Second generation biofuels

Second generation biofuel technologies are able to manufacture biofuels from biomass. Biomass is a wide-ranging term meaning any source of organic carbon that is renewed rapidly as part of the carbon cycle. Biomass is all derived from plant materials but can include animal materials.

Second generation biofuel technologies have been developed because first generation biofuel manufacture has important limitations. First generation biofuel processes are useful, but limited: there is a threshold above which they cannot produce enough biofuel without threatening food supplies and biodiversity. They are not cost competitive with existing fossil fuels such as oil, and some of them produce only limited greenhouse gas emissions savings.

Second generation biofuels can solve these problems and can supply a larger proportion of our fuel supply sustainably, affordably, and with greater environmental benefits.

Second generation bioethanol production: Lignocellulosic bioethanol
First generation bioethanol is produced by fermenting plant-derived sugars to ethanol, using a similar process to that used in beer and wine-making. This requires the use of 'food' crops such as sugar cane, corn, wheat, and sugar beet. These crops are required for food, so if too much biofuel is made from them, food prices could rise and shortages might be experienced in some countries. Corn, wheat and sugar beet also require high agricultural inputs in the form of fertilizers, which limit the greenhouse gas reductions that can be achieved. Therefore, next generation processes are required to extend the amount of biofuel that can be produced sustainably.

All plants contain cellulose and lignin. These are complex carbohydrates (molecules based on sugar). Lignocellulosic ethanol is made by freeing the sugar molecules from cellulose using enzymes. These sugars can then be fermented to produce ethanol in a similar way to first generation bioethanol production.

The by-product of this process is lignin. Lignin can be burned as a carbon neutral fuel to produce heat and power for the processing plant and possibly for surrounding homes and businesses.

The greenhouse gas emissions savings for lignocellulosic ethanol are greater than those obtained by first generaiton biofuels. Lignocellulosic ethanol can reduce greenhouse gas emissions by around 90% when compared with fossil petroleum Concawe Well to Wheels LCA.

An operating lignocellulosic ethanol production plant is located in Canada, run by IOGEN Corporation IOGEN. The demonstration-scale plant produces around 700,000 litres of bioethanol each year. A commercial plant is under construction. Many further lignocellulosic ethanol plants have been proposed in North America and around the world. For further information on this topic, see the cellulosic ethanol entry.