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A bug's life - How industrious insects are recycling food waste for farmers

PUBLISHED: 10:03 01 June 2019 | UPDATED: 11:04 01 June 2019

Soldier fly larvae are being used to turn rotting fruit waste into a valuable farming by-product. Picture: AMT Fruit

Soldier fly larvae are being used to turn rotting fruit waste into a valuable farming by-product. Picture: AMT Fruit

AMT Fruit

Two Fenland firms have found an inventive solution to food waste by recycling rotting fruit back into farmland as a non-toxic bug repellent - with the help of some industrious insects.

Larvae of the black soldier fly. Picture: MD-Terraristik/WikimediaLarvae of the black soldier fly. Picture: MD-Terraristik/Wikimedia

Waste fruit crops are being fed to insect larvae to generate a valuable by-product for farmers - and it is all thanks to a mutually-beneficial partnership within East Anglia's "circular economy".

Food waste has become a growing consumer concern, with a recent study by campaign group Feedback estimating that as many as four million UK people could be fed their "five a day" from fruit and vegetables that are currently rejected for cosmetic reasons such as colour, shape and size.

One company which has found novel ways to address this problem is AMT Fruit, part of the Munoz Group, based in Chatteris near Ely - one of the UK's largest citrus specialists, working with over 250 growers to supply Tesco with about 140 million nets of fruit each year.

Between 2015 and 2018, the firm says it has reduced its operational waste by 30pc by broadening retail product specifications, introducing new "over-sized" product lines, improving delivery strategies to extend shelf life, and donating one million portions of fruit via food charities.

Black Soldier Fly (Hermetia illucens). Picture: James Niland/WikimediaBlack Soldier Fly (Hermetia illucens). Picture: James Niland/Wikimedia

But despite these efforts the organisation still generates more than 2,000 tonnes of waste each year from its UK operation - prompting an inventive partnership with a fellow Fenland firm.

AgriGrub, based in nearby Soham, feeds the waste vegetables and fruit to the ravenous larvae of black soldier flies which are branded as Calci worms and sold as a form of live pet food for reptiles.

Their by-product is called frass - a sustainable source of plant nutrients, and a bio-repellent for crop protection.

Naomi Pendleton, head of technical at AMT Fruit, said: "Our citrus waste is too wet and acidic and full of rots and moulds which makes it unpalatable for animal feed. We were having to send all our waste to AD [anaerobic digestion] plants. At the start of 2018 we were introduced to Joe Halstead from AgriGrub, who was looking for locally sourced viable waste products on which to grow his black soldier fly larvae."

Naomi Pendleton, head of technical at AMT Fruit. Picture: AMT FruitNaomi Pendleton, head of technical at AMT Fruit. Picture: AMT Fruit

"This is a great example of a circular economy created through a mutually beneficial relationship."

Joe Halstead, managing director of Agrigrub, said the active component in frass is called chitosan, which is already well-documented as an efficient biopesticide - but for many years the cost of extracting it was considered too great, as the process involved boiling crustacean shells in sulphuric acid.

Frass from insects, however, needs little processing and represents an economically viable source of chitosan for agriculture, he said.

"We are focusing our attention at the moment on higher margin crops which have few treatment options for pests and diseases as this is likely to give us the best return in the least time," said Mr Halstead.

Joe Halstead, managing director of AgrigrubJoe Halstead, managing director of Agrigrub

"However, longer-term I hope and expect frass to have broad-acre application, especially where neonicotinoids [pesticides now banned by the EU] are being phased out. Our first frass trials, on brassicas, showed a 94pc reduction in aphid numbers on frass-treated plants versus controls.

"It is in the field where routine synthetic pesticide usage is most damaging to our environment, so ideally we'd like to see frass and its bio-repellent qualities used in the field to repel insects rather than killing them. This spares non-pest species and allows beneficial insects to persist in the local environment."

Naomi Pendleton will discuss the project at an Agri-Tech East event in Norwich next week, named Closing the Loop on the Circular Economy.

Dr Belinda Clarke, director of Agri-Tech East, said: "Food waste is a major issue and the work AMT Fruit is doing with AgriGrub is one of a number of inspirational approaches that use waste from one process as input to another. The event will also look at novel uses for coffee waste and ways of producing fertiliser from greenhouse gas."

Other speakers at the event include Gareth Roberts of Cambond, Peter Hammond of CCm Technologies, Steve Taylor of Celbius and Dr Claudio Avignone Rossa, reader in systems microbiology at the University of Surrey. It will be chaired by Meredith Lloyd Evans, chief executive of BioBridge.

- The event "Closing the Loop on the Circular Economy" takes place on Wednesday June 5 from 1.30pm to 5pm at Centrum on the Norwich Research Park. For more information see the Agri-Tech east website.

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