How collecting food waste could slow climate change – and save us money

Cleaning up. Image: Getty.

Food waste is a global problem, and one that’s driving climate change. Here in the UK, the country’s biodegradable waste goes to a landfill, where it breaks down to produce methane, a gas that is roughly 30 times as bad as carbon dioxide.

And yet there’s a simple solution. With the exception of garden waste, which often contains lignin from woody matter, all biodegradable materials, including much of our food waste, could instead be processed in anaerobic digesters. This decomposition in an atmosphere devoid of oxygen produces biogas, which can then be used to generate heat and electricity.

This is more or less the same process that takes place in landfill sites, except that the biogas can’t escape from an anaerobic digester as it can from landfill – meaning the breakdown of the organic matter takes place in an environment that is enclosed and controlled.

The result is biogas consisting of 60 per cent methane and 40 per cent carbon dioxide, which can be burnt in order to generate heat or used as a fuel for vehicles. It could also be used to generate electricity after the biogas has been scrubbed, which can then either power the anaerobic digester or be exported to the national grid. The process also produces digestate, a solid and liquid residue that can be returned to farmland as a soil conditioner. The amount of biogas and the quality of digestate varies according to what feedstock is used in the digester.

This process is already widely used both across Europe – particularly in Denmark, Sweden, Germany and Austria – and elsewhere globally, particularly in India and Thailand. What's more, this move towards separate food waste collection is already happening in countries outside the UK, and its momentum is increasing according to the World Biogas Association. Already, major cities, including New York, Paris, Oslo, Copenhagen, Auckland, San Francisco, Mexico City and many others are regularly collecting food waste from their citizens. The decisions to do so are usually taken at city level, but enabling legislation from national governments assist in this.


At present the UK is lagging behind. Only 109 local authorities in England, about 33 per cent of the total number, collect food waste as of May 2018, according to the Anaerobic Digestion and Bioresources Association (ADBA). Yet making a separate food waste collection mandatory across the UK and running the food waste through anaerobic digesters, could supply enough biogas to generate 36 per cent of UK electricity, according to a 2007 Friends of the Earth report. This percentage could be increased again if food waste from restaurants, cafeteria and retailers was also collected. 

ADBA’s research also suggests that universal separate household food waste collections would trigger the construction of around 80 new anaerobic digester plants for food waste processing. This would add an extra 187 megawatts equivalent (MWe) of capacity, powering 285,000 extra homes – representing all the homes in a city the size of Glasgow. Data from WRAP suggests that further food waste collection from businesses would add around a further 10 per cent, depending on the quality of the feedstock collected and what exemptions were applied (for example, it might only apply to businesses collecting more than 50 kilograms per week or the lower threshold of 5kg).

A 38 per cent improvement in food waste collection from flats in Ealing alone could generate £26,000 of annual savings for the London borough, £28,000 in revenue for a local anaerobic digester (based on electricity sales to the national grid) and reductions in carbon dioxide emissions of around 270 tonnes, found Londoners Lab, a collaborative project consisting of Greater London Authority, University College London, Ferrovial Services Centre of Excellence for Cities and Future Cities Catapult.

ADBA has been campaigning on this issue for a while, but the good news is that the government finally signalled its intention to introduce separate food waste collections in its forthcoming Resources & Waste Strategy, which will ensure that all homes and suitable businesses in England will have access to food waste collections by 2023. The next step, following the government announcement, is a consultation, but it is widely acknowledged that additional funding would be needed by local authorities to achieve this, as the business case isn’t currently strong enough.

 
 
 
 

Wild boar are moving back to Genoa, and not everyone is pleased

A wild boar, c1933. Image: Getty.

Crossing the Ponte Gerolamo Serra in the Italian city of Genoa, I spotted a small crowd clustered by the river wall. I approached, intrigued, and peered over the wall to discover the subject of their delight: a sounder of eight wild boars – the adults sheltering from the heat in the undergrowth, while the juveniles foraged among the foliage that grows in the river bed during the dry summer months.

In any other city, such a sight might have been surprising. But in Italy, and particularly in the region of Liguria, where Genoa is located, the population of wild boars has been increasing at such a rapid rate that these incidents are now common. Across the country, it’s estimated that the population has risen from 600,000 to 1m over the past decade.

But while wild boars may look comically out of place trotting about the city, it’s actually a natural result of the way people have migrated – and the wars they have fought – over the course of recent history.

Making a comeback

A species native to Europe, the wild boar (or “cinghiale”, in Italian) largely disappeared from its historical territories during the 18th and 19th centuries. Their decline was widely attributed to the combined effects of habitat change, competition for space and resources and, of course, hunting.

Wild boars were a prized quarry, revered for their ferocity – and the danger involved in pursuing them. According to local folklore from the region of Liguria, the last truly wild boar was hunted and killed in 1814, in the province of Savona.

After an absence of more than a century, wild boar began to return to Liguria, and to the neighbouring region of Piedmont. A further influx occurred during World War I, when it’s believed that military activities in the south-east of France forced parts of the population back into Italy over the Alps.

Although hunting fraternities were quick to augment this fledgling population with wild boars transported from elsewhere, the return of the species was primarily due to natural causes. From the 1950s onwards, traditional agricultural practices were abandoned as more and more people moved from rural towns into the cities. This meant that large areas of formerly cultivated terraces and pastures were rapidly overgrown, fast becoming dense secondary woodlands.

A city gone wild

This spontaneous “rewilding” has become a controversial issue in the region. Many conservationists and environmental organisations consider the region’s return to a “wild state” a success. But others believe that the encroaching wilderness signals a loss of traditional woodland knowledge and a reduction of biodiversity, associated with the pastures and meadows.


The province of Genoa is among the areas most densely populated by wild boar in Italy, with an estimated 25 boar per 10km². Rewilding processes have brought woodlands to the city limits, blurring the boundary between rural and urban areas. The species has expanded beyond the hinterlands, colonising highly urbanised, densely populated city spaces in Genoa, drawn by the abundance of food waste created by humans.

In 2009, the infamous boar Pierino made his home at Righi, on the outskirts of Genoa, where he was routinely fed with focaccia by enthusiasts. Today, a family of wild boar call the Albergo dei Poveri – a historical hostel for the Genoese poor in the city centre – their home.

But while their antics are often recorded and shared with glee on social media, the threats posed by the presence of wild animals has become a preoccupation for the city’s municipal administration.

Boorish behaviour

Wild boar have been involved in a number of traffic accidents, and have proven to be particularly dangerous when with their young, attacking dogs and even people. The city council in Genoa has put forward many proposals to reduce the number of animals in the city, ranging from forced removals, to sterilisation, increased attention to waste disposal and approved hunts. About 90 wild boar were reportedly culled in 2018.

Needless to say, each of these measures has been hotly debated. Animal advocacy groups staunchly oppose the proposals, and sometimes obstruct the authorities’ attempts to take action, often sending patrols to care for the animals, and even give them names. But other residents are displeased with the animals’ presence in the city, and have consulted with the council on how to address the problems that they cause.

And so Genoa continues to grapple with thorny issues surrounding the presence of wild boar in the city, with the city authorities seeking to resolve a polemical issue that embroils the lives of animals and humans alike. So far, a collective, coherent and communally agreeable strategy has proven evasive; one that considers the need for public safety, hygiene and health with the ethical responsibilities towards to wild boar themselves.

Meanwhile, the animals themselves continue to lounge and forage beneath the Ponte Gerolamo Serra and elsewhere, bringing a little of the wilderness into the city.

The Conversation

Robert Hearn, Assistant Professor in Human Geography, University of Nottingham.

This article is republished from The Conversation under a Creative Commons license. Read the original article.