I apologise for arguing with what should have been the final word, but this is a matter which must cause consternation to many ordinary people with a few birds and one which arises quite often in my professional role as lecturer in environmental health and food safety and security. It would be interesting to see the original email to Jhub. The links quoted are quite clear and do not contradict earlier comments on what is legal. The key words are “waste” and “discard”.
Where there is no intention at any time to discard materials, then they cannot and are not to be classed as 'waste'. This reasoning was relied on heavily by the High Court in the case of Mayer Parry Recycling Limited v The Environment Agency. The same point was made in the case of Environment Agency v Thorn International and Environment Agency v Inglenorth.
In the case of food-based waste the question is whether the material is to be discarded by the producer. Is it of no use within your own household? If the restaurant is disposing of the material it is waste. If your neighbour is disposing of the material it is waste. You, however, are not disposing of the material. You are deliberately using it for an intended purpose within your own premises having legitimately purchased it with the aim of so using.
The everyday use of language is confusing as “waste food” and “food waste” are terms used indiscriminately, however, it is worth considering that we throw away 7.2 million tonnes of food and drink from our homes every year, costing us £12bn - most of this could have been eaten.