Renewable Wood Fuels

Wood has been the primary source of heating fuels since the dawn of Civilization.  Over the centuries wood fuels have been replaced by development of alternative fossil fuels and energy generation-use technologies.  Developing Countries historically have often transitioned from wood-to-coal & petroleum, followed by natural gas fuels.  Since the development of electricity in the late 1800’s, this energy-power source has enabled the development of cleaner and renewable energy supplies.  Cleaner energy sources began with developing large hydropower plants, followed by nuclear, and more recently wind & solar power.  Despite the growing development of many newer and cleaner energy generation technologies, wood continues to be a major source of renewable fuels for both heating and power generation.

The smoke from burning wood has historically been a major source of widespread respiratory health problems.  With the current of health issues possibly attributed wood smoke from uncontrolled combustion sources, should the EPA much more aggressively regulate this source of renewable energy within the U.S.?

History of U.S. Primary Energy Supplies – Wood has been the primary source of heating fuels in North America since man first migrated from Asia.  Over the past couple centuries the historic high levels of energy supplied by wood within the U.S. was exceeded by coal (mid-1880’s), then petroleum (late-1910’s), followed by natural gas (late-1920’s) and more recently hydropower (late-1950’s).  Refer to the following graph.

Figure 1 – U.S. Primary Energy Consumption: 1850-1975


Data Source – EIA Tables: E1 and 1.3.  Note: ‘Other Renewables’ consisted of at least 98% wood up to 1975.

Beginning in the 1960’s wood and agriculture wastes (or biowastes) were increasing used to generate heat and electric power.  Nuclear power development also began during this period.  Refer to the following graph.

Figure 2 – U.S. Low Carbon Primary Energy Consumption: 1950-2015Image

Data Source – EIA Tables: E1 and 1.3.  Note: ‘Biomass’ includes wood, biowaste and vehicle biofuels.  ‘Primary Energy Consumption’ data for 2015 is estimated based on AER 2013 and AEO/STEO 2013-15 data.

Following 1970 Nuclear power grew very rapidly and exceeded Biomass fuels by about 1975 and Hydropower by the early-1980’s.  Nuclear power became the largest ‘zero carbon’ energy/power source ever since.  Due to a combination of stagnate Hydropower growth and increasing Biowaste+Biofuels, total Biomass energy exceeded Hydropower in the late 1990’s.

Total Biomass primary energy consumed has increased overall since the mid-1970’s.  How much of this increase is due to Wood?  Refer to the following graph.

Figure 3 – U.S. Renewable Primary Energy Consumption: 1950-2015Image

Data Source – EIA Tables: E1, 1.3 and 10.2a-c.  Note:  ‘Primary Energy Consumption’ data for 2015 estimated based on AER 2013 and AEO/STEO 2013-15 data.

Due to the combination of peaking consumption in the Residential and Industrial Sectors, total Wood primary energy consumption peaked in the mid-1980’s.  The Renewable Fuel Standard (RFS) has required increased volumes of biofuels (primarily ethanol) be blended into petroleum motor fuels each year.  As a result of the RFS and decline in Wood consumption in recent decades, total (vehicle) Biofuel primary energy is projected to possibly equal Wood by 2015.  In addition, Wind power is projected to also exceed Wood primary energy by possibly 2020.  The large expansion of Wind power is of course due to over 20 years of very generous Federal and State subsidies, and various State Renewable Portfolio (or power) Standards.

Wood Consumption Environmental Impacts - While Wood has historically been one of the most important primary energy sources, the smoke produced by conventional use-combustion can have significantly negative environmental impacts.  One of the most serious environmental-health impacts is due to the soot or particulates (matter or PM) generated in conventional fireplaces, stoves and heaters.  The World Health Organization estimates that up to 7 million fatalities each year are caused by air pollution in recent years.  Up to 4 million of these fatalities have been attributed to in-door pollution; primarily due to wood smoke and improper/inadequate building-structure ventilation systems.

Essentially all Developed Countries recognized the importance of preventing in-door smoke exposure hazards from burning wood and standardized building construction design standards (or codes) to include proper ventilation (chimneys/smoke stacks) beginning almost a 100 years ago.  The problem of wood smoke has evolved to be primarily a out-door concern issue in Developed Countries today, particularly in more densely populated neighborhoods during stagnate cold weather (winter) conditions where the smoke does not readily dissipate.   The hazards of smoke are typically mitigated by dissipating or reducing the smoke concentration downwind of the wood burning source.  This hazard mitigation process is commonly referred to as a ‘solution-by-dilution’ process, which reduces the hazardous smoke concentration and mitigates the severity of adverse health effects.

The health hazards of wood smoke can go beyond just the soot or PM concerns.  Wood smoke can contain many other hazardous pollutants that are potentially very harmful; and vary depending the combustion technology used and the wood quality (green vs. seasoned/dried/processed).

Reducing Firewood Pollution – The amount PM pollutants contained in the combustion products (exhaust) from burning wood and other fuels varies depending on the type of combustion technology used and heating fuel consumed.  For example, refer to the following diagram.


As illustrated above, the level of PM emissions vary with heater technologies and the type of fuel consumed.  Clearly the cleanest source of indoor heat would be electric heaters; directly.  However, this is only true overall if the electric power came from 100% hydro, nuclear, wind and/or solar generated electric power.  But, since nearly all power supplied is connected to centralized grids, the (indirect) PM emissions from fossil fuel or biomass power plants will be somewhat greater than ‘zero’ (as illustrated above) depending on the power plant’s environmental controls design and emissions-location relative to nearby Residents.

Today natural gas is the most plentiful and cleanest fuel for electricity generation and for most forms of heating fuels.  One obvious solution to reducing wood smoke PM would be to replace wood heaters with cleaner and generally more cost effective natural gas heaters.  Natural gas, however, is not available throughout the U.S.  In many regions the only available alternatives to wood and natural gas is LPG or petroleum No.2 Fuel Oil.  But, none of these alternative heating fuels are renewables and directionally emit much greater levels of carbon dioxide than renewable wood.  If minimizing carbon emissions is a Consumer and Government high priority, what are the options to substantially reducing the PM emissions from burning (green) wood to generate needed heat?

Future Of Cleaner Burning Renewable Wood – The smoke pollution from wood can be very effectively reduced by at least 80% by replacing obsolete fireplaces and heaters with ‘certified EPA’ woodstoves or fireplace inserts.  To further support such an improvement the EPA recently initiated a new regulation development process to upgrade Residential wood heaters.  This new regulation will build on a past regulation, which initiated the development of the first ‘EPA certified’ Residential/Commercial heaters back in 1988.

The consumption of renewable wood has been in decline within the U.S. since the early 1980’s.  This decline has been due to a combination of displacing wood fuels with natural gas, LPG and electric heaters, and, improved buildings energy efficiency and significant increases in other renewables such as geothermal heat.  The new cleaner wood heaters proposed by the EPA could significantly increase the costs of all new wood heaters, which could be unaffordable for lower income Residents.  Higher cost wood stoves/heaters could make keeping and operating obsolete/dirtier wood burning stoves/heaters necessary for a large percentage of the population that currently relies wood for home heating.  While the economic impacts of the pending regulations may negatively impact some lower income Residents, the EPA predicts the added thermal efficiency and cleaner new wood heaters will benefit users (and their neighbors) at levels magnitudes greater than the added new heater costs.

If the added costs for cleaner, more efficient woodstoves prove to be excessive, this factor will not only become a burden for lower income Families, but could also lead to further decline in renewable wood consumption within the U.S.  Wood heat must then be replaced by alternative heating sources, which overwhelming will likely be natural gas, LPG or petroleum heating oil.  This possible decrease in renewable wood fuels and increase of fossil fuels consumption will not help reduce future U.S. carbon emissions.

So, what other reasonable options exist to maintaining and possibly increasing the cost effectiveness, consumption and sustainability of cleaner renewable wood in the future?  This question will be addressed in a future TEC “Renewable Wood Fuels (Part 2)” Post.  To help make this future TEC Post more comprehensive, your ideas and comments will be appreciated.