Sustainability of Biofuels
Harvests can rise only if new land is brought into cultivation or yields go up. In the longer run, plenty of new farmland could be ploughed up and technology would have advanced. But much of the new land is in remote parts of Brazil, Russia, Kazakhstan, the Congo and Sudan. Which would require big investments in roads and other infrastructure, which could take decades and would often lead to the clearing of precious forest. With technological advances, genetically modified foods would be brought into production or if new seed varieties would be planted in Africa. But again, that will take time. Moreover, GM foods will not live up to their promises unless they shed the popular suspicion that dogs them, especially in Europe. And some of the new land dry, marginal areas of Africa, Brazil and Kazakhstan could be vulnerable to damage from global warming. By some measures, global warming could cut world farm output by as much as one-sixth by 2020. No less worryingly, high oil prices would depress the use of oil-based fertilizers, which have been behind much of the increase in farm production during the past half-century.
Sustainability of Ethanol Production
Ethanol fuel production consumes large quantities of unsustainable petroleum and natural gas. Even with the most optimistic energy return on investment claims, in order to use 100% solar energy to grow corn and produce ethanol such as fueling farm and transportation machinery with ethanol, distilling with heat from burning crop residues, using no fossil fuels. The consumption of ethanol fuel to replace current U.S. petroleum use alone would require about 75% of all cultivated land on the face of the Earth, with no ethanol available for other countries, or sufficient food and water for humans and animals. Scientists at the Paris Global Science Forum Conference on Scientific Challenges for Energy Research believe that many biofuels are therefore non-scalable non-solutions to our current worldwide energy crisis.