Picture: Helge V. Keitel, KK-Net, Sotkamo, Finland (2011)
The US Department of Energy predicted 2011 that the use of foreign petroleum, which currently feeds 56% of the demand, will grow to 68% by 2025. The economic consequences of this are self-evident, but recent geopolitical events and growing environmental concerns related to the global build-up of greenhouse gases have also become energy-related issues.
Consequently, a serious interest in alternative energy sources is now being fostered for reducing dependence on non-renewable foreign energy sources. One such measure is the conversion of under-utilized lignocellulosic biomass sources, such as corn stover, bagasse, pulp and paper waste, switch grass and the like, into liquid fuels and chemicals that partially replace petroleum and petrochemicals.
To date in the US, production of renewable fuels, particularly ethanol, is primarily from food crops that are high in sugar and starch. Even given the economic viability of corn ethanol, government subsidies are still required.
While this has had some impact on US energy source portfolio, its application has not been without several serious limitations. The use of arable land for fuel rather than for food production and the use of food sources for fuel rather than as food have created issues in prices and availability of traditional food and feed.
A more sustainable solution would be the use of cellulosic feedstock, which often can be obtained as waste from food crops or from non-food plants grown on marginal land.
In US, the Federal Government has been calling for search into ethanol production from a number of cellulosic sources.
The most widely investigated of these sources thus far have been corn stover or crops grown specifically as energy crops, such as switch grass and poplars. However, another viable feedstock could be aquatic plants obtained from constructed wetlands.
Source: Journal of Industrial Microbiology and Biotechnology