ML083460110

PINGP - License Renewal: Mn Biomass Study 2005

ML083460110
Person / Time
Site:	Prairie Island
Issue date:	02/01/2005
From:	National Renewable Energy Lab, US Dept of Energy (DOE)
To:	Office of Nuclear Reactor Regulation, State of MN, Dept of Commerce
References
Download: ML083460110 (11)

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Minnesota Biomass -

Hydrogen and Electricity Generation Potential A study by the National Renewable Energy Laboratory Golden, Colorado Provided with financial assistance from the U.S. Department of Energy for The Minnesota Department of Commerce and The Minnesota Office of Environmental Assistance February 2005

2 This study was funded though the U.S. Department of Energy Technical Assistance Program.

The Office of Weatherization and Intergovernmental Program (OWIP) of the Department of Energys Energy Efficiency and Renewable Energy (EERE) Office has designated funds to enable state and local officials, working through the DOE Regional Offices, to access DOE National Laboratories experts for assistance in crosscutting renewable energy and energy efficiency policies and programs. This is for short-term assistance in one of four eligible areas:

System benefits charges or other rate-payer funded utility efficiency and renewable

programs, Renewable or efficiency portfolio standards, Use of clean energy technologies to help states and localities address air emissions, or Use of renewable energy on state or local public lands.

These requests are for short-term assistance, with a maximum budget of $5,000 per request.

States can access experts from the National Renewable Energy Laboratory (NREL), Oak Ridge National Laboratory (ORNL) and Lawrence Berkeley National Lab (LBNL).

The National Renewable Energy Laboratory (NREL) is the nation's primary laboratory for renewable energy and energy efficiency R&D. Established in 1974, NREL began operating in 1977 as the Solar Energy Research Institute. It was designated a national laboratory of the U.S.

Department of Energy (DOE) in September 1991 and its name changed to NREL. NRELs mission is to develop renewable energy and energy efficiency technologies and practices, advance related science and engineering, and transfer knowledge and innovations to address the nation's energy and environmental goals. More information on NRELs programs and capabilities can be found at www.nrel.gov.

3 Minnesota Biomass -

Hydrogen and Electricity Generation Potential Today, renewable energy sourcessolar, wind, biomass, and hydroelectric poweraccount for 9.4% of the total electricity generated in the United States. Biomass power is the second largest source of renewable electricity (after hydroelectric power), making up 19% of the total renewable electricity, or 76% of the non-hydro renewable electricity. (EIA, 2004). Most of this biomass power (62%) is produced from wood residues generated by the forestry industry, urban wood waste, and pulp and paper mills.

While this power is largely generated by direct-fired combustion, which operates at about 20% efficiency, the same biomass can also be used in 37% efficient integrated gasification combined cycle (IGCC) technologies. In addition to this more efficient method to produce electricity from biomass, recent advances also provide the means to convert the biomass to hydrogen, which can be used safely as fuel or as a component in products such as ammonia-based fertilizers.

The need to address waste streams and environmental concerns about our current fossil-based energy system have provided new incentives for using biomass to produce energy. Mill residues and other wood residues are used to generate electricity, avoiding landfill disposal costs while generating power for on-site use. Agricultural residues are used as biomass power feedstocks as a waste control strategy and have been encouraged, in part, to reduce the air quality impacts of open-field burning. The pulp and paper industry has been using on-site power systems to recover valuable chemicals from the black liquor and generate steam and electricity for the plant. Landfill and manure methane projects utilize methane that would otherwise be vented or flared, while displacing the need for conventional electricity generation.

Using biomass for energy generation also offers a number of other benefits such as greenhouse gas reduction and air-quality benefits compared to open burning and coal-fired power plants. Additionally, because many biomass feedstocks are concentrated in rural areas, biomass energy facilities can provide rural economic development benefits by creating jobs and tax revenues. Finally, biomass energy offsets fossil fuel consumption and helps to diversify the nations energy supply mix.

As a State, Minnesota is rich in natural resources, a majority of which are in the agricultural and forestry sectors. As a consequence of these resources, significant quantities of residual biomass is available. A study was conducted by the National Renewable Energy Laboratory to determine the total amount of biomass-derived hydrogen and electricity that could be produced in the State of Minnesota from its energy crops and residual biomass. Additionally, the percents of todays gasoline consumption and electricity consumption were calculated, as well as the resulting reductions in greenhouse gas emissions.

Biomass resource estimates from three literature sources were obtained and used to estimate the total quantity of forest residue, mill residue, agricultural residue, energy crops, and urban wood residue. As in many biomass-related studies, the most significant area of uncertainty in this analysis is in the area of resource data inputs. As shown in Table 1, biomass resource quantities were not available for all biomass categories in any of the data sources. Only lignocellulosic (e.g., wood, grasses, agricultural residues) biomass was included in this assessment, although additional biomass in the form of animal excreta, municipal solid waste, and food processing residue may also be used to produce electricity and/or hydrogen. If data on the amounts of these additional waste streams become available, estimates for biomass-based electricity and hydrogen generation potential for the state would be revised upward.

4

1. Biomass Inventory The data from three Minnesota biomass inventories were averaged to determine values for this analysis.

Table 1: Biomass Resources in Minnesota Source of Biomass Biomass Resources from ORNL database1 Biomass Resources from NREL GIS Group Biomass Resource from 1997 ILSR Inventory Average of all biomass resource data tons/year at <$50/ton tons/year tons/year tons/year Forest Residue 874,900 874,900 Mill Residue 1,121,000 1,017,688 571,960 903,549 Agricultural Residue 11,935,896 40,709,527 22,040,438 24,895,287 Energy Crops 5,783,002 5,783,002 Urban Wood Waste 1,532,529 1,532,529 Total 21,247,327 41,727,215 22,612,398 33,989,267 1 ORNL 1999 database: http://bioenergy.ornl.gov/resourcedata/

2NREL GIS database, updated with new sources of data: mill residue data are from the 2002 Timber Products Output Database by the USDA Forest Service; agricultural residue data are from the National Agricultural Statistics Service at USDA (http://www.nass.usda.gov:81/ipedb/)

3ILSR 1997 database:

http://www.carbohydrateeconomy.org/library/admin/uploadedfiles/Survey_of_Minnesotas_Agricultural_

Residues_and.html

2. Hydrogen from Biomass Hydrogen can be produced from lignocellulosic biomass by combining gasification or pyrolysis, with steam reforming and the water-gas shift reaction (CO + H2O => CO2 + H2). The technology to achieve this has been tested in systems equivalent to 10 kg of biomass per hour. Gasification technology has been tested at scales as large as approximately 15,000 kg of biomass per hour.

Biomass typically contains only about 6% (by weight) hydrogen. That leads many people to argue that it doesnt make sense to use biomass to produce hydrogen. However, the carbon in biomass is used as the chemical template for removing oxygen from water in the steam reforming process. By producing some hydrogen from steam in the reforming and water gas-shift reactors, approximately 50% more hydrogen can be produced than by using only the hydrogen in the biomass. If biomass is approximated as having the empirical formula of CH1.4O0.6, the full conversion of biomass to hydrogen can be represented as:

If all of the hydrogen were to come from the biomass, only 1.4 moles of hydrogen would be produced per mole of biomass. Because the carbon in the biomass is used to remove some hydrogen from water in reforming/shift, however, up to 2.1 moles of hydrogen per mole of biomass are possible.

Hydrogen can also be produced from manure using anaerobic digestion followed by reforming and shift.

Biomass-derived sugars, which could be the waste products from food processing facilities (e.g., plants making beet sugar, corn syrup, cheese, cereals or baked goods) or the products of enzymatic breakdown of cellulose, can be converted to hydrogen via fermentation or anaerobic digestion followed by reforming.

2 2

2 6

.0 4.1 1.2 4.1 H

CO O

H O

CH

+

+

5 Finally, low-temperature conversion of glucose to hydrogen is also being researched, but is not currently applicable to whole-biomass (lignocellulosic) streams.

To calculate the amount of hydrogen that could be produced from lignocellulosic biomass in Minnesota, a hydrogen yield of 0.725 kg/kg bone dry biomass (65.8 kg H2/ton bone dry biomass) was assumed (Spath and Mann, 2003). This corresponds to a 50% energy conversion efficiency and an assumption that the biomass has a heating value of 8,500 Btu/lb HHV, dry basis.

The amount of gasoline used in Minnesota in 2000 was approximately 2.5 billion gallons. On a lower heating value basis, the energy content of a gallon of gasoline is approximately equal to the energy content of a kilogram of hydrogen. From these parameters, the amount of gasoline that could be displaced by biomass-derived hydrogen was calculated using the following equation:

Where:

D = percentage of gasoline displaced, gallons/year H2 = amount of hydrogen used in transportation applications, kg/year

= ratio of the efficiency of hydrogen use to gasoline use G = amount of gasoline used in MN in 2000 Based on data from the GREET program http://www.transportation.anl.gov/software/GREET/index.html) at Argonne National Laboratory, the amount of CO2 emitted from gasoline-burning automobiles is equal to 9,100 grams per gallon of gasoline consumed. Since no CO2 is produced by using hydrogen in an internal combustion engine or fuel cell, the direct vehicle CO2 emissions savings are equal to 9,100 grams per gallon of gasoline conserved.

Previous life cycle assessments by the National Renewable Energy Laboratory have shown that the total amount of greenhouse gases (CO2, methane, and N2O) that are produced by converting biomass to hydrogen depend on the type of biomass and the fate of the biomass if it were to have been disposed of rather than used for energy. If the biomass is grown as an energy crop, specifically for the purpose of energy production, the CO2 emitted from the hydrogen facility is balanced by the CO2 consumed by the biomass during its growth cycle. However, the process cannot be considered to be a zero-net emitter because of the fossil fuels used to grow and transport the biomass. Mann and Spath (1997) showed that the net greenhouse gas emissions are approximately 5% of the total carbon in the biomass. However, if the biomass is a residue that would have been sent to a landfill (e.g., urban wood waste), the net greenhouse gas emissions from the system are negative due to the avoidance of methane emissions during normal decomposition. Operations using biomass recovered from forest thinning would have a nearly zero net emissions profile because of the oxidation of nearly all of the carbon on the forest floor, less the carbon that may be stored underground. Emissions avoided by using agricultural residues would depend on how the residue was normally disposed of. Because of the wide variance in avoided greenhouse gas emissions profiles, it was assumed that the production of hydrogen from lignocellulosic biomass in MN would result in very little to zero greenhouse gas emissions.

Table 2 shows the amount of hydrogen that could be produced from the average of the resources identified in the three sources of literature cited in Table 1, assuming that the efficiency of the hydrogen vehicle is equal to the efficiency of todays fleet of gasoline vehicles. The major assumptions used to calculate Tables 2 are shown in the appendix.

100 2

G H

D

=

6 Table 2: Hydrogen Potential Based on Average of Biomass Resource Data and Equal Fuel Efficiency Usage:

(assumes equal efficiency between hydrogen-and gasoline-fueled cars)

Source of Biomass Average of all biomass resource data Hydrogen potential

% of gasoline use that could be met with this H2 Direct CO2 reductions for hydrogen transportation fuel Life-cycle GHG reductions for hydrogen transportation fuel tons/year kg/year tons C02/year tons CO2-equiv/year Forest Residue 874,900 57,543,023 2% 523,797 664,869 Mill Residue 903,549 59,427,318 2% 540,949 686,641 Agricultural Residue 24,895,287 1,637,387,220 65% 14,904,645 18,918,863 Energy Crops 5,783,002 380,353,662 15% 3,462,245 4,394,720 Urban Wood Waste 1,532,529 100,795,922 4% 917,515 1,164,626 Total 33,989,267 2,235,507,144 89% 20,349,151 25,829,720 Table 3 assumes that a future hydrogen fuel cell vehicle is twice as efficient as todays gasoline vehicles.

Also shown in these tables are the amount of gasoline usage that could be displaced with this hydrogen and the accompanying reductions in CO2 and life-cycle greenhouse gas emissions. The major assumptions used to calculate Tables 3 are shown in the appendix.

Table 3: Hydrogen Potential Based on Average of Biomass Resource Data and Double Fuel Efficiency Usage:

(assumes the efficiency of hydrogen-fueled cars is twice that of gasoline-fueled cars)

Source of Biomass Average of all biomass resource data Hydrogen potential

% of gasoline use that could be met with this H2 Direct CO2 reductions for hydrogen transportation fuel Life-cycle GHG reductions for hydrogen transportation fuel tons/year kg/year tons C02/year tons CO2-equiv/year Forest Residue 874,900 57,543,023 5% 1,047,594 1,329,739 Mill Residue 903,549 59,427,318 5%

1,081,898 1,373,282 Agricultural Residue 24,895,287 1,637,387,220 130% 29,809,289 37,837,726 Energy Crops 5,783,002 380,353,662 30% 6,924,491 8,789,441 Urban Wood Waste 1,532,529 100,795,922 8% 1,835,030 2,329,253 Total 33,989,267 2,235,507,144 177% 40,698,302 51,659,440

3. Electricity from Biomass Two important technologies for converting lignocellulosic biomass to electricity are direct combustion and integrated gasification/combined cycle (IGCC). Technical information on how these technologies work can be found at NRELs Biopower web site: http://www.nrel.gov/clean_energy/biopower.html.

Most of the biopower plants in the world use direct-fired systems. They burn bioenergy feedstocks directly to produce steam. This steam is usually captured by a turbine, and a generator then converts it into electricity. Gasification systems use high temperatures and an oxygen-starved environment to convert biomass into a gas (a mixture of hydrogen, carbon monoxide, and methane). The gas fuels what's called a gas turbine, which is very much like a jet engine, only it turns an electric generator instead of propelling a jet. For the calculations presented here, conversion efficiencies of 1.41 and 1.76 MWh/ton of

7 bone dry biomass were assumed for the direct-fired and IGCC cases, respectively. The other major assumptions used to calculate power potential are shown in the appendix. Table 4 shows electricity generation potential and greenhouse gas savings that could result by using the average amount of biomass in Minnesota in direct-fired power plants.

Table 4: Power Potential from the Use of Direct-Fired Biomass Power Plants in MN (Based on Average of Biomass Resource Data)

Source of Biomass Electricity potential

% of MN electricity use that could be met with biomass power Equivalent capacity Direct CO2 reductions for this biomass power Life-cycle GHG reductions for biomass power MWh/year MW tons CO2/year tons CO2-equiv/year Forest Residue 1,233,609 2% 176 935,138 965,030 Mill Residue 1,274,005 2% 182 965,760 996,631 Agricultural Residue 35,102,355 58% 5,009 26,609,365 27,459,935 Energy Crops 8,154,033 14% 1,164 6,181,170 6,378,752 Urban Wood Waste 2,160,866 4% 308 1,638,046 1,690,406 Total 47,924,867 80% 6,839 36,329,479 37,490,754 Table 5 shows electricity generation potential and greenhouse gas savings that could result by using the average amount of biomass in Minnesota in for IGCC plants.

Table 5: Power Potential from the use of Biomass IGCC in MN (Based on Average of Biomass Resource Data)

Source of Biomass Electricity potential

% of MN electricity use that could be met with biomass power Equivalent capacity Direct CO2 reductions for this biomass power Life-cycle GHG reductions for biomass power MWh/year MW tons CO2/year tons CO2-equiv/year Forest Residue 1,539,824 3% 220 1,167,265 1,204,576 Mill Residue 1,590,247 3% 227 1,205,488 1,244,021 Agricultural Residue 43,815,705 73% 6,252 33,214,526 34,276,231 Energy Crops 10,178,084 17% 1,452 7,715,503 7,962,130 Urban Wood Waste 2,697,251 4% 385 2,044,653 2,110,011 Total 59,821,110 99% 8,536 45,347,435 46,796,969

4. Generic Results Due to Resource Uncertainty Because of the large variability in biomass resource data, calculations of the hydrogen and electricity potential were also carried out for functional amounts of biomass. Tables 6 and 7 show hydrogen results parallel to those shown above. Tables 8 and 9 show electricity results. It is important to note that the impact of using biomass to produce hydrogen for the transportation sector or power for the electric sector is directly related to how much biomass is available. To displace just 3% of gasoline use in Minnesota, at least one-million tons per year of biomass will be required for hydrogen production and use in vehicles

8 that match todays internal combustion engine efficiencies. Two-percent of the traditional power generation in Minnesota can be replaced with this much biomass used in direct-fired power plants.

Greater displacements of both gasoline and power can be achieved by using more efficient conversion systems such as fuel cells and IGCC power plants.

Table 6: Hydrogen Results Based on Functional Amounts of Biomass Resources (assumes equal efficiency between hydrogen-and gasoline-fueled cars)

Biomass resource base Hydrogen potential

% of gasoline use that could be met with this H2 Direct CO2 reductions for hydrogen transportation fuel Life-cycle GHG reductions for hydrogen transportation fuel tons/year kg/year tons C02/year tons CO2-equiv/year 1

66 0% 1 1 100 6,577 0% 65 83 1,000 65,771 0% 651 826 100,000 6,577,097 0% 65,094 82,593 1,000,000 65,770,972 3% 650,935 825,934 10,000,000 657,709,719 26% 6,509,351 8,259,340 Table 7: Hydrogen Results Based on Functional Amounts of Biomass Resources (assumes the efficiency of hydrogen-fueled cars is twice that of gasoline-fueled cars)

Biomass resource base Hydrogen potential

% of gasoline use that could be met with this H2 Direct CO2 reductions for hydrogen transportation fuel Life-cycle GHG reductions for hydrogen transportation fuel tons/year kg/year tons C02/year tons CO2-equiv/year 1

66 0% 1 2 100 6,577 0% 130 165 1,000 65,771 0% 1,302 1,652 100,000 6,577,097 1% 130,187 165,187 1,000,000 65,770,972 5% 1,301,870 1,651,868 10,000,000 657,709,719 52% 13,018,703 16,518,680 Table 8: Electricity Results Based on Functional Amounts of Biomass Resources used in Direct-fired Biomass Power Plants Biomass resource base Electricity potential

% of MN electricity use that could be met with biomass power Equivalent capacity Direct CO2 reductions for this biomass power Life-cycle GHG reductions for biomass power tons/year MWh/year MW tons CO2/year tons CO2-equiv/year 1

1 0% 0 1 1

100 141 0% 0 107 110 1,000 1,410 0% 0 1,069 1,103 100,000 141,000 0% 20 106,885 110,302 1,000,000 1,410,000 2% 201 1,068,852 1,103,017 10,000,000 14,100,000 23% 2,012 10,688,515 11,030,174

9 Table 9: Electricity Results Based on Functional Amounts of Biomass Resources used in IGCC Power Plants Biomass resource base Electricity potential

% of MN electricity use that could be met with biomass power Equivalent capacity Direct CO2 reductions for this biomass power Life-cycle GHG reductions for biomass power tons/year MWh/year MW tons CO2/year tons CO2-equiv/year 1

2 0% 0 1 1

100 176 0%

0 133 138 1,000 1,760 0% 0 1,334 1,377 100,000 176,000 0% 25 133,417 137,682 1,000,000 1,760,000 3% 251 1,334,169 1,376,816 10,000,000 17,600,000 29% 2,511 13,341,692 13,768,161

5. Summary The analysis projects that there is enough residual biomass and energy crops in the State that, if collected and fed to the most efficient conversion technologies available, it could produce up to 99% of the total electricity currently used in Minnesota. Exclusively using agriculture residue has the potential to produce up to73% of the electricity currently used.

In regard to hydrogen, the analysis projects that there is enough residual biomass and energy crops in the state, that if collected and fed to the most efficient conversion technologies available (assuming equal fuel efficiency) that the hydrogen produced could replace up to 89% of the total gasoline currently used in Minnesota. Exclusively using agriculture residue could replace 65% of the gasoline currently used.

However, this potential cannot be realized unless economically viable collection, hauling, energy conversion and energy distribution systems are in place. There is substantial research and increasing numbers of demonstration projects occurring nationally to determine which system components are most functional and cost effective for given locations. Results of the data analysis performed for this report provides convincing evidence that Minnesota should further participate in such research and demonstration projects. This course of action would help ensure that the state maximizes value while benefiting from its significant renewable biomass resources.

6. References Energy Information Administration (July 2004). Renewable Energy Trends 2003 with Preliminary Data for 2003. Table C-3, p 24. http://www.eia.doe.gov/cneaf/solar.renewables/page/rea_data/rea.pdf Mann, M.K., Spath, P.L. (1997). Life Cycle Assessment of a Biomass Gasification Combined-Cycle System. NREL/TP-430-23076. National Renewable Energy Laboratory. Golden, CO.

Spath, P.L., Mann, M.K., Amos, W.A. (2003). Update of Hydrogen from Biomass - Determination of the Delivered Cost of Hydrogen. National Renewable Energy Laboratory. Golden, CO.

http://www.nrel.gov/docs/fy04osti/33112.pdf

10 Appendix: Calculations and Assumptions Hydrogen Calculations & Assumptions (assuming equal efficiency)

Hydrogen yield (kg/kg BDW) 0.0725 Source: Spath and Mann, 2000 Hydrogen yield (kg/ton BDW) 65.8 Gallons of gasoline consumed in 2000 in MN 2,523,108,000 Ratio of the efficiency of hydrogen use to gasoline use 1

GHG emissions from gasoline combustion in today's ICE (g/mile) (not LCA) 400.83 Source: GREET Mileage on car (miles/gallon) 22.4 Assumption in GREET GHG emissions from gasoline combustion in today's ICE (g/gallon gasoline) (not LCA) 8,978.56 Direct g CO2-equiv/kg H2 offset 8,978.56 Direct tons CO2-equiv/kg H2 offset 0.0099 Life-cycle GHG emissions from gasoline combustion in today's ICE (g/mile) 508.59 Source: GREET Life-cycle GHG emissions from gasoline combustion in today's ICE (g/gallon) 11,392.37 Life-cycle g CO2-equiv/kg H2 offset 11,392.37 Source: GREET Life-cycle tons CO2-equiv/kg H2 offset 0.0126 Hydrogen Calculations & Assumptions (assuming double efficiency)

Hydrogen yield (kg/kg BDW) 0.0725 Source: Spath and Mann, 2000 Hydrogen yield (kg/ton BDW) 65.8 Gallons of gasoline consumed in 2000 in MN 2,523,108,000 Ratio of the efficiency of hydrogen use to gasoline use 2

GHG emissions from gasoline combustion in today's ICE (g/mile) (not LCA) 400.83 Source: GREET Mileage on car (miles/gallon) 22.4 Assumption in GREET GHG emissions from gasoline combustion in today's ICE (g/ gallon gasoline) (not LCA) 8,978.56 Direct g CO2-equiv/kg H2 offset 17,957.11 Direct tons CO2-equiv/kg H2 offset 0.0198 Life-cycle GHG emissions from gasoline combustion in today's ICE (g/mile) 508.59 Source: GREET Life-cycle GHG emissions from gasoline combustion in today's ICE (g/gallon) 11,392.37 Life-cycle g CO2-equiv/kg H2 offset 22,784.74 Source: GREET Life-cycle tons CO2-equiv/kg H2 offset 0.0251

11 Power Calculations & Assumptions (direct-fired plant)

IGCC or Direct Combustion?

Direct Specify "IGCC" or "Direct" Electricity yield (MWh/ton BDW) 1.41 IGCC assumes a 37% HHV efficiency; Direct assumes a 27.7% HHV efficiency Assumed power plant capacity factor 80%

MWh of electricity consumed in MN in 2002 60,169,575 Source: EIA, State Electricity Profiles, 2002 Direct emissions, g CO2/kWh offset 687.7 Net generation in MN, MWh 52,777,966 Source: EIA, State Electricity Profiles, 2002 CO2 emissions from electricity in MN, thousand short tons 40,009 Source: EIA, State Electricity Profiles, 2002 Direct emissions, tons CO2/MWh offset 0.76 LC emissions, g CO2-equiv/kWh offset 709.7 LC emissions, tons CO2-equiv/MWh offset 0.78 Power Calculations & Assumptions (IGCC plant)

IGCC or Direct Combustion?

IGCC Specify "IGCC" or "Direct" Electricity yield (MWh/ton BDW) 1.76 IGCC assumes a 37% HHV efficiency; Direct assumes a 27.7% HHV efficiency Assumed power plant capacity factor 80%

MWh of electricity consumed in MN in 2002 60,169,575 Source: EIA, State Electricity Profiles, 2002 Direct emissions, g CO2/kWh offset 687.7 Net generation in MN, MWh 52,777,966 Source: EIA, State Electricity Profiles, 2002 CO2 emissions from electricity in MN, thousand short tons 40,009 Source: EIA, State Electricity Profiles, 2002 Direct emissions, tons CO2/MWh offset 0.76 LC emissions, g CO2-equiv/kWh offset LC emissions, tons CO2-equiv/MWh offset Emissions from NREL LCA Studies g/kWh, LCA

% in use in MN Coal 1022 52%

NGCC 499 18%

Oil-fired 1022 9%