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Fossil Fuels and Biomass Energy

[Wyoming - Forbes]


- Fossil Fuels – Coal

Fossil fuels are the remains of dead plants and animals on land and in the seabed. These are formed from the fossilized remains of dead animals and plants that are exposed to heat and pressure in the earth’s crust for hundreds of millions of years. 

Fossil fuels primarily consist of hydrocarbons. They contain carbon and hydrogen in varying ratios, such as methane, that has a low carbon to hydrogen ratio, or anthracite coal, which is almost pure carbon. Hydrocarbons are formed when the fossilized remains of dead organisms are chemically altered over hundreds of millions of years by intense pressure and heat found in the earth’s crust. The chemical energy ‘stored’ in these fuels is released during combustion to produce electric power. 

According to estimates provided by the Energy Information Administration, fossil fuels account for 86% of the total energy produced in the world. Of this, petroleum accounted for 36.8%, coal 26.6% and natural gas 22.9%. However, fossil fuels are non-renewable sources of energy. They take hundreds of millions of years to form and are depleted much faster than new reserves can be created. It is estimated that 23.5 tons of fossilized organic material deposited on the ocean floor is required to produce 1 liter of gasoline. In 1997, the total amount of fossil fuel used was equivalent to plant matter that grew on the entire land and ocean surface of the earth over a period of 422 years. 

Another disadvantage of our heavy dependence on fossil fuels is the amount of carbon dioxide produced during combustion, which is estimated at 21.3 billion tons per year. However, natural processes are capable of absorbing only about half of the total amount of carbon dioxide emissions released into the atmosphere, which means every year the amount of carbon dioxide in the atmosphere is increasing by 10.65 billion tons, which is theorized to be the leading contributor to global warming that could potentially have very adverse effects on the ecosystem.  


Amager Bakke_Copenhagen_Denmark_110820A
[Amager Bakke , also known as Amager Slope or Copenhill, is a combined heat and power waste-to-energy plant and sports facility in Amager, Copenhagen, Denmark - Civil Engineering Discoveries]

- Fossil Fuels – Natural Gas

Natural gas is usually found along with fossil fuels, in coal-beds and trapped in other types of rock. It is created by methanogenic organisms present in landfills, marshes and wetlands. It naturally consists of methane and small amounts of other gases such as ethane, propane, butane, pentane, hydrocarbons of higher molecular weight, sulfur, helium and nitrogen. The constituents of natural gas other than methane need to be removed before natural gas can be used as a source of fuel. 

Although natural gas is considered to be cleaner than other fossil fuels, it has still been found to contribute to pollution and global warming. While it can be used to supplement the world’s ever depleting reserves of traditional fossil fuels, it is not a 100% clean, non-polluting alternative. In 2004, carbon dioxide emissions resulting from the use of natural gas stood at 5,300 million tons while coal and oil contributed to carbon dioxide emissions of 10,600 million tons and 10,200 million tons, respectively. However, this trend is expected to reverse by 2030 when natural gas is likely to emit 11,000 million tons of carbon dioxide as opposed to 8,400 million tons from coal and 17,200 tons from oil at that time. Also, when released directly into the atmosphere, natural gas is a far more potent greenhouse gas than carbon dioxide but since this occurs in very small amounts, it is currently not a major cause of concern.


- Biomass Energy

Biomass power is carbon neutral electricity generated from renewable organic waste that would otherwise be dumped in landfills, openly burned, or left as fodder for forest fires. When burned, the energy in biomass is released as heat. If you have a fireplace, you already are participating in the use of biomass as the wood you burn in it is a biomass fuel. 

In biomass power plants, wood waste or other waste is burned to produce steam that runs a turbine to make electricity, or that provides heat to industries and homes. Fortunately, new technologies -- including pollution controls and combustion engineering -- have advanced to the point that any emissions from burning biomass in industrial facilities are generally less than emissions produced when using fossil fuels (coal, natural gas, oil).  

Biomass resources that are available on a renewable basis and are used either directly as a fuel or converted to another form or energy product are commonly referred to as “feedstocks.”  Biomass feedstocks include dedicated energy crops, agricultural crop residues, forestry residues, algae, wood processing residues, municipal waste, and wet waste (crop wastes, forest residues, purpose-grown grasses, woody energy crops, algae, industrial wastes, sorted municipal solid waste [MSW], urban wood waste, and food waste).  

  • DEDICATED ENERGY CROPS -- Dedicated energy crops are non-food crops that can be grown on marginal land (land not suitable for traditional crops like corn and soybeans) specifically to provide biomass. These break down into two general categories: herbaceous and woody. Herbaceous energy crops are perennial (plants that live for more than 2 years) grasses that are harvested annually after taking 2 to 3 years to reach full productivity. These include switchgrass, miscanthus, bamboo, sweet sorghum, tall fescue, kochia, wheatgrass, and others. Short-rotation woody crops are fast-growing hardwood trees that are harvested within 5 to 8 years of planting. These include hybrid poplar, hybrid willow, silver maple, eastern cottonwood, green ash, black walnut, sweetgum, and sycamore. Many of these species can help improve water and soil quality, improve wildlife habitat relative to annual crops, diversify sources of income, and improve overall farm productivity. 
  • AGRICULTURAL CROP RESIDUE -- There are many opportunities to leverage agricultural resources on existing lands without interfering with the production of food, feed, fiber, or forest products. Agricultural crop residues, which include the stalks and leaves, are abundant, diverse, and widely distributed across the United States. Examples include corn stover (stalks, leaves, husks, and cobs), wheat straw, oat straw, barley straw, sorghum stubble, and rice straw. The sale of these residues to a local biorefinery also represents an opportunity for farmers to generate additional income.  
  • FORESTRY RESIDUES -- Forest biomass feedstocks fall into one of two categories: forest residues left after logging timber (including limbs, tops, and culled trees and tree components that would be otherwise unmerchantable) or whole-tree biomass harvested explicitly for biomass. Dead, diseased, poorly formed, and other unmerchantable trees are often left in the woods following timber harvest. This woody debris can be collected for use in bioenergy, while leaving enough behind to provide habitat and maintain proper nutrient and hydrologic features. There are also opportunities to make use of excess biomass on millions of acres of forests. Harvesting excessive woody biomass can reduce the risk of fire and pests, as well as aid in forest restoration, productivity, vitality, and resilience. This biomass could be harvested for bioenergy without negatively impacting the health and stability of forest ecological structure and function. 
  • ALGAE -- Algae as feedstocks for bioenergy refers to a diverse group of highly productive organisms that include microalgae, macroalgae (seaweed), and cyanobacteria (formerly called “blue-green algae”). Many use sunlight and nutrients to create biomass, which contains key components—including lipids, proteins, and carbohydrates— that can be converted and upgraded to a variety of biofuels and products. Depending on the strain, algae can grow by using fresh, saline, or brackish water from surface water sources, groundwater, or seawater. Additionally, they can grow in water from second-use sources, such as treated industrial wastewater; municipal, agricultural, or aquaculture wastewater; or produced water generated from oil and gas drilling operations.  
  • WOOD PROCESSING RESIDUES -- Wood processing yields byproducts and waste streams that are collectively called wood processing residues and have significant energy potential. For example, the processing of wood for products or pulp produces unused sawdust, bark, branches, and leaves/needles. These residues can then be converted into biofuels or bioproducts. Because these residues are already collected at the point of processing, they can be convenient and relatively inexpensive sources of biomass for energy. 
  • SORTED MUNICIPAL WASTE -- MSW resources include mixed commercial and residential garbage, such as yard trimmings, paper and paperboard, plastics, rubber, leather, textiles, and food wastes. MSW for bioenergy also represents an opportunity to reduce residential and commercial waste by diverting significant volumes from landfills to the refinery.  
  • WET WASTE -- Wet waste feedstocks include commercial, institutional, and residential food wastes (particularly those currently disposed of in landfills); organic-rich biosolids (i.e., treated sewage sludge from municipal wastewater); manure slurries from concentrated livestock operations; organic wastes from industrial operations; and biogas (the gaseous product of the decomposition of organic matter in the absence of oxygen) derived from any of the above feedstock streams. Transforming these “waste streams” into energy can help create additional revenue for rural economies and solve waste-disposal problems.

 [More to come ...]

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