Three-Dimensional Modeling of Natural Convection During Postharvest Storage of Corn and Wheat in Metal Silos in the Bajío Region of Mexico

This study analyzes the dynamics of temperature and moisture in a cylindrical silo with a conical roof and floor used for storing corn in the Bajío region of Mexico, considering conditions both with and without aeration. The model incorporates external temperature fluctuations, solar radiation, grain moisture equilibrium with air humidity through the sorption isotherm (water activity), and grain respiration to simulate real storage conditions. The model is based on continuity, momentum, energy, and moisture conservation equations in porous media. This model was solved using the finite element method (FEM) to evaluate temperature and interstitial humidity variations during January and May, representing cold and warm environmental conditions, respectively. The simulations show that, without aeration, grain temperature progressively accumulates in the center and bottom region of the silo, reaching critical values for safe storage. In January, the low ambient temperature favors the natural dissipation of heat. In contrast, in May, the combination of high ambient temperatures and solar radiation intensifies thermal accumulation, increasing the risk of grain deterioration. However, implementing aeration periods allowed for a reduction in the silo’s internal temperature, achieving more homogeneous cooling and reducing the threats of mold and insect proliferation. For January, an airflow rate of 0.15 m3/(min·ton) was optimal for maintaining the temperature within the safe storage range (≤17 °C). In contrast, in May, neither this airflow rate nor the accumulation of 120 h of aeration was sufficient to achieve optimal storage temperatures. This indicates that, under warm conditions, the aeration strategy needs to be reconsidered, assessing whether a higher airflow rate, longer periods, or a combination of both could improve heat dissipation. The results also show that interstitial relative humidity remains stable with nocturnal aeration, minimizing moisture absorption in January and preventing excessive drying in May. However, it was identified that aeration period management must be adaptive, taking environmental conditions into account to avoid issues such as re-wetting or excessive grain drying.

Impact of metal silos on households’ maize storage, storage losses and food security: An application of a propensity score matching

Efficacy of metal silos and hermetic bags against stored-maize insect pests under simulated smallholder farmer conditions

Farmers in Sub-Saharan Africa use storage structures that help maintain grain quality and safety. This study reviewed the use of different grain storage structures used by smallholder farmers in Zimbabwe namely granaries, metal silos, supergrain bags, polypropylene bags and cribs. Metal silos and supergrain bags, however costly, have hermetic properties that kill pests while granaries dilapidate with time. Cribs are susceptible to moisture entry, while polypropylene bags are prone to perforations by sharp objects. This review discussed the impact of climate change on preservation of grain quality during storage. Moulds, insect pest infestations and rodent attacks are major challenges that cause storage losses. Knowledge barriers, cost, fear of the unknown, effectiveness of storage structure and security of grain are factors that affect the diversity of storage structure use. Proper use of storage structures contributes towards achieving sustainable development goals and increases farmer resilience to the impacts of climate change.

This study examines the economic feasibility of improved storages and the potential impacts of using them on household food security and income. Moreover, it tests whether storage losses can induce early sale of households maize produce. We used data from on-farm experiment, household survey, and secondary sources. We considered Purdue Improved Crop Storage (PICS) bags, metallic silos, and polypropylene bags (control). Results show that PICS bags are profitable when the grain is sold during the lean season. However, the economic feasibility of metallic silos depends on the size of the storages and location i.e. silos of 1.5t and 2t storage capacities are feasible in some districts while lower size silos are not feasible in all locations. Storing maize using PICS bags will enhance household food security, especially among net-buyer farm households enabling them to reduce their annual grain deficit period by three to four weeks. Moreover, market-oriented storage using the improved storage options can increase farmers income substantially. Our results do not justify that the sell low, buy high situation observed among smallholder farmers is caused by high grain losses due to storage insect pests. Keywords: Maize, PICS bags, metallic silos, price seasonality, potential impact, Tanzania Acknowledgement : The authors are grateful to USAID/FtF Initiative for its financial support.

Large diameter steel silos usually require a beam structure to support rooftop inspection gangways and resist loads derived from the snow and wind actions. The existence of localized overloads caused by drifted snow on roofs as a consequence of the wind action has been reported in the literature. European standard EN 1991-1-3 also considers the need of taking into account asymmetric patterns for snow loads calculation. However, conical roofs are not included in the specific list of cases considered by this standard. The present work compares the normal stresses and displacements produced in a conical steel silo roof structure by applying balanced loads distributed on the whole roof and unbalanced loads applied on a roof sector. Experimental measurements and a three-dimensional beam model developed by the authors have been used to predict the stresses and vertical displacements of a metal silo roof structure measuring 18.34 m in diameter. The results show that the existence of an asymmetric load pattern produces higher normal stresses (up to 23%) and vertical displacements (up to 50%) than those derived from balanced loads, for any similar load per beam considered.

Post-harvest storage losses (PHLs) remain significant in Sub-Saharan Africa (SSA) due to several factors mainly insect pests and molds. Hermetic storage technologies (HSTs) are being promoted to address these storage losses. In Uganda, HSTs were first introduced in 2012. However, its use among farming households remains low today. Data were collected from 306 smallholder farmers from four districts of Northern Uganda using a pre-tested semi-structured questionnaire to understand their knowledge, use, and constraints to the adoption of hermetic storage. A multivariate Logit regression model was used to find the significance of the factors affecting adoption. Results showed low awareness and use of hermetic storage among smallholder farmers. Only 53.3% of the interviewed farmers were aware of the use of hermetic storage for grain storage. The SuperGrain bag was the most known form of hermetic storage (35.3%), followed by the Purdue Improved Crop Storage (PICS) bag (34.9%), metallic silo (15.5%), and plastic silo (14.4%). Hermetic storage use was even lower as only 17.6% of the surveyed farmers were using one or more forms of hermetic storage to store their grains. Insect pest management without chemical insecticides was the main reason (83.1%) for hermetic storage use. About 75.5% of those aware of hermetic storage had received training in the technology. Hermetic storage use in farming households led to improved food availability, household income, and nutrition. Lack of local availability (50.2%), high costs (37.8%), and inadequate knowledge (6.9%) were the main constraints hindering the adoption of hermetic storage in Northern Uganda. The logit regression models showed that only training in hermetic storage significantly (p = 0.002) affected farmers’ decision to adopt hermetic storage. Understanding the factors that constrain the adoption of HSTs could provide policymakers with important information to initiate and design policies and programs aimed at reducing crop storage losses.

ABSTRACTThe outbreak of devastating storage pests has rendered smallholder farmers' traditional storage practices ineffective. This study used single bound dichotomous choice contingent valuation to examine factors determining smallholder farmers' willingness to pay (WTP) for a metal silo, a new and improved storage technology in Zimbabwe. Data were collected using structured questionnaires from 249 randomly selected households in Makoni and Shamva Districts. Logit results showed that storage loss, quantity of non-food crops, equipment value, vegetable income, participation in informal activities, and household head's age and marital status significantly influenced WTP for metal silos. The amount of grain lost in storage positively influenced farmers' WTP, suggesting that current storage practices are not effective against storage losses. Income variables, except the value of equipment, showed a positive influence on WTP for a metal silo implying that increasing the household's income eases financial constraints that could impede investments in the silo technology. The study recommends the adoption of metal silos to curb storage losses and improve household food security. Diversification of agriculture and provision of credit are recommended to increase WTP for metal silos. Development agents promoting the technology should target married and young households for sustainability, without marginalising their counterparts.

Silo storage is considered the best option for wheat storage. However, the storage losses in warehouse storage are also equivalent to silo storage of wheat when proper storage management practices are adopted and the Food Corporation of India (FCI) is the best example of a sustainable food storage system with only 0.3% storage losses in 3 years of wheat storage. The wheat procurement, storage, and distribution system of FCI is unique in the world and handles about 85 million tons of food grains annually by procuring from farmers at the guaranteed Minimum Support Price that meets certain quality standards. This article discusses the role of FCI in food security, warehouse storage management practice as a model, and storage loss level of wheat during storage.

Lately continuous usage of fossil fuels has become a significant problem due to environmental pollution coming from the usage of these energy sources. Therefore, this has caught attention around the world, looking to stop getting a worse environmental situation. One energy source that has become popular in the last few years is solar energy which can effectively be utilized as renewable and clean energy. However, reliable is a big problem for this kind of energy due to high intermittency by solar radiation. On this paper, we aim to analyze three regions from Sonora in Mexico to evaluate how good is our numerical weather predictor (WRF-Solar) to forecast solar radiation for a year on semi-arid regions and valley-like region. We used WRF-Solar and weather stations observational data to contrast and evaluate accuracy from our model. This looks to help to get a better focus on solar radiation forecasting on northwestern region in Mexico due to high capability to produce solar photovoltaic energy.

Grain storage in silos plays a fundamental role in preserving the quality and safety of agricultural products. This study presents a comparative evaluation of two-dimensional (2D) and three-dimensional (3D) mathematical models to predict the temperature and moisture distribution during unventilated corn storage in cylindrical silos with conical roofs. The models incorporate external temperature fluctuations, solar radiation, grain moisture equilibrium with air humidity via sorption isotherm (water activity), and grain respiration to simulate real-world storage conditions. The 2D model offers computational efficiency and is suitable for preliminary assessments but simplifies natural convection effects and underestimates axial temperature gradients. Conversely, the 3D model provides a detailed representation of heat and moisture transfer phenomena, capturing complex interactions such as buoyancy-driven flow and localized effects of solar radiation. The results reveal that temperature and moisture accumulation are more pronounced in the upper regions of the silo, driven by solar radiation and natural convection, with significant implications for large-scale silos where thermal inertia plays a key role. This dual modeling approach demonstrates that while the 2D model is valuable for quick evaluations, the 3D model is essential for comprehensive insights into thermal and moisture gradients. The findings support informed decision-making in silo design, optimization, and management, enhancing grain storage strategies globally.

The metal silo: An effective grain storage technology for reducing post-harvest insect and pathogen losses in maize while improving smallholder farmers’ food security in developing countries

Numerical modelling of temperature variations in a Chinese solar greenhouse

Overheating phenomena induced by fully-glazed facades: Investigation of a sick building in Italy and assessment of the benefits achieved via fuzzy control of the AC system

Classic PID-based control strategies for raceway photobioreactor biomass concentration and water level