Materials Characterization Paper In Support of the Proposed Rulemaking – Identification of Nonhazardous Secondary Materials That Are Solid Waste Biomass - Agricultural Re sidues and Food Scraps

March 18, 2010

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1. Definitions of Agricultural Residues and Food Scraps

Agricultural residues include cr op residues remaining in fields af ter harvest (primary residues) and processing residues generated from the harvested portio ns of crops during food, feed, and fiber production (secondary residues).

Food scraps are generated at all stages of the food system incl uding farming, storage, processing, wholesaling, retail, and consumption (Scott Kantor et al . 1997). Food scraps, broadly defined, include both the portion of harvested crops and li vestock that does not ente r the retail market and the portion of food discarded by reta ilers and consumers. In this paper, food scraps generated by
retailers and consumers are not considered beca use they enter the waste stream as municipal solid waste (MSW) (EPA 2006, Simmons et al. 2006). Food scraps genera ted in the manufacture and distribution of food are produc ed through spoilage, removal of unusable portions, discard of substandard products, and packaging failure.

2. Annual Quantities of Agricultural Residu es and Food Scraps Generated and Used

(1) Sectors that Generate Agricultur al Residues and Food Scraps:

• NAICS 111: Crop Production

• NAICS 11511: Support Activi ties 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 agricultura l 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, pean uts, peas, potatoes, rice, rye, safflower, sorghum, soybeans, suga rcane, 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 fe rtility 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 Re sidues and Food Scraps

• Domestic production of peanut hulls wa s approximately 0.27 million tons in 1999 (Özyurt and Realff 2002).

• Total quantities of seconda ry agricultural residues a nd 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 fact ors 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 stal ks, husks, and shelled cobs. Processing facilities experience margin al feedstock costs from $54 to $84 per dry ton depending on the fraction of stover colle cted 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 c ould be updated for cu rrent collection and transportation costs given recent in creases in energy prices.

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

• Total primary agricultural re sidue 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 s uggest that higher food prices will drive additional land into crop production (Secchi and Babcock 2007), thereby potentially increasing residue production.

• Domestic sugarcane production has decr eased over the past decade (ERS 2008), thus reducing the total amount of sec ondary agricultural residue (bagasse) combusted in sugar mills. Conversely, new methods for utilizing sugarcane “trash,” or field residue, may increase to tal 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 Agricultur al 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 suga rcane bagasse at sugar mills (EIA 2007). The remaining 29 percent was used in th e Agriculture, Forestry, and Mining, and the Paper and Allied Products industries (EIA 2008).

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• The combustor survey database devel oped 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 s econdary 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 Agricult ural Residues and Food Scraps:

• Primary agricultural residues play an important role in maintaining cropland production. Removing them can increas e erosion, reduce crop productivity, and deplete soil carbon and nutrients (Graham et al. 2007). Recent work has shown that cropland is particularly susceptib le to loss of soil carbon with increased residue removal (Wilhelm et al. 2007).

• Primary agricultural residue s are often harvested to provide animal bedding.

• Certain secondary agricultu ral 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 pr oducts, 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 Resi dues and Food Scraps Landfilled:

• Primary agricultural residues are not la ndfilled to an appreciable extent.

• Data on the quantity of food scraps la ndfilled are not readily accessible in the
available literature. Furt her inquiry may reveal th ese amounts. For example, Annex 3 to the “Inventory of U.S. Gr eenhouse 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 proces sing 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 (B tu). 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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(4) Quantities of Agricultural Residues and Food Scraps Stockpiled/Stored:

• Primary agricultural residues tend to degrade rapidly afte r harvest and are largely decomposed by the following planting season.

• Quantities of secondary agri cultural residues an d food scraps stockpiled or stored
are unknown.

Exhibit 1: Overview of Generation and Us e 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 To ns -----------

Primary Ag. Residues 500 a N/I 0 327–387 b 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 : a Total primary agricultural residue from major crops. b Minimum 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 fo r Agricultural Residues and Food Scraps

(1) Types of Units Using Agricultur al 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 agricu ltural residues and food scraps are described in Farrell and Gopal (2008).

(2) Sourcing of Agricultural Residues and Food Scraps:

• Agricultural residues and food scraps ar e generated from ha rvesting crops and processing crops and livestock in to food products for retail sale.

• Bagasse is produced when chopped and crus hed 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 pr ocessing before being combusted.

• Public comments from BlueFire Ethanol Fu els, Inc. in respons e to the Advanced Notice of Proposed Rulemaking (ANPRM) describe the process by which lignin is produced. The process involves a transfor mation 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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hemicellulose are converted to sugars, fe rmented, 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 pe rcent of states had renewable fuels portfolio standards requiring that varying percentages of power generated within
the individual states come from alte rnative fuels (including biomass) by a designated future date; several more stat es 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 hi gh 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 be tween 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 Etha nol Fuels, Inc. in response to the ANPRM indicate that lignin has a h eating 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 likel y to be close to the biogenic portion of MSW, which has an average heat cont ent (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 f ood scraps are not readily available.

• EPA’s AP-42 includes estimated emissi on 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 alwa ys 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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utilized. Estimated emissions of PM-10 are 0.19 lbs./MMBtu when using wet
scrubber controls. Uncontrolled NO
x emissions are 0.17 lbs./MMBtu, while
uncontrolled CO 2 emissions exceed 220 lbs./MMBtu. Note that EPA rates the data quality of emission factors for controlled PM and CO 2 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 a ssociated with extraction and processing
of traditional fuels. In addition to the emissions impacts of combustion described above, Exhibit 2 lists the quant ities of the total cradle-t o-gate emissions for these fuels based on typical processes in th e United States in the late 1990s.

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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

CO 2 3.9 19 19.1
- 15.3

CH 4 0.451 0.029 0.029
- 0.369

N 2 O 1.63x10 -5 2.01x10 -5 2.07x10 -5

- 1.17x10 -5

MTCO 2 E/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 st ep 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 cycl e steps that are the ma in 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 ava ilable 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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