2,000 tons of biomass per acre?

From Smokey Wire member Roy Anderson, posted with his permission:

A week or so ago, I read the article linked below about wildfire in California.  In the first few lines it states, “The U.S. Forest Service estimates that dead stands in the Creek fire contain 2,000 tons of fuel per acre”.

2,000 tons of biomass per acre is higher than I’m used to seeing when looking at USFS FIA Data across other parts of the US West….higher by an order of magnitude for average stands.  For example, as a rough calculation, assume a stand averages 100 trees per acre and 24” DBH (pretty nice timber!).  This would mean that each tree in the stand has about 150 cubic feet of volume (bolewood) or 15,000 cubic feet of bolewood per acre.  Each cubic foot of wood weighs about 60 pounds (green weight), which translates into about 450 tons per acre green weight basis (100 trees/acre x 150 cubic feet per tree x 60 pounds per cubic foot divided by 2000 pounds per ton).  If you double that amount (which I think is very generous) to account for branches needles and all other vegetation it still only adds up to 900 tons per acre on a green weight basis.  An oven dry weight basis would be half of that.   It really makes we wonder if the 2,000 tons per acre figure is accurate?  If so, maybe its caused by accumulation of fuel from dead timber and other vegetation???

Anyway, I’m writing to see if you have an opinion about the accuracy of this?



9 thoughts on “2,000 tons of biomass per acre?”

  1. I also find the 2000 tons/ac exceptionally high. This value did not come from myself. I think it may have come from a report issued by press liaison for the fire, but I do not know exactly where Bettina got the value from.

  2. High indeed! Here is an extract from the report (2019) of a just made retrieval of an FS FIA estimate of the tonnage of biomass per acre of live trees on N.F. land in Fresno and Madera Counties CA. where the Creek Fire is burning. Volume of dead trees is not available
    The estimate of 2,000 tons per acre is impossibly high.

    EVALIDator Version – View report

    Numerator attribute number and description: 0510 Above ground biomass of live trees (at least 1 inch d.b.h./d.r.c), in green short tons, on forest land
    Denominator attribute number and description: 0002 Area of forest land, in acres
    FIADEF as the forest land definition.
    California 062019
    Page variable=None (based on values from the Current inventory).
    Row variable=County code and name (based on values from the Current inventory).

    Ratio estimate: (Tons per ac.)
    County code and name Total National Forest Other
    06019 CA Fresno 102.2460 123.0652 54.9553
    06039 CA Madera 119.8188 160.2614 63.436

  3. I’m hearing anecdotal reports from firefighters on the ground at Creek Fire that they are encountering in excess of 10 feet depth of accumulated liter mats on the ground, some places exceeding 18 feet depth. They don’t expect to extinguish this, even with soaking rains or if buried in snow. It will still be burning next spring. That’s where the 2000 tons per acre is coming from. 43560 sq ft per acre x 10 feet deep x 10 pounds per cubic ft = 2178 tons per acre of litter mats alone, plus the dead trees, plus live trees. By the way, this much fuel will release about 4000 tons per acre of greenhouse gas, equivalent to the annual emissions of roughly 850 cars. The Creek Fire is now beyond 300,000 acres and potentially 255 million car-years of greenhouse gas. Switching everybody to zero emission vehicles isn’t going to solve anything if we don’t deal with forest health first.

  4. I asked Adam Hernandez, a wildland fire technology instructor at Reedley College, Calif., whether 2,000 tons per acre is possible on the Sierra National Forest. Mr. Hernandez was formerly a wildland firefighter and Fuels Specialist on the Sierra NF. He said, “yes this is accurate in many locations. Of course this is broadly speaking.”

  5. So,
    If there are ~ 1000 tons of Biomass/acre, (not 2000 tons),and 16,000,000btu/ton of biomass and 1,000,000 acres of this type of forest are burned yearly on planet earth,
    this equates to 1.6^16 btu/year added to the atmosphere just from biomass.
    Now add oil at 1.6^17,
    Gas, coal, nukes, battery, people renewables etc, etc, etc do that for every year from 1975 to 2019
    (The time NASA said planet earth atmosphere increased 1° F, and what do you think you’ll find?

    DO THE MATH, it’s not hard.

    Then build a heat transfer system for earth’s atmosphere,
    with heat at 630° F and -160° F,
    DT of ~800 ° F.
    U factor of 10 btu/hr ft^2 °F,
    Calculate area of atmosphere at 50,000 miles above sea level.

    Impossible you say?

  6. NO, I do not agree. I am a forester too. My estimate of the burnt biomass and hence converted to CO2 is 100t/acre. Remember that during a forest fire there is a lot of left over wood- in some cases salvageable. In any case, I agree with the overall position that uncontrolled forest fires are a major contributor to CO2 increase on a global case. I did some rough calculations and the CO2 generated from the BC forest fires last year, was more than all the CO generated over a year in Canada by the combustion of fossil fuels.


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