Over one-sixth of all food produced globally ends up thrown away, a UN analysis has found. Around 931 million tonnes of food went into the waste bins of households, retailers, restaurants and other food services in 2019.

The United Nations Environment Programme (UNEP) and UK charity WRAP, which promotes sustainability, looked at food waste in retail outlets, restaurants and homes by reviewing government data and academic studies across 54 countries with a mix of incomes.

Their joint  found that 17 per cent of all food produced is thrown away by consumers. Most of this waste – 11 per cent of total food – occurs in homes. Globally, the average person throws away 121 kilograms of food, with 74 kg of this happening within households.

Food waste isn’t just a problem in high-income countries, the report found. On average, the annual per capita food waste in homes is 79 kg in high-income countries versus 91 kg in lower middle-income countries.

The report included both edible and non-edible waste, such as bones or vegetable peelings that must be thrown away. Lower middle-income countries may have higher per capita food waste because food is more often prepared from scratch, which might increase inedible food waste.

“A lot more data on edible and non-edible food waste in households is needed, especially in lower middle-income countries,” says a spokesperson for UNEP.

Food losses pre and post-harvest and food waste by consumers has a substantial impact on the environment and climate change, making up around 9 per cent of global greenhouse gas emissions. It also increases demand on land for agriculture and raises water use.

that 690 million people go to bed hungry, a number expected to rise sharply as a result of the coronavirus pandemic, and 3 billion people can’t afford a healthy diet.

Reducing food waste is vital and all individuals have a part to play, says Richard Swannell at WRAP. “Rather than focussing on supply chains, we need to tackle food waste inside homes with behaviour change campaigns,” he says.

Sign up to our free Fix the Planet newsletter to get a dose of climate optimism delivered straight to your inbox, every Thursday

A 10,000-kilometre-long fibre-optic cable owned by Google that is at the bottom of the Pacific Ocean can be used to detect deep-sea seismic activity and ocean waves.

Zhongwen Zhan at the California Institute of Technology in Pasadena, California, and his colleagues, including researchers at Google, used traffic data from one of the tech giant’s optical fibres to measure changes in pressure and strain in the cable. Using this data, they could detect earthquakes and ocean waves called swells generated by storms.

Over a nine-month period, the team recorded around 30 ocean storm swell events and around 20 earthquakes over magnitude 5 – strong enough to damage buildings – including the . The team had wanted to measure a tsunami, but none occurred during the monitoring.

Deploying and maintaining geophysical instruments on the seafloor is difficult and expensive, so underwater seismic stations are relatively rare. Anthony Sladen at the University Côte d’Azur in France says that the study is “a major step in exploiting the benefits of existing cables”.

There have been previous efforts to use fibre-optic cables as seismic sensors, but these required specialised laser-detection equipment at both ends of the cable or the use of dedicated fibres within the cables. Such fibres are in short supply on deep-sea cables, so dedicating one to measuring earthquakes would be difficult.

Zhan says his team’s approach of using an existing traffic fibre is more flexible and scalable as it doesn’t need new infrastructure. “This is exciting as if only a fraction of the million kilometres of submarine fibre-optic networks could be used as sensors, there would be vast improvements in the amount and coverage of seismic data.”

Nature sanitises around 38 million tonnes of human waste per year – the equivalent of around £3.2-billion-worth of commercial water treatment.

Alison Parker at Cranfield University in the UK and colleagues looked at 48 cities in Africa, Asia, North America and South America. They analysed how much human waste is produced and where it ends up by reviewing existing data from interviews, observations and direct field measurements.

The team looked at waste management not connected to sewers. This included pit latrines and septic tanks where waste is primarily contained on-site – in a hole below the ground for pit latrines and in box tanks for septic tanks.

Liquid waste from pit latrines and excess water from septic tanks can gradually filter through soil – a process that cleans it before it reaches groundwater. However, this doesn’t happen in cities where the water table is shallow or where large volumes of waste are discharged in a crowded area. Instead, the liquids can contaminate ground water, posing a health risk.

With 892 million people, predominantly in low and middle income countries, using this type of waste management, the researchers estimate that nature safely treats around 38 million tonnes of human waste per year. The team did not look at how much waste is not safely treated.

More than 4 billion people don’t have access to safe sanitation services, with one-third living in low income countries. Unsafe sanitation is responsible for 775,000 deaths each year.

“Sanitation that involves the ground naturally treating waste can be part of the solution,” says Parker. However, pit latrines, septic tanks and other natural waste management options only work if the soils can filter the waste or if the waste dumped in rivers can be diluted safely without causing harm to the environment, which is not always the case.

Duncan Mara at the University of Leeds, UK, says that approaches like this cannot be the “be-all and end-all” as every person on this planet should be given access to sanitation which is safe for the environment and protects human health. This should include also sewers in crowded areas as they are safer.