Wood Fuels and Energy Risks

In Part 1 of my TEC Post the history and some of the options to expanding the use of renewable wood in a more responsibly environmental manner was covered. This Part 2 Post will cover additional options to more safely expanding the production and consumption of wood; the second largest renewable energy source within the U.S. today.

About 2.5 million U.S. Households currently use wood as their primary source of Residential heating fuel.  Concerns have been apparently growing as to the possible respiratory health impacts on many Residents, particularly in more densely populated regions around the U.S.  Possibly due to wood smoke particular material (PM) emission concerns or increasing access to generally cleaner and more cost effective heating fuel alternatives, the Residential Sector’s wood consumption has decreased very significantly in recent decades.  A large part of the fuels-switching from wood-to-alternatives unfortunately involves primarily substituting fossil fuels, which increases U.S. carbon emissions.  Also this fuels-switching trend does not mitigate most Resident’s health risks from wood smoke exposure.  What are other feasible options to continue utilizing and possibly increasing renewable wood biofuels, and do so by substantially reducing current and future health exposure risks of potentially hazardous wood smoke PM emissions?

U.S. End-use Sector Historic Wood Consumption – Wood has been historically used by all End-use Sectors within the U.S.  Even the Transportation Sector (Railroads) used wood until the mid-late 1800’s.  While wood continued to be a primary Residential heating fuel throughout the 1800’s and the early 1900’s, its use began to decline very significantly during the mid 1900’s due to fuels-switching to coal, natural gas, petroleum and electric heaters.  Since 1950 wood consumption of other End-use Sectors began to increase significantly.  Refer to the following Figure 5.

Figure 5 – U.S. End-use Sectors’ Wood Consumption, 1949-2013


Data Source – EIA Tables 10.2a, 10.2b and 10.2c.  ` 

EIA data indicates that the wood consumption of the Residential Sector declined 1949-74, increased and peaked in 1985, and then declined again.  The Industrial Sector’s wood consumption increased almost continuously during most the 1900’s, exceeded the Residential Sector in 1960, and increased to its historic peak in 1997.  The Residential Sector’s wood consumption has been relatively constant on average since 1997.  The Power and Commercial Sectors also experienced small, but limited increases in wood consumption over the past couple decades.

The EIA and NASEO predict that the Residential Sector’s wood consumption could possibly experience a small increase in the near future.  However, longer term projections such as the EIA AEO 2014 indicate a continuous gradual decline in future Residential renewable wood consumption, and possible increased consumption within other End-use Sectors.  Are these longer term renewable wood consumption projections reasonable, and, are there alternatives to better control wood smoke PM and other potentially harmful combustion emissions from existing fireplace/non-EPA certified woodstove technologies?

Potential Health Hazards of Burning Wood – As discussed and actively commented-debated in the first TEC Post: “Renewable Wood Fuels (Part 1): Environmentally Beneficial or a Chronic Problem?”, wood smoke emissions have and in some cases apparently still present significant respiratory health risks for numbers of U.S. Residents.  To control indoor wood smoke emissions the U.S. has mandated new-proper building ventilation standards over 50 years ago.  Outdoor wood smoke emissions have been formally addressed by the EPA beginning 1988 and more recently by a new developing woodstove/heater emission regulation.  Commercial and Industrial smoke emissions have also been very aggressively regulated and reduced since the original Clean Air Act back in the 1970’s.

In 1997 the EPA passed the first PM2.5 regulation that significantly includes wood smoke.  This regulation was updated in 2006, which further restricted burning wood.  Those Cities that have been found in non-attainment with the PM2.5 regulations have been required to take many corrective actions including implementing ‘wood burning bans’.  As a result, many large Cities have increasingly imposed wood burning bans during winter months when ‘thermal inversions’ are major contributors to smog-high PM2.5 conditions.  As a result, some cities are or planning to restrict high wood smoke producing technologies, which primarily includes limiting new conventional fireplaces.

Reducing Residential Wood Stove/Heater Smoke Hazards – The EPA has historically controlled wood smoke PM pollution indirectly by establishing regional PM10-PM2.5 regulatory standards.   These regulations led to the EPA facilitating the development of low emission ‘certified woodstoves’ and a new ‘wood-wise’ program to help increase Residents’ wood smoke hazards awareness and facilitate their abilities to minimize smoke emissions.  As a result of these and other related programs substantial reductions in woodstove/heater unit technologies’ PM emissions performance has been accomplished in recent years.  Refer to Figure 6.

Figure 6 – PM Emisions of Different Residential Heater Technologies


Data Source: BAAQMD Publication.

Example Environmental Agency data indicates that wood smoke contributes to about 1/3rd of total PM emissions within higher population density regions (the SF Bay Area for example) and the largest source of wood smoke appears to be conventional wood-burning fireplaces.   Based on BAAQMD data wood-burning fireplaces are clearly the worst sources of wood smoke pollution and produce 2000% greater PM emissions than EPA certified woodstoves (per unit heat output).  The lower PM emission heater sources are normally natural gas and propane (LPG) fueled (furnaces), followed by (No.2 heating) oil.  Electric heaters can have zero Residential local PM emissions; however the level of more distant outdoor emissions depends on the source and mix of electricity supply.

The lowest PM emissions from woodstoves/heaters clearly come from (wood/biomass) ‘pellet” fuels.  Even though the cost of wood pellet stoves and fuels are generally more expensive to alternative EPA certified woodstoves, this technology can produce 2/3rds lower PM emissions than non-pellet certified stoves.

Advantages of Wood Pellet Stoves/Heaters – About one million U.S. Residences have and use wood pellet heaters/stoves currently.  Due to the generally increased costs of wood pellet stoves & fuels, this represents less than 10% of total wood fireplace/stove installations within U.S. Residences today.  However, wood pellets are most often used as the primary Residence heating fuel and currently makeup about 15% of the total Residential Sector’s wood fuels consumption (data basis). 

Wood pellets have many other actual and potential environmental benefits compared to seasoned and green wood.  The emissions of many harmful pollutants from processed-dried pellets are substantially lower than seasoned and particularly green wood.  Green wood is the worse polluting fuel since it contains large amounts of natural organic compounds.  Burning green wood often yields substantially increased ‘volatile organic compounds’ (VOC: creosotes, aldehydes, dioxins, and other hazardous air pollutants or HAP’s), and increased nitrogen oxides (NOX) and carbon monoxide (CO).  Fuel pellets contain substantially reduced organic compounds and burn much more cleaner in wood pellet stoves, which produces substantially lower NOX, CO, HAP’s and PM compared to green and most seasoned wood fuels.

Fuel pellets also provide an opportunity to expand the production and consumption of many other cellulosic biomass materials.  Wood or other biomass fuel pellets can be produced from a wide variety of sources including wood wastes and brush from harvesting or land clearing, and a wide variety of non-food agriculture products or wastes (switchgrass, hemp, corn stover, etc.).

Since the vast majority of wood burning stove/heater-units within the Residential Sector are conventional fireplaces and non-certified/non-pellet woodstoves, this situation possibly presents significant opportunities to substantially reduce wood smoke PM and other HAP emissions.  The manufacture of cleaner pellet heaters and production-consumption of wood+other biomass pellets also can provide many opportunities in addition to reducing potentially harmful pollution.  Added pellet fuel technology benefits include not only displacing fossil fuels with increased renewable biomass heating fuels, but also possibly contributing to substantial expansion of new heater units manufacturing and wood/pellet biomass fuels production business growth opportunities.

Other Potential Opportunities of Expanding Wood Pellet Production and Reducing Smoke PM/HAP Emissions – Due to a number of factors including record droughts, insect infestations and inadequate land management, the largest sources of wood smoke are often the numerous (and growing) forest, brush and grass wildfires that appear to be increasingly plaguing the U.S.  The U.S. has some of the most extensive and dense forests among Developed Nations.  Unfortunately, the U.S. also is subject to some of the largest and most voluminous forest wildfires.  In recent years the U.S. had experienced 15-20 major wildfires annually and each wildfire incident consumed at least an average of 35,000 acres.  These wildfires often emit far more hazardous PM and HAP pollution than Residential fireplaces in recent years.  Most of the wildfires tend to concentration the smoke to levels that is extremely hazardous to downwind exposed Residents.  When you consider the fact that almost half the U.S. Residents live near or adjacent high density forests, the smoke exposure health impacts can potentially be larger from wildfires then most existing Residential fireplaces.

Besides the growing drought conditions in the West-Midwest, one of the largest and growing problems has been ‘bark beetle’ infestations.  Over 22 million acres and growing of dead trees exist today across many forest regions within the U.S. due to insect/beetle infestations.  This represents over 20 years of wood supplied to the Residential Sector annually.  If these existing dead trees were harvested and a significant percentage processed into pellets the opportunities-benefits could be potentially very large.  This would involve thinning existing forests to help prevent future forest fires and substantially increasing the availability and consumption of cleaner renewable heating fuels for a large number of Residents than currently rely on wood for primary and secondary heating fuels.

Just think of the large number of jobs that could be created by substantially expanding the Work Crews needed to more properly thin/replant U.S. forests (and help prevent inevitable major wildfires), building & operating new pellet fuel production facilities (fed by the harvested dead wood/waste), building & operating new manufacturing facilities to produce certified & pellet stoves, and the associated economic growth benefits of a substantial expansion of this part of the U.S. economy.  Besides dead trees, and due to a number of budget constraints, most healthy forests have become overgrown in recent decades and also need to be thinned to prevent nearly uncontainable major wildfires caused by lightning storms or human related incidents.

Possible Options to Consuming Dead and Overgrown Forests – The initial investment costs for new-cleaner and higher efficiency Residential woodstoves/heaters or fireplace inserts can be onerous for many Residents that struggle to meet their basic living expenses currently.   New wood smoke regulations could adversely impact many Rural Residents that must rely on wood fuels for primary home heating.  There are of course a number of regulatory-financial support options of how to help lower income Residents afford cleaner certified woodstoves/heaters.

Even if a state-of-art certified woodstoves/heaters are installed, to minimize smoke emissions requires proper operation.  This involves properly and continuous following low emission operating procedures during stove/heater startup and operation.  The problem with these cleaner and more efficient certified woodstoves is that they are much more complex to operate than a simple fireplace.  Clean-efficient operation requires proper fueling prior to lighting-starting the stove/heater operation, correctly-continuously adjusting air inlets within safe-efficient firebox temperature operating targets, and properly adjusting the air-firebox temperature to safely-properly open and refuel the firebox as needed during continuous operation.  If not carried out properly, the best designed certified wood/pellet stoves can produce significant smoke and waste fuel, which compromises its cleaner-efficient design, and, could adversely impact the Neighbors.

To avoid the risks of improper Residential Sector certified woodstove/heater operation and increased smoke PM/HAP emissions a feasible alternative strategy would be to substantially expand the use of renewable wood fuels within the Industrial and Power Sectors.  Unlike the need to season (dry) or produce processed pellet biofuels, the raw wood/biomass could be burned directly in new Industrial/Power boilers-power generation facilities and the smoke emissions properly controlled as any other state-of-art stationary facility.  Combustion emissions from Industrial facilities are normally controlled by installing required stack emission BACT environmental controls.  To avoid the problem that has occurred with many recent, highly polluting biomass/waste fueled boilers the EPA and State Environmental Agencies must not allow any unreasonable exemptions such as ‘minor source’ designations that have led to substantial pollution for some poorly permitted biowaste combustion boilers-power plants in recent years.

In Conclusion – The U.S. has an opportunity to significantly reduce its carbon emissions and substantially reduce the amount of wood smoke hazardous PM/HAP emissions many Residents are currently and will continued to be exposed to in the future.  The solution should include making the U.S. Forest Service and Bureau of Land Management more responsible and accountable for better managing U.S. forests.  By harvesting and thinning existing dead and overgrown forests, the U.S. could feasibly expand the consumption of renewable wood biofuels by at least 200 Trillion Btu per year (50% increase in Residential Sector or 10% increase in U.S. total wood consumption).  This is equivalent to reducing U.S. carbon emissions by 10-15 million MT per year (LPG displacement basis) or removing up to about 0.5 million light duty vehicles from the roads.  .

In addition the installation and proper use of certified EPA wood/pellet stoves/heaters needs to be substantially expanded.  If after a thorough analysis of these or other viable options’ costs-and-benefits indicate that expansion of the Industrial and Power Sectors’ renewable wood consumption will be more cost effective overall, this new strategy should be pursued with high priority.  In the mean time, an optimal balance between costs and benefits for Rural Residents who most rely on wood heating fuels should probably be pursued in parallel to other cost effective renewable wood opportunities.