The world wastes around a third of all food produced every year.
In Australia, that equals more than 7 million tonnes of edible food, and is estimated to cost the economy more than $36 billion annually, according to a report commissioned by the federal government.
At the same time, many of us cook on gas, which is getting more expensive and contributing to greenhouse gas pollution.
But there's a growing movement of people and businesses looking to kill two birds with one stone.
Creating biogas at home from food waste, which can then be used for cooking, is getting simpler.
Some companies now offer larger-scale systems for restaurants and even refugee camps, as well as basic home set-ups.
Around six years ago, Annett and Paul ditched city life in Sydney and moved to northern New South Wales, where they built an off-the-grid tiny house.
As part of that set-up, they installed a biogas food digester that they feed food scraps and toilet waste.
From that organic material, the system produces methane, which is fed by a line to a gas stove-top in their house.
Annett says there are some days in summer when the system is most productive, and they struggle to keep up with the amount of gas it creates, which they use to subsidise their solar-powered electric cooker.
"It's good. We're basically using it in the mornings or at night when the sun's not out," Annett says.
Making gas pays for itself
Emissions from food waste make up about 3 per cent of Australia's total greenhouse gas emissions every year, according to data from the former federal government.
Around the world, it's closer to 8 per cent of emissions.
Although creating biogas at home is not a "panacea" for our food-based emissions, it is one potentially valuable piece of the puzzle, according to the authors of a 2019 Australian study.
In the case study the authors looked at, it turned out to be a financially viable option too.
That study found that enough gas was produced from a single household to cook for an average of nearly 38 minutes each day.
However, that included some days where no gas was used, and others where up to two hours of gas supply was used.
According to their data, a system would pay for itself in just over four years based on savings from purchasing gas alone.
And that was based on the lower gas prices of the time.
If savings from fertiliser, which is a by-product of creating methane from food waste, were also factored in, that payoff time would be shorter again.
Like Annett and Paul, Ned lives on an off-grid property near the Hawkesbury River in New South Wales and creates his own biogas.
"The bladder where the gas is stored lasts about two and a half hours' run time."
He says he realised the real utility of making his own biogas when his family was recently flooded in.
"[The delivery driver] couldn't get in to deliver a gas bottle," he says.
"This whole idea that you can always go to the shop and get things … that's not always the way."
He says their system doesn't produce enough gas to supply all their cooking needs, but it's excellent as a backup and for diverting waste from landfill.
"We probably don't have as much food waste as [the average family].
"We're a family of five — three little kids — the amount of gas cooking we do is probably more than we'd be able to generate on purely residential food waste consumption.
Annett says it's a similar case with her family's system.
In the beginning, they went to the farmers markets to get extra food waste to feed it, but now they're only using the gas as a backup.
"We're not feeding it as much as we could — you could feed it up to six litres [of food waste], per day but we're only adding about one to two.
"If you only use it for making coffee or tea you can use it every day but if you cook meals on it ... we have to watch it a little bit."
What if I live in an apartment?
There are other requirements for creating biogas at home too that mean it's not a viable option for everyone.
While there are a number of different systems, and some people even make their own bespoke versions, they all take up quite a bit of space and are probably not conducive to apartment living.
That's because unlike liquefied natural gas that we get in gas bottles, for instance, methane produced from food scraps remains in its expanded, gaseous form.
Ned's pretty handy and is looking into ways to compress his homemade methane, but for others that wouldn't be an option.
Another issue is temperature.
Anaerobic digestion stops below about 20 degrees Celsius, and has an optimum digestion temperature of around 35C.
Although an electric heating device is one option to keep production going in cold climates, Annett says their system slows significantly at this time of year.
So are there solutions for people without space or in colder climates?
Western Australia's City of Cockburn Council is collecting food waste from partners including fish and chips stores and bakeries.
They're then delivering that waste to a fertiliser plant where the methane is captured and used to power generators to produce electricity.
At their peak, they estimate the generators are supplying electricity from biogas to around 3,000 homes.
What began as a trial became a permanent service in 2021.
And Byron Shire is looking to implement a similar program permanently, which will also include waste from households.
Byron already has a three-bin system, with one dedicated to food waste that the eco-conscious community has got behind, according to bioenergy project manager John Hart.
With that waste collection system already in place, he says he's hoping to see their biogas generator up and running soon.
"We'd like to break ground in around February 2023 after the summer holidays and have the facility running a year later," he says.
As well as being a cheaper alternative than landfill for businesses, Mr Hart thinks with the rising costs of fuels and waste disposal, savings could filter back to ratepayers.
"The business case for this facility is that we're keeping it local. We'll be reducing truck movements and powering the council's largest sewerage treatment plant with green electricity.
"It stands to reason that residential rates will drop, which will be a huge success story for the local residential ratepayer."
A waste treatment solution for refugee camps
Internationally, a company called HomeBiogas is making a system it says can work in apartment buildings, and will be plumbed into the garbage disposal chute in the sink.
It's also launching a system aimed at restaurants and army bases, and has been supplying refugee camps with systems to help manage food and toilet waste.
Founded by a trio of marine biologists, that company says it's distributed over 15,000 systems so far, which offset more than 76,000 tonnes of CO2 emissions globally in 2021.
Mr Efrati expects those figures to ramp up significantly in the coming years as bigger products come online.
"Each commercial system can reduce greenhouse gas emissions by up to 1,000 tonnes of CO2-equivalent a year, compared to six tonnes a year for the household systems."
He says producing biogas at the source is part of a global movement to reframe "waste" as a resource.
"Countries across the world are starting to understand this and have implemented regulations forbidding sending waste to landfills," he says.
"We do not have any other options as landfills are filling up and their methane emissions are particularly damaging to the environment."
The UN and the International Energy Agency agree.
They've estimated biogas could supply up to 20 per cent of our gas demand as we transition away from fossil fuels.
Ned says it's a no-brainer.
"The fact that it can take all food waste and process it on site … on a community level as well as global, if people were not putting food waste into landfill, that would be huge."
