth phase, which was then switched to aeration with atmospheric air when nitrate was close to depletion. These tests were run with and without the addition of 50 mM sodium bicarbonate. Cultures without added bicarbonate showed decreased growth rates with the aeration change, but there was no immediate TAG accumulation. The cultures with bicarbonate added immediately ceased cellular replication and rapid TAG accumulation was observed, as monitored by Nile Red fluorescence which has previously been correlated by gas chromatography to cellular TAG levels. Sodium bicarbonate addition (25 mM final concentration) was also tested with the marine diatom Phaeodactylum tricornutum strain Pt-1 and this organism also accumulated TAG.

Aeration Strategy Simulations for Wheat Storage in the Sub-Tropical Region of North India

Ambient aeration is typically used in temperate climates to preserve grains by cooling, preventing moisture migration, and maintaining temperature as low and uniform throughout the grain mass as possible. However, the climatic factors for wheat bulk storage in the sub-tropical climate of north India are challenging for the grain preservation process. Low relative humidity with high temperature during daytime and high relative humidity with low temperature during nighttime is the common phenomenon. Five years of weather data were analyzed using the modified Chung-Pfost EMC equation for wheat. Fifteen different aeration strategies were formulated based on the weather data during the maintenance period (June to September) and cooling period (October to March). Strategies were selected based on combinations of the following parameters: temperature control; EMC control; 1 h, 2 h, or 4 h morning and/or evening aeration; and 0.11, 0.34, and 0.67 m3 min-1 t-1 airflow rate. These 15 aeration strategies for the sub-tropical weather conditions of north India were studied using the 2D PHAST-FEM model developed at Purdue University. The initial grain temperature and moisture were assumed as 27°C and 12% (w.b.), respectively, based on typical harvest conditions. Dry matter loss (DML), insect development, fan run hours, and average grain temperature and moisture content for these aeration strategies were quantified based on weather data from 2000-2001 to 2004-2005. Aeration strategies were selected based on the optimum combination of low values of DML, insect development, grain temperature, moisture content, and fan run hours during both the maintenance and cooling periods . The best strategy was to operate fans 4 h during the morning and evening with an airflow of 0.11 m3 min-1 t-1, with EMC control but without temperature control during the maintenance period and with both EMC and temperature control during the cooling period (strategy 13).

Evaluation of different temperature management strategies for suppression of Sitophilus zeamais (Motschulsky) in stored maize

Three years of experimental trials (2001–2003) were conducted in 12.7 t capacity pilot-scale bins to determine the survival, reproduction and suppression of Sitophilus zeamais Motschulsky under three temperature management strategies, no aeration (NA, control), ambient aeration (AA, ⩽23.9 °C), and chilled aeration (CA, ⩽18.3 °C) from May to November in Indiana, USA. One-way ANOVA indicated that the number of progeny for small adult populations of caged insects (0.14–0.28 insects per gram maize) embedded 0.6 m deep in the stored grain mass varied among temperature strategies for some, but not all of the storage periods. Progeny numbers in the CA strategy were significantly lower ( P<0.05) than those for the NA and AA strategies for periods with longer hours of grain temperature ⩽15.0 °C. There were no differences in progeny numbers between the NA and AA strategies for most of the storage periods. This may have been due to higher mortality, lower oviposition and fecundity from overcrowding of S. zeamais under the NA strategy caused by factors in the caged insect microclimate (e.g., rapid food depletion, heating, moisture, molding, and high CO 2 levels). Our results suggest that maintaining stored maize at temperatures ⩽15.0 °C for longer periods suppressed S. zeamais progeny more effectively than at ⩽18.3 °C. In addition, leaving the stored grain bulk unaerated early in the spring so it remained cool at ⩽15.0 °C due to winter aeration resulted in early suppression of S. zeamais progeny.

Effects of Controlled Ambient Aeration on Rice Quality During On‐Farm Storage

ABSTRACTRice (Oryza sativa L., ‘Cypress’) quality is highly dependent on its handling; hence, new storage treatments must be analyzed for their impact on rice quality. Rough rice from the 2000 season was harvested, dried, and stored in six farm‐scale bins. Three of the bins were aerated with a thermostatically activated controller, and three were aerated under traditional methods. Rice was sampled periodically over 12 weeks, and quality parameters were analyzed. The effects of bin sample position (spatial), bin sample depth, aeration treatment, and storage duration were investigated for their impact on rice quality factors: moisture content, head rice yield, pasting properties, and water absorption. For both aeration treatments at most sampling durations, rice sampled from the center of the bins had significantly lower head rice yield than that sampled from the north and south areas. Overall, moisture contents were not significantly affected by sampling position, although, in some specific sampling time and aeration treatment combinations, significant variation was noticed for moisture content as a function of sampling position. Sample depth within the bin did not cause any changes in the values of the rice properties. Throughout the storage duration, the physicochemical properties of the rice treated with controlled aeration were consistent with the trends of the rice treated with manual aeration. Storage duration significantly influenced (P &lt; 0.05) water absorption, peak viscosity, head rice yield (HRY), and moisture content, with all but moisture content increasing over the storage duration. In contrast, the moisture content of the grain slightly decreased over the storage period.

CONTROLLED AMBIENT AERATION DURING RICE STORAGE FOR TEMPERATURE AND INSECT CONTROL

Rice (cv. Cypress) was harvested in September 2000 from a farm near Grady, Arkansas, placed in six, 600t(31,000bu) bins [each was filled with ~430 t (21,000 bu)], and dried gently from 18 to 13% moisture content (MC). Threeof the bins were equipped with an aeration control system activated by specific ambient air conditions in three cycles. Threeof the bins were aerated by the onsite, storage manager under his normal regimen. Grain temperatures were recorded at fourlocations within each bin. To monitor insect viability, small cages were filled with approximately 150 g of rice and 20, 1 to2weekold mixed sex adults of one insect species. The species that were tested included the lesser grain borer, Rhyzoperthadominica (Fauvel); the rice weevil, Sitophilus oryzae (L.); and the sawtoothed grain beetle, Oryzaephilus surinamensis (L.).Cages were removed at 5week intervals, and surviving and emerging insects were counted. Grain temperatures weresignificantly reduced through controlled aeration relative to the traditional, manual aeration. In addition, both live insectcounts and total emerged adult insects recovered from the cages were significantly lower (p < 0.05) within the bins treatedwith controlled aeration. The rice weevils were the hardiest of the insects tested, while sawtoothed grain beetles survivedthe least. This work indicates that controlled, ambient aeration can be an effective storage treatment against insects and maybe a useful alternative to chemical controls.

A post-harvest economic model to evaluate grain chilling as an IPM technology

A spreadsheet model was developed to evaluate the economic costs of new post-harvest integrated pest management technologies, such as grain chilling, against traditional pest control methods, such as phosphine fumigation. The model considers 34 factors including electrical power consumption, capital investment cost, chemical costs, and less quantifiable factors such as worker safety, environmental issues, and changes in end-product value. When applied to the storage of popcorn, a high value speciality crop, and wheat, the annual operating costs of chilled aeration compared to phosphine fumigation with ambient aeration were up to 128 and 300% lower, respectively. The effect of high capital investment with low variable costs, as with chilled aeration, was compared to the low capital investment and high variable costs of phosphine fumigation using a multi-year Net Present Cost (NPC) model. For the case studies evaluated, the NPC of chilled aeration ranged from −122 to 197% of that for in-house fumigation with ambient aeration. Chilling of popcorn became economically feasible if a premium of less than one cent per retail bag could be obtained for popcorn labeled post-harvest pesticide-free. Chiller unit prices of US$ 80,000–90,000 were found to be a reasonable capital expenditure for this alternative integrated pest management technology.

An experimental and modelling study of the demographic performance of rhyzopertha dominica (F.). I. development rate

Experiments are described in which data on developmental rate of the lesser grain borer, Rhyzopertha dominica, were collected over a wide range of temperatures (15–39°C) and relative humidities (20–70%). The results differed from previously published work in that development was completed at temperatures as low as 18°C, although only at relative humidities of 55% or above. Development was not completed at less than 30% r.h. at any temperature. In general, the rate of development observed in this study was lower than that in the literature. The data collected from these experiments were used to develop submodels for emergence pattern and rate of development. The derived model of development rate includes both exponential and logarithmic functions of temperature and humidity and does reflect well the critical observed interaction between temperature and relative humidity. This study has important implications for the effective use of grain-cooling with ambient aeration to restrict insect population growth.

Chilled versus ambient aeration and fumigation of stored popcorn part 2: Pest management

During the summer of 1994, a prototype grain chiller was tested to determine its efficacy as a pest management tool and its economic competitiveness with conventional pest management techniques. Four popcorn bins (121.5 tonnes) at a commercial facility were utilized. Two bins were managed using traditional ambient aeration and fumigation. The remaining two bins were managed with chilled aeration. Insect probe, larval, and pheromone traps were placed in each bin and monitored weekly. Significantly fewer Plodia interpunctella (Hübner) were trapped in the chilled aeration bins compared to the traditionally managed popcorn bins. Very few insect species were found in the probe traps, with the exception of hairy fungus beetles, Typhaea stercorea (L.) in July and August. Fewer beetles were found in the chilled bins when compared to the traditionally managed bins. Costs of chilled aeration (0.11 cents/kg) were competitive with the costs of conventional pest management practices (fumigation and ambient aeration) (0.096–0.17 cents/kg).

Chilled versus ambient aeration and fumigation of stored popcorn part 1: Temperature management

During the summer of 1994, four commercial 121.5 tonne corrugated steel bins of stored popcorn were evaluated for chemical-free pest management and conditioning. Two of the bins were managed conventionally with intensive aeration for moisture conditioning and calendar-based fumigation treatments for pest control. In the other two bins grain temperatures were managed with the Purdue prototype grain chiller. They were monitored and chilled only as needed throughout the summer. The average grain temperature in the core of the chilled bins was 11.3 °C, which was well below the critical 15–17 °C limit for most insect development. The average temperature along the south wall of the two bins was maintained at 17.5 °C. Grain temperatures in the bins conditioned with ambient aeration never dropped below 23 °C, and thus were on average 6–18 ° higher during the same period. Electrical operating costs of chilled aeration were 0.11 cents per kg of popcorn.

Temperature management of the maize weevil, Sitophilus zeamais Motsch. (Coleoptera: Curculionidae), in three locations in the United States

A new simulation model was used to quantify the effect of eight common stored maize management practices on dry matter loss and Sitophilus zeamais Motsch. development using ambient weather conditions for Indianapolis, Indiana; Columbia, South Carolina; and Amarillo, Texas. For each location, good, normal, and poor storage years were identified and evaluated. No aeration was found to be ineffective and undesirable for control of dry matter loss and S. zeamais development in all situations. Fall-chilled aeration proved to be the most effective aeration strategy for all locations and years. However, Indianapolis showed the least benefit compared to ambient fall aeration, while Columbia benefited most. Although only continuous ambient fall aeration was investigated, the results showed that controlling the aeration process holds promise in optimizing this technique. The use of spring warm-up aeration increased the rate of quality deterioration while summer rechilling improved insect control with little increase in dry matter loss. A combination of controlled ambient aeration in the fall and chilled aeration during summer storage has significant potential as a non-chemical preventative pest management technique for all locations and years. Residual pesticides and fumigation of properly cooled maize storages should not be necessary in the United States.