Renewable fuels

Renewable fuels have gained in popularity due to their sustainability, low contributions to the carbon cycle, and in some cases lower amounts of greenhouse gases.

The geo-political ramifications of these fuels are also of interest, particularly to industrialized economies which desire independence from Middle Eastern oil.

Biofuels from grain and beet in temperate regions have a part to play, but they are relatively expensive and their energy efficiency and CO2 savings benefits, are variable.

Of the worldwide total remaining petroleum reserves of approximately 1,277,702,000,000 barrels (203.1384 km3) (about one half of the original virgin reserves) and a worldwide usage rate of 25,000,000,000 barrels (4.0 km3) per year, only about 50 years worth of petroleum is predicted to remain at the current depletion rate.

If the modern world remains reliant on petroleum as a source of energy, the price of crude oil could increase markedly, destabilizing economies worldwide.

Furthermore, the conclusion that anthropogenic greenhouse gas emissions are causing climate change, along with regional geopolitical instabilities have challenged nations to act to develop both alternative and carbon-neutral sources of energy.

On December 19, 2007, President Bush signed into law the Energy Independence and Security Act, establishing a requirement that at least 36 billion US gallons (140,000,000 m3) of renewable fuel be used in the marketplace by 2022.

Dedicated energy crops, such as switchgrass, are also promising cellulose sources that can be produced in many regions of the United States.

Cellulosic biomass, derived from non-food sources such as trees and grasses, is also being developed as a feedstock for ethanol production.

[9] According to the International Energy Agency, biofuels have the potential to meet more than a quarter of world demand for transportation fuels by 2050.

By rapidly heating biomass in the absence of oxygen (pyrolysis), a liquid crude can be formed that can be further processed into a usable bio-oil.

As opposed to other biofuels, pyrolysis oils use the non-edible fraction of biomass and can occur on the order of milliseconds and without the need for large fermentation reactors.

When this process draws its power from renewable energy sources like wind turbines or photovoltaic cells, the production requires little consumption of non-renewable resources.