We’ve all done it. You buy a bunch of bananas, take one before placing the rest in the fruit bowl and then go on with your life, rushing to work in the morning, walking the dog in the evening and generally forgetting about your purchase. Ten days later, they look brown and pitiful. So instead of making a smoothie or a banana cake, you throw them away, wondering aloud what made them go brown so fast.

And it’s not just bananas. Overall, a third of food is wasted or lost – either before or during harvest, on its way to consumers or, as with bananas in the fruitbowl, after it has been bought.

In our complex and globalised food system, something is going awry between farm and fork. If we are to a growing world population while cutting carbon emissions and minimising environmental impact, then tackling excessive food waste is one of the biggest challenges. 

Bananas, as the one of the most popular fruits in the world, are not a bad place to start. The banana industry is worth $36bn (£28.4bn) a year. But each year hundreds of thousands of tonnes are lost or wasted. The UK-based agri-tech startup Tropic Biosciences aims to change that.

The company wants bananas to last longer – not before they turn brown but before they ripen in the first place. By looking closely at the fruit’s genome, the company’s scientists can locate genes involved in making a fruit hormone called ethylene. This hormone is crucial to the ripening process. The aim is then to edit these genes, so that the ripening process is delayed and shelf life extended.  

This could help traders as they move fruit across the world, from producers in regions such as Latin America or Asia to markets elsewhere.

“By extending the shelf life, you can reduce wastage in transportation,” says Gilad Gershon, chief executive of Tropic Biosciences. “Banana is the most shipped fruit in the world. If we can reduce wastage by a few percentage points, the impact on the environment and on margins is quite significant.”

For decades, the race to feed more people has been a matter of how much produce farmers can grow. Questions abound: is your land fertile enough? Are you using the right plant? Did you harvest at the right moment? But increasingly, the world is noticing that much of that food is never eaten in the first place. 

The issue of food loss and food waste took off in 2011 when the UN Food and Agriculture Organization (FAO) commissioned a special report into how efficient – or inefficient – our food chain was. The study concluded, based on some rough estimates, that globally one-third of food produced for human consumption is lost or wasted.  

“Think about the land, the energy, the water that goes into producing that food, into getting it to the consumer,” says Rose Rolle, food loss and waste team leader at the FAO. “When you throw away food, all those efforts and resources are also thrown away.” 

From their lab in Norwich, Tropic Biosciences works to address this situation from the outset. “You might use different cooling or transportation technologies, but if you address the genetics early on, the impact can be higher,” says Gershon. 

Food products made from gene-edited crops are already being sold in the US, and countries such as Japan and Argentina have light regulations in place for such crops. However, in the EU, there are much heavier regulations, considering gene-edited crops on a par with traditionally genetically modified organisms (GMOs), with fewer being developed as a result.

Mangoes are relatively simple fruit to deal with when it comes to ripeness. An unripe mango is hard and an overripe mango is very squishy – immediately obvious to the touch. But some fruits pose a much greater challenge.

Avocados are more deceptive. One in five will either never ripen or is overripe when it reaches consumers. So the scientists at Wageningen University and Research (WUR) are looking for a way to predict when an avocado will be at its prime.

“As long as quality is above a certain threshold, we consider it food. If it goes below, then we consider it waste,” says Eelke Westra, programme manager at WUR’s Post-Harvest Quality Programme. “My job is to keep it above that threshold.”

European markets in particular are currently dominated by ready-to-eat avocados, fruits that are just right on the day they’re sold. As such, they must be kept in special ripening rooms until they are close to the desired quality. Then they are quickly transported to shops and markets where they are sold.

But deciding when an avocado is ripe is tricky. When a machine takes skin samples or drills into the flesh to detect the ripeness of a sample, it also spoils the avocado. One solution is to take acoustic measurements instead. “You knock the fruit and measure the sound going through the food as a measure of firmness,” says Westra. Or you can project an infrared light beam on the fruit, with a sensor picking up the light reflected by the avocado: some wavelengths are absorbed by its molecules, while others are reflected. “The whole reflective spectrum is a measure for the firmness of the avocado,” he says.

Some versions of these technologies are currently used in European storage rooms, days or weeks before the fruits are harvested. But even this method of ripeness-testing might not be enough to prevent waste. Avocado batches are infamously diverse, with one fruit’s ripeness varying wildly from the next.

Researchers at WUR are looking into two possible solutions: expanding current processing power to monitor each fruit individually, or even more ambitiously, to start scanning the fruits before they are harvested.

Yet another is to accept that just as fruits are not all alike, people’s tastes aren’t either. “If we can make use of natural variations in food and veggies, knowing the preferences of each consumers, we could pair them,” says Westra, dreaming of a world where each person’s tastes can be satisfied if previously understood.

And Westra is not the only one aware that individual differences between fruits plays a major role in waste.

What’s the biggest contributor to landfills and incinerators in the US? Yes, food. The Environmental Protection Agency (EPA) estimates that food constitutes 21.6% of discarded solid waste. And because this falls within municipal jurisdiction, there’s one key player to involve in food loss and food waste prevention: cities.

“Cities are both uniquely positioned to deal with food loss and food waste and highly motivated to do so,” says JoAnne Berkenkamp, senior advocate at the Healthy People & Thriving Communities Program at the Natural Resources Defense Council. Municipal authorities want to free landfills and feed those who are food insecure, while also reaching related targets like reducing greenhouse gas emissions.

Beyond the toll it takes on resource use, discarded food is a major contributor to climate change. When food is left to rot in landfills, it releases methane, a powerful greenhouse gas that’s many times more damaging than carbon dioxide (CO2). Food loss and food waste contribute close to 8% of global emissions.

“If food loss and waste were a country, it would be the third-largest emitter of greenhouse gases after China and the US,” says Berkenkamp.

Along with two colleagues, in 2017 she produced a report that looked precisely into how cities can reduce food loss and waste, with a focus on New York, Nashville and Denver. Her team discovered that each person was throwing away an average of 900g of edible food a week; 68% of all the food that ended up in the bin was edible.

In many parts of the world beyond the US, the problem is the same. The difficulty is not that there isn’t enough food to go around, but that only some people can access it.

Tatiana Vargas coordinates the Costa Rican charity Plato Lleno (or “Full Plate”), which aims to “rescue” edible food that would otherwise be thrown away. Her organisation picks up leftover meals from events and restaurants and delivers them to orphanages, elderly homes and food banks.

Organisations like Plato Lleno work at the end of the food value chain. It’s always better to prevent waste at earlier stages, for instance educating consumers about how to calculate for events, but if those previous steps fail, they act as a safety net. Beyond food rescue and donation, the only options are composting or animal feed.

Late on a Thursday evening, Vargas waits with two colleagues, nutritionist Carolina Bolaños and graphic designer Gidget Monge at a diner, closing for the day with 30 loaves of bread that wouldn’t be used the next day. It takes no more than five minutes and one person to collect them, so they combined the rescue mission with a chance to chat about their work.

“It’s a shame when this happens and there’s no-one to pick it up,” says diner Darling Noguera, who says in other places she’s worked they have had to regularly throw away perfectly edible food. “One thinks about homeless people who have nothing to eat.”

So far, Plato Lleno has collected 10.6 tonnes of food in less than 500 missions.  Before their work began, restaurants and catering services were throwing everything to the bin. “They were literally paying to have someone take good food to the dump,” says Vargas.

Similar organisations are springing up all over the world – some of them, like the app Too Good To Go, now operating across several countries in Europe.