(Neilcy Info).Plants use photosynthesis to grow and produce biomass. Also known as biomatter, biomass can be used directly as fuel or to produce biofuels. 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. 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.
Liquid biofuel
Information on pump, California.
Liquid biofuel is usually either a bioalcohol such as ethanol fuel or an oil such as biodiesel or straight vegetable oil. Biodiesel can be used in modern diesel vehicles with little or no modification to the engine. It can be made from waste and virgin vegetable and animal oils and fats (lipids). Virgin vegetable oils can be used in modified diesel engines. In fact the diesel engine was originally designed to run on vegetable oil rather than fossil fuel. A major benefit of biodiesel use is the reduction in net CO2 emissions, since all the carbon emitted was recently captured during the growing phase of the biomass. The use of biodiesel also reduces emission of carbon monoxide and other pollutants by 20 to 40%.[citation needed]
In some areas corn, cornstalks, sugarbeets, sugar cane, and switchgrasses are grown specifically to produce ethanol (also known as grain alcohol) a liquid which can be used in internal combustion engines and fuel cells. Ethanol is being phased into the current energy infrastructure. E85 is a fuel composed of 85% ethanol and 15% gasoline that is sold to consumers. Biobutanol is being developed as an alternative to bioethanol. There is growing international criticism of the production of biofuel crops in association with food crops with respect to issues such as food security, environmental impacts (deforestation) and energy balance.[citation needed]
Another source of biofuel is sweet sorghum. It produces both food and fuel from the same crop. Some studies have shown that the crop is net energy positive ie. it produces more energy than is consumed in its production and utilization.[citation needed]
Solid biomass
Main article: Biomass
Sugar cane residue can be used as a biofuel
Solid biomass is most commonly used directly as a combustible fuel, producing 10-20 MJ/kg of heat. Biomass can also be used to feed bacteria, which can transform it in another form of energy such as hydrogen, using a process called Fermentative hydrogen production.
Its forms and sources include wood fuel, the biogenic portion of municipal solid waste, or the unused portion of field crops. Field crops may or may not be grown intentionally as an energy crop, and the remaining plant byproduct used as a fuel. Most types of biomass contain energy. Even cow manure still contains two-thirds of the original energy consumed by the cow. Energy harvesting via a bioreactor is a cost-effective solution to the waste disposal issues faced by the dairy farmer, and can produce enough biogas to run a farm.
With current technology, it is not ideally suited for use as a transportation fuel. Most transportation vehicles require power sources with high power density, such as that provided by internal combustion engines. These engines generally require clean burning fuels, which are generally in liquid form, and to a lesser extent, compressed gaseous phase. Liquids are more portable because they can have a high energy density, and they can be pumped, which makes handling easier.
Non-transportation applications can usually tolerate the low power-density of external combustion engines, that can run directly on less-expensive solid biomass fuel, for combined heat and power. One type of biomass is wood, which has been used for millennia. Two billion people currently cook every day, and heat their homes in the winter by burning biomass, which is a major contributor to man-made climate change global warming.[citation needed] The black soot that is being carried from Asia to polar ice caps is causing them to melt faster in the summer.[citation needed] In the 19th century, wood-fired steam engines were common, contributing significantly to industrial revolution unhealthy air pollution.[citation needed] Coal is a form of biomass that has been compressed over millennia to produce a non-renewable, highly-polluting fossil fuel.
Wood and its byproducts can now be converted through processes such as gasification into biofuels such as woodgas, biogas, methanol or ethanol fuel; although further development may be required to make these methods affordable and practical. Sugar cane residue, wheat chaff, corn cobs and other plant matter can be, and are, burned quite successfully. The net carbon dioxide emissions that are added to the atmosphere by this process are only from the fossil fuel that was consumed to plant, fertilize, harvest and transport the biomass.
Processes to harvest biomass from short-rotation trees like poplars and willows and perennial grasses such as switchgrass, phalaris, and miscanthus, require less frequent cultivation and less nitrogen than do typical annual crops. Pelletizing miscanthus and burning it to generate electricity is being studied and may be economically viable.[29]
Biogas
Main articles: Biogas and Anaerobic digestion
Biogas can easily be produced from current waste streams, such as paper production, sugar production, sewage, animal waste and so forth. These various waste streams have to be slurried together and allowed to naturally ferment, producing methane gas. This can be done by converting current sewage plants into biogas plants. When a biogas plant has extracted all the methane it can, the remains are sometimes more suitable as fertilizer than the original biomass.
Alternatively biogas can be produced via advanced waste processing systems such as mechanical biological treatment. These systems recover the recyclable elements of household waste and process the biodegradable fraction in anaerobic digesters.
Renewable natural gas is a biogas which has been upgraded to a quality similar to natural gas. By upgrading the quality to that of natural gas, it becomes possible to distribute the gas to the mass market via the existing gas grid.
Source :http://en.wikipedia.org/wiki/Renewable_energy
