PERSONAL Carbon Allowances have been a talking point this week after receiving broad support from a UK environmental audit committee report released on Monday. The idea is that the government would give each individual across the country an equal number of carbon credits to spend each year, creating a market in which those who lead a lower-carbon lifestyle can sell their unused credits via an exchange to those who exceed their limit. The credits would be used alongside money payments to account for the carbon inherent and explicit in our consumer and behaviour choices. This approach to individuals taking personal responsibility for reducing the emissions, widely believed to be causing global climate change, has been discussed by groups across the world since at least the beginning of this century, but it is only now becoming a political hot topic here in the United Kingdom.

Some supporters view Personal Carbon Allowances (PCAs) as a complement to "green taxes". Others view them as a fairer and more equitable alternative, allocating responsibility for change through a mechanism that would be clearer to the public than complex or "stealth" taxes. Already some who question this system are making comparisons to Second World War ration coupons. But how would it work and what does it cover? Mayer Hillman's highly readable How We Can Save the Planet set out a workable model in 2004. The chapter "Watching Your Figure: How to Live Within Your Carbon Ration" reads much like straightforward dieting guidance for a healthy lifestyle, except the "calories" being counted are kilograms of carbon dioxide that we use in our homes and our travel.

Hillman, and many others since, calculate that in the UK the average adult is responsible for some 5,420 kilograms of (kg) per year directly through the energy we use for our homes and how we travel, on a daily basis and on our holidays. To put that into perspective, you use 146kg on a return train journey from Edinburgh to London. A transatlantic flight will produce 3,930kg ? almost your whole year's allowance. And typically, a car driver in Britain emits 1,050kg every year. Surely industry puts out more , so why penalise the individual? Actually this annual personal number is only slightly larger than the proportion of generated by industry per capita supplying our infrastructure, services and goods, including our food. And the industrial side of the process can be more effectively motivated by commercial trading systems such as a maturing EU Emissions Trading Scheme.

In this way the producer, for instance a farmer producing strawberries or a manufacturer producing a sofa, is directly responsible for reducing their carbon, where they can, or must pay the cost. That cost will no doubt be embedded in the cost to the consumer, and the merchant may even prefer to reveal those costs, but it is their responsibility and opportunity to reduce their emissions. That said, it is also the consumer's choice to shop competitively, not only for the lowest price, as reflected in reduced impacts, but also for businesses who reflect shared values with the purchaser. This is where PCAs may become crucial and carbon calculators become useful tools. If we are each meant to reduce our by 80 per cent in line with the Scottish Government's proposals (in line with recommendations by the International Panel on Climate Change) then we need a plan to reduce each of our 5,400kg by something like the same.

A positive example of this model has been tested by Sustainability South West in England for over a year. Using a carefully calculated methodology (clearly set out on the project's website) the organisation has worked out a PCA for each year from 2007 to 17. Over this time individual budgets reduce incrementally by 30 per cent. This voluntary pilot is already well supported by individuals, businesses and community groups. While some of the supporting materials may be a bit basic, that is balanced by their clarity and the organisation's willingness to test the waters in what inevitably will be an evolving process. But how can individuals get over the pain of making an 80 per cent reduction? Some choices are fairly straightforward. Buying a more efficient A++ refrigerator is easy. But what about the cars and homes we have already invested in?

This debate came live this week as MPs argued that highly punitive car tax on less efficient cars punished consumers who had already made purchases. The introduction of PCAs would mean those who drive more miles in less-efficient cars would more quickly use up more of their annual credits than those with more efficient models or those who drove less or used public transport. The difficulty is, if everyone is in the same boat then resale of inefficient models will escalate their depreciation. So in taking this forward we will clearly need a phased approach, supported by industry and entrepreneurial options. Perhaps we need businesses that offer to buy our less-efficient cars on agreement that we commit to competitive leasing agreements for more-efficient models.

Or jobs that are more flexible via home working or video conferencing that make lower-impact demands on our mobility while improving our productivity through a lower percentage of our time spent on travel. And better, faster, more sophisticated public transport options will improve the way we travel in the 21st century. It seems highly likely that PCAs will become a tangible part of our lives in the coming years, but individuals will need some help from business and government to make it work.