What is bioenergy
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Bioenergy > What is bioenergy?
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.
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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.
Bioethanol
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
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)
Other Liquid Biofuels
- Biobutanol (butanol, butyl alcohol)
- Butanol (called "biobutanol" if derived from biomass) is an alcohol similar to ethanol but with a higher energy density. Despite this and other advantages butanol is currently more expensive to produce than ethanol.
- Pure Plant Oil (PPO)
- PPO (also known as SVO, Straight Vegetable Oil) is a diesel type fuel. It occurs natural in plant oils such as rapeseed, jatropha and many others. Waste cooking oil can also be converted to PPO. PPO can be used in its pure form or mixed with diesel/biodiesel.
- 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.
- Biogasoline
- Under development by Shell and Virent Energy Systems, biogasoline is a synthetic form of gasoline made from cellulosic feedstocks.
Gas biofuels
Biogas
The most common kind of gaseous biofuel is biogas, 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 electricity or mixed with natural gas (in either a gas or compressed liquid form) and used as a vehicle fuel.
Biopropane
Synthetic natural gas (SNG)
Syngas
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
Wood can be utilized for bioenergy in the following forms:
- Firewood
- Wood charcoal (charcoal)
- Wood-fired biomass boilers
- Wood gasification (wood gas) - especially waste wood
- Wood pellets
- Wood residues (waste wood)
Charcoal
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.
- See also the the list of bioenergy technologies.
Sustainability concerns
| Types of bioenergy | edit | |
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Gases: Biopropane | Biogas | Synthetic natural gas | Syngas | ||
| Bioenergy conversion technologies | edit | |
| Technologies categorized by bioenergy processes: Biochemical: Aerobic, Anaerobic, Landfill gas collection (LFG), Biodiesel production, Ethanol production Technologies categorized by feedstock: Technologies by commercialization status: Analysis of technologies: Life-cycle analysis | ||
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| Comments wanted on "Draft Principles" for Sustainable Biofuels What is bioenergy? | Benefits/Risks | Who is doing what? | ||
