mercredi 29 novembre 2017

Controversy over alternative energy

Biomass power renewable energy

Biomass in ecology

  The definition of biomass in ecology is the mass of living organisms in a given area or ecosystem at a given time. Biomass can refer to one or more species biomass which is the weight of one species in the community or to the community biomass which is the mass of all the species in the community. Biomass can include plants (phytomass) and biomass (zoomass), and in our present case, it's the weight mass of organically bound carbon number in tonne present who will be considered for its energy potential.

It is estimated that:
  • the total live biomass on Earth apart from bacteria is about 560 billion tons of carbon 
  •  The world bacterial biomass was calculated to be 350-550 billion of tons of carbon, equal to 60%-100% of carbon in plants.
  • 95% of the biomass is in the continents
  • only 5-10 billion of tons of carbon are found in the oceans
  • on land, there's 1000 times more plant biomass than animal biomass 
  • 18% of all this plant biomass is eaten by animals on land
  • in the ocean, there's 30 times more animal biomass than plant biomass
  • most plant biomass on the ocean is eaten by animal's biomass 
  • the Earth's total annual production of the biomass it is estimated to be 100 billion tons of carbon a year. 


  Biomass power is the energy derived from vegetable or animal matter which can be harnessed to produce electricity. In the field of bio-energy, biomass is the part of it still usable as a source of energy; either directly by combustion or indirectly after methanation (biogas, or its uncluttered version bio-methane).     
  Wood is still the largest biomass energy source today. Natural wood logs are used on a large scale, this includes also branches, forest residues, dead trees, municipal wastes, etc... The largest source of energy from wood is pulping liquor or "black liquor" a waste product from processes of pulp, paper, and paperboard industry. It's used in the pulp mill's industry. They use recovery boilers to burn the black liquor to create and produce steam. Wood is considered an alternative energy source because it pollutes less than fossil fuel, and it is being considered a renewable energy source because plants crop can be replaced with new growth.
  Pellet fuels are made from organic compressed matter or biomass. Pellets are made from one of any five general categories of biomass: industrial waste and co-products, food wastes, agricultural residues, energy crops, and virgin lumber. Wood pellets are the most common fuel pellets, and they're made from compacted sawdust and related industrial wastes.

  Many crops are of interest for their ability to provide high yields of biomass, like sugarcane. Bagasse, its residue is produced in great quantities. The production of bagasse is evaluated at 250 million tons a year, it can serve to feed animals. It has a poor nutritive value and can be fermented by white-rot fungi to produce enriched animal feed. Bagasse and other sources such as cornstarch who are rich in sugar can be fermented to produce first-generation biofuels. Bio-ethanol is an alcohol that can serve directly in a fuel cell to produce electricity or as an additive to gasoline. But utilizing food-based resources for fuel production can only aggravate the food shortage problem. Second-generation biofuels, on the other hand, utilize non-food biomass products such as municipal and agriculture wastes. Despite being the favored alternative of production of bio-fuel,
second-generation biofuels isn't achieved yet due to technological issues. Energy derived from biomass is projected to be the largest non-hydroelectric renewable source of electricity in the U.S. between 2000 and 2020.

  Some biomass products like ethanol and wood have a poor calorific value, compared to the energy released by burning 1 tonne of oil equivalent 0,3215 (toe).
The tonne of oil equivalent (toe) is a unit of energy, it's approximately 42 gigajoules or 11 600 kWh. And a tonne of crude oil is approximately 7,3 barrels. 


The calorific value in comparison with crude oil: 

  • 2,2 tonnes of wood = 1 toe 
  • 1,5 tonnes of high-quality coal = 1 toe
  • 1 ton of uranium (in light water reactor) = 10000-16000 toe
  • 1100 m³ of natural gas = 1 toe 
  • 1 tonne of diesel = 1,01 toe
  • 1 tonne of bio-ethanol = 0,64 toe

  Electricity production comparison value:

  • geothermal electricity :              1MWh = 0,860 toe
  • nuclear electricity :                    1MWh = 0,261 toe
  • fossil or renewable electricity :    1MWh = 0,086 toe
  • Natural gas electricity :              1MWh = 0,077 toe

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