Feeling squeezed from gas prices? Why not make your own?
The world throws away about a third of all food produced each year.
In Australia, that equates to more than 7 million tonnes of edible food, and is estimated to cost the economy more than $36 billion a year, according to a report commissioned by the federal government.
At the same time, many of us cook with gas, which is increasingly expensive and contributes to greenhouse gas pollution.
But there is a growing movement of people and businesses looking to kill two birds with one stone.
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Making biogas at home from leftover food, which can then be used for cooking, is getting simpler.
Several companies now offer large-scale systems for restaurants and even refugee camps, as well as basic home arrangements.
About six years ago, Annett and Paul left city life in Sydney and moved to northern New South Wales, where they built a small off-grid house.
As part of the arrangement, they installed a biogas food digester which they use to feed leftovers and toilet waste.
From that organic material, the system produces methane, which is piped through a duct to the gas stove in their home.
Annett says there are some days in the summer when the system is most productive, and they struggle to keep up with the amount of gas it produces, which they use to subsidize their solar-powered electric stoves.
“Good. We basically use it in the morning or at night when the sun isn’t out,” Annett said.
Making gas pay for itself
Emissions from food waste account for about 3 per cent of Australia’s total greenhouse gas emissions each year, according to data from the former federal government.
Worldwide, emissions are close to 8 percent.
While making 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 the 2019 Australian study.
In the case studies I looked at, it turned out to be a financially viable option as well.
The study found that enough gas is produced from one household to cook an average of nearly 38 minutes each day.
However, that includes some days where no gas is used, and others where a gas supply of up to two hours is used.
According to their data, a system will pay for itself in just four years based on savings from gas purchases alone.
And that was based on lower gas prices at the time.
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If savings from fertilizer, which is a by-product of making methane from food waste, are taken into account, the payback period will be even shorter.
Like Annett and Paul, Ned lives on an off-grid property near the Hawkesbury River in New South Wales and makes his own biogas.
The bladder in which gas is stored lasts about two and a half hours.
He said he realized the real use of making his own biogas when his family was recently flooded.
“[The delivery driver] can’t go in to deliver gas bottles,” he said.
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“The whole idea that you could always go to the store and get things… it wasn’t always like that.”
He says their system doesn’t produce enough gas to supply all of their cooking needs, but is excellent as a backup and for diverting waste away from landfills.
“We may not have as much leftovers [the average family].
“We are a family of five – three young children – the amount of gas cooking we do is probably more than we can generate from consuming home-cooked food waste.
Annett said it was a similar case with his family system.
At first, they left to the farmer’s market to get extra leftovers to feed, but now they only use gas as a backup.
“We don’t feed him as much as we can — you can feed him up to six liters [of food waste], per day but we only add about one to two.
“If you only use it to make coffee or tea, you can use it every day, but if you cook food on it … we have to keep an eye on it a bit.”
What if I live in an apartment?
There are other requirements for making biogas at home as well which means 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, all of them take up little space and may not be conducive to apartment living.
That’s because unlike liquefied natural gas that we get in gas bottles, for example, methane produced from food waste remains in the form of an expanding gas.
Ned is quite handy and is looking for a way to compress his homemade methane, but for others it won’t be an option.
Another problem is temperature.
Anaerobic digestion stops below about 20 degrees Celsius, and has an optimal digestive temperature of around 35C.
Although electric heating devices are one option for keeping production running in colder climates, Annett says their systems slow down significantly at this time of year.
So is there a solution for people without space or in colder climates?
Western Australia’s Cockburn City Council has run a trial in which they collect leftovers from partners including fish and chip shops and bakeries.
They then send the waste to a fertilizer factory where the methane is captured and used to drive a generator to generate electricity.
At its peak, they estimated the generators supplied electricity from biogas to about 3,000 homes.
And although Cockburn was just an experiment, the Byron Shire wanted to implement a similar program permanently.
Byron already has a system of three bins, with one dedicated to food waste owned by environmentally conscious communities, according to bioenergy project manager John Hart.
With the existing waste collection system, he hopes their biogas generator will be operational soon.
“We want to do the groundbreaking around February 2023 after the summer holidays and have the facility running a year later,” he said.
As well as being a less expensive alternative to landfill for businesses, Hart thinks with rising fuel and waste disposal costs, the savings could filter back to rate payers.
“The business case for this facility is that we keep it local. We will reduce truck movement and power the largest sewage treatment plant on the council with green electricity.
“It makes sense that housing rates would come down, which would be a huge success story for local housing rate payers.”
Waste treatment solutions for refugee camps
Internationally, a company called HomeBiogas is building the system said it could work in an apartment building, and would be dumped down the drain in the sink.
He has also launched systems aimed at restaurants and military bases, and has supplied refugee camps with systems to help manage food and toilet waste.
Founded by a trio of marine biologists, the company says it has distributed more than 15,000 systems so far, offsetting more than 76,000 tonnes of CO2 emissions globally by 2021.
Mr Efrati expects those numbers to increase significantly in the coming years as bigger products start coming online.
“Each commercial system can reduce greenhouse gas emissions by up to 1,000 tonnes of CO2 equivalent per year, compared to six tonnes per year for domestic systems.”
He said producing biogas at the source was part of a global movement to reframe “waste” as a resource.
“Countries around the world are starting to understand this and have implemented regulations that prohibit sending waste to landfills,” he said.
“We have no other choice because the landfills are full and the methane emissions are very damaging to the environment.”
The United Nations and the International Energy Agency agree.
They estimate that biogas can supply up to 20 percent of our gas demand when we switch from fossil fuels.
Ned said it was nothing to think about.
“The fact that it can take all the leftovers and process them on site … at the community level as well as globally, if people don’t throw food waste into landfills, it’s going to be huge.”
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