By Russell Martin
Renewable energy is rapidly becoming a hot button topic among energy producers, environmentalists, end-use energy consumers, and other various groups. The topic is intriguing, promising, and puzzling. This review will introduce and briefly explain biomass, biofuels, and bioenergy production according to the Intergovernmental Panel on Climate Change definitions (IPCC 2007) followed by a projected outlook for the future production of biomass that can be converted into bioenergy on a per state basis using the 2007 Natural Resource Conservation Service’s Natural Resource Inventory and the projections from the 2005 Billion Ton Report. The projected outlook is intended to give readers an idea of the potential individual states have for producing biomass from forest and agricultural land resources according to the Billion Ton Report (USDOE/USDA 2005) and the Natural Resource Inventory (NRCS 2007).
The production of biomass is the first step to producing bioenergy. Biomass is defined as:
“The total mass of living organisms in a given area or of a given species usually expressed as dry weight. Organic matter consisting of, or recently derived from, living organisms (especially regarded as fuel) excluding peat. Biomass includes products, by-products and waste derived from such material. Cellulosic biomass is biomass from cellulose, the primary structural component of plants and trees.” – IPCC 2007
An alternative name for biomass used to produce bioenergy is a “feedstock.” The main categories of feedstocks are: oil seed crops, grains, sugar crops, and agricultural residues, trees, grasses, and algae (Pena 2008). The last category containing trees and grasses is commonly referred to as cellulosic biomass. Different parts of the plants are used depending on the category of feedstock. For example, fats and oils from oil seed crops, such as soybeans, can be directly converted to biodiesel using the processes of transesterfication or hydrotreating (for more examples see Pena 2008). The product derived from a particular feedstock is dependent on which part of the plant and the conversion process used. The possible products that can be derived from biomass include biodiesel, ethanol, butanol, methane, hydrocarbons, and natural oils, which can be further processed into any number of desirable fuels (Pena 2008).
The production of biofuel is the second step in producing bioenergy. Biofuel is defined as:
“Any liquid, gaseous, or solid fuel produced from plant or animal organic matter. E.g. soybean oil, alcohol from fermented sugar, black liquor from the paper manufacturing process, wood as fuel, etc. Second-generation biofuels are products such as ethanol and biodiesel derived from ligno-cellulosic biomass by chemical or biological processes.” –IPCC 2007
Biofuels are derived from various plant parts and the conversion process used to convert the plant part determines the biofuel that can be produced. Each biofuel displaces different quantities of fossil fuel equivalents. The conversion of biomass to biofuel can also result in by-products, which are usually plant parts and materials that cannot be converted usually due chemical composition.
The final step in the production of bioenergy is the consumption of biofuels to produce electricity, heat, or steam. Bioenergy is defined as “energy derived from biomass (IPCC 2007).” Heat, as a bioenergy, is the form of energy that is used in combustion engines, which we typically associate with biofuel consumption. Unprocessed biomass can also be directly burned to produce heat, as is the case when wood is burned in a fireplace. The previously mentioned by-products can also be directly burned to produce bioenergy in the form of heat.
Currently, there is disconnection in the scientific literature between ecologists and energy experts. Several biomass projection papers for various regions and countries around the world are calling for the production of specific biomass crops, such as hybrid poplars in Canada (McKinney et al. 2006), across an entire country or region with little recognition of the potential impacts of converting non-forest ecosystems to forested biomass production sites or vice a versa. This paper attempts to promote a biomass production projection method that does not require or advocate landuse conversion since landuse change has been shown to be a major contributor to green house gas (GHG’s) emissions, which leads to a “carbon debt” (Fargione et al. 2008).
In April 2005, the US Department of Energy (USDOE) and the US Department of Agriculture (USDA) published a joint report commonly referred to as “The Billion Ton Report (BTR).” The purpose of the report was to identify the technical feasibility of producing a billion tons of biomass annually for use as feedstocks for biofuels and bioenergy, which would potentially displace 30% of our annual petroleum use. This report looked at the production of biomass from two primary landuses, forestland and agricultural land, which are estimated to produce 368 and 998 million dry tons per year respectively by the mid-21st century (USDOE/USDA 2005). Several key assumptions were made concerning the production of biomass from these two landuses in the BTR.
For forestland, the assumptions were:
“All areas not currently accessible by roads were excluded, all environmentally sensitive areas were excluded, equipment recovery limitations were considered, and recoverable biomass was allocated into two utilization groups – conventional forest products and biomass for biofuels and bioenergy products.” -(USDOE/USDA 2005)
For agricultural land, the assumptions were:
”Yields of corn, wheat, and other small grains increased by 50%, the residue-to-grain ratio for soybeans was increased to 2:1, harvest technology was capable of recovering 75 percent of annual crop residues (when removal is sustainable), all cropland was managed with no-till methods, 55 million acres of cropland, idle cropland, and cropland pasture were dedicated to the production of perennial bioenergy crops, all manure in excess of that which can be applied on-farm for soil improvement under anticipated EPA restrictions was used for biofuel, and all other available residues were utilized.” -(USDOE/USDA 2005)
In 2007, the Natural Resource Conservation Service (NRCS) published its Natural Resource Inventory (NRI), which is a statistical survey of natural resource conditions and trends based on data collected in 2003. The inventory breaks down landuse within the United States and identifies patterns and trends in landuse over time (NRCS 2007).
The USDOE/USDA Billion Ton Report estimates that there are approximately 749 million acres of forestland in the United States with 504 million acres considered as timberland, 168 million acres considered as “other” forestland, and 77 million acres of reserved timberland that is off-limits to harvest as parks or wilderness (USDOE/USDA 2005). The 368 tons of biomass per year projection is based on the 504 and 168 million acres, of which approximately 30% is federally owned (USDOE/USDA 2005). The NRCS Natural Resource Inventory estimates that there are approximately 406 million acres of forestland in the United States as of 2003 (NRCS 2007). The discrepancy between these two estimates for landuse is significant, but can largely be attributed to the differences in the number of categories identified and the definitions of those categories in each report. For example, the BTR focuses on the two broad landuse categories of forestland and agricultural land, whereas the Natural Resource Inventory uses nine specific categories including cropland, Conservation Reserve Program (CRP) land, pastureland, rangeland, forestland, other rural land, developed land, water land, and federal land (NRCS 2007). Also, the BTR includes federal forestland in its 672 million acre total whereas the NRI separates all federal land from other landuse types. Because these large discrepancies can be logically explained based on the structure and differing natures of the respective reports, this author assumes that biomass production estimates from the BTR can be projected using the per state landuse estimates from the NRI. In order to calculate biomass production per state, the total projected annual biomass production of 368 million tons will be proportionally distributed to each state with 70% of production (258 million tons) generated from the NRI forestland category and the remaining 30% of production (110 million tons) generated from the NRI federal land category.
The Billion Ton Report estimates that there are approximately 455 million acres of agricultural land in the United States when including all cropland, CRP land, and pastureland (USDOE/USDA 2005). The Natural Resource Inventory estimates that there are approximately 368 million acres of cropland, 32 million acres of CRP land, and 117 million acres of pastureland in the United States for a total of 516 million acres of “agricultural land,” which is an unrecognized category in the NRI (NRCS 2007). Again, the discrepancy between these two estimates is significant but can be attributed to differences in landuse definitions and the nature of the respective reports. Also, this author assumes that the logical explanations of these discrepancies allow for the assumption that biomass production estimates from the BTR can be projected using the per state landuse estimates from the NRI. Since federal lands do not produce biomass crops, all 998 million tons of annual biomass is distributed proportionally across each state’s “agricultural land.”
When reading this projection, please keep in mind that not all land within a landuse category must or will be used for biomass production. This projection takes the projected sum of biomass that could potentially be produced within a given category and spreads that production across the lower contiguous 48 states in proportion to their quantities of current landuse. For example, the 998 tons of agriculture biomass that will be produced will be evenly distributed across all lower 48 states and across the landuse categories present in each state. Texas is projected to produce approximately 88 tons of agricultural biomass per year. This biomass will be produced evenly across all 3 landuses, but it will not require all 45 thousand acres of “agricultural land” to produce it.
As seen in Table 1 (Page1 & Page 2), the projected leader in biomass production will likely be Texas, while Rhode Island will likely produce the smallest quantity of biomass. Also, when viewing this information, please remember that these are estimates of biomass production based on data and information from two separate reports. The purpose of this projection is to give the readers an idea of which states will likely produce the most biomass for use as biofuels and/or bioenergy. It is important for policy makers and infrastructure planners to be aware of this trend since biorefineries should be located as close to the production source as possible in order to reduce production costs and increase efficiency.
This introduction to biomass, biofuels, and bioenergy along with the projected biomass production outlook is intended to introduce the readers to the fundamentals of bioenergy production, provide a reference list for finding additional information (see literature cited), and help them start thinking about the future possibilities of bioenergy production. It is also important that readers, scientists, and policy makers be aware of current landuse practices and ecological factors of a given area when considering biomass production. If you enjoyed this paper, please check back in the following weeks for a follow up report that will discuss the use of native perennial prairie grasses in biomass production.
Fargione, J., J. Hill, D. Tilman, S. Polasky, and P. Hawthorne. 2008 Land clearing and the biofuel carbon debt. Science 319:1235-1238.
International Panel on Climate Change. 2007. Assessment Report 4. Working Group 3 “Mitigation of Climate Change”.
McKenney, D. W., D. Yemshanov, G. Fox, and E. Ramlal. 2006. Using bioeconomic models to assess research priorities: a case study on afforestation as a carbon sequestration tool. Canadian Journal of Forest Research 36:886-900.
Natural Resource Conservation Service. 2007. Natural Resource Inventory.
Pena, N., Pew Center on Global Climate Change. 2008. Biofuels for Transportation: A Climate Perspective.
United States Department of Agriculture and United States Department of Energy. 2005. Biomass as Feedstock for a Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply.