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BIOMASS ENERGY. Biomass consists of all living plant matter as well as organic wastes derived from plants, humans, marine life, and animals.

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Biomass energy

BIOMASS ENERGY

Biomass consists of all living plant matter as well as organic wastes derived from plants, humans, marine life, and animals.

In addition trees, grasses, animal dung, as well as sewage, garbage wood construction residues and other components of municipal waste are all examples of biomass

Biomass energy is the first form of energy exploited by man. Biomass is the natural energy for conversion of solar energy to high-energy content products that can be stored transported, and used conveniently.


Characteristics of biomass
CHARACTERISTICS OF BIOMASS

  • Biomass energy is a renewable

  • Connected to farming -economics

  • Multiuse – food, shelter, energy, materials

  • Environmental concerns include land and water use, fertilizer and other nutrient requirements

  • Naturally diffuse and distributed – harvesting and transport and distribution are important


Source of biomass energy
SOURCE OF BIOMASS ENERGY

The main source of biomass energy is from the sun. Plants grow by the process of photosynthesis in which sunlight transforms two abundant raw materials, water and carbondioxide, to carbohydrates and other complex organic compounds of great natural and commercial value. The reaction is shown below:

  • Average solar incidence is about 4000 W/m2/day

  • Biomass capture efficiency is ~ 1%

  • Thin film photovoltaic efficiency is ~ 10%

The process is intermediate in the formation of glucose/sucrose, cellulose polymers, fuel for plant respiration, or variety of other compounds depicted in the figure below:


Renewability indices and biomass resources
RENEWABILITY INDICES AND BIOMASS RESOURCES

Since biomass is considered as a renewable there is the need to estimate how rapidly it is regenerated in quantities that are useful to humans.

Semi quantitative measure of the rate of regeneration was proposed by Paul Weisz (1978)

His idea compared the time for regeneration of commercially meaningful quantity of the resource quantity of the resource under scrutiny, Tr to a time at which the resource will be beneficial to mankind Tu



Renewability indices and biomass resources cont1
RENEWABILITY INDICES AND BIOMASS RESOURCES CONT.

Table 10.1 Selected Dimensionless Time Constant Related to the Renewability of Biomass


Biomass relevance to energy production
BIOMASS RELEVANCE TO ENERGY PRODUCTION

  • BIOMASS UTILIZATION

  • Figure 10.2 Explain the biological and thermal routes of biomass energy conversion


Advantages and disadvantages
ADVANTAGES AND DISADVANTAGES

  • Advantages

    • It is renewable and domestic available

    • Its disperse nature leverages its potential impact by enabling it to function as a distributed energy source.

    • Biomass derived products can substitutes those of plastics and metalic products which require abundance of energy.

    • Its use as a source of energy offers another major benefit to sustainability namely a pathway to manage municipal and agricultural waste.

    • It has the potential to combat the atmospheric buildup of the greenhouse gas CO2

    • It act as a feedstock and has lower sulfur content


Advantages and disadvantages1
ADVANTAGES AND DISADVANTAGES

  • Disadvantages

    • It has low energy content compared to coal and petroleum derived fuels

    • Intensive cultivation may stress water resource and deplete soil nutrients

    • The wide dispersion of biomass combined with the low intensity of production per unit land areas are serious disadvantages when there is a need to supply huge amounts of energy to a small area.

    • It has high cost of transportation







Thermal convesion of biomass
THERMAL CONVESION OF BIOMASS in 2050

  • Biomass to Electricity

    • Co-firing with coal to reduce sulfur emissions and smooth a transition to reduced fossil dependency

    • Repowering (ie is backlifting an existing generating station to switch to biomass fuel, or add a biomass-fired generator to an existing fossil fueled unit)

    • Direct combustion in a Rankine cycle to raise steam to operate a turbine generator

    • Various configurations of combined cycles in which the biomass is first gasified and the gas then combusted to generate steam or, in a gas turbine, to provide motive power with the option for extracting additional electricity from the waste heat

    • Thermal of hydrothermal conversion of the biomass to other fuels that, after substantial cleaning, are combusted to generate steam or motive power, or fed to a fuel cell for direct conversion to electricity


Biomass to fuels
BIOMASS TO FUELS in 2050

  • Bioethanol in the United States

  • Bioethanol from Corn

  • • Corn grain is the feedstock

  • – with a current capacity of ~144 M dry tons

  • – equivalent to 10 – 14 B gallons of ethanol

  • – ~10% of U.S. fuel consumption

  • Current ethanol production is ~2 B gallons

  • • Liquid fuel additive/replacement

  • – environmentally friendly oxygenate

  • – fuel flexible cars can use blends up to 85% ethanol

  • Subsidized heavily to make it competitive with gasoline




  • Biomass to electricity
    BIOMASS TO ELECTRICITY CORN FEEDSTOCK

    EXAMPLE OF US INSTALLED CAPACITY


    Challenges to biomass based electricity production
    CHALLENGES TO BIOMASS BASED ELECTRICITY PRODUCTION CORN FEEDSTOCK

    • Low heat to power efficiency of combustion steam turbines

      – 18-24% (14,000-19,000 Btu/kWh)

    • Alkali and other trace metal deposits and emissions

    • Particulate Deposits and Emissions

    • NOx Emissions

    • Cost of Electricity

      – $0.065 – 0.08/kWh

    • Lower Energy Density

      – Oxygen = 30-45 wt % dry basis

    • Use of Land, Water, Nutrients

    • Displacement of Higher Value Crops


    Bioconversion
    BIOCONVERSION CORN FEEDSTOCK

    Bioconversion or biochemical processing refers to the direct or adaptive use of the chemistry of living things to transform one substance to another eg. Fermentation

    BIOGAS

    ~ 50%vol CH4, 50%vol CO2

    • From Anaerobic Digestion of wet Biomass

      – Animal, Human Wastes

      – Sewage Sludge

      – Crop Residues

  • By-Products: Nitrogen-rich Sludge (Fertilizer) and Fewer Pathogens

  • Extensive Use in India and China (Millions of Digesters); Industrialized Countries (Stockyards, Municipal Sewage, ~5000 Digesters)

  • Major Goals

    – Environmental Neutralization of Waste

    – Fertilizer From Waste


  • Biogas from anaerobic digestion
    BIOGAS FROM ANAEROBIC DIGESTION CORN FEEDSTOCK

    • Gas Production Rate

      • 0.2 Nm3/m3/day Floating or Fixed Cover Digesters (Villages: China, India)

      • 4-8 Nm3/m3/day industrial Scale Technology (Dilute Industrial, Municipal Wastes)

    • Estimated Costs of Biogas $/million Btu

      – Household 11.6

      – Village 5.8

      – Industrial 0.7-1.1


    Overall process chemistry for production of bisgas by anaerobic digestion of wet biomass

    Bacteria that promote fermentation and CORN FEEDSTOCK

    acetic acid fermentation

    COMPLEX

    ORGANIC

    MATTER

    SHORT CHAIN ACIDS

    ALCOHOLS, H2 etc.

    CH4 CO2 MINERAL AND

    NITROGEN-RICH

    EFFLUENT SLURY

    Bacteria that promote methane formation

    OVERALL PROCESS CHEMISTRY FOR PRODUCTION OF BISGAS BY ANAEROBIC DIGESTION OF WET BIOMASS

    • 35-55ºC

    • Process Variables: pH, feed-rate & C/N ratio, solids residence time (SRT), hydraulic residence time (HRT), stirring

    • Simple technologies SRT and HRT of order weeks


    Fixed dome small scale anaerobic digester
    FIXED DOME SMALL SCALE ANAEROBIC DIGESTER CORN FEEDSTOCK

    • FIGURE 10.7



    Potential adverse environmental impacts of biomass production and utilization for energy
    POTENTIAL ADVERSE ENVIRONMENTAL IMPACTS OF BIOMASS PRODUCTION AND UTILIZATION FOR ENERGY


    Opportunities for biomass
    OPPORTUNITIES FOR BIOMASS PRODUCTION AND UTILIZATION FOR ENERGY

    • Reducing Greenhouse Gas CO2

    • Restoring Forest Resources

    • Renewable Carbon Source for Energy Future Dominated by Non-Carbon Based Electricity, e.g. Nuclear, Geothermal, and Solar. Biomass Becomes Significant Raw Material for:

      – Liquid Hydrocarbon Fuels–Chemicals

      – Other High Value Products


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