Sir, - Whilst I support much of Mr Stephen Kershaw's letter (D&S, Sept 12) I have a major concern.

His suggestion that a biodegradable refuse sack has environmental merit is flawed and misplaced as these products only have value in well controlled green waste composting systems which are closely monitored and well controlled.

The description "biodegradable" is usually misleading. What does it mean and how was the product tested - if indeed it has been and by whom?Are the results published and are they understandable by the general public?

Usually plastic sacks claiming to be biodegradable work well in laboratory conditions where temperature, moisture and availability of oxygen are well controlled. Unfortunately these conditions rarely exist in the United Kingdom and never in landfill sites - as this would lead to excessive generation of methane.

Further, I have yet to see a full environmental impact comparison of ordinary sacks with the biodegradable version. I suspect that the environmental footprint of the latter to be worse than the former which is why they are never published.

I accept that they will work in dedicated composting schemes where they exist but elsewhere biodegradable sacks offer no environmental benefit to society.

Lastly, I should point out that most of the harmful brands contain up to 75pc of recycled or recovered material - this is not possible with biodegradable material which cannot be recycled.

JOHN SALE

Mapleton Drive,

Norton.

Spare a thought

Sir, - ActionAid's nationwide fundraising collections will be taking place between September 20 and October 5, and like many volunteers across the country we will be visiting friends and neighbours during the fortnight beforehand to ask for donations.

In its fight against global poverty ActionAid will be drawing attention to the plight faced by many children living in poverty throughout the developing world.

All over the world, every single day, poverty, politics and conflict deny children their basic rights. These children are declined the freedom to have a childhood.

And that's why we are asking local readers to spare a thought for children and their families the world over and help ActionAid's work with some of the poorest communities in Africa, Asia, Latin America and the Caribbean so that they can have a brighter future.

BOB & LIZ SAMPSON

School Lane,

Newton-le-Willows,

Bedale.