AS I walked home the other day I noted the neat cylinders of black plastic bags on every doorstep.

Can someone explain to me why it is suddenly more eco-friendly – more green – to use thousands upon thousands of plastic bags for our refuse, when until now one wheelie bin, which would have lasted for ever, would have been used week-in, week-out?

Are the council’s black bags biodegradable? If not, where do they all go? Are they washed out and reused? No? Please explain, someone.

Brian Roberts, Stamford Street East, York.

• A City of York Council spokeswoman, said: “Black bags have been a feature of waste collections for many years and they will continue to have a place in the future.

“Many properties are unable to use wheeled bins due to constraints on space for storage, presentation or the fact that we simply can’t get a vehicle to empty them.

“Our bags are not biodegradable. Biodegradable sacks require oxygen in order to decompose, and sacks made of this material are aimed more at reducing litter, as the bags will decompose in the open air over a period of a few months.

“Putting biodegradable sacks into landfill prevents them from decomposing as there is no oxygen underground.

“That said, it is waste decomposing in the ground that causes harmful greenhouse gases and, as bags take many, many years to decompose, they produce much less of these gases.

“It is organic waste that decomposes quickly underground that produce huge amounts of greenhouse gases.

“Our bags are made from recycled material.”