Reality Check

PA

There are lots of uses for CO2 in the process of getting beer to your glass, but not all beers need it.

As a general rule, lagers are more likely to use CO2 than ales. If you’re wondering whether your ale uses CO2, if you're in the pub and your pint is being poured just by flicking a switch on a tap then it will be coming from a pressurised keg and will be propelled to your glass either by CO2 or by a mix of CO2 and nitrogen. If there's a pump that the bar staff need to pull, then the beer will be coming from a cask and will be mostly propelled by the pump.

A keg will use CO2 to keep it under pressure while a cask will not.

Similarly, brewers use CO2 to move beer around their plants and to keep oxygen out of the tanks and pipes being used.

CO2 is produced by yeast in the brewing process and may be either recovered or lost, so some brewers will buy in the gas to pump into the beer and make it fizzy.

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Some of the English cities under pressure from Westminster to introduce clean air zones by 2020 launched consultations about their plans last week.

Birmingham, Leeds, Southampton, Nottingham and Derby have to reduce nitrogen dioxide levels or face big fines.

Of those, only Birmingham seems likely to introduce a scheme affecting all older vehicles, with the others expected to target heavier vehicles such as lorries, buses and taxis.

Schemes charging drivers more to use older vehicles in certain areas have been used around Europe - have they worked?

Morrisons

Morrisons' switch from plastic bags to paper got us looking round at the discussions online about the comparative environmental impacts of paper bags and plastic bags, with much of the research funded by plastic bag makers.

The figures are disputed, but it does appear that producing paper bags uses more energy, creates more carbon emissions and there is no question that paper bags are bulkier and heavier than plastic bags, thus take more energy to transport and more space in bins.

But new forests grown to replace trees cut to make paper bags will help in the battle against climate change by locking up carbon from the atmosphere.

Which you prefer depends on what your environmental priorities are, and at the moment the big issue is plastic. Yet all of these factors are being trumped by the fact that paper decomposes quickly into natural products, while plastic could potentially stay around for hundreds of years and breaks down into tiny particles that can get into the food chain.

Environmental groups say that what's needed in the longer term is a move away from single-use bags altogether.