A Comparison of Wood Chip and Oil-Fired Power Plants

The Vermont media site, VTDigger, had a recent comment: “Just a single 25 megawatt (MW) wood chip plant could provide some 4 percent of Vermont’s consumption, 24/7/365, and would contribute to the Vermont economy in the form of jobs and money in circulation from the wages, taxes — wealth created in the state that stays in the state.”

Special Report: New Renewable Energy Standard Would Revolutionize Energy Use in Vermont

The comment is correct about jobs, wages, taxes, etc., but are wood power plants:

• Efficient? NO. The efficiency of wood power plants is about 25%, fuel oil power plants about 33%.
• Producing low-cost energy? NO. The plant owners likely would sell the electricity at about 10 c/kWh*
• Requiring public subsidies? YES. Federal and state up-front cash grants, and a subsidy of about 5 c/kWh.
• Increasing CO2 emissions? YES. See below explanations and URLs.
• Increasing health-damaging air pollution? YES. See below explanations and URLs.
• Negatively impacting forests? YES. See below explanations and URLs.

* The owners of the Ryegate, VT, 20 MW, wood chip power plant receive about 10 c/kWh for electricity fed to the NE grid (156 million kWh in 2015), under Vermont’s SPEED program. NE wholesale prices have averaged about 5 c/kWh for the past 5 years, and likely will not be increasing, due to an abundance of domestic, low-cost, natural gas.

http://www.vermontstandardoffer.com/ryegate-production/

Vermont Needs Low-Cost Electrical Energy: Vermont has a near-zero, real-growth economy. It needs to have more low-cost energy to make ALL sectors of Vermont’s economy more viable, so they can expand, be profitable, create good, steady, full-time jobs, that pay good wages and have good benefits. Those private businesses and their workers usually pay more income and other taxes, than subsidized, non-profit and government/private partnerships and their workers.

Vermont, one of the poorer states in the U.S., with a fragile, services-dominated economy, cannot afford to turn over a major part of its economy to expensive renewable energy production. With more and more of such subsidized, renewable energy projects, Vermont’s entire economy would be facing an increasingly stronger headwind for many years.

Increased energy efficiency, plus increased supply of low-cost (6 – 7 c/kWh) hydro energy from Hydro-Quebec, would REDUCE energy bills of Vermont’s already-struggling households and businesses, add practically no CO2, and no pollution!

Countries with higher wind and solar energy on the grid invariably have higher household electric rates. Figure 7 of this URL shows Denmark and Germany having the highest rates; France, 75% nuclear, has one of the lowest.

http://euanmearns.com/an-update-on-the-energiewende/

Wood Burning Plants and CO2 Emissions: A wood chip power plant or heating plant adds CO2 through: 1) Logging soil disturbance, vehicle transport, equipment use, refurbishments and replacements, diesel fuel burning; 2) Plant construction; 3) Plant O & M, refurbishments and replacements; 4) Plant decommissioning. Those CO2 emissions would require a forest area up to 15% greater than the wood burning CO2 to reabsorb it over up to 60 years.

http://www.theenergycollective.com/willem-post/2392251/wood-for-fuel-logging-increases-co2-and-damages-forest-health

http://www.theenergycollective.com/willem-post/2390703/a-comparison-of-wood-chip-and-oil-fired-power-plants

http://www.theenergycollective.com/willem-post/2225851/economics-and-co2-emissions-montpelier-district-heating-plant

CO2 Emissions and Sequestering: Vermont CO2 emissions are about 8,370,000 Mt/y*, of which Vermont forests sequester about 8,230,000 Mt/y, 1.82 Mt/acre/y*. The remaining 140,000 Mt/y becomes an annual addition to the atmosphere. Vermont forests cannot sequester all of Vermont CO2, i.e., there is NO spare forest area in Vermont, or elsewhere, to sequester ANY CO2 from wood burning.

*The 1,603,737 Mt of CO2 from wood burning is improperly excluded, due to the historical myth “burning wood is CO2-neutral”. See Note.

NOTE: Conversion factor for carbon sequestered by 1 acre of average U.S. Forest = – 0.29 Mt C/acre/year x (44 CO2/12 C) = -1.06 Mt CO2. Vermont claims 8.23 million Mt/y/4,511,000 forest acres = 1.82 Mt/acre/y; Maine claims 0.3 x 44/12 = 1.1 Mt/acre/y.

https://www.epa.gov/energy/ghg-equivalencies-calculator-calculations-and-references

http://www.forestecologynetwork.org/climate_change/sequestration_facts.html

Forests and CO2: It was previously thought old-growth forests ceased to accumulate carbon. As a result, they are not protected by international treaties. But, due to research, it is now known such forests still continue to add biomass and sequester and store enormous amounts of CO2, i.e., they serve as a global CO2 sink, and should be protected.

http://www.nature.com/news/2008/080910/full/news.2008.1092.html

In the US Northeast, almost all forests are in the “infant to prime of life” stage, generally aged 0 – 80 years, well below old-growth stage, and adding much biomass and absorbing much carbon. Logging for burning, or fires, both immediately release this absorbed CO2, which gets very slowly reabsorbed by new forest growth, if allowed to proceed.

http://www.maforests.org/NewEnglandBiomess.ppt

Logging a forest for burning offsets net forest growth, thus reducing, or eliminating, the net forest CO2 sequestration benefit. Leaving a forest undisturbed, instead of logging it, is always better for net CO2 impacts, even if including forest growth and carbon storage in wood products, such as lumber. As CO2 levels in the atmosphere are the result of CO2 added to, or subtracted from, any lost, or reduced net forest CO2 sequestration, increases overall atmospheric CO2 levels.

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

No Logging Provides Highest Forest Carbon Storage: http://www.maforests.org/Keeton.pdf
Logging Destabilizes Soil Carbon: http://www.eurekalert.org/pub_releases/2014-12/dc-ldf120214.php
Massachusetts Forest Watch: http://www.maforests.org/Links.pdf

Burning Wood is Not Renewable: A forest regenerates from the harvesting activity (which also disturbs the forest floor, releasing CO2), by absorbing CO2 from the atmosphere, and storing C as hydrocarbons in new biomass growth above and below ground, and releasing O2. That process may take up to 100 years in New England, up to 50 years in the US southeast, such as in Georgia. See below URLs.

Proponents simply declare, “burning wood is CO2-neutral”, which creates political “feel-good”, because it conjures up the APPEARANCE of meeting CO2 targets, etc. However, it perpetuates uninformed thinking by lay people and others. Proponents purposely forget to add: “over a period of up to 100 years in New England, up to about 50 years in the US southeast.”

“CO2-neutral” is not close to true. Even if the logging were “sustainable”, i.e., no more cutting than biomass growth, there would still be a large carbon impact, due to lost carbon sequestration from the biomass growth now being used to “offset CO2 emissions”, instead of that biomass growth reducing atmospheric CO2.

All of the harvested land area must be allowed to regenerate biomass to its former state, instead of being used for development. A further burden would be the CO2 from activities mentioned under above section “Wood Burning Plants”. In New England, adding wood chip power plants, which typically get much of their wood by clear-cutting, would be a 100-year “save the world solution”.

https://ampd.epa.gov/ampd/
ttp://www.pfpi.net/wp-content/uploads/2011/04/PFPI-biomass-carbon-accounting-overview_April.pdf
https://ces.williams.edu/files/2011/02/Mary-Booth-Wiliams-Talk.pdf
http://www.globalchange.umich.edu/globalchange2/current/lectures/deforest/deforest.html
http://www.maforests.org/Timberspeak-Timber_Industry_Propaganda.pdf

Burning Wood is Not Clean and Not Green: Usually, it comes as a surprise to lay people, wood burning has at least as much CO2/kWh and particulate/kWh as coal. Exhausts from wood chip-fired plants, which are used around the clock in some communities, likely increase the air pollution of nearby areas, due to volatile organic compounds (VOCs); carbon monoxide; and particulates, which cause diseases of respiratory systems.

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

“Small” biomass facilities have high pollution rates, so the combined impacts of “small” facilities can create a “big” problem. In the below table are the pollution rates for modern institutional, or commercial-scale, wood burning plants, particularly school-sized wood chip boilers, compared to fossil fuels plants, as provided by the Biomass Energy Resource Center (which promotes biomass) for the MA Department of Energy.

The particulate emissions from above wood burning data are 7 times worse than oil, 14 times worse than natural gas, and 25 times worse than propane. Even if better pollution control technologies were used, the wood emission profile remains worse than other fuels that use similar pollution control.

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

NOTE: Recently, the EPA proposed reducing the particulate emissions of NEW residential woodstoves by 80%. The proposal covers woodstoves, fireplace inserts, indoor and outdoor wood boilers (also called hydronic heaters), forced air furnaces and masonry heaters.

http://yosemite.epa.gov/opa/admpress.nsf/0/e3175e041784cf6485257c550059ca4c?OpenDocument

CO2 from Wood Burning: In the US northeast, the industry standard is burning one ton of green wood (7.6 million Btu/green ton; 45% moisture; 7.6 million/1100 = 6,909 Btu/lb, dry) creates a little more than one ton of CO2, and dry wood consists of 50% carbon (by weight). See table.

The CO2 is calculated as follows:

C = (1 – 0.45) ton dry wood/green ton x 0.5 = 0.275 ton/green ton

C + O2 = CO2.  By molecular weight = 12 + 32 = 44; 1 ton C + 2.67 ton O2 = 3.67 ton CO2; 0.275 x 3.67 = 1.01 ton CO2/green ton.

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

NOTE: Below is a comparison of the combustion CO2 of various fuels in latest-technology power plants; excludes other CO2 contributors:

Super-critical coal plants, 220 bar and 600/600 °C, efficiencies of 42%; ultra-super-critical, 300 bar and 600/600 °C, efficiencies of 45% to 48%.
CCGT gas plants, “H class”, 60% efficient at ISO conditions. See URL
Wood-chip plants 50 MW, 30% efficient. See URL

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

http://www.brighthubengineering.com/power-plants/72369-compare-the-efficiency-of-different-power-plants/

http://www.aet-biomass.com/en-GB/Home/References/Biomass-Fired-Plants/Western-Wood-Energy-Plant.aspx

NOTE: Vermont’s wood-for-fuel harvest was 1,216,167 ton in 2014, of which 868,825 for space heating and 347,342 for electrical generation. About 347,342/719,033 = 48% of total electrical tonnage was harvested in Vermont. See URLs.

http://fpr.vermont.gov/sites/fpr/files/About_the_Department/Library/Library/FINAL_2015 Residential Fuel Assessment Report.pdf   Page 14

http://fpr.vermont.gov/sites/fpr/files/Forest_and_Forestry/Forest_Based_Business/Library/2014 HARVEST SUMMARY_final.pdf

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

NOTE: Below are listed the wood tonnage and combustion CO2 tonnage of Vermont’s wood chip power plants in 2015.

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

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

NOTE: Below is a comparison of CO2 /MWh for various base-loaded plant types; variable solar and wind energy are supplementary energy sources, i.e., not base-loaded. The wood combustion CO2 gradually diminishes (not to zero) over at least 5 decades, if the deforested area is allowed to regrow itself to its before-harvest status.

NOTE: The Vermont Comprehensive Energy Plan (CEP) stated goal is to have 90% RE of ALL energy by 2050, not just electrical energy, which is only 35% of all energy. The plan includes proposals that would increase cutting and burning of Vermont’s forests. See table.

This would increase the VT wood harvest for fuel by more than 1,600,000/1,216,167 = 132%, mostly from in-state forests. Add to that the clearing for access roads and 500-ft-tall wind turbines and those forests, with hundreds of clear-cut areas, will look much different from today. It would immediately add to the atmosphere 1,616,000 ton of CO2/y, due to burning, plus prevent the forest, which is in “infant to prime of life” stage, from absorbing CO2, if it were left alone to grow new biomass, instead of being developed as a “working landscape”. Increased logging likely will cause decreased overall growth and sequestration, causing a double whammy of increased CO2 stack emissions and decreased forest sequestration.

http://www.maforests.org/Biomass%20Assumptions.pdf

NOTE:

• The most valuable portion of a tree is the straight trunk.
• Forest residue consists of branches, tops, areas with splits or sweep, crooks, or portions of a tree with rot; moisture 40% – 50%; fuel value 4,625 Btu/lb.
• Sawmill residue consists of bark, sawdust, chips; moisture 50%; fuel value 4,500 Btu/lb.

NOTE:

• Forest residue usually is chipped for burning. Much of forest residue is left to rot.
• Loggers, in sustainable-harvesting mode, often say they take only sick, near-dead trees and other “waste” wood, but, in almost all cases, that is not close to the truth.
• Loggers, in clear-cutting mode, take almost all there is to take. See Figure 4, 5, 6 of URL.

http://www.stlawu.edu/green/sites/stlawu.edu.green/files/reports/INRS Final Report.pdf

NOTE: There is other biomass, such as corncobs, cornstalks, various grasses, bamboo, etc., that can be harvested each year, or every few years. Those crops require much land area. In Vermont, most of that land area would need to be created by eliminating open spaces, meadows, etc., to ensure biomass would be available in the quantities required by Vermont. In that case, biomass could be claimed to be PARTIALLY renewable. However, the soil likely would become less useful for other agricultural purposes, due to depletion. Taking, taking, taking from the land, without giving back, is not a long-term, sustainable option, as any farmer knows.

Wood Chip Plants Heating Energy-Hog Buildings: Some people advocate for wood chip central heating plants, or wood chip combined heating/power (CHP) plants, with thermal distribution systems to heat buildings. However, any new central plants likely would be connected to energy-hog buildings, which make such systems uneconomical, especially with higher energy prices.

Such central plants systems may appear attractive to people, who are not familiar with the numbers, but as energy-efficient building design has significantly advanced since the oil price shock of 1973, the economics of NEW central plant systems became unfavorable, except in Europe, Japan, etc., which have higher energy prices and more energy-efficient buildings.

It would be far less costly to pay some additional money to have zero-net-energy or energy surplus buildings with heat pumps and PV solar systems, instead of central plant systems. Trying to convince decision makers, including legislators, etc., to let go of their ingrained, uninformed thinking is quite an uphill battle.

NOTE: With enough “free” money, i.e., cash subsidies, anything can be made to appear economical, such as the recently built, much-praised, wood chip District Heating Plant, Montpelier, VT, which:

Received 100% of its $20 million construction cost as federal, state and city cash grants to heat energy-hog buildings, and
INCREASED CO2 emissions compared to No. 2 fuel oil, that would take about 100 years to be reabsorbed, and
Is operated at a loss, because heat users are paying at rates too low to recover all O&M and refurbishments costs, and
Had that been a privately financed plant, i.e., without subsidies, it would lose at least $2.5 million per year, including paying real estate taxes.

Repeating such a folly throughout Vermont would be irrational energy policy. That $20 million should have been spent on increased energy efficiency.

http://www.theenergycollective.com/willem-post/2225851/economics-and-co2-emissions-montpelier-district-heating-plant

Evaluated Alternatives: Two alternatives were evaluated:

Alt. 1: Wood chip power plant
Alt. 2: No. 2 fuel oil power plant

Results of Evaluation:

1. Alt. 2 has about 40% less capital cost than Alt. 1
2. Alt. 2 has much less staffing, maintenance and other operating cost/y than Alt. 1
3. Alt. 2 produces electricity at a much lesser cost/MWh than Alt. 1
4. Alt. 2 emits about 54.3% less CO2 emissions/y than Alt. 1*
5. Alt. 2 requires much less area than Alt. 1

* The percentage gradually diminishes over 50 – 100 years, as the forest recovers, i.e., reabsorbs the combustion CO2. The total CO2, due to activities other than burning wood, would require a forest area about 20% larger than the harvested area.

Summary of Alternative No. 1: Wood Chip Power Plant

Assumptions: Capacity 25 MW; capacity factor 90% (base-loaded mode); 25% efficiency; 7.6 million Btu/green ton (45% moisture); 3,413,000 Btu/MWh; cord weight of low-grade, green wood chips = 5,000 pounds = 2.5 tons; 0.5 cord/acre to conform to sustainable forestry practice; 32 ton/truckload; 250 hauling days; 640 acre/sq. mi.; a ton = 2000 lb; a metric ton = 2204.62 lb.

http://www.biomasscenter.org/pdfs/Wood chip-Heating-Guide.pdf

Turnkey capital cost = 25 MW x $2,500,000/MW = $62.5 million
Electricity, gross = 25 x 8760 x 0.90 = 197,100 MWh/y
Electricity, self use = 22,675 MWh/y
Electricity, net = 197,100/1.13 = 174,425 MWh/y
Heat input = 197,100 x (3,413,000 Btu/MWh)/0.25 = 2,691 billion Btu/y
Wood chip supply = 2,691 billion Btu/y/(7.6 million Btu/ton) = 354,054 ton/y, or 1.8 ton/MWh
Truckloads = 354,054/32 = 11,064/year, or 44/day
Cords = 354,054/2.5 = 141,622/y
Area* = 141,622/0.5 = 283,243 acre, or 443 sq. mi

*In the real world, the plant would get its wood from an area with a 30-mile radius, or 3.14 x 30^2 = 2,826 sq. mi., about 6.4 times greater, or which about 15% would be used for clear-cutting. As a result, Vermont could have only a few additional 25 MW wood-burning plants.

NOTE: The 40-year clear-cutting for a McNeil-size power plant would be 13000 ton/MW x 50 MW x 0.75, CF in 2015 x 1/(78 ton/acre x 1/3), usable fraction x 40 y, time between harvests = 0.75 million acres. McNeil gets its wood from an area with a 50-mile radius, or 3.14 x 50^2 x 640 = 5,024,000 acres, of which about 15% is used for clear-cutting.

Average New England Standing Biomass = 78 green tons per acre.

http://www.maforests.org/STANDING%20BIOMASS%20CALC.xls

CO2 Emissions:

Below is the lb CO2/million Btu for No.2 fuel oil or diesel fuel.

Harvest, process, transport = 2.09 gal diesel/ton x 24.2922 lb CO2/gal x 354,054 ton wood/y = 8,988 ton CO2/y

Combustion = 1.01 x 354,054 ton wood/y = 357,594 ton CO2/y

Total = 366,582 ton CO2/y

NOTE: The CO2 due to building the plant, land disturbance, O&M, and decommissioning the plant is omitted

Summery of Alternative No. 2: No. 2 Fuel Oil-Fired Power Plant

Assumptions: Capacity 25 MW; capacity factor 90% (base-loaded mode); 35% efficiency

The turnkey capital cost = 25 MW x $1,500,000/MW = $37.5 million
Production = 25 x 8760 x 0.90 = 197,100 MWh/y
Heat input = 197,100 x (3,413,000 Btu/MWh)/0.35 = 1,922 billion Btu/y

CO2 Emissions:

NOTE: The CO2 due to building the plant, O&M, and decommissioning the plant is omitted.

Photo Credit: Jori Samonen via Flickr