Postharvest Storage Losses of Cereal Crops: A Critical Review

Postharvest losses (PHL) of cereal crops represent a significant challenge to global food security, particularly in developing countries. This comprehensive review explores the current status of cereal storage losses, identifies contributing factors, and evaluates potential solutions, with a focus on hermetic storage technology.

The Global Food Security Challenge and the Role of PHL

Meeting the food demands of a burgeoning global population is a pressing concern. With projections indicating a population of 9.1 billion by 2050, food production must increase by approximately 70% [1, 2, 3]. This growth is primarily expected in developing countries, many of which already grapple with hunger and food insecurity. Urbanization, climate change, and land allocation for non-food crops exacerbate these challenges. While traditional strategies have focused on improving agricultural production and land use, postharvest loss, a crucial aspect, remains underfunded and under-researched [4, 5, 6, 7]. Globally, roughly one-third of produced food, equivalent to 1.3 billion tons and valued at approximately US $1 trillion, is lost annually during postharvest operations [8]. This “food loss,” defined as food suitable for human consumption but ultimately unconsumed [9, 10], represents a significant missed opportunity. Addressing PHL requires comparatively modest investments and offers substantial returns compared to increasing crop production.

Understanding Postharvest Loss in the Food Supply Chain

Postharvest loss encompasses food lost throughout the supply chain, from harvest to consumption [9]. These losses manifest in various forms, including weight loss due to spoilage, quality degradation, nutritional loss, reduced seed viability, and commercial loss [11]. The magnitude of PHL varies significantly across crops, regions, and economies. In developing countries, despite resourcefulness, significant losses occur due to knowledge gaps, inadequate technology, and insufficient storage infrastructure. Conversely, developed nations experience lower losses mid-supply chain due to advanced technologies and efficient handling systems. However, substantial food waste occurs at the consumer end [12]. “Food waste” refers to discarded food, intentional non-food use, or spoilage/expiration [12]. In 2010, the United States alone wasted an estimated 133 billion pounds of food, representing 31% of the total available food, at the retail and consumer levels. Studies indicate that cereals, root crops, and fruits and vegetables account for approximately 19%, 20%, and 44% of losses by weight, respectively [8, 13]. When considering caloric content, cereal losses constitute the largest share (53%). Given the importance of cereals like wheat, rice, and maize as staple foods, minimizing their losses is crucial for food security, combating hunger, reducing land requirements, and improving rural livelihoods.

The Economic, Social, and Environmental Impact of PHL

PHL translates to direct physical and quality losses, diminishing the economic value of crops or rendering them unfit for consumption. In extreme cases, losses can reach 80% of total production [14]. African countries, facing low agricultural productivity in many regions, experience losses estimated between 20% and 40% [15]. The World Bank reports that sub-Saharan Africa (SSA) loses approximately USD 4 billion worth of food grains annually [16]. These losses profoundly impact millions of smallholder farmers, affecting food availability and trade values. Beyond economic and social implications, PHL has significant environmental consequences. The wasted resources used in producing lost food—land, water, and energy—contribute to environmental degradation. Uneaten food also generates additional CO2 emissions [17]. The FAO estimates that unconsumed food generates about 3.3 gigatons of CO2 equivalent emissions, excluding land use change [17]. The global blue water footprint (water used during the food lifecycle) for wasted food is estimated at 250 km3 [14, 17]. Land, another precious resource, is similarly wasted. A Nigerian study revealed that lost paddy rice accounted for 19% of the total cultivated area [18]. Globally, in 2007, about 1.4 billion hectares of land—an area larger than Canada and China combined—was wasted growing food that went unconsumed [19].

Focusing on Storage Losses: A Critical Issue in Developing Countries

Given the crucial role of PHL reduction in enhancing food security, understanding the patterns, scale, causes, and potential solutions, particularly in developing countries, is paramount. While losses occur throughout the supply chain, storage losses are especially critical in these regions. This review focuses on the status of storage losses for major cereal crops, the key factors contributing to these losses, and potential solutions. Technological interventions, particularly hermetic storage, hold significant promise. While numerous efforts have focused on developing and disseminating these technologies for smallholder farmers, a comprehensive, evidence-based assessment of their effectiveness across various crops is lacking. This paper addresses this gap by examining the use and effectiveness of hermetic storage in mitigating storage losses, especially for smallholders in developing countries.

Cereal Grain Storage Practices: Traditional and Improved Methods

Traditional storage methods in developing countries often involve simple structures like woven baskets, clay pots, or raised platforms. These methods, while culturally ingrained, offer limited protection against pests, moisture, and temperature fluctuations, leading to significant losses. Improved storage practices, incorporating hermetic technology, offer a viable solution.

Hermetic Storage: A Promising Technology for Reducing PHL

Hermetic storage involves storing grain in airtight containers that limit insect infestation and preserve grain quality. This technology creates a modified atmosphere within the storage unit, depleting oxygen and increasing carbon dioxide levels, effectively controlling insect populations without the use of chemical insecticides.

Types of Hermetic Storage Solutions

Several hermetic storage solutions exist, catering to different scales and needs. These include:

• Metal silos: Robust and durable, metal silos offer long-term storage solutions but can be expensive for smallholder farmers.
• Plastic containers and bags: Cost-effective and readily available, plastic containers and bags provide a practical option for small-scale storage. Super Grain Bags, a specific type of hermetic bag, have gained popularity due to their ease of use and effectiveness.
• Flexible hermetic storage structures: These structures offer larger storage capacities and can be adapted to various settings.

Effectiveness of Hermetic Storage

Studies have demonstrated the efficacy of hermetic storage in significantly reducing storage losses across various cereal crops. These studies have shown reductions in insect infestations, preservation of grain quality, and extended storage life. Specifically, research has documented the effectiveness of hermetic bags in minimizing losses in maize, wheat, and rice.

Benefits of Hermetic Storage for Smallholder Farmers

Hermetic storage offers several advantages for smallholder farmers, including:

• Reduced losses: By minimizing insect damage and preserving grain quality, hermetic storage increases the marketable yield.
• Improved food security: Preserving grain allows farmers to store food for longer periods, ensuring food availability during lean seasons.
• Increased income: Higher quality grain fetches better market prices, leading to increased income for farmers.
• Reduced reliance on chemical insecticides: Hermetic storage eliminates the need for chemical insecticides, promoting environmentally friendly practices and safeguarding human health.

Challenges and Opportunities for Scaling Up Hermetic Storage

Despite its proven effectiveness, scaling up the adoption of hermetic storage faces several challenges, including:

• Awareness and training: Many farmers lack awareness of hermetic storage technology and its benefits. Effective training programs are essential for promoting adoption.
• Access and affordability: Ensuring access to affordable hermetic storage solutions, particularly for resource-constrained farmers, is crucial.
• Quality control and standardization: Maintaining quality control and standardization of hermetic storage products is essential for ensuring their effectiveness.

Addressing these challenges through targeted interventions can unlock the full potential of hermetic storage in contributing to global food security.

Conclusion: Investing in Postharvest Loss Reduction for a Sustainable Future

Postharvest loss reduction, particularly in cereal crops, is a vital component of achieving global food security. Hermetic storage offers a promising technological solution, particularly for smallholder farmers in developing countries. Investing in research, development, and dissemination of hermetic storage technologies, coupled with effective training and awareness programs, can significantly reduce losses, improve livelihoods, and enhance global food security. Further research is needed to evaluate the long-term impact of hermetic storage and to optimize its implementation in diverse contexts. By prioritizing postharvest loss reduction, we can move towards a more sustainable and food-secure future.

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