utilization of biomass pyrolysis for energy … sids csd-15 paper.pdf · utilization of biomass...

8
UTILIZATION OF BIOMASS PYROLYSIS FOR ENERGY PRODUCTION, SOIL FERTILITY AND CARBON SEQUESTRATION ROBERT HAWKINS, JON NILSSON, REBECCA OGLESBY AND DANNY DAY Summary of information presented May 7, 2007 at the UN Commission on Sustainable Development Partnerships Fair - Partnership in New Technologies for Small Island Developing States Abstract. New pyrolysis technologies have been developed that allow for carbon sequestration through the production of sustainable energy from biomass (bioenergy). These systems produce charcoal (biochar) and energy in the form of heat, steam, electricity, or liquid fuels. Purified hydrogen can also be produced, allowing production of ammonia and future electric systems that utilize hydrogen (such as hydrogen fuel cells). Pyrolysis energy systems produce more power than they consume, and can supply their own power utilizing waste heat from the system. Therefore, this technology could be deployed without the need for existing energy infrastructure. The biochar is a carbon-based co-product that has value as a soil amendment, containing nutrients such as potassium (K), phosphorous (P), magnesium (Mg) and calcium (Ca). When placed in the soil, an increase in soil organic matter (SOM) is observed, along with increases in crop productivity, water retention, and soil biological activity as well as a decreased fertilizer requirement. Pyrolysis technology can be deployed on a large industrial scale, or on small farm or community scales. In these applications it can produce fuel, heat, electricity and fertilizer from crop residues and wastes. The deployment of new biochar and bio-energy systems creates economic opportunities for local communities through the creation of new businesses that develop to support its infrastructure (suppliers of bio-wastes, manufacturer and distribution of co-products, and related agricultural application services etc.). Due to its adaptability to a wide range of feedstocks, over 60 organizations are now involved in biochar research worldwide. (http://terrapreta.bioenergylists.org/organizations ). Figure 1. Concept of low-temperature pyrolysis bio-energy with biochar sequestration. Typically, about 50% of the pyrolyzed biomass is converted into biochar and can be returned to soil. (Adapted from: Lehmann, J. 2007, Bioenergy in the black. Front Ecol Environ 2007; 5(7): 381–387) Transport Energy Coproducts Industry Biomass - manure - organic wastes - crop residues - wood waste Returned to soil as bio-char Optionally, N2, NOX, SOX, CO2 can be added to increase C sink and nutrient content Pyrolysis Biofuel bio-oil hydrogen Residual Heat

Upload: nguyenliem

Post on 15-Mar-2018

223 views

Category:

Documents


1 download

TRANSCRIPT

UTILIZATION OF BIOMASS PYROLYSIS FOR ENERGY PRODUCTION,

SOIL FERTILITY AND CARBON SEQUESTRATION

ROBERT HAWKINS, JON NILSSON, REBECCA OGLESBY AND DANNY DAY

Summary of information presented May 7, 2007 at the UN Commission on Sustainable Development Partnerships Fair - Partnership in New Technologies for Small Island Developing States

Abstract. New pyrolysis technologies have been developed that allow for carbon sequestration through the production of sustainable energy from biomass (bioenergy). These systems produce charcoal (biochar) and energy in the form of heat, steam, electricity, or liquid fuels. Purified hydrogen can also be produced, allowing production of ammonia and future electric systems that utilize hydrogen (such as hydrogen fuel cells). Pyrolysis energy systems produce more power than they consume, and can supply their own power utilizing waste heat from the system. Therefore, this technology could be deployed without the need for existing energy infrastructure. The biochar is a carbon-based co-product that has value as a soil amendment, containing nutrients such as potassium (K), phosphorous (P), magnesium (Mg) and calcium (Ca). When placed in the soil, an increase in soil organic matter (SOM) is observed, along with increases in crop productivity, water retention, and soil biological activity as well as a decreased fertilizer requirement. Pyrolysis technology can be deployed on a large industrial scale, or on small farm or community scales. In these applications it can produce fuel, heat, electricity and fertilizer from crop residues and wastes. The deployment of new biochar and bio-energy systems creates economic opportunities for local communities through the creation of new businesses that develop to support its infrastructure (suppliers of bio-wastes, manufacturer and distribution of co-products, and related agricultural application services etc.). Due to its adaptability to a wide range of feedstocks, over 60 organizations are now involved in biochar research worldwide. (http://terrapreta.bioenergylists.org/organizations).

Figure 1. Concept of low-temperature pyrolysis bio-energy with biochar sequestration.

Typically, about 50% of the pyrolyzed biomass is converted into biochar and can be returned to soil.

(Adapted from: Lehmann, J. 2007, Bioenergy in the black. Front Ecol Environ 2007; 5(7): 381–387)

Transport Energy Coproducts Industry

Biomass - manure - organic wastes - crop residues - wood waste

Returned to soil as bio-char

Optionally, N2, NOX, SOX, CO2 can be added to increase C sink and nutrient content

Pyrolysis

Biofuel bio-oil hydrogen

Residual Heat

Biomass Pyrolysis Technology

At the 2007 United Nations Commission on Sustainable Development, a new system of converting biomass to energy was presented which can reduce dependence on oil. This technology is called biomass pyrolysis. In this system, biomass is exposed to high temperatures in the absence of oxygen, producing energy and co-products. Although pyrolysis biofuel production represents only a small portion of energy production worldwide (UNDP 2004), it has the potential to generate electricity at a cost lower than any other biomass-to-electricity technology available (Bridgewater et. al. 2002). A main advantage to implementing this technology is that a pyrolysis system can supply its own power and heat by utilizing waste heat from the system, so there is no need to supply power or heat from outside sources (Iwasaki, 2003). Therefore, these systems can be deployed without the need for existing energy infrastructure. With these new advances, well over 15 countries are now involved in commercializing biomass pyrolysis systems (http://terrapreta.bioenergylists.org/company). Recent development by EPRIDA, Inc. have made this technolgy more scaleable to agricultural industries with two sizes of pyrolysis units. The first processes 1-ton of biomass per hour unit and produces 1 mw of electricity, 1 megawatt of usable heat and 300 pounds of charcoal per hour. The second processes 25kg of biomass per hour, producing 25 kw of heat and electricity and 20 pounds of charcoal per hour. The Eprida process was developed through research conducted with the National Renewable Energy Labs, Oak Ridge National Laboratory, the Pacific Northwest National Laboratory, U.S. Dept. of Energy, USDA Agricultural Research Service, University of Georgia and Iowa State University.

The EPRIDA pyrolysis plant located at the Biomass Conversion Center in Athens, GA.

Biomass Pyrolysis vs. Conventional Biomass to Energy Systems

In conventional use of biomass for fuel, biomass is harvested and burned, and like fossil fuels, releases compounds back to the atmosphere. This contributes to increased greenhouse gases. In order for the energy cycle to be truly carbon neutral, an amount of biomass equal to that which was harvested must be re-grown so that the plants can absorb an equivalent amount of CO2. To be a steady fuel supply, biomass crops require an increase in agricultural production, which further depletes soil nutrients and minerals. This reduces the ability to grow biomass in the future. Therefore, although biomass crops are a renewable source of energy, they are not necessarily sustainable. With biomass pyrolysis, what was previously considered agricultural waste (crop residues, wood wastes, manures) can create energy and nutrient enhancing soil supplements. The energy created can be converted into several forms including hydrogen and electricity, which can be used to power small farms or fed back onto the energy grid.

Examples of feedstocks include: coconut husks, corn stover, bean stubble, tobacco stalks, wastes from agricultural processing, wood wastes from manufacturing and lumber industries, demolition wood wastes, short-rotation energy crops, municipal solid waste, manure and sewage (Antal 1982). By using agricultural wastes, biomass pyrolysis does not compete with food production. The Products of Biomass Pyrolysis

The main products generated by biomass pyrolysis are pyrolysis vapors, heat and charcoal (biochar). These outputs can be used in a wide range of applications. 1. Pyrolysis vapors can be condensed to form bio-oil Bio-oil is a complex mixture of oxygenated hydrocarbons and water that can be used as low grade heating fuel. Due to its high density, bio-oil is much more economical to transport than either biomass or hydrogen (Czernik et al., 2007). The heating value of bio-oil is about 40% to 50% of that for petroleum-based fuels (Yaman, 2004) and about 60% of ethanol (Raveendran et al., 1996). Bio-oil can be refined to be used as a source of chemical feedstock for gasoline, can be added to petroleum refinery feedstock or combusted in raw form (Samolada et al., 1998). Biomass pyrolysis allows biomass to be processed at dispersed locations where wastes are generated and bio-oil can be transported to a central refinery or power plant. Cost benefits are significant due to the high price of transporting biomass feedstock over large distances (>30 km). Decentralized production of bio-oil also makes sense since biomass is often generated in rural areas where bio-oil can be processed for use in agricultural machinery. 2. Pyrolysis vapors can be used directly for energy In this scenario it is not necessary to condense pyrolysis vapors into bio-oil to extract the energy. Pyrolysis vapors can be burned directly as fuel for integrated heat and power production, or refined to produce fuels and chemicals such as gasoline, diesel, alcohols, olefins, oxychemicals, synthetic natural gas and high purity hydrogen (Magrini-Bair and others, 2007). If the energy is needed for local use, such as on a small farm, it is better to work with the pyrolysis vapors in this form. 3. Pyrolysis vapors can be treated to produce synthetic gas (syngas) Utilizing steam reforming, pyrolysis vapors can produce a syngas consisting of over 50% hydrogen, plus CO, CO2, and small amounts of methane (Czernik et al., 2007). Since these gases are comprised of hydrocarbons, they should not be emitted into the atmosphere in an unaltered state. Instead they can be converted into a clean burning, mid BTU fuel, similar to natural gas. This can be combusted in existing engines, generators, boilers, and turbines to produce heat, steam and electricity. Syngas is also suitable as a cooking fuel and can substitute for propane or natural gas in uses such as home heating. High purity hydrogen from syngas can be suitable for use in hydrogen engines, fuel cells (Czernik et al., 2007) and for production of ammonia fertilizers. The current largest use of hydrogen in the world today is for the production of ammonia. Utilizing pyrolysis to generate hydrogen could replace natural gas as the primary feedstock required to manufacture ammonia based fertilizers. The production of ammonia using natural gas emits carbon dioxide into the atmosphere and fixes the price of fertilizer to the price of natural gas. Production of ammonia from syngas could change this, allowing the price of fertilizer to become influenced by the lower price of biomass wastes. 4. Pyrolysis syngas can create synthetic liquid fuels Pyrolysis of biomass is one of the leading near-term options for renewable production of hydrogen and has the potential to provide a significant fraction of transportation fuel required in the future (Czernik et al., 2007). This can be achieved by use of hydrogen fuel cell vehicles or hydrogen powered combustion engines. Pyrolysis syngas can be used to produce transportation fuels that work with current infrastructures and technologies. Hydrogen and carbon monoxide, main components of the pyrolysis syngas, are the reactants necessary to produce liquid fuels (methanol, ethanol, gasoline, aviation fuel and diesel fuel) via Fischer-Tropsch (F-T) synthesis. F-T synthesis is regarded as the key technological component for converting syngas to transportation fuels and other liquid products (Wilhelm and others, 2001). F-T diesel is not bio-diesel. FT

diesel is a clear liquid that gives complete combustion with no particulate emissions and has a higher energy density that petroleum diesel and biodiesel. F-T diesel can be used in all existing diesel engines and can be mixed without a maximum mixture level with petroleum diesel (Wilhelm and others 2001). For instance Audi won the “24 Hours at LeMans” sports car race with F-T diesel. Currently, F-T fuels are produced from syngas originating from natural gas and coal. Biomass syngas can replace fossil fuels as the primary feedstock. 5. Pyrolysis vapors can produce non-energy products Pyrolysis vapors can also be used to produce a number of co-products such as wood preservative, meat browning, food flavorings, adhesives, or specific chemical compounds (Czernik, 2004). Liquid smoke, the chemical used to add smoke flavor to foods, is currently produced by pyrolysis of mesquite and other hardwoods. In local agricultural applications these vapors can be condensed and used as insecticides, herbicides, and fungicides (Steiner, 2007). The bio-oil by product from these processes can be refined as a source of chemical feedstocks to yield products such as acetic acid (vinegar).

6. Biomass pyrolysis can create valuable soil amendments One of the most exciting new benefits of biomass pyrolysis is its ability to produce valuable soil amendments in the form of charcoal (biochar). Biochar is currently used by Japan and in some parts of the world by indigenous tribes. Recent archeological exploration has found that indigenous peoples of the Amazon used charcoal to enrich their soil over 1,000 years ago. This was due to the discovery of a black colored soil in the Amazon basin of Brazil termed Terra Preta. It is believed that prior to the arrival of Europeans, the charcoal in these soils was added by native Amazonians to create arable farmland (Lehmann et al., 2006). Phosphorus (P) and calcium (Ca) are normally scarce in the very acidic Oxisols and Utisols that are predominant in this region. In contrast, Terra Preta soils contain higher levels of P and Ca with a higher, almost neutral pH (Glaser et al.,

Figure 2. Co-products from Biomass Pyrolysis ©Eprida 2008

1998). Another distinctive feature of Terra Preta soil is the high stability of its soil organic matter (SOM), and high cation exchange capacity (Sombroek, 2003), all factors that improve soil fertility.

The use of charcoal as a soil amendment is not limited to ancient civilizations such as the ones that created Terra Preta. New research has shown that biochar is more efficient at increasing soil fertility and nutrient retention than un-charred organic matter (Lehmann et al., 2006). Carbon enhanced SOM offers direct value through improved water infiltration, water holding capacity, structural stability, cation exchange capacity, soil biological activity and as a CO2 sink (Lehmann, 2007). Charcoal can also reduce fertilizer runoff and adsorb ammonium ions.

The use of biochar has recently been authorized for use as a soil amendment in Japan. Of all of the charcoal used in Japan in 1999, the highest percentage of use was in agricultural land as a soil amendment.

The second highest use was in the livestock industry where it used for animal feed and deodorization (Okimori et al.,2003). In the U.S. a system has been developed where biochar can be amended with ammonium bicarbonate producing a valuable carbon based fertilizer called ECOSS (Day and others, 2005). Other benefits of biochar include its ability to: adsorb soil-damaging pesticides and neutralize natural toxins in decomposing organic materials (Yelverton and others, 1996), and increase soil organic content (Blanco-Canqui et al., 2004). On farm trials in the U.S., a 20% increase in corn yield and a 520% in mycorrhizal populations (beneficial soil fungi that plants depend on) was observed where carbon based soil amendments were applied at 7-9 pounds per acre. In two years of trials at the Virginia Polytechnic Institute, a similar product achieved a 10% increase in sweet corn yield, a 30-pound per acre savings in nitrogen for Irish potatoes and a 22% increase in tomato yield (Morse, R and P. Stevens, 2006, 2007). Observations in the field also verified reduced need for irrigation where carbon based amendments were applied. Under proper conditions, scientists have also shown that when added to soil, biochar has the potential to increase soil carbon sequestration by as much as 400%. This is due to its beneficial effects on soil microorganisms, which convert soluble organic matter into stable organic compounds (Day, Reicosky, Nichols 2005).

In Hawaii, with electricity costs being some of the highest in the U.S., a company called EGEN is in negotiation to provide a pyrolysis plant for the island of Kauai. In this instance, the Kauai Utility has a program in place that allows generators of electricity to sell power on the grid or to a third party vendor with a 100% tax credit over a period of five years. In this case biochar will be used to generate electricity while also improving sustainability of agricultural cropland (http://www.egenindustries.com). In Australia, a similar concept is being developed for desalination of water (http://www.eprida.com). Recently, this technology has been scaled down so that small farms or farm cooperatives can own and operate a unit. This enables them to produce their own fuel and fertilizer.

7. Biomass pyrolysis can be used to sequester atmospheric carbon dioxide Charcoal is commonly used for heating and cooking, and in many developing countries is the only available fuel. In traditional methods of charcoal manufacturing all the valuable chemicals (tars, oils and smoke) and heat escape into the atmosphere. While biomass pyrolysis can provide fuel for heating and cooking, it is vastly different than the smoking kilns and barrels that are currently used throughout the world. Pyrolysis systems that produce biochar and energy do not produce pollution, contaminate water supplies, or create waste disposal problems. To ensure that systems producing biochar are clean and do not contribute to green house gas (GHG)

Figure 3: Eprida biochar from Pelletized Pine © Eprida, 2006

pollution, an organization called the International Biochar Initiative has formed and is setting standards for this product (http://www.biochar-international.org/home.html). Biomass pyrolysis can sequester up to 50% of the initial carbon (C) input and return it to the soil. The initial loss of C can be used for energy production and can offset fuel use (Figure 1.). This contrasts greatly with burning of biomass, which sequesters 3% of the initial C as charcoal, with the rest being emitted to the atmosphere, or biological decomposition which retains only 10 –20% of initial C after 5 – 10 years (Lehmann et al., 2006). Therefore, with its ability to capture and store carbon in the soil, biomass pyrolysis can deliver tradable carbon emission reductions (Lehmann, et.al. 2006). Controlled pyrolysis has recently been approved by the United Nations Framework Convention on Climate Change as a Clean Development Mechanism (CDM) for avoidance of methane production from biomass decay. (http://cdm.unfccc.int/UserManagement/FileStorage/CDMWF_AM_C7UWTIEMRJ05M3D02XWDW80JN989IP). In a CDM feasibility study on pyrolysis at an industrial tree plantation, it was calculated that annual processing of 368,000 tons of biomass would provide emissions reductions of 230,000 tons of CO2 per year and could provide jobs for approximately 2,600 people (Okimori, 2003). The latest figures published by the World Bank indicate that the carbon market grew in value to an estimated US$30 billion in 2006 (€23 billion), three times greater than the previous year. As of November 2007, over 850 carbon-offset projects have been registered worldwide with about seven percent of them in the area of biomass fuels (UNEP 2008 Yearbook). Conclusions Biomass fuels such as wood, herbaceous materials and agricultural by-products currently form the world’s third largest primary energy resource, behind coal and oil. At best, conventional biomass to energy is considered to be carbon neutral. Harvesting biomass to produce energy may not be sustainable because it can result in reduced soil productivity by depletion of carbon and nutrients. Biomass pyrolysis addresses this dilemma, because it can utilize waste products and about half of the original carbon can be returned to the soil (Lehmann, 2007). Utilizing biomass pyrolysis for the production of fuels also has significant advantages when compared to coal fuels because it can eliminate the need for post combustion scrubbing and can reduce nitric oxide (NOx) formation (Bisio et al., 1995). In fact such energy is actually CARBON NEGATIVE, because for each carbon molecule recycled back to the atmosphere, one is buried in the soil, so the net effect is to reduce atmospheric CO2! The deployment of biomass pyrolysis systems can create new local businesses, job opportunities and raise the income of people in rural communities (Okimori et al., 2003). Farming communities can benefit most from this system because the biochar co-product can reduce or eliminate purchased fertilizers while sequestering atmospheric CO2 (Glaser and others., 2002). This can create new profit centers for landowners by creating carbon credits and energy, which farmers can use or sell. This can decentralize fertilizer and energy distribution, making resources more available to farmers. It can reduce agricultural dependence on petroleum and natural gas based products by allowing regional energy production that is cost competitive with fossil fuels. Although biomass pyrolysis represents only a small portion of energy production worldwide it has the potential to generate energy at a lower cost than other energy systems. With its carbon negative footprint, biomass pyrolysis has the ability to do this in a way that can contribute to reduction in greenhouse gas emissions. Given that 1) soil organic carbon is one of the largest reservoirs in interaction with the atmosphere and 2) enhancing natural processes is thought to be the most cost-effective means of reducing atmospheric CO2; biomass pyrolysis provides a way forward toward overcoming the obstacles that are facing biofuels production today. In the words of USDA Soil Scientist, David Laird, we now have “A Win–Win–Win Scenario for Simultaneously Producing Bioenergy, Permanently Sequestering Carbon, while Improving Soil and Water Quality” (Laird, 2008).

References (A complete list of the references used in this paper is available at: http://www.carbonnegative.info) Antal, Michael (1982). Biomass Pyrolysis: A Review of the Literature Part 1- Carbohydrate Pyrolysis. K.W Boer, J.A. Duffie (ed.) Advances in Solar Energy: An annual review of Research and Development Vol 1 American Solar Energy Society, Inc. NY 61-111.

Bisio, Attilio and Sharon Boots (1995) Encyclopedia of Energy Technology and the Environment Vol 3 John Wiley & Sons, Inc, New York, NY 2281-2310.

Blanco-Canqui, H. and Rattan Lal (2004). Mechanisms of carbon sequestration in soil aggregates. Critical Reviews in Plant Sciences 23(6): 481-504.

Czernik, Stefan, Robert Evans, Richard French (2007). Hydrogen from biomass-production by steam reforming of biomass pyrolysis oil. Catalysis Today 129: 265-268.

Czernik, Stefan, A.V. Bridgewater (2004). Overview of Application of Biomass Fast Pyrolysis Oil. Energy Fuels 18: 590-598

Day, Danny, R.J. Evans, J.W. Lee, D. Reicosky (2005). Economical CO2, SOx, and NOx Capture from Fossil-fuel Utilization with Combined Renewable Hydrogen Production and Large-scale Carbon Sequestration. Energy 30: 2558-2579.

Day D, D Reicosky, K Nichols (2005). Internal report to U.S. Office of Management & Budget.

Glaser, Bruno, Ludwig Haumaier, Georg Guggenberger, Wolfgang Zech (1998). Stability of soil organic matter in Terra Preta soils. 16th World Congress of Soil Science, Montpellier, 20-26/08/1998, Proceedings on CD-ROM.

Glaser, Bruno, Johannes Lehmann, Christoph Steiner, Thomas Nehls, Muhammad Yousaf, and Wolfgang Zech (2002). Potential of Pyrolyzed Organic Matter in Soil Amelioration. 12th ISCO Conference: 421-427.

Iwasaki, W. (2003). A Consideration of the Economic Efficiency of Hydrogen Production from Biomass. International Journal of Hydrogen Energy 28: 939-944.

Laird, D.A. (2008) The Charcoal Vision: A Win–Win–Win Scenario for Simultaneously Producing Bioenergy, Permanently Sequestering Carbon, while Improving Soil and Water Quality. Agronomy Journal: 100(1) 178-181

Lehmann, Johannes, John Gaunt, Marco Rondon (2006). Bio-Char Sequestration in Terrestrial Ecosystems. Mititagtion and Adaptation Strategies for Global Change 11: 403-427.

Lehmann, Johannes (2007). Bio-energy in the black. Frontiers in Ecology and in the Environment 5: 381–387.

Magrini-Bair, K., S. Czernik, R. French, Y.O. Parent, E. Chornet, D.C. Dayton, C. Feik, R. Bain (2007). Fluidizable reforming catalyst development for conditioning biomass-derived syngas. Applied Catalysis A: General 318: 199-206.

Okimori, Y, Makoto Ogawa, F. Takahashi (2003). Potential of CO2 Emission Reductions by Carbonizing Biomass Waste from Industrial Tree Plantation in South Sumatra, Indonesia. Mitigation and Adaptation Strategies for Global Change 8: 261-280.

Raveendran, K. and Anuradda Ganesh (1996). Heating value of biomass and biomass pyrolysis products. Fuel 75: 1715-1720.

Samolada, M.C., W. Baldauf, and I. A. Vasalos (1998). Production of a bio-gasoline by upgrading biomass flash pyrolysis liquids via hydrogen processing and catalytic cracking. Fuel 77: 1667 – 1675.

Sombroek, W., M L Ruivo, P M Fearnside, B Glaser, and J Lehmann (2003). ‘Amazonian Dark Earths as carbon stores and sinks’, in J. Lehmann, D.C. Kern, B. Glaser and W.I. Woods eds., Amazonian Dark Earths: Origin, Properties, Management, Dordrecht, KluwerAcademic Publishers. 125–139

Steiner, Christoph, K.C. Das, M. Garcia, B Forster, and Wolfgang Zech (2007). Charcoal and smoke extract stimulate the soil microbial community in a highly weathered Xanthic Ferralsol. Pedobiologia In press.

UNDP: (2004). World Energy Assessment; ed. J. Goldemberg and T. B. Johansson, New York, NY, UNDP

UNEP Website: (2008) UNEP Launches Year Book 2008 at its 10th Special Session of the Governing Council/Global Ministerial Environment Forum in Monaco (Monaco, 20 February 2008 )

Wilhelm, D.J., D.R. Simbeck, A.D. Karp, R.L. Dickenson (2001). Syngas production for gas-to-liquids applications: technologies, issues and outlook. Fuel Processing Technology 71: 139-148.

Yaman, Serdar (2004). Pyrolysis of biomass to produce fuels and chemical feedstocks. Energy Conversion and Management 45: 651-671.

Yelverton, F.H, Jerome B Weber, G. Peedin, W. D. Smith (1996). Using activated charcoal to inactivate agricultural chemical spills. North Carolina Cooperative Extension Service Pub. AG-442 1-4.