Energy Products from Waste and Biomass

The basic processes for the conversion of biomass into energy products are pyrolysis or thermo chemical and enzymatic processes. In March 2009, a patent was issued to the BCD Group Inc -11 on a new low temperature method for conversion of biomass to product containing 80% and higher contents of carbon. Unlike other thermo chemical processes, organic waste and biomass are converted to carbon and hydrogen without formation of carbon oxides at lower temperatures 290-350°C and lower than pyrolysis 400-700°C and higher. The conversion of biomass and lignin to carbon and hydrogen are presented in Figures 5 and 6 below. R(OH)x  represents the hydroxyl contents of biomass that are removed by chemical reactions to eliminate formation of carbon oxides and loss of carbon as reaction medium is heated to 350°C temperatures. The hydrogen donors promote removal of oxygen from biomass as shown in the equation and thus the carbon is not removed as carbon oxides and is a recoverable product.

 

The feed stocks for CTH conversion to energy are:

Municipal solid waste (celluloses)
Plastics
Rubber
Crop residues
Forestry waste

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The conversion of biomass and lignin to carbon and hydrogen is presented in Figures 5 and 6 below. ROH is represents the high hydroxyl contents of biomass that are removed to minimize formation of carbon oxides and loss of carbon as reaction medium is heated to higher temperatures. The hydrogen donor materials promote remove of oxygen as shown in the equation and thus the carbon remains as a recoverable product.


Figure 5


Figure 6

The unique attribute of this development is that waste hydrocarbons and heavy oils are employed as hydrogen donor and are converted to carbon, hydrogen and lower molecular hydrocarbons.


Figure 7

In the typical pyrolysis process (Figure 7) the temperature requirements for waste conversion to carbonaceous products, oils and gases ranges from 700 to 900° C as shown for processing rice hull and straw. Inspection of gas composition generated by pyrolysis reveals very high loss of carbon from feed stocks as carbon oxides. Gas analysis of sludge (Figure 8) by CTH process reveals that there was little or no loss of carbon from the decomposed sludge as carbon oxides. Waste decomposition into a high content carbon product can be achieved with formation and loss of carbon as greenhouse gases.


Figure 8


Figure 9

As shown in Figure 9, when 1 ton of biomass is processed by the CTH process essentially all carbon in feed stock is recovered. Chemical analysis performed products by the Galbraith laboratories, Knoxville, Tennessee revealed that solids residue carbon content is greater than
80% and greater than 90 % when corrected for added reagent and ash contents of processed feed stock. The general feed stock processing scheme is shown in Figure 10.


Figure 10

Uses of Carbon

Preliminary studies have been completed on the production of Syn-gas from carbon product and use as fuel for Solid Oxide Fuel Cells. These studies indicated the potential commercial value of this carbon product for these applications. There are many other potential industrial applications for this carbon product as listed below

Commercial Product Applications

Some of the uses of this carbon product include:

  • Direct use as fuel or charcoal
  • Fuel for Syn gas preparation
  • Fuel for Solid Oxide Fuel Cells
  • Carbon black products
  • Inert filler
  • Activated carbon

The Advantages of CTH production of products from biomass are:

  • Operates at lower temperatures of 300° – 400° C
  • Employs low cost chemicals
  • Rapidly transforms organic materials to a carbon residue
  • Effects complete dehydrogenation of hydrogen- bearing materials