Materials Characterization Paper 

In Support of the 

Proposed Rulemaking – 

Identification of Nonhazardous Secondary Materials That Are Solid Waste

Biomass - Agricultural Residues and Food Scraps 

March 18, 2010 

============================================================== 

1. Definitions of Agricultural Residues and Food Scraps 

Agricultural residues include crop residues remaining in fields after harvest (primary residues) 

and processing residues generated from the harvested portions of crops during food, feed, and 

fiber production (secondary residues). 

Food scraps are generated at all stages of the food system including farming, storage, processing, 

wholesaling, retail, and consumption (Scott Kantor et al. 1997). Food scraps, broadly defined, 

include both the portion of harvested crops and livestock that does not enter the retail market and 

the portion of food discarded by retailers and consumers. In this paper, food scraps generated by 

retailers and consumers are not considered because they enter the waste stream as municipal 

solid waste (MSW) (EPA 2006, Simmons et al. 2006). Food scraps generated in the manufacture 

and distribution of food are produced through spoilage, removal of unusable portions, discard of 

substandard products, and packaging failure. 

2. Annual Quantities of Agricultural Residues and Food Scraps Generated and Used 

(1) Sectors that Generate Agricultural Residues and Food Scraps: 

• NAICS 111: Crop Production 

• NAICS 11511: Support Activities for Crop Production 

• NAICS 311: Food Manufacturing 

• NAICS 312 Beverage and Tobacco Product Manufacturing 

(2) Quantities and Prices of Agricultural Residues and Food Scraps Generated: 

• Current annual production of agricultural residues from major crops is around 500 

million dry tons (Milbrandt 2005, Haq and Easterly 2006). These crops include 

barley, canola, corn, cotton, dry beans, flax, oats, peanuts, peas, potatoes, rice, 

rye, safflower, sorghum, soybeans, sugarcane, sunflowers, and wheat, among 

others. The fraction of this amount that can be removed from fields in a 

sustainable manner (i.e., while maintaining cropland fertility and quality) varies 

widely from 113 million tons by Perlack et al. (2005) to 173 million tons by 

Milbrandt (2005)). Newer analyses soon to be published tend to be even lower. 

• Sugarcane production from 2005 through 2007 averaged 13.5 million tons of cane 

(ERS 2008). This yielded approximately 3.8 million tons of bagasse assuming 

0.28 lbs. of bagasse produced per pound of cane (Macedo et al. 2004).
Biomass - Agricultural Residues and Food Scraps 

 

• Domestic production of peanut hulls was approximately 0.27 million tons in 1999 

(Özyurt and Realff 2002). 

• Total quantities of secondary agricultural residues and industrial food scraps 

produced on an annual basis are not readily accessible from the available 

literature. 

• Further analysis could be used to derive an estimate of industrial food scrap 

production by applying known conversion factors for weight reductions that occur 

as crops and livestock are processed into retailed food products. These conversion 

factors range from 5 percent for fresh fruit to 30 percent for meat, poultry, and 

processed vegetables (Scott Kantor et al. 1997, Jones Putman and Allshouse 

1999). 

• Around 75 million tons, or two-thirds, of the 113 million tons of sustainably 

harvestable primary agricultural residue estimated by Perlack et al. (2005) is corn 

stover, which is composed of corn stalks, husks, and shelled cobs. Processing 

facilities experience marginal feedstock costs from $54 to $84 per dry ton 

depending on the fraction of stover collected from the field and transportation 

distance (Petrolia 2008). 

• Haq and Easterly (2006) provide a detailed list of supply curves for primary and 

secondary agricultural residues. These could be updated for current collection and 

transportation costs given recent increases in energy prices. 

(3) Trends in Generation of Agricultural Residues and Food Scraps: 

• Total primary agricultural residue production fluctuates with 1) the amount of US 

land in crop production and 2) the relative proportion of crops, each with its own 

residue production rate. Current trends suggest that higher food prices will drive 

additional land into crop production (Secchi and Babcock 2007), thereby 

potentially increasing residue production. 

• Domestic sugarcane production has decreased over the past decade (ERS 2008), 

thus reducing the total amount of secondary agricultural residue (bagasse) 

combusted in sugar mills. Conversely, new methods for utilizing sugarcane 

“trash,” or field residue, may increase total biomass use from this crop (Macedo et 

al. 2008). 

• Trends in other secondary agricultural residue and food scraps are not readily 

available. 

3. Uses of Agricultural Residues and Food Scraps 

(1) Combustion Uses of Agricultural Residues and Food Scraps:

• In 2007, approximately 6.0 million tons of agricultural residues were burned as 

fuel, 92 percent of which (Btu basis) provided useful thermal output (EIA 2008). 

The remaining 8 percent was used to produce electricity. Around 71 percent of 

total agricultural residues combusted (Btu basis) were secondary residues used in 

the food processing industry, mostly sugarcane bagasse at sugar mills (EIA 2007). 

The remaining 29 percent was used in the Agriculture, Forestry, and Mining, and 

the Paper and Allied Products industries (EIA 2008). 

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Biomass - Agricultural Residues and Food Scraps 

 

• The combustor survey database developed by EPA for the 2009 proposal of the 

Commercial and Industrial Solid Waste Incinerator (CISWI) standards and the 

Industrial Boilers Maximum Achievable Control Technology (MACT) standards 

indicates that the sources surveyed for these rules annually combust at least 3 

million tons of food scraps and agricultural residues (EPA 2009).1,2

 In addition, 

units affected by these rules reported combusting approximately 3.4 million tons 

of material described in general terms as biomass or bio-liquids in the database.3

• An emerging market for corn stover and other primary and secondary agricultural 

residues is for use as a heat and power source for the production of corn and 

cellulosic ethanol (Morey et al. 2006, Farrell and Gopal 2008). 

(2) Non-Combustion Uses of Agricultural Residues and Food Scraps:

• Primary agricultural residues play an important role in maintaining cropland 

production. Removing them can increase erosion, reduce crop productivity, and 

deplete soil carbon and nutrients (Graham et al. 2007). Recent work has shown 

that cropland is particularly susceptible to loss of soil carbon with increased 

residue removal (Wilhelm et al. 2007). 

• Primary agricultural residues are often harvested to provide animal bedding. 

• Certain secondary agricultural residues can be spread upon cropland as soil 

treatments. Such is the case with peanut hulls, where a majority in Georgia (40 

percent of US production) are used in granular carriers for lawn and garden 

insecticide and fertilizer products, with the remainder sold for livestock feed and 

bedding (Özyurt and Realff 2002). 

• Non-combustion uses for food scraps can include composting. 

(3) Quantities of Agricultural Residues and Food Scraps Landfilled: 

• Primary agricultural residues are not landfilled to an appreciable extent. 

• Data on the quantity of food scraps landfilled are not readily accessible in the 

available literature. Further inquiry may reveal these amounts. For example, 

Annex 3 to the “Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-

2006” report describes a methodology (Pages A-179 and A-180) that was 

followed to estimate methane generation at industrial landfills (EPA 2008). This 

included gathering information on food processing wastes diverted to landfills. 

 1

 The categories of material in the combustion database that we assume are agricultural residues or food 

scraps are (1) animal fat/oils/tallow, (2) bagasse, and (3) plant-based agricultural residue. 

2

 Although we report this quantity from the combustion database as a tonnage, the database includes 

material quantities expressed in terms of heating values (Btu). To express this information as a tonnage, we 

assumed heating values of 4,848 Btu/lb, 6,065 Btu/lb, and 6,450 Btu/lb for animal fat/oils/tallow, bagasse, and plantbased agricultural residues, respectively, based on the various thermal values presented in this paper. 

3

 To convert the total Btu values reported for these materials to tonnages, we assumed a thermal value of 

6,000 Btu/lb, based on the range of thermal values reported for biomass materials in this paper, the manure and 

gaseous fuels materials characterization paper, and the materials characterization paper for forest derived biomass 

and pulp and paper residues. 

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Biomass - Agricultural Residues and Food Scraps 

 

(4) Quantities of Agricultural Residues and Food Scraps Stockpiled/Stored:

• Primary agricultural residues tend to degrade rapidly after harvest and are largely 

decomposed by the following planting season. 

• Quantities of secondary agricultural residues and food scraps stockpiled or stored 

are unknown. 

Exhibit 1: Overview of Generation and Use of Agricultural Residues and Food Scraps 

Annual Quantity 

Used as Fuel Annual 

Quantity 

Generated 

Cement 

Kilns Other 

Annual 

Quantity 

Landfilled 

Annual 

Quantity in 

Other Uses 

Total 

Quantity 

Stockpiled Commodity 

---------- Million Tons -----------

Primary Ag. Residues 500a N/I 0 327–387b 0

Secondary Ag. Residues N/I N/I 6.0 

Combined N/I N/I N/I

Food Scraps N/I N/I N/I N/I N/I N/I

Notes: aTotal primary agricultural residue from major crops. bMinimum amount needed to remain on land to 

maintain soil fertility and moisture, and prevent erosion and carbon loss. 

N/I = not identified 

4. Management and Combustion Processes for Agricultural Residues and Food Scraps 

(1) Types of Units Using Agricultural Residues and Food Scraps:

• The discussion for this section centers on the use of bagasse in sugar mills. 

Bagasse is burned in fuel cells, horseshoe boilers, and spreader stoker boilers 

(EPA 1996). Other emerging technologies of combusting agricultural residues and 

food scraps are described in Farrell and Gopal (2008). 

(2) Sourcing of Agricultural Residues and Food Scraps:

• Agricultural residues and food scraps are generated from harvesting crops and 

processing crops and livestock into food products for retail sale. 

• Bagasse is produced when chopped and crushed cane is milled through a series of 

grooved rolls, thereby releasing cane juices. 

(3) Processing of Agricultural Residues and Food Scraps: 

• Bagasse does not require special processing before being combusted. 

• Public comments from BlueFire Ethanol Fuels, Inc. in response to the Advanced 

Notice of Proposed Rulemaking (ANPRM) describe the process by which lignin 

is produced. The process involves a transformation of virtually any cellulosic feed 

into fermentable sugars, in which the biomass is separated into two main 

constituents: (1) cellulose and hemicellulose and (2) lignin. The cellulose and 

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Biomass - Agricultural Residues and Food Scraps 

 

hemicellulose are converted to sugars, fermented, and purified into products. The 

lignin is separated by filtering and pressing and used as fuel to obtain steam for 

the production facility using an on-site boiler (Sumait 2009). 

(4) State Status of Agricultural Residues and Food Scraps:

• As of September 2006, approximately 50 percent of states had renewable fuels 

portfolio standards requiring that varying percentages of power generated within 

the individual states come from alternative fuels (including biomass) by a 

designated future date; several more states have enacted such regulations since 

then (DOE 2006).4

5. Agricultural Residues and Food Scraps Composition and Impacts 

(1) Composition of Agricultural Residues and Food Scraps:

• Most agricultural residues have a high heating value of between 12.9 and 14.6 

million btu/ton (6,450 to 7,300 btu/lb) (Wright et al. 2006). Air-dried biomass is 

typically around 15 to 20 percent moisture. 

• Bagasse has an approximate high heating value of 12.1 million btu/ton (6,065 

btu/lb), (Wright et al. 2006). As burned in sugar mills (45 to 55 percent moisture 

by weight), its heating value is between 6.0 and 8.0 million btu/ton (3,000 and 

4,000 btu/lb) (EPA 1996). 

• The high heat value of peanut hulls is 16.0 million btu/ton (8,031 btu/lb) (Bain et 

al. 2003). 

• Public comments submitted by BlueFire Ethanol Fuels, Inc. in response to the 

ANPRM indicate that lignin has a heating value of between 7,600 and 8,000 

Btu/lb (Sumait 2009). In addition, public comments from Hawaiian Commercial 

and Sugar Company state that cooking oil has a thermal value of 16,000 to 17,000 

Btu/lb (O’Keefe 2009). 

• The heating value of food scraps is likely to be close to the biogenic portion of 

MSW, which has an average heat content (moisture content unknown) of 9,696 

btu/ton (4,848 btu/lb). 

(2) Impacts of Agricultural Residues and Food Scraps:

• Use of biomass as a substitute for coal in an existing power plant reduces SO2, 

NOx, and other emissions (Hong 2007 p.13). 

• Combustion of corn stover can yield NOx emissions of 0.22 pounds per MMBtu 

and SOx emissions of 0.10 pounds per MMBtu (De Kam 2007 p.12). 

• Data on emissions from combustion of food scraps are not readily available. 

• EPA’s AP-42 includes estimated emission factors for bagasse combustion in 

boilers at sugar mills using a variety of control technologies. For example, for 

particulate matter (PM) of unspecified size, bagasse combustion emits between 

0.2 and 2.2 pounds per MMBtu, depending on the type of control technology 

 4

 The summary table in the reference does not always specify which types of biomass are included, 

however, it is likely that agricultural residues are included. For example, Nevada includes “agricultural wastes.” 

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Biomass - Agricultural Residues and Food Scraps 

 

utilized. Estimated emissions of PM-10 are 0.19 lbs./MMBtu when using wet 

scrubber controls. Uncontrolled NOx emissions are 0.17 lbs./MMBtu, while 

uncontrolled CO2 emissions exceed 220 lbs./MMBtu. Note that EPA rates the 

data quality of emission factors for controlled PM and CO2 as high (i.e., based on 

repeated tests at multiple sites), while the remaining factors are less reliable 

estimates (EPA 1996, p. 1.8-4). 

(3) Lifecycle Emissions Impacts: 

Use of agricultural residues or food scraps as a replacement for traditional primary 

fuels eliminates the environmental impacts associated with extraction and processing 

of traditional fuels. In addition to the emissions impacts of combustion described 

above, Exhibit 2 lists the quantities of the total cradle-to-gate emissions for these 

fuels based on typical processes in the United States in the late 1990s. 

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Biomass - Agricultural Residues and Food Scraps 

 

Exhibit 2: Emissions from Extraction and Processing of Traditional Fuels (Lb./MMBtu) 

Pollutant Coal 

Distillate 

Fuel Oil 

Residual 

Fuel Oil Wood 

Natural 

Gas 

Criteria Pollutants 

PM2.5 - - - - -

PM10 - - - - -

PM, unspecified 0.246 0.012 0.012 6.67x10-4 0.004

NOx 0.022 0.061 0.062 0.08 0.117

VOCs 0.008 0.361 0.365 - 0.515

SOx 0.022 0.186 0.187 0.003 1.913

CO 0.017 0.046 0.046 0.022 0.223

Pb 2.60x10-7 1.01x10-6 1.00x10-6 - 2.72x10-7

Hg 8.17x10-8 1.87x10-7 1.87x10-7 - 7.18x10-8

Greenhouse Gases

CO2 3.9 19 19.1 - 15.3

CH4 0.451 0.029 0.029 - 0.369

N2O 1.63x10-5 2.01x10-5 2.07x10-5 - 1.17x10-5

MTCO2E/MMBtu 0.006 0.009 0.009 - 0.01

Source:

Franklin Associates 1998. 

Note:

“-” signifies data not available; may equal zero. 

The emission information presented in this table is derived from Life Cycle Inventory (LCI) data, 

as compiled by Franklin Associates. LCI data identifies and quantifies resource inputs, energy 

requirements, and releases to the air, water, and land for each step in the manufacture of a product 

or process, from the extraction of the raw materials to ultimate disposal. The LCI can be used to 

identify those system components or life cycle steps that are the main contributors to 

environmental burdens such as energy use, solid waste, and atmospheric and waterborne 

emissions. Uncertainty in an LCI is due to the cumulative effects of input uncertainties and data 

variability. 

There are several life cycle inventory databases available in the U.S. and Europe. For this paper, 

we applied the most readily available LCI database that was most consistent with the materials and 

uses examined. These LCI data rely on system boundaries as defined by Franklin Associates, as 

described in the documentation for this database, available at: 

http://www.pre.nl/download/manuals/DatabaseManualFranklinUS98.pdf. 

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Biomass - Agricultural Residues and Food Scraps 

 

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