Читать книгу Encyclopedia of Renewable Energy - James Speight G., James G. Speight - Страница 182

Third-generation biofuels (also called advanced biofuels) seek to improve the feedstock, rather than improving the fuel-making process.

Designing oilier crops, for example, could greatly boost yield. Scientists have designed poplar trees with lower lignin content to make them easier to process. Researchers have already mapped the genomes of sorghum and corn, which may allow genetic agronomists to tweak the genes controlling oil production.

Algae fuel, also called oilgae or third-generation biofuel, is a biofuel from algae, which are low-input, high-yield feedstocks that can produce biofuels. Algae can produce up to 30 times more energy per acre than land crops such as soybeans. With the higher prices of fossil fuels, there is much interest in algaculture (farming algae).

One advantage of many biofuels over most other fuel types is that they are biodegradable, and so relatively harmless to the environment if spilled. Algae fuel still has its difficulties though, for instance, to produce algae fuels, it must be mixed uniformly, which, if done by agitation, could affect biomass growth. Algae, such as Botryococcus braunii and Chlorella vulgaris, are relatively easy to grow, but the algal oil is difficult to extract. Macroalgae (seaweed) also have a great potential for bioethanol and biogas production.

Recently, the term fourth-generation biofuels has arisen and is coming into popular use. Fourth-generation technology combines genetically optimized feedstocks, which are designed to capture large amounts of carbon, with genomically-synthesized microbes, which are made to efficiently make fuels. The key to the process is the capture and sequester of carbon dioxide, a process that renders fourth-generation biofuels a carbon negative source of fuel. However, the weak link is carbon capture and sequestration technology, which continues to challenge industry.

See also: Biofuels – First Generation, Biofuels – Second Generation