Although China’s economic growth is slowing, the country still has a voracious appetite for electricity. According to the China Electricity Council, the nation is expected to generate 1,050 gigawatts of power this year, an almost 9 percent increase from last year. But even that additional growth won’t accommodate the nation’s energy demand.

China’s enormous demand for electricity is primarily fed by coal, which generates about 83 percent of the nation’s power. Although China holds the world’s third-largest coal reserves, its massive demand makes it a net importer of coal. Indeed, China ultimately consumed 300 million more tons of coal than the 3 billion tons it produced last year.

However, growth in coal demand isn’t just a Chinese story. Coal’s abundance and relative low cost make it the fuel of choice throughout the emerging markets. As such, coal demand is expected to grow by more than 78 percent over the next two decades.

The emerging markets aren’t the only coal-dependent nations. The developed world also heavily relies on coal for its power generation. More than 44 percent of US electricity is generated by coal-fired power plants, while Canada uses coal in similar quantities.

Additionally, Japan’s damaged nuclear infrastructure should cause it to become more dependent on coal and natural gas to meet its energy demand over the next two years. The nuclear crisis in Japan has also inspired governments in other countries to reduce their use of nuclear power. For example, the German government’s plan to phase out its existing nuclear reactor could also lead to a spike in that nation’s coal demand.

Although some investors may view coal as an antiquated power source, coal demand should remain robust for the foreseeable future. In fact, the US Energy Information Agency predicts that annual global coal demand will swell from its current level of 150 quadrillion British thermal units (BTU) to more than 209 quadrillion BTUs by 2035.

These are long-term trends that can’t be ignored.

Market Vectors Coal ETF (NYSE: KOL) offers investors the best way to gain exposure to the global coal markets. The exchange-traded fund (ETF) holds shares of 36 companies engaged in some aspect of the coal business.

More than 68 percent of assets are allocated to shares of coal mining and production companies, with the remainder spread across mining equipment makers, power generators and the technology companies that cater to the coal business.

The ETF allocates 40.9 percent of its assets to the US, but the fund is also well diversified geographically, with nine nations represented in its portfolio. Most significantly, the ETF has a 20.6 percent allocation to China and a 14.6 percent allocation to Australia, which represent one of the most important coal trading relationships in the world.

The ETF charges a reasonable expense ratio of 0.59 percent, which makes the fund an inexpensive long-term holding.

With coal demand forecast to rise for decades to come, coal will produce gains for long-term investors.