What is bioenergy

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Bioenergy > What is bioenergy?

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Introduction to Bioenergy

Bioenergy is energy contained in living or recently living biological organisms, a definition which specifically excludes fossil fuels. Plants get bioenergy through photosynthesis, and animals get it by consuming plants. Organic material containing bioenergy is known as biomass. Humans can use this biomass in many different ways, through something as simple as burning wood for heat, or as complex as genetically modifying bacteria to create cellulosic ethanol. Since almost all bioenergy can be traced back to energy from sunlight, bioenergy has the major advantage of being a renewable energy source. However, it is important that bioenergy be harnessed in a sustainable fashion.

A specific plant or substance used for bioenergy is called a feedstock. Feedstocks are usually converted into a more easily usable form, usually a liquid fuel.


Types of biofuels

Liquid biofuels

Liquid biofuels have attracted much attention and investment because they can be used to replace or supplement traditional petroleum-based transportation fuels and can be used in existing vehicles with little or no modification to engines and fueling systems. They can also be used for heating and electricity production. Large quantities of liquid biofuels are presently used in many countries, and the potential exists to greatly expand their use in the future. The two most common kinds of liquid biofuels are ethanol and biodiesel, but a range of other liquid fuels exist or are being developed.


Ethanol is currently produced in large quantities by fermenting the sugar or starch portions of agricultural raw materials. The feedstocks used for ethanol production vary by region, including sugar cane in Brazil, grain and corn (maize) in North America, grain and sugar beets in France, etc. The top three ethanol producers are Brazil, the US and China. Because ethanol from sugar and starch directly competes with food production, people are working to commercialize technologies to produce ethanol from cellulose, which makes up the bulk of all plants and trees and is inedible. Cellulosic ethanol is often referred to as a second-generation biofuel.


Biodiesel is typically composed of methyl (or ethyl) esters of long chain fatty acids derived from plant oils. It is produced by chemically upgrading oils obtained from the pressing of oil plants, both edible like rapeseed, soybean and the fruits of oil palms and non-edible, like jatropha and karanj. Waste cooking oil can also be converted to biodiesel. (source:IEA Bioenergy)

Biofuel Yields of Selected Ethanol and Biodiesel Feedstocks. Image copyright by Worldwatch Institute. Excerpted from Biofuels for Transportation (2006, Worldwatch Institute). Used with permission.

Other Liquid Biofuels

Jatropha Nursery in Kaffrine, Senegal
  • Biokerosene
    • Kerosene is widely used to power jet engines. At present biokerosene is not produced for large-scale aviation because aviation fuels need to meet special requirements such as a very low freezing point and a high energy content by volume. There are, however, a variety of possible alternatives to petroleum-derived kerosene. The most promising is the synthetic biokerosene produced from Fischer-Tropsch processesusing biomass feedstocks.
  • Pyrolysis oil
    • also known as "bio-oil", is a liquid biofuel created through pyrolysis.
  • Biomass-to-liquids (BTL) - chemical processes that transform biomass into liquid fuels.

Gas biofuels


The most common kind of gaseous biofuel is biogasor biomethane, which is composed mostly of methane and carbon dioxide and is produced from the anaerobic digestion or fermentation of biomass including manure, sewage sludge, municipal solid waste, biodegradable waste or any other feedstock. Biogas can either be burned to produce heat and electricity or purified to be used as a vehicle fuel, sometimes mixed with natural gas.


Synthetic natural gas (SNG)

SNG is generated by gasification or fermentation of biomass and additional methanation and cleaning


Solid biofuels

Solid biofuels include wood, manure or charcoal burned as fuel as well as more recent innovations like high-density clean burning pellets. Solid biomass can be burned for heat or to produce electricity either by itself or as part of a co-firing power plant.


Wood can be utilized for bioenergy in the following forms:


Biomass pellets

  • Wood and other forms of biomass can be pressed into pellets. Due to their low moisture content, regular shape and high density, pellets can be burned very efficiently and are relatively easy to transport. They are often used for heating or electricity generation.

Sustainability concerns

Northeastern U.S. pine forest. Selectively harvested biomass from forests can be transformed into different forms of bioenergy.
  • Results of the ongoing German “bio global” project of Oeko-Institut and IFEU (sponsored by the German Ministry for Environment and the Federal Environment Agency) on sustainability issues of bioenergy trade

Special note

  • Please note: The term "bioenergy" has also been used to refer to various, especially medical or spiritual, concepts which are not the focus of this website.

Types of bioenergy edit

Gases: Biopropane | Biogas | Synthetic natural gas | Syngas
Liquids: Biodiesel | Biobutanol | Biogasoline | Biokerosene | Biomass-to-Liquids (BTL) | Dimethyl ether (DME)
ETBE | Ethanol | Methanol | Pure plant oil (PPO) | Pyrolysis oil | Synthetic Natural Gas
Solids: Biomass pellets | Char/Charcoal | Wood

Bioenergy conversion technologies edit
Technologies categorized by bioenergy processes:

Biochemical: Aerobic, Anaerobic, Landfill gas collection (LFG), Biodiesel production, Ethanol production
Thermochemical: Combustion, Gasification, Pyrolysis, Depolymerization

Technologies categorized by feedstock:
Algae | Cellulosic technology

Technologies by commercialization status:

Analysis of technologies: Life-cycle analysis


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