A recent study by the US National Academies into coal's research and development needs found that future levels of coal use will depend largely on the timing and stringency of regulations to control carbon emissions. By around 2020, coal use in the US could lie somewhere between 25% above 2004 levels and 15% below them. And 10 years later, coal consumption is even more unclear – ranging from 70% above current levels to 50% below.

In the words of Corale Brierley, president of Brierley Consultancy and chair of the committee that wrote the report, "given the degree of uncertainty about future coal use, R&D policies need to accommodate a range of possible scenarios".

With that in mind, the committee suggests additional funding of around $10 m a year to determine the size and characteristics of recoverable coal deposits in the US. As mines become deeper or use coal seams in areas that have already been mined, the risk to mine workers will increase. So the report recommends investing around $35 m a year in research that will decrease miners' exposure to dangerous conditions. This should include efforts to control methane release, which would have the added benefit of reducing emissions of a greenhouse gas and potentially adding to natural gas supplies.

Of course, it's not only safety that's affected as mines go deeper – there will be effects on the environment too. That's why the committee proposes $60 m a year for research into lessening the environmental impacts of coal mining, such as mitigating disturbance of groundwater and surface water systems, minimizing the risk of ground collapse, and reducing the effects of acid mine drainage from abandoned mines.

The study also recommends an assessment of the suitability of geological formations, such as depleted oil and gas fields, for storing carbon dioxide. Such an assessment could include the formations' storage capacity, rates of migration and leakage of the gas, and the economic, legal and environmental impacts of storage in both the near- and long-term.

"If coal is to continue as a primary component of the nation's future energy supply in a carbon-constrained world, large-scale demonstrations of carbon management technologies – especially carbon capture and sequestration – are needed to prove the commercial readiness of technologies to significantly reduce carbon dioxide emissions from coal-based power plants and other energy conversion processes," says the report.

The committee believes that decisions on whether to invest in new coal-based power plants are likely to depend on both future constraints on carbon dioxide emissions and on the commercial readiness of carbon emission reduction technologies.

At the recent G8 summit in Germany, the US agreed – along with Germany, France, the UK, Italy, Japan, Canada, Russia and the European Union – to aim to at least halve global carbon dioxide emissions by 2050 under a UN framework. Since the agreement was not legally binding, however, the future of carbon dioxide emissions constraints in the US – and so the outlook for additional US coal-based power plants – is as yet unclear.