Gen Z and millennials have become the biggest adopters of online grocery shopping and consumers of delivery takeaway, with Rabobank reporting "convenience culture" correlates with more food waste.

Households in the ACT reportedly throw out 12.3 per cent of the food they buy annually, meaning more than $1100 worth on average ends up in the bin.

The annual waste would feed 1.1 million households or all the households in Canberra 13 times over for an entire year, the report said.

The agribusiness bank found household spending on food increased nationally by about $20 per week in 2021, meaning the average weekly grocery bill was now $178.

Its annual national survey also showed bigger spenders tended to be bigger wasters, with Aussies who spent over $300 each week on food wasting almost 17 per cent of their grocery shop.

Rabobank Australia head of sustainable development Crawford Taylor said COVID-19 had changed food purchasing habits for the worse and results showed even with lockdown, bad habits remained.

Worryingly, Mr Taylor said the report was based on what people estimated they wasted, which meant the reality was likely to be much worse.

He said a high proportion of both high-income earners and students likely contributed to the capital's increased food wastage, despite student numbers having been reduced in the last 12 months.

"When you look at it via the generations, the Gen Z throw out 15.7 per cent relative to the baby boomers," he said.

"The baby boomers make up 5.9 per cent, so about 2.5 times less."

Mr Taylor said consumers were responsible for half of what was wasted through the food chain in Australia each year.

"Individuals do have the power to take action and have a positive impact on the amount of food thrown out across the country," he said.

"While also saving themselves hundreds of dollars and reducing the substantial impact food waste is having on the environment and carbon emissions."

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The report found using leftovers to make lunches for the week could save $364 annually and considering portion size when preparing meals could save up to $412 annually.

Globally, food waste produces 8 per cent of greenhouse gas emissions, according to Rabobank, with foods that end up in landfill decomposing and releasing carbon dioxide and methane.

Mr Taylor said the main reasons for wastage included food losing its freshness, food going off or people simply forgetting about it in the cupboard or fridge.

"This is perhaps why it's so surprising for a generation known for their concern for the environment, that Gen Z is the most likely to waste food while at the same time, being the generation most likely to believe that food waste impacts climate change and pollution," he said.

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