Biomass Research

The Forest Operations Unit of the Southern Research Station (SRS) has been involved in biomass-related research since the late 1970's. Biomass is a source for biofuels as an alternative to gasoline and other oil-based products. High energy demands have created a need to further develop economically viable ways to harvest this renewable resource. Therefore, our studies in this area continue.

Our Research Unit has nine primary research topic areas related to biomass: biomass harvesting systems; economic analysis; bundling; individual machines; proto-type machines; energywood chipping systems; environmental considerations; short rotation woody crop production; and drying, storing, transporting & roll splitting.

For more information on mechanical fuel reduction treatments visit our mastication webpage.

Biomass Research Topics

Recent Studies

Recent Outputs

Biomass Moisture Content

Biomass and Heat Value

Presentations

Links

References

Recent Studies

Using a Round Baler to harvest understory biomass
Seasonal Effects on Transpirational Drying of Loblolly Pine
Performance of a slash bundler in the Southeast

Recent Outputs

Forest Residues Bundling Project CD

During the summer of 2003, the USDA Forest Service conducted an evaluation of biomass bundling for forest residue extraction. This CD provides a report of the project results, a video documentary project record, and a collection of images from the project. To obtain a copy of the CD just complete and submit the order form below and one will promptly be mailed to you. Additional information is available at: http://www.fs.fed.us/forestmanagement/WoodyBiomassUtilization/

Bundler Project CD Order Form

Biomass Publications from the Forest Operations Research Unit: A Synthesis

Our unit has been studying biomass-related topics since 1977. This CD aids the reader by organizing these publications in one easy-to-use CD. Included on the CD are an executive summary, two bibliographies, individual publications (in PDF format), and a keyword listing. The types of publications on the CD consist of presentation reports, published reports, portions of books, and master's theses.

The CD can be accessed by visiting: http://www.srs.fs.usda.gov/pubs/biomass_cd

To obtain a copy of the CD simply complete and submit the order form below and one will promptly be mailed to you, or contact Dana Mitchell, Research Engineer, at 334-826-8700 or danamitchell@fs.fed.us.

Biomass Publications CD Order Form

Forest Residue Trucking Simulator (version 5)

The Forest Residues Transportation Model (FoRTS) is a spreadsheet calculator designed to help you compare alternative methods of moving biomass from the forest to a wood-using facility. It will let you:

estimate loading and hauling costs for different combinations of equipment
evaluate the best mix (numbers and types) of equipment
compare different hauling routes
examine reloading, or two-stage hauling opportunities

You can use default values for basic comparisons or input your own numbers to examine specific projects.

The model will NOT give actual costs for these operations because it does not include factors such as profit and overhead. It is intended to represent a relative comparison among options.

To learn more about the program or to obtain a copy of the spreadsheet, simply download the following files.

FoRTS Overview (1.5 Mb pdf file)

FoRTS v5 (1.7 Mb Excel file)

Biomass Moisture Content

The moisture content of biomass affects the gross weight of the material that is being handled. Green material will have a higher density than drier material because of the extra water weight in the cells of the wood. In biomass markets, it is important for all parties to have a common understanding of the dry mass of material that is being sold or processed. Generally biomass loads are sampled for moisture content and then converted to a dry-basis measure such as "bone dry tons" or "bone dry units."

A bone dry ton (bdt) is an amount of material that weighs 2000 lbs when it is dry. A bone dry unit (bdu) is an amount of material that weighs 2400 lbs when it is dry. Bone dry tons are used in some biomass markets, particularly where logs are being processed. Bone dry units are found in other markets, particularly where the predominant form is chips or hog fuel. Another term used in some residue transactions is the "unit" or "gravity packed unit" (GPU). A GPU is the amount of material in a volume of 200 cubic feet. This volume measure should not be confused with the "cunit" or a measure that is 100 cubic feet of solid wood. For a full description of wood measurements and conversions, see Forest Products Measurements and Conversion Factorsby David Briggs.

Moisture content measurement can be done in several ways. Electronic moisture meters can measure moisture content indirectly. More exact measurement requires actually drying a sample of material and determining the dry weight and the weight of water that was originally in the sample. The calculation of moisture content can be done in one of two ways:

%MCod = wt. of water / wt. of wood * 100 (This is MC oven-dry basis)

%MCwb = wt. of water / (wt. of wood + wt. of water)*100 (This is MC wet basis)

You can convert %MCod to %MCwb using the formula:

%MCwb = %MCod*100 / (100 + %MCod).

To go the other way us the formula:

%MCod = %MCwb*100 / (100 - %MCwb)

To have this calculation done for you and see this illustrated graphically, you can download the Moisture Content Converter (Excel file).

Biomass and Heat Value

A very useful parameter to know when dealing with biomass is the heat value, or heat of combustion, which is defined as the total amount of heat obtainable from ovendry material when burned in an enclosure of constant volume, allowing no deductions for heat losses (Koch, P. 1985. Utilization of hardwoods growing on southern pine sites. U.S. Dep. Agric. For. Serv., Agric. Handb. 605 3710 p. 3 vol.). Since biomass is mainly used as a fuel source, it is helpful to know the fuel potential of the material being used. A number of variables affect heat value, the most important being moisture content, species, and the portion of the tree being used (stemwood, branchwood, bark). Heat value is normally expressed in Btu's/ovendry pound. A Btu is defined as the heat required to raise the temperature of 1 lb of water from 63 deg F to 64 deg F (Serway, R.A., 1983. Physics for scientists and engineers with modern physics, 2nd edition, p. 427. Saunders College Publishing). Heat values for some common hardwoods are listed in Table 1. Heat values for some materials derived from southern pine trees are shown in Table 2.

Table 1. Heat of combustion (Btu/ovendry pound) of stems and branches of 6-inch trees of 22 hardwood species growing on southern pine sites (data from Manwiller).

Species	Stem-wood	Stem-bark	Branch-wood	Branch-bark
Ash, green	7,695	7,472	7,727	7,606
Ash, white	8,033	7,695	8,013	7,816
Elm, American	7,770	6,840	7,857	6,904
Elm, winged	7,917	7,019	7,869	6,889
Hackberry	7,882	7,147	7,867	7,141
Hickory, sp	8,183	7,586	7,931	7,259
Maple, red	7,846	7,595	7,829	7,384
Oak, black	7,680	7,642	7,692	7,847
Oak, blackjack	7,739	7,766	7,739	7,907
Oak, cherrybark	7,848	7,582	7,737	7,655
Oak, laurel	7,828	7,897	7,653	7,806
Oak, northern red	7,791	7,879	7,776	7,926
Oak, post	7,889	7,191	7,845	7,728
Oak, scarlet	7,798	8,041	7,673	7,894
Oak, Shumard	7,789	7,970	7,745	7,913
Oak, southern red	7,919	7,983	7,839	7,798
Oak, water	7,876	7,930	7,833	7,918
Oak, white	7,676	7,328	7,507	7,574
Sweetbay	7,736	7,822	7,802	7,886
Sweetgum	7,667	7,200	7,690	7,214
Tupelo, black	7,867	7,788	7,814	8,176
Yellow-poplar	7,774	7,696	7,811	7,666
Average	7,827	7,593	7,784	7,632

Table 2. Heat of combustion (Btu/ovendry pound) of various materials from southern pine trees (data from Howard).

Material	Average	Range
Resin		14,625 to 16,250
Charcoal	12,335	11,225 to 12,740
Needles	9,030	8,935 to 9,105
Loblolly pine stemwood	8,600	8,310 to 9,352
Earlywood	8,610	8,470 to 8,760
Latewood	8,585	8,385 to 8,755
Rootwood	8,605	8,560 to 8,680
Tops (bark & wood at 1" top)	8,395	8,015 to 8,745
Old cones	8,130	8,085 to 8,190
Kraft black liquor	5,965	5,820 to 6,130