Energy from Biomass
Biomass refers to living and recently dead biological material that can be used as fuel or for industrial production. Most commonly, biomass refers to plant matter grown for use as biofuel, but it also includes plant or animal matter used for production of fibres, chemicals or heat. Biomass may also include biodegradable wastes that can be burnt as fuel. It excludes organic material which has been transformed by geological processes into substances such as coal or petroleum.
Biomass is grown from several plants, including miscanthus, switchgrass, hemp, corn, poplar, willow, sugarcane and palm oil. The particular plant used is usually not very important to the end products, but it does affect the processing of the raw material. Production of biomass is a growing industry as interest in sustainable fuel sources is growing.
Although fossil fuels have their origin in ancient biomass, they are not considered biomass by the generally accepted definition because they contain carbon that has been "out" of the carbon cycle for a very long time. Their combustion therefore disturbs the carbon dioxide content in the atmosphere.
Plastics from biomass, like some recently developed to dissolve in seawater, are made the same way as petroleum-based plastics, are actually cheaper to manufacture and meet or exceed most performance standards. But they lack the same water resistance or longevity as conventional plastics.
First generation biofuels
Vegetable oil
Vegetable oil can be used for either food or fuel; the quality of the oil
may be lower for fuel use. Vegetable oil can be used in many older diesel
engines (equipped with indirect injection systems), but only in warm climates.
In most cases, vegetable oil is used to manufacture biodiesel, which is compatible
with most diesel engines when blended with conventional diesel fuel. MAN B&W
Diesel, Wartsila and Deutz AG offer engines that are compatible with straight
vegetable oil. Used vegetable oil is increasingly being processed into biodiesel,
and at a smaller scale, cleaned of water and particulates and used as a fuel.
Biodiesel
Biodiesel is the most common biofuel in Europe. It is produced from oils or fats using transesterification and is a liquid similar in composition to mineral diesel. Its chemical name is fatty acid methyl (or ethyl) ester (FAME). Oils are mixed with sodium hydroxide and methanol (or ethanol) and the chemical reaction produces biodiesel (FAME) and glycerol. 1 part glycerol is produced for every 10 parts biodiesel.
Biodiesel can be used in any diesel engine when mixed with mineral diesel. In some countries manufacturers cover their diesel engines under warranty for 100% biodiesel use, although Volkswagen Germany, for example, asks drivers to make a telephone check with the VW environmental services department before switching to 100% biodiesel (see biodiesel use). Many people have run their vehicles on biodiesel without problems. However, the majority of vehicle manufacturers limit their recommendations to 15% biodiesel blended with mineral diesel. In many European countries, a 5% biodiesel blend is widely used and is available at thousands of gas stations.
In the USA, more than 80% of commercial trucks and city buses run on diesel. Therefore "the nascent U.S. market for biodiesel is growing at a staggering rate—from 25 million gallons per year in 2004 to 78 million gallons by the beginning of 2005. By the end of 2006 biodiesel production was estimated to increase fourfold to more than 1 billion gallons," energy expert Will Thurmond writes in an article for the July-August 2007 issue of THE FUTURIST magazine.
Bioalcohols
Biologically produced alcohols, most commonly ethanol, and less commonly propanol
and butanol, are produced by the action of microorganisms and enzymes through
fermentation of sugars or starches (easiest), or celulose (which is more difficult).
Biobutanol (also called biogasoline) is often claimed to provide a direct
replacement for gasoline, because it can be used directly in a gasoline engine
(in a similar way to biodiesel in diesel engines).
BioGas
Biogas is produced by the process of anaerobic digestion of organic material
by anaerobes. It can be produced either from biodegradable waste materials
or by the use of energy crops fed into anaerobic digesters to supplement gas
yields. The solid byproduct, digestate, can be used as a biofuel or a fertilizer.
Biogas contains methane and can be recovered from industrial anaerobic digesters and mechanical biological treatment systems. Landfill gas is a less clean form of biogas which is produced in landfills through naturally occurring anaerobic digestion. If it escapes into the atmosphere it is a potent greenhouse gas.
Solid Biofuels
Examples include wood, charcoal, and dried manure.
Syngas
Syngas is produced by the combined processes of pyrolysis, combustion, and
gasification. Biofuel is converted into carbon monoxide and energy by pyrolysis.
A limited supply of oxygen is introduced to support combustion. Gasification
converts further organic material to hydrogen and additional carbon monoxide.
The resulting gas mixture, syngas, is itself a fuel. Using the syngas is more efficient than direct combustion of the original biofuel; more of the energy contained in the fuel is extracted.
Syngas may be burned directly in internal combustion engines. The wood gas generator is a wood-fueled gasification reactor mounted on an internal combustion engine. Syngas can be used to produce methanol and hydrogen, or converted via the Fischer-Tropsch process to produce a synthetic petroleum substitute. Gasification normally relies on temperatures >700°C. Lower temperature gasification is desirable when co-producing biochar.
Biofules in Europe
The European Union in its biofuels directive (updated 2006) has set the goal that for 2010 that each member state should achieve at least 5.75% biofuel usage of all used traffic fuel. By 2020 the figure should be 10%. As of January 2008 these aims are being reconsidered in light of certain environmental and social concerns associated with biofuels such as rising food prices and deforestation.
Soil Erosion, Deforestation, and Biodiversity
It is important to note that carbon compounds in waste biomass that is left on the ground are consumed by other microorganisms. They break down biomass in the soil to produce valuable nutrients that are necessary for future crops. On a larger scale, plant biomass waste provides small wildlife habitat, which in turn ripples up through the food chain. The widespread human use of biomass (which would normally compost the field) would threaten these organisms and natural habitats. When cellulosic ethanol is produced from feedstock like switchgrass and saw grass, the nutrients that were required to grow the lignocellulose are removed and cannot be processed by microorganisms to replenish the soil nutrients. The soil is then of poorer quality. Loss of ground cover root structures accelerates unsustainable soil erosion.
Significant areas of native Amazon rainforest have been cleared by slash and burn techniques to make room for sugar cane production, which is used in large part for ethanol fuel in Brazil, and growing ethanol exports. Large-scale deforestation of mature trees (which help remove CO2 through photosynthesis - much better than does sugar cane or most other biofuel feedstock crops do) contributes to un-sustainable global warming atmospheric greenhouse gas levels, loss of habitat, and a reduction of valuable biodiversity. A portion of the biomass should be retained onsite to support the soil resource. In some locations such as Indonesia deforestation for Palm Oil plantations is leading to displacement of Indigenous peoples. Also, extensive use of pesticide for biofuel crops is reducing clean water supplies.
Some mainstream environmental groups support biofuels as a significant step toward slowing or stopping global climate change. However, biofuel production can threaten the environment if it is not done sustainably. As a result, governmental and environmental organisations are turning against biofuels made at a non-sustainable way (hereby preferring certain oil sources as jatropha and lignocellulose over palm oil) and are asking for global support for this.
