Although there are some reasonable questions about the value of making long-term projections about energy use, doing so is one of the duties of the US' Energy Information Agency. On Monday, the EIA released an overview of a report in which it attempts to track the trends in the energy economy of the US out to 2040. The report contains some eye-popping predictions, including a huge (but brief) boom in domestic oil production, a near balance between energy imports and exports, and a peak in carbon emissions that's already in our past.

Energy predictions are fraught with uncertainty, but this report contains more than most, since it's predicated on having the entire period out to 2040 covered by legislation and rules that are already on the books. At the moment, that would include the expiration of a tax credit that promotes the installation of renewable power facilities, something that Congress has already renewed several times. Perhaps more significantly, the EPA's rules governing greenhouse gas emissions from existing facilities are still being formulated but are likely to be in effect for most of the period under consideration.

This probably explains why the EIA predicts that the slice of domestic energy production that comes from renewables only increases from 11 to 12 percent over the next 30 years.

But what's startling is that, despite the slow rise in renewables, the EIA thinks that the US is already past its peak of carbon emissions (2005 and 2007 both had roughly similar totals and represent the peak). As shown in the chart below, the energy used for each dollar of GDP has been dropping steadily since the 1980s; carbon emissions for each dollar have recently started dropping even faster. The report projects that those trends will both continue, with energy/dollar dropping by a total of 43 percent by 2040.

In addition to the growth of natural gas and rise of renewables, the report ascribes this drop to an increase in efficiency (vehicle fuel efficiency in particular is improving significantly). This won't result in a big drop in carbon emissions—continued GDP growth will offset these tends—but it could mean a prolonged plateau out to 2040. And, as noted above, policy changes may actually help drive a drop, and any climate agreements are likely to require one.

The other thing driving the drop in carbon intensity is the natural gas boom. It's made natural gas the cheapest way to generate electricity in the US (ahead of well-sited wind), a change that the report predicts will see gas become the largest source of electrical power in the US by 2030, displacing coal. Given that burning coal releases far more CO 2 per unit of energy, any emissions rules could accelerate this changeover as well.

There's a technique similar to fracking that works for oil, and that's setting off an equivalent boom. The EIA expects that oil production within the US will reach levels not seen since the peak in 1970. But oil flows through rocks less easily than natural gas, so the boom will be short lived, peaking before this decade is over. In contrast, the growth of natural gas extraction won't peak at all in the report's timeframe, leading to 50 percent growth between now and 2040.

The net result is that the gap between net energy production and consumption, currently at 16 percent, will drop to under five percent in the 2020s and stay there. We'll still import lots of oil, but exports of coal and natural gas will offset most of that.

The surge in natural gas supply will have impacts beyond turning the US into a net exporter of the fuel. It can be used as a raw material in many chemical processes, and the cheap power it generates can make various industrial activities more economical. As a result, the EIA foresees a growth in domestic chemical and metal production, as well as other forms of manufacturing. This won't be large for any one sector, but the overall growth will be fairly significant.

The other place that's likely to see growth is the use of natural gas in transportation. The EIA thinks that the price of natural gas will go up, but that the price of oil will go up even faster, increasing an already substantial gap between the two. By 2040, the report suggests that up to three percent of the transportation fuel will be in the form of compressed or liquid natural gas, mostly used by buses and long-haul freight. It's even possible that it will find a use in rail and cargo ships.

So, while the report is limited by its mandate to stick within the confines of existing regulations, the most likely results of any regulatory changes are to enhance the impact of underlying trends in efficiency and energy extraction. In other words, unless governmental policies change radically, we're likely to get to some of these places sooner than 2040.