Renewable Energy - Biomass
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Biomass
Plants partly use photosynthesis to store solar energy, water and CO2. Biofuel is any fuel that derives from biomass - recently living organisms or their metabolic byproducts, such as manure from cows. It is a renewable energy.
Typically biofuel is burned to release its stored chemical energy. Research into more efficient methods of converting biofuels and other fuels into electricity utilizing fuel cells is an area of very active work. Biomass, also known as biomatter, can be used directly as fuel or to produce liquid biofuel. Agriculturally produced biomass fuels, such as biodiesel, ethanol and bagasse (often a by-product of sugar cane cultivation) can be burned in internal combustion engines or boilers.
Liquid biofuel
Liquid biofuel is usually bioalcohol such as methanol, ethanol and biodiesel. Biodiesel can be used in modern diesel vehicles with little or no modification and can be obtained from waste and crude vegetable and animal oil and fats (lipids). In some areas corn, sugarbeets, cane and grasses are grown specifically to produce ethanol (also known as alcohol) a liquid which can be used in internal combustion engines and fuel cells.
The EU plans to add 5% bioethanol to Europe's petrol by 2010. For the UK alone this would require 1.2 million hectares of arable land to be used exclusively for the production of bioethanol. Within its borders, the country only has 6.5 million hectares of arable land. Other, more efficient sources of biofuel, such as palm and soya oil, would probably have a significant negative environmental impact due to habitat damage in the areas in which they are grown.
Solid biomass
Direct use is usually in the form of combustible solids, either firewood or combustible field crops. Field crops may be grown specifically for combustion or may be used for other purposes, and the processed plant waste then used for combustion. Most sorts of biomatter, including dried manure, can actually be burnt to heat water and to drive turbines. Sugar cane residue, wheat chaff, corn cobs and other plant matter can be, and is, burnt quite successfully. The process releases no net CO2.
Solid biomass van also be gasified, and used as described in the next section.
Biogas
Many organic materials can release gases, due to metabolisation of organic matter by bacteria (fermentation. Landfills actually need to release this gas to prevent dangerous explosions. Animal feces releases methane under the influence of anaerobic bacteria.
Also, under high pressure, high temperature, anaerobic conditions many organic materials such as wood can be gasified to produce gas. This is often found to be more efficient than direct burning. The gas can then be used to generate electricity and/or heat.
Drawbacks
All biomass needs to go through some of these steps: it needs to be grown, collected, dried, fermented and burned. All of these steps require resources and an infrastructure.
Biomatter energy, under the right conditions, is considered to be renewable.
From Wikipedia.