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Alex Hobbs   Biomass

Alex Hobbs Biomass






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  • Miyamoto, K. (ed.), "Renewable Biological Systems for Alternative Sustainable Energy Production" (Section 1.2.1. Photosynthetic efficiency), FAO Agricultural Services Bulletin #128 Approximately 114 kilocalories of free energy are stored in plant biomass for every mole of CO2 fixed during photosynthesis. Solar radiation striking the earth on an annual basis is equivalent to 178,000 terawatts, i.e. 15,000 times that of current global energy consumption. Although photosynthetic energy capture is estimated to be ten times that of global annual energy consumption, only a small part of this solar radiation is used for photosynthesis. Approximately two thirds of the net global photosynthetic productivity worldwide is of terrestrial origin, while the remainder is produced mainly by phytoplankton (microalgae) in the oceans which cover approximately 70% of the total surface area of the earth. Since biomass originates from plant and algal photosynthesis, both terrestrial plants and microalgae are appropriate targets for scientific studies relevant to biomass energy production. Any analysis of biomass energy production must consider the potential efficiency of the processes involved. Although photosynthesis is fundamental to the conversion of solar radiation into stored biomass energy, its theoretically achievable efficiency is limited both by the limited wavelength range applicable to photosynthesis, and the quantum requirements of the photosynthetic process. Only light within the wavelength range of 400 to 700 nm (photosynthetically active radiation, PAR) can be utilized by plants, effectively allowing only 45% of total solar energy to be utilized for photosynthesis. Furthermore, fixation of one CO2 molecule during photosynthesis, necessitates a quantum requirement of ten (or more), which results in a maximum utilization of only 25% of the PAR absorbed by the photosynthetic system. On the basis of these limitations, the theoretical maximum efficiency of solar energy conversion is approximately 11%. In practice, however, the magnitude of photosynthetic efficiency observed in the field, is further decreased by factors such as poor absorption of sunlight due to its reflection, respiration requirements of photosynthesis and the need for optimal solar radiation levels. The net result being an overall photosynthetic efficiency of between 3 and 6% of total solar radiation. From http://www.fao.org/docrep/w7241e/w7241e00.htm#Contents
  • Biopower Technology Description Biopower, also called biomass power, is the generation of electric power from biomass resources – now usually urban waste wood, crop, and forest residues; and, in the future, crops grown specifically for energy production. Biopower reduces most emissions (including emissions of greenhouse gases-GHGs) compared with fossil fuel-based electricity. Because biomass absorbs CO2 as it grows, the entire biopower cycle of growing, converting to electricity, and regrowing biomass can result in very low CO2 emissions compared to fossil energy without carbon sequestration, such as coal, oil or natural gas. Through the use of residues, biopower systems can even represent a net sink for GHG emissions by avoiding methane emissions that would result from landfilling of the unused biomass. Representative Technologies for Conversion of Feedstock to Fuel for Power and Heat • Homogenization is a process by which feedstock is made physically uniform for further processing or for combustion (includes chopping, grinding, baling, cubing, and pelletizing). • Gasification (via pyrolysis, partial oxidation, or steam reforming) converts biomass to a fuel gas that can be substituted for natural gas in combustion turbines or reformed into H2 for fuel cell applications. • Anaerobic digestion produces biogas that can be used in standard or combined heat and power (CHP) applications. Agricultural digester systems use animal or agricultural waste. Landfill gas also is produced anaerobically. • Biofuels production for power and heat provides liquid-based fuels such as methanol, ethanol, hydrogen, or biodiesel. Representative Technologies for Conversion of Fuel to Power and Heat • Direct combustion systems burn biomass fuel in a boiler to produce steam that is expanded in a Rankine Cycle prime mover to produce power. • Cofiring substitutes biomass for coal or other fossil fuels in existing coal-fired boilers. • Biomass or biomass-derived fuels (e.g. syngas, ethanol, biodiesel) also can be burned in combustion turbines (Brayton cycle) or engines (Otto or Diesel cycle) to produce power. • When further processed, biomass-derived fuels can be used by fuels cells to produce electricity System Concepts • CHP applications involve recovery of heat for steam and/or hot water for district energy, industrial processes, and other applications. Nearly all current biopower generation is based on direct combustion in small, biomass-only plants with relatively low electric efficiency (20%), although total system efficiencies for CHP can approach 90%. Most biomass direct-combustion generation facilities utilize the basic Rankine cycle for electric-power generation, which is made up of the steam generator (boiler), turbine, condenser, and pump. For the near term, cofiring is the most cost-effective of the power-only technologies. Large coal steam plants have electric efficiencies near 33%. The highest levels of coal cofiring (15% on a heat-input basis) require separate feed preparation and injection systems. Biomass gasification combined-cycle plants promise comparable or higher electric efficiencies (> 40%) using only biomass, because they involve gas turbines (Brayton cycle), which are more efficient than Rankine cycles, as is true for coal. Other technologies being developed include integrated gasification/fuel cell and biorefinery concepts. Technology Applications • The existing biopower sector – nearly 1,000 plants – is mainly comprised of direct-combustion plants, with an additional small amount of cofiring (six operating plants). Plant size averages 20 MWe, and the biomass-to-electricity conversion efficiency is about 20%. Grid-connected electrical capacity has increased from less than 200 MWe in 1978 to more than 9,700 MWe in 2001. More than 75% of this power is generated in the forest products industry’s CHP applications for process heat. Wood-fired systems account for close to 95% of this capacity. In addition, about 3,300 MWe of municipal solid waste and landfill gas generating capacity exists. Recent studies estimate that on a life-cycle basis, existing biopower plants represent an annual net carbon sink of 4 MMTCe. Prices generally range from 8¢/kWh to 12¢/kWh. Current Status • CHP applications using a waste fuel are generally the most cost-effective biopower option. Growth is limited by availability of waste fuel and heat demand. • Biomass cofiring with coal ($50 - 250/kW of biomass capacity) is the most near-term option for large-scale use of biomass for power-only electricity generation. Cofiring also reduces sulfur dioxide and nitrogen oxide emissions. In addition, when cofiring crop and forest-product residues, GHG emissions are reduced by a greater percentage (e.g. 23% GHG emissions reduction with 15% cofiring). • Biomass gasification for large-scale (20-100MWe) power production is being commercialized. It will be an important technology for cogeneration in the forest-products industries (which project a need for biomass and black liquor CHP technologies with a higher electric-thermal ratio), as well as for new baseload capacity. Gasification also is important as a potential platform for a biorefinery. • Small biopower and biodiesel systems have been used for many years in the developing world for electricity generation. However, these systems have not always been reliable and clean. DOE is developing systems for village-power applications and for developed-world distributed generation that are efficient, reliable, and clean. These systems range in size from 3kW to 5MW and completed field verification by 2003. • Approximately 15 million to 21 million gallons of biodiesel are produced annually in the United States. • Utility and industrial biopower generation totaled more than 60 billion kWh in 2001, representing about 75% of nonhydroelectric renewable generation. About two-thirds of this energy is derived from wood and wood wastes, while one-third of the biopower is from municipal solid waste and landfill gas. Industry consumes more than 2.1 quadrillion Btu of primary biomass energy. Technology History • In the latter part of the 19th century, wood was the primary fuel for residential, commercial, and transportation uses. By the 1950s, other fuels had supplanted wood. In 1973, wood use had dropped to 50 million tons per year. • At that point, the forest products and pulp-and-paper industries began to use wood with coal in new plants and switched to wood-fired steam power generation. • The Public Utility Regulatory Policies Act (PURPA) of 1978 stimulated the development of nonutility cogeneration and small-scale plants to in the wood-processing and pulp-and-paper sectors and increased supply of power to the grid. • The combination of low natural gas prices, improved economies of scale in combined cycle palns, and withdrawal of incentives in the late 1980s, led to annual installations declining from about 600 MW in 1989, to 300-350MW in 1990. • There are now nearly 1,000 wood-fired plants in the United States, with about two-thirds of those providing power (and heat) for on-site uses only. Technology Future The levelized cost of electricity (in constant 1997$/kWh) for biomass direct-fired and gasification configurations are projected to be: 2000 2010 2020 Direct-fired 7.5 7.0 5.8 Gasification 6.7 6.1 5.4 Source: Renewable Energy Technology Characterizations, EPRI TR-109496, 1997. R&D directions include: Gasification – This technology requires extensive field verification in order to be adopted by the relatively conservative utility and forest-products industries, especially to demonstrate integrated operation of biomass gasifier with advanced-power generation (turbines and/or fuel cells). Integration of gasification into a biorefinery platform is a key new research area. Small Modular Systems – Small-scale systems for distributed or minigrid (for premium or village power) applications will be increasingly in demand. Cofiring – The DOE biopower program is moving away from research on cofiring, as this technology has reached a mature status. However, continued industry research and field verifications are needed to address specific technical and nontechnical barriers to cofiring. Future technology development will benefit from finding ways to better prepare, inject, and control biomass combustion in a coal-fired boiler. Improved methods for combining coal and biomass fuels will maximize efficiency and minimize emissions. Systems are expected to include biomass cofiring up to 5% of natural gas combined-cycle capacity. Source: National Renewable Energy Laboratory. U.S. Climate Change Technology Program. Technology Options: For the Near and Long Term. DOE/PI-0002. November 2003 (draft update, September 2005).
  • SE has cheap power, but not everything is factored in. This graph was taken from http://www.poweringthesouth.org/index.html
  • In an October 12 issue of the industry publication “Energy Daily” Duke Energy CEO Jim Rogers predicted that much stronger green building codes will be adopted in the near future.
  • Who has biggest economic opportunity for carbon marketplace? 9 of the world’s 30 largest emitters of greenhouse gases are southeastern U.S. states. North Carolina is 12 th largest GHG emitter in the U.S. and 24 th in the world. However, NC and the southeast have more of an economic opportunity than the rest of the U.S. in addressing our greenhouse gas emissions, because we rank below the rest of the U.S. and the industrialized world in use of renewable energy and energy efficiency.
  • So, this is a general comparison of SHP to CHP to give you a better sense of where the efficiency gains are coming from: You can see here that for the production of equal amounts of power (30 units) and heat (45 units), that The separate generation has greater CUMULATIVE losses (68+11) along the way versus just 25 for the combined generation of heat and power For equal amount heat and power generation, significantly less fuel is used

Alex Hobbs   Biomass Alex Hobbs Biomass Presentation Transcript

  • Biomass & CHP Opportunity for NC Alex Hobbs, PhD, PE NC Solar Center www.ncsc.ncsu.edu Sierra Club Forum November 14, 2009
  • Living within our energy budget Carbon production cycle based on agricultural biomass for production of hydrocarbon based energy and products
  • Energy from the Sun An sustainable supply of energy for the next few billion years & nuclear energy we all support 150 x 10 6 km The Sun destroys 4 x 10 9 kg/s of mass and releases energy at the rate of 3.8 x 10 26 J/s. Diameter = 1.39 x 10 6 km Weight = 2 x 10 30 kg Diameter = 12,700 km Earth 32’ ≈ .53° E = mc 2 One billionth of the Sun’s radiation actually reaches Earth 178,000 Terawatts Where 1 tera is 10 12 Surface solarization = 1000 W/m 2
  • NC’s most widely deployed solar collector Woody Biomass 6 CO 2 + 6 H 2 O + Sunlight -> (CH 2 O) 6 + 6 O 2  nutrients Solar Powered Biomass
  • Long View of Climate Change
    • Venus, Earth & Mars were 96% CO2 originally
    • Carbon has been sequestered into the earth’s crust for 3+ billion years
    • With current growth in fossil fuel usage we will release all fuel grade carbon to the atmosphere in ~ 200 years
  • World carbon balance
  • Natural decomposition of 100 kg of biomass: 111.7 kg CO 2 + 6.5 kg CH 4 = 248.2 kg CO 2 -equiv If 100 kg biomass were to completely decompose aerobically or combusted: 185.4 kg CO2 GHG effect reduced by 62.8 kg per 100 kg of biomass Avoided Biomass Decomposition 100 kg biomass (bone dry) (50.6 kg carbon) 46% landfilled 54% mulched 90.0 kg CO 2 (24.6 kg carbon) 90% aerobic 54 kg biomass (27.3 kg carbon) 14.8 kg CO 2 (4.05 kg carbon) 5.4 kg CH 4 (4.05 kg carbon) 46 kg biomass (23.3 kg carbon) anaerobic decomposition 50% to CO 2 50% to CH 4 40.5% captured and combusted 59.5% released as CH 4 5.4 kg CO 2 (1.5 kg carbon) 2.9 kg CH 4 (2.2 kg carbon) of the non-lignin lignin and 50% resistant to degradation 15.2 kg carbon degradation of 50% of cellulose & hemicellulose 8.1 kg carbon 10% oxidized by soil microbes 1.5 kg CO 2 (0.4 kg carbon) 90% not oxidized by soil microbes 4.9 kg CH 4 (3.65 kg carbon) 10% anaerobic decomposition 3.6 kg CH 4 (2.7 kg carbon)
  • Life Cycle CO 2 and Energy Balance for a Direct-Fired Biomass System Direct-Fired Biomass Residue System 134% carbon closure Mann and Spath (1997). NREL/TP-430-23076 Net greenhouse gas emissions -410 g CO 2 equivalent/kWh Landfill and Mulching Transportation Construction Power Plant Operation 10 3 1,204 1,627 Avoided Carbon Emissions 1.0 Fossil Energy In Electricity Out 28.4
  • Environmental Advantage of Biomass Based Energy Production NREL LCA studies by Mann & Spath
  • Wood Biomass to Electricity 45 MWe Craven County Wood Energy (CCWE) Operating since 1990 at 95% availability
  • NC Wood vs. Coal Emissions 2003 Wade Bennett NC GreenPower presentation
  • Biomass R&D Act of 2000 Source: Martin Holmer Management Harvesting Environmental sustainability
  • Let’s focus on Southeastern energy issues In the Southeast what types of reasonable “solutions” may be provided through policy and technology changes?
  • Southeast has relatively cheap power Risk of dying from coal fired power plant caused particulates Source: Clean Air Task Force http://poweringthesouth.org
  • NC and GA – two of most inefficient energy economies in the U.S. Source: U.S. Department of Energy, Energy Information Administration. 2006
  • World’s 50 largest GHG producers North Carolina 24 th in World World’s largest emitters – 9 of 50 are southeast U.S. states Georgia 22 nd in World Florida 17 th in World Source: Pew Climate Center presentation to NC Climate Change Commission, 2006 Virginia 31 st in World
  • Consider CHP for efficiently using biomass for power production
    • Promote distributed generation using available “opportunity” fuels
    • Utilize waste heat from the natural inefficiency of power generation
    • Strive to reduce carbon emissions to the atmosphere
    • Support the process to establish policies that allow change to occur
  • Efficiency Benefits of CHP
  • Efficiency gains translate to emission reductions
  • NC REPS Definition of Biomass
    • The NCUC decided not to expand the definition of biomass specified in N.C. Gen. Stat. § 62-133.8(a)(8): “agricultural waste, animal waste, wood waste , spent pulping liquors, combustible residues, combustible liquids, combustible gases, energy crops, or landfill methane; or waste heat derived from a renewable energy resource.” Further determination of what constitutes a qualifying biomass resource may be made on a case-by-case basis
  • Wood residues
    • The conversion of woody biomass to energy in the NC poses a unique opportunity to address three issues:
    • Restoration of forest health
    • GHG reduction by using renewable energy alternatives
    • Provide economic development in rural communities
  • Total Biomass Thermal Fuel Value 199x10 12 Btu/yr 6650 Mw t 1662 Mwe
  • There is a significant proportion of the 10% NC REPS available from gleaning logging residues.
  • Biomass harvests can reduce site preparation costs.
  • Biomass markets can make management of poor quality stands profitable by making pre-commercial thinnings into commercial thinnings.
  • Woody Biomass “Practices” There are different opinions Practice Industry Extension Environmentalist Best Management Practices for Water Quality Approve Approve Approve Harvest Notification Dislike any sort of pre or post harvest announcement or opening to government regulation or oversight Supports Written Contract approved by NC Registered Forester to verify that BMPs were followed, documentation to pass up the commercial chain to state regulators. This is sort of a back door to post harvest notification Pre harvest notification Minimum Residual Stand for Thinning, Residue Left at Final Harvest Nope No consensus opinion 30 ft 2 /acre for thinning, 8 live 5” diameter trees/acre no harvest of advanced regeneration, 2 brush piles per acre
  • Do we have some questions? Alex Hobbs NC Solar Center www.ncsc.ncsu.edu
  • EPA CHP technology catalog
    • www.epa.gov/chp/basic/catalog.html
    • Good introduction to power technology options and heat recovery
    • Coverage of several efficiency measurements and where they best apply
  • EPA Biomass Publication
    • CHP applications for low Btu fuels
    • Provides a good review of everything from stoker boilers to gasification for powering renewable CHP
    • www.epa.gov/combdhpp/documents/biomass_chp_catalog.pdf
  • Energy Conversion Technologies Chris Hopkins-NCSU Simple Sugars Energy Products and Processes for Woody Biomass Torrefied Wood Bio-Char Bio-Oil Syngas (CO H 2 CH 4 ) Alcohol, Fischer-Tropsch Liquids Hydrolysis Pyrolitic Conversion Direct Combustion Bio-Fuels & Bio-Products Bio-Power Logging Residue, Waste Wood, Tops & Branches Hot Gas or Steam Process Heat Turbines Electricity or Combined Heat and Power (CHP) Torrefaction 300ºC Pyrolysis 400ºC Gasification 500ºC Acids & Enzymes Alcohols Fermentation & Distillation
  • NC Biomass Council Estimated 277 trillion Btu’s or 81billion kW t hr of biomass resource in NC http://www.engr.ncsu.edu/ncsc/bioenergy/docs/NC_Biomass_Roadmap.pdf
  • Notes on Biomass Availability for the EMC Chris Hopkins Outreach Associate, Forestry Extension
  • Components of Biomass Available for Energy and Fuels in NC
    • Forest harvest residues
    • Pulpwood
    • Agricultural Residues (corn and wheat stover)
    • Hay
    • Biofuels crops (perhaps on pasture land)
  • Current Forest Productivity
    • TPO for NC 2007 data indicate we are generating about
      • 12 million green tons of logging residue and
      • 11.5 million other removals,
      • 25% more than enough to satisfy the 17.6 million tons of forest residue (55% of the RPS total need) from the full implementation of the RPS
  • Prospective Forest Productivity
    • We could approximately increase our harvestable annual yield by a factor of 5.25
        • If all timberland stands were managed on a 50 year rotation and
        • Growth rates matched those of the top 25% of existing hardwood and softwood stands.
  • Pulpwood
    • Most NC pulp mills not currently operating at full capacity
    • Nationally we are using less paper each year (1-2%)
    • NC TPO indicates about
      • 10 million tons of pulpwood produced annually
      • 1.5 million tons of fiber for composite products
  • Agricultural Residues
    • USDA figures from the last ten years indicate:
    • Corn stover and wheat straw are the main sources of potential agricultural residues in NC.
    • Corn stover is about 74% of the agricultural residues (0.659 million BDT) and wheat straw is the bulk of the remainder (0.238 million BDT)
    • Hay is not a residue product, but may be available for use (1.589 million tons)
  • Biofuels on Pasture and Hay Land
    • Hay is typically grown on fallow agricultural land while pastures are usually less productive.
    • Hay represents about 716,000 acres, while pasture is about 3,000,000 acres.
    • Biofuels production such as switchgrass on pasture lands would likely be relatively low compared to typical ranges (4-9 BDT/acre)
    • 4 BDT/acre used in this analysis.
  • Regions for Analysis of the Biopower/Biofuels Resources
    • NCSU is working with the NC Biofuels Center to develop a strategic assessment of the best fit of biomass feedstocks to potential technologies and may use the following regional breakdown for simplified analysis:
  • Requirments for Biofuels and Biopower Production
    • Biopower was assumed to require 8.8 million BDT annually at full RPS implementation or 1.466 million BDT from each region.
    • Biofuels production is proposed to be 600,000,000 gallons annually
      • Assume 80 gallons of fuel per BDT of biomass.
      • 7,500,000 BDT required statewide,
      • 1,250,000 BDT from each region
    • Biopower and Biofuels production is assumed to be equally shared among regions.
  • Constraints and Improvements of Biomass Availability
    • Availability describes participation in biomass markets, assumed to be 90% for all biomass sources in this analysis
    • Recovery is the technical ability to bring available biomass to market
      • 75 % from recent experience with the logging industry
      • 60% from agriculture literature
      • 100% for hay and biofuels crops
    • Yield gain describes increase in production foreseen under improved management scenarios (2 is considered a conservative forestry increase, i.e., 100% increase)
  • Biomass vs. Biofuels and Biopower
    • Red indicates regional biopower goal not met.
    • Yellow indicates biopower goal met, partial fulfillment of biofuels goal.
    • Green indicates both goals met.
    • Numbers in table are cumulative over
      • Logging residue,
      • Other forest residue,
      • Pulpwood ,
      • Agriculture residue
      • Hay
      • Switchgrass
  • Base Case: Current Productivity, Recovery and Availability Logging Residues Other Forest Residues Pulpwood Crop Residue Hay Pasture to Switchgrass Availability 0.9 0.9 0.9 0.9 0.9 0.9 Recovery 0.75 0.75 1 0.6 1 1 Yield Gain 1 1 1 1 1 1 Total 0.675 0.675 0.9 0.54 0.9 0.9 Regions Cumulative Sum of Biomass Sources 1 2 3 4 5 6 Logging Residues 521,996 589,281 801,593 1,124,893 607,084 422,309 Other Forest Residues 1,057,529 1,182,391 1,570,654 2,180,129 1,142,855 804,977 Pulpwood 1,670,130 1,841,674 2,361,622 3,222,692 1,610,893 1,158,497 Crop Residue 1,686,060 1,927,704 2,415,237 3,393,891 1,810,264 1,439,461 Hay 1,923,458 2,470,064 2,695,526 3,551,121 2,014,530 1,448,090 Pasture to Switchgrass 3,778,922 6,604,488 5,353,583 5,104,002 2,085,936 2,041,960
  • Improved Forest Production Scenario with Current Recovery and Availability Logging Residues Other Forest Residues Pulpwood Crop Residue Hay Pasture to Switchgrass Availability 0.9 0.9 0.9 0.9 0.9 0.9 Recovery 0.75 0.75 1 0.6 1 1 Yield Gain 2 2 2 1 1 1 Total 1.35 1.35 1.8 0.54 0.9 0.9 Regions Cumulative Sum of Biomass Sources 1 2 3 4 5 6 Logging Residues 1,043,992 1,178,562 1,603,186 2,249,786 1,214,167 844,617 Other Forest Residues 2,115,059 2,364,782 3,141,308 4,360,258 2,285,711 1,609,955 Pulpwood 3,340,260 3,683,349 4,723,244 6,445,384 3,221,786 2,316,994 Crop Residue 3,356,190 3,769,379 4,776,860 6,616,583 3,421,157 2,597,958 Hay 3,593,588 4,311,739 5,057,148 6,773,813 3,625,423 2,606,587 Pasture to Switchgrass 5,449,052 8,446,163 7,715,205 8,326,694 3,696,830 3,200,457
  • Results
    • Satisfying biofuels and biopower mandates are achievable with modest and achievable increases in forest production alone in most regions.
    • Region 6 is probably too small and isolated to be considered independently.
  • How Achievable is a Doubling of Forest Productivity?
    • CAPAG Forest Management Option
    • Goal: by 2020 double the productivity of 50% of NC timberland for high value products and claim these products and energy as carbon offsets.
    • Enhance funding of the Forest Development Program (NC DENR)
      • ~$230 million for 10 years
      • Discounted cost of about $260/acre in program
    • 10% of the budget reserved for forestry extension
    Chris Hopkins
  • Forest Industry Health
    • Financial motivation for forest landowners is not to produce biomass product,
    • Motivation is to produce a high value solid wood product , biomass is a co-product (so is pulpwood).
    • Forest residue energy relies on health of the solid wood product market