FURNACES FOR HEATING AND WOOD BURNING POWER PLANTS

Vermonters use low sulfur No.2 fuel oil, propane, natural gas and wood for space and domestic hot water heating. Such heating contributes about 28% of total Vermont emissions of about 10 million metric ton in 2015 (latest numbers!).

 

No.2 fuel oil and propane are about 75% of heating emissions, pipeline and compressed natural gas about 22% and wood about 3%.

 

FURNACE EFFICIENCIES

 

The standard efficiency rating for residential heating systems is AFUE or Annual Fuel Utilization Efficiency, which is used with natural gas, propane and fuel oil systems. This is the annual average efficiency, which is less than the instantaneous efficiency.

 

New gas, propane or fuel oil furnaces typically have efficiencies between 78% and 96% AFUE, and generally fall into one of three categories.

 

1) Minimum-efficiency furnaces typically have an AFUE of 78-80% (compared with 60-70% for an older furnace). The increase in efficiency is mainly due to a combination of better heat exchangers, electronic ignition (to replace a standing pilot), and internal vent dampers to reduce off-cycle losses via the exhaust flue. In milder climates, this type may be the most cost-effective option.

 

2) Medium-efficiency furnaces have slightly higher efficiencies, up to 83% AFUE for gas or propane, and up to 87% for fuel oil. These systems use even more efficient heat exchangers and have more precise control of combustion air and venting. Medium-efficiency fuel oil furnaces typically incorporate new "high-static" burners that extract more heat from the fuel. 

 

3) High-efficiency gas or propane condensing furnaces have AFUEs of 90-96%. See note. These furnaces use a second heat exchanger to reclaim some of the heat lost in the form of water vapor. The water vapor in the exhaust is condensed, releasing additional useable heat, and lowering the exhaust temperature to enable venting to the outdoors via a short plastic pipe. Although this type of system is more expensive, it is often the most cost-effective option in cold climates, especially in energy-hog buildings with high heating requirements.

NOTE: The condensing furnaces require the water circulating through the heat exchangers of the house to be at about 140F or less to achieve those high efficiencies. That means all or part of the typical baseboard heaters would need to be replaced, because they require at least 175F circulating water.

 

Electrical Efficiency: In addition to the furnace's AFUE, you should also consider the system's electrical efficiency. Furnaces can use a significant amount of electricity, mainly to power the fan motor. Look for a system with a high electrical efficiency. Multi-speed or variable speed fan motors and circulating pumps, and continuously varying the furnace gas/propane input, are usually more efficient than single-speed motors and old-fashioned, wasteful on/off operation.

https://www.energydepot.com/RPUres/library/homeheating.asp

 

COMPARISON OF CO2 OF VARIOUS HEATING FURNACES  

 

The AFUEs of various furnaces and CO2 per million Btu of delivered heat are shown on table 2.

Wood has 2.53 times the CO2 emissions/kWh of natural gas

Wood toxic pollutants/kWh are about 1.67 times than of hard coal, because 1) coal combustion has slightly less lb CO2/million Btu and 2) coal power plants are much more efficient than wood power plants. See URLs.

http://www.windtaskforce.org/profiles/blogs/is-burning-wood-co-2-ne... 

https://www.eia.gov/tools/faqs/faq.php?id=73&t=11

The combustion CO2 of the first year of plant operation would be absorbed according to an S-curve over about 40 years; slowly increasing during the first 1/3, rapidly increasing during the second 1/3, and slowly increasing during the last 1/3 of the period; not much help if the world’s climate is to be prevented from falling off the cliff during the next 20 to 30 years.

 

NOTE: 40 years is a US average; 80 - 100 years in northern climates, such as northern Vermont; 40 - 50 years in moderate climates, such as North Carolina, 25 years between harvests on planted, fertilized, and culled forests of fast-growing pines in Georgia. 

https://www.pfpi.net/wp-content/uploads/2011/04/PFPI-biomass-carbon...

 

NOTE: Any other CO2 associated with the A to Z chain (from embodied CO2, and CO2 due to managing wood lots, harvesting, O&M of the plant, and plant decommissioning) would never be absorbed, unless additional forest is set aside.

Inefficient heating systems should be banned within a certain time period.

High-efficiency propane and natural gas condensing furnaces should be promoted with incentives and new gas lines, etc.

High-efficiency wood stoves should be promoted with incentives.

HEAT PUMPS

 

The NE grid had emissions of 710 lb CO2/MWh in 2016, fed to grid. See note and URL

To have 1 million Btu of electricity at the user meter, about 1 million Btu x 1.075 needs to be fed by power plants to the NE grid to account for transmission and distribution losses.

CO2/million Btu of electricity at user meter = (710/ lb CO2/MWh) x (1000000 Btu/3412 Btu/kWh) x (1 MWh/1000 kWh) x 1.075, T&D = 224 lb. See table 1.

Heat pump winter average COP is about 2.2

CO2/million Btu at user meter (for a heat pump) would be about 224/2.2 = 102 lb, i.e., only slightly better than natural gas used with condensing furnace. See table 1 

https://www.iso-ne.com/static-assets/documents/2018/01/2016_emissio...

 

NOTE:

- An old wood stove has 3 times the CO2 emissions of a high-efficiency condensing gas furnace. Remember, these emissions take about 100 years to be reabsorbed in colder climates.

- A high-efficiency, condensing gas furnace has 1.2 times the CO2 emissions of a heat pump. Remember, that ratio increases as the NE grid becomes “cleaner” during future years.

 

NOTE:

Electricity Mix Based on Power Purchase Agreements: There are non-technical people talking about the “Vermont electricity mix” or the “New Hampshire electricity mix”. That mix exists only on paper, because it is based on power purchase agreements, PPAs, between utilities and owners of electricity generators. A utility may claim it is 100% renewable. This means the utility has PPAs with owners of renewable generators, i.e. wind, solar, biomass, hydro, etc. That mix has nothing to do with physical reality.

 

Electricity Mix Based on Physical Reality: Once electricity is fed into the NE electric grid by any generator, it travels:

 

- On un-insulated wires, as electromagnetic waves, EM, at somewhat less than the speed of light, i.e. from northern Maine to southern Florida, about 1800 miles in 0.01 of a second, per College Physics 101.

- On insulated wires, the speed decreases to as low as 2/3 the speed of light, depending on the application.

 

If those speeds were not that high, the NE electric grid would not work, and modern electronics would not work.

 

The electrons vibrate at 60 cycles per second, 60 Hz, and travel at less than 0.1 inch/second; the reason it takes so long to charge a battery.

 

It is unfortunate most high school teachers told students the electrons were traveling.

Teachers likely never told them about EM waves, or did not know it themselves.

http://www.djtelectricaltraining.co.uk/downloads/50Hz-Frequency.pdf

 

This article explains in detail what happens when electricity is fed to the grid.

http://www.windtaskforce.org/profiles/blogs/popular-misconceptions-...

 

NOTE: If you live off the grid, have your own PV system, batteries, and generator for shortages and emergencies, then you can say I use my own electricity mix. If you are connected to the GMP grid, which is connected to the NE grid, and draw from any socket, then you draw the NE mix.

 

Table 1	CO2	Eff	Heat output	CO2	Ratio
Furnace type	lb/MBtu	%	Btu/MBtu	lb/MBtu
Wood, old	213	70	700000	304	3.0
Wood, new	213	80	800000	266	2.6
No. 2 fuel oil, old	161	70	700000	230	2.3
No. 2 fuel oil; new	161	80	800000	201	2.0
Propane, old	139	80	800000	174	1.7
Propane new, condensing	139	96	960000	145	1.4
Natural gas, old	117	80	800000	146	1.4
Natural gas, condensing	117	96	960000	122	1.2
		Winter COP
Heat pump	224	2.2	2200000	102	1.0

 

MBtu = 1000000 Btu

 

WOOD FURNACES

 

These URLs has much information regarding wood moisture and wood burning.

 

https://is.muni.cz/el/1423/podzim2013/MEB423/um/Wood_Lesson_02.pdf

https://mha-net.org/docs/v8n2/docs/WDBASICS.pdf

 

In Table 1A are examples of wood furnaces using various fuels.

Wood burning immediately releases 213 lb of CO2 per million Btu of DRY wood, but that CO2 gets absorbed by new biomass growth over about 100 years in colder climates, such as Vermont, about 50 years in milder climates, such as North Carolina.

 

The heat content of wood pellets was assumed at 16.0 million Btu/ton of fuel, wet; depending on the moisture content and the quality of the sawdust

 

The heat content of air-dried firewood, a mixture of hardwoods, 20% water, was assumed at 14.3 million Btu/ton of fuel, wet

 

The heat content of wood chips was assumed at 7.6 million Btu/ton of fuel, wet, because wood chips usually contain a mixture of low-quality branches, leaves and the tops of trees, which have lower heat content than trunk wood of hardwood trees. See table 2

 

Sample Calculations:

 

- Heat content of dry wood pellets = 8000 Btu/lb of fuel, wet x 1/0.926, wood fraction = 8640 Btu/lb, dry

- Heat to house = 8640 Btu/ lb of fuel, dry x 0.80, eff. = 6912 Btu/lb of fuel, dry    

- CO2 of 1 ton of wood pellets = 213 lb/1000000 Btu of wood pellets, dry x 2000 lb/ton x 8640 Btu/lb of wood pellets, dry x 1/1000000 = 3681 lb

 

Table 2/Wood furnaces	Wood	Firewood	Woodchips
	Pellets	Air dried	As delivered
Moisture content, mc we basis	8	20	45
Wood fraction = 1/(1 + 8/100)	0.926	0.833	0.690
Water fraction = 1 - wood fraction	0.074	0.167	0.310
Total weight, wet	1.000	1.000	1.000
Heat content, Btu/lb, dry = 8000/0.926	8640	8400	5510
Heat to furnace, Btu/lb, wet	8000	7000	3800
Fuel, 1 ton = 2000 lb	2000	2000	2000
Heat to furnace, Btu/ton, wet	16000000	14000000	7600000
Heat of evaporation, 60F - 212F, Btu/lb	1058	1058	1058
Evaporation loss, Btu/lb = 1058 x 0.074	78	176	328
Conversion loss, Btu/lb = 8640 - 6912 - 78	1806	1856	1981
Furnace efficiency, %	80	80	70
Heat to house, Btu/lb, dry = 8640 x 0.8	6912	6720	3857
.
CO2, lb/million Btu, dry	213	213	213
CO2, lb/ton, dry	3681	3578	2347

 

COMPARISON OF CO2/kWh OF VARIOUS POWER PLANTS

 

The Vermont McNeal and Ryegate wood-chip power plants have CO2 emissions/MWh about 4 times greater than a gas-fired combined-cycle gas turbine, CCGT, power plant.

 

The other pollutants of wood per MWh, including particulates, are about 4/2.4 = 1.67 greater than of coal.

https://www.eia.gov/tools/faqs/faq.php?id=73&t=11

 

Sample calculation for natural gas: 3412000 Btu/MWh/0.55, eff. x 117 lb CO2/1000000 Btu = 727 lb CO2/MWh.

 

A standard ton of green wood is 45% water, and dry wood is 50% carbon. Burning one US ton of green woodcreates 2000 x (1- 0.45) x 0.5 x (44/12)/2000 = 1.00833 US ton of CO2 emissions.

 

It takes about 50 years in moderate climates (North Carolina) to about 100 years in colder climates (Vermont) for the combustion CO2 of wood burning to be naturally reabsorbed.

 

The absorption has the shape of an S-curve, i.e., slowly increasing during the first 1/3, rapidly increasing during the second 1/3, and slowly increasing during the last 1/3 of the period; not much help if the world’s climate is to be prevented from falling off the cliff during the next 20 to 30 years.

 

NOTE: Any other CO2 associated with the A to Z chain (from embodied CO2, and CO2 due to managing wood lots, harvesting, O&M of the plant, and plant decommissioning) would never be absorbed, unless additional forest is set aside.

 

Natural gas CCGTs should be promoted with new gas lines, etc.

Wood burning power plants should be deemphasized.

 

Table 2A/Fuel	lb CO2/million Btu	Plant efficiency, %	lb CO2/MWh	CO2 Ratio
Wood chip; McNeal/Ryegate*	213	25	2907	4.0
Wood chip; Denmark	213	30	2423	3.3
Hard coal	206	41	1712	2.4
No. 2 fuel oil	161	35	1572	2.2
Natural gas, CCGT*	117	55	726	1.0

 *

Plus upstream CO2 (logging, chipping, transport, etc.) of about 5 to 10 %, if burning wood chips

Plus upstream CO2 (logging, chipping/pelletizing, transport, etc.) of about 10 to 15 %, if burning wood pellets

CCGT = Combined-cycle, gas turbine plant

 

McNeal/Ryegate Wood Burning Power Plants

 

Below are listed the wood tonnage and combustion CO2 tonnage of Vermont’s wood chip burning power plants in 2015. The CO2 emissions of these two plants are about 7.3% of Vermont's total annual emissions.

 

Table 3/Vermont Wood Power Plants		McNeil	Ryegate	Total
Green ton = 2000 lb		ton	ton	ton
Electrical, wood	2015, McNeil	469,190.0	249,843	719,033
Electrical, wood CO2	EPA, McNeil	473,100.4	251,925	725,025

 

http://www.maforests.org/McNeil Emissions 2015.pdf

http://www.maforests.org/RYEGATE TECHNICAL.pdf

http://fpr.vermont.gov/sites/fpr/files/About_the_Department/Library... 

http://fpr.vermont.gov/sites/fpr/files/Forest_and_Forestry/Forest_B...

http://www.maforests.org/VermontBiomassBiomess.pdf

 

ELECTRICITY COST OF WOOD AND GAS

 

The cost of generating electricity with a 25%-efficient wood power plant is about 9.5 c/kWh. It is a very wasteful way to burn wood; the heat of three out of four trees goes up the chimney! 

 

In Vermont, the entire output of the Ryegate plant is sold at 10 c/kWh under the Vermont Standard Offer Program, which provides the owners of Ryegate with a good profit.

 

The cost of generating electricity with a 55%-efficient CCGT plant is about 3412/0.55 x 3/1000000 = 1.86 c/kWh for gas + 2 c/kWh for other variable and fixed costs = 3.86 c/kWh, at $3 million Btu, plus the CO2/kWh is about 1/4 of wood. The electricity is sold at an annual average price of about 5 c/kWh. See table 2

 

NOTE: 

- Natural gas is a low-cost, low-CO2 competitor of high-cost, variable, intermittent wind, solar, etc., and thus RE entities oppose new gas lines.

- Hydro-Quebec is a low-cost, near-CO2-free competitor of high-cost variable, intermittent wind, solar, etc., and thus RE entities oppose transmission lines for more electricity from H-Q.

- Vermont Yankee was a low-cost, near-CO2-free competitor of high-cost, variable, intermittent wind and solar, etc., and thus RE entities opposed VY until they succeeded in hounding VY out of business.

 

APPENDIX 1

Obstruction Against New Gas Lines:It may be good political optics for legislators, but it is not good economics and CO2 policy to restrict the use of domestic, low-cost, clean-burning, natural gas and propane in Vermont and New England.

http://www.windtaskforce.org/profiles/blogs/synapse-study-of-new-en...;

 

The governors of New York and Massachusetts have been unwisely opposing the installation of new gas lines to bring more Pennsylvania gas to NY and NE.

 

Their opposition may satisfy the wishes of RE entities, but would merely place another, unnecessary burden on already struggling Vermonters trying to eke out a living in Vermont’s near-zero, real-growth economy. 

 

APPENDIX 2

Heat Pumps in Energy-Hog Buildings are a Folly: The below heat pump articles show at least 80% of all Vermont houses and other buildings are energy hogs and thus unsuitable for heat pumps, because heat pumps would displace, on average, only about 34% of fuel oil, with the other 66% supplied by the traditional systems. 

 

According to the VT-DPS survey of about 140 existing installations, the average energy savings were about $200/heat pump/y. 

That is much less than the $850 to $1800 per year savings estimated by VPIRG and Efficiency Vermont

Many hundreds of owners of energy-hog houses were talked into buying heat pumps

GMP and the EV-approved installers made tons of money, almost everyone else with energy-hog houses was left holding the empty bag.

 

The turnkey capital cost is about $5000 per heat pump, which lasts about 15 years. Amortizing at 5%/y for 15 years requires annual payments of $474/y, plus there are costs for maintenance contracts and service calls. 

 

Only about 1% of Vermont buildings is highly insulated/highly sealed, say 17,000 Btu/h at -20F for a 2000 sq ft house. Heat pumps would displace 100% of the fuel oil for such a house.

 

Please read these articles to be up to speed on the efficacy of heat pumps in New England.

 

http://www.windtaskforce.org/profiles/blogs/fact-checking-regarding...

http://www.windtaskforce.org/profiles/blogs/vermont-baseless-claims...

 

APPENDIX 3

Hydro-Quebec Electricity Generation and Purchases: Google this URL for the 2017 facts. The H-Q electricity supply is an order of magnitude cleaner than the Vermont supply.
http://www.hydroquebec.com/sustainable-development/energy-environme...

 

Table 4/H-Q	2017
	GWh
Hydropower generated	177091
Purchased	44006
- Hydro	31610
- Wind	9634
- Biomass and waste reclamation	2021
- Other	741
Total RE generated and purchased	221097

 

NOTE:Gentilly-2 nuclear generating station, plus three thermal generating stations (Tracy, La Citière and Cadillac) were shut down.

 

Hydro-Quebec Export Electricity: H-Q net exports were 34.4 TWh/y in 2017; provided 27% of H-Q net income, or $780 million, i.e., very profitable.

 

H-Q export revenue was $1,651 million in 2017, or 1641/34.4 = 4.8 c/kWh.

See page 24 of Annual Report URL.

This is for a mix of old and new contracts.

Revenue = 1641

Net profit = 780

Cost = 1641 - 780 = 861

Average cost of H-Q generation = 861/34.4 = 2.5 c/kWh

 

GMP buys H-Q electricity, at the Vermont border, for 5.549 c/kWh, under a recent contract. GMP buys at 5.549 c/kWh, per GMP spreadsheet titled “GMP Test Year Power Supply Costs filed as VPSB Docket No: Attachment D, Schedule 2, April 14, 2017”.

H-Q is eager to sell more of its surplus electricity to New England and New York.

 

That is at least 50% less than ridgeline wind and large-scale field-mounted solar, which are heavily subsidized to make their electricity appear to be less costly than reality. 

 

GMP sells to me at 19 c/kWh, per rate schedule. Consumers pricing for electricity is highly political. That is implemented by rate setting, taxes, fees, surcharges, etc., mostly on household electric bills, as in Denmark and Germany, etc. The rate setting is influenced by protecting “RE policy objectives”, which include highly subsidized, expensive microgrids, islanding, batteries and net metered solar and heat pumps.

 

http://www.hydroquebec.com/sustainable-development/energy-environme...

http://news.hydroquebec.com/en/press-releases/1338/annual-report-2917/

http://www.hydroquebec.com/data/documents-donnees/pdf/annual-report...

http://www.windtaskforce.org/profiles/blogs/green-mountain-power-co...

http://www.windtaskforce.org/profiles/blogs/increased-canadian-hydr...

 

APPENDIX 4

A price of a ton of coal is about $115, retail.

A green cord of wood, 45% water, weighs about 2.5 ton,

A price of a cord of wood is about $115/ton x 2.5 ton = $287.5, about the same as a similar quantity of coal

A ton of green wood has about 7.6 million Btu

A cord of green wood has about 7.6 x 2.5 = 19 million Btu

 

In 2017, the annual average heat content of coal produced in the United States was about 19.78 million Btu per short ton (2,000 pounds), and the annual average heat content of coal consumed was 19.46 million Btu per short ton. 

https://www.eia.gov/tools/faqs/faq.php?id=72&t=2

 

By 1800, most of west Europe was seriously deforested near urban areas. 

It became more and more of an effort to travel long distances with horse-drawn carriages to get to wood, harvest it, and distribute it to users.

Please read this URL

http://www.windtaskforce.org/profiles/blogs/the-importance-of-100-y... 

APPENDIX 5

The Net Heat Content of Wood and Efficiency of Heating Plant; loss method

Information extracted from this URL

https://mha-net.org/docs/v8n2/docs/WDBASICS.pdf

 

1) Heat Loss due to Water Vapor Produced by Burning Hydrogen

 

H2 + ½ O2----H2O

2 lb H2 + 16 lb O2----18 lb H2O

Carbon in 100 lb of dry wood is 49 lb

Hydrogen in 100 lb of dry wood is 6 lb

0.06 lb H2 + 0.48 lb O2 = 0.54 lb H2O

Heat of vaporization is 1058.2 Btu/lb water

Evaporation loss = 0.54 x 1058.2 = 570 Btu/lb

Gross heating value is 8600 Btu/lb of dry wood, also called Higher Heating Value, HHV

Net Heating value = 8600 - 570 = 8030 Btu/lb dry wood, also called Lower Heating Value, LHV

 

2) Heat Loss due to Moisture Content

 

Moisture content, mc, dry weight basis

mc dry basis, % = (Weight wet - Weight dry)/Weight dry x 100

mc dry basis, % = (115 w - 100 d)/100 d x 100 = 15%

 

Moisture content, mc, wet weight basis

mc wet basis = (Weight wet - Weight dry)/Weight wet x 100

mc wet basis = (115 w - 100 d)/115 w x 100 = 13%

 

or

Wood, dry = (1 - 0.15) x 100 lb = 85 lb; water is 100 - 85 = 15 lb

Wood, wet = 1/(1 + 0.15) x 100 lb = 87 lb, water is 100 - 87 = 13 lb

 

See equilibrium moisture content graph and table in URL

At 80% humidity, mc is 15%

Assume wood chips are pre-dried with heat from flue gases to 15% m. c.

Heat available = 0.85 x 8030 = 6845 Btu lb, as fed to boiler

 

NOTE: If 1000 lb of grain is harvested at 25% MC, and dried to 14% MC, what is the final weight of the drier grain?

Final weight of grain = 1000* (100 - 25)/(100 - 14) = 872 lb of grain at 14 % MC

 

3) Heat Loss due Excess Combustion Air, assumed at 30%

 

1 lb C requires 11.52 lb of air, or 0.49 lb C requires 5.65 lb of air

1 lb of H2 requires 34.56 lb of air, or 0.06 lb of H2 requires 2.07 lb of air

1 lb of wood requires 5.65 + 2.07 = 7.72 lb of air

Excess air is 0.3 x 7.72 = 2.32 lb

Temp difference = 270F, stack - 70F, room = 200F

Air specific heat is 0.24 Btu/lb

Heat loss due to excess air is 2.32 x 0.24 x 200 F = 111 Btu/lb of wood. See note

Boiler/ductwork air in leakage assumed at 34 Btu/lb of wood

Total loss = 145 Btu/lb of wood

 

NOTE: If excess air were 100%, loss would be 370 Btu/lb of wood.

 

Table 5 shows the four major losses.

 

Heat Content of Wood	Btu/lb, dry
Theoretical, but essentially impossible total, see URL	10,800
Generally accepted Gross Heating Value, dry wood	8600
Losses
1) Reduced due to water vapor produced by burning hydrogen, Net Heating Value, dry wood	8030
2) Reduced due to moisture content - see table in URL and make your choice, in this case	6845
3) Excess air - see discussion and make your choice	6700
4) Other losses
Boiler jacket, 2% of 6700	134
Boiler room piping and equipment, 1% of 6700	67
Flue gas combustibles, 0.5% of 6700	34
Bottom ash combustibles, 1% of 6700	67
Heat to the hot water distribution system	6398
Efficiency, %; based on Gross Heating Value = 100 x 6398/8600; steady conditions*	74.4

* The wood chip heating plant likely has an annual average efficiency of about 70%.

APPENDIX 6

Sequestering Combustion CO2 From Wood Chip Burning Plants Takes Decades

 

Here is some information for those who have been led to believe, or persuaded themselves to believe, wood burning is environmentally friendly.

 

Forests have aboveground and belowground new growth, which absorbs CO2 from the air and carbon, C, from the soil. Removing live trees, low-grade and high-grade, reduces CO2 absorption. In Vermont, about 50% of tree removals is used for high-grade purposes (the C stays sequestered, until some of it is burned); and about 50% is used mostly for burning (the C becomes CO2 and is released to the atmosphere), and a small quantity is used for pulp/paper mills (the C stays sequestered, unless some of it is burned).

 

Wood burning power plants (McNeil, Ryegate in Vermont) emit about 4 times the combustion CO2/kWh of high-efficiency gas turbine power plants.

 

The combustion CO2 of the first year of heating plant or power plant operation would be sequestered by re-growing trees according to an S-curve over a long period (See notes); slowly increasing during the first 1/3, rapidly increasing during the second 1/3, and slowly increasing during the last 1/3 of the period. That would be not much help to prevent the world’s climate from falling off the cliff during the next 20 to 30 years.

 

NOTE: The combustion CO2 of wood burning would be reabsorbed by new tree growth, if:

 

1) Logged forests would have the same acreage (they likely would not)

2) Forests would not further fragmented by roads or developed (they likely would be)

3) Forest CO2 sequestering capability, Mt/acre/y, remains the same (it could be less). See note

 

NOTE: Regarding the time period for sequestering the combustion CO2:

 

- 40 years is a US average. See Note.

- 80 to 100 years in northern climates with short growing seasons, such as northern Vermont and Maine. 

- 40 to 50 years in moderate climates with longer growing seasons, such as New Jersey and North Carolina

- 25 years between harvests of planted, fertilized, and culled forests of fast-growing pines in Georgia. 

https://www.pfpi.net/wp-content/uploads/2011/04/PFPI-biomass-carbon...

 

NOTE: On an A to Z basis, there would be about 15% of additional CO2 that has nothing to do with combustion, in case of wood chips, or about 20%, in case of wood pellets. This includes non-wood-burning CO2, such as from:

 

- Fuel used for managing wood lots, logging, chipping/pelletizing and transport,

- Energy to run the plant,

- Energy for decommissioning and reuse/landfill of the plant,

- Embodied energy in the A to Z infrastructures

 

 NOTE: 

- The EPA assumes sequestering of CO2 by undisturbed, healthy forests at about 1.0 metric ton per acre per year, as a US average.

- Disturbed, fragmented, less than healthy forests, as in most of New England, sequester much less than 1.0 metric ton of CO2 per acre per year, due to:

 

1) Acid rain and pollution from Midwest power plants, etc.,

2) Various encroachments, and

3) Colder climate and short growing season.

 

Yet the Vermont and Maine Environmental Departments claim 1.0 metric ton per acre per year!

 

Piling up the CO2 Year After Year

 

Re-growing trees would sequester the combustion CO2 of Year 1 of plant operation over about 80 to 100 years, in New England.

 

The CO2 of Years 2, 3, 4 to Year 40 would be added to the CO2 of Year 1, and be sequestered in a similar manner, except shifted forward by a year.

 

In Year 40, there would be 40 layers of CO2 and 40 forest areas in various stages of regrowth, as a result of cutting trees for burning.

 

Year 40 is assumed to be the last year of plant operation. It is likely that plant would be replaced to repeat the cycle.

 

During Year 41 through 80, there would be 41 to 80 layers of CO2 and 41 to 80 forest areas in various stages of regrowth, as a result of cutting trees for burning.

 

Closing Down Wood Burning Power Plants

 

It would be far better for New Hampshire, Maine and Vermont to shut down wood burning power plants, as time is of the essence regarding “climate change”, according to some people. See table 5 and URL.

 

- In Vermont, utilities are forced to buy wood electricity at about 10 c/kWh, as part of the Vermont Standard Offer program, and as required by the Vermont Renewable Portfolio Standard program.

 

- In New Hampshire a law was passed in 2018 to subsidize money-loosing NH wood burning power plants. The plants need to be base-loaded to maximize production and need to sell at about 9 - 10 c/kWh to be viable. The subsidy would impose an extra cost on ratepayers of about $25 million/y. Implementing the law is held up in various court cases for environmental reasons.

 

- The wholesale prices of the NE grid averaged about 5 c/kWh since 2008, courtesy of abundant, domestic, near-zero-subsidized, clean-burning, low-CO2 gas at about 5 c/kWh, and near-zero-subsidized, near-zero-CO2 nuclear at 4.5 - 5 c/kWh.

http://www.windtaskforce.org/profiles/blogs/furnaces-for-heating-an...

 

Table 5/Fuel	lb CO2/million Btu	Plant efficiency, %	lb CO2/MWh	CO2 Ratio
Wood chip; McNeal/Ryegate*	213	25	2907	4.0
Wood chip; Denmark	213	30	2423	3.3
Hard coal	206	41	1712	2.4
No. 2 fuel oil	161	35	1572	2.2
Natural gas, CCGT*	117	55	726	1.0

*

Plus upstream CO2 (logging, chipping, transport, etc.) of about 5 to 10%, if burning wood chips

Plus upstream CO2 (logging, chipping/pelletizing, transport, etc.) of about 10 to 15 %, if burning wood pellets

CCGT = Combined-cycle, gas turbine plant

APPENDIX 7

Wood-Burning Power Plants

 

Vermont has the Ryegate wood burning plant, which gets about 50 percent of its trees from northern NH. Its efficiency is about 24%, but the efficiency from “forest to electric meter” is about 15.5 percent. That means the energy equivalent of about 5.5 out of 6.5 trees is wasted.

 

Ryegate burns about 250,000 ton of trees per year, which has about 250,000 ton of combustion CO2 emissions per year.

  

There is non-combustion CO2, about 15% to 20%, on a forest-to-electric meter basis.

That CO2 is due to logging, chipping, transport, power plant operations, disturbance of the forests, etc.

That CO2 is absorbed in some other manner or is added to the atmosphere.

 

NOTE: In Georgia, with planted forests that are managed/culled for quality and fertilized, the time between harvests is about 25 years.

 

http://www.windtaskforce.org/profiles/blogs/is-burning-wood-co-2-ne...

http://www.windtaskforce.org/profiles/blogs/wood-for-fuel-logging-i...

http://www.windtaskforce.org/profiles/blogs/a-comparison-of-wood-ch...

http://www.windtaskforce.org/profiles/blogs/dismal-economics-and-in...

http://www.windtaskforce.org/profiles/blogs/governor-sununu-vetoes-...

 

A much better approach would be to have high-efficiency wood burning heating plants. The efficiency from "forest to heating appliance" would be about 62.5 percent. That means the energy equivalent of only about 0.6 out of 1.6 trees is wasted.

http://www.windtaskforce.org/profiles/blogs/more-realistic-energy-s...