Causes and Prevention of Post-Harvest Losses

Every year, a significant portion of food grains, pulses, and oilseeds produced by farmers never reaches the consumer’s plate. These are post-harvest losses – the gap between what is harvested and what actually becomes available for consumption. In India, these losses can range from about 4% to nearly 10% depending on the commodity, translating into thousands of crores of rupees worth of food wasted annually. Understanding the causes behind these losses – and the technologies that can prevent them – is essential for improving food security and farmer incomes.

What are post-harvest losses? 🔗

Post-harvest loss refers to the reduction in quantity and quality of food produce that occurs between the time of harvest and the point of final consumption. These losses happen across the entire supply chain – during harvesting, threshing, drying, storage, processing, and transportation. They include physical weight loss from spoilage and spillage, quality degradation from moisture or pest damage, nutritional loss, and reduced commercial value.

According to a study published in the journal Foods, roughly one-third of all food produced globally – approximately 1.3 billion tonnes worth about USD 1 trillion – is lost or wasted in post-harvest operations each year. In developing countries like India, these losses are primarily driven by inadequate infrastructure and outdated technologies rather than consumer-level waste.

The scale of post-harvest losses in India 🔗

Two major government-commissioned studies have quantified post-harvest losses in India. The ICAR-CIPHET study (2015) and the NABCONS study (2022), both conducted under the Ministry of Food Processing Industries, provide the most comprehensive data. According to the NABCONS 2022 findings presented in the Lok Sabha, cereals suffer losses between 3.89% and 5.92%, pulses between 5.65% and 6.74%, and oilseeds between 2.87% and 7.51%.

In absolute economic terms, India loses food worth approximately ₹1.53 lakh crore (around USD 18.5 billion) every year across all agricultural commodities, as reported by the ICRIER-ADMI study based on NABCONS data. These numbers are staggering, particularly when a large section of the population still faces food insecurity.

Causes of post-harvest losses 🔗

Post-harvest losses are not caused by a single factor. They result from a combination of biological, environmental, and systemic inefficiencies at every stage of the supply chain.

Losses during harvesting and threshing 🔗

The supply chain begins at the farm, and losses start right at harvest. Harvesting at the wrong time – too early or too late – leads to significant problems. Early harvesting at high moisture content increases the cost of drying and makes grains susceptible to mould and breakage. Delayed harvesting results in shattering losses and exposes the crop to birds, rodents, and weather damage. A Punjab-based study found that delayed wheat harvesting increased losses from about 1.5% to 2.5%, roughly a 67% increase.

Manual threshing, still common in many parts of India, causes grain spillage, breakage, and incomplete separation of grain from chaff. Similarly, traditional winnowing can result in losses of up to 4% of total production.

Losses during drying 🔗

Proper drying is critical because most grains need to reach a safe moisture level (below 13%) before storage. Sun drying – the most widely used method in rural India – is slow, weather-dependent, and exposes grains to contamination from dust, stones, and animal droppings. Grains laid out on roadsides or open grounds are vulnerable to birds, insects, and unseasonal rains. When grains go into storage without adequate drying, the resulting high moisture encourages rapid mould growth and mycotoxin contamination.

Inadequate storage facilities 🔗

Storage is the stage where the largest chunk of losses occurs in developing countries. In India, roughly 50-60% of harvested grains are stored in traditional structures – earthen pots, mud bins, bamboo baskets, gunny bags, and small rural godowns (warehouses). These structures are made from locally available materials, lack scientific design, and cannot protect grains from insects, rodents, or moisture fluctuations over long periods.

Temperature swings between day and night cause moisture to migrate within the grain mass, creating pockets of dampness that become hotspots for fungal growth. Poorly maintained rural godowns often have leaking roofs, cracked walls, and inadequate ventilation, making them particularly prone to pest infestations.

Among all biotic factors, insect pests are considered the most damaging during storage, causing 30-40% of storage losses in some cases. Storage pests such as the rice weevil (Sitophilus oryzae), the pulse beetle (Callosobruchus maculatus), and the larger grain borer (Prostephanus truncatus) feed on stored grains, reduce their weight, and contaminate them with excreta and body fragments. Rodents are another major problem in rural godowns, eating and contaminating stored grain.

Mycotoxin contamination 🔗

Fungi such as Aspergillus flavus and A. parasiticus produce aflatoxins – highly toxic compounds that make grains unfit for human consumption and pose serious health risks, including increased risk of liver cancer. Globally, an estimated 4.5 billion people in developing countries are exposed to aflatoxins through contaminated food. High moisture and warm temperatures in storage create ideal conditions for these fungi to thrive. Oilseeds are especially vulnerable because their high oil content can degrade rapidly in damp conditions, producing elevated fatty acid levels and sometimes even self-heating.

Processing losses in pulses and oilseeds 🔗

Beyond storage, substantial losses occur during the processing stage itself – particularly for pulses and oilseeds.

Low dal recovery in pulse milling 🔗

In India, most pulses are consumed as dal – dehusked and split forms. The milling process involves cleaning, dehusking (removing the outer husk), and splitting the grain into two halves. The majority of pulse milling in India is done using traditional mills that rely on carborundum emery rollers for dehusking and burr grinders for splitting.

The problem is that traditional conditioning methods do not adequately loosen the husk, so multiple abrasive passes are required. Each pass generates broken pieces and powder, reducing the yield of usable dal. As a result, traditional mills yield only about 65-75% dehusked splits, compared to a potential recovery of 82-89%. The remaining 5-15% is lost as broken grains and powder. This gap between actual and potential recovery represents a significant economic loss for both millers and consumers, and contributes to higher dal prices.

Research into improved pulse processing technologies – such as cylinder-concave dehullers, pre-milling treatments (soaking and oil application), and controlled thermal conditioning – has shown that dehulling efficiency can be significantly improved. For instance, the CFTRI mini dal mill developed in India achieves much higher dal recovery rates compared to traditional equipment.

Residual oil in oilseed cakes 🔗

When oilseeds like mustard, groundnut, soybean, or sunflower are processed, the extracted oil is the primary product. The leftover solid material is called oilcake (or khali). In traditional mechanical pressing – still widely used in small-scale operations across India – the oilcake retains around 8-12% residual oil. This represents a substantial portion of oil that remains unextracted, meaning lower oil yield for the processor and higher cost for the consumer.

Modern solvent extraction plants, which use hexane to dissolve remaining oil from pressed cake, can recover over 99% of available oil, leaving less than 1% residual oil in the meal. However, small-scale processors and village-level expellers typically cannot afford solvent extraction technology and continue to operate with mechanical presses that leave significant oil behind.

Transportation and handling losses 🔗

Moving grain from field to market adds another layer of loss. In many parts of rural India, grains are transported in bullock carts, open trolleys, or poorly maintained trucks over bad roads. Bags are loaded and unloaded multiple times – sometimes up to ten times before the grain reaches a mill. Each handling step leads to spillage. Low-quality jute and polypropylene bags tear easily, especially when heavy hooks are used for lifting. The result is a steady trickle of grain lost during transit.

Technologies and strategies to reduce post-harvest losses 🔗

The good news is that most post-harvest losses are preventable with the right mix of technology and practice.

Improved storage technologies 🔗

Scientific storage can reduce losses from double digits to under 2%. Some of the most promising options include:

Hermetic (airtight) storage: This method uses sealed bags or containers to create a low-oxygen, high-carbon-dioxide environment through natural respiration of the grain and any organisms present. This kills insects without the use of chemicals. Technologies such as PICS bags (Purdue Improved Crop Storage), SuperGrain bags by GrainPro, and metal silos have shown excellent results. In trials across Africa and Asia, properly sealed hermetic storage units reduced food losses by up to 98% compared to traditional storage.

Metal silos: Made from galvanised steel sheets, these cylindrical structures provide airtight, rodent-proof, and moisture-resistant storage. While the initial investment is higher, their durability and low maintenance make them cost-effective over time.

Modern warehousing: India’s government has launched ambitious initiatives to expand grain storage capacity. The World’s Largest Grain Storage Plan in the cooperative sector, launched in 2024, aims to add 70 million metric tonnes of storage capacity over five years, with an estimated investment of ₹1.25 lakh crore.

Improved processing technologies 🔗

For pulses, upgrading from traditional emery roller mills to modern cylinder-concave dehullers and CFTRI-type mini dal mills can dramatically improve dal recovery rates. Pre-milling treatments such as controlled soaking, oil application, and thermal conditioning help loosen the husk, reducing the need for aggressive abrasive dehusking and thereby cutting losses from broken and powdered grain.

For oilseeds, transitioning from simple mechanical expellers to double-pressing systems or combining pre-pressing with solvent extraction can recover a much larger proportion of the available oil. Even newer approaches like enzyme-assisted extraction and gas-assisted mechanical expression (GAME) are being researched to improve oil yields while reducing energy consumption.

Government schemes and policy measures 🔗

Several Indian government programmes specifically target post-harvest loss reduction. The Pradhan Mantri Kisan SAMPADA Yojana (PMKSY) focuses on building post-harvest infrastructure and food processing facilities. The Agriculture Infrastructure Fund (AIF) provides medium and long-term loans for investment in warehousing and community farming assets. The Mission for Integrated Development of Horticulture (MIDH) works to strengthen post-harvest management infrastructure nationwide.

Farmer training and awareness 🔗

Technology alone is not enough. Farmers need training in proper harvesting timing, drying techniques, safe moisture levels for storage, and correct use of modern storage equipment. With 86% of Indian farmers being small and marginal operators, affordability and simplicity of solutions are as important as their effectiveness.

Why reducing post-harvest losses matters 🔗

Cutting post-harvest losses is one of the most resource-efficient strategies for improving food availability. Unlike increasing production – which demands more land, water, fertiliser, and energy – reducing losses works with what has already been produced. It lowers food prices, boosts farmer incomes, improves nutritional outcomes, and reduces the environmental footprint of agriculture.

As the ICRIER-ADMI report puts it, reducing post-harvest losses is far more cost-effective and gentler on natural resources – soil, water, air, and biodiversity – than simply producing more and losing more.

What do you think? Given that traditional storage and processing methods are still dominant in rural India, what would be the most practical way to encourage smallholder farmers to adopt modern post-harvest technologies – subsidised equipment, local training programmes, or cooperative-level shared infrastructure?

References

1. https://www.pib.gov.in/PressReleaseIframePage.aspx?PRID=1885038
2. https://pmc.ncbi.nlm.nih.gov/articles/PMC5296677/
3. https://icrier.org/pdf/Policy_Brief_20.pdf
4. https://indiaagronet.com/indiaagronet/post_harvest/pulses.htm
5. https://www.researchgate.net/publication/324247226_Performance_Evaluation_of_Pulse_Milling_Machines
6. https://encyclopedia.pub/entry/48281
7. https://officerspulse.com/2024/07/19/post-harvest-losses-in-agriculture/