Rising energy demand over the coming two decades will require investment in all potential sources of energy, Exxon Mobil said Tuesday in its latest report.

The report, "New Outlook for Energy: A View to 2030," predicted energy demand would be about 35 percent higher in 2030 than it was in 2005, and meeting that demand will require "trillions of dollars of investment and a commitment to innovation."

Exxon Mobil said it expects economies worldwide to grow and living standards to improve -- implying increased use of automobiles and energy-dependent appliances.

As with other recent forecasts, Exxon Mobil said natural gas supply is set to expand, particularly in the United States. Unconventional gas supplies in the United States are expected to meet more than 50 percent of gas demand by 2030.

Analysts said rising energy demand and consumption would pose a major challenge as the clamor grows for cleaner and more renewable energy sources.

Although high prices, political commitments and campaigning groups have all pushed initiatives toward energy sources with a lower carbon footprint, achieving substantial results is set to be a major challenge through the next decades covered by Exxon Mobil's outlook.

Fossil fuels -- oil, natural gas and coal -- are set to continue meeting most of the world's needs in the near future "because no other energy source can match their availability, versatility, affordability and scale," the report said.

"The fastest-growing of these fuels will be natural gas, reflecting its abundance, versatility and economic advantages as an efficient, clean-burning fuel for power generation."

The oil company was upbeat about the future. "We see many hopeful things -- economic recovery and growth, improved living standard and a reduction in poverty, and promising new energy technologies," said Exxon Mobil's Rex W. Tillerson, chairman and chief executive officer.

"But we also see a tremendous challenge, and that is how to meet the world's growing energy needs while also reducing the impact of energy use on the environment," Tillerson added.

Tillerson said supplies of all economic fuel sources need to be expanded to satisfy projected increases in global energy demand. With world population set to rise to almost 8 billion, there will also be greater demand for energy indirectly applied to serve the broader societies.

Exxon Mobil's outlook includes an assessment of how potential carbon emission reduction policies will affect future energy demand and impact the fuel mix. The company says that imposing higher costs for carbon emissions would affect energy prices and prove to be an incentive to switch to less carbon-intensive fuels, such as natural gas.

Exxon Mobil said energy-efficiency gains are expected to accelerate between 2005 and 2030 when contrasted with historical trends. Gains in energy efficiency will curb energy demand growth through 2030 by about 65 percent, it said.