Post-harvest losses are estimated to remove as much as 50% of crops from the food supply in developing countries. Moisture, infestation and rotting are major problems for farmers and processors, leading to reduced income and aggravating hunger.

Research and private sector organisations are coming up with solutions to combat post-harvest losses. These are a few of them:

Pics bags

Up to 50% of cowpeas, an important food crop in west and central Africa, are lost to weevil infestation. The Purdue Improved Cowpea Storage (Pics) bag – first developed in 2007 by Purdue University – provides a cheap solution.

The bag consists of two inner polyethylene plastic bags and an outer nylon sack. This reusable triple layer bag sells for $2 and seals the contents from oxygen, killing insects inside.

More than 3.2m Pics bags were sold across west and central Africa between 2007-2013, and farmers have started using them for other crops too.

“This technology has also contributed to price stabilisation,” says Sara Farley, chief operating officer and co-founder of the Global Knowledge Initiative (GKI), which researches post-harvest opportunities.

“Where consumers used to purchase cowpeas for as little as $20 per 100kg bag, the market price has stabilised at $40,” says GKI report Reducing Global Food Waste and Spoilage.

Solar bubble dryer

Farmers often depend on drying crops in the sun. Variable weather conditions make this risky, and crops may be exposed to vermin or contaminants.

In September 2014, GrainPro, the International Rice Research Institute and Germany’s Hohenheim University launched the solar bubble dryer. With a transparent polyethylene cover over a plastic floor, it’s like a bubble that traps solar radiation, with moisture expelled through mains power or solar-powered ventilators.

At $1,700 for the version, or $2,200 for the solar-powered version, the dryer is not cheap but will be a worthwhile investment for some.

“It’s especially beneficial to smallholders in developing regions where rapidly changing weather is contributing to massive food losses,” says Victor Dela Casa, a spokesperson for GrainPro

C:AVA

Cassava is a staple crop in Africa, but has a short shelf life after harvesting. One way of reducing losses is to process it quickly into high-quality cassava flour (HQCF).

The C:Ava project, led by the Natural Resources Institute (NRI), is working with partners in Ghana, Tanzania, Uganda, Nigeria, and Malawi to both improve yields and develop processing capacity for more than 90,000 cassava growers. It has trained farmers to grow different cassava varieties, and introduced graters and presses for on-farm pre-processing of raw cassava roots into wet cakes with a longer shelf life.

“We think it is important to consider post-harvest losses both from a physical loss perspective and from an economic loss perspective,” says Andrew Westby, director of the NRI. “The project has focussed on skill development to enable farmer enterprises to process products for higher value markets.”

Mud silos

These have been used in some parts of Ghana for hundreds of years, but are still not widespread. Constructed of local grasses and mud, these storage units contain several compartments for crops, and can store up to about 1.5 metric tonnes of grain. If well maintained, they can last up to 50 years.

Recently, a project led by the US-based Opportunities Industrialisation Centers International (Oici) has been introducing the silos to parts of Ghana where they are not traditionally used. Oici’s research has found that mud silos reduce losses to almost zero, provided grains are well dried and treated before storage to prevent rotting or infestation.

To date, Oici has constructed almost 6,000 mud silos in Ghana, costing less than $25 each. But while cheap and effective, further scaling up depends on raising awareness and acceptance in communities, and identifying appropriate local materials.

Intervention modelling tool

Development organisations or other actors trying to reduce post-harvest losses need to work out where to invest their efforts. A tool launched in July, also by the NRI, may help.

The graphical modelling tool identifies which interventions will be most effective for losses along a whole value chain. Users can experiment with investments in loss reduction, and a panel displays corresponding changes in loss values.

“It’s intended as an imaginative way of getting people to think about key factors affecting investment in loss-reduction projects,” explains Rick Hodges, visiting professor of grain post-harvest management at the NRI.

“It doesn’t make decisions for the user, but shows how three important factors – efficiency, adoption rate and investment – interact.”

Gum arabic coating

Modified atmosphere packaging slows decay, but is relatively expensive. Researchers at the Centre of Excellence for Post-harvest Biotechnology (CEPB) at the University of Nottingham Malaysia have come up with a cheap alternative: edible coatings, made of gum arabic.

CEPB’s research found that applying a solution with a 10% gum arabic edible coating delayed tomato ripening and meant the fruits could be stored for up to 20 days without deteriorating.

Gum arabic is derived from acacia trees native to the Sahel. This makes it a potentially sustainable tool for farmers in that region to use in post-harvest handling, though widespread use depends on the development of production and distribution channels, and raising awareness among smallholder farmers.

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